Clinicaltrials.gov: NCT01130948.

Background: Previous studies with small sample sizes reported contradicting findings as to whether pulmonary function tests can predict exercise-induced oxygen desaturation (EID). Objective: To evaluate whether forced expiratory volume in one second (FEV₁), resting oxygen saturation (Spo₂) and diffusion capacity for carbon monoxide (Dlco) are predictors of EID in chronic obstructive pulmonary disease (COPD). Methods: We measured FEV₁, Dlco, Spo₂ at rest and during a 6-min walking test as well as physical activity by an accelerometer. A drop in Spo₂ of >4 to <90% was defined as EID. To evaluate associations between measures of lung function and EID univariate and multivariate analyses were used and positive/negative predictive values were calculated. Receiver operating characteristic curve analysis was performed to determine the most useful threshold in order to predict/exclude EID. Results: We included 154 patients with COPD (87 females). The mean FEV₁ was 43.0% (19.2) predicted and the prevalence of EID was 61.7%. The only independent predictor of EID was FEV₁ and the optimal cutoff value of FEV₁ was at 50% predicted (area under ROC curve, 0.85; p < 0.001). The positive predictive value of a threshold of FEV₁ <50% was 0.83 with a likelihood ratio of 3.03 and the negative predicting value of a threshold of FEV₁ ≥80% was 1.0. The severity of EID was correlated with daily physical activity (r = –0.31, p = 0.008). Conclusions: EID is highly prevalent among patients with COPD and can be predicted by FEV₁. EID seems to be associated with impaired daily physical activity which supports its clinical importance.

Preliminary evidence supports an association between OSA and cardiac dysrhythmias. Negative intrathoracic pressure, as occurring during OSA, may provoke cardiac dysrhythmias. Thus, we aimed to study the acute effects of simulated apnea and hypopnea on arrhythmic potential and measures of cardiac repolarization [QT(C) and T (peak) to T (end) intervals [TpTec]) in humans. In 41 healthy volunteers, ECG was continuously recorded prior, during and after simulated obstructive hypopnea (inspiration through a threshold load), simulated apnea (Mueller maneuver), end-expiratory central apnea and normal breathing in randomized order. The number of subjects with premature beats was significantly higher during inspiration through a threshold load (n = 7), and the Mueller maneuver (n = 7) compared to normal breathing (n = 0) (p = 0.008 for all comparisons), but not during end-expiratory central apnea (n = 3, p = 0.125). Inspiration through a threshold load was associated with a non-significant mean (SD) increase of the QT(C) interval [+5.4 (22.4) ms, 95 %CI -1.7 to +12.4 ms, p = 0.168] and a significant increase of the TpTcc interval [+3.7 (8.9) ms, 95 %CI +0.9 to +6.6 ms, p = 0.010]. The Mueller maneuver induced a significant increase of the QT(C) interval [+8.3 (23.4) ms, 95 %CI 0.9 to +15.6 ms, p = 0.035] and the TpTec interval (+4.2 (8.2) ms, 95 %CI +1.6 to +6.8 ms, p = 0.002). There were no significant changes of the QT(C) and TpTec intervals during central end-expiratory apnea. These data indicate that simulated obstructive apnea and hypopnea are associated with an increase of premature beats and prolongation of QT(C) and TpTec intervals. Therefore, negative intrathoracic pressure changes may be a contributory mechanism for the association between OSA and cardiac dysrhythmias.

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BackgroundTravel to mountain areas is popular. However, the effects of acute exposure to moderate altitude on the cardiovascular system and metabolism are largely unknown.ObjectivesTo investigate the effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation.MethodsIn 51 healthy male subjects with a mean (SD) age of 26.9 (9.3) years, oxygen saturation, blood pressure, heart rate, arterial stiffness, lipid profiles, low density lipoprotein (LDL) particle size, insulin resistance (HOMA-index), highly-sensitive C-reactive protein and pro-inflammatory cytokines were measured at 490 m (Zurich) and during two days at 2590 m, (Davos Jakobshorn, Switzerland) in randomized order. The largest differences in outcomes between the two altitudes are reported.ResultsMean (SD) oxygen saturation was significantly lower at 2590 m, 91.0 (2.0)%, compared to 490 m, 96.0 (1.0)%, p<0.001. Mean blood pressure (mean difference +4.8 mmHg, p<0.001) and heart rate (mean difference +3.3 bpm, p<0.001) were significantly higher at 2590 m, compared to 490 m, but this was not associated with increased arterial stiffness. At 2590 m, lipid profiles improved (median difference triglycerides −0.14 mmol/l, p = 0.012, HDL +0.08 mmol/l, p<0.001, total cholesterol/HDL-ratio −0.25, p = 0.001), LDL particle size increased (median difference +0.45 nm, p = 0.048) and hsCRP decreased (median difference −0.18 mg/l, p = 0.024) compared to 490 m. No significant change in pro-inflammatory cytokines or insulin resistance was observed upon ascent to 2590 m.ConclusionsShort-term stay at moderate altitude is associated with increased blood pressure and heart rate likely due to augmented sympathetic activity. Exposure to moderate altitude improves the lipid profile and systemic inflammation, but seems to have no significant effect on glucose metabolism.Trial RegistrationClinicalTrials.gov NCT01130948