Elsevier

Respiratory Medicine

Volume 95, Issue 8, August 2001, Pages 693-696
Respiratory Medicine

Short Report
Prevalence of daytime hypercapnia or hypoxia in patients with OSAS and normal lung function

https://doi.org/10.1053/rmed.2001.1120Get rights and content
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Abstract

The purpose of this study was to determine factors increasing daytime P aCO2orP aO2in obstructive sleep apnoea syndrome patients (OSAS) with normal pulmonary function tests. Anthropometric, pulmonary function tests, arterial blood gases and sleep polygraphic data were analysed retrospectively in 218 OSAS patients (apnoea–hypopnoea index >15 h−1; 18 females, 55±11 years): 125 patients had abnormal pulmonary function tests, i.e. one or more flow or volume under 80% or above 120% of predictive value (group I) and 93 had normal pulmonary function tests (group II). Hypercapnia was defined as P aCO2≥6·0 kPa and hypoxia asP aO2<9·3 kPa. Patients with abnormal pulmonary function tests were more hypoxic and hypercapnic, more obese, and had a higher apnoea–hypopnoea index (P<0·05). Seventeen patients of group I and four of group II were hypercapnic (13·6% and 4·3%, respectively ). Thirty-one patients in group I (24·8%) had a P aO2<9·3 kPa and six (6·5%) in group II. Stepwise multiple regression analysis showed that in group II, only two factors were correlated with P aCO2: mean apnoea duration and FRC (respectively: c=0·228, P<0·001;c=0·006,P =0·0108); and only two with P aO2: mean apnoea duration: (c=−0·218, P=0·029) and BMI (c=−3·72,P <0·0001). Daytime hypercapnia is present in 4·3% and daytime hypoxia in 6·5% of patients with occlusive sleep apnoea syndrome and normal pulmonary function tests. These alterations in blood gases in OSAS with normal pulmonary function tests should be considered as OSAS severity criteria.

Keywords

sleep apnoea syndrome
pulmonary function tests
apnoea index
apnoea duration
hypercapnia
hypoxia.

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Correspondence should be addressed to: Dr E. Verin, Service de Physiologie Respiratoire, Hôpital de Bois Guillaume, CHU de Rouen, 1 rue de Germont, 76031 Rouen Cedex, France. Fax: (33) 232 889 139; E-mail: [email protected]