Am. J. Respir. Crit. Care Med., Vol 152, No. 5, 11 1995, 1620-1626.
Influence of sleep on ventilatory and upper airway response to CO2 in normal subjects and patients with COPD
JC Meurice, I Marc and F Series
Unite de recherche, Hopital Laval, Universite Laval, Quebec, Montreal, Canada.
In order to investigate the influence of the dynamic changes in upper
airway (UA) resistance in the pathophysiology of noctural hypoventilation
in COPD, we compared the ventilatory pattern and UA resistance, measured at
baseline and during CO2 rebreathing, in nine normal men and 13 patients
with COPD. Measurements were made during wakefulness and during non-REM
sleep during a morning nap after a sleep deprivation night. Ventilatory
parameters (VE, VT, VT/TI) were calculated from flow measurements using a
Fleich no. 3 pneumotachograph connected to a fitting nasal mask. Pharyngeal
pressure was measured with a low-bias catheter referenced to the mask
pressure. Baseline UA resistances (supraglottic resistance: SGR) values
were similar in the two groups. They significantly increased in both groups
from wakefulness to sleep. Furthermore, VE and VT/TI were higher in
patients with COPD than in normal subjects during wakefulness and during
sleep. The slope of the VE/PETCO2 relationship was significantly lower in
patients with COPD than in normal subjects (p = 0.0001), without any
significant decrease between wakefulness and sleep. SGR systematically
decreased during CO2 rebreathing in both groups during wakefulness and
during sleep. The slope of SGR/PETCO2 relationship was lower in patients
with COPD than in control subjects during sleep and during wakefulness (p =
0.005), whereas the decrease in SGR with increased VE and VT/TI was similar
in both groups 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.
