Chest
Original ResearchSleep MedicineDeterminants of Hypercapnia in Obese Patients With Obstructive Sleep Apnea: A Systematic Review and Metaanalysis of Cohort Studies
Section snippets
Study Selection
We identified all published studies that evaluated the prevalence of chronic daytime hypercapnia (Paco2, ≥ 45 mm Hg) in obese patients with OSA. OSA was defined as an AHI of ≥ 5 events per hour, obesity was defined as a body mass index (BMI) of ≥ 30 kg/m2. Two investigators (R.K. and A.V.H.) conducted independent comprehensive literature searches of Medline from 1966 to July 31, 2008, the Web of Science from 1980 to July 31, 2008, and Scopus from 1960 to July 31, 2008. A first search used text
Study Characteristics
Figure 1 provides details on how an initial search that yielded 314 potential abstracts was reduced to the 15 studies that were included in the metaanalysis (n = 4,250). The number of patients in each study ranged between 30 and 1,227 (Table 1).21, 24 All the studies were published in the last 15 years, with one exception.8 Eleven studies were performed in white populations, and 4 studies7, 21, 24, 25 (n = 1,572; 38% of total sample) were performed in Japanese patients. Most of the studies were
Main Findings
Our metaanalysis confirms that in obese patients without evidence of obstructive airways disease, chronic daytime hypercapnia is associated with the following three factors: the severity of OSA (as measured by AHI or the degree of nocturnal hypoxemia); BMI; and the degree of restrictive chest wall mechanics. More importantly, the severity of OSA and the impairment of respiratory system mechanics are closely associated with the degree of obesity. Specifically, lower FEV1, vital capacity (VC),
Acknowledgments
Author contributions: Drs. Kaw, Hernandez, and Walker contributed to the conception and design of this article. Drs. Hernandez, Kaw, and Walker were responsible for the acquisition of data. Drs. Hernandez, Kaw, Walker, Aboussouan, and Mokhlesi were responsible for the analysis and interpretation of the data. Drs. Kaw, Hernandez, Walker, and Mokhlesi contributed to the drafting of the article. Drs. Hernandez, Kaw, Walker, Aboussouan, and Mokhlesi contributed to the critical revision of the
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