CONTINUOUS VERSUS BILEVEL POSITIVE AIRWAY PRESSURE IN A PATIENT WITH IDIOPATHIC CENTRAL SLEEP-APNEA

A 57-yr-old mast with idiopathic central apnea is reported. He present ed at our hospital complaining of excessive daytime sleepiness. Polyso mnography, including esophageal pressure monitoring, confirmed central sleep apnea with are apnea index of 27/h. He had mild non-insulin-dep endent diabetes mellitus (NIDDM) but no signs of diabetic neuropathy o r other background diseases. The ventilatory responses to hypoxia and hypercapnia tested while he was awake indicated increased respiratory chemosensitivity. We applied nasal continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BPAP) in an attempt to c ompare the possible difference in therapeutic efficacy. Although nasal CPAP completely reversed central apnea, nasal BPAP adversely affected both apnea length and frequency in an applied pressure-dependent mann er. Arterial blood gas analyses while he was being treated indicted al veolar hypoventilation with CPAP and hyperventilation with BPAP. Addit ionally, administration of a mixed gas containing 5% CO2 through a fac e mask had a significant effect on the disappearance of central apnea in this patient, These findings support the theory that the arterial P CO2 level is critical in generating idiopathic central apnea and that nasal CPAP therapy may be effective in eliminating central apnea lay r aising the PaCO2.