Rehabilitation Assessment System for Stroke Patients Based on Fusion-Type Optoelectronic Plethysmography Device and Multi-Modality Fusion Model: Design and Validation

This study aimed to propose a portable and intelligent rehabilitation evaluation system for digital stroke-patient rehabilitation assessment. Specifically, the study designed and developed a fusion device capable of emitting red, green, and infrared lights simultaneously for photoplethysmography (PPG) acquisition. Leveraging the different penetration depths and tissue reflection characteristics of these light wavelengths, the device can provide richer and more comprehensive physiological information. Furthermore, a Multi-Channel Convolutional Neural Network-Long Short-Term Memory-Attention (MCNN-LSTM-Attention) evaluation model was developed. This model, constructed based on multiple convolutional channels, facilitates the feature extraction and fusion of collected multi-modality data. Additionally, it incorporated an attention mechanism module capable of dynamically adjusting the importance weights of input information, thereby enhancing the accuracy of rehabilitation assessment. To validate the effectiveness of the proposed system, sixteen volunteers were recruited for clinical data collection and validation, comprising eight stroke patients and eight healthy subjects. Experimental results demonstrated the system's promising performance metrics (accuracy: 0.9125, precision: 0.8980, recall: 0.8970, F1 score: 0.8949, and loss function: 0.1261). This rehabilitation evaluation system holds the potential for stroke diagnosis and identification, laying a solid foundation for wearable-based stroke risk assessment and stroke rehabilitation assistance.

MEMS Fingertip Strain Plethysmography for Cuffless Estimation of Blood Pressure

OBJECTIVE

To develop a cuffless method for estimating blood pressure (BP) from fingertip strain plethysmography (SPG) recordings.

METHODS

A custom-built micro-electromechanical systems (MEMS) strain sensor is employed to record heartbeat-induced vibrations at the fingertip. An XGboost regressor is then trained to relate SPG recordings to beat-to-beat systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP) values. For this purpose, each SPG segment in this setup is represented by a feature vector consisting of cardiac time interval, amplitude features, statistical properties, and demographic information of the subjects. In addition, a novel concept, coined geometric features, are introduced and incorporated into the feature space to further encode the dynamics in SPG recordings. The performance of the regressor is assessed on 32 healthy subjects through 5-fold cross-validation (5-CV) and leave-subject-out cross validation (LSOCV).

RESULTS

Mean absolute errors (MAEs) of 3.88 mmHg and 5.45 mmHg were achieved for DBP and SBP estimations, respectively, in the 5-CV setting. LSOCV yielded MAEs of 8.16 mmHg for DBP and 16.81 mmHg for SBP. Through feature importance analysis, 3 geometric and 26 integral-related features introduced in this work were identified as primary contributors to BP estimation. The method exhibited robustness against variations in blood pressure level (normal to critical) and body mass index (underweight to obese), with MAE ranges of [1.28, 4.28] mmHg and [2.64, 7.52] mmHg, respectively.

CONCLUSION

The findings suggest high potential for SPG-based BP estimation at the fingertip.

SIGNIFICANCE

This study presents a fundamental step towards the augmentation of optical sensors that are susceptible to dark skin tones.

A comparison between bioelectrical impedance analysis and air-displacement plethysmography in assessing fat-free mass in patients with motor neurone diseases: a cross-sectional study

AIM

To determine the validity of bioelectrical impedance analysis (BIA) in quantifying fat-free mass (FFM) compared to air-displacement plethysmography (ADP) in patients with a motor neurone disease (MND).

METHODS

FFM of 140 patients diagnosed with MND was determined by ADP using the BodPod (i.e. the gold standard), and by BIA using the whole-body Bodystat. FFM values were translated to predicted resting energy expenditure (REE); the actual REE was measured using indirect calorimetry, resulting in a metabolic index. Validity of the BIA compared to the ADP was assessed using Bland-Altman analysis and Pearson's r. To assess the clinical relevance of differences, we evaluated changes in metabolic index and in individualized protein demand.

RESULTS

Despite the high correlation between ADP and BIA (r = 0.93), averaged across patients, the assessed mean fat-free mass was 51.7 kg (± 0.9) using ADP and 54.2 kg (± 1.0) using BIA. Hence, BIA overestimated fat-free mass by 2.5 kg (95% CI 1.8-3.2, p < 0.001). Clinically, an increased metabolic index would be more often underdiagnosed in patients with MND using BIA (31.4% according to BIA versus 44.2% according to ADP, p = 0.048). A clinically relevant overestimation of ≥ 15 g in protein demand was observed for 4 (2.9%) patients using BIA.

CONCLUSIONS

BIA systematically overestimates FFM in patients with MND. Although the differences are limited with ADP, underscoring the utility of BIA for research, overestimation of fat-free mass may have consequences for clinical decision-making, especially when interest lies in determining the metabolic index.

Outcome measures in Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by severe intellectual disability, little to no expressive speech, visual and motor problems, emotional/behavioral challenges, and a tendency towards hyperphagia and weight gain. The characteristics of AS make it difficult to measure these children's functioning with standard clinical tests. Feasible outcome measures are needed to measure current functioning and change over time, in clinical practice and clinical trials.

AIM

Our first aim is to assess the feasibility of several functional tests. We target domains of neurocognitive functioning and physical growth using the following measurement methods: eye-tracking, functional Near-Infrared Spectroscopy (fNIRS), indirect calorimetry, bio-impedance analysis (BIA), and BOD POD (air-displacement plethysmography). Our second aim is to explore the results of the above measures, in order to better understand the AS phenotype.

METHODS

The study sample consisted of 28 children with AS aged 2-18 years. We defined an outcome measure as feasible when (1) at least 70% of participants successfully finished the measurement and (2) at least 60% of those participants had acceptable data quality. Adaptations to the test procedure and reasons for early termination were noted. Parents rated acceptability and importance and were invited to make recommendations to increase feasibility. The results of the measures were explored.

RESULTS

Outcome measures obtained with eye-tracking and BOD POD met the definition of feasibility, while fNIRS, indirect calorimetry, and BIA did not. The most important reasons for early termination of measurements were showing signs of protest, inability to sit still and poor/no calibration (eye-tracking specific). Post-calibration was often applied to obtain valid eye-tracking results. Parents rated the BOD POD als most acceptable and fNIRS as least acceptable for their child. All outcome measures were rated to be important. Exploratory results indicated longer reaction times to high salient visual stimuli (eye-tracking) as well as high body fat percentage (BOD POD).

CONCLUSIONS

Eye-tracking and BOD POD are feasible measurement methods for children with AS. Eye-tracking was successfully used to assess visual orienting functions in the current study and (with some practical adaptations) can potentially be used to assess other outcomes as well. BOD POD was successfully used to examine body composition.

TRIAL REGISTRATION

Registered d.d. 23-04-2020 under number 'NL8550' in the Dutch Trial Register: https://onderzoekmetmensen.nl/en/trial/23075.

Lung Function Evaluated By Structured Light Plethysmography in Children After Lung Surgery: A Preliminary Analysis

Background: Structured light plethysmography (SLP) is a novel light-based method that captures chest wall movements to evaluate tidal breathing. Methods: Thirty-two children who underwent lung surgery were enrolled. Their clinical history was collected along with spirometry and SLP. Results: Median age of surgery was 9 months (interquartile range 4-30). Most frequent diagnosis was congenital pulmonary airway malformation (14/32), then pulmonary sequestration (9/32), tumor (5/32), and bronchogenic cyst (4/32). The most frequent surgical approach was lobectomy (59%), segmentectomy (38%), and complete resection (3%). More than 80% had surgery when younger than 3 years of age. Eight patients had short-term complications (pleural effusion was the most frequent), while long-term effects were reported in 15 patients (19% recurrent cough, 13% thoracic deformities, 13% airway infections, 9% wheezing, 6% reduced exercise tolerance, and 3% columnar deformities). Spirometry was normal in 9/22 patients. Nine patients had a restrictive pattern, while 4 showed a mild bronco-reactivity. Ten patients did not perform spirometry because of young age. SLP revealed the presence of obstructive pattern in 10% of patients (IE50 > 1.88) and showed a significant difference between the two hemithorax in 29% of patients. Discussion: SLP may be a new method to evaluate lung function, without collaboration and radiation exposure, in children who underwent lung resection, also in preschool age.

Utilizing venous occlusion plethysmography to assess vascular effects: A study with buloxibutid, an angiotensin II type 2 receptor agonist

Buloxibutid (also known as C21) is a potent and selective angiotensin II type 2 receptor (AT2R) agonist, in development for oral treatment of fibrotic lung disease. This phase I, open-label, pharmacodynamic study investigated vascular effects of buloxibutid in five healthy male volunteers. Subjects were administered intra-arterial infusions of buloxibutid for 5 min in ascending doses of 3, 10, 30, 100, and 200 μg/min, infused sequentially in the forearm. Infusions of sodium nitroprusside (SNP) solution in doses of 0.8-3.2 μg/min were administered as a positive control. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Safety and tolerability of intra-arterial administrations of buloxibutid were evaluated. Following infusion of buloxibutid in doses of 3-200 μg/min, the range of increase in FBF was 27.8%, 17.2%, 37.0%, 28.5%, and 60.5%, compared to the respective baseline. The largest increase was observed in the highest dose group. Infusions of SNP as a positive control, increased FBF 230-320% compared to baseline. Three adverse events (AEs) of mild intensity, not related to buloxibutid or SNP, were reported for two subjects. Two of these AEs were related to study procedures. There were no clinically relevant changes in arterial blood pressure during the study period. Intra-arterial infusion of buloxibutid in low, ascending doses increased FBF, indicating that buloxibutid may be effective in conditions associated with endothelial dysfunction. Venous occlusion plethysmography was found to be a useful method to explore pharmacodynamic vascular effects of novel AT2R agonists, while avoiding systemic adverse effects.

Efficacy of Marker-Based Motion Capture for Respiratory Cycle Measurement: A Comparison with Spirometry

Respiratory rate monitoring is fundamental in clinical settings, and the accuracy of measurement methods is critical. This study aimed to develop and validate methods for assessing respiratory rate and the duration leof respiratory cycle phases in different body positions using optoelectronic plethysmography (OEP) based on a motion capture video system. Two analysis methods, the summation method and the triangle method were developed. The study focused on determining the optimal number of markers while achieving accuracy in respiratory parameter measurements. The results showed that most analysis methods showed a difference of ≤0.5 breaths per minute, with R2 ≥ 0.94 (p < 0.001) compared to spirometry. The best OEP methods for respiratory rate were the abdominal triangles and the sum of abdominal markers in all body positions. The study explored inspiratory and expiratory durations. The research found that 5-9 markers were sufficient to accurately determine respiratory time components in all body positions, reducing the marker requirements compared to previous studies. This interchangeability of OEP methods with standard spirometry demonstrates the potential of non-invasive methods for the simultaneous assessment of body segment movements, center of pressure dynamics, and respiratory movements. Future research is required to improve the clinical applicability of these methods.

Air Displacement Plethysmography is an Accurate and Feasible Noninvasive Measure of Fat-Free Mass in Children With Intestinal Failure

BACKGROUND

The nutritional status of children with intestinal failure (IF) can be difficult to determine using body weight and currently available anthropometric techniques. Air displacement plethysmography (ADP) is a noninvasive measure of whole-body composition that measures body mass and volume, with a calculation of percent body fat (%BF) and fat-free mass (FFM) that may be useful during the provision of specialized nutrition.

OBJECTIVES

To evaluate the validity and feasibility of measuring body composition in children with IF using ADP compared with deuterium dilution (DD), as well as secondarily with other measures of body composition, namely bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA), and four-site skinfold anthropometry.

METHODS

We conducted a prospective cohort study of 18 children recruited through the Center for Advanced Intestinal Rehabilitation at Boston Children's Hospital. Patients 2-17 years of age with IF dependent on parenteral nutrition (PN) for more than 90 days were included. Spearman rank correlation and Bland-Altman limits of agreement (LOA) analysis were used to compare ADP to 4 alternative measures of body composition.

RESULTS

Eighteen children with IF, median age 7.1 [interquartile range (IQR) 5.4-9.3] years, 9 female (50%), and median residual bowel length 31 (IQR 22-85) cm were enrolled. Median PN energy intake was 46 (IQR 39-49) kcal/kg/day. Incomplete bladder emptying lead to invalid measures of DD in 4 subjects. Spearman correlation coefficients for %BF were low to moderate between ADP and DD ( r = 0.29), DXA ( r = 0.62), BIA ( r = 0.50), and skinfold ( r = 0.40). Correlations for FFM were high between ADP and these other measures (range 0.95-0.98). Comparing ADP with DD and skinfold measures, Bland-Altman analysis showed small mean bias (-1.9 and +1.5 kg) and acceptable 95% LOA ranges (10.7 and 22.9 kg), respectively, with larger bias (-10.7 and -7.7 kg) and LOA ranges (38.7 and 45.2 kg) compared to DXA and BIA. %BF by ADP and skinfold thickness were moderately correlated ( r = 0.43) with low bias (-0.2%) but very wide LOA (25.7%).

CONCLUSIONS

Body composition via ADP is feasible and valid in children with IF as a measure of FFM but appears less suitable for the measurement of %BF. The technique holds promise as a noninvasive measure of body composition to assess the efficacy of nutritional, medical, and surgical interventions.

Development of a predictive model of body fat mass for newborns and infants

OBJECTIVES

The aim of this study is to develop predictive body fat mass models, one for newborns and one for infants, using air displacement plethysmography as a reference method.

METHODS

The study was carried out with 125 newborns (1-5 d of age) and 71 infants (≥3-6 mo). The stepwise method was used to estimate the final model from the predictors of sex, weight, length, triceps skinfold, waist circumference, mean arm circumference, and gestational age. The quality of the models was evaluated by the determination coefficient, variance inflation factor, and residual analysis. The paired t test and Bland-Altman plot were used to assess the agreement between observed and estimated values.

RESULTS

The final model for newborns was - 0.76638 + 0.2512 * weight (kg) + 0.0620 * PCT (mm) + 0.0754 * gender (R² = 70%) and the final model for infants: -2.22748 + 0.4928 * weight (kg) + 0.0737 * TSF (mm) + 0.2647 * gender (R² = 84%).

CONCLUSIONS

This work determined equations to estimate the BFM of term newborns and infants. The models can be used in clinical practice, especially in health units without access to technologies for measuring body composition, adding important information for nutritional monitoring.

Evaluation of bioelectrical impedance analysis in measuring body fat in 6-to-12-year-old boys compared with air displacement plethysmography

Air displacement plethysmography (ADP) has been considered as the 'standard' method to determine body fat in children due to superior validity and reliability compared with bioelectrical impedance analysis (BIA). However, ADP and BIA are often used interchangeably despite few studies comparing measures of percentage body fat by ADP (%FMADP) with BIA (%FMBIA) in children with and without obesity. The objective of this study was to measure concurrent validity and reliability of %FMADP and %FMBIA in 6-to-12-year-old boys with and without obesity. Seventy-one boys (twenty-five with obesity) underwent body composition assessment. Ten boys participated in intra-day reliability analysis. %FMADP was estimated by Bodpod using sex- and age-specific equations of body density. %FMBIA was estimated by a multi-frequency, hand-to-foot device using child-specific equations based on impedance. Validity was assessed by t tests, correlation coefficients and limits of agreement (LoA); and reliability by technical error of measurement (TEM) and intraclass correlation coefficients (ICC). Compared with %FMADP, %FMBIA was significantly underestimated in the cohort (-3·4 ± 5·6 %; effect size = 0·42) and in both boys with obesity (-5·2 ± 5·5 %; ES = 0·90) and without obesity (-2·4 ± 5·5 %; ES = 0·52). A strong, significant positive correlation was found between %FMADP and %FMBIA (r = 0·80). Across the cohort, LoA were 22·3 %, and no proportional bias was detected. For reliability, TEM were 0·65 % and 0·55 %, and ICC were 0·93 and 0·95 for %FMBIA and %FMADP, respectively. Whilst both %FMADP and %FMBIA are highly reliable methods, considerable differences indicated that the devices cannot be used interchangeably in boys age 6-to-12 years.

Challenges in body composition assessment using air-displacement plethysmography by BOD POD in pediatric and young adult patients

BACKGROUND & AIMS

Air-Displacement-Plethysmography (ADP) by BOD POD is widely used for body fat assessment in children. Although validated in healthy subjects, studies about use in pediatric patients are lacking. We evaluated user experience and usability of ADP measurements with the BOD POD system in healthy children and pediatric and young adult patients.

METHODS

Using the experiences of seven cohort studies, which included healthy children and patients aged 2-22 years, we retrospectively evaluated the user experience with the User Experience Questionnaire (UEQ) (n = 13) and interviews (n = 7). Technical performance was studied using the quality control data collected by the ADP-system.

RESULTS

From 2016 to 2022, 1606 measurements were scheduled. BOD POD was mostly rated 'user-friendly', with a generally neutral evaluation on all scales of the UEQ. However, questionable reliability and validity of the results were frequently (86%) reported. We found a high technical failure-rate of the device, predominantly in stability (17%) and accuracy of the measurement (12%), especially in the 'pediatric option' for children aged <6 years. Measurement failure-rate was 38%, mostly due to subject's fear or device failure, especially in young and lean children, and in children with physical and/or intellectual disabilities.

CONCLUSION

We conclude that ADP by BOD POD in children and young adults is non-invasive and user-friendly. However, in specific pediatric populations, BOD POD has several limitations and high (technical) failure-rates, especially in young children with aberrant body composition. We recommend caution when interpreting body composition results of pediatric patients as assessed with BOD POD using the current default settings.

Breathing Chest Wall Kinematics Assessment through a Single Digital Camera: A Feasibility Study

The identification of respiratory patterns based on the movement of the chest wall can assist in monitoring an individual's health status, particularly those with neuromuscular disorders, such as hemiplegia and Duchenne muscular dystrophy. Thoraco-abdominal asynchrony (TAA) refers to the lack of coordination between the rib cage and abdominal movements, characterized by a time delay in their expansion. Motion capture systems, like optoelectronic plethysmography (OEP), are commonly employed to assess these asynchronous movements. However, alternative technologies able to capture chest wall movements without physical contact, such as RGB digital cameras and time-of-flight digital cameras, can also be utilized due to their accessibility, affordability, and non-invasive nature. This study explores the possibility of using a single RGB digital camera to record the kinematics of the thoracic and abdominal regions by placing four non-reflective markers on the torso. In order to choose the positions of these markers, we previously investigated the movements of 89 chest wall landmarks using OEP. Laboratory tests and volunteer experiments were conducted to assess the viability of the proposed system in capturing the kinematics of the chest wall and estimating various time-related respiratory parameters (i.e., fR, Ti, Te, and Ttot) as well as TAA indexes. The results demonstrate a high level of agreement between the detected chest wall kinematics and the reference data. Furthermore, the system shows promising potential in estimating time-related respiratory parameters and identifying phase shifts indicative of TAA, thus suggesting its feasibility in detecting abnormal chest wall movements without physical contact with a single RGB camera.

Development and validation of anthropometric-based fat-mass prediction equations using air displacement plethysmography in Mexican infants

BACKGROUND/OBJECTIVES

Fat-mass (FM) assessment since birth using valid methodologies is crucial since excessive adiposity represents a risk factor for adverse metabolic outcomes.

AIM

To develop infant FM prediction equations using anthropometry and validate them against air-displacement plethysmography (ADP).

SUBJECTS/METHODS

Clinical, anthropometric (weight, length, body-mass index -BMI-, circumferences, and skinfolds), and FM (ADP) data were collected from healthy-term infants at 1 (n = 133), 3 (n = 105), and 6 (n = 101) months enrolled in the OBESO perinatal cohort (Mexico City). FM prediction models were developed in 3 steps: 1) Variable Selection (LASSO regression), 2) Model behavior evaluation (12-fold cross-validation, using Theil-Sen regressions), and 3) Final model evaluation (Bland-Altman plots, Deming regression).

RESULTS

Relevant variables in the FM prediction models included BMI, circumferences (waist, thigh, and calf), and skinfolds (waist, triceps, subscapular, thigh, and calf). The R2 of each model was 1 M: 0.54, 3 M: 0.69, 6 M: 0.63. Predicted FM showed high correlation values (r ≥ 0.73, p < 0.001) with FM measured with ADP. There were no significant differences between predicted vs measured FM (1 M: 0.62 vs 0.6; 3 M: 1.2 vs 1.35; 6 M: 1.65 vs 1.76 kg; p > 0.05). Bias were: 1 M -0.021 (95%CI: -0.050 to 0.008), 3 M: 0.014 (95%CI: 0.090-0.195), 6 M: 0.108 (95%CI: 0.046-0.169).

CONCLUSION

Anthropometry-based prediction equations are inexpensive and represent a more accessible method to estimate body composition. The proposed equations are useful for evaluating FM in Mexican infants.

Bridging vascular physiology to vascular medicine: an integrative laboratory class

Vascular diseases of the legs are highly prevalent and constitute an important part of medical curricula. The understanding of these diseases relies on strongly interwoven aspects of vascular physiology and vascular medicine. We aimed to connect these within a horizontally integrated laboratory class on vascular physiology of the leg that was designed in cooperation between the departments of physiology and vascular surgery. Conceptually, we applied examination techniques of vascular medicine to visualize physiological parameters that are altered by the most frequent diseases. This facilitates integrative discussions on malfunctions, trains diagnostic skills, and bridges to vascular medicine. In four experiments, we use oscillometry and impedance venous occlusion plethysmography to address key aspects of the arterial and venous system of the legs: 1) arterial pulse wave, 2) arterial systolic blood pressure, 3) venous capacitance and venous outflow, and 4) reactive hyperemia. After the experiments, physiological vascular function, the associated diseases, their impact on the recorded parameters, and diagnostic options are discussed. To allow reproduction, we describe the course structure and the experimental setup in detail. We present the experimental data of a cohort of medical students and document learning success and student satisfaction. All experiments were feasible and provided robust data on physiologically and clinically relevant vascular functions. The activity was perceived positively by the students and led to a substantial improvement of knowledge. With this work, we offer a template for reproduction or variation of a proven concept of horizontally integrated teaching of vascular physiology of the leg.NEW & NOTEWORTHY This article presents an integrative laboratory class on vascular physiology bridging to vascular medicine. The four experiments rely on oscillometry and venous occlusion plethysmography. We describe in detail this new class regarding structure, experimental setup, and experimental procedure, and we give insight into the applied materials. Moreover, we present the experimental data of 74 students and a quantitative evaluation of the students' learning success and acceptance.

Depth-Based Measurement of Respiratory Volumes: A Review

Depth-based plethysmography (DPG) for the measurement of respiratory parameters is a mobile and cost-effective alternative to spirometry and body plethysmography. In addition, natural breathing can be measured without a mouthpiece, and breathing mechanics can be visualized. This paper aims at showing further improvements for DPG by analyzing recent developments regarding the individual components of a DPG measurement. Starting from the advantages and application scenarios, measurement scenarios and recording devices, selection algorithms and location of a region of interest (ROI) on the upper body, signal processing steps, models for error minimization with a reference measurement device, and final evaluation procedures are presented and discussed. It is shown that ROI selection has an impact on signal quality. Adaptive methods and dynamic referencing of body points to select the ROI can allow more accurate placement and thus lead to better signal quality. Multiple different ROIs can be used to assess breathing mechanics and distinguish patient groups. Signal acquisition can be performed quickly using arithmetic calculations and is not inferior to complex 3D reconstruction algorithms. It is shown that linear models provide a good approximation of the signal. However, further dependencies, such as personal characteristics, may lead to non-linear models in the future. Finally, it is pointed out to focus developments with respect to single-camera systems and to focus on independence from an individual calibration in the evaluation.

The influence of receiving real-time visual feedback on breathing during treadmill running to exhaustion

Breathing plays a vital role in everyday life, and specifically during exercise it provides working muscles with the oxygen necessary for optimal performance. Respiratory inductance plethysmography (RIP) monitors breathing through elastic belts around the chest and abdomen, with efficient breathing defined by synchronous chest and abdomen movement. This study examined if providing runners with visual feedback through RIP could increase breathing efficiency and thereby time to exhaustion. Thirteen recreational runners (8F, 5M) ran to exhaustion on an inclined treadmill on two days, with visual feedback provided on one randomly chosen day. Phase angle was calculated as a measure of thoraco-abdominal coordination. Time to exhaustion was not significantly increased when visual feedback was provided (p = 1). Phase angle was not significantly predicted by visual feedback (p = 0.667). Six participants improved phase angle when visual feedback was provided, four of whom increased time to exhaustion. Four participants improved phase angle by 9° or more, three of whom increased time to exhaustion. Participants who improved phase angle with visual feedback highlight that improving phase angle could increase time to exhaustion. Greater familiarization with breathing techniques and visual feedback and a different paradigm to induce running fatigue are needed to support future studies of breathing in runners.

Unsupervised study of plethysmography signals through DTW clustering

The study of plethysmography time series is crucial to better understand the breathing behavior of mice, in particular the influence of neurotoxins on the respiratory system. Current approaches rely on a few respiratory descriptors computed on individual breathing cycles that fail to account for the variety of breathing habits and their evolution with time. In this paper we introduce a new procedure for the automatic analysis of plethysmography signals. Our method relies on a new and robust segmentation of respiratory cycles and a DTW-based clustering algorithm to extract the most typical respiratory cycles (called reference sequences). We can then create a symbolic representation of any new recording by matching respiratory cycles to their closest reference sequence. This new representation is a visual and quantitative tool to assess the breathing behavior of mice and its evolution with time. Our method is applied to plethysmography signals collected on mice with two different genotypes and exposed to a neurotoxin. Clinical relevance This article proposes a novel approach to study plethysmography data. Our algorithm is able to accurately extract clinically meaningful respiratory cycles and the associated ventilation patterns descriptors such as tidal volume and inhalation/exhalation duration. In addition, thanks to the associated symbolic representation of signals, the temporal evolution of respiration is easily quantified. This opens a new research path to study the often slowly evolving and subtle influence of neurotoxins on the respiratory system.

Respiratory Inductance Plethysmography to Assess Fatigability during Repetitive Work

Cumulative fatigue during repetitive work is associated with occupational risk and productivity reduction. Usually, subjective measures or muscle activity are used for a cumulative evaluation; however, Industry 4.0 wearables allow overcoming the challenges observed in those methods. Thus, the aim of this study is to analyze alterations in respiratory inductance plethysmography (RIP) to measure the asynchrony between thorax and abdomen walls during repetitive work and its relationship with local fatigue. A total of 22 healthy participants (age: 27.0 ± 8.3 yrs; height: 1.72 ± 0.09 m; mass: 63.4 ± 12.9 kg) were recruited to perform a task that includes grabbing, moving, and placing a box in an upper and lower shelf. This task was repeated for 10 min in three trials with a fatigue protocol between them. Significant main effects were found from Baseline trial to the Fatigue trials (p < 0.001) for both RIP correlation and phase synchrony. Similar results were found for the activation amplitude of agonist muscle (p < 0.001), and to the muscle acting mainly as a joint stabilizer (p < 0.001). The latter showed a significant effect in predicting both RIP correlation and phase synchronization. Both RIP correlation and phase synchronization can be used for an overall fatigue assessment during repetitive work.

The impact of subject positioning on body composition assessments by air displacement plethysmography evaluated in a heterogeneous sample

Introduction

This study sought to evaluate the impact of subject positioning on body composition assessments by air displacement plethysmography using the BOD POD®.

Methods

Eighty-two adults (42 men and 40 women), aged 26.1 ± 8.4 y (mean ± standard deviation), body mass index = 23.6 ± 4.8 kg/m2, were assessed by repeated measurements in two different positions: relaxed (legs apart, back away from the rear) and compact (legs together, arms near the body, back touching the rear). We relied on Bland-Altman analysis to quantify the agreement between results recorded in the two positions. Using body surface charts, we tested the hypothesis that posture-induced variability stems from differences in exposed skin area.

Results

Switching from compact to relaxed position resulted in a bias of -197 mL for body volume, -1.53% for percent body fat, and 1.085 kg for fat-free mass. The body surface area in contact with air was larger in relaxed position by 3632 ± 522 cm2. When body volume was expressed in terms of the actual area of exposed skin in the compact position, the percent body fat bias became 0.08%, with a 95% confidence interval of (-0.14, 0.29)%.

Conclusions

Subject posture is a source of significant variability in air displacement plethysmography. The disagreement between results obtained in different positions can be eliminated by adjusting the surface area artifact, suggesting that subject positioning in the BOD POD® should be controlled to avoid changes in the amount of air maintained under isothermal conditions by the body.

Comparison of Respiratory Calibration Methods for the Estimation of Lung Volume in Children With and Without Neuromotor Disorders

PURPOSE

The primary purpose of this study was to validate common respiratory calibration methods for estimating lung volume in children.

METHOD

Respiratory kinematic data were collected via inductive plethysmography from 81 typically developing children and nine children with neuromotor disorders. Correction factors for the rib cage and abdomen were calculated using three different methods: (a) least squares method with both rib cage and abdomen corrections (LsqRC/AB), (b) least squares method with rib cage correction only (LsqRC), and (c) a standard 2:1 rib-cage-to-abdomen ratio (Banzett). Correction factors for the LsqRC/AB and LsqRC methods were calculated with and without the use of the speech-like breathing calibration task. Lung volume estimation errors were calculated by comparing the estimated lung volumes based on the correction factors and the actual lung volumes acquired from a spirometer, normalized to each participant's vital capacity.

RESULTS

For typically developing children, the LsqRC/AB method resulted in significantly smaller lung volume estimation errors compared with other methods. Lung volume estimation errors decreased as age increased for each method. For the children with neuromotor disorders, the LsqRC/AB and LsqRC methods resulted in significantly smaller lung volume estimation errors than the Banzett method but were not significantly different from one another. There were no significant differences in lung volume estimation errors for the LsqRC/AB and LsqRC methods when the correction factors were calculated with and without the speech-like breathing calibration task.

CONCLUSION

The LsqRC/AB method exclusively utilizing the rest breathing calibration task is the most accurate and efficient respiratory calibration method for use with children with and without neuromotor disorders at this time.

Effect of pursed-lip breathing and forward trunk lean positions on regional chest wall volume and ventilatory pattern in older adults: An observational study

ABSTRACT

Pursed-lip breathing (PLB) and forward trunk lean posture (FTLP) are commonly used to relieve dyspnea and improve ventilation in a rehabilitation program. However, their effect on chest wall volumes and movements in older adults without chronic obstructive pulmonary disease has never been investigated. This observational study aimed to identify the effect of combined PLB and FTLP on total and regional chest wall volumes, ventilatory pattern, and thoracoabdominal movement using in older adults. It was hypothesized that the combined PLB with FTLP would result in the highest chest wall volumes among the experimental tasks. Twenty older adults performed 2 breathing patterns of quiet breathing (QB) and PLB during a seated upright (UP) position and FTLP. An optoelectronic plethysmography system was used to capture the chest wall movements during the 4 experimental tasks. Tidal volume (VT) was separated into pulmonary ribcage, abdominal ribcage, and abdomen volume. The changes in anterior-posterior (AP) and medial-lateral (ML) chest wall diameters at 3 levels were measured and used to identify chest wall mechanics to improve chest wall volumes. The PLB significantly improved ventilation and chest wall volumes than the QB (P < .05). VT of pulmonary ribcage, VT of abdominal ribcage, and VT were significantly higher during the PLB + UP (P < .05) and during the PLB + FTLP (P < .01) as compared to those of QB performed in similar body positions. However, there was no significant in total and regional lung volumes between the PLB + UP and the PLB + FTLP. The AP diameter changes at the angle of Louis and xiphoid levels were greater during the PLB + UP than the QB + UP and the QB + FTLP (P < .01). The AP diameter changes at the umbilical level and the ML diameter changes at the xiphoid level were significantly larger during the PLB + FTLP than the QB + FTLP and the QB + UP (P < .05). The ML diameter changes at the umbilical level were significantly greater during the PLB + FTLP than the QB + UP (P < .05). However, no significant difference in the relative regional chest wall volumes and phase angle among the experimental tasks (P > .05). In conclusion, a combined PLB performed in an FTLP or UP sitting could be used as a strategy to improve chest wall volumes and ventilation in older adults.

Validation of a Novel Compact System for the Measurement of Lung Volumes

BACKGROUND

Current techniques for measuring absolute lung volumes rely on bulky and expensive equipment and are complicated to use for the operator and the patient. A novel method for measurement of absolute lung volumes, the MiniBox method, is presented.

RESEARCH QUESTION

Across a population of patients and healthy participants, do values for total lung capacity (TLC) determined by the novel compact device (MiniBox, PulmOne Advanced Medical Devices, Ltd.) compare favorably with measurements determined by traditional whole body plethysmography?

STUDY DESIGN AND METHODS

A total of 266 participants (130 men) and respiratory patients were recruited from five global centers (three in Europe and two in the United States). The study population comprised individuals with obstructive (n = 197) and restrictive (n = 33) disorders as well as healthy participants (n = 36). TLC measured by conventional plethysmography (TLCPleth) was compared with TLC measured by the MiniBox (TLCMB).

RESULTS

TLC values ranged between 2.7 and 10.9 L. The normalized root mean square difference (NSD) between TLCPleth and TLCMB was 7.0% in healthy participants. In obstructed patients, the NSD was 7.9% in mild obstruction and 9.1% in severe obstruction. In restricted patients, the NSD was 7.8% in mild restriction and 13.9% in moderate and severe restriction. No significant differences were found between TLC values obtained by the two measurement techniques. Also no significant differences were found in results obtained among the five centers.

INTERPRETATION

TLC as measured by the novel MiniBox system is not significantly different from TLC measured by conventional whole body plethysmography, thus validating the MiniBox method as a reliable method to measure absolute lung volumes.

Machine learning for automatic identification of thoracoabdominal asynchrony in children

BACKGROUND

The current methods for assessment of thoracoabdominal asynchrony (TAA) require offline analysis on the part of physicians (respiratory inductance plethysmography (RIP)) or require experts for interpretation of the data (sleep apnea detection).

METHODS

To assess synchrony between the thorax and abdomen, the movements of the two compartments during quiet breathing were measured using pneuRIP. Fifty-one recordings were obtained: 20 were used to train a machine-learning (ML) model with elastic-net regularization, and 31 were used to test the model's performance. Two feature sets were explored: (1) phase difference (ɸ) between the thoracic and abdominal signals and (2) inverse cumulative percentage (ICP), which is an alternate measure of data distribution. To compute accuracy of training, the model outcomes were compared with five experts' assessments.

RESULTS

Accuracies of 61.3% and 90.3% were obtained using ɸ and ICP features, respectively. The inter-rater reliability (i.r.r.) of the assessments of experts was 0.402 and 0.684 when they used ɸ and ICP to identify TAA, respectively.

CONCLUSIONS

With this pilot study, we show the efficacy of the ICP feature and ML in developing an accurate automated approach to identifying TAA that reduces time and effort for diagnosis. ICP also helped improve consensus among experts.

IMPACT

Our article presents an automated approach to identifying thoracic abdominal asynchrony using machine learning and the pneuRIP device. It also shows how a modified statistical measure of cumulative frequency can be used to visualize the progression of the pulmonary functionality along time. The pulmonary testing method we developed gives patients and doctors a noninvasive and easy to administer and diagnose approach. It can be administered remotely, and alerts can be transmitted to the physician. Further, the test can also be used to monitor and assess pulmonary function continuously for prolonged periods, if needed.

Agreement between B-Mode Ultrasound and Air Displacement Plethysmography in Preprofessional Ballet Dancers

PURPOSE

This study aimed to assess the agreement between B-mode ultrasound and air displacement plethysmography (ADP) body composition results in preprofessional ballet dancers.

METHODS

Male (n = 21, Mage = 17.2 ± 1.7 yr, MBMI = 20.5 ± 2.0 kg·m-2) and female (n = 27, Mage = 16.1 ± 1.4 yr, MBMI = 18.3 ± 1.3 kg·m-2) dancers were assessed by ADP and ultrasound to determine body fat percentage (%BF), fat mass (FM), and fat-free mass (FFM). Pearson's correlations were used to assess agreement, and paired t-tests were used to determine differences between devices (α = 0.05). Ultrasound validity was assessed using SEE and total error. Bland-Altman plots were used to identify 95% limits of agreement.

RESULTS

Agreement was high for %BF (females, r = 0.94; males, r = 0.77), FM (females, r = 0.94; males, r = 0.73), and FFM (females, r = 0.95; males, r = 0.99). However, ultrasound overestimated %BF and FM and underestimated FFM (P < 0.05) compared with ADP in females only. In addition, there were stronger agreement and lower error for FFM compared with both %BF and FM regardless of sex.

CONCLUSION

There is strong agreement between ultrasound and ADP in this population. Although ultrasound may be a useful field tool to assess body composition, future research is needed to refine %BF equations in this population to reduce calculation errors.

A Field-based Three-Compartment Model Derived from Ultrasonography and Bioimpedance for Estimating Body Composition Changes

PURPOSE

The purpose of this study was to assess the agreement between a field-based three-compartment (3CFIELD) model and a laboratory-based three-compartment (3CLAB) model for tracking body composition changes over time.

METHODS

Resistance-trained males completed a supervised nutrition and resistance training intervention. Before and after the intervention, assessments were performed via air displacement plethysmography (ADP), bioimpedance spectroscopy (BIS), portable ultrasonography (US), and bioelectrical impedance analysis (BIA). ADP body density and BIS body water were used within the reference 3CLAB model, whereas US-derived body density and BIA body water were used within the 3CFIELD model. Two-compartment model body composition estimates provided by US and BIA were also examined. Changes in fat-free mass and fat mass were analyzed using repeated-measures ANOVA, equivalence testing, Bland-Altman analysis, linear regression, and related validity analyses.

RESULTS

Significant increases in fat-free mass (3CLAB, 4.0 ± 4.5 kg; 3CFIELD, 3.9 ± 4.2 kg; US, 3.2 ± 4.3 kg; BIA, 3.9 ± 4.2 kg) and fat mass (3CLAB, 1.3 ± 2.2 kg; 3CFIELD, 1.4 ± 2.2 kg; US, 2.1 ± 2.6 kg; BIA, 1.4 ± 2.9 kg) were detected by all methods. However, only the 3CFIELD model demonstrated equivalence with the 3CLAB model. In addition, the 3CFIELD model exhibited superior performance to US and BIA individually, as indicated by the total error (3CFIELD, 1.0 kg; US, 1.8 kg; BIA, 1.6 kg), 95% limits of agreement (3CFIELD, ±2.1 kg; US, ±3.3 kg; BIA, ±3.1 kg), correlation coefficients (3CFIELD, 0.79-0.82; US, 0.49-0.55; BIA, 0.61-0.72), and additional metrics.

CONCLUSIONS

The present study demonstrated the potential usefulness of a 3CFIELD model incorporating US and BIA data for tracking body composition changes over time, as well as its superiority to US or BIA individually. As such, this accessible multicompartment model may be suitable for implementation in field or limited-resource settings.

Collateral Circulation Testing of the Hand- Is it Relevant Now? A Narrative Review

Testing for collateral circulation of the hand before any radial artery procedure has been a subject of many controversies. Neither the Allen's test (AT) nor the plethysmography based Barbeau test, adequately and reliably test for collateral circulation. With growing interest in radial approaches for vascular procedures, its common use for arterial monitoring and blood gas sampling, there has been a growing interest in the relevance of assessing collateral hand circulation. Multiple studies now refute the utility of collateral testing, yet it continues to be propagated as an essential triaging assessment tool by educators. Allen's, or modified Allen tests (MAT) are operator dependent and often subjected to observational bias. Barbeau test is more objective, however, it fails to show added benefit in assessing pre-procedural patency. Despite studies questioning the validity of collateral circulation assessment, these tests continue to preclude radial approach. There is no standardization for being considered an abnormal test across literature and the significance of an abnormal test translating into a clinical outcome has not been investigated in prior studies. This may be attributed to the robust vascular supply of the hand, connections at the digital circulation level and vessel recruitment in an event of occlusion. We reviewed this topic extensively and make an argument that non-invasive collateral testing should be abandoned as a triage tool for radial artery procedures such as arterial punctures, arterial monitoring, and transradial vascular procedures.

Automatic unsupervised respiratory analysis of infant respiratory inductance plethysmography signals

Infants are at risk for potentially life-threatening postoperative apnea (POA). We developed an Automated Unsupervised Respiratory Event Analysis (AUREA) to classify breathing patterns obtained with dual belt respiratory inductance plethysmography and a reference using Expectation Maximization (EM). This work describes AUREA and evaluates its performance. AUREA computes six metrics and inputs them into a series of four binary k-means classifiers. Breathing patterns were characterized by normalized variance, nonperiodic power, instantaneous frequency and phase. Signals were classified sample by sample into one of 5 patterns: pause (PAU), movement (MVT), synchronous (SYB) and asynchronous (ASB) breathing, and unknown (UNK). MVT and UNK were combined as UNKNOWN. Twenty-one preprocessed records obtained from infants at risk for POA were analyzed. Performance was evaluated with a confusion matrix, overall accuracy, and pattern specific precision, recall, and F-score. Segments of identical patterns were evaluated for fragmentation and pattern matching with the EM reference. PAU exhibited very low normalized variance. MVT had high normalized nonperiodic power and low frequency. SYB and ASB had a median frequency of respectively, 0.76Hz and 0.71Hz, and a mode for phase of 4^o and 100^o. Overall accuracy was 0.80. AUREA confused patterns most often with UNKNOWN (25.5%). The pattern specific F-score was highest for SYB (0.88) and lowest for PAU (0.60). PAU had high precision (0.78) and low recall (0.49). Fragmentation was evident in pattern events <2s. In 75% of the EM pattern events >2s, 50% of the samples classified by AUREA had identical patterns. Frequency and phase for SYB and ASB were consistent with published values for synchronous and asynchronous breathing in infants. The low normalized variance in PAU, was consistent with published scoring rules for pediatric apnea. These findings support the use of AUREA to classify breathing patterns and warrant a future evaluation of clinically relevant respiratory events.

A Comparison of Sexual Arousal in Men Exposed to Visual Stimuli With and Without Facial Blurring

The role of the facial images in arousal and attraction has been examined before but never via penile plethysmography (PPG). This retrospective chart review aimed to determine the significance and magnitude of differences in arousal measured by PPG in 1,000 men exposed to slide stimuli with or without facial blurring in subjects of various ages. Arousal in response to blurred stimuli was significantly higher than nonanonymized stimuli with modest effect sizes for slides across age and gender categories. Facial blurring increased differences in arousal between adults and adolescents with a modest effect size. Our findings support the use of facial blurring to further protect the anonymity of models and limit the ethical and legal challenges of using slide stimuli with child models.

End-expiratory lung volume remains stable during N2 MBW in healthy sleeping infants

We have previously shown that functional residual capacity (FRC) and lung clearance index were significantly greater in sleeping healthy infants when measured by N2 (nitrogen) washout using 100% O2 (oxygen) versus 4% SF6 (sulfur hexafluoride) washout using air. Following 100% O2 exposure, tidal volumes decreased by over 30%, while end-expiratory lung volume (EELV, i.e., FRC) rose markedly based on ultrasonic flow meter assessments. In the present study to investigate the mechanism behind the observed changes, N2 MBW was performed in 10 separate healthy full-term spontaneously sleeping infants, mean (range) 26 (18-31) weeks, with simultaneous EELV monitoring (respiratory inductance plethysmography, RIP) and oxygen uptake (V´O2 ) assessment during prephase air breathing, during N2 washout by exposure to 100% O2 , and subsequently during air breathing. While flow meter signals suggested a rise in ELLV by mean (SD) 26 (9) ml over the washout period, RIP signals demonstrated no EELV change. V'O2 /FRC ratio during air breathing was mean (SD) 0.43 (0.08)/min, approximately seven times higher than that calculated from adult data. We propose that our previously reported flow meter-based overestimation of EELV was in fact a physiological artifact caused by rapid and marked movement of O2 across the alveolar capillary membrane into the blood and tissue during 100% O2 exposure, without concomitant transfer of N2 to the same degree in the opposite direction. This may be driven by the high observed O2 consumption and resulting cardiac output encountered in infancy. Furthermore, the low resting lung volume in infancy may make this error in lung volume determination by N2 washout relatively large.

Non-invasive vascular assessment in people with type 2 diabetes: Diagnostic performance of Plethysmographic-and-Doppler derived ankle brachial index, toe brachial index, and pulse volume wave analysis for detection of peripheral arterial disease

OBJECTIVE

There is evidence that standard assessment techniques for detecting PAD might be of less diagnostic accuracy in people with type 2 diabetes. The aim of this study was to examine diagnostic performance of Plethysmographic-and-Doppler derived ankle brachial index, toe brachial index, and Pulse volume waveform analysis for detecting PAD in people with T2DM.

METHODS

In this cross-sectional study 303 patients with T2DM were included in the study. The participants underwent ABI measurement, applying both Plethysmographic and Doppler derived devices, as well as TBI, PVW was also recorded for each patient. Diagnostic performance of each test for detecting PAD, applying ultrasound Doppler scan as the reference standard, was measured. Moreover, the best cut-off point for each method to detect PAD was determined.

RESULTS

PVW showed the highest sensitivity (81.8%) for detecting PAD, followed by ABI_DOP (72.7%), and ABI_PLE (20%). However, all devices showed an excellent specificity for detecting PAD. The optimal cut-off point for diagnosis of PAD was 0.9 for ABI_DOP, 1.2 for ABI_PLE, and 0.38 for TBI.

CONCLUSION

Within this population of patients with T2DM, TBI less than 0.38 provided the best sensitivity for detection of PAD followed by PVW, ABI_DOP≤0.9, and ABI_PLE<1.2.

Bronchial thermoplasty reduces airway resistance

BACKGROUND

The mechanism for symptomatic improvement after bronchial thermoplasty (BT) is unclear, since spirometry reveals little or no change. In this study, the effects of BT on airway resistance were examined using two independent techniques.

METHODS

Eighteen consecutive patients, with severe asthma (57.6 ± 14.2 years) were evaluated by spirometry and plethysmography at three time points: (i) baseline, (ii) left lung treated but right lung untreated and (iii) 6 weeks after both lungs were treated with BT. At each assessment, total and specific airway resistance (Raw, sRaw) were measured. High resolution CT scans were undertaken at the first two assessments, and measurements of lobar volume, airway volume and airway resistance were made. The Asthma Control Questionnaire (ACQ) was administered at each assessment.

RESULTS

The baseline ACQ score was 3.5 ± 0.9, and improved progressively to 1.8 ± 1.2 (p < 0.01). At baseline, severe airflow obstruction was observed, FEV1 44.8 ± 13.7% predicted, together with gas trapping, and elevated Raw at 342 ± 173%predicted. Following BT, significant improvements in Raw and sRaw were observed, as well as a reduction in Residual Volume, increase in Vital Capacity and no change in FEV1. The change in Raw correlated with the change in ACQ (r = 0.56, p < 0.05). CT scans demonstrated reduced airway volume at baseline, which correlated with the increased Raw determined by plethysmography (p = - 0.536, p = < 0.05). Following BT, the airway volume increased in the treated lung, and this was accompanied by a significant reduction in CT-determined local airway resistance.

CONCLUSION

Symptomatic improvement after BT is mediated by increased airway volume and reduced airway resistance.

Respiratory-Swallow Coordination Training and Voluntary Cough Skill Training: A Single-Subject Treatment Study in a Person With Parkinson's Disease

Purpose Airway protective disorders are common in Parkinson's disease (PD), yet effective methods to rehabilitate these life-threatening impairments are limited. This study examined the effects of two skill-based treatments aimed at improving swallowing and cough in a severely dysphagic person with PD: respiratory-swallow coordination training (RSCT) and voluntary cough skill training (VCST). It was hypothesized that (a) RSCT would improve respiratory-swallow coordination and swallowing safety and efficiency and (b) VCST would improve reflex and voluntary cough effectiveness. Method An 81-year-old man with midstage PD and severe dysphagia was recruited for study participation. The study utilized a multiple-baseline ABACA experimental design with a 2-month delayed retention assessment. Measures of respiratory-swallow coordination, swallowing safety and efficiency, and cough effectiveness were collected at each assessment using respiratory inductive plethysmography, flexible endoscopic evaluations of swallowing, and spirometry. Data were analyzed descriptively using baseline corrected tau and standard mean difference effect sizes (d). Results Large effect sizes were observed immediately following RSCT for respiratory-swallow coordination (d = 9.17), penetration-aspiration (d = 12.88), vallecular residue (d = 1.75), piriform residue (d = 4.15), and overall dysphagia severity (d = 1.83). Large effect sizes were also observed immediately following VCST for single voluntary cough (d = 4.30), sequential voluntary cough (d = 3.28), and reflex cough (d = 5.58). Improvements were maintained 2 months later for all outcome measures except single voluntary cough. Discussion This is the first study to examine the effects of RSCT and VCST in a person with PD. Robust improvements in respiratory-swallow coordination and swallowing safety and efficiency were achieved following four sessions of RSCT, and significant improvements in reflex and voluntary cough strength were seen following four sessions of VCST. Future work is needed to study these treatments in larger cohorts of people with PD.

Mini-fluid challenge test predicts stroke volume and arterial pressure fluid responsiveness during spine surgery in prone position: A STARD-compliant diagnostic accuracy study

The study was designed to verify if mini-fluid challenge test is more reliable than dynamic fluid variables in predicting stroke volume (SV) and arterial pressure fluid responsiveness during spine surgery in prone position with low-tidal-volume ventilation.Fifty patients undergoing spine surgery in prone position were included. Fluid challenge with 500 mL of colloid over 15 minutes was given. Changes in SV and systolic blood pressure (SBP) after initial 100 mL were compared with SV, pulse pressure variation (PPV), SV variation (SVV), plethysmographic variability index (PVI), and dynamic arterial elastance (Eadyn) in predicting SV or arterial pressure fluid responsiveness (15% increase or greater).An increase in SV of 5% or more after 100 mL predicted SV fluid responsiveness with area under the receiver operating curve (AUROC) of 0.90 (95% confidence interval [CI], 0.82 to 0.99), which was significantly higher than that of PPV (0.71 [95% CI, 0.57 to 0.86]; P = .01), and SVV (0.72 [95% CI, 0.57 to 0.87]; P = .03). A more than 4% increase in SBP after 100 mL predicted arterial pressure fluid responsiveness with AUROC of 0.86 (95% CI, 0.71-1.00), which was significantly higher than that of Eadyn (0.52 [95% CI, 0.33 to 0.71]; P = .01).Changes in SV and SBP after 100 mL of colloid predicted SV and arterial pressure fluid responsiveness, respectively, during spine surgery in prone position with low-tidal-volume ventilation.

A Comparison of SVM and CNN-LSTM Based Approach for Detecting Smoke Inhalations from Respiratory signal

Wearable sensors have successfully been used in recent studies to monitor cigarette smoking events and analyze people's smoking behavior. Respiratory inductive plethysmography (RIP) has been employed to track breathing and to identify characteristic breathing pattern specific to smoking. Pattern recognition algorithms such as Support Vector Machine (SVM), Hidden Markov Model, Decision tree, or ensemble approaches have been used to identify smoke inhalations. However, no deep learning approaches, which have been proved effective to many time series datasets, have ever been tested yet. Hence, a Convolutional Neural Network (CNN) and Long Term Short Memory (LSTM) based approach is presented in this paper to detect smoke inhalations in the breathing signal. To illustrate the effectiveness of this deep learning approach, a traditional machine learning (SVM) based approach was used for comparison. On the validation dataset of 120 smoking sessions performed in a laboratory setting by 30 moderate-to-heavy smokers, the CNN-LSTM approach achieved an F1-score of 72% in leave-one-subject-out (LOSO) cross-validation method whereas the classical SVM approach scored 63%. These results suggest that deep learning-based approaches might provide a better analytical method for detection of smoke inhalations than more conventional machine learning approaches.

Neonatal body composition by air displacement plethysmography in healthy term singletons: a systematic review

BACKGROUND

There is increasing evidence that intrauterine environment and, consequently, growth in utero have both immediate and far-reaching consequences for health. Neonatal body composition might be a more sensitive marker of intrauterine environment and neonatal adiposity than birth weight and could serve as a predictor for non-communicable diseases later in life.

METHODS

To perform a systematic literature review on neonatal body composition determined by air displacement plethysmography in healthy infants. The systematic review was performed using the search terms "air displacement plethysmography", "infant" and "newborn" in Pubmed. Data are displayed as mean (Standard deviation).

RESULTS

Fourteen studies (including n = 6231 infants) using air displacement plethysmography fulfilled inclusion criteria for meta-analysis. In these, weighted mean body fat percentage was 10.0 (4.1) % and weighted mean fat free mass was 2883 (356) g in healthy term infants. Female infants had a higher body fat percentage (11.1 (4.1) % vs. 9.6 (4.0) %) and lower fat free mass (2827 (316) g vs. 2979 (344) g). In the Caucasian subpopulation (n = 2202 infants) mean body fat percentage was 10.8 (4.1), whereas data for reference values of other ethnic groups are still sparse.

CONCLUSIONS

Body composition varies depending on gender and ethnicity. These aggregated data may serve as reference for body composition in healthy, term, singletons at least for the Caucasian subpopulation.

Noise Reduction Technique for Single-Color Video Plethysmography Using Singular Spectrum Analysis

Recently, a contactless method for measuring a biological signal using a video camera has garnered attention. Especially, video plethysmography, a technique for obtaining a pulse wave from a video, is useful for managing the health of people on a daily basis. However, any body movement of a person subjected to the measurement leads to the generation of irregular noise in video plethysmography and reduces the accuracy of the recorded biological information, e.g., heart rate, during the measurement. Blind source separation is a popular technique for eliminating noise from the results of video plethysmography comprising different multiple-color channels. However, it is difficult to apply this technique to a single-color video such as a near-infrared video. Herein, a new method that combines singular spectrum analysis with the circular autocorrelation function is introduced to eliminate irregular noise in single-color video plethysmography. Applying the proposed method on videos collected from 39 individuals improved the estimation accuracy of instantaneous heart rate by approximately 44% over a conventional method using a linear filter. Furthermore, the proposed method also enabled more precise estimations of the heart rate than that achieved using multi-color video plethysmography.

An investigation into the effect of body mass index on the agreement between whole-body fat mass determined by MRI and air-displacement plethysmography

OBJECTIVE

To validate MRI fat measurement protocols using purpose built test objects and by comparison with air-displacement plethysmography (ADP) whole-body fat measurements in non-obese subjects.

METHODS

Test objects of known fat concentration were used to quantify the accuracy of the MRI measurements. 10 participants with a body mass index in the range 18-30 underwent whole-body MRI using two different Dixon-based sequences (LAVA Flex and IDEAL IQ) to obtain an estimate of their whole-body fat mass. The MRI determined fat mass was compared to the fat mass determined by ADP.

RESULTS

MRI test object measurements showed a high correlation to expected fat percentage (r > 0.98). The participant MRI and ADP results were highly correlated (r = 0.99) but on average (mean ± standard deviation) MRI determined a higher fat mass than ADP (3.8 ± 3.1 kg for LAVA Flex and 1.9 ± 3.2 kg for IDEAL IQ). There was no trend in the difference between MRI and ADP with total fat mass.

CONCLUSION

The good agreement between MRI and ADP shows that Dixon-based MRI can be used effectively as a tool in physiological research for non-obese adults.

ADVANCES IN KNOWLEDGE

This work found that for ten non-obese subjects body mass index had no effect on the MRI determination of whole-body fat mass.

Exploring Comfort Levels and the Role of Compensation in Sexual Psychophysiology Study Participation

A number of devices have been developed to assess physiological sexual response. Some come into direct contact with the genitals (e.g., vaginal/clitoral/penile plethysmography [VPP/CPP/PPG], labial thermistors [LT]), whereas others capture images of the genitals remotely (e.g., thermal imaging [TI], laser Doppler imaging [LDI]). Researchers have speculated about the relative invasiveness of these measurement tools, with limited empirical work examining participants' perceptions of different devices and how these may impact volunteer bias. We investigated individuals' levels of comfort with participating in hypothetical sexual psychophysiology studies and their reasons for discomfort. We also examined the relationship between comfort level and compensation for participation. Men (n = 291) and women (n = 716) completed an online survey where they were presented with vignettes describing studies using VPP, CPP, PPG, LT, TI, and LDI. Participants reported their comfort level with the idea of participating in each study, the amount of compensation that would be reasonable, and factors influencing their decision not to participate if they were unwilling. Participants were similarly comfortable with some studies involving genital contact (VPP) or remote imaging (TI), and somewhat less comfortable with others (LDI, LT, PPG; small or small-medium effect sizes). Along with our qualitative analysis, these findings reveal that direct genital contact is one aspect of study intrusiveness, but that it is not necessarily the most important study feature influencing comfort with participation. Our results suggest that providing additional information regarding protocols at screening and offering $50 compensation might attract wider samples of participants.

Simultaneous cardiac and respiratory inhibition during seizure precedes death in the DBA/1 audiogenic mouse model of SUDEP

This study was designed to evaluate cardiac and respiratory dysfunction in a mouse model of sudden unexpected death in epilepsy i.e., SUDEP. We simultaneously monitored respiration via plethysmography and the electrocardiogram via telemetry before, during, and after an audiogenic seizure. DBA/1 mice responded to an acoustic stimulus with one or two cycles of circling and jumping before entering a clonic/tonic seizure. This was followed by death unless the mice were resuscitated by mechanical ventilation using room air. During the initial clonic phase, respiration declined and cardiac rhythm is slowed. By the tonic phase, respiration had ceased, atrial P-waves were absent or dissociated from the QRS complex, and heart rate had decreased from 771±11 to 252±16 bpm. Heart rate further deteriorated terminating in asystole unless the mice were resuscitated at the end of the tonic phase which resulted in abrupt recovery of P-waves and a return to normal sinus rhythm, associated with gasping. Interestingly, P-waves were preserved in the mice treated with methylatropine during the pre-ictal period (to block parasympathetic stimulation) and heart rate remained unchanged through the end of the tonic phase (765±8 vs. 748±21 bpm), but as in control, methylatropine treated mice died from respiratory arrest. These results demonstrate that a clonic/tonic seizure in the DBA/1 mouse results in abrupt and simultaneous respiratory and cardiac depression. Although death clearly results from respiratory arrest, our results suggest that seizure activates two central nervous system pathways in this model-one inhibits respiratory drive, whereas the other inhibits cardiac function via vagal efferents. The abrupt and simultaneous recovery of both respiration and cardiac function with mechanical ventilation within an early post-ictal timeframe shows that the vagal discharge can be rapidly terminated. Understanding the central mechanism associated with the abrupt cardiorespiratory dysfunction and equally abrupt recovery may provide clues for therapeutic targets for SUDEP.

Continuous Distant Measurement of the User's Heart Rate in Human-Computer Interaction Applications

In real world scenarios, the task of estimating heart rate (HR) using video plethysmography (VPG) methods is difficult because many factors could contaminate the pulse signal (i.e., a subjects’ movement, illumination changes). This article presents the evaluation of a VPG system designed for continuous monitoring of the user’s heart rate during typical human-computer interaction scenarios. The impact of human activities while working at the computer (i.e., reading and writing text, playing a game) on the accuracy of HR VPG measurements was examined. Three commonly used signal extraction methods were evaluated: green (G), green-red difference (GRD), blind source separation (ICA). A new method based on an excess green (ExG) image representation was proposed. Three algorithms for estimating pulse rate were used: power spectral density (PSD), autoregressive modeling (AR) and time domain analysis (TIME). In summary, depending on the scenario being studied, different combinations of signal extraction methods and the pulse estimation algorithm ensure optimal heart rate detection results. The best results were obtained for the ICA method: average RMSE = 6.1 bpm (beats per minute). The proposed ExG signal representation outperforms other methods except ICA (RMSE = 11.2 bpm compared to 14.4 bpm for G and 13.0 bmp for GRD). ExG also is the best method in terms of proposed success rate metric (sRate).

The Accuracy of Respiratory Calibration Methods for Estimating Lung Volume During Speech Breathing: A Comparison of Four Methods Across Three Adult Cohorts

Purpose This study evaluated the accuracy of respiratory calibration methods for estimating lung volume during speech breathing. Method Respiratory kinematic data were acquired via inductance plethysmography in 32 young adults, 22 older adults, and 13 older adults with Parkinson's disease (PD). Raw rib cage (RC) and abdomen (AB) signals (V) were calibrated to liters using 4 correction methods: (a) isovolume maneuvers, (b) a constant 2:1 RC-to-AB ratio, (c) least squares method with RC correction only (LsqRC), and (d) least squares method with both RC and AB corrections (LsqRC/AB). Mean percent error, the absolute difference between estimated and actual lung volumes then normalized to each speaker's vital capacity, was calculated for each method. Results For young adults, the LsqRC/AB method significantly reduced mean percent error compared to all other methods. Although LsqRC/AB also resulted in smaller errors for older adults and adults with PD, LsqRC/AB and LsqRC were not significantly different from one another in these groups. Conclusion The LsqRC/AB method reduces errors across all cohorts, but older adults and adults with PD also have reduced errors when using LsqRC. Further research should investigate both least squares methods across larger age and disease severity ranges.

Acute effects of three pulmonary reexpansion modalities on thoracoabdominal motion of healthy subjects: Randomized crossover study

BACKGROUND

Chest physiotherapy can be an alternative to increase lung volumes through pulmonary expansion therapies, but there is still inconsistency in the literature in order to determine which device can promote a greater volume increase at the expense of a better ventilatory pattern. Therefore, the aim of this study was to evaluate and compare the chest wall kinematics of healthy subjects submitted to the use of three different devices for pulmonary reexpansion.

METHODS

Chest wall compartmental and operational volumes, breathing pattern and thoracoabdominal asynchrony were evaluated in 12 healthy individuals through optoelectronic plethysmography during quiet breathing, pulmonary reexpansion and recovery. Three different devices (volume-oriented incentive spirometer-IS-v; positive expiratory pressure-PEP; and incentive spirometer volume and pressure oriented-IS-vp) were administered in a random order with at least 48h between the devices.

RESULTS

A greater volume variation in the chest wall and its compartments was observed when the IS-vp was used in comparison with the other devices (p<0.05). Furthermore, the IS-vp mobilizes a greater amount of volume accompanied by greater synchronism between the compartments when compared to IS-v (p <0.05).

CONCLUSION

The IS-vp may be able to increase total and compartmental chest wall volumes, as well as improve synchrony among compartments when compared to IS-v and PEP devices, thus constituting an important tool for treating patients with restrictive ventilatory pattern.

Apnea and hypopnea characterization using esophageal pressure, respiratory inductance plethysmography, and suprasternal pressure: a comparative study

OBJECTIVES

To determine if recording of suprasternal pressure (SSP) can classify apneas and hypopneas as reliably as respiratory inductance plethysmography (RIP) belts and to compare the two methods to classification with esophageal pressure (Pes), the reference method for assessing respiratory effort.

METHODS

In addition to polysomnographic recordings that included Pes, SSP was recorded. Recordings from 32 patients (25 males, mean age 66.7 ± 15.3 years, and mean BMI 30.1 ± 4.5 kg/m²) were used to compare the classification of detected apneas and hypopneas by three methods of respiratory effort evaluation (Pes, RIP belts, and SSP). Signals were analyzed randomly and independently from each other. All recordings were analyzed according to AASM guidelines.

RESULTS

Using Pes as a reference for apnea characterization, the Cohen kappa (κ) was 0.93 for SSP and 0.87 for the RIP. The sensitivity/specificity of SSP was 97.0%/96.9% for obstructive, 93.9%/98.3% for central, and 94.9%/97.9% for mixed apneas. The sensitivity/specificity of the RIP was 97.4%/91.9% for obstructive, 87.5%/97.9% for central, and 85.6%/96.6% for mixed apneas. For hypopnea characterization using the Pes as a reference, κ was 0.92 for SSP and 0.86 for the RIP. The sensitivity/specificity of SSP was 99.7%/97.6% for obstructive and 97.6%/99.7% for central. The sensitivity/specificity of the RIP was 99.8%/81.1% for obstructive and 81.1%/99.8% for central.

CONCLUSIONS

These results confirm the excellent agreement in the detection of respiratory effort between SSP, RIP belts, and Pes signals. Thus, we conclude that apnea and hypopnea characterization in adults with SSP is a reliable method.

The effects of passive leg raising may be detected by the plethysmographic oxygen saturation signal in critically ill patients

BACKGROUND

A passive leg raising (PLR) test is positive if the cardiac index (CI) increased by > 10%, but it requires a direct measurement of CI. On the oxygen saturation plethysmographic signal, the perfusion index (PI) is the ratio between the pulsatile and the non-pulsatile portions. We hypothesised that the changes in PI could predict a positive PLR test and thus preload responsiveness in a totally non-invasive way.

METHODS

In patients with acute circulatory failure, we measured PI (Radical-7) and CI (PiCCO2) before and during a PLR test and, if decided, before and after volume expansion (500-mL saline).

RESULTS

Three patients were excluded because the plethysmography signal was absent and 3 other ones because it was unstable. Eventually, 72 patients were analysed. In 34 patients with a positive PLR test (increase in CI ≥ 10%), CI and PI increased during PLR by 21 ± 10% and 54 ± 53%, respectively. In the 38 patients with a negative PLR test, PI did not significantly change during PLR. In 26 patients in whom volume expansion was performed, CI and PI increased by 28 ± 14% and 53 ± 63%, respectively. The correlation between the PI and CI changes for all interventions was significant (r = 0.64, p < 0.001). During the PLR test, if PI increased by > 9%, a positive response of CI (≥ 10%) was diagnosed with a sensitivity of 91 (76-98%) and a specificity of 79 (63-90%) (area under the receiver operating characteristics curve 0.89 (0.80-0.95), p < 0.0001).

CONCLUSION

An increase in PI during PLR by 9% accurately detects a positive response of the PLR test.

TRIAL REGISTRATION

ID RCB 2016-A00959-42. Registered 27 June 2016.

Measurement agreement in percent body fat estimates among laboratory and field assessments in college students: Use of equivalence testing

The purpose of this study was to examine the agreement in percent body fat estimates among 7 laboratory and field assessments against dual-emission x-ray absorptiometry using equivalence testing. Participants were 437 college students (mean age = 19.2±0.6 years). Dual-emission x-ray absorptiometry was used as the criterion with hydrostatic weighing, skinfold thickness, air displacement plethysmography, near infrared reactance, and three methods of bioelectrical impedance analysis examined as surrogate assessments. Relative agreement was examined using intraclass correlation coefficients. Group level agreement was examined using equivalence testing. Individual-level agreement was assessed using Mean Absolute Percent Error and Bland-Altman Plots. Single measure intraclass correlation coefficient scores ranged from 0.71-0.80. Hydrostatic weighing, skinfold thickness, air displacement plethysmography, and 4-electrode bioelectrical impedance analysis showed statistical equivalence with the criterion using a 10% Equivalence Interval with absolute mean differences ranging from 1.0%-4.9% body fat. Mean Absolute Percent Error ranged from 11.7% using skinfold thickness to 21.9% using Omron (hand-held) bioelectrical impedance analysis. Limits of Agreement were heteroscedastic across the range of mean scores compared to dual-emission x-ray absorptiometry, with greater mean differences observed at higher levels of percent body fat. Hydrostatic weighing, skinfold thickness, air displacement plethysmography, and 4-electrode bioelectrical impedance analysis showed strong evidence for statistical equivalence with dual-emission x-ray absorptiometry in a sample of college students.

Body Mass Index Is a Better Indicator of Body Composition than Weight-for-Length at Age 1 Month

OBJECTIVE

To assess whether body mass index (BMI) provides a better assessment of measured adiposity at age 1 month compared with weight-for-length (WFL).

STUDY DESIGN

Participants were healthy term-born infants in the Infant Growth and Microbiome (n = 146) and the Baby Peas (n = 147) studies. Length, weight, and body composition by air displacement plethysmography were measured at 1 month. World Health Organization-based WFL and BMI z-scores were calculated. Within-cohort z-scores of percent fat-Z, fat mass-Z, fat mass/length2-Z, fat mass/length3-Z, fat-free mass-Z, and fat-free mass/length2-Z were calculated. Correlation and multiple linear regression (adjusted for birth weight) analyses tested the associations between body composition outcomes and BMI-Z vs WFL-Z. Quantile regression was used to test the stability of these associations across the distribution of body compositions.

RESULTS

The sample was 52% female and 56% African American. Accounting for birth weight, both BMI-Z and WFL-Z were strongly associated with fat mass-Z (coefficients 0.56 and 0.35, respectively), FM/L2-Z (0.73 and 0.51), and FM/L3-Z (0.79 and 0.58), with stronger associations for BMI-Z compared with WFL-Z (P < .05). Even after accounting statistically for birth weight, BMI-Z was persistently more strongly associated than WFL-Z with body composition outcomes across the distribution of body composition outcomes.

CONCLUSIONS

We demonstrate in 2 distinct cohorts that BMI is a better indicator of adiposity in early infancy compared with WFL. Our findings support the preferred use of BMI for growth and nutritional status assessment in infancy.

Body composition measurement by air displacement plethysmography in pregnancy: Comparison of predicted versus measured thoracic gas volume

OBJECTIVES

Body composition measurements with air displacement plethysmography (ADP) define body volume, which must be corrected for thoracic gas volume (TGV). We hypothesized that physiologic changes owing to pregnancy could affect the accuracy of predicted TGV and introduce errors into body composition measurements.

METHODS

We investigated the effect of measuring versus predicting TGV on the accuracy of body composition calculations measured with ADP in overweight and obese pregnant women. The fat and fat-free masses of 110 women were determined with ADP with predicted and measured TGV.

RESULTS

Measured TGV decreased from early to late pregnancy (P = 0.0002). Compared with measured TGV, predicted TGV was 6.3% higher during early gestation and 12.6% higher during late gestation (both P ≤ 0.001). The use of predicted instead of measured TGV in body composition calculations resulted in an overestimation of fat mass by 0.8% during the early stage, and 2.6% during the late stage of pregnancy (both P ≤ 0.001).

CONCLUSIONS

Measuring TGV increases the accuracy of body composition measurement by ADP in overweight and obese women, particularly during the late stage of pregnancy.

Body Composition Growth Patterns in Early Infancy: A Latent Class Trajectory Analysis of the Ethiopian iABC Birth Cohort

OBJECTIVE

The objective of this study was to identify subgroups with distinct fat and fat-free growth patterns in the first 6 months of life and describe predictors of these different patterns.

METHODS

A total of 510 apparently healthy Ethiopian infants were followed from birth to 6 months of age. Each infant had at least three and up to six repeated measurements of fat and fat-free mass using air-displacement plethysmography. Latent class trajectory analyses were used to categorize infants in groups with distinct body composition patterns.

RESULTS

Four distinct fat mass and two fat-free mass growth patterns were identified. Of the infants measured, 5% presented a delayed fat growth pattern and 3% presented a catch-up fat growth pattern involving low birth weight but a significant fat growth velocity from 2.5 to 6 months. A large class had a high fat level at birth and an accelerated fat growth pattern in early infancy. Fat-free growth was represented by two distinct classes with less variability. Catch-up growth was primarily seen in fat mass.

CONCLUSIONS

We identified distinct patterns of delayed, catch-up, and accelerated fat growth in early infancy. This variability is not detected in regular anthropometric assessment and could be a mechanism linking early growth with later obesity and cardiometabolic risk.

Methods for the determination of skeletal muscle blood flow: development, strengths and limitations

Since the first measurements of limb blood flow at rest and during nerve stimulation were conducted in the late 1800s, a number of methods have been developed for the determination of limb and skeletal muscle blood flow in humans. The methods, which have been applied in the study of aspects such as blood flow regulation, oxygen uptake and metabolism, differ in terms of strengths and degree of limitations but most have advantages for specific settings. The purpose of this review is to describe the origin and the basic principles of the methods, important aspects and requirements of the procedures. One of the earliest methods, venous occlusion plethysmography, is a noninvasive method which still is extensively used and which provides similar values as other more direct blood flow methods such as ultrasound Doppler. The constant infusion thermodilution method remains the most appropriate for the determination of blood flow during maximal exercise. For resting blood flow and light-to-moderate exercise, the non-invasive ultrasound Doppler methodology, if handled by a skilled operator, is recommendable. Positron emission tomography with radiolabeled water is an advanced method which requires highly sophisticated equipment and allows for the determination of muscle-specific blood flow, regional blood flows and estimate of blood flow heterogeneity within a muscle. Finally, the contrast-enhanced ultrasound method holds promise for assessment of muscle-specific blood flow, but the interpretation of the data obtained remains uncertain. Currently lacking is high-resolution methods for continuous visualization and monitoring of the skeletal muscle microcirculation in humans.

Can diaphragmatic breathing modify chest wall volumes during inspiratory loaded breathing in patients with heart failure?

BACKGROUND

Some inspiratory muscle training protocols for patients with heart failure report the request of diaphragmatic breathing during inspiratory loaded breathing. However, it is unclear whether this condition modifies the chest wall volumes.

OBJECTIVE

The primary purpose was to evaluate chest wall volumes during inspiratory loaded breathing as well as during inspiratory loaded breathing associated with diaphragmatic breathing in patients with heart failure.

METHODS

Sixteen men with heart failure functional class I to III, aged 50(SD=7) years were evaluated. Volumes of the pulmonary rib cage, abdominal rib cage and abdomen, as well as other breathing pattern variables, were assessed by optoelectronic plethysmography during quiet breathing, inspiratory loaded breathing, and inspiratory loaded breathing associated with diaphragmatic breathing.

RESULTS

Chest wall tidal volume significantly increased from quiet breathing 0.53(SD=0.14)L to inspiratory loaded breathing 1.33(SD=0.48)L and to inspiratory loaded breathing associated with diaphragmatic breathing 1.36(SD=0.48)L. A significant volume variation was observed on the three compartments (p<0.05 for all). During inspiratory loaded breathing associated with diaphragmatic breathing, patients showed increased abdominal volume compared to quiet breathing [0.28(SD=0.05) to 0.83(SD=0.47)L, p<0.001]; as well as from inspiratory loaded breathing [0.63(SD=0.23) to 0.83(SD=0.47)L, p=0.044]. No significant changes were observed between the two inspiratory loaded breathing conditions on the percentages of the contribution of each chest wall compartment for the tidal volume, respiratory rate, minute ventilation, and duty cycle.

CONCLUSION

When inspiratory loaded breathing was associated with diaphragmatic breathing, a higher volume in the abdominal compartment was obtained without significant changes in other breathing pattern variables.