Determinants of Hypercapnia in Obese Patients With Obstructive Sleep Apnea A Systematic Review and Metaanalysis of Cohort Studies

Department of Hospital Medicine, Medicine Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
Chest (Impact Factor: 7.48). 07/2009; 136(3):787-96. DOI: 10.1378/chest.09-0615
Source: PubMed


Inconsistent information exists about factors associated with daytime hypercapnia in obese patients with obstructive sleep apnea (OSA). We systematically evaluated these factors in this population.
We included studies evaluating the association between clinical and physiologic variables and daytime hypercapnia (Paco(2), >or= 45 mm Hg) in obese patients (body mass index [BMI], >or= 30 kg/m(2)) with OSA (apnea-hypopnea index [AHI], >or= 5) and with a < 15% prevalence of COPD. Two investigators conducted independent literature searches using Medline, Web of Science, and Scopus until July 31, 2008. The association between individual factors and hypercapnia was expressed as the mean difference (MD). Random effects models were used to account for heterogeneity.
Fifteen studies (n = 4,250) fulfilled the selection criteria. Daytime hypercapnia was present in 788 patients (19%). Age and gender were not associated with hypercapnia. Patients with hypercapnia had higher BMI (MD, 3.1 kg/m(2); 95% confidence interval [CI], 1.9 to 4.4) and AHI (MD, 12.5; 95% CI, 6.6 to 18.4) than eucapnic patients. Patients with hypercapnia had lower percent predicted FEV(1) (MD, -11.2; 95% CI, -15.7 to -6.8), lower percent predicted vital capacity (MD, -8.1; 95% CI, -11.3 to -4.9), and lower percent predicted total lung capacity (MD, -6.4; 95% CI, -10.0 to -2.7). FEV(1)/FVC percent predicted was not different between hypercapnic and eucapnic patients (MD, -1.7; 95% CI, -4.1 to 0.8), but mean overnight pulse oximetric saturation was significantly lower in hypercapnic patients (MD, -4.9; 95% CI, -7.0 to -2.7).
In obese patients with OSA and mostly without COPD, daytime hypercapnia was associated with severity of OSA, higher BMI levels, and degree of restrictive chest wall mechanics. A high index of suspicion should be maintained in patients with these factors, as early recognition and appropriate treatment can improve outcomes.

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    • "It is known that OHS and OSAS are often associated and the majority of patients with OHS have severe OSAS.[13] However, due to the methodological design of our study, the rate of OSAS could not be determined. "
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    ABSTRACT: Patients with obesity hypoventilation syndrome (OHS) have significant morbidity and mortality. Early diagnosis and treatment is important and there are limited data on its prevalence and predictive factors. The objective of this observational study was to determine the frequency and predictors of OHS in hospitalized patients at a tertiary health care institution. All blood gas analyses of hospitalized adult (age over 18 years) patients were prospectively recruited from the biochemistry laboratory at a tertiary health care center between August 2009 and July 2010. Patients who had hypercapnia (PaCO2 ≥ 45 mmHg) while breathing room air were included and clinical and laboratory data were obtained from hospital records. A standard questionnaire was also filled by face-to-face interview with patients and/or relatives. A total of 9480 patients' arterial blood gases were evaluated and 330 patients (3.4%) who met the selection criteria were included in the analysis during the study period. Hypoventilation was associated with acute diseases in 64.2% and chronic diseases in 35.8% of the patients. Of the chronic hypoventilation patients, 24.4% had OHS. Univariate logistic regression analysis showed that, female gender, body mass index (BMI), smoking, PaO2, SaO2 and a PaCO2/BMI <1.5 were significantly related to OHS. In multivariate logistic regression analysis, BMI >35 kg/m(2), SaO2 <91.4% and PaCO2 /BMI <1.5 were significantly related to OHS. A PaCO2/BMI <1.5 was an independent variable strongly predictive of OHS (odds ratio: 36.9, 95% of the confidence interval: 2.75-492.95, P = 0.007). OHS is a common cause of chronic alveolar hypoventilation. A careful examination PaCO2 /BMI ratio may prevent misdiagnoses among hypercapnic patients.
    No preview · Article · Mar 2014 · Annals of Thoracic Medicine
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    • "The prevalence of obesity hypoventilation syndrome (OHS) is also rising with the obesity epidemic and it is important for anesthesiologists to recognize and manage these patients perioperatively. A recent meta-analysis of a cohort of more than 4000 patients with OSA reported a 19% prevalence of OHS confirming an overall prevalence of approximately 3 per 1000 [31]. Among OSA patients the prevalence of OHS is reported as 11% and about 90% of patients with OHS have OSA [32]. "
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    ABSTRACT: Modern surgery is faced with the emergence of newer "risk factors" and the challenges associated with identifying and managing these risks in the perioperative period. Obstructive sleep apnea and obesity hypoventilation syndrome pose unique challenges in the perioperative setting. Recent studies have identified some of the specific risks arising from caring for such patients in the surgical setting. While all possible postoperative complications are not yet fully established or understood, the prevention and management of these complications pose even greater challenges. Pulmonary hypertension with its changing epidemiology and novel management strategies is another new disease for the surgeon and the anesthesiologist in the noncardiac surgical setting. Traditionally most such patients were not considered surgical candidates for any required elective surgery. Our review discusses these disease entities which are often undiagnosed before elective noncardiac surgery.
    Full-text · Article · Jan 2014 · The Scientific World Journal
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    • "The incidence of OHS increases significantly as obesity increases, with a reported prevalence of around 10 to 20% in outpatients presenting to sleep clinics [54,93-95] to almost 50% of hospitalized patients with a BMI greater than 50 kg/m2[96]. Current estimates suggest that around 0.15 to 0.4% of the population may have OHS [97,98]. "
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    ABSTRACT: The overlap syndrome of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD), in addition to obesity hypoventilation syndrome, represents growing health concerns, owing to the worldwide COPD and obesity epidemics and related co-morbidities. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to a considerable health burden. The coexistence OSA and COPD seems to occur by chance, but the combination can contribute to worsened symptoms and oxygen desaturation at night, leading to disrupted sleep architecture and decreased sleep quality. Alveolar hypoventilation, ventilation-perfusion mismatch and intermittent hypercapnic events resulting from apneas and hypopneas contribute to the final clinical picture, which is quite different from the “usual” COPD. Obesity hypoventilation has emerged as a relatively common cause of chronic hypercapnic respiratory failure. Its pathophysiology results from complex interactions, among which are respiratory mechanics, ventilatory control, sleep-disordered breathing and neurohormonal disturbances, such as leptin resistance, each of which contributes to varying degrees in individual patients to the development of obesity hypoventilation. This respiratory embarrassment takes place when compensatory mechanisms like increased drive cannot be maintained or become overwhelmed. Although a unifying concept for the pathogenesis of both disorders is lacking, it seems that these patients are in a vicious cycle. This review outlines the major pathophysiological mechanisms believed to contribute to the development of these specific clinical entities. Knowledge of shared mechanisms in the overlap syndrome and obesity hypoventilation may help to identify these patients and guide therapy.
    Full-text · Article · Nov 2013 · Respiratory research
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