Electromagnetic inductance plethysmography is well suited to measure tidal breathing in infants

Prediction of Tidal Volume in Newborns Through a Novel Three-Dimensional Model: A Viability Study

INTRODUCTION

Although noninvasive monitoring through quantifying rib cage movement has been useful in serial assessment of pulmonary function in newborns, measuring tidal volume (TV) is commonly performed invasively. As it is the most basic measure of pulmonary function, expanding its assessment to a noninvasive measure can contribute to clinical findings and interpretations in neonatal clinical practice.

OBJECTIVE

(1) Create a noninvasive measurement tool for TV for neonatal clinical use; (2) Evaluate the agreement between measured TV and predicted TV.

METHODS

Observational study with healthy newborns. Predicted TV was calculated based on the newborns' weight using the mid-range of the volumes usually set during mechanical ventilation of term infants (5 mL/kg). For measured TV, newborns were filmed in supine position using a digital camera, and their chest circumferences were measured with a nonelastic tape. Body markers delimited the segmentation of the area of interest, and a MATLAB software routine established their relationship with the area in cm² and generated a representative image of the thoracic and abdominal areas in a cylindrical, elliptical-based format, as well as a three-dimensional model to represent quantitative data of measured TV. Paired t-test assessed the means of measured and predicted TV, Pearson's correlation assessed level of association, and Kappa coefficient assessed the agreement between them.

RESULTS

Newborns' gestational ages ranged from 38 to 40 weeks and weights from 2190 to 4125 g. A total of 56 respiratory cycles were validated for analysis. The mean predicted TV according to weight was 5.06 mL/kg, and measured TV was 5 ml/kg (p = 0.31), with a correlation of 0.7 (p < 0.001) and a kappa coefficient of 0.39 (p = 0.01).

CONCLUSIONS

MATLAB software routine was a practical and easy-to-use tool to monitor noninvasive TV in a neonatal setting. There was no difference between predicted and estimated TV, with fair agreement between them.

A Pediatric Upper Airway Library to Evaluate Interpatient Variability of In Silico Aerosol Deposition

The airway of pediatric patients' changes through development, presenting a challenge in developing pediatric-specific aerosol therapeutics. Our work aims to quantify geometric variations and aerosol deposition patterns during upper airway development in subjects between 3.5 months-6.9 years old using a library of 24 pediatric models and 4 adult models. Computational fluid-particle dynamics was performed with varying particle size (0.1-10 μm) and flow rate (10-120 Lpm), which was rigorously analyzed to compare anatomical metrics (epiglottis angle (θE), glottis to cricoid ring ratio (GC-ratio), and pediatric to adult trachea ratio (H-ratio)), inhaler metrics (particle diameter, [Formula: see text], and flow rate, Q), and clinical metrics (age, sex, height, and weight) against aerosol deposition. Multivariate non-linear regression indicated that all metrics were all significantly influential on resultant deposition, with varying influence of individual parameters. Additionally, principal component analysis was employed, indicating that [Formula: see text], Q, GC-ratio, θE, and sex accounted for 90% of variability between subject-specific deposition. Notably, age was not statistically significant among pediatric subjects but was influential in comparing adult subjects. Inhaler design metrics were hugely influential, thus supporting the critical need for pediatric-specific inhalable approaches. This work not only improves accuracy in prescribing inhalable therapeutics and informing pediatric aerosol optimization, but also provides a framework for future aerosol studies to continue to strive toward optimized and personalized pediatric medicine.

Prematurity-associated wheeze: current knowledge and opportunities for further investigation

Prematurity-associated wheeze is a common complication of preterm birth, with significant impact on the health and healthcare utilization of former preterm infants. This wheezing phenotype remains poorly understood and difficult to predict. This review will discuss the current state of the literature on prematurity-associated wheeze. We will discuss etiology and pathophysiology, and offer two conceptual models for the pathogenesis of this complex condition. This review will also identify current methods of ascertainment, and discuss the strengths and limitations of each. We will explore research-backed approaches to prevention and management, and finally suggest both pre-clinical and clinical avenues for investigation. An in-depth understanding of prematurity-associated wheeze will aid clinicians in its diagnosis and management, and inspire scientists to pursue much-needed further study into causes and prevention of this common and impactful condition. IMPACT: There is no recent, concise review on the current state of research on prematurity-associated wheeze, which is a rapidly evolving area of study. This article highlights causal models of wheeze, methods of ascertainment, management strategies for the clinician, and opportunities for further research for the physician scientist.

Electromagnetic inductance plethysmography to study airflow after nebulized saline in bronchiolitis

BACKGROUND

Spirometric effects from therapeutic interventions in infants with severe respiratory distress cannot readily be measured, hampering development of better treatment for acute bronchiolitis. Inhaled normal saline is regularly used in these infants, with little knowledge of how this influences lung physiology.

OBJECTIVES

Assess feasibility of infant lung function testing using electromagnetic inductance plethysmography (EIP) in a clinical setting in a busy pediatric department, and explore effects from inhaled normal saline on tidal flow-volume loops in infants with acute bronchiolitis.

METHODS

Observational study conducted at the Children's Clinic, Haukeland University Hospital, Bergen, Norway during the winters 2016 and 2017, enrolling children with bronchiolitis below six months of age. EIP was performed immediately before and 5 and 20 min after saline inhalation. EIP is a noninvasive method to measure tidal breathing parameters by quantifying volume changes in the chest and abdomen during respiration. The method consists of an electromagnet/antenna and a patient vest.

RESULTS

EIP was successfully applied in 36/45 (80%) enrolled infants at mean (standard deviation) age 2.9 (2.5) months, after a hospital stay of 2.2 (1.9) days. After saline inhalation, tidal expiratory to inspiratory time ratio (Te/Ti) had increased significantly, whereas the other relevant flow/volume parameters had changed numerically in a direction compatible with a more obstructive pattern.

CONCLUSIONS

EIP could successfully be used to obtain tidal breathing parameters in infants with respiratory distress and appears a promising tool for assessment of therapeutic interventions in bronchiolitis. Saline inhalations should be used with caution as placebo in intervention studies.

Physiological effects of high-flow nasal cannula therapy in preterm infants

OBJECTIVE

High-flow nasal cannula (HFNC) therapy is increasingly used in preterm infants despite a paucity of physiological studies. We aimed to investigate the effects of HFNC on respiratory physiology.

STUDY DESIGN

A prospective randomised crossover study was performed enrolling clinically stable preterm infants receiving either HFNC or nasal continuous positive airway pressure (nCPAP). Infants in three current weight groups were studied: <1000 g, 1000-1500 g and >1500 g. Infants were randomised to either first receive HFNC flows 8-2 L/min and then nCPAP 6 cm H₂O or nCPAP first and then HFNC flows 8-2 L/min. Nasopharyngeal end-expiratory airway pressure (pEEP), tidal volume, dead space washout by nasopharyngeal end-expiratory CO₂ (pEECO₂), oxygen saturation and vital signs were measured.

RESULTS

A total of 44 preterm infants, birth weights 500-1900 g, were studied. Increasing flows from 2 to 8 L/min significantly increased pEEP (mean 2.3-6.1 cm H₂O) and reduced pEECO₂ (mean 2.3%-0.9%). Tidal volume and transcutaneous CO₂ were unchanged. Significant differences were seen between pEEP generated in open and closed mouth states across all HFNC flows (difference 0.6-2.3 cm H₂O). Infants weighing <1000 g received higher pEEP at the same HFNC flow than infants weighing >1000 g. Variability of pEEP generated at HFNC flows of 6-8 L/min was greater than nCPAP (2.4-13.5 vs 3.5-9.9 cm H₂O).

CONCLUSIONS

HFNC therapy produces clinically significant pEEP with large variability at higher flow rates. Highest pressures were observed in infants weighing <1000 g. Flow, weight and mouth position are all important determinants of pressures generated. Reductions in pEECO₂ support HFNC's role in dead space washout.

Ventilator flow data predict bronchopulmonary dysplasia in extremely premature neonates

Early prediction of bronchopulmonary dysplasia (BPD) may facilitate tailored management for neonates at risk. We investigated whether easily accessible flow data from a mechanical ventilator can predict BPD in neonates born extremely premature (EP). In a prospective population-based study of EP-born neonates, flow data were obtained from the ventilator during the first 48 h of life. Data were logged for >10 min and then converted to flow-volume loops using custom-made software. Tidal breathing parameters were calculated and averaged from ≥200 breath cycles, and data were compared between those who later developed moderate/severe and no/mild BPD. Of 33 neonates, 18 developed moderate/severe and 15 no/mild BPD. The groups did not differ in gestational age, surfactant treatment or ventilator settings. The infants who developed moderate/severe BPD had evidence of less airflow obstruction, significantly so for tidal expiratory flow at 50% of tidal expiratory volume (TEF₅₀) expressed as a ratio of peak tidal expiratory flow (PTEF) (p=0.007). A compound model estimated by multiple logistic regression incorporating TEF₅₀/PTEF, birthweight z-score and sex predicted moderate/severe BPD with good accuracy (area under the curve 0.893, 95% CI 0.735-0.973). This study suggests that flow data obtained from ventilators during the first hours of life may predict later BPD in premature neonates. Future and larger studies are needed to validate these findings and to determine their clinical usefulness.

Lung function at term in extremely preterm-born infants: a regional prospective cohort study

OBJECTIVES

To compare lung function of extremely preterm (EP)-born infants with and without bronchopulmonary dysplasia (BPD) with that of healthy term-born infants, and to determine which perinatal characteristics were associated with lung function at term and how predictive these measurements were for later respiratory health in EP-born infants.

METHODS

Perinatal variables were recorded prospectively, and tidal breathing parameters were measured at term-equivalent age using electromagnetic inductance plethysmography. Respiratory morbidity was defined by hospital readmissions and/or treatment with asthma medications during the first year of life.

RESULTS

Fifty-two EP-born infants (mean gestational age 26¹, range 22⁶-27⁶ weeks) and 45 term-born infants were included. There was evidence of significant airway obstruction, higher tidal volumes and increased minute ventilation in the EP-born infants with and without BPD, although generally more pronounced for those with BPD. Male gender, antenatal steroids and number of days on continuous positive airway pressure were associated with lung function outcomes at term. A prediction model incorporating two unrelated tidal breathing parameters, BPD, birth weight z-score and gender, predicted respiratory morbidity in the first year of life with good accuracy (area under the curve 0.818, sensitivity and specificity 81.8% and 75.0%, respectively).

CONCLUSION

Lung function measured at term-equivalent age was strikingly abnormal in EP-born infants, irrespective of BPD. Tidal breathing parameters may be of value in predicting future pulmonary health in infants born premature.

TRIAL REGISTRATION NUMBER

NCT01150396; Results.