Effects of continuous positive airway pressure on diaphragmatic kinetics and breathing pattern in healthy individuals

• Published in: Respirology (Carlton, Vic.) Vol. 21; no. 7; pp. 1262 - 1269
• Main Authors: Soilemezi, Eleni, Koco, Entela, Tsimpos, Christos, Tsagourias, Matthew, Savvidou, Savvoula, Matamis, Dimitris
• Format: Journal Article
• Language: English
• Published: Australia Blackwell Publishing Ltd 01.10.2016
• Subjects: Abdominal Muscles - physiology; Adult; Continuous Positive Airway Pressure; diaphragm; Diaphragm - physiology; Electromyography; Female; Functional Residual Capacity; Humans; hyperinflation; Male; Plethysmography; Positive-Pressure Respiration; Reference Values; Respiratory Function Tests; Respiratory Mechanics - physiology; Respiratory Muscles - physiology; sonography; Tidal Volume - physiology; hyperinflation; diaphragm; continuous positive airway pressure; sonography
• ISSN: 1323-7799; 1440-1843
• DOI: 10.1111/resp.12823

Background and objective In this study, we investigate the changes in diaphragmatic kinetics, breathing pattern and work of breathing induced by 10 cmH2O of continuous positive airway pressure (CPAP). Methods We used sonography to study diaphragmatic kinetics and measured energy expenditure using indirect calorimetry in 50 healthy volunteers at 0 cmH2O positive end expiratory pressure (ZEEP) and after application of 10 cmH2O CPAP. In a subgroup of 14 subjects, the changes in thoracic and abdominal volumes and thoraco‐abdominal asynchrony were recorded with inductive plethysmography, while accessory respiratory muscle activity was recorded with electromyography. Results Continuous positive airway pressure breathing induced acute lung hyperinflation of 600 mL above passive functional residual capacity. This hyperinflation induced changes in diaphragmatic kinetics and breathing pattern; diaphragmatic excursion, thickness and thickness ratio, tidal volume (Vt) and oxygen consumption (VO2) increased while respiratory rate decreased. The increase in Vt with CPAP was mainly due to rib cage contribution. Activation of the accessory inspiratory (scalene) and expiratory (transversus abdominis) muscles was recorded. The raised respiratory muscles workload induced an increase in VO2. Conclusion In healthy volunteers, CPAP therapy leads to lung overdistention and recruitment of respiratory muscles. These mechanisms operate at a high energy cost. We are presenting an integrated picture of the changes in breathing pattern and work of breathing induced by 10 cmH2O of continuous positive airway pressure. This is also the first study looking at diaphragmatic kinetics using M‐mode ultrasound during a setting of acute hyperinflation.