The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

OFFICE SPIROMETRY PREDICTS RISK FOR OBESITY HYPOVENTILATION SYNDROME IN PATIENTS WITH SUSPECTED OBSTRUCTIVE SLEEP APNEA.

Deepak Shrivastava, MD; FCCP; Susan Edwards, RCP, CRT; Rodney Felber, DO
Department of Internal medicine, San Joaquin General Hospital, French Camp, CA 

Background:
There is higher incidence of obesity hypoventilation syndrome (OHS) in patients with obstructive sleep apnea (OSA). Restrictive ventilatory impairment, gas exchange abnormalities and pulmonary hypertension are frequently present. Patients with OHS often have poor sleep patterns and excessive daytime sleepiness. OHS may be present independent of OSA. Office spirometry, in addition to other clinical features, identifies high-risk patients for OHS as part of the initial evaluation for suspected OSA.

Methods: Data was prospectively collected during pre-nocturnal polysomnography (NPSG) evaluation. A cohort of 260 patients was followed in the outpatient setting. A total 117 had obesity as defined by a body mass index of 25 kg/m2 or higher. We recorded Epworth sleepiness scores, forced vital capacity (FVC), forced expiratory volume (FEV1) in one second and flow rates. Patients with restrictive physiology were referred for arterial blood gas analysis.

    Male Female Combined 95% Confidence Interval
Restrictive Physiology   30/73 18/44   48/117 = 41% + 9%
High Co2   11/73   6/44 17/117 = 15% + 6%



RESULTS: The gender (men, n=73 and women, n=44) of a patient made no difference in the proportions; all P-values exceeded 99%. Pooled data over gender revealed following confidence intervals for the proportions of obese patients who had restrictive physiology and those who had high pCO2 levels. 

Of those 48 who had a restricted physiology as indicated by office spirometry, seventeen had high pCO2 levels. A 95% confidence interval for this proportion was 35% ± 14. These seventeen patients were diagnosed with OHS.

Conclusions: Significant percent of obese patients with suspected sleep apnea have restrictive ventilatory function. Many of these patients actually have OHS at the time of initial evaluation. Office spirometry can predict high-risk patients for concomitant presence of obesity hypoventilation syndrome. 

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