Use of a triaxial magnetometer for respiratory measurements

Telemonitoring Techniques for Lung Volume Measurement: Accuracy, Artifacts and Effort

Telemonitoring becomes more important in pulmonary research. It can be used to decrease the pressure on the health care system, to lower the costs of health care and to increase quality of life of patients. Previous studies show contradictory results regarding the effectiveness of telemonitoring. According to multiple researchers, inefficiency can be a result of poor study design, low data quality and usability issues. To counteract these issues, this review proves for an in-depth explanation of four (potential) telemonitoring systems in terms of work principle, accuracy, disturbing factors and usability. The evaluated systems are portable spirometry/breath-by-breath analyzers, respiratory inductance and magnetic plethysmography and electrical impedance tomography. These insights can be used to select the optimal technique for a specific purpose in future studies.

Chest wall motion analysis in healthy volunteers and adults with cystic fibrosis using a novel Kinect-based motion tracking system

Respiratory disease is the leading cause of death in the UK. Methods for assessing pulmonary function and chest wall movement are essential for accurate diagnosis, as well as monitoring response to treatment, operative procedures and rehabilitation. Despite this, there is a lack of low-cost devices for rapid assessment. Spirometry is used to measure air flow expired, but cannot infer or directly measure full chest wall motion. This paper presents the development of a low-cost chest wall motion assessment system. The prototype was developed using four Microsoft Kinect sensors to create a 3D time-varying representation of a patient's torso. An evaluation of the system in two phases is also presented. Initially, static volume of a resuscitation mannequin with that of a Nikon laser scanner is performed. This showed the system has slight underprediction of 0.441 %. Next, a dynamic analysis through the comparison of results from the prototype and a spirometer in nine cystic fibrosis patients and thirteen healthy subjects was performed. This showed an agreement with correlation coefficients above 0.8656 in all participants. The system shows promise as a method for assessing respiratory disease in a cost-effective and timely manner. Further work must now be performed to develop the prototype and provide further evaluations.

Influence of posture on the ventilatory pattern and the thoraco-abdominal kinematics of patients with chronic obstructive pulmonary disease (COPD)

OBJECTIVE

Evaluate the influence of posture on ventilatory pattern, compartmental distribution of volume of chest wall and thoraco-abdominal kinematics of patients with severe chronic obstructive pulmonary disease (COPD).

DESIGN

Cross-sectional study.

METHODS

Twelve, male patients with severe COPD (Forced Expiratory Volume in the first second (FEV1) = 24.35 ± 4.52%, Forced Vital Capacity% (FVC%) = 60 ± 13.39% and relationship FEV1/FVC = 53.42 ± 14.47). The distribution of the volume of the ribcage [pulmonary rib cage (Rcp), abdominal ribcage (Rca) and abdomen (Ab)] during quiet breathing in a sitting position without back support (SWB), sitting with backrest (SB) and supine position (SUP) was determined using an opto-electronic plethysmograph.

RESULTS

The following differences were observed: a greater tidal volume in the SWB position when compared to the SB position (p = 0.01); greater expiratory time in the SUP position in relation to the SWB (p = 0.03) and SB (p = 0.01); and increased abdominal contribution to the tidal volume in the SUP position in relation to the SWB (p < 0.01) and SB (p < 0.001). No difference was found in the thoraco-abdominal synchrony among the positions.

CONCLUSION

Sitting position without back support enhances the activation of respiratory muscles by increasing the tidal volume and supine position seems to favor lung deflation by increasing the expiratory time. It seems appropriate to adopt these positions to optimize the ventilation/perfusion relationship and physiotherapeutic intervention in different clinical conditions.

Noncontact respiratory measurement of volume change using depth camera

In this study, a system is developed to measure human chest wall motion for respiratory volume estimation without any physical contact. Based on depth image sensing technique, respiratory volume is estimated by measuring morphological changes of the chest wall. We evaluated the system and compared with a standard reference device, and the results show strong agreement in respiratory volume measurement [correlation coefficient: r=0.966]. The isovolume test presents small variations of the total respiratory volume during the isovolume maneuver (standard deviation&#60;107 ml). Then, a regional pulmonary measurement test is evaluated by a patient, and the results show visibly difference of pulmonary functional between the diseased and the contralateral sides of the thorax after the thoracotomy. This study has big potential for personal health care and preventive medicine as it provides a novel, low-cost, and convenient way to measure user's respiration volume.

Color structured light system of chest wall motion measurement for respiratory volume evaluation

We present a structured light system to dynamically measure human chest wall motion for respiratory volume estimation. Based on a projection of an encoded color pattern and a few active markers attached to the trunk, respiratory volumes are obtained by evaluating the 3-D topographic changes of the chest wall in an anatomically consistent measuring region during respiration. Three measuring setups are established: a single-sided illuminating-recording setup for standing posture, an inclined single-sided setup for supine posture, and a double-sided setup for standing posture. Results are compared with the pneumotachography and show good agreement in volume estimations [correlation coefficient: R>0.99 (P<0.001) for all setups]. The isovolume tests present small variations of the obtained volume during the isovolume maneuver (standard deviation<0.085 L for all setups). After validation by the isovolume test, an investigation of a patient with pleural effusion using the proposed method shows pulmonary functional differences between the diseased and the contralateral sides of the thorax, and subsequent improvement of this imbalance after drainage. These results demonstrate the proposed optical method is capable of not only whole respiratory volume evaluation with high accuracy, but also regional pulmonary function assessment in different chest wall behaviors, with the advantage of whole-field measurement.

Comparative evaluation of susceptibility to motion artifact in different wearable systems for monitoring respiratory rate

The purpose of this study is to comparatively evaluate the performance of different wearable systems based on indirect breathing monitoring in terms of susceptibility to motion artifacts. These performances are compared with direct respiratory measurements using a spirometer, which is accurate, reliable, and less sensitive to movement artifacts, but cannot be integrated into truly wearable form. Experiments were carried out on four indirect methods implemented into wearable systems, inductive plethysmography, impedance plethysmography, piezoresistive pneumography, and piezoelectric pneumography, to ascertain the performance of each of them in terms of noise due to movement artifacts, as well as to study the effects of different movements or gestures during each test. A group of volunteers was asked to wear all of the breath monitoring systems simultaneously along with the face mask of the spirometer while carrying out four physical exercises in a gym under controlled conditions. Data are analyzed in the time and frequency domain to estimate the frequency respiration from each wearable system and compare it with those of the spirometer. Results confirmed that all the wearable systems are somehow affected by movement artifacts, but statistical investigation showed that for most of the physical exercises, three out of four, piezoelectric pneumography provided best performance in terms of robustness and reduced susceptibility to movement artifacts.

The influence of fundamental frequency and sound pressure level range on breathing patterns in female classical singing

PURPOSE

This study investigated the influence of fundamental frequency (F0) and sound pressure level (SPL) range on respiratory behavior in classical singing.

METHOD

Five trained female singers performed an 8-s messa di voce (a crescendo and decrescendo on one F0) across their musical F0 range. Lung volume (LV) change was estimated, and chest-wall kinematic behavior (dimensional change in ribcage [RC] and abdominal [AB] wall) was recorded using triaxial magnetometry.

RESULTS

The direction of F0 influence on LV excursion (LVE) varied among singers, but SPL range appeared to be less important than duration to LVE. LVE was generally evenly divided between crescendo and decrescendo. Kinematic patterns differed markedly among singers, despite task consistency, and RC and AB paradoxing was widespread.

CONCLUSION

Each singer maintained her characteristic kinematic pattern regardless of F0 or SPL range, although these did influence aspects of RC and AB behavior. Given the essential role of breathing in classical singing, further work is needed to understand how singers develop their highly individual respiratory strategies and the principles by which each singer's breathing strategy can be optimized.

Application of long-period-grating sensors to respiratory plethysmography

A series of in-line curvature sensors on a garment are used to monitor the thoracic and abdominal movements of a human during respiration. These results are used to obtain volumetric tidal changes of the human torso in agreement with a spirometer used simultaneously at the mouth. The curvature sensors are based on long-period gratings (LPGs) written in a progressive three-layered fiber to render the LPGs insensitive to the refractive index external to the fiber. A curvature sensor consists of the fiber long-period grating laid on a carbon fiber ribbon, which is then encapsulated in a low-temperature curing silicone rubber. The sensors have a spectral sensitivity to curvature, d lambda/dR from approximately 7-nm m to approximately 9-nm m. The interrogation technique is borrowed from derivative spectroscopy and monitors the changes in the transmission spectral profile of the LPG's attenuation band due to curvature. The multiplexing of the sensors is achieved by spectrally matching a series of distributed feedback (DFB) lasers to the LPGs. The versatility of this sensing garment is confirmed by it being used on six other human subjects covering a wide range of body mass indices. Just six fully functional sensors are required to obtain a volumetric error of around 6%.

Repetitive paired-pulse transcranial magnetic stimulation affects corticospinal excitability and finger tapping in Parkinson's disease

OBJECTIVES

To study the effect of long trains of a recently established conditioning-test paired-pulse repetitive transcranial magnetic stimulation (rTMS) paradigm on corticospinal excitability and finger tapping speed.

METHODS

We applied 900 inhibiting or facilitating paired-pulses or 900 real or sham single stimuli at 1Hz over the motor cortex contralateral to the dominant hand of 9 healthy subjects and contralateral to the more affected hand of 11 patients with Parkinson's disease.

RESULTS

In both groups, motor evoked potentials (MEPs) from suprathreshold pulses were larger after facilitating paired-pulses than after inhibiting paired-pulses. After real single-pulse rTMS and after either type of paired-pulse rTMS patients showed an increase in finger tapping frequency on the stimulated hand. Tapping was unchanged contralaterally, after sham stimuli, and in controls. Tremor and tapping frequencies were not correlated, nor was the change in MEP size correlated to the change in tapping frequency.

CONCLUSIONS

Repetitive paired-pulses allow selective induction of corticospinal inhibition or facilitation, but do not enhance the transient improvement of finger motility induced by conventional single-pulse rTMS.

Early and long-term functional outcomes following lung volume reduction surgery

In the past 3 years, lung volume reduction surgery has become the most controversial topic in the clinical management of patients with emphysema. Although literature has added to the understanding of the procedure, many important issues remain unclear. This article emphasizes functional and basic physiologic changes that occur following lung volume reduction surgery in patients with emphysema.

Chest wall and lung volume estimation by optical reflectance motion analysis

Estimation of chest wall motion by surface measurements only allows one-dimensional measurements of the chest wall. We have assessed on optical reflectance system (OR), which tracks reflective markers in three dimensions (3-D) for respiratory use. We used 86 (6-mm-diameter) hemispherical reflective markers arranged circumferentially on the chest wall in seven rows between the sternal notch and the anterior superior iliac crest in two normal standing subjects. We calculated the volume of the entire chest wall and compared inspired and expired volumes with volumes obtained by spirometry. Marker positions were recorded by four TV cameras; two were 4 m in front of and two were 4 m behind the subject. The TV signals were sampled at 100 Hz and combined with grid calibration parameters on a personal computer to obtain the 3-D coordinates of the markers. Chest wall surfaces were reconstructed by triangulation through the point data, and chest wall volume was calculated. During tidal breathing and vital capacity maneuvers and during CO2-stimulated hyperpnea, there was a very close correlation of the lung volumes (VL) estimated by spirometry [VL(SP)] and OR [VL(OR)]. Regression equations of VL(OR) (y) vs. VL(SP) (x, BTPS in liters) for the two subjects were given by y = 1.01x-0.01 (r = 0.996) and y = 0.96x + 0.03 (r = 0.997), and by y = 1.04x + 0.25 (r = 0.97) and y = 0.98x + 0.14 (r = 0.95) for the two maneuvers, respectively. We conclude spirometric volumes can be estimated very accurately and directly from chest wall surface markers, and we speculate that OR may be usefully applied to calculations of chest wall shape, regional volumes, and motion analysis.

A new instrument for the measurement of rib cage and abdomen circumference variation in respiration at rest and during exercise

A simple and inexpensive new extensometer for measuring changes in chest wall circumference during human respiratory movements is presented. The instrument detects the delay between ultrasound emission and reception at opposite ends of two rubber tubes encircling the rib cage and abdomen. Assuming a two degree of freedom model of the chest wall and employing an isovolume procedure for determination of volume-motion coefficients, extensometer estimation of tidal volume (VT) from changes of rib cage and abdomen circumference was compared with spirometer measurements at rest and during exercise on a cycle ergometer (55-155 W) in six subjects and, in four of them, on a treadmill (4-12 km.h-1). In three subjects hypercapnic hyperpnoea at rest was also studied. The slopes of the linear relationship between extensometer and spirometer VT (litres) averaged 0.9967 (SD 0.0117) (r2 = 0.995-0.998; n = 90-143) for cycle ergometer exercise, 1.0072 (SD 0.0078) (r2 = 0.991-0.998; n = 75-93) for treadmill exercise and 0.9942 (SD 0.0188) (r2 = 0.997-0.998; n = 18-25) for hypercapnic hyperpnoea. In all instances the slope of the regression line was consistent with the model of the identity line (slope = 1). The changes in end-expiratory lung volume between respiration at rest and during exercise were determined by the extensometers, and were nearly identical (98.4% on average) to those measured with the spirometer (r2 = 0.945; n = 24). It is concluded that determination of chest wall circumference with this new instrument is suitable for quantitative measurement of ventilation and lung volume variations in humans under most physiological conditions.

An optical technique for the measurement of thoracic wall movement during high-frequency jet ventilation

Instrumentation for use in high-frequency jet ventilation is not currently capable of providing information suitable for predicting gas exchange. Whilst techniques for the accurate measurement of tidal volume during jet ventilation are now available, the relationship between tidal volume and the efficiency of gas exchange varies with frequency and inspiratory/expiratory time (I:E) ratio. We report technical details of a new non-invasive instrument capable of accurately measuring displacement of the thoracic wall at high frequencies and without electrical connection to the patient. It is hoped that use of this instrument will allow the calculation of an efficiency index for the transduction of airway pressure changes into peripheral expansion. It is also hoped that this index may be of value in predicting the gas exchange response to changes in jet parameters.