Prevalence of obesity hypoventilation syndrome in ambulatory obese patients attending pathology laboratories.

BACKGROUND AND

OBJECTIVE

The prevalence of obesity hypoventilation syndrome (OHS) in the unselected obese is unknown. Our objectives were: (i) to determine the prevalence of OHS in ambulatory obese patients not previously referred to a pulmonologist for suspicion of sleep breathing disorders and (ii) to assess whether venous bicarbonate concentration [HCO3-v ] can be used to detect OHS.

METHODS

In this prospective multicentric study, we measured [HCO3-v ] in consenting obese patients attending pathology analysis laboratories. Patients with [HCO3-v ] ≥ 27 mmol/L were referred to a pulmonologist for comprehensive sleep and respiratory evaluations. Those with [HCO3-v ] < 27 mmol/L were randomized to either referral to a pulmonologist or ended the study.

RESULTS

For the 1004 screened patients, the [HCO3-v ] was ≥27 mmol/L in 24.6% and <27 mmol/L in 45.9%. A total of 29.5% who had previously consulted a pulmonologist were excluded. A population of 241 obese patients underwent sleep and respiratory assessments. The prevalence of OHS in this population was 1.10 (95% CI = 0.51; 2.27). In multivariate analysis, PaCO2 , forced expiratory volume in 1 s (FEV1 ), apnoea-hypopnoea index (AHI), BMI, use of ≥3 anti-hypertensive drugs, anti-diabetics, proton pump inhibitors and/or paracetamol were related to raised [HCO3-v ].

CONCLUSION

The prevalence of OHS in our obese population was lower than previous estimations based on hospitalized patients or clinical cohorts with sleep breathing disorders. Apart from hypercapnia, increased [HCO3-v ] may also reflect multimorbidity and polypharmacy, which should be taken into account when using [HCO3-v ] to screen for OHS.