Correlates of obesity-related chronic ventilatory failure

Journal article

"Take home" message: It remains unclear why only some obese patients develop hypoventilation syndrome. In the largest cross-sectional study to date, exploring a wide range of potential factors provoking the obesity hypoventilation syndrome, we have found that intra-abdominal obesity and a poor response to hypoxia appear to be the dominant factors associated with hypoventilation, thus providing further insights into the pathophysiology of this condition.

The question addressed by the study: Only a third of obese patients develop chronic ventilatory failure. This cross-sectional study assessed multiple factors potentially associated with chronic ventilatory failure.

Materials/Patients and Methods: Subjects had a body mass index (BMI) greater than 30 kg/m2, with or without chronic ventilatory failure (awake PaCO2 greater than 6kPa or base excess (BE) ≥2mmols/l). Factors investigated were grouped into domains: (1) obesity measures, (2) pulmonary function, (3) respiratory and non-respiratory muscle strength, (4) sleep study derivatives, (5) hypoxic and hypercapnic responses, and (6) some hormonal, nutritional and inflammatory measures.

Results: Seventy-one obese subjects (52% male) were studied over 27 months, 52 (SD 9) years and BMI 47 (range, 32 – 74) kg/m2. The best univariate correlates of BE from each domain were: (1) dual energy X-ray absorptiometry measurement of visceral fat (r=+0.50, p=0.001); (2) supine FEV1 (r=-0.40, p=0.001); (3) sniff maximum pressure (r=-0.28, p=0.02); (4) mean overnight oxygen saturation (SpO2) (r= 0.50, p<0.001); (5) ventilatory response to 15% O2 breathing ( r=-0.28, p=0.02) and; (6) vitamin D (r=-0.30, p=0.01). In multivariate analysis only visceral fat and ventilatory response to hypoxia remained significant.

Answer to the question: We have confirmed that in the obese, BMI is a poor correlate of chronic ventilatory failure, and the best independent correlates are visceral fat and hypoxic ventilatory response.

Authors: Stradling, J; Manuel, A; Hart, N

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: BMJ Publishing Group
• Journal: BMJ Open Respiratory Research
• Volume: 3
• Issue: 1
• Article number: e000110
• Publication date: 2016-02-01
• DOI: 10.1136/bmjresp-2015-000110
• ISSN: 2052-4439
• Keywords: Obesity; Hypoventilation; Hypercapnia