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

Background: 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.

Hyperoxia improves exercise capacity in cardiopulmonary disease: a series of randomised controlled trials.

Background: The aim of this study was to investigate the overall and differential effect of breathing hyperoxia (inspiratory oxygen fraction (F IO2 ) 0.5) versus placebo (ambient air, F IO2 0.21) to enhance exercise performance in healthy people, patients with pulmonary vascular disease (PVD) with precapillary pulmonary hypertension (PH), COPD, PH due to heart failure with preserved ejection fraction (HFpEF) and cyanotic congenital heart disease (CHD) using data from five randomised controlled trials performed with identical protocols. Methods: 91 subjects (32 healthy, 22 with PVD with pulmonary arterial or distal chronic thromboembolic PH, 20 with COPD, 10 with PH in HFpEF and seven with CHD) performed two cycle incremental (IET) and two constant work-rate exercise tests (CWRET) at 75% of maximal load (Wmax), each with ambient air and hyperoxia in single-blinded, randomised, controlled, crossover trials. The main outcomes were differences in Wmax (IET) and cycling time (CWRET) with hyperoxia versus ambient air. Results: Overall, hyperoxia increased Wmax by +12 W (95% CI: 9-16, p<0.001) and cycling time by +6:13 min (4:50-7:35, p<0.001), with improvements being highest in patients with PVD (Wmax/min: +18%/+118% versus COPD: +8%/+60%, healthy: +5%/+44%, HFpEF: +6%/+28%, CHD: +9%/+14%). Conclusion: This large sample of healthy subjects and patients with various cardiopulmonary diseases confirms that hyperoxia significantly prolongs cycling exercise with improvements being highest in endurance CWRET and patients with PVD. These results call for studies investigating optimal oxygen levels to prolong exercise time and effects on training.

Effect of nocturnal oxygen therapy on exercise performance of COPD patients at 2048 m: data from a randomized clinical trial.

This trial evaluates whether nocturnal oxygen therapy (NOT) during a stay at 2048 m improves altitude-induced exercise intolerance in lowlanders with chronic obstructive pulmonary disease (COPD). 32 lowlanders with moderate to severe COPD, mean ± SD forced expiratory volume in the first second of expiration (FEV1) 54 ± 13% predicted, stayed for 2 days at 2048 m twice, once with NOT, once with placebo according to a randomized, crossover trial with a 2-week washout period at < 800 m in-between. Semi-supine, constant-load cycle exercise to exhaustion at 60% of maximal work-rate was performed at 490 m and after the first night at 2048 m. Endurance time was the primary outcome. Additional outcomes were cerebral tissue oxygenation (CTO), arterial blood gases and breath-by-breath measurements ( http://www.ClinicalTrials.gov NCT02150590). Mean ± SE endurance time at 490 m was 602 ± 65 s, at 2048 m after placebo 345 ± 62 s and at 2048 m after NOT 293 ± 60 s, respectively (P < 0.001 vs. 490 m). Mean difference (95%CI) NOT versus placebo was - 52 s (- 174 to 70), P = 0.401. End-exercise pulse oximetry (SpO2), CTO and minute ventilation ([Formula: see text]) at 490 m were: SpO2 92 ± 1%, CTO 65 ± 1%, [Formula: see text] 37.7 ± 2.0 L/min; at 2048 m with placebo: SpO2 85 ± 1%, CTO 61 ± 1%, [Formula: see text] 40.6 ± 2.0 L/min and with NOT: SpO2 84 ± 1%; CTO 61 ± 1%; [Formula: see text] 40.6 ± 2.0 L/min (P < 0.05, SpO2, CTO at 2048 m with placebo vs. 490 m; P = NS, NOT vs. placebo). Altitude-related hypoxemia and cerebral hypoxia impaired exercise endurance in patients with moderate to severe COPD and were not prevented by NOT.

Effect of Nocturnal Oxygen Therapy on Daytime Pulmonary Hemodynamics in Patients With Chronic Obstructive Pulmonary Disease Traveling to Altitude: A Randomized Controlled Trial.

INTRODUCTION: We investigated whether nocturnal oxygen therapy (NOT) mitigates the increase of pulmonary artery pressure in patients during daytime with chronic obstructive pulmonary disease (COPD) traveling to altitude. METHODS: Patients with COPD living below 800 m underwent examinations at 490 m and during two sojourns at 2,048 m (with a washout period of 2 weeks < 800 m between altitude sojourns). During nights at altitude, patients received either NOT (3 L/min) or placebo (ambient air 3 L/min) via nasal cannula according to a randomized crossover design. The main outcomes were the tricuspid regurgitation pressure gradient (TRPG) measured by echocardiography on the second day at altitude (under ambient air) and various other echocardiographic measures of the right and left heart function. Patients fulfilling predefined safety criteria were withdrawn from the study. RESULTS: Twenty-three COPD patients [70% Global Initiative for Chronic Obstructive Lung Disease (GOLD) II/30% GOLD III, mean ± SD age 66 ± 5 years, FEV1 54% ± 13% predicted] were included in the per-protocol analysis. TRPG significantly increased when patients traveled to altitude (from low altitude 21.7 ± 5.2 mmHg to 2,048 m placebo 27.4 ± 7.3 mmHg and 2,048 m NOT 27.8 ± 8.3 mmHg) difference between interventions (mean difference 0.4 mmHg, 95% CI -2.1 to 3.0, p = 0.736). The tricuspid annular plane systolic excursion was significantly higher after NOT vs. placebo [2.6 ± 0.6 vs. 2.3 ± 0.4 cm, mean difference (95% confidence interval) 0.3 (0.1 - 0.5) cm, p = 0.005]. During visits to 2,048 m until 24 h after descent, eight patients (26%) using placebo and one (4%) using NOT had to be withdrawn because of altitude-related adverse health effects (p < 0.001). CONCLUSION: In lowlanders with COPD remaining free of clinically relevant altitude-related adverse health effects, changes in daytime pulmonary hemodynamics during a stay at high altitude were trivial and not modified by NOT. CLINICAL TRIAL REGISTRATION: www.ClinicalTrials.gov, identifier NCT02150590.

Nocturnal Heart Rate and Cardiac Repolarization in Lowlanders With Chronic Obstructive Pulmonary Disease at High Altitude: Data From a Randomized, Placebo-Controlled Trial of Nocturnal Oxygen Therapy.

Background: Chronic obstructive pulmonary disease (COPD) is associated with cardiovascular disease. We investigated whether sleeping at altitude increases nocturnal heart rate (HR) and other markers of cardiovascular risk or arrhythmias in lowlanders with COPD and whether this can be prevented by nocturnal oxygen therapy (NOT). Methods: Twenty-four COPD patients, with median age of 66 years and forced expiratory volume in 1 s (FEV1) 55% predicted, living <800 m underwent sleep studies at Zurich (490 m) and during 2 sojourns of 2 days each at St. Moritz (2,048 m) separated by 2-week washout at <800 m. During nights at 2,048 m, patients received either NOT (2,048 m NOT) or ambient air (2,048 m placebo) 3 L/min via nasal cannula according to a randomized, placebo-controlled crossover trial. Sleep studies comprised ECG and pulse oximetry to measure HR, rhythm, HR-adjusted QT interval (QTc), and mean oxygen saturation (SpO2). Results: In the first nights at 490 m, 2,048 m placebo, and 2,048 m NOT, medians (quartiles) of SpO2 were 92% (90; 94), 86% (83; 89), and 97% (95; 98) and of HR were 73 (66; 82), 82 (71; 85), and 78 bpm (67; 74) (P < 0.05 all respective comparisons). QTc increased from 417 ms (404; 439) at 490 m to 426 ms (405; 440) at 2,048 m placebo (P < 0.05) and was 420 ms (405; 440) at 2,048 m NOT (P = NS vs. 2,048 m placebo). The number of extrabeats and complex arrhythmias was similar over all conditions. Conclusions: While staying at 2,048 m, lowlanders with COPD experienced nocturnal hypoxemia in association with an increased HR and prolongation of the QTc interval. NOT significantly improved SpO2 and lowered HR, without changing QTc. Whether oxygen therapy would reduce HR and arrhythmia during longer altitude sojourns remains to be elucidated.

Effect of Nocturnal Oxygen on Blood Pressure Response to Altitude Exposure in COPD - Data from a Randomized Placebo-Controlled Cross-Over Trial.

PURPOSE: Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to hypoxia-induced autonomic dysregulation. Hypoxemia is marked during sleep. In COPD, altitude exposure is associated with an increase in blood pressure (BP) and a decrease in baroreflex-sensitivity (BRS). Whether nocturnal oxygen therapy (NOT) may mitigate these cardiovascular autonomic changes in COPD at altitude is unknown. MATERIALS AND METHODS: In a randomized placebo-controlled cross-over trial, 32 patients with moderate-to-severe COPD living <800 m were subsequently allocated to NOT and placebo during acute exposure to altitude. Measurements were done at low altitude at 490 m and during two stays at 2048 m on NOT (3 L/min) and placebo (3 L/min, ambient air) via nasal cannula. Allocation and intervention sequences were randomized. Outcomes of interest were BP, BRS (from beat-to-beat BP measurement), BP variability (BPV), and heart rate. RESULTS: About 23/32 patients finished the trial per protocol (mean (SD) age 66 (5) y, FEV1 62 (14) % predicted) and 9/32 experienced altitude-related illnesses (8 vs 1, p < 0.05 placebo vs NOT). NOT significantly mitigated the altitude-induced increase in systolic BP compared to placebo (Δ median -5.8 [95% CI -22.2 to -1.4] mmHg, p = 0.05) but not diastolic BP (-3.5 [95% CI -12.6 to 3.0] mmHg; p = 0.21) or BPV. BRS at altitude was significantly higher in NOT than in placebo (1.7 [95% CI 0.3 to 3.4] ms/mmHg, p = 0.02). CONCLUSION: NOT may protect from hypoxia-induced autonomic dysregulation upon altitude exposure in COPD and thus protect from a relevant increase in BP and decrease in BRS. NOT may provide cardiovascular benefits in COPD during conditions of increased hypoxemia and may be considered in COPD travelling to altitude.

Right Atrial Pressure During Exercise Predicts Survival in Patients With Pulmonary Hypertension.

Background We investigated changes in right atrial pressure (RAP) during exercise and their prognostic significance in patients assessed for pulmonary hypertension (PH). Methods and Results Consecutive right heart catheterization data, including RAP recorded during supine, stepwise cycle exercise in 270 patients evaluated for PH, were analyzed retrospectively and compared among groups of patients with PH (mean pulmonary artery pressure [mPAP] ≥25 mm Hg), exercise-induced PH (exPH; resting mPAP <25 mm Hg, exercise mPAP >30 mm Hg, and mPAP/cardiac output >3 Wood Units (WU)), and without PH (noPH). We investigated RAP changes during exercise and survival over a median (quartiles) observation period of 3.7 (2.8-5.6) years. In 152 patients with PH, 58 with exPH, and 60 with noPH, median (quartiles) resting RAP was 8 (6-11), 6 (4-8), and 6 (4-8) mm Hg (P<0.005 for noPH and exPH versus PH). Corresponding peak changes (95% CI) in RAP during exercise were 5 (4-6), 3 (2-4), and -1 (-2 to 0) mm Hg (noPH versus PH P<0.001, noPH versus exPH P=0.027). RAP increase during exercise correlated with mPAP/cardiac output increase (r=0.528, P<0.001). The risk of death or lung transplantation was higher in patients with exercise-induced RAP increase (hazard ratio, 4.24; 95% CI, 1.69-10.64; P=0.002) compared with patients with unaltered or decreasing RAP during exercise. Conclusions In patients evaluated for PH, RAP during exercise should not be assumed as constant. RAP increase during exercise, as observed in exPH and PH, reflects hemodynamic impairment and poor prognosis. Therefore, our data suggest that changes in RAP during exercise right heart catheterization are clinically important indexes of the cardiovascular function.

Altitude Travel in Patients With Pulmonary Hypertension: Randomized Pilot-Trial Evaluating Nocturnal Oxygen Therapy.

Introduction: Stable patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PH) wish to undergo altitude sojourns or air travel but fear disease worsening. This pilot study investigates health effects of altitude sojourns and potential benefits of nocturnal oxygen therapy (NOT) in PH patients. Methods: Nine stable PH patients, age 65 (47; 71) years, 5 women, in NYHA class II, on optimized medication, were investigated at 490 m and during two sojourns of 2 days/nights at 2,048 m, once using NOT, once placebo (ambient air), 3 L/min per nasal cannula, according to a randomized crossover design with 2 weeks washout at <800 m. Assessments included safety, nocturnal pulse oximetry (SpO2), 6-min walk distance (6 MWD), and echocardiography. Results: At 2,048 m, two of nine patients required medical intervention, one for exercise-induced syncope, one for excessive nocturnal hypoxemia (SpO2 < 75% for >30 min). Both recovered immediately with oxygen therapy. Two patients suffered from acute mountain sickness. In 6 patients with complete data, nocturnal mean SpO2 and cyclic SpO2 dips reflecting sleep apnea significantly differed from 490 to 2,048 m with placebo, and 2,048 m with NOT (medians, quartiles): SpO2 93 (91; 95)%, 89 (85; 90)%, 97 (95; 97)%; SpO2 dips 10.4/h (3.1; 26.9), 34.0/h (5.3; 81.3), 0.3/h (0.1; 2.3). 6 MWD at 490, 2,048 m without and with NOT was 620 m (563; 720), 583 m (467; 696), and 561 m (501; 688). Echocardiographic indices of heart function and PH were unchanged at 2,048 m with/without NOT vs. 490 m. Conclusions: 7/9 PH patients stayed safely at 2,048 m but revealed hypoxemia, sleep apnea, and reduced 6 MWD. Hemodynamic changes were trivial. NOT improved oxygenation and sleep apnea. The current pilot trial is important for designing further studies on altitude tolerance of PH patients.

Effect of Nocturnal Oxygen Therapy on Nocturnal Hypoxemia and Sleep Apnea Among Patients With Chronic Obstructive Pulmonary Disease Traveling to 2048 Meters: A Randomized Clinical Trial.

Importance: There are no established measures to prevent nocturnal breathing disturbances and other altitude-related adverse health effects (ARAHEs) among lowlanders with chronic obstructive pulmonary disease (COPD) traveling to high altitude. Objective: To evaluate whether nocturnal oxygen therapy (NOT) prevents nocturnal hypoxemia and breathing disturbances during the first night of a stay at 2048 m and reduces the incidence of ARAHEs. Design, Setting, and Participants: This randomized, placebo-controlled crossover trial was performed from January to October 2014 with 32 patients with COPD living below 800 m with forced expiratory volume in the first second of expiration (FEV1) between 30% and 80% predicted, pulse oximetry of at least 92%, not requiring oxygen therapy, and without history of sleep apnea. Evaluations were performed at the University Hospital Zurich (490 m, baseline) and during 2 stays of 2 days and nights each in a Swiss Alpine hotel at 2048 m while NOT or placebo treatment was administered in a randomized order. Between altitude sojourns, patients spent at least 2 weeks below 800 m. Data analysis was performed from January 1, 2015, to December 31, 2018. Intervention: During nights at 2048 m, NOT or placebo (room air) was administered at 3 L/min by nasal cannula. Main Outcomes and Measures: Coprimary outcomes were differences between NOT and placebo intervention in altitude-induced change in mean nocturnal oxygen saturation (SpO2) as measured by pulse oximetry and apnea-hypopnea index (AHI) measured by polysomnography during night 1 at 2048 m and analyzed according to the intention-to-treat principle. Further outcomes were the incidence of predefined ARAHE, other variables from polysomnography results and respiratory sleep studies in the 2 nights at 2048 m, clinical findings, and symptoms. Results: Of the 32 patients included, 17 (53%) were women, with a mean (SD) age of 65.6 (5.6) years and a mean (SD) FEV1 of 53.1% (13.2%) predicted. At 490 m, mean (SD) SpO2 was 92% (2%) and mean (SD) AHI was 21.6/h (22.2/h). At 2048 m with placebo, mean (SD) SpO2 was 86% (3%) and mean (SD) AHI was 34.9/h (20.7/h) (P < .001 for both comparisons). Compared with placebo, NOT increased SpO2 by a mean of 9 percentage points (95% CI, 8-11 percentage points; P < .001), decreased AHI by 19.7/h (95% CI, 11.4/h-27.9/h; P < .001), and improved subjective sleep quality measured on a visual analog scale by 9 percentage points (95% CI, 0-17 percentage points; P = .04). During visits to 2048 m or within 24 hours after descent, 8 patients (26%) using placebo and 1 (4%) using NOT experienced ARAHEs (P < .001). Conclusions and Relevance: Lowlanders with COPD experienced hypoxemia, sleep apnea, and impaired well-being when staying at 2048 m. Because NOT significantly mitigated these undesirable effects, patients with moderate to severe COPD may benefit from preventive NOT during high altitude travel. Trial Registration: ClinicalTrials.gov Identifier: NCT02150590.

Physical activity in incident patients with pulmonary arterial and chronic thromboembolic hypertension.

INTRODUCTION: The cardinal symptom of pulmonary hypertension (PH) is dyspnea on exertion, leading to decreased activity in daily living. The aim of this study was to analyze daily physical activity in incident patients with arterial or chronic thromboembolic PH (PAH/CTEPH) and to investigate its correlation with pulmonary hemodynamics, symptoms, exercise capacity, and other outcomes. METHODS: Incident patients with PAH/CTEPH had a 1-week activity assessment by the arm-worn accelerometer SenseWear within - 3 months/+ 2 weeks of the diagnostic right heart catheterization (RHC) and baseline assessments including 6-minute walking distance (6MWD). Activity was correlated to RHC data at rest and exercise and to other outcomes. RESULTS: Thirty-nine PH-patients (24 PAH, 15 CTEPH, 23 females, 65(54;73) years, mean pulmonary artery pressure (mPAP) 38(30;46) mmHg, cardiac output (CO) 5.2(4.6;6.3) l/min, 6MWD 458(300;593) m) were included. 64% had a sedentary lifestyle ( < 5000 steps/day), 26% were moderately active (5000-9999 steps/day), and 10% were active. In a multivariate stepwise regression analysis including age, gender, 6MWD and hemodynamics at rest and during exercise (heart rate, mPAP, stroke volume), the 6MWD was the only independent predictor of steps/day (B = 16.8 (95% CI 11.6-22.0), p < 0.001). CONCLUSION: Daily physical activity as steps/day assessed in incident patients with PAH/CTEPH did not well correlate with invasive hemodynamics at rest or during exercise, but very well with the 6MWD. Whether daily activity assessments provide additional information to simple walk distance on risk factor profiles during follow-up in patients with PAH/CTEPH remains to be clarified.

Effect of domiciliary oxygen therapy on exercise capacity and quality of life in patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension: a randomised, placebo-controlled trial.

STUDY QUESTION: We investigated whether domiciliary oxygen therapy (DOXT) increases exercise capacity and quality of life in patients with pulmonary arterial or distal chronic thromboembolic pulmonary hypertension (PAH/CTEPH) presenting with mild resting hypoxaemia and exercise-induced oxygen desaturation. MATERIALS AND METHODS: 30 patients with PAH/CTEPH, mean±sd age 60±15 years, pulmonary artery pressure 39±11 mmHg, resting arterial oxygen saturation measured by pulse oximetry (S pO2 ) ≥90%, S pO2 drop during a 6-min walk test ≥4%, on pulmonary hypertension-targeted medication, were randomised in a double-blind crossover protocol to DOXT and placebo (ambient air) treatment, each over 5 weeks, at 3 L·min-1 via nasal cannula overnight and when resting during the day. Treatment periods were separated by 2 weeks of washout. Co-primary outcomes were changes in 6-min walk distance (6MWD, breathing ambient air) and physical functioning scale of the 36-item short-form medical outcome questionnaire during treatment periods. RESULTS: DOXT increased the 6MWD from baseline 478±113 m by a mean (95% CI) of 19 (6-32) m, and physical functioning from 52±29 by 4 (0-8) points. Corresponding changes with placebo were 1 (-11-13) m in 6MWD and -2 (-6-2) points in physical functioning. Between-treatment differences in changes were 6MWD 18 (1-35) m (p=0.042) and physical functioning 6 (1-11) points (p=0.029). DOXT significantly improved the New York Heart Association functional class versus placebo. ANSWER TO THE QUESTION: This first randomised trial in PAH/CTEPH patients with exercise-induced hypoxaemia demonstrates that DOXT improves exercise capacity, quality of life and functional class. The results support large long-term randomised trials of DOXT in PAH/CTEPH.

Effect of breathing oxygen-enriched air on exercise performance in patients with precapillary pulmonary hypertension: randomized, sham-controlled cross-over trial.

Aims: The purpose of the current trial was to test the hypothesis that breathing oxygen-enriched air increases exercise performance of patients with pulmonary arterial or chronic thrombo-embolic pulmonary hypertension (PAH/CTEPH) and to investigate involved mechanisms. Methods and results: Twenty-two patients with PAH/CTEPH, eight women, means ± SD 61 ± 14 years, resting mPAP 35 ± 9mmHg, PaO2 ambient air >7.3 kPa, underwent four bicycle ergospirometries to exhaustion on different days, while breathing oxygen-enriched (FiO2 0.50, hyperoxia) or ambient air (FiO2 0.21, normoxia) using progressively increased or constant load protocols (with 75% maximal work rate under FiO2 0.21), according to a randomized, sham-controlled, single-blind, cross-over design. ECG, pulmonary gas-exchange, arterial blood gases, cerebral and quadriceps muscle tissue oxygenation (CTO and QMTO) by near-infrared spectroscopy were measured. In ramp exercise, maximal work rate increased from 113 ± 38 W with normoxia to 132 ± 48 W with hyperoxia, mean difference 19.7 (95% CI 10.5-28.9) W, P < 0.001. Constant load exercise endurance increased from 571 ± 443 to 1242 ± 514 s, mean difference 671 (95% CI 392-951) s, P < 0.001. At end-exercise with hyperoxia PaO2, CTO, QMTO, and PaCO2 were increased, and ventilatory equivalents for CO2 were reduced while the physiological dead space/tidal volume ratio remained unchanged. Conclusion: In patients with PAH/CTEPH, breathing oxygen-enriched air provides major increases in exercise performance. This is related to an improved arterial oxygenation that promotes oxygen availability in muscles and brain and to a reduction of the excessive ventilatory response to exercise thereby enhancing ventilatory efficiency. Patients with PAH/CTEPH may therefore benefit from oxygen therapy during daily physical activities and training. Trial registration: clinicaltrials.gov Identifier: NCT01748474.

Mechanisms of Improved Exercise Performance under Hyperoxia.

BACKGROUND: The impact of hyperoxia on exercise limitation is still incompletely understood. OBJECTIVES: We investigated to which extent breathing hyperoxia enhances the exercise performance of healthy subjects and which physiologic mechanisms are involved. METHODS: A total of 32 healthy volunteers (43 ± 15 years, 12 women) performed 4 bicycle exercise tests to exhaustion with ramp and constant-load protocols (at 75% of the maximal workload [Wmax] on FiO2 0.21) on separate occasions while breathing ambient (FiO2 0.21) or oxygen-enriched air (FiO2 0.50) in a random, blinded order. Workload, endurance, gas exchange, pulse oximetry (SpO2), and cerebral (CTO) and quadriceps muscle tissue oxygenation (QMTO) were measured. RESULTS: During the final 15 s of ramp exercising with FiO2 0.50, Wmax (mean ± SD 270 ± 80 W), SpO2 (99 ± 1%), and CTO (67 ± 9%) were higher and the Borg CR10 Scale dyspnea score was lower (4.8 ± 2.2) than the corresponding values with FiO2 0.21 (Wmax 257 ± 76 W, SpO2 96 ± 3%, CTO 61 ± 9%, and Borg CR10 Scale dyspnea score 5.7 ± 2.6, p < 0.05, all comparisons). In constant-load exercising with FiO2 0.50, endurance was longer than with FiO2 0.21 (16 min 22 s ± 7 min 39 s vs. 10 min 47 s ± 5 min 58 s). With FiO2 0.50, SpO2 (99 ± 0%) and QMTO (69 ± 8%) were higher than the corresponding isotime values to end-exercise with FiO2 0.21 (SpO2 96 ± 4%, QMTO 66 ± 9%), while minute ventilation was lower in hyperoxia (82 ± 18 vs. 93 ± 23 L/min, p < 0.05, all comparisons). CONCLUSION: In healthy subjects, hyperoxia increased maximal power output and endurance. It improved arterial, cerebral, and muscle tissue oxygenation, while minute ventilation and dyspnea perception were reduced. The findings suggest that hyperoxia enhanced cycling performance through a more efficient pulmonary gas exchange and a greater availability of oxygen to muscles and the brain (cerebral motor and sensory neurons).

Exercise pulmonary haemodynamics predict outcome in patients with systemic sclerosis.

The aim of the present study was to investigate the prognostic value of exercise haemodynamics measured during right heart catheterisation (RHC) in patients with systemic sclerosis (SSc) referred for evaluation of pulmonary hypertension.SSc patients undergoing RHC at rest and during maximal supine incremental cycle exercise were grouped into resting precapillary pulmonary hypertension (PHrest) (mean pulmonary artery pressure (mPAP) ≥25 mmHg, pulmonary artery wedge pressure <15 mmHg), exercise-induced pulmonary hypertension (PHex) (mPAP ≥30 mmHg and mPAP/cardiac output >3 mmHg·L-1·min-1 at maximal exercise), and without pulmonary hypertension (PHnone). Patients' characteristics, haemodynamics and follow up data were compared between groups.72 SSc patients were followed for median (interquartile range) 33 (15-55) months. Mean (95% CI) survival without transplantation estimated by Kaplan-Meyer analysis was 4.4 (0.8-2.9) years in PHrest (n=17), 5.2 (4.4-6.1) years in PHex (n=28) and 9.5(8.4-10.6) years in PHnone (n=27; p<0.05 versus others). In Cox regression models, the exercise-induced increase in mPAP (hazard ratio (HR) 1.097, 95% CI 1.002-1.200) and the coefficient of pulmonary vascular distensibility alpha (HR 0.100, 95% CI 0.012-0.871) controlled for age, but not resting haemodynamics predicted transplant-free survival.Among SSc patients with normal mPAP at rest, an excessive increase in mPAP during exercise and an impaired vascular distensibility may indicate an early stage of pulmonary vasculopathy, associated with reduced survival similar to resting pulmonary hypertension patients.

Prevalence of Anxiety and Depression in Pulmonary Hypertension and Changes during Therapy.

BACKGROUND: Pulmonary hypertension (PH) leads to reduced health-related quality of life (HRQoL). OBJECTIVE: To investigate the prevalence and course of anxiety and depression and their association with HRQoL, disease severity and survival in PH. METHODS: 131 PH patients (91 pulmonary arterial, 30 chronic thromboembolic, 10 due to lung disease; 84 female, 47 male) had repeated assessments with the Hospital Anxiety and Depression Scale (HADS), HRQoL, six-minute walk distance and WHO functional class during a mean course of 16 ± 12 months. RESULTS: Among the 49 incident and 82 prevalent PH patients, the HADS score was positive in 53%/21% (depression), 51%/24% (anxiety) and 63%/26% (total score) (all p < 0.05). The HADS score was improved at the second assessment in incident patients. The HADS score correlated with HRQoL at all consecutive assessments and with functional class until the third assessment, but not with baseline hemodynamics, age or gender. CONCLUSION: Mood disorders remain underdiagnosed in PH. The higher prevalence of anxiety/depression in incident versus prevalent patients and the improvement over time may indicate an amelioration of mood disorders after PH diagnosis and treatment.

Pressure-Flow During Exercise Catheterization Predicts Survival in Pulmonary Hypertension.

BACKGROUND: Pulmonary hypertension manifests with impaired exercise capacity. Our aim was to investigate whether the mean pulmonary arterial pressure to cardiac output relationship (mPAP/CO) predicts transplant-free survival in patients with pulmonary arterial hypertension (PAH) and inoperable chronic thromboembolic pulmonary hypertension (CTEPH). METHODS: Hemodynamic data according to right heart catheterization in patients with PAH and CTEPH at rest and during supine incremental cycle exercise were analyzed. Transplant-free survival and predictive value of hemodynamics were assessed by using Kaplan-Meier and Cox regression analyses. RESULTS: Seventy patients (43 female; 54 with PAH, 16 with CTEPH; median (quartiles) age, 65 [50; 73] years; mPAP, 34 [29; 44] mm Hg; cardiac index, 2.8 [2.3; 3.5] [L/min]/m(2)) were followed up for 610 (251; 1256) days. Survival at 1, 3, 5, and 7 years was 89%, 81%, 71%, and 59%. Age, World Health Organization-functional class, 6-min walk test, and mixed-venous oxygen saturation (but not resting hemodynamics) predicted transplant-free survival. Maximal workload (hazard ratio [HR], 0.94 [95% CI, 0.89-0.99]; P = .027), peak cardiac index (HR, 0.51 [95% CI, 0.27-0.95]; P = .034), change in cardiac index, 0.25 [95% CI, 0.06-0.94]; P = .040), and mPAP/CO (HR, 1.02 [95% CI, 1.01-1.03]; P = .003) during exercise predicted survival. Values for mPAP/CO predicted 3-year transplant-free survival with an area under the curve of 0.802 (95% CI, 0.66-0.95; P = .004). CONCLUSIONS: In this collective of patients with PAH or CTEPH, the pressure-flow relationship during exercise predicted transplant-free survival and correlated with established markers of disease severity and outcome. Right heart catheterization during exercise may provide important complementary prognostic information in the management of pulmonary hypertension.

Effect of oxygen and acetazolamide on nocturnal cardiac conduction, repolarization, and arrhythmias in precapillary pulmonary hypertension and sleep-disturbed breathing.

BACKGROUND: Sleep-disturbed breathing (SDB) is common in patients with precapillary pulmonary hypertension (PH). Nocturnal oxygen therapy (NOT) and acetazolamide improve SDB in patients with PH, and NOT improves exercise capacity. We investigated the effect of NOT and acetazolamide on nocturnal cardiac conduction, repolarization, and arrhythmias in patients with PH and SDB. METHODS: In a randomized, placebo-controlled, double-blind, crossover trial, 23 patients with arterial (n = 16) or chronic thromboembolic PH (n = 7) and SDB defined as a mean nocturnal oxygen saturation < 90% or dips (> 3%) > 10/h with daytime Pao2 ≥ 7.3 kPa were studied. Participants received NOT (3 L/min), acetazolamide tablets (2 × 250 mg), and sham-NOT/placebo each during 1 week separated by a 1-week washout period. Three-lead ECG was recorded during overnight polysomnography at the end of each treatment period. Repolarization indices were averaged over three cardiac cycles at late evening and at early morning, and nocturnal arrhythmias were counted. RESULTS: NOT was associated with a lower overnight (68 ± 10 beats/min vs 72 ± 9 beats/min, P = .010) and early morning heart rate compared with placebo. At late evening, the heart rate-adjusted PQ time was increased under acetazolamide compared with placebo (mean difference, 10 milliseconds; 95% CI, 0-20 milliseconds; P = .042). In the morning under NOT, the heart rate-adjusted QT (QTc) interval was decreased compared with placebo (mean difference, -25 milliseconds; 95% CI, -45 to -6 milliseconds; P = .007), and the interval between the peak and the end of the T wave on the ECG was shorter compared with acetazolamide (mean difference, -11 milliseconds; 95% CI, -21 to -1 milliseconds; P = .028). Arrhythmias were rare and similar with all treatments. CONCLUSIONS: In patients with PH with SDB, NOT reduces nocturnal heart rate and QTc in the morning, thus, favorably modifying prognostic markers. TRIAL REGISTRY: ClinicalTrials.gov; No.: NTC-01427192; URL: www.clinicaltrials.gov.