INFLUENCE OF SLEEP ON VENTILATORY AND UPPER AIRWAY RESPONSE TO CO2 INNORMAL SUBJECTS AND PATIENTS WITH COPD

In order to investigate the influence of the dynamic changes in upper airway (UA) resistance in the pathophysiology of noctural hypoventilat ion in COPD, we compared the ventilatory pattern and UA resistance, me asured at baseline and during CO2 rebreathing, in nine normal men and 13 patients with COPD. Measurements were made during wakefulness and d uring non-REM sleep during a morning nap after a sleep deprivation nig ht. Ventilatory parameters (VE, VT, VT/TI) were calculated from flow m easurements using a Fleich no. 3 pneumotachograph connected to a fitti ng nasal mask. Pharyngeal pressure was measured with a low-bias cathet er referenced to the mask pressure. Baseline UA resistances (supraglot tic resistance: SCR) values were similar in the two groups. They signi ficantly increased in both groups from wakefulness to sleep. Furthermo re, VE and VT/TI were higher in patients with COPD than in normal subj ects during wakefulness and during sleep. The slope of the VE/PETCO(2) relationship was significantly lower in patients with COPD than in no rmal subjects (p = 0.0001), without any significant decrease between w akefulness and sleep. SGR systematically decreased during CO2 rebreath ing in both groups during wakefulness and during sleep. The slope of S GR/PETCO(2) relationship was lower in patients with COPD than in contr ol subjects during sleep and during wakefulness (p = 0.005), whereas t he decrease in SCR with increased VE and VT/TI was similar in both gro ups and not influenced by sleep. We conclude that the impediment in UA resistance behavior in response to a hypercapnic stimulus in patients with COPD is related to the decrease in their ventilatory response.