Inhibition of ventilatory motor output increases expiratory retro palatal compliance during sleep

We hypothesized that inhibition of ventilatory motor output leads to increased pharyngeal compliance during NREM sleep, independent of lung volume.MethodsEighteen subjects were studied using noninvasive positive pressure ventilation (NPPV) to inhibit ventilatory motor output during stable NREM sleep. Nasopharyngoscopy was used to measure the retro palatal cross-sectional area/pressure relationship (CSA/Pph) in 8 subjects. The effect of NPPV on neck circumference (NC) and end-expiratory lung volumes (EELV) was studied in 10 additional subjects using strain gauge plethysmography and respitrace, respectively.Results(1) The CSA/Pph was increased during expiration under passive compared to active breathing (11.7 ± 7.1 vs. 8.5 ± 5.6 mm2/cmH2O, respectively; p < 0.05) but not during inspiration. (2) NC correlated with the CSA/Pph during passive expiration (R2 = 0.77, p < 0.05). (3) NC and EELV did not change between active and passive breaths (p = NS).Conclusions(1) Inhibiting the ventilatory motor output increases the pharyngeal compliance. (2) Increased passive expiratory pharyngeal compliance was not associated with changes in NC or EELV.