Continuous positive airway pressure and lung inflation in sleep apnea patients.
BACKGROUND
It was shown in normals that an important decrease in upper airway resistance can be obtained with continuous positive airway pressure (CPAP). It was suggested that lung inflation in patients with sleep apnea syndrome (SAS) could also be a mechanism of action of CPAP.


OBJECTIVE
In the present study we wanted to evaluate the effects of nocturnal CPAP on the daytime lung function pattern in patients with SAS.


METHODS
We measured arterial blood gases and possible changes in static lung volumes in 57 SAS patients (37 with normal lung function, 10 with COPD and 10 with restrictive lung disease) after at least one month of CPAP therapy.


RESULTS
A significant increase in PaO(2) (from 79 to 84 mm Hg, p = 0.01) and a decrease in AaDO(2) (from 23 +/- 1 to 16 +/- 1, p < 0.01) was only observed in SAS patients with normal lung function. This improved gas exchange was parallelled by a small but non significant change in the FRC (from 96.5 +/- 3.2 to 105.4 +/- 3.7%pred, p = 0.07) and TLC (from 101.3 +/- 1.7 to 104.1 +/- 1.4%pred, p = 0.15). Similar changes in TLC and FRC were also observed in SAS patients with obstructive and restrictive lung disease.


CONCLUSIONS
Chronic nocturnal CPAP therapy can improve daytime gas exchange and may influence lung inflation during the daytime. The small changes seem to be a functional effect but of no clinical relevance.
Verbraecken
J
J
Department of Pulmonology, University of Maastricht, Maastricht, The Netherlands.
Willemen
M
M
De Cock
W
W
Van de Heyning
P
P
De Backer
W A
WA
D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011659:Pulmonary Gas Exchange; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012891:Sleep Apnea Syndromes / Q000503:physiopathology* / Q000628:therapy*