Chest ACCP Member Benefits
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Guest Access | Sign In via User Name/Password
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (20)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Poulain, M.
Right arrow Articles by Préfaut, C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Poulain, M.
Right arrow Articles by Préfaut, C.
(Chest. 2003;123:1401-1407.)
© 2003 American College of Chest Physicians

6-Minute Walk Testing Is More Sensitive Than Maximal Incremental Cycle Testing for Detecting Oxygen Desaturation in Patients With COPD*

Magali Poulain, PhD; Fabienne Durand, PhD; Bernard Palomba, PT; François Ceugniet, MD; Jacques Desplan, MD; Alain Varray, PhD and Christian Préfaut, MD

* From the Clinique du Souffle "La Solane" (Drs. Poulain, Palomba, Ceugniet, and Desplan), Osséja; UPRES-EA 701 Physiologie des Interactions (Dr. Préfaut), Service de Physiologie Clinique, Hôpital Arnaud de Villeneuve, Montpellier; UPRES-EA Sport (Dr. Varray), Performance, Santé, Faculté des Sciences du Sport, Montpellier; and Laboratoire Sport (Dr. Durand), Santé, Altitude, Département STAPS l’Ermitage, Font-Romeu, France.

Correspondence to: Magali Poulain, PhD, Clinique du Souffle "La Solane," 19 rue des Casteillets 66340 Osséja, France; e-mail: mpoulain{at}aol.com


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
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 (FEV1, 62.4 ± 2% predicted) and 10 patients with supplementary COPD (FEV1, 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 (SpO2) 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 O2 desaturation was noted in both. O2 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.

Key Words: COPD • oxygen desaturation • 6-min walking test


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Conclusion
 References
 
Patients with COPD have reduced exercise tolerance.1 This exercise intolerance and its associated dyspnea are primarily due to airway obstruction but also to a combination of several factors.2 3 Peripheral muscular dysfunction has been demonstrated in this population, and although the degree of its impact on exercise capacity and dyspnea has not been established with certainty,4 5 rehabilitation programs that include exercise training are able to reduce dyspnea and improve exercise tolerance.6 In order to prescribe optimal exercise, however, patients with COPD must first be evaluated, and cardiopulmonary exercise testing (CPET) is most often recommended to assess the level and mechanisms of exercise intolerance and to determine individualized training intensity.7 The diagnosis of exercise-induced desaturation during this CPET is important not only in terms of pathophysiology but also potentially for therapeutics. Surprisingly, we recently observed that several respiratory patients who did not exhibit O2 desaturation during CPET performed prior to rehabilitation paradoxically showed regular O2 desaturation during the walking component of the rehabilitation program.

O2 desaturation has been studied during different types of exercise testing. PaO2 fell to a lower level during treadmill exercise compared with bicycle exercise in patients with chronic obstructive airway disease.8 Palange et al9 compared walking and cycling exercise tests in patients with COPD and demonstrated that PaO2 values were lower during walking. This study, however, used a shuttle test, which in fact is a field incremental maximal exercise test and not a pure walking test. Therefore, no data in the literature were found to specifically confirm our clinical observation.

This study was designed to determine whether exercise-induced desaturation appears in some patients with COPD during walking but not during maximal incremental cycle exercise. In order to evaluate exercise-induced desaturation during walking, we used 6-min walk testing (6MWT), which is well known for its clinical interest, simplicity, and reproducibility.10 11 In a population of 80 consecutive patients with COPD, we evaluated the prevalence of exercise-induced desaturation during 6MWT in comparison with maximal cycle CPET. In addition, the reproducibility of the phenomenon was tested.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Conclusion
 References
 
Patients
Eighty consecutive respiratory patients, 44 men and 36 women, admitted to a medical rehabilitation center (Clinique du Souffle "La Solane"; Osséja, France) participated. All these patients presented clinical histories consistent with COPD. The mean age (± SEM) was 60.6 ± 1 years, height was 165 ± 0.009 cm, weight was 74.7 ± 1.6 kg, body mass index (BMI) was 27.3 ± 0.5, and FEV1 was 1.65 ± 0.06 L (62.4 ± 2% predicted; range, 37 to 86%). According to the recent American Thoracic Society criteria,12 our patients presented moderate (stage IIA) airway obstruction. Fifty-three patients had a history of smoking, 7 patients were currently smoking, and 46 patients had stopped smoking. The patients were in a clinically stable state and had no recent infectious exacerbations. No patients were receiving long-term oxygen therapy. The aim of the study was fully explained to them, and all gave written consent to participate. Study participation began 3.2 ± 0.3 days after admission to the center. Ten supplementary subjects participated in this study in addition to the 80 subjects; their mean age was 66.5 ± 2 years, height was 163 ± 0.02 cm, weight was 79.9 ± 2.3 kg, BMI was 30.3 ± 1.43, and FEV1 was 1.42 ± 0.15 L (59.1 ± 5% predicted).

Lung Function
Lung function measurements were performed using a plethysmograph (V6200 Autobox; SensorMedics; Yorba Linda, CA) to determine total lung capacity (TLC), FVC, and FEV1. The Tiffeneau ratio (FEV1/FVC) was then calculated.

CPET and Cardiopulmonary Parameters
The maximal exercise test was performed on a cycle ergometer (Ergometrics 900; Ergoline; Bitz, Germany) following the individualized protocol usually used in our laboratory. Briefly, we calculated the maximal predicted power output from the predicted maximal oxygen uptake (O2max) according to the Wasserman equation for theoretical values.13 We then calculated the estimated O2max for a given subject by multiplying the predicted O2max by FEV1 percentage of predicted. Estimated O2max was then converted to estimated maximal power (Wmax). The 3-min warm-up was conducted at 20% of estimated Wmax, and the load was increased by 8% of estimated Wmax every minute to obtain Wmax output in approximately 10 min. O2max was assumed to have been reached if three of the four following criteria were met: (1) leveling off of oxygen uptake (O2) despite increasing load, (2) respiratory exchange ratio (RER) > 1.1, (3) attainment of age-predicted maximal heart rate (HRmax) [210 - 0.65 x age], and (4) inability of the subject to maintain the pedaling frequency despite maximal effort and verbal encouragement. If three criteria were not observed but at least the increase in RER was recorded, we considered that the O2max was symptom limited.

During exercise testing, gas exchanges were measured continuously using a breath-by-breath automated exercise metabolic system (max series 29C; SensorMedics). The subjects breathed through a mouthpiece with a noseclip in place. Before each test, the volume was calibrated by five inspiratory and expiratory strokes with a 3-L pump at different flow levels, and then the gas analyzers were calibrated with two gas mixtures of known O2 and CO2 concentration. Expired gases were analyzed for O2 with a zirconia solid electrolyte O2 analyzer and for CO2 with an infrared analyzer. O2, CO2 output, RER, minute ventilation, and its components tidal volume and breathing frequency were averaged during the last 20 s of each load. A 12-lead ECG (Cardiosoft Corina; Marquette Hellige Medical Systems; Freiburg, Germany) was monitored continuously during testing.

6MWT
6MWT was performed twice (first 6MWT [6MWT-1] and second 6MWT [6MWT-2]) with at least 15 min between tests to allow heart rate (HR) to return to its initial rest value. Subjects were asked to walk at their own maximal pace along a perimeter of 31.5 m. They were asked to cover as much ground as possible while maintaining a steady pace without running during the allotted time. No encouragement was given, and subjects were informed each minute of the time remaining. The patients were allowed to stop, but they could start again, if possible, within the allocated 6 min. Distance covered in 6 min, oxygen saturation, and HR, which was measured by a Sport Tester (Polar; Kempele, Finland) every minute, were recorded. The dyspnea score measured on a visual analog scale before and at the end of the test was also recorded to determine if scores had returned to initial values by the beginning of 6MWT-2. 6MWT-2 values were always better than those of 6MWT-1; 6MWT-2 values are reported.

O2 Desaturation and Blood Gas Analysis
Pulse oximetric saturation (SpO2) was measured during both tests using pulse oximetry (Nonin 8500 M; Nonin Medical; Minneapolis, MN). Desaturation was defined as a fall >= 4% of the resting SpO2 value during at least the last 3 min of the cycling or walking tests.14 To estimate blood gas levels during the cycle test, arterialized blood was collected at the ear lobe at rest, and maximal exercise and samples were immediately analyzed for PaO2, PaCO2, and pH (BGE; Instrumentation Laboratory; Milan, Italy).

Protocol
O2 Desaturation Comparison:
On the first day of the study, subjects underwent lung plethysmography and resting ECG and performed their first CPET (CPET-1) on a cycle ergometer. SpO2 was recorded throughout exercise, and arterialized blood gas levels were recorded at rest and maximal load. One to three days after CPET-1, subjects performed 6MWT-1 and 6MWT-2, during which SpO2, HR, and dyspnea were recorded.

Reproducibility of the Phenomenon:
To evaluate the reproducibility of the phenomenon, a supplementary trial was held. Ten subjects who were not part of the original study group of 80 members, but who exhibited arterial desaturation during two successive 6MWT but not during CPET, performed a second CPET (CPET-2) and a single-bout 6MWT (6MWT-3). CPET-2 and 6MWT-3 were performed in the same protocol conditions as in the first stage (9 ± 1 days and 6 ± 1 days, respectively, after the first test). SpO2 and HR were recorded continuously during both tests, while arterialized blood gases were drawn at rest and during the last 20 s of cycling exercise.

Statistics
The results are expressed as mean ± SEM. We used a one-way analysis of variance to compare anthropometric, plethysmographic, and gas exchange data. A stepwise multiple regression analysis was used to evaluate independent variables explaining the variance of desaturation in 6MWT.

Variation coefficients were calculated to compare the two CPETs and 6MWT-2 and 6MWT-3. One-way repeated-measure analyses of variance were used to compare kinetic values of SpO2 between the two CPETs and the two 6MWTs. Statistical analysis was performed using a statistical software package (SigmaStat 2.03; Jandel Scientific; Erkrath, Germany); p < 0.05 was considered significant.


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Conclusion
 References
 
O2 Desaturation Comparison
No between-group difference was noted for resting levels of SpO2 (Table 1 ). 6MWT was performed 2.5 ± 0.5 days after the CPET. The fall in SpO2 measured between rest and the last stage of exercise is reported in Figure 1 . These data allowed us to determine three different groups.


View this table:
[in this window]
[in a new window]

  		Table 1. Anthropometric, Plethysmographic, and Gasometric Characteristics at Rest in 80 Patients With COPD*

 


View larger version (34K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1. Fall in SpO2 between rest and end of CPET and 6MWT in NN patients (narrow horizontal lines), DND patients (broad horizontal lines), and DD patients (vertical lines). *Fall in SpO2 > 4%.

 
The first group showed desaturation at 6MWT that was not observed at CPET (DND). The DND group comprised 23 subjects (28.75% of the total population). The desaturation in SpO2 (fall of 7 ± 0.4%) as previously defined persisted 5.08 ± 0.1 min during 6MWT. The second group showed desaturation during both 6MWT and CPET (DD). The DD group comprised 16 subjects (20% of the total population). The desaturation in SpO2 (fall of 6.66 ± 0.76%) persisted 5 ± 0.1 min during 6MWT and 4.3 ± 0.3 min during CPET. The third group showed no desaturation during either 6MWT or CPET (NN). The NN group comprised 41 subjects (51.25% of the total population). In CPET, there was no significant difference between the falls in SpO2 and the falls in capillary arterial oxygen saturation (SaO2) [DND, 2.78 ± 0.3% vs 2.5 ± 0.5%; DD, 6.6 ± 0.76% vs 6.4 ± 1.5%; and NN, 2.02 ± 0.4% vs 1.7 ± 0.3%, respectively, for SpO2 and capillary SaO2].

There was no significant between-group difference for age, weight, height, BMI, and FEV1. Significant difference was noted in NN vs DD for FEV1/FVC, and for TLC in NN vs DD and in DND vs DD (p < 0.05; Table 1 ).

Table 2 shows no between-group difference in symptom-limited O2 (expressed in liters per minute) and symptom-limited O2 (expressed in percentage of predicted). Wmax, HRmax, HR at ventilatory threshold, and dyspnea were the same in the three groups. No difference was noted for distance covered in 6MWT and HR at the end of the test, but NN showed a tendency toward decreased HR measured at the end of 6MWT compared with DND and DD. In the stepwise multiple regression analysis performed to explain the desaturation, HR at the end of 6MWT was retained in DND (r = 0.64, F = 6.32, p < 0.05), and distance and HR at the end of 6MWT was retained in DD (r = 0.70, F = 4.01, p < 0.05).


View this table:
[in this window]
[in a new window]

  		Table 2. CPET-1 and 6MWT-2 Parameters in 80 Patients With COPD*

 
Reproducibility of the Phenomenon
There were no significant differences between the 10 supplementary subjects and the DND group for age, weight, height, or FEV1. In the supplementary trial, no significant difference was noted for any variable between either CPET or 6MWT. These results were confirmed using the variation coefficient (Table 3 ). Figure 2 shows the kinetics of SpO2 at three times: at rest, at the middle of exercise, and at the end of exercise for the two exercise tests and the repetitions of both. The lack of O2 desaturation was therefore confirmed in CPET-2, and 6MWT-3 confirmed the O2 desaturation for walking exercise.


View this table:
[in this window]
[in a new window]

  		Table 3. Reproducibility for CPET and 6MWT in 10 Patients With COPD Who Presented DND*

 


View larger version (13K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2. Kinetics of SpO2 at rest (T 0), mid-exercise (T 1), and end-exercise (T2) for CPET-1 ({circ}), CPET-2 (•), 6MWT-2 ({triangleup}), and 6MWT-3 ({blacktriangleup}) in 10 patients with COPD. **Significant difference with preceding level of test (p < 0.001). §Significant difference between rest and end of exercise (p < 0.05).

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Conclusion
 References
 
This study essentially shows the following: (1) 28% of patients with COPD present DND, and (2) this phenomenon is reproducible.

O2 Desaturation Definition
We defined O2 desaturation as a fall in SpO2 of > 4% below resting value that persists for at least the last 3 min of the exercise test. The fall of 4% was validated in a study of exercise-induced hypoxemia in athletes.14 This 4% fall was defined as a fall of 2% to account for potential inaccuracy of oximetry plus another fall of 2% to account for the right shift of the hemoglobin saturation curve induced by exercise metabolic acidosis. To avoid an artifactual drop in SpO2, the fall of 4% was retained when it persisted for at least 3 consecutive min during exercise.14 In this study, the average fall in SpO2 was approximately 75% greater than the minimal fall defined, and the average time was approximately 70% longer than the minimal time defined.

Evidence of the Phenomenon and Reproducibility
Our study highlights three types of SpO2 response to exercise. Exercise-specific responses have already been suggested by Palange et al9 and Cockroft et al,8 who showed different O2 desaturation values during walking and cycling exercise. Although these studies suggested the existence of a specific DND population, this is the first time to our knowledge that desaturation is reported during a walking test vs a maximal cycle test. A relatively impressive number of subjects showed this phenomenon, and it was thus important to determine its reproducibility. No significant difference was noted between the variables of CPET and 6MWT-2 and 6MWT-3, and this finding was strengthened by the low variation coefficient. These results confirm a study by Covey et al,15 who showed the reliability of two symptom-limited exercise tests performed approximately 2 weeks apart and a study by Guyatt et al,10 who showed the reproducibility of 6MWT. The fact that we found the same results in 6MWT-2, the reference test, and 6MWT-3, which was a single-bout exercise, excluded a potential effect of exercise repetition on O2 desaturation and indicated that the phenomenon was not protocol dependent. In all, 28% of our total COPD population showed DND, and the reproducibility of this phenomenon was confirmed in 10 other patients. 6MWT therefore seems to have more clinical interest than expected. It is currently a valid tool to measure the functional status of patients, reflect their capacity to undertake day-to-day activities, and assess the effectiveness of therapies such as pulmonary rehabilitation. Our results suggest that 6MWT may also have the potential to become a diagnostic test as well, either to measure dynamic hyperinflation as demonstrated by Marin et al,16 or to unmask exercise-induced desaturation as shown in this work. 6MWT does not negate the need for CPET to assess the level and mechanisms of exercise intolerance, to detect cardiac failure, and to determine individual training intensity. 6MWT and CPET are complementary tests, but our study suggests that limiting 6MWT use only to investigating exercise tolerance may need to be reconsidered.

Hypotheses for the Phenomenon
Several hypotheses can be advanced to explain the DND: (1) the walking distance covered; (2) walking distance in relation to severity of obstruction; (3) the greater muscle mass involved in walking than in cycling; (4) the type of exercise, rectangular or triangular; or (5) the difference in ventilatory demand and/or breathing pattern reported between walking and cycling. No significant between-group difference was noted in the walking distance in 6MWT. Our three groups covered approximately the same distance, whereas only the DD group and the DND group showed O2 desaturation during the walk. In the DD group, the distance covered in association with the HR at the end of the test explained 50% of the variability in the O2 desaturation. The DND group showed a trend toward greater walking distance of approximately 40 m, although distance did not explain the variability in O2 desaturation for this group, which confirms the report of Mak et al17 that O2 desaturation during walking is not correlated with distance.

It has been reported that FEV1 impairment and perceived breathlessness are correlated with walking distance in patients with COPD.17 The patients of the DND and DD groups, who showed a tendency toward more greatly impaired FEV1 than the NN group and the same maximal dyspnea, covered the same distance as the NN group, which suggests that FEV1 was not the main factor to explain the distance covered. Our results confirmed those of Troosters et al,18 who reported that FEV1 is not implicated in the equation prediction of walking distance. DD patients presented a lower FEV1/FVC ratio and greater TLC than DND patients, however, which suggests that the desaturation in DD patients in all tests could be explained by the specific pathophysiology, ie, emphysema.

During exercise testing, the muscle mass involved in running with a treadmill protocol is greater than in cycling with a cycle ergometer protocol.19 The greater muscle mass involved in running could increase muscular O2 extraction, thereby inducing a substantial decrease in venous pressure of O2.19 We do not, however, know whether the muscle mass used during high-intensity walking is greater than during cycling in patients with COPD.

In any case, the patients were at approximately 91% of their HRmax from the second minute of 6MWT, which indicates that this test is rectangular. The cycle test is triangular, and the patients maintained the same HR until 2 min before the end of testing. Therefore, even though the intensity was maximal during the cycle test, a higher submaximal intensity was maintained for a longer period during 6MWT, which may indicate higher O2 demand20 and thus lower venous pressure of O2.

Ventilatory demand may differ with different types of activity, and breathing pattern may thus differ as well. Triathletes exhibiting exercise-induced desaturation were noted to have a different ventilatory pattern in running compared with cycling.21 During a shuttle test in patients with COPD, Palange et al9 showed an increase in physiologic dead space/tidal volume ratio, which is consistent with the observations in triathletes. The type of activity (ie, walking vs cycling) may affect the occurrence of desaturation.

Celli et al22 and Delgado et al23 further showed that the arm muscles are active during walking exercise in some patients with COPD and this might be a source of reflex impulses to the respiratory centers, leading to dissynchronous breathing and thereby impairing gas exchange. In this study, however, we did not measure breathing pattern or ventilatory demand during the walking test, and further studies are needed. Another point that should be mentioned is that cycling was an unfamiliar form of exercise for our patients. Several studies have reported a higher ventilatory demand in patients with COPD during cycling exercise as compared with walking.8 24 The association of this hyperventilation and the possible favorable breathing pattern during cycling could explain the lack of O2 desaturation observed during the cycle test.


   Conclusion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
References
 
In conclusion, this study clearly showed that 28% of patients with COPD presented DND. This phenomenon was reproducible and not protocol dependent, suggesting a broader range of clinical applications for 6MWT. The mechanisms of this phenomenon remain unknown, but our data suggest they are multifactorial. Because desaturation during walking exercise could lead to the prescription of O2 de-ambulation, further investigation is needed to better understand our findings and possibly to improve the rehabilitation programs of patients with COPD.


   Acknowledgements
 
The authors thank Anne Cotxet and José Cabézudo for technical assistance, and Cathy Carmeni for linguistic revision of the manuscript.


   Footnotes
 
Abbreviations: BMI = body mass index; CPET = cardiopulmonary exercise testing; CPET-1 = first cardiopulmonary exercise testing; CPET-2 = second cardiopulmonary exercise testing; DD = desaturation during both 6-min walk testing and cardiopulmonary exercise testing; DND = desaturation at 6-min walk testing not observed at cardiopulmonary exercise testing; HR = heart rate; HRmax = maximal heart rate; NN = no desaturation during either 6-min walk testing or cardiopulmonary exercise testing; RER = respiratory exchange ratio; SaO2 = arterial oxygen saturation; 6MWT = 6-min walk testing; 6MWT-1 = first 6-min walk testing; 6MWT-2 = second 6-min walk testing; 6MWT-3 = single-bout 6-min walk testing; SpO2 = pulse oximetric saturation; TLC = total lung capacity; O2 = oxygen uptake; O2max = maximal oxygen uptake; Wmax = maximal power

Received for publication May 21, 2002. Accepted for publication September 5, 2002.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 References
 

  1. Préfaut, CH, Varray, A, Vallet, G (1995) Pathophysiological basis of exercise training in patients with chronic obstructive lung disease. Eur Respir Rev 5,27-32
  2. Dillard, TA, Piantadosi, S, Rajogopal, KR Determinants of maximum exercise capacity in patients with chronic airflow obstruction. Chest 1989;96,267-271[Abstract/Free Full Text]
  3. Killian, KJ, Leblanc, P, Martin, DH, et al Exercise capacity and ventilatory, circulatory and symptom limitation in patients with chronic airflow limitation. Am Rev Respir Dis 1992;146,935-940[ISI][Medline]
  4. Maltais, F, Simard, A, Simard, C, et al Oxidative capacity of the skeletal muscle and lactic acid kinetics during exercise in normal subjects and in patients with COPD. Am J Respir Crit Care Med 1996;153,288-293[Abstract]
  5. Maltais, F, Jobin, J, Sullivan, MJ, et al Metabolic and hemodynamic responses of lower limb during exercise in patients with COPD. J Appl Physiol 1998;84,1573-1580[Abstract/Free Full Text]
  6. Lacasse, Y, Wong, E, Guyatt, GH, et al Meta-analysis of respiratory rehabilitation in chronic obstructive pulmonary disease. Lancet 1996;348,1115-1119[CrossRef][ISI][Medline]
  7. Varray, A, Préfaut, C Exercise training in patients with respiratory disease: procedures and results. Eur Respir Rev 1995;5,51-58
  8. Cockcroft, A, Beaumont, A, Adams, L, et al Arterial oxygen desaturation during treadmill and bicycle exercise in patients with chronic obstructive airways disease. Clin Sci (Lond) 1985;68,327-332[Medline]
  9. Palange, P, Forte, S, Onorati, P, et al Ventilatory and metabolic adaptations to walking and cycling in patients with COPD. J Appl Physiol 2000;88,1715-1720[Abstract/Free Full Text]
  10. Guyatt, GH, Sullivan, MJ, Thompson, PJ, et al The six-minute walk test: a new measure of exercise capacity in patients with chronic heart failure. Can Med Assoc J 1985;132,919-923[Abstract]
  11. Redelmeier, D, Bayoumi, A, Goldstein, R, et al Interpreting small differences in functional status: the six-minute walk test in chronic lung disease patients. Am J Respir Crit Care Med 1997;155,1278-1282[Abstract]
  12. Pauwels, RA, Buist, AS, Calverley, PM, et al Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001;163,1256-1276[Free Full Text]
  13. Wasserman, K, Hansen, J, Sue, D, et al Principles of exercise testing and interpretation. 1986 Lea and Febiger. Philadelphia, PA:
  14. Préfaut, C, Durand, F, Mucci, P, et al Exercise-induced arterial hypoxemia in athletes: a review. Sports Med 2000;30,47-61[CrossRef][ISI][Medline]
  15. Covey, MK, Larson, JL, Alex, CG, et al Test-retest reliability of symptom-limited cycle ergometer tests in patients with chronic obstructive pulmonary disease. Nurs Res 1999;48,9-19[CrossRef][ISI][Medline]
  16. Marin, J, Carrizo, S, Gascon, M, et al Inspiratory capacity, dynamic hyperinflation, breathlessness, and exercise performance during the 6-minute-walk test in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001;163,1395-1399[Abstract/Free Full Text]
  17. Mak, VH, Bugler, JR, Roberts, CM, et al Effect of arterial oxygen desaturation on six minute walk distance, perceived effort, and perceived breathlessness in patients with airflow limitation. Thorax 1993;48,33-38[Abstract]
  18. Troosters, T, Gosselink, R, Decramer, M Six minute walking distance in healthy elderly subjects. Eur Respir J 1999;14,270-274[Abstract]
  19. Jones, NL Clinical exercise testing. 1988 WB Saunders. Philadelphia, PA:
  20. Baarends, EM, Schols, AM, Mostert, R, et al Analysis of the metabolic and ventilatory response to self-paced 12-minute treadmill walking in patients with severe chronic obstructive pulmonary disease. J Cardiopulm Rehabil 1998;18,23-31[CrossRef][Medline]
  21. Galy, O, Hue, O, Le Gallais, D, et al Is exercise-induced desaturation activity-dependent? Plügers Arch 2001;442,R93
  22. Celli, BR, Rasullo, J, Make, BJ Dyssynchronous breathing during arm but not leg exercise in patients with chronic airflow obstruction. N Engl J Med 1986;314,1485-1490[Abstract]
  23. Delgado, HR, Brown, SR, Skatrud, JB, et al Chest wall and abdominal motion during exercise in patients with chronic obstructive pulmonary disease. Am Rev Respir Dis 1982;126,200-205[Medline]
  24. Mathur, RS, Revill, SM, Vara, DD, et al Comparison of peak oxygen consumption during cycle and treadmill exercise in severe chronic obstructive pulmonary disease. Thorax 1995;50,829-833[Abstract]



This article has been cited by other articles:


Home page
 ChestHome page
D. D. Marciniuk, S. J. Butcher, J. K. Reid, G. F. MacDonald, N. D. Eves, R. Clemens, and R. L. Jones
The Effects of Helium-Hyperoxia on 6-min Walking Distance in COPD: A Randomized, Controlled Trial
Chest, June 1, 2007; 131(6): 1659 - 1665.
[Abstract] [Full Text] [PDF]

Home page
 Eur Respir JHome page
G. Deboeck, G. Niset, J-L. Vachiery, J-J. Moraine, and R. Naeije
Physiological response to the six-minute walk test in pulmonary arterial hypertension
Eur. Respir. J., October 1, 2005; 26(4): 667 - 672.
[Abstract] [Full Text] [PDF]

Home page
 Proc Am Thorac SocHome page
T. Higenbottam
Pulmonary Hypertension and Chronic Obstructive Pulmonary Disease: A Case for Treatment
Proceedings of the ATS, April 1, 2005; 2(1): 12 - 19.
[Abstract] [Full Text] [PDF]

Home page
 ChestHome page
J. E. Johnson
Which Exercise Test Should Be Used for Patients With Symptomatic COPD?
Chest, September 1, 2004; 126(3): 668 - 670.
[Full Text] [PDF]

Home page
 ChestHome page
S. E. Turner, P. R. Eastwood, N. M. Cecins, D. R. Hillman, and S. C. Jenkins
Physiologic Responses to Incremental and Self-Paced Exercise in COPD: A Comparison of Three Tests
Chest, September 1, 2004; 126(3): 766 - 773.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
V. N. Lama, K. R. Flaherty, G. B. Toews, T. V. Colby, W. D. Travis, Q. Long, S. Murray, E. A. Kazerooni, B. H. Gross, J. P. Lynch III, et al.
Prognostic Value of Desaturation during a 6-Minute Walk Test in Idiopathic Interstitial Pneumonia
Am. J. Respir. Crit. Care Med., November 1, 2003; 168(9): 1084 - 1090.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via ISI Web of Science (20)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Poulain, M.
Right arrow Articles by Préfaut, C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Poulain, M.
Right arrow Articles by Préfaut, C.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS