Analysis of the metabolic and ventilatory response to self-paced 12-minute treadmill walking in patients with severe chronic obstructive pulmonary disease

Differential impacts between fat mass index and fat-free mass index on patients with COPD

BACKGROUND

Differences in the clinical impacts of fat mass index (FMI) and fat-free mass index (FFMI) remain unclear in patients with chronic obstructive pulmonary disease (COPD). We hypothesized that FMI and FFMI have different impacts on 1) emphysema and 2) pulmonary function and health-related quality of life of COPD patients.

METHODS

Patients with COPD (n = 228), enrolled in a multicenter prospective 3-year cohort were classified into four groups based on baseline median FMI and FFMI values. Emphysema assessed as the ratio of low attenuation area to total lung volume (LAA%) on computed tomography, pulmonary function, and health-related quality of life assessed using the St. George's Respiratory Questionnaire (SGRQ) were compared.

RESULTS

The four groups had statistically significant differences in LAA%, pulmonary function, and SGRQ scores. The Low FMI Low FFMI group exhibited the highest LAA%, lowest pulmonary function, and worst SGRQ scores among the four groups. In addition, these differences were consistent over 3 years. Multivariate analysis showed that low FMI was associated with high LAA%, low inspiratory capacity/total lung capacity (IC/TLC), and carbon monoxide transfer coefficient (KCO). In contrast, low FFMI was associated with these factors as well as worse SGRQ scores.

CONCLUSION

FMI and FFMI have different effects on the clinical manifestations of COPD. Both low fat and muscle mass contributed to severe emphysema, whereas only low muscle mass contributed to worse health-related quality of life in patients with COPD.

Ventilatory constraint is more severe in walking than cycling in patients with COPD

Due to its effectivity in assessing functional capacity and adding prognostic information to the staging of chronic obstructive pulmonary disease (COPD) patients, the 6-min walk test (6MWT) is extensively used in clinical evaluation. Currently, there is little information about the physiological response this test elicits in patients, especially when compared to cardiopulmonary exercise test (CPET). The aim of the study was to compare ventilatory and metabolic responses between these tests commonly used for the assessment of clinical outcome. A group of 20 patients with moderate to very severe COPD were tested for their pulmonary function (flow-volume curve, static lung volumes), occlusion mouth pressures and breath-by-breath measurement of flow, volumes, and oxygen (O₂) and carbon dioxide (CO₂) concentration during the 6MWT and CPET. All parameters measured during both exercise tests were assessed over the throughout of the tests and compared between each other at specified time points. Serially measured inspiratory vital capacity (IVC) decreased more rapidly and extensively during the walk-test (p ​< ​0,0001). This was accompanied by a limited increase in tidal volume (V_T) and minute ventilation (V_E), which were significantly lower in the course of the 6MWT (p ​= ​0,0003 and p ​= ​0,0097, respectively). We also noticed a significant decrease in hemoglobin oxygen saturation (SpO₂) during the 6MWT which was correlated to percent decrease in IVC (p ​= ​0,0206). Over the course of the 6MWT, oxygen consumption (VO₂) and V_T reached plateau within 2 ​min, while carbon dioxide production (VCO₂) and V_E within 3 ​min. During CPET, VO₂, VCO₂ and V_E rose continuously, while V_T reached plateau within 4 ​min. The 6MWT seems to be a rather endurance-based test associated with more pronounced dynamic lung hyperinflation and mechanical constraint of ventilation in comparison to cycling.

•

Various types of exercise are tolerated differently.

•

The 6MWT is, as opposed to ergometry, accompanied by a quicker increase in dynamic lung hyperinflation and desaturation.

•

It seems that pedaling, as compared to walking, is the superior way of training movement for rehabilitation purposes.

Two-step stool aerobic training for smokers

OBJECTIVE

The aim of this study was to analyze subjective, physical, and physiologic responses to a standardized incremental 30-min two-step stool test to create an individualized 45-min maximally intensive two-step stool endurance exercise regimen for home training.

DESIGN

This is a longitudinal study on 26 consecutively referred male smokers aged 39-66 yrs. Each performed the two-step stool test on two 15-cm steps at 10, 20, 30, 40, 50, and 60 climbs per minute. Exertional dyspnea, oxygen consumption per unit time, ventilation, respiratory rate, tidal volume, heart rate, capillary oxyhemoglobin saturation, physiologic cost index, and oxygen pulse were recorded and compared with those observed during incremental cycle exercise (30 W per 3 mins). Multivariate analysis for each parameter was undertaken as a mixed model.

RESULTS

All subjects attained 60 climbs per minute on the two-step stool test and performed 38-42 mins of two-step stool endurance. All parameters reached 80%-96% of cycle maximum oxygen consumption. The subjects found the two-step stool endurance simple and practical to perform at home. There were no complications.

CONCLUSIONS

The incremental two-step stool test is a simple, cost-effective way to establish a 45-min maximally intensive endurance exercise training program practical for use in the home.

Relation between physical capacity, nutritional status and systemic inflammation in COPD

BACKGROUND

Decreased physical capacity, weight loss, fat-free mass depletion and systemic inflammation are frequently observed in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVE

Our aim was to examine relations between physical capacity, nutritional status, systemic inflammation and disease severity in COPD.

METHOD

Forty nine patients with moderate to severe COPD were included in the study. Spirometry was preformed. Physical capacity was determined by a progressive symptom limited cycle ergo meter test, incremental shuttle walking test, 12-minute walk distance and hand grip strength test. Nutritional status was investigated by anthropometric measurements, (weight, height, arm and leg circumferences and skinfold thickness) and bioelectrical impedance assessment was performed. Blood samples were analyzed for C-reactive protein (CRP) and fibrinogen.

RESULT

Working capacity was positively related to forced expiratory volume in 1 s (FEV(1) ) (p < 0.001), body mass index and fat free mass index (p = 0.01) and negatively related to CRP (p = 0.02) and fibrinogen (p = 0.03). Incremental shuttle walk test was positively related to FEV(1) (p < 0.001) and negatively to CRP (p = 0.048). Hand grip strength was positively related to fat free mass index, and arm and leg circumferences. Fifty to 76% of the variation in physical capacity was accounted for when age, gender, FEV(1) , fat free mass index and CRP were combined in a multiple regression model.

CONCLUSION

Physical capacity in chronic obstructive pulmonary disease is related to lung function, body composition and systemic inflammation. A depiction of all three aspects of the disease might be important when targeting interventions in chronic obstructive pulmonary disease.

Physiologic Responses to Incremental and Self-Paced Exercise in COPD

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.

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.

[Chronic obstructive pulmonary disease: evaluation of exercise tolerance using three different exercise tests]

The clinical usefulness of simple exercise tests in patients with chronic obstructive pulmonary disease (COPD) continues to give rise to debate. Questions remain about whether these tests assess maximum effort or only exercise tolerance (submaximal effort). To determine the levels of stress reached during the six-minute walking (6MW) test and stair climbing (SC) test and their relation to maximum aerobic capacity, 50 patients with COPD (FEV1 49 +/- 19%) were studied. Data collected included spirometric variables and VO2, heart rate (HR), ventilatory response and dyspnea during the progressive effort ergometric cycle (PEEC) test. Two 6MW and SC tests were completed on two separate days, with distance, number of steps, HR and dyspnea recorded. HR was higher during the PEEC test. Among the simple tests, SC caused a faster HR than did the 6MW test. Likewise, a significant linear relation was observed between VO2/kgpeak during the 6MW test (r2 = 0.27; p < 0.05) and the SC test (r2 = 0.33; p < 0.01). We therefore conclude that exercise tolerance in patients with COPD can be evaluated using simple stress tests. The SC test is probably the best simple way to determine maximum functional capacity, whereas the 6MW test can be reserved for measurement of exercise tolerance.

Tissue depletion and health related quality of life in patients with chronic obstructive pulmonary disease

The relationship between tissue depletion and decreased exercise performance has been well established in patients with COPD. In this study we investigated the influence of the pattern of tissue depletion on health related quality of life (HRQL) and their mutual relationship with exercise capacity and dyspnoea. Patients with low body weight and/or low fat-free mass (FFM; using bioelectrical impedance) were categorized in three groups according to type of tissue depletion: loss of both FFM and fat mass (FM), and loss of FFM or FM only. Handgrip strength (HGS) was used as a functional outcome measure of tissue depletion. Exercise performance was assessed by 12 min walking distance (12MWD) and dyspnoea by visual analogue scale (VAS). HRQL was measured with the St George's Respiratory Questionnaire (SGRQ) and the Medical Psychological Questionnaire for Lung diseases (MPQL). Patients with depletion of FFM irrespective of body weight showed greater impairment in 12MWD, HGS, the 'activity' and 'impact' scores of the SGRQ and the domain 'invalidity' of the MPQL, in comparison with depleted patients with relative preservation of FFM. Exercise performance and dyspnoea were also significantly related to these subscores of HRQL. In addition, dyspnoea related significantly to the domain 'symptoms' of the SGRQ. Tissue depletion pattern remained significantly related to SGRQ-scores and the domain 'invalidity' of the MPQL when dyspnoea and walking distance were added to the model as a covariates. Tissue depletion is an important determinant of HRQL independent of exercise capacity and dyspnoea.