Mask Continuous Positive Airway Pressure Increases Diaphragm Thickening Fraction in Healthy Subjects

Abstract

<b><i>Introduction:</i></b> The most widespread treatment for obstructive sleep apnoea and obesity hypoventilation syndrome is continuous positive airway pressure (CPAP). The addition of inspiratory support is a potential alternative. This is a physiological study to determine the effect of CPAP and inspiratory support pressure on respiratory effort measured by diaphragm thickening fraction (DTF) in healthy volunteers. <b><i>Methods:</i></b> DTF was measured in spontaneously breathing, healthy volunteers during 4 phases: (I) without connection to a ventilator, (II) on a ventilator without any applied pressures, (III) with a CPAP of 5 cmH₂O, and (IV) with an additional inspiratory support pressure of 5 cmH₂O. <b><i>Results:</i></b> Twenty-nine individuals agreed to participate. DTF was similar during the first two phases (32 ± 13% and 35 ± 22%). A considerable increase in DTF to 51 ± 21% was noted in phase III. The introduction of inspiratory support pressure during phase IV led to a reduction in DTF back to 36 ± 23% (<i>p</i> &lt; 0.001). Tidal volume and minute ventilation were both slightly higher in phase IV compared to phase III. <b><i>Conclusion:</i></b> CPAP without inspiratory support pressure increases respiratory effort measured by DTF in healthy subjects. Further research is required to investigate this phenomenon in a clinical setting.