title: Predictors for nocturnal hypoxaemia (mean SaO2 < 90%) in normoxic and mildly hypoxic patients with COPD.
abstract: Detection of nocturnal hypoxaemia, defined as a mean arterial oxygen saturation below 90%, in normoxic or mildly hypoxic chronic obstructive pulmonary disease (COPD) patients seems clinically relevant, since this feature may precede pulmonary hypertension. Nocturnal studies are expensive and time-consuming procedures. The current study investigates to what extent it is possible to predict nocturnal hypoxaemia from daytime parameters. Forty two COPD patients with a daytime arterial oxygen tension (PaO2) above 8 kPa participated. Nocturnal oxygenation, daytime blood gas values, and ventilatory responses to hypercapnia were measured. In 10 patients, enough desaturations occurred to qualify as nocturnal hypoxaemia. They had a significantly lower daytime PaO2 value, and a lower steady-state hypercapnic ventilatory response. They also smoked more often, and complained about daytime sleepiness. Multiple linear regression analysis demonstrated that daytime PaO2 (32%) was the best independent predictor. Sleepiness (12%), and number of cigarettes smoked (5%) also contributed independently, but in a minor way. Patients with a high daytime PaO2 (> 11 kPa) did not develop nocturnal hypoxaemia. The hypercapnic ventilatory response was used to distinguish nocturnal hypoxaemic from normoxaemic patients. Only patients with a low response (< 3.5 l.min-1.kPa-1) appeared to run a risk of developing nocturnal hypoxaemia. The sensitivity of this test was 80%, and the specificity 70%. It is concluded that daytime PaO2, hypercapnic ventilatory response and sleepiness are helpful in predicting nocturnal hypoxaemia.
authors.affiliation: Dept of Pulmonary Diseases, University of Nijmegen, Groesbeek, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Vos
authors.forename: H T
authors.initials: HT
authors.lastname: Folgering
authors.forename: C L
authors.initials: CL
authors.lastname: van Herwaarden
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D008297:Male; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D012890:Sleep; D012907:Smoking / Q000009:adverse effects
chemical_list: D010100:Oxygen