Noninvasive ventilation during walking in patients with severe COPD: a randomised cross-over trial.

It was hypothesised that noninvasive positive-pressure ventilation (NPPV) applied during walking prevents exercise-induced hypoxaemia and improves exercise performance in severe chronic obstructive pulmonary disease (COPD) patients already receiving long-term NPPV. A total of 20 COPD patients (mean+/-sd age 65.1+/-8.7 yrs, forced expiratory volume in one second 27+/-8% predicted and total lung capacity 116+/-27% pred) reporting dyspnoea, even during mild exertion, underwent two 6-min walking tests with a rollator and supplemental oxygen (2.1+/-0.9 L.min(-1)) in a randomised cross-over design: with and without pressure-limited NPPV as used at home (inspiratory:expiratory pressure 2.9+/-0.44:0.4+/-0.1 kPa (29+/-4:4+/-1 mbar), respiratory frequency 20+/-2 breaths.min(-1)). The arterial oxygen tension significantly increased by 1.39+/-1.43 kPa (95% confidence interval (CI) 0.71-2.07 kPa) after walking with NPPV, but significantly decreased by 1.43+/-1.06 kPa (95% CI -1.92 - -0.94 kPa) without NPPV. Dyspnoea, as assessed by the Borg dyspnoea scale, significantly decreased from 6 (interquartile range (IQR) 4.5-10) to 4 (1.5-4.5) and walking distance significantly increased from 209 (IQR 178-279) to 252 (203-314) m when walking was NPPV-aided. In chronic hypercapnic chronic obstructive pulmonary disease, high-intensity noninvasive positive-pressure ventilation can also be administered during walking with unchanged ventilator settings compared with settings used at rest, thus resulting in improved oxygenation, decreased dyspnoea and increased walking distance. Therefore, noninvasive positive-pressure ventilation during walking could prevent hypoxia-induced complications and could, in future, play a role in palliative care.     

Physiologic responses to incremental and self-paced exercise in COPD: a comparison of three tests

OBJECTIVES: To investigate cardiorespiratory and dyspnea responses to incremental and self-paced exercise tests in patients with COPD. DESIGN: A prospective within-subject design was used. PATIENTS: Twenty stable subjects (15 men), with a mean (+/- SD) age of 64.0 +/- 7.5 years and moderate-to-severe COPD (ie, mean FEV(1), 0.8 +/- 0.3 L and 28.9 +/- 7.9% predicted) were studied. METHODS: Each subject completed a 6-min walk test (6MWT), an incremental shuttle walking test (ISWT), and a cycle ergometer test (CET), within a 2-week period. The tests were performed at least 24 h apart. Standardized encouragement was utilized in each test with the aim of maximizing performance. Heart rate (HR) and dyspnea were measured each minute throughout the tests, and pulse oximetric saturation (Spo(2)) was measured before and immediately after each test. The distances walked in the 6MWT and ISWT were compared to peak oxygen uptake (Vo(2)) values from the CET. RESULTS: HR increased linearly with increasing workload during the CET and ISWT, but increased alinearly with a disproportionate increase early in the 6MWT. In contrast, dyspnea scores increased linearly during the 6MWT, but increased alinearly with a disproportionate increase late during the CET and ISWT. Peak HR and dyspnea were not significantly different between tests. Spo(2) was significantly lower at the end of both walking tests compared to that at the end of the CET (p < 0.001). The distance walked in both the ISWT and 6MWT were related to peak Vo(2) values on the CET (for both tests, r = 0.73; p < 0.001). CONCLUSIONS: The patterns of response in HR and dyspnea seen during the 6MWT suggest that patients with COPD titrate exertion against dyspnea to achieve a peak tolerable intensity. This strategy is not possible in an externally paced ISWT or CET. However, it is a limited strategy, with performance converging at higher workloads. Similar peak exercise responses were achieved in the 6MWT, ISWT, and CET. Greater oxygen desaturation was observed during the field walking tests, suggesting that both the ISWT and 6MWT are more sensitive than the CET in detecting exercise-induced hypoxemia and in assessing ambulatory oxygen therapy needs.     

Use of functional independence measure in rehabilitation of inpatients with respiratory failure

Most outcomes do not deeply express the degree of disability in patients with respiratory failure (RF) following inpatient pulmonary rehabilitation (IPR). The aim of our study was to evaluate the efficacy of an IPR in patients with confirmed COPD and RF using functional independence measure (FIM) that determines the degree of disability experienced by patients and the progress they make during rehabilitation. This scale includes several items: self care, mobility, locomotion, communication and social recognition. Twenty-two patients (age 70+/-2 years, PO(2) 58.18+/-7.63mmHg, PCO(2) 46.82+/-9.11mmHg) were prospectively observed and studied. IPR included respiratory and peripheral muscle training, mucus evacuation techniques, and energy conservation techniques. FIM, Medical Research Council dyspnoea scale (MRC), St. George's Respiratory Questionnaire (SGRQ), and 6-min walking distance (6-MWD) were assessed on admission (pre) and discharge (post) from IPR. After IPR there was a statistically significant improvement (p<0.01) in all the FIM items (total score in self care, mobility, locomotion, social recognition) except for communication. Changes of MRC (pre 4.32+/-0.84; post 3.00+/-1.15, p<0.001), SGRQ (%) (pre 69.86+/-4.62; post 46.50+/-11.94, p<0.001), and 6-MWD (pre 164.54+/-98.63; post 214.32+/-97.64, p<0.001) paralleled those improvements. An inverse correlation between MRC and FIM (r=-0.5042, p=0.016) was observed. Our preliminary study has shown that the benefits of IPR in COPD with RF do not only translate in dyspnoea, exercise capacity and quality of life but also within neuromotor disabilities as assessed by FIM. Our results warrant future studies in pulmonary rehabilitation using FIM as an outcome measure.     

Effect of blood gas derangement on QTc dispersion in severe chronic obstructive pulmonary disease: evidence of an electropathy?

Cardiac arrhythmias are common in patients with respiratory failure from chronic obstructive pulmonary disease (COPD). Several factors may be potentially arrhythmogenic in these patients, including hypoxemia and hypercapnia, acid-base disturbances, cor pulmonale and the use of digitalis, methylxanthines, and sympathomimetic drugs. The aim of this study was to examine the effect of hypoxemia and hypercapnia on QTc dispersion (QTcD) in COPD patients, and to evaluate the effect of a partial correction of one of these pro-arrhythmic factors, the hypoxemia, on Qtc dispersion, as QTcD has been proposed as a marker of heterogeneous repolarization and, hence of ventricular electrical instability. We showed that in 15 hypoxemic/hypercapnic COPD patients, compared to 20 controls, the QTcD was significantly higher (49.7±10.6 vs. 22.9±9.8 ms; P=0.0001); furthermore, after only 24 h of oxygen therapy, and hence after a partial correction of hypoxemia, there was a significant reduction in QTcD in COPD patients (49.7±10.6 vs. 36.3±10.1 ms; P=0.018). The data of the present study suggest that the increase in QTcD may be an early marker of a blood gas mediated electropathy in COPD patients.     

Acute improvement of pulmonary artery pressure by non-invasive positive pressure ventilation in the patients with hypercapnic respiratory failure

It is very important to decrease pulmonary artery pressure (PAP) in patients with chronic obstructive pulmonary disease (COPD) in order to prevent progression to right heart failure. We showed an acute improvement of PAP by non-invasive positive pressure ventilation (NPPV) treatment in patients with hypercapnic respiratory failure. In 26 patients with COPD (18 males and 8 females), physical examination, Doppler echocardiographic evaluation and arterial blood gases analysis were performed on admission and at discharge. PAP was measured by Doppler echocardiography. NPPV was used when 2 of the following were present without contraindications: 1. Respiratory distress with moderate to severe dyspnea, 2. Arterial pH less than 7.35 with PaCO(2) above 45 mmHg, 3. Respiratory rate of 25/minute or greater. Mean age of the patients was 62.6 ± 10.8 year, and mean usage of the NPPV was 12.6 ± 5.5 day. Mean and systolic PAPs of the patients (43.8 ± 16.9 mmHg and 66.7 ± 23.3 mmHg) were significantly decreased with NPPV treatment (26.6 ± 8.4 mmHg, p< 0.0001 and 41.8 ± 14.6 mmHg, p< 0.0001). Also, each parameter of the arterial blood gases was improved significantly with NPPV usage. An echocardiographic assessment in the COPD patients having NPPV treatment due to acute respiratory failure, might be a useful and easy method to show an improvement of PAP as a supportive measure in the management of those patients, in addition to beneficial effects of that treatment on respiratory acidosis, hypercapnia and hypoxemia.     

Mechanisms of improvement in exercise capacity using a rollator in patients with COPD

STUDY OBJECTIVE: We analyzed the effects of the use of a rollator on walking distance and physiologic variables: pulmonary gas exchange, heart rate, minute ventilation (Ve), oxygen saturation, and symptoms during the 6-min walk test (6MWT) in patients with COPD. SETTING: Outpatient clinic at university hospital. PATIENTS: Fourteen patients with COPD in stable clinical condition. One patient had mild COPD, five patients had moderate COPD, six patients had severe COPD, and two patients had very severe COPD. INTERVENTIONS: Two 6MWTs were performed with a portable metabolic system (VmaxST 1.0; Viasys Healthcare; MEDA; Aartselaar, Belgium) with a rollator and without a rollator, in random order. In addition, maximal voluntary ventilation (MVV) was measured with and without a rollator, randomly. RESULTS: The median 6MWT distance increased significantly with a rollator: 416 m without a rollator (interquartile range [IQR], 396 to 435 m), vs 462 m with a rollator (IQR, 424 to 477 m) [p = 0.04]. Significant increases were also seen in oxygen uptake (0.04 L/min [IQR, - 0.002 to 0.09 L/min]); tidal volume (0.06 L/min [IQR, - 0.001 to 0.11 L/min]); and Ve (0.95 L/min [IQR, - 0.67 to 7.1 L/min]), recorded in the last minute of the 6MWT; as well as in MVV (3 L/min [IQR, 0 to 12 L/min]) [p < 0.05 for all]. Borg dyspnea scores tended to be lower with a rollator: 6 (IQR, 4 to 7) without a rollator, vs 5 (IQR, 4 to 7) with a rollator (p = 0.10). The variation in the 6MWT was explained by individual changes in walking efficiency (partial R(2) = 0.31) and changes in Ve (partial R(2) = 0.36) [p model < 0.04]. CONCLUSION: The use of a rollator improves walking distance of patients with COPD through an increased ventilatory capacity and/or better walking efficiency.     

Comparing supplementary oxygen benefits from a portable oxygen concentrator and a liquid oxygen portable device during a walk test in COPD patients on long-term oxygen therapy

BACKGROUND: Differences in oxygen delivery between portable oxygen concentrators (POC) and liquid oxygen (LO) portable units, pose a question if POCs are equally effective as LOs in reducing exercise-induced hypoxaemia. DESIGN: Randomized, single-blind clinical trial. PATIENTS: Thirteen COPD patients (means: age 66+/-11 year, FEV(1) 35.2+/-13.7% predicted) and respiratory failure (means: PaO2 52+/-5mmHg, PaCO2 51.3+/-7.5mmHg). METHODS: All patients underwent a series of 6-min walk tests (6MWT) carried out in random order among one of the three devices: POC, LO cylinder and cylinder with compressed air (CA). Oxygen supplementation was 3lpm for LO and an equivalent to 3lpm in a pulse flow system for POC. RESULTS: The mean SpO2 was equally improved at rest: 92.9+/-2.8% with POC and 91.7+/-2.0% with LO compared to CA-87.8+/-2.7% (POC and LO vs. CA p<0.05). POC and LO significantly improved oxygenation during 6MWT (mean SpO(2) was 84.3+/-5% and 83.8+/-4.2%, respectively) compared to breathing CA-77.6+/-7.4%, p<0.05. Mean 6MWT distance increased with LO (350+/-83m) and POC (342+/-96m) when compared to CA (317+/-84m), however, these differences were not statistically significant. Dyspnoea score assessed at the end of the exercise (Borg scale) was significantly lower when breathing oxygen (4.2+/-1.2 with POC and 4.1+/-1.7 with LO vs. 5.4+/-1.9 with CA, p<0.05). CONCLUSIONS: Effectiveness of oxygen supplementation from a POC did not differ from the LO source during 6MWT in COPD patients with respiratory failure. Oxygen at 3lpm flow was not sufficient to prevent hypoxaemia during strenuous exercise.     

Encouraged 6-min walking test indicates maximum sustainable exercise in COPD patients

STUDY OBJECTIVES: In patients with moderate-to-severe COPD, an encouraged 6-min walking test (6MWT) is a high-intensity submaximal exercise protocol that shows an oxygen uptake (Vo(2)) plateau after the third minute of the test. This last feature prompted the hypothesis that self-paced walking speed is set to achieve "maximal" sustainable Vo(2), namely "critical power" or "critical speed." PATIENTS AND METHODS: Eight patients with moderate-to-severe COPD (mean age, 68 +/- 7 years [+/- SD]; FEV(1), 50 +/- 13% predicted; Pao(2), 69 +/- 8 mm Hg) underwent the following tests on different days in order: (1) encouraged 6MWT; (2) standard incremental shuttle test to identify peak walking speed; (3) four different high-intensity, constant walking speed tests to exhaustion to calculate critical walking speed; and (4) timed walking test at critical walking speed (CWS) to examine sustainability of the exercise. RESULTS: 6MWT and CWS showed similar results (mean of last 3 min): Vo(2) (1,605 +/- 304 mL/min vs 1,584 +/- 319 mL/min), minute ventilation (47 +/- 12 L/min vs 48 +/- 11 L/min), respiratory exchange ratio (0.89 +/- 0.1 vs 0.90 +/- 0.1), heart rate (130 +/- 18 beats/min vs 131 +/- 16 beats/min), Borg dyspnea score (5.4 +/- 1.3 vs 5.5 +/- 2.4), and walking speed (1.49 +/- 0.1 m/s vs 1.44 +/- 0.1 m/s, respectively). CONCLUSION: This study supports that 6MWT indicates maximum sustainable exercise that might be related with its predictive value in COPD patients.     

Effects of high-flow nasal cannula with oxygen on self-paced exercise performance in COPD: A randomized cross-over trial

Introduction:Studies have demonstrated that noninvasive ventilation improves exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). The role of heated humidified high-flow nasal cannula (HFNC) therapy in patients with COPD on self-paced exercise performance remains unclear. Therefore, the purpose of the present study was to determine whether HFNC-aided supplemental oxygen during a 6-minute walk test (6MWT) would change self-paced exercise performance and cardiopulmonary outcomes in patients with stable COPD.Methods:A single-site, cross-over trial was conducted in a pulmonary rehabilitation outpatient department. This study enrolled 30 stable COPD patients without disability. The participants with and without HFNC performed 6MWTs on 2 consecutive days. Outcomes were the distance walked in the 6MWT, physiological, and cardiopulmonary parameters.Results:Those performing HFNC-aided walking exhibited a longer walking distance than those performing unaided walking. The mean difference in meters walked between the HFNC-aided and unaided walking scenarios was 27.3 ± 35.6 m (95% CI: 14.4–40.5 m). The energy expenditure index was significantly lower when walking was aided by HHHNFC rather than unaided (median: 1.21 beats/m walked vs median: 1.37 beats/m walked, P < .001). However, there were no differences in transcutaneous carbon dioxide tension between HHHNFC and non-HHHNFC patients.Conclusion:Walking distance and arterial oxygen saturation improved in stable COPD patients receiving HFNC with additional oxygen support. However, HFNC did not affect transcutaneous carbon dioxide tension and the self-reported dyspnea score during the walking test. The present study demonstrated the feasibility and safety of using HFNC in self-paced exercise.Trial registration:NCT03863821     

Shuttle walking test and 6-minute walking test induce a similar cardiorespiratory performance in patients recovering from an acute exacerbation of chronic obstructive pulmonary disease

BACKGROUND: The incremental shuttle walking test (SWT) has recently been proposed as a more valid and reproducible alternative to the conventional 6-min walking test (6MWT) in the evaluation of exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). OBJECTIVE: To compare the cardiorespiratory performance obtained during two sessions of SWT with that obtained during two sessions of 6MWT. METHODS: We examined 18 patients (forced expiratory volume in 1 s: 48 +/- 14%) recovering from an acute exacerbation of COPD that had required hospitalization. In the same afternoon, each patient performed two SWT and two 6MWT, with an interval of at least 30 min between each test; the sequence of the tests was randomized. RESULTS: Mean walking distance was greater in the second SWT test than in the first SWT. The changes from baseline in systolic blood pressure, heart rate, respiratory rate, oxygen saturation and dyspnea Borg index at the end of the test were similar between the two 6MWT and the two SWT. There was a highly significant correlation between walking distances measured during SWT and during 6MWT (rho: 0.85, p < 0.0005). Neither SWT nor 6MWT correlated with functional data of COPD. CONCLUSIONS: SWT, though being considered to be closer to a submaximal exercise test than 6MWT, does not induce a greater cardiorespiratory performance than 6MWT in patients recovering from acute exacerbation of COPD.     

Daily Passive Muscle Stretching Improves Flow-Mediated Dilation of Popliteal Artery and 6-minute Walk Test in Elderly Patients with Stable Symptomatic Peripheral Artery Disease

BackgroundPatients with peripheral arterial disease (PAD) often have walking impairment due to insufficient oxygen supply to skeletal muscle. In aged rats, we have shown that daily stretching of calf muscles improves endothelium-dependent dilation of arterioles from the soleus muscle and increases capillarity and muscle blood flow during exercise. Therefore, we hypothesized that daily muscle stretching of calf muscles would improve endothelium-dependent vasodilation of the popliteal artery and walking function in PAD patients.MethodsWe performed a randomized, non-blinded, crossover study whereby 13 patients with stable symptomatic PAD were randomized to undergo either 4 weeks of passive calf muscle stretching (ankle dorsiflexion applied 30 min/d, 5 days/wk) followed by 4 weeks of no muscle stretching and vice versa. Endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin-induced dilation of the popliteal artery and 6 minute walk test (6MWT) were evaluated at baseline and after each 4 week interval.ResultsAfter 4 weeks of muscle stretching, FMD and 6MWT improved significantly in the muscle stretching group vs. the control (FMD: 5.1 ± 0.5% vs. 3.7 ± 0.3%, P = 0.005; 6MWT continuous walking distance: 304 ± 43 m vs. 182 ± 34 m; P = 0.0006). No difference in nitroglycerin-induced dilation was found between groups (10.9 ± 1.2 vs. 9.9 ± 0.4%, P = 0.48). Post-stretching, 6MWT total walking distance was positively correlated with normalized FMD (R = 0.645, P = 0.02).ConclusionsPassive calf muscle stretching enhanced vascular endothelial function and improved walking function in elderly patients with stable symptomatic PAD. These findings merit further investigation in a prospective randomized trial.     

Six months of aerobic exercise does not improve microvascular function in type 2 diabetes mellitus

Aims/hypothesis Adults with type 2 diabetes mellitus have impaired microvascular function. It has been hypothesised that microvascular function may be restored through regular exercise. The aim of this study was to investigate whether 6 months of regular aerobic exercise would improve microvascular function in adults with type 2 diabetes. Materials and methods Fifty-nine patients with type 2 diabetes (32 males, age 62.9±7.6 years, HbA_1c 6.8±0.9%) were randomised to either a 6-month aerobic exercise programme (30 min, three times a week, 70–80% of maximal heart rate) or a ‘standard care’ control group. Before and after the intervention period, microvascular function was assessed as the maximum skin hyperaemia to local heating and endothelial and non-endothelial responsiveness following the iontophoretic application of acetylcholine and sodium nitroprusside. Maximal oxygen uptake, as an index of aerobic fitness, was assessed using a maximal exercise test. Results No significant improvement was seen in the exercise group compared with the control group for any of the variables measured: maximal oxygen uptake (control pre: 1.73±0.53 [means±SD] vs post: 1.67±0.40; exercise pre: 1.75±0.56 vs post: 1.87±0.62 l/min, p=0.10); insulin sensitivity (insulin tolerance test) (control pre: −0.17±0.06 vs post: −0.17±0.06; exercise pre: −0.16±0.1 vs post: −0.17±0.07 mmol l⁻¹ min⁻¹, p=0.97); maximal hyperaemia (control pre: 1.49±0.43 vs post: 1.52±0.57; exercise pre: 1.42±0.36 vs post: 1.47±0.33 V, p=0.85); peak response to acetylcholine (control pre: 1.37±0.47 vs post: 1.28±0.37; exercise pre: 1.27±0.44 vs post: 1.44±0.23 V, p=0.19) or to sodium nitroprusside (control pre: 1.09±0.50 vs post: 1.10±0.39; exercise pre: 1.12±0.28 vs post: 1.13±0.40 V, p=0.98). Conclusions/interpretation In this group of type 2 diabetic patients with good glycaemic control a 6-month aerobic exercise programme did not improve microvascular function or aerobic fitness.     

The Use of Pulse Oximetry to Determine Hypoxemia in Acute Exacerbations of COPD

Background: There is little evidence that the guideline-recommended oxygen saturation of 92% is the best cut-off point for detecting hypoxemia in COPD exacerbations. Objective: To detect and validate pulse oximetry oxygen saturation cut-off values likely to detect hypoxemia in patients with aeCOPD, to explore the correlation between oxygen saturation measured by pulse oximetry and hypoxemia or hypercapnic respiratory failure. Methodology: Cross-sectional study nested in the IRYSS-COPD study with 2,181 episodes of aeCOPD recruited between 2008 and 2010 in 16 hospitals belonging to the Spanish Public Health System. Data collected include determination of oxygen saturation by pulse oximetry upon arrival in the emergency department (ED), first arterial blood gasometry values, sociodemographic information, background medical history and clinical variables upon ED arrival. Logistic regression models were performed using as the dependent variables hypoxemia (PaO2 < 60 mmHg) and hypercapnic respiratory failure (PaO2 < 60 mmHg and PaCO2 > 45). Optimal cut-off points were calculated. Results: The correlation coefficient between oxygen saturation and pO2 measured by arterial blood gasometry was 0.89. The area under the curve (AUC) for the hypoxemia model was 0.97 (0.96–0.98) and the optimal cut-off point for hypoxemia was an oxygen saturation of 90%. The AUC for hypercapnic respiratory failure was 0.90 (0.87–0.92) and the optimal cut-off point was an oxygen saturation of 88%. Conclusions: Our results support current recommendations for ordering blood gasometry based on pulse oximetry oxygen saturation cut-offs for hypoxemia. We also provide easy to use formulae to calculate pO2 from oxygen saturation measured by pulse oximetry.     

6-minute walk testing is more sensitive than maximal incremental cycle testing for detecting oxygen desaturation in patients with COPD

STUDY OBJECTIVES: Some respiratory patients exhibit oxygen desaturation during rehabilitative walking but not during maximal cardiopulmonary exercise testing (CPET). We evaluated exercise-induced desaturation during 6-min walk testing (6MWT) in comparison with CPET in patients with COPD and determined the reproducibility of the phenomenon. PATIENTS: We tested 80 consecutive patients with COPD (FEV(1), 62.4 +/- 2% predicted) and 10 patients with supplementary COPD (FEV(1), 59.1 +/- 5% predicted) [mean +/- SEM] to determine the reproducibility. MEASUREMENTS AND RESULTS: First, patients with COPD performed cycle CPET (first CPET [CPET-1]). Three days later, they performed two 6MWTs (first 6MWT [6MWT-1] and second 6MWT [6MWT-2]). Pulse oximetric saturation (SpO(2)) was recorded every minute in both tests. Three groups emerged: desaturation at 6MWT not observed at CPET (DND) [n = 23], desaturation in both tests (n = 16), and no desaturation in either test (n = 41). Second, to evaluate reproducibility, 10 additional subjects with COPD who exhibited desaturation during two successive 6MWTs but not in CPET performed a second CPET (CPET-2) and a single-bout 6MWT (6MWT-3) in a supplementary trial. When two CPETs were performed, lack of O(2) desaturation was noted in both. O(2) desaturation was confirmed in 6MWT-2 and 6MWT-3 (7.4 +/- 1% and 7.4 +/- 1.5%, respectively). CONCLUSION: Twenty-eight percent of patients with COPD presented DND. The phenomenon was reproducible and not protocol dependent, emphasizing the clinical interest of the 6MWT.     

Comparison of volume- and pressure-limited NPPV at night: a prospective randomized cross-over trial

Both pressure- and volume-limited non-invasive positive pressure ventilation (NPPV) have been used in patients with chronic respiratory failure. The aim of the present study was to compare the efficacy of ventilation during nocturnal volume- and pressure-limited NPPV. Fifteen patients (nine COPD, six non-COPD) were randomly assigned to receive either volume-limited or pressure-limited NPPV and were switched to the complementary mode after 6 weeks. Ten patients (five COPD, five non-COPD) completed the study. PaCO2 during sleep comparably decreased from 54.6+/-8.0 to 46.2+/-6.1 mmHg during volume-limited NPPV (P<0.05), and to 46.5+/-6.4 mmHg during pressure-limited NPPV (P<0.05). Improvements in sleep quality assessed by polysomnography were comparable, but less gastrointestinal side effects were reported for pressure-limited NPPV (P<0.05). Using a pneumotachograph the variance of inspiratory volumes was lower, but the variance of peak inspiratory pressures was higher during volume-limited NPPV compared to pressure-limited NPPV. Substantial leak volumes which accounted for 57% (volume-limited NPPV) and for 58% (pressure-limited NPPV) of the applied inspiratory volume were independent from the mode of ventilation. In conclusion, nocturnal volume- and pressure-limited NPPV have similar effects on gas exchange and sleep quality in patients with hypercapnic chronic respiratory failure, but volume-limited NPPV is associated with more gastrointestinal side effects.     

两种运动试验对慢性阻塞性肺疾病患者运动低氧的比较

目的:对比6min步行试验(6MWT)与心肺运动试验(CPET)对慢性阻塞性肺疾病(COPD)患者运动低氧敏感性的差别。方法:选择30例稳定期COPD患者,分别行6MWT与CPET,两个试验的先后顺序随机,比较两种运动试验中运动低氧发生情况的差异。结果:6MWT中运动低氧发生率为46.6%(14/30),CPET中发生运动低氧发生率为50.0%(15/30),两种试验运动低氧的发生率,差异无统计学意义(P=0.796)。运动开始第2min至第6min,6MWT每分钟末脉搏血氧饱和度(SpO2)值低于心肺运动试验(P均0.05)。运动低氧发生时间6MWT(M=2)秒,明显早于CPET(M=8)秒(P=0.01)。结论:6MWT与CPET在COPD患者运动低氧发生率差异无统计学意义,运动低氧发生时间6MWT早于CPET。6MWT是一个简单、可行的COPD患者运动低氧的评价方案。     

精准化运动方案在心脏外科手术患者快速康复中的应用研究

目的：评价无创心输出量监测（ICG）指导下的精准化运动方案在心脏外科手术患者快速康复中的应用价值。方法：纳入2019年3月至2020年3月于中山大学附属第一医院心脏外科二区行心脏手术的80名患者,随机分为对照组和干预组,对照组40例,干预组40例,两组术前及术后（出院前）均进行无创血流动力学监测下的6分钟步行试验（6MWT）,并签署知情同意书。对照组实施常规的运动康复措施,干预组通过6MWT过程中血流动力学的动态变化制定精准化的运动康复方案。比较2组患者的活动耐量、血流动力学指标、住院时间、术后下床时间、术后并发症等指标的差别。结果：1.干预组的活动耐量提高（6分钟步行试验距离（6MWD）430.48±54.62米VS 401.80±35.16米,P<0.05）、活动代谢当量（4.75±0.85 METS VS 4.03±0.54 METS,P<0.05）2.干预组的住院时间（29.57±7.24天VS 35.50±9.87 天,P<0.05）、术后下床时间（1.88±0.46天VS 2.15±0.43天,P<0.05）显著缩短。3.两组康复运动过程中的并发症：干预组患者在围术期实施康复运动过程中无发生并发症,对照组患者发生心律失常2例,其中房颤1例（2.5%）,室性早搏1例（2.5%）,呼吸困难2例（5%）,气促2例（5%）,血氧下降1例（2.5%）。结论：无创心输出量监测和6分钟步行试验联合指导下的精准化运动康复方案,可以大幅度地促进心脏外科手术患者的快速恢复。     

Long-term controlled trial of nocturnal nasal positive pressure ventilation in patients with severe COPD

STUDY OBJECTIVES: To determine the 1-year efficacy of noninvasive positive pressure ventilation (NPPV) added to long-term oxygen therapy (LTOT) in patients with stable severe COPD. PATIENT SELECTION AND METHODS: We prospectively randomized 52 patients with severe COPD (FEV(1) < 45%) to either NPPV plus "standard care" (96% patients with LTOT) or to standard care alone (93% patients with LTOT). The outcomes measured included the following: rate of acute COPD exacerbations; hospital admissions; intubations; and mortality at 3 months, 6 months, and 12 months. The patients were also evaluated at 3 months and 6 months for dyspnea using the Medical Research Council and Borg scales, gas exchange, hematocrit, pulmonary function, cardiac function with echocardiogram, and neuropsychological performance. RESULTS: One-year survival was similar in both groups (78%). The number of acute exacerbations was similar at all time points in patients receiving NPPV, compared with control subjects. The number of hospital admissions was decreased at 3 months in the NPPV group (5% vs 15% of patients, p < 0.05), but this difference was not seen at 6 months (18% vs 19%, respectively). The only beneficial differences were observed in the Borg dyspnea rating, which dropped from 6 to 5 (p < 0.039), and in one of the neuropsychological tests (psychomotor coordination) for the NPPV group at 6 months. CONCLUSIONS: Our study indicates that over 1 year, NPPV does not affect the natural course of the disease and is of marginal benefit in outpatients with severe COPD who are in stable condition.     

The Effect of Continuous Positive Airway Pressure on Stair-Climbing Performance in Severe COPD Patients

Abstract

Stair climbing is associated with dynamic pulmonary hyperinflation and the development of severe dyspnea in patients with chronic obstructive pulmonary disease (COPD). This study aimed to assess whether (i) continuous positive airway pressure (CPAP) applied during stair climbing prevents dynamic hyperinflation and thereby reduces exercise-induced dyspnea in oxygen-dependent COPD-patients, and (ii) the CPAP-device and oxygen tank can be carried in a hip belt. In a randomised cross-over design, oxygen-dependent COPD patients performed two stair-climbing tests (44 steps): with supplemental oxygen only, then with the addition of CPAP (7 mbar). The oxygen tank and CPAP-device were carried in a hip belt during both trials.

Eighteen COPD patients were included in the study. Although all patients could tolerate stair climbing with oxygen alone, 4 patients were unable to perform stair climbing while using CPAP. Fourteen COPD patients (mean FEV₁ 36 ± 14% pred.) completed the trial and were analyzed. The mean flow rate of supplemental oxygen was 3 ± 2 l/min during stair climbing. Lung hyperinflation, deoxygenation, hypoventilation, blood lactate production, dyspnea and the time needed to manage stair climbing were not improved by the application of CPAP (all p > 0.05). However, in comparison to climbing with oxygen alone, limb discomfort was reduced when oxygen was supplemented with CPAP (p = 0.008).

In conclusion, very severe COPD patients are able to carry supporting devices such as oxygen tanks or CPAP-devices in a hip belt during stair climbing. However, the application of CPAP in addition to supplemental oxygen during stair climbing prevents neither exercise-induced dynamic hyperinflation, nor dyspnea.     

Benefits of oxygen on exercise performance and pulmonary hemodynamics in patients with COPD with mild hypoxemia

STUDY OBJECTIVES: To clarify the effects of oxygen on exercise performance and pulmonary hemodynamics during exercise in patients with COPD with mild hypoxemia at rest. DESIGN: Seventy-five male patients with stable COPD ("pink puffer" type), accompanied by mild hypoxemia (> 60 mm Hg) at rest and with mild (percentage of predicted FEV1 [%FEV1] > 50%, n = 16), moderate (%FEV1 > 35% to < or = 50%, n = 25), and severe (%FEV1 < or =35%, n = 34) airflow obstruction were recruited from an outpatient clinic. A 6-min walking distance (6MD) test was administered to 75 patients, and the pulmonary hemodynamics of 43 subjects were determined during exercise on a supine bicycle ergometer at 25 W and breathing compressed air and oxygen at 2 L/min. RESULTS: Supplemental oxygen resulted in a significant increase in 6MD, except for patients with mild airflow obstruction and mild desaturation. This increase in 6MD produced by oxygen was greater as the restriction of the airflow was more severe, and correlated negatively with %FEV1, but not with PaO2 at rest or exercise hypoxemia. Pulmonary artery pressure (Ppa) and pulmonary artery occlusion pressure (Pop) increased with exercise, while the rates of increase in both types of pressure were significantly higher for severe COPD than for mild COPD and moderate COPD. Oxygen inhalation significantly reduced the increases in Ppa and Pop during exercise in patients with moderate-to-severe COPD, and the effect of oxygen on the increase in Pop correlated positively with airtrapping (vital capacity - FVC). CONCLUSION: These findings suggest that supplemental oxygen benefits patients with COPD with moderate-to-severe airflow obstruction and mild hypoxemia at rest, as reflected in improvement in exercise performance and pulmonary hypertension during exercise.