**3.3 Discussion**

The literature on the 6MWT does not provide any comparative material for our results obtained during a walk along a hallway 22 m in length performed by healthy individuals, 28 years of age on average. The mean distance covered by our volunteers amounting to 625**.**9 m may only be compared with the distance obtained by other researchers, walked by healthy subjects over 40 years of age. In the work by Enright et al. [11], the distance was equal to an average of 535 m, while in the work by Troosters (Troosters et al., 1999) – to 631 m. In comparison with the distance covered by the subjects in the study by Enright & Sherill (Enright & Sherill, 1998), our volunteers covered almost 100 m more. The recorded difference is very likely to be related to our volunteers' young age (29 on average). In the study by Troosters et al., the average distance in a 50-metre-long hallway was a few meters longer than that covered by our healthy volunteers who were two decades younger. Almost identical distances in completely different age groups may only be explained by the fact that older patients had to do two times fewer turnarounds in a 50-metre-long hallway.

Hallway 625**.**9 94**.**6 57**.**1 < 0**.**009

Table 1. The distance covered during the six-minute walk test on the treadmill and in the

Difference between the means

value SD Mean

Table 2. The heart rate and blood pressure before and after the test performed on the

The Hotteling T2 test was used to assess the equality of vectors of the expected values for

The obtained result: T2=11**.**7 and F=7**.**3<<53 (where 53 stands for the threshold of the hypothesis at significance level <0**.**05) gives a clear evidence about the identical

The literature on the 6MWT does not provide any comparative material for our results obtained during a walk along a hallway 22 m in length performed by healthy individuals, 28 years of age on average. The mean distance covered by our volunteers amounting to 625**.**9 m may only be compared with the distance obtained by other researchers, walked by healthy subjects over 40 years of age. In the work by Enright et al. [11], the distance was equal to an average of 535 m, while in the work by Troosters (Troosters et al., 1999) – to 631 m. In comparison with the distance covered by the subjects in the study by Enright & Sherill (Enright & Sherill, 1998), our volunteers covered almost 100 m more. The recorded difference is very likely to be related to our volunteers' young age (29 on average). In the study by Troosters et al., the average distance in a 50-metre-long hallway was a few meters longer than that covered by our healthy volunteers who were two decades younger. Almost identical distances in completely different age groups may only be explained by the fact that

older patients had to do two times fewer turnarounds in a 50-metre-long hallway.

Before the test After the test

125.9 13**.**4 123**.**0 12**.**5 -2**.**9 <0**.**4 134**.**2 16**.**2 135**.**8 18**.**5 1**.**6 <0**.**73

SD Difference between the

P Hallway Treadmill

value SD Mean

means [m]

P

Difference between the means

value SD

<sup>9</sup>96**.**8 19**.**5 103**.**2 22**.**5 6**.**4 <0**.**<sup>25</sup>

<sup>7</sup>83**.**7 11**.**8 82**.**6 9**.**6 -0**.**9 <0**.**<sup>71</sup>

P

Mean distance [m]

Treadmill 683**.**0 65**.**2

Hallway Treadmill

[bpm] 76**.**9 12**.**9 81**.**4 13**.**3 4**.**5 <0**.**<sup>1</sup>

<sup>81</sup>**.**4 7**.**8 80**.**2 8**.**0 -1**.**2 <0**.**<sup>5</sup>

value SD Mean

Mean

treadmill and in the hallway

seven analyzed parameters of the 6MWT.

hemodynamic effects of both testing methods.

Way of performing

the 6MWT

hallway

Way of performing the 6MWT

Heart rate

Systolic pressure [mm Hg]

Diastolic pressure [mm Hg]

**3.3 Discussion** 

ATS guidelines approved in 2002, which specify the length and width of the hallway, will certainly make it possible to compare the 6MWT results obtained in various centres. Another way of comparing the results obtained in various places is the proposed return to the idea of using the treadmill.

In our study most, i.e. 86% of the healthy volunteers who had participated in the test, evaluated the comfort of a treadmill test as better than or the same as the hallway test. Hence, the applied design solutions and algorithm may be regarded as appropriate and flexible in terms of adjusting the speed of the treadmill belt to the walking speed of a healthy individual.

In the paper by Stevens et al., the participants could put in motion, speed up and slow down the treadmill by means of a special switch (Stevens et al., 1999). Although Stevens et al. enabled the participants to adjust the treadmill to their walking speed "by hand", the distance covered on the treadmill turned out to be shorter indeed than the distance walked in the hallway because the participant could hardly adjust to the speed of the treadmill belt.

We applied a treadmill which adjusts its speed to the walking capacity of the individual. As a result, the persons taking part in the test covered a distance 57**.**1 meters longer on average than in the hallway. The distance covered on the treadmill is longer than that walked in the hallway both due to flexible adjustment of the treadmill belt to the walking speed and due to avoiding multiple turnarounds and hence the need to speed up and slow down in the hallway test.

The multi-aspect analysis of the results including the distance covered, blood pressure and pulse measured before and after the 6MWT, shows similar hemodynamic consequences for both methods. Thus, it can be inferred that in the future it will be possible to determine the conversion rate, at least for healthy subjects, facilitating the comparison of the results obtained during a test in a 30-m hallway with the results on an adjustable treadmill.

As opposed to conditions in the hallway, the 6MWT on a moving treadmill creates possibilities of easy monitoring of heart rate and arterial blood pressure. This enables the hemodynamic surveillance that is necessary for the safe test performance in patients with cardiac insufficiency.

The attempt by Stevens at al. to use the treadmill for a 6MWT in patients with respiratory failure did not meet the expectations as it shortened the distance in comparison with a hallway test. Our results show the expected elongation of the distance compared with the hallway test, although they cannot be currently referred to patients with intermittent dysbasia, heart failure or severe lung disease. Patients suffering from such diseases are less fit, which may affect their ability to perform the 6MWT on a modified adjustable treadmill. We are aware of the fact that the decision whether our modified treadmill meets the expectations of physicians who use the 6MWT in their medical practice and research can only be made after performing the tests in these groups of patients. In finished, but yet not published trial we assumed that the quality of the algorithm version adjusting the speed of the treadmill belt to the pace of the patient's walk during the six-minute walk test (6MWT) on a moving treadmill, checked for healthy volunteers, makes it possible to perform the test safely in patients with heart failure (Szczurek et al., 2006; Prochaczek et al., 2007).

The work was intended to compare the distance covered, the level of exertion and hemodynamic effects in a hallway test and in a test on a modified treadmill for patients with

The Six-Minute Walk Test on the Treadmill 229

did not interfere with the measurements. As a result, we have developed an algorithm that makes the 6-minute walk test on the treadmill much safer than at the beginning and very similar to a classic hallway test. It has allowed us to prepare a commercial version of the ERT-100 treadmill equipped with a transmitter and receiver. The treadmill has passed the

The second part of the chapter contains the evaluation of adjustment of the new treadmill to the walking pace of healthy volunteers, as well as a comparison of the distance covered during the 6-minute walk on the treadmill and in the hallway. A better comfort of the 6MWT and a longer distance covered on the treadmill compared with the distance covered in the hallway may indicate that the algorithm of adjusting the speed of the treadmill to the

The obtained results demonstrating the advantages of the treadmill in healthy volunteers have encouraged us to perform a 6MWT for patients with heart failure in the II-III NYHA classes. In yet not published material it has been shown that the treadmill test was tolerated equally well by the patients as the hallway test. The fact that a similar distance was covered in both tests demonstrates that the technological barrier preventing us from obtaining

The availability of a treadmill adapting its pace to the patient's capacity, makes it possible to start treatment assessment or rehabilitation in patients with HF or COPD both inside and

The authors would like to thanks all the volunteers from the Academy of Physical Education

American Thoracic Association [ATS] statements (2002). Guidelines for the six-minute walk test. *Am. J Respir Crit Care Med,* Vol. 166, No 1, pp. 111-117, ISSN 1535-4970 Bittner, V., Weiner, D.H., Yusuf, S., Rogers, W.J., McIntyre, K.M., Bangdiwala, S.I.,

Costanzo, M.R., Augustine, S., Bourge, R., et al. (1995). Selection et treatment of candidates

Enright, P.L. & Sherill, D.D. (1998). Reference equations for the six-minute walk in healthy adults. *Am J Respir Crit Care Med,* Vol. 158, No 5, pp. 1384-1387, ISSN 1535-4970. Guyatt, G.H., Sullivan, M.J., Thompson, P.J., Fallen, E.L., Pugsley, S.O., Taylor, D.W. &

Kronenberg, M.W., Kostis, J.B., et al. - the SOLVD Investigators. (1993). Prediction of mortality and morbidity with the 6 minute walk test in patients with left ventricular dusfunction. *JAMA, Vol.* 270, No 14, pp. 1702-1707, ISSN 1538-3598. Bittner, V. (2003). Exercise testing in heart failure: Maximal, submaximal, or both? *J Am Coll* 

for heart transplantation. A statement for health professionals from the Committee on Heart Failure and Cardiac Transplantation of the Council on Clinical Cardiology, American, Heart Association. *Circulation,* Vol. 92, No 12, pp. 3593–

Berman LB. (1985). The 6-minute walk: a new measure of exercise capacity in

credible results of the six-minute walk test on the treadmill, has been overcome.

walking capacity of the tested individual has been properly selected.

*Cardiol,* Vol. 42, No 1, pp. 123-125, ISSN 0735-1097.

CE certification procedure.

outside the hospital.

**6. References** 

**5. Acknowledgements** 

in Katowice for their participation in the tests.

3612, ISSN 1524-4539.

heart failure in NYHA functional class II-III. Twenty people with diagnosed heart failure and tolerance of physical exercise in NYHA functional class II-III took part in the tests.

The analysis of the performance and results of the test indicates that during the six-minute walk test on a modified treadmill, HF patients in NYHA class II-III may slow the treadmill down safely or stop, depending on their exertion level. Our research has demonstrated that a walk test performed on a treadmill, controlled by means of the pace of the patient's walk, is equally well tolerated and generates exertion (Borg Scale 11,87 ± 2,90) that is similar as in case of the classic hallway test (Borg Scale 11,87 ± 2,90).

The fact that we have proved that there are no statistical differences in the distance covered (treadmill 317,36 ± 133,92, hallway 312,43 ± 117,76) and in the hemodynamic effects of the test performed on a treadmill compared to a hallway test, enables us to use a modified treadmill to replace the hallway test and vice versa, in order to evaluate patients with HF or chronic obstructive pulmonary disease. The fact that a similar distance was covered in both tests demonstrates that the technological barrier preventing us from obtaining credible results of the six-minute walk test on the treadmill, has been overcome. The availability of a treadmill adapting its pace to the patient's capacity, makes it possible to start treatment assessment or rehabilitation in patients with HF or COPD both inside and outside the hospital. If the results of our work are confirmed by other authors, the centres specializing in exercise tests will certainly be able to perform six-minute walk tests, while the hallways in hospitals and medical centres will be used for internal circulation purposes, as designed.

The modified treadmill providing solutions that are not offered by any other companies, may be additionally recommended for fitness purposes because the person using the treadmill may avoid dyspnoea by adjusting his or her walking speed.
