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

Abstract

Background and objective: In this study, we investigate the changes in diaphragmatic kinetics, breathing pattern and work of breathing induced by 10 cmH 2 O 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 cmH 2 O positive end expiratory pressure (ZEEP) and after application of 10 cmH 2 O 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.

Evaluation of a New Interface Combining High-Flow Nasal Cannula and CPAP

“…In healthy individuals, CPAP induces hyperinflation, which affects the length of diaphragm fibers and muscle kinetics. [23][24][25] In keeping with the results of a previous study, 23 we observed increments of 25% and 45% for thickness at end-expiration and thickness at end-inspiration, respectively, after application of CPAP 10 cm H 2 O. Further increments of both thickness at end-expiration and thickness at end-inspiration compared with CPAP were observed with CPAP ϩ HFNC 40 L/min and 50 L/min, although not 30 L/min.…”

“…In healthy volunteers unaware of the study purposes, we found that adding HFNC to CPAP (compared to CPAP) (1) did not importantly alter either the preset airway pres- 14 (12)(13)(14)(15)(16)(17)(18)(19) 19 (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) 21 (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28) .01 †; .001* ‡; .001* § 21 (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28) 21 (18)(19)(20)(21)…”

“…The median (interquartile range) temperature assessed inside the interface during CPAP (27 [27][28] [23][24][25]°C) (P Ͻ .001 for all comparisons). The addition of heated humidified flow through the nasal cannula slightly, although significantly, increased the temperature only at CPAP ϩ HFNC 50 L/min compared with CPAP (P ϭ .004).…”

Stable Breathing in Patients With Obstructive Sleep Apnea Is Associated With Increased Effort but Not Lowered Metabolic Rate

“…However, our use of CPAP to improve airflow obstruction was interventional in nature and thus a causal influence of CPAP via relief of airflow obstruction on respiratory parameters may be inferred. It is possible that CPAP has influences on metabolic rate other than via the upper airway: For example, in controls during wakefulness, CPAP can activate accessory respiratory muscles and may increase work of breathing 62 ; while we did not seek to quantify expiratory work of breathing, our finding that respiratory effort is reduced suggests that a CPAP-induced increase in work of breathing during sleep in patients with sleep apnea is extremely unlikely. The finding of increased VO 2 on CPAP relies on the observed increase in ventilation with CPAP in conjunction with the relative constancy of PO 2 levels.…”

Role of Diaphragm Ultrasound When NIV Fails in COPD Exacerbations

“…In healthy subjects, acute hyperinflation achieved through the application of CPAP does not decrease but, instead, increases diaphragmatic excursions. 4 Diaphragmatic excursions in clinically stable hyperinflated patients with COPD and in healthy subjects are similar. 5,6 If not hyperinflation, what else could have reduced diaphragmatic excursions?…”