Neural Respiratory Drive In Patients With Obstructive Sleep Apne

Part 1 Varibility of Neural Respiratory Drive in Patients with Obstructive Sleep ApneaObjectiveTo evaluate the role of varibility of neural respiratory drive in the pathophysiology of obstructive sleep apnea (OSA).Methods13 patients with OSA were studied. Neural respiratory drive was assessed by diaphragm electromyogram (EMGdi) recorded from a multipair esophageal electrode during wakefulness, sleep and treatment with continuous positive air pressure (CPAP) during overnight polysomnography (PSG).ResultsCoefficient of variation of the EMG(CV-EMG) during sleep (29.1%±7.5%) and apnea events(40.7%±12.0%) was higher than that (14.7%±1.9%) during wakefulness(p﹤0.001). However, there was no difference in the CV-EMG during treatment with CPAP and wakefulness (15.4%±4.6% vs. 14.7%±1.9%,p﹥0.05).Conclusionvariability of neural respiratory drive in patients with OSA during sleep or apnea event was higher than that during wakefulness. CPAP could eliminate apnea events and reduce variability of neural respiratory drive during sleep in patients with OSA.Part 2 Neural Respiratory Drive during Continuous Positive Airway Pressure(CPAP) and pressure relief CPAP(c-flex)BackgroundPressure release continuous positive airway pressure (CPAP) is an evolution of CPAP that has been reported to improve patient comfort. We hypothesised the pressure release would lead to unloading of the inspiratory muscles and therefore conducted a prospective double-blind cross-over physiological study of autotitrating CPAP (APAP) against autotitrating pressure relief CPAP (PR-APAP).MethodsEleven patients with severe obstructive sleep apnoea (OSA; mean AHI 74.5±14.4/h) were studied. We assessed neural drive by recording the oesophageal pressure, gastric pressure, transdiaphragmatic pressure and the diaphragm EMG during overnight polysomnography. ResultsBoth APAP and PR-APAP significantly reduced neural respiratory drive. Transdiaphragmatic pressure swings during apnoea (30.2±11.5 cm H2O) before treatment decreased to 9.1±5.3 cm H2O for PRAPAP and 8.5±3.7 cm H2O for APAP. The transdiaphragmatic pressure and the diaphragm EMG did not differ significantly between APAP and PR-APAP. The gastric pressure swing at expiration phase disappeared during both APAP and PR-APAP when sleep respiratory events were eliminated.ConclusionsPR-APAP is not superior to APAP in terms of reducing neural respiratory drive. It is unnecessary to replace conventional APAP with PR-APAP for patients who have been successfully treated with traditional APAP.