How to treat patients with obstructive sleep apnea syndrome during an altitude sojourn

Considering the high prevalence of the obstructive sleep apnea syndrome (OSA), it is expected that many patients with the disorder are traveling to altitude. However, this may expose them to the risk of pronounced hypoxemia, exacerbation of nocturnal breathing disturbances by frequent central apneas, impaired daytime performance, and high blood pressure. Recently, randomized studies specifically investigated the effects of altitude (1630-2590 m) in OSA patients and the optimal treatment in this setting. The results indicate that patients should continue to use continuous positive airway pressure therapy (CPAP) when sleeping at altitude. Since CPAP alone does not control central sleep apnea emerging at altitude, combined treatment with acetazolamide and CPAP should be considered, in particular, in patients with severe OSA and co-morbidities. Supplemental oxygen combined with CPAP might be advantageous in patients with OSA and concomitant cardiopulmonary disease by preventing hypoxemia and central sleep apnea. In patients unable to use CPAP or if electrical power is not available, an optimally fitted mandibular advancement device might be an alternative treatment option that can be combined with acetazolamide during altitude sojourns. Acetazolamide alone is also beneficial and better than no treatment at all, since it improves oxygen saturation, breathing disturbances, and the excessive blood pressure elevation in OSA patients traveling to altitude

Blood pressure response to exposure to moderate altitude in patients with COPD

Esther I Schwarz,1 Tsogyal D Latshang,1 Michael Furian,1 Deborah Flück,1 Sebastian Segitz,1 Severine Müller-Mottet,1 Silvia Ulrich,1 Konrad E Bloch,1,2 Malcolm Kohler1,2 1Department of Pulmonology and Sleep Disorders Centre, University Hospital of Zurich, Zurich, Switzerland; 2Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland Purpose: Patients with COPD might be particularly susceptible to hypoxia-induced autonomic dysregulation. Decreased baroreflex sensitivity (BRS) and increased blood pressure (BP) variability (BPV) are markers of impaired cardiovascular autonomic regulation and there is evidence for an association between decreased BRS/increased BPV and high cardiovascular risk. The aim of this study was to evaluate the effect of short-term exposure to moderate altitude on BP and measures of cardiovascular autonomic regulation in COPD patients. Materials and methods: Continuous morning beat-to-beat BP was noninvasively measured with a Finometer® device for 10 minutes at low altitude (490 m, Zurich, Switzerland) and for 2 days at moderate altitude (2,590 m, Davos Jakobshorn, Switzerland) – the order of altitude exposure was randomized. Outcomes of interest were mean SBP and DBP, BPV expressed as the coefficient of variation (CV), and spontaneous BRS. Changes between low altitude and day 1 and day 2 at moderate altitude were assessed by ANOVA for repeated measurements with Fisher’s exact test analysis. Results: Thirty-seven patients with moderate to severe COPD (mean±SD age 64±6 years, FEV1 60%±17%) were included. Morning SBP increased by +10.8 mmHg (95% CI: 4.7–17.0, P=0.001) and morning DBP by +5.0 mmHg (95% CI: 0.8–9.3, P=0.02) in response to altitude exposure. BRS significantly decreased (P=0.03), whereas BPV significantly and progressively increased (P<0.001) upon exposure to altitude. Conclusion: Exposure of COPD patients to moderate altitude is associated with a clinically relevant increase in BP, which seems to be related to autonomic dysregulation. Clinical trial registration: ClinicalTrials.gov (NCT01875133). Keywords: COPD, hypobaric hypoxia, baroreflex sensitivity, blood pressure variabilit

Exercise Performance of Lowlanders with Chronic Obstructive Pulmonary Disease Acutely Exposed to 2048 m: A Randomized Cross-Over Trial

Konstantinos Bitos,1 Tobias Kuehne,1 Tsogyal D Latshang,1 Sayaka S Aeschbacher,1 Fabienne Huber,1 Deborah Flueck,1 Elisabeth D Hasler,1 Philipp M Scheiwiller,1 Mona Lichtblau,1 Silvia Ulrich,1 Konrad E Bloch,1 Michael Furian1,2 1University Hospital Zurich, Department of Respiratory Medicine, Zurich, Switzerland; 2Swiss University of Traditional Chinese Medicine, Research Department, Bad Zurzach, SwitzerlandCorrespondence: Michael Furian, University Hospital Zurich, Department of Pulmonology, Raemistrasse 100, Zurich, 8092, Switzerland, Email [email protected]: Amongst the millions of travelers to high altitude worldwide are many with chronic obstructive pulmonary disease (COPD), but data regarding the effects of acute exposure to altitude on exercise performance are limited. The current study investigated how acute exposure to moderate altitude influences exercise performance in COPD patients, providing novel insights to the underlying physiological mechanisms.Methods: Twenty-nine COPD patients, GOLD grade 2– 3, median (quartile) forced expiratory volume in 1 second (FEV1) of 60% predicted (46; 69) performed cycling incremental ramp exercise test (IET) at 490 m and after acute exposure of 2– 6 hours to 2048 m or vice versa, according to a randomized cross-over design. Exercise performance and breath-by-breath analyses of the last 30 seconds of each IET were compared between locations.Results: At 2048 m compared to 490 m, the maximum power output (Wmax) was 77 watts (62;104) vs 88 watts (75;112), median reduction 5 watts (95% CI, 2 to 8, P< 0.05), corresponding to a median reduction of 6% (95% CI, 2 to 11, P< 0.05) compared to 490 m. The peak oxygen uptake (V’O2peak) was 70% predicted (56;86) at 2048 m vs 79% predicted (63;90) at 490 m, median reduction of 6% (95% CI, 3 to 9, P< 0.05). The oxygen saturation by pulse oximetry (SpO2) at 2048 m was reduced by 8% (95% CI, 4 to 9, P< 0.05) compared to 490 m. The minute ventilation (V’E) increased by 2.8L/min (95% CI, 0.9 to 4.2, P< 0.05) at 2048 m. The maximum heart rate and the subjective sense of dyspnea and leg fatigue did not change.Conclusion: Lowlanders with moderate-to-severe COPD acutely exposed to 2048 m reveal small but significant reduction in cycling IET along with a reduced V’O2peak. As dyspnea perception and maximal heart rate were unchanged, the lower blood oxygenation and exaggerated ventilatory response were culprit factors for the reduced performance.Keywords: COPD, exercise, high altitude, hypoxia, hypoxemia, cardiopulmonary exercise testin

Exercise performance and symptoms in lowlanders with COPD ascending to moderate altitude: randomized trial

Michael Furian,1,* Deborah Flueck,1,* Tsogyal D Latshang,1 Philipp M Scheiwiller,1 Sebastian Daniel Segitz,1 S&eacute;verine Mueller-Mottet,1 Christian Murer,1 Adrian Steiner,1 Silvia Ulrich,1 Thomas Rothe,2 Malcolm Kohler,1 Konrad E Bloch1 1Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland; 2Zuercher RehaZentrum Davos, Davos Clavadel, Switzerland *These authors contributed equally to this work Objective: To evaluate the effects of altitude travel on exercise performance and symptoms in lowlanders with COPD. Design: Randomized crossover trial. Setting: University Hospital Zurich (490 m), research facility in mountain villages, Davos Clavadel (1,650 m) and Davos Jakobshorn (2,590 m). Participants: Forty COPD patients, Global Initiative for Obstructive Lung Disease (GOLD) grade 2&ndash;3, living below 800 m, median (quartiles) age 67 y (60; 69), forced expiratory volume in 1 second 57% predicted (49; 70). Intervention: Two-day sojourns at 490 m, 1,650 m, and 2,590 m in randomized order. Outcome measures: Six-minute walk distance (6MWD), cardiopulmonary exercise tests, symptoms, and other health effects. Results: At 490 m, days 1 and 2, median (quartiles) 6MWD were 558 m (477; 587) and 577 m (531; 629). At 2,590 m, days 1 and 2, mean changes in 6MWD from corresponding day at 490 m were -41 m (95% CI -51 to -31) and -40 m (-53 to -27), n=40, P&lt;0.05, both changes. At 1,650 m, day 1, 6MWD had changed by -22 m (-32 to -13), maximal oxygen uptake during bicycle exercise by -7% (-13 to 0) vs 490 m, P&lt;0.05, both changes. At 490 m, 1,650 m, and 2,590 m, day 1, resting PaO2 were 9.0 (8.4; 9.4), 8.1 (7.5; 8.6), and 6.8 (6.3; 7.4) kPa, respectively, P&lt;0.05 higher altitudes vs 490 m. While staying at higher altitudes, nine patients (24%) experienced symptoms or adverse health effects requiring oxygen therapy or relocation to lower altitude.Conclusion: During sojourns at 1,650 m and 2,590 m, lowlanders with moderate to severe COPD experienced a mild reduction in exercise performance and nearly one quarter required oxygen therapy or descent to lower altitude because of adverse health effects. The findings may help to counsel COPD patients planning altitude travel. Registration:&nbsp;ClinicalTrials.gov: NCT01875133 Keywords: CPET, cardiopulmonary exercise testing, acute mountain sickness, hypoxia, adverse health effects, dyspnea, altitude illness, arterial blood gas analysis, pulmonary functio

Time-varying signal analysis to detect high-altitude periodic breathing in climbers ascending to extreme altitude

This work investigates the performance of cardiorespiratory analysis detecting periodic breathing (PB) in chest wall recordings in mountaineers climbing to extreme altitude. The breathing patterns of 34 mountaineers were monitored unobtrusively by inductance plethysmography, ECG and pulse oximetry using a portable recorder during climbs at altitudes between 4497 and 7546 m on Mt. Muztagh Ata. The minute ventilation (VE) and heart rate (HR) signals were studied, to identify visually scored PB, applying time-varying spectral, coherence and entropy analysis. In 411 climbing periods, 30–120 min in duration, high values of mean power (MPVE) and slope (MSlopeVE) of the modulation frequency band of VE, accurately identified PB, with an area under the ROC curve of 88 and 89 %, respectively. Prolonged stay at altitude was associated with an increase in PB. During PB episodes, higher peak power of ventilatory (MPVE) and cardiac (MP LF HR ) oscillations and cardiorespiratory coherence (MP LF Coher ), but reduced ventilation entropy (SampEnVE), was observed. Therefore, the characterization of cardiorespiratory dynamics by the analysis of VE and HR signals accurately identifies PB and effects of altitude acclimatization, providing promising tools for investigating physiologic effects of environmental exposures and diseases