Chest
Volume 131, Issue 6, June 2007, Pages 1678-1684
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ORIGINAL RESEARCH
SLEEP MEDICINE
Obesity Hypoventilation Syndrome: Hypoxemia During Continuous Positive Airway Pressure

https://doi.org/10.1378/chest.06-2447Get rights and content

Background

Polysomnography findings between matched groups with obstructive sleep apnea (OSA) and OSA plus obesity-hypoventilation syndrome (OHS) before and after continuous positive airway pressure (CPAP), particularly in the extremely severe obese (body mass index [BMI] ≥ 50 kg/m2), are unclear.

Design

Prospective study of subjects (BMI ≥ 50 kg/m2) undergoing diagnostic polysomnography. Subjects with an apnea-hypopnea index (AHI) ≥ 15/h underwent a second polysomnography with CPAP. The effect of 1 night of CPAP on sleep architecture, AHI, arousal indexes, and nocturnal oxygenation was assessed. OHS was defined as those subjects with obesity, Paco2 > 45 mm Hg, and Pao2 < 70 mm Hg in the absence of lung disease.

Results

Twenty-three subjects with moderate-to-severe OSA and 23 subjects with moderate-to-severe OSA plus OHS underwent a 1-night trial of CPAP. Both groups were matched for spirometry, BMI, and AHI, but oxygen desaturation was worse in the OSA-plus-OHS group. CPAP significantly improved rapid eye movement (REM) duration (p < 0.005), AHI (p < 0.005), arousal indexes (p < 0.005), and percentage of total sleep time (TST) with oxygen saturation (Spo2) < 90% (p < 0.005) in both groups. In subjects with OSA plus OHS, 43% continued to spend > 20% of TST with Spo2 < 90%, compared to 9% of the OSA group, despite the adequate relief of upper airway obstruction.

Conclusions

Extremely severe obese subjects (BMI ≥ 50 kg/m2) with moderate-to-severe OSA plus OHS exhibit severe oxygen desaturation but similar severities of AHI, arousal indexes, and sleep architecture abnormalities when compared to matched subjects without OHS. CPAP significantly improves AHI, REM duration, arousal indexes, and nocturnal oxygen desaturation. Some subjects with OHS continued to have nocturnal desaturation despite the control of upper airway obstruction; other mechanisms may contribute. Further long-term studies assessing the comparative role of CPAP and bilevel ventilatory support in such subjects with OHS is warranted.

Section snippets

Subjects

A prospective study was undertaken of all subjects with extremely severe obesity (BMI ≥ 50 kg/m2) consecutively presenting to and undergoing diagnostic overnight polysomnography at the Royal Prince Alfred Hospital, Sydney, between August 2001 and January 2004. All subjects were referred to the unit for the investigation of possible sleep-disordered breathing. Any subject with a history or clinical examination suggestive of neuromuscular disease, chest wall disease (eg, kyphoscoliosis or polio),

Sleep Study Population and Recordings

Eighty subjects (34 men) with a BMI ≥ 50 kg/m2 presented to the sleep-disordered breathing clinic. All patients underwent polysomnography. Mild OSA (AHI, 5 to 14.9/h) was demonstrated in 10 subjects, moderate OSA (AHI, 15 to 29.9/h) was demonstrated in 14 subjects, and severe OSA (AHI > 30/h) was demonstrated in 50 subjects. All subjects had > 80% obstructive or mixed apneas and hypopneas. Six (7.5%) subjects did not demonstrate OSA (ie, an AHI < 5/h).

Exclusions

The 10 subjects with mild OSA were excluded

Discussion

The present study has shown that 1 night of CPAP therapy improves upper airway obstruction, arousal indexes, sleep architecture, and nocturnal oxygen desaturation in subjects with extremely severe obesity (BMI > 50 kg/m2) and moderate-to-severe OSA, with or without OHS. However, the response of nocturnal oxygen desaturation to CPAP was strikingly different in those with OSA and OHS, despite adequately treating the apneas and hypopneas, with 43% of these subjects continuing to desaturate with Spo

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The authors have no conflicts of interest to declare.

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