Search

BACKGROUND: Postural changes are known to affect normal lung volumes. A reduction in sitting to supine functional residual capacity (FRC) is well-described in non-obese subjects adopting a supine position. However, postural changes in lung volumes in the obese require further exploration. We aimed to longitudinally address the effects of weight loss on postural changes in lung volumes and pulmonary function in obese subjects. We tested the hypothesis that supine reduction in FRC would be absent in morbid obesity and recovered upon weight loss. METHODS: This was a prospective, observational, longitudinal study. Consecutive morbidly obese adults (N = 12, age: 44 ± 14 y, body mass index: 45 ± 5 kg/m2) enrolled in a bariatric surgery program were included. Standard pulmonary function tests and blood gas analysis were performed both before and 1 y after surgery. Pulmonary function was assessed in both the sitting and supine position using spirometry and multi-breath helium dilution. Parameters recorded before and after weight loss were compared. The main outcome measure was FRC. RESULTS: Ten subjects were retested 1 y after surgery (body mass index: 31 ± 5 kg/m2). FRC was not affected by change in posture before surgery. Supine reduction in FRC was observed after weight loss (ΔFRC: −0.6 ± 0.4 L, sitting vs supine, P = .002). Pulmonary gas exchange improved (alveolar-to-arterial oxygen partial pressure difference: −8 ± 11 mm Hg, P = .035). CONCLUSIONS: Although postural change in FRC is absent when the morbidly obese adopt a supine position, supine reduction in FRC can be recovered following gastroplasty-induced weight loss, despite residual mild to moderate obesity. This also shows that mild to moderate obesity may affect supine FRC more than morbid obesity. (ClinicalTrials.gov registration NCT02207192.)

BACKGROUND: The RAD-57 pulse CO-oximeter is a lightweight device allowing noninvasive measurement of blood carboxyhemoglobin (SpCO). We assessed the diagnostic value of pulse CO-oximetry, comparing SpCO values from the RAD-57 to standard laboratory blood carboxyhemoglobin (COHb) measurement in emergency department patients with suspected carbon monoxide (CO) poisoning. METHODS: This was a prospective, diagnostic accuracy study according to the Standards for the Reporting of Diagnostic Accuracy Studies criteria in consecutive adult emergency department patients with suspected CO poisoning. SpCO was measured with the RAD-57 simultaneously with blood sampling for laboratory blood gas analysis. We made no changes to our standard management of CO poisoning. Blood COHb > 5% for non-smokers, and > 10% for smokers were applied as the reference standard. RESULTS: We included 93 subjects: 37 smokers and 56 non-smokers. CO poisoning was diagnosed in 26 subjects (28%). The SpCO values ranged from 1% to 30%, with a median of 4% (IQR 2.7–7.3%). The COHb values ranged from 0% to 34%, with a median of 5% (IQR 2–9%). The mean differences between the COHb and SpCO values were −0.2% ± 3.3% (95% limits of agreement of −6.7% and 6.3%) for the whole cohort, −0.7% (limits of agreement −7.7% and 6.2%) for the non-smokers, and 0.6% (limits of agreement −5.0% and 6.2%) for the smokers. The optimal thresholds for detecting CO poisoning were SpCO of 9% and 6% for smokers and non-smokers, respectively. CONCLUSIONS: SpCO measured with the RAD-57 was not a substitute for standard blood COHb measurement. However, noninvasive pulse CO-oximetry could be useful as a first-line screening test, enabling rapid detection and management of CO-poisoned patients in the emergency department.