Search

Background: Continuous monitoring of pulse oximetry (S pO 2 ) is recommended during the 6-min walk test (6MWT) to ensure that the lowest S pO 2 is recorded. In this case, severe exercise-induced desaturation (EID; S pO 2 < 80%) triggers walking interruption by the examiner. Our main objective was to assess the impact of this approach on 6MWT distance in patients with chronic respiratory diseases and, second, to evaluate the safety of the test without interruption due to severe EID., Methods: 6MWTs with continuous monitoring of S pO 2 were prospectively performed in subjects with chronic respiratory disease. The participants were randomly allocated to walk with or without S pO 2 real-time assessment. S pO 2 visualization during the test execution was available only in the first group, and walking interruption was requested by the examiner if S pO 2 < 80%., Results: One hundred forty-five participants were included in each group (68.6% females, 62 [52-69] y old) without differences in demographic and resting lung function parameters between them. The main respiratory conditions were COPD ( n = 101), asthma ( n = 73), pulmonary hypertension ( n = 47), and interstitial lung disease ( n = 39). The walked distance was similar comparing groups (349.5 ± 117.5 m vs 351.2 ± 105.4 m). Twenty-five subjects presented with severe EID in the group with real-time S pO 2 assessment, and 20 subjects had severe EID in the group without real-time assessment respectively (overall prevalence of 15.5%). The 23 participants who had their test interrupted by the examiner due to severe EID in the first group (2 subjects stopped by themselves due to excessive symptoms) walked a shorter distance compared to the 11 subjects with severe EID without test interruption in the second group (9 subjects stopped by themselves due to excessive symptoms): 240.6 ± 100.2 m versus 345.9 ± 73.4 m. No exercise-related serious adverse events were observed., Conclusions: Interruption driven by severe EID reduced the walked distance during the 6MWT. No serious adverse event, in turn, was observed in subjects with severe desaturation without real-time S pO 2 assessment., Competing Interests: The authors have disclosed no conflicts of interest., (Copyright © 2024 by Daedalus Enterprises.)

Background: Continuous monitoring of S pO 2 throughout the 6-min walk test (6MWT) unveiled that some patients with respiratory diseases may present values across the test lower than S pO 2 measured at the end of the test. Nevertheless, it remains unclear whether this approach improves the yield of walk-induced desaturation detection in predicting mortality and hospitalizations in patients with COPD., Methods: Four hundred twenty-one subjects (51% males) with mild-very severe COPD underwent a 6MWT with continuous measurement of S pO 2 . Exercise desaturation was defined as a fall in S pO 2 ≥ 4%. All-cause mortality was assessed up to 6 y of follow-up and the rate of hospitalizations in the year succeeding the 6MWT., Results: One hundred forty-nine subjects (35.4%) died during a mean (interquartile) follow-up of 55.5 (30.2-64.1) months. Desaturation was observed in 299/421 (71.0%). S pO 2 along the test was < end S pO 2 (88 [82-92]% vs 90 [84-93]%, P < .001). Desaturation detected only during (but not at the end of) the test was found in 81/421 (19.2%) participants. Multivariate Cox regression model adjusted for sex, body composition, FEV 1 , residual volume/total lung capacity ratio, walk distance, O 2 supplementation during the test, and comorbidities retained the presence of desaturation either at the end (1.85 [95% CI 1.02-3.36]) or only along the test (2.08 [95% CI 1.09-4.01]) as significant predictors of mortality. The rate of hospitalizations was higher in those presenting with any kind of desaturation compared to those without exercise desaturation. Logistic regression analysis revealed that walking interruption and diffusing capacity of the lung for carbon monoxide predicted desaturation observed only during the test., Conclusions: O 2 desaturation missed by end-exercise S pO 2 but exposed by measurements during the test was independently associated with all-cause mortality and hospitalizations in subjects with COPD., Competing Interests: The authors have disclosed no conflicts of interest., (Copyright © 2023 by Daedalus Enterprises.)

Background: Expiratory flow limitation (EFL) is a key physiological abnormality in COPD. Comparing tidal-to-maximum flow-volume (F-V) loops is a simple and widely available method to assess EFL in patients with COPD. We aimed to investigate whether subjects with COPD showing significant resting tidal F-V enveloping (ie, > 50% tidal volume) would present with higher exertional operating lung volumes, which would lead to greater burden of dyspnea and poorer exercise tolerance compared to their counterparts., Methods: 37 subjects with COPD (21 males; 63.1 ± 9.2 years old; FEV 1 = 37 ± 12% predicted) and 9 paired controls (3 males; 55.9 ± 11.7 y old) performed an incremental cardiopulmonary exercise testing on a cycle ergometer. Dyspnea perception, inspiratory capacity maneuvers after 3-4 sequential tidal F-V loops, and esophageal and gastric pressures were measured during exercise., Results: Most subjects (31 of 37, 84%) presented with significant tidal F-V enveloping. Critical inspiratory constraints and upward dyspnea inflection points (as a function of both work rate and ventilation) were reached earlier in these subjects, thereby leading to poorer exercise tolerance compared to their counterparts ( P = .01). Abdominal muscle recruitment (ie, increase in gastric pressure ≥ 15%) during tidal expiration was significantly higher in the EFL+ group. However, this did not bear an influence on the operating lung volumes, inspiratory constraints, dyspnea, cardiocirculatory responses, or exercise tolerance ( P > .05)., Conclusions: Tidal F-V loop enveloping at rest should be valued as it is related to relevant clinical outcomes, such as dyspnea burden and exercise tolerance in subjects with COPD., (Copyright © 2019 by Daedalus Enterprises.)

Introduction: Exercise intolerance is the most predominant symptom in patients with COPD. Nevertheless, it is unclear whether walking economy and gait variability are altered in these patients. Thus, our main objective was to compare the cost of transport and gait variability as a function of speed, including the self-selected walking speed, in subjects with COPD relative to healthy subjects., Methods: 22 subjects, 11 with COPD (FEV 1 = 45 ± 17% of predicted) and 11 age- and sex-matched healthy subjects undertook an evaluation that involved walking on a treadmill at 6 speeds (at 3.2 km/h, at a self-selected walking speed, and at 2 speeds below and 2 speeds above the self-selected walking speed) and measuring the cost of transport (the oxygen consumption normalized by mass and distance), gait variability, perceived dyspnea, and leg fatigue., Results: In subjects with COPD, the cost of transport decreased with increasing walking speed, contrary to healthy subjects, who presented a minimum at the self-selected walking speed. No difference was found in cost of transport between the experimental groups at the same absolute velocity ( P = .62). In subjects with COPD, dyspnea sensation rose above the self-selected walking speed, doubling at the maximal walking velocity ( P = .03), and gait variability was higher at low speeds., Conclusion: Subjects with COPD choose their walking speed so as to keep the dyspnea sensation tolerable and to keep gait variability and cost of transport at an acceptable level. These outcomes suggest that interventions acting on dyspnea and gait pattern may increase patients' self-selected walking speed and improve their quality of life., (Copyright © 2018 by Daedalus Enterprises.)

Introduction: The application of expiratory positive airway pressure (EPAP) in patients with COPD during exercise may reduce dynamic hyperinflation, while, on the other hand, it can increase the resistive work of breathing. Therefore, we evaluated the effects of 2 intensities of EPAP during exercise on tolerance, dynamic hyperinflation, and dyspnea in subjects with moderate to very severe COPD., Methods: We performed a cross-sectional, experimental, 4-visit study. In visit 1, subjects performed symptom-limited cycling incremental cardiopulmonary exercise test (CPET). In visits 2-4, at least 48 h apart, in a randomized order, subjects performed constant CPET without EPAP, EPAP with 5 cm H 2 O (EPAP5), or EPAP with 10 cm H 2 O (EPAP10)., Results: The study included 15 non-hypoxemic subjects ranging from moderate to very severe COPD (mean FEV 1 = 35 ± 11% predicted). Increasing intensities of EPAP during constant CPET tended to cause progressive reduction in exercise tolerance ( P = .11). Of note, 10 of 15 subjects demonstrated significantly shorter average exercise duration with EPAP10 compared to the test without EPAP (-151 ± 105 s, P = .03 or -41 ± 26%). Minute ventilation increment was constrained by EPAP, secondary to a limited increase in tidal volume ( P = .01). Finally, dyspnea sensation and serial measurements of inspiratory capacity during exercise were similar when comparing the three interventions at isotime and at end-constant CPETs., Conclusions: The application of EPAP5 or EPAP10 during exercise tended to cause a progressive reduction in exercise tolerance in subjects with COPD without improvement in dyspnea or dynamic hyperinflation at equivalent exercise duration., (Copyright © 2017 by Daedalus Enterprises.)

Background: Expiratory positive airway pressure (EPAP) is a form of noninvasive positive-pressure ventilatory support that, in spite of not unloading respiratory muscles during inspiration, may reduce the inspiratory threshold load and attenuate expiratory dynamic airway compression, contributing to reduced expiratory air-flow limitation in patients with COPD. We sought to determine the effects of EPAP on operational lung volumes during exercise in COPD patients., Methods: This was a nonrandomized, experimental comparison of 2 exercise conditions (with and without EPAP); subjects completed a treadmill exercise test and performed, before and immediately after exercise, lung volume measurements. Those who overtly developed dynamic hyperinflation (DH), as defined by at least a 15% reduction from pre-exercise inspiratory capacity (IC), were invited for an additional research visit to repeat the same exercise protocol while receiving EPAP through a spring loaded resistor face mask. The primary outcome was IC variance (pre-post exercise) comparison under the 2 exercise conditions., Results: Forty-six subjects (32 males), a mean 65.0 ± 8.2 years of age, and with moderate to severe COPD (FEV(1) = 38 ± 16% predicted) were initially enrolled. From this initial sample, 17 (37%) presented overt DH, as previously defined. No significant difference was found between these subjects and the rest of the initial sample. Comparing before and after exercise, there was significantly less reduction in IC observed when EPAP was used (-0.18 ± 0.35 L vs -0.57 ± 0.45 L, P = .02), allowing greater IC final values (1.45 ± 0.50 L vs 1.13 ± 0.52 L, P = .02)., Conclusions: The application of EPAP reduced DH, as shown by lower operational lung volumes after submaximal exercise in COPD patients who previously manifested exercise DH., (Copyright 2012 Daedalus Enterprises)