Local symptoms of chronic venous insufficiency after deep vein thrombosis (DVT) are well described, but little is known about the effect of residual venous obstruction on exercise capacity. We tested our hypothesis that chronic residual iliofemoral vein occlusion (IFVO) after DVT may impair exercise capacity. Nine post‐DVT patients with residual IFVO and effort intolerance were studied; a comparison cohort consisted of 11 healthy volunteers. Exercise tolerance was assessed by bimodality incremental symptom‐limited cardiopulmonary testing, using leg and arm ergometers. In healthy subjects, leg vein obstruction was modelled by application to the thighs of cuff tourniquets inflated to 30–40 mmHg. Leg exercise tolerance as measured by oxygen uptake at peak exercise (peak ⩒’O₂) was reduced in patients (median 50% predicted (range 36–83%) vs. 88% predicted (67–129%) in normal subjects, p < 0.001). Arm exercise tolerance was also reduced in patients, but less severely than in the legs – the median arm: leg ratio of peak ⩒’O₂ was 0.95 (0.77–1.43) in patients vs. a normal ratio of 0.73 (0.6–1.0) in healthy subjects (p < 0.003). In healthy subjects, bilateral leg vein obstruction by tourniquets reduced peak ⩒’O₂ in leg exercise to 76% predicted (range 55–108%; p < 0.001 vs. standard test). In conclusion, the comparison of arm vs. leg exercise capacity in post‐DVT patients with residual IFVO and the effect of experimental venous obstruction (thigh tourniquets) in healthy subjects suggest that reduced exercise capacity in patients was at least partially caused by reduced venous return. Chronic venous obstruction should be recognized as a cause of exercise limitation.

Aim: We studied the effect of O ₂ supplementation on physiological responses to exercise in patients with pulmonary vascular disease. Methods: Six patients with pulmonary arterial hypertension (PAH), four patients with chronic thromboembolic pulmonary hypertension (CTEPH) (age 54 ± 17 years; 8 females) and 13 healthy individuals (age 50 ± 17 years; 5 females) were tested. PAH/CTEPH was defined hemodynamically by mPAP > 20 mmHg and PVR > 3 WU. Patients performed symptom‐limited cardiopulmonary exercise tests, and constant work‐rate tests (CWRTs) at 80% of the work‐rate (WR) at the gas exchange threshold (GET). Tests breathing room air (RA, 21% O ₂ ) were compared to tests performed breathing 30% O ₂ . Oxygen‐uptake (V̇O ₂ ) kinetics were calculated from the CWRT results. Results: In the PAH/CTEPH group, peak WR, peak V̇O ₂ and V̇O ₂ at the GET improved significantly when breathing 30% O ₂ compared to RA (mean ± SD 85 ± 26 vs. 77 ± 25 W, 18.3 ± 5.8 vs. 15.6 ± 5.7 mL/kg/min and 764 ± 181 vs. 685 ± 154 mL/min; p = 0.011, p = 0.015 and p = 0.012, respectively). Peak V̇O _2/ HR was higher with 30% O ₂ compared with RA (8.8 ± 2.2 vs. 7.7 ± 1.8 mL/beat, p = 0.021). The time constant (tau) of V̇O ₂ kinetics was faster in PAH/CTEPH patients while breathing 30% O ₂ compared to RA (36 ± 4 vs. 43 ± 6 s, p = 0.009). In healthy individuals there was no improvement in V̇O ₂ kinetics while breathing 30% O ₂ compared to RA (tau 35 ± 6 vs. 35 ± 6 s, p = 0.916). Conclusion: A clinically applicable level of O ₂ supplementation (30%) improved maximal and aerobic exercise capacity and V̇O ₂ kinetics in PAH/CTEPH patients. O ₂ supplementation may be considered to support exercise training in PAH/CTEPH patients.

Background/Objectives: COPD patients often complain of severe dyspnea when walking uphill, even up a mild incline. This study aimed to determine whether the dyspnea experienced during uphill walking is disproportionate to the increased mechanical work required to overcome gravity. Methods: Fourteen COPD patients (FEV₁ 49 ± 11% predicted) and nine healthy participants performed three symptom-limited exercise tests on a treadmill, each at a fixed grade: 1%, 2.5%, and 4% for COPD patients; and 1%, 3%, and 5% for healthy participants. Treadmill speed was increased stepwise (3 min/stage). Inspiratory capacity (IC) maneuvers were performed during the last minute of each stage. Borg dyspnea scores (0–10) at the different inclines were compared at a uniform level of oxygen uptake (iso-$\dot{\mathrm{V}}$O₂). Results: Borg dyspnea scores by COPD patients at the highest iso-$\dot{\mathrm{V}}$O₂ attained were significantly higher at 4% treadmill grade compared to 2.5% and compared to 1% grade (7 ± 2 vs. 5 ± 2 vs. 5 ± 2, respectively; p < 0.001 for 4% vs. 1% grade, p < 0.005 for 4% vs. 2.5%). Dynamic hyperinflation worsened with grade, as reflected by decrease in inspiratory reserve volume (IRV) at the highest common iso-$\dot{\mathrm{V}}$O₂ attained: 798 ± 336 mL at 1% grade vs. 698 ± 325 mL at 2.5% (p < 0.004) vs. 564 ± 350 mL at 4% (p < 0.002 for 4% vs. 1%; p < 0.004 for 4% vs. 2.5%). In contrast, healthy participants showed no significant grade-dependent differences in dyspnea or IRV at iso-$\dot{\mathrm{V}}$O₂. Conclusions: Walking uphill in itself increases breathlessness of COPD subjects at iso-$\dot{\mathrm{V}}$O₂, suggesting that the increased dyspnea cannot be explained simply by the increased work. This phenomenon may be related to dynamic hyperinflation, which is worse at steeper inclines.