Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic

Rhona Sinclair; V. Goodridge; Alan Batterham; Gerard Danjoux

Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic

Rhona Sinclair, V. Goodridge, Alan Batterham, Gerard Danjoux

Research output: Contribution to conference › Paper › peer-review

Abstract

Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction
before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and
subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min
walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT.
Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET
was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was
derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the
furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE),
providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable
CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances
walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass
correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake
a definitive concurrent validity study.

Original language	English
Publication status	Published - 2009
Event	2008 Meeting of the Anaesthetic Research Society, Royal College of Anaesthetists - London, United Kingdom Duration: 20 Nov 2008 → 21 Nov 2008

Conference

Conference	2008 Meeting of the Anaesthetic Research Society, Royal College of Anaesthetists
Country/Territory	United Kingdom
City	London
Period	20/11/08 → 21/11/08

Bibliographical note

Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.

Cite this

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title = "Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic",

abstract = "Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.",

author = "Rhona Sinclair and V. Goodridge and Alan Batterham and Gerard Danjoux",

note = "Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.; 2008 Meeting of the Anaesthetic Research Society, Royal College of Anaesthetists ; Conference date: 20-11-2008 Through 21-11-2008",

year = "2009",

language = "English",

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Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic. / Sinclair, Rhona; Goodridge, V.; Batterham, Alan et al.
2009. Paper presented at 2008 Meeting of the Anaesthetic Research Society, Royal College of Anaesthetists, London, United Kingdom.

Research output: Contribution to conference › Paper › peer-review

TY - CONF

T1 - Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic

AU - Sinclair, Rhona

AU - Goodridge, V.

AU - Batterham, Alan

AU - Danjoux, Gerard

N1 - Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.

PY - 2009

Y1 - 2009

N2 - Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.

AB - Functional assessment of exercise capacity is now widely recognized as a major determinant of preoperative risk prediction before major surgery. Two different techniques are principally used in the UK: cardiopulmonary exercise testing (CPET) and subjective patient-reported assessment of metabolic equivalents (METs). The identification of anaerobic threshold (AT), from CPET, presently represents the UK gold standard; however, reported METs form a cornerstone of the American Heart Association preoperative guidelines. Unpublished data from our institution have demonstrated a poor correlation between patient-reported METs and oxygen consumption (VO2) at AT (r¼0.31). The sensitivity and predictive value of METs to identify objective, CPET-derived exercise capacity was also low (sensitivity 24%). With this in mind, our group felt that where CPET is unavailable, a more robust test of exercise capacity is required to accurately assess the operative risk. We propose that the 6 min walk test (6MWT) may fulfil this requirement. The aim of this study was to examine the validity of the 6MWT against a criterion measure derived from CPET: AT. Fifteen participants, undergoing major non-cardiac surgery, were recruited from our preoperative assessment clinics. CPET was conducted according to our standardized ramped protocol with participants exercising until they attained their AT. AT was derived from the data recorded using the V-slope method. After a short rest period, participants completed two separate 6MWT; the furthest distance walked was recorded. Statistical analysis used an ordinary least-squares linear regression method to derive the validity coefficient (r) and the standard error of the estimate (SEE), providing the typical prediction error associated with the prediction of AT from the results of a 6MWT in an individual patient. All participants completed three tests. Mean age was 69.5 (SD 7.0) yr (12 males and three females). Data from 13 participants were suitable for statistical analysis (two exclusions: one unreadable CPET and one invalid 6MWT from knee injury). The group achieved a mean AT of 10.1 (SD 3.5) ml O2 kg21 min21 and a mean 6MWT distance of 548.1 (SD 74.1) m. The distances walked during two 6MWT demonstrated a mean improvement of 19 m; the 6MWT was a highly reliable test, with an intraclass correlation (3.1) of 0.94. We found a validity coefficient of r¼0.76, with a standard error of prediction of AT from distance walked during 6MWT of +2.4 ml O2 kg21 min21. The 6MWT demonstrates a strong correlation with AT in this pilot study, with good repeatability between tests. It may provide a robust, cheap, accurate alternative for measuring exercise capacity where CPET is unavailable. On the basis of this encouraging exploratory phase correlation, we now plan to undertake a definitive concurrent validity study.

UR - http://bja.oxfordjournals.org/content/vol102/issue4/index.dtl#IN_THIS_ISSUE

M3 - Paper

T2 - 2008 Meeting of the Anaesthetic Research Society, Royal College of Anaesthetists

Y2 - 20 November 2008 through 21 November 2008

ER -

Validity of the 6 min walk test as a surrogate for the anaerobic threshold in the preoperative assessment clinic

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