6 – Minute walk test in patients 6 – Minute walk test in patients with COPD: clinical applications with COPD: clinical applications

in pulmonary rehabilitation in pulmonary rehabilitation

Vasanthi .JVasanthi .J

Author : Sue C.JenkinsAuthor : Sue C.Jenkins

Physiotherapy Physiotherapy

Volume 93Volume 93

2007, 175 – 182 2007, 175 – 182

Introduction Introduction

COPD is the leading cause of morbidity COPD is the leading cause of morbidity and mortality worldwide.and mortality worldwide.

Develop progressive disability and Develop progressive disability and impairment in quality of life.impairment in quality of life.

The prevalence of COPD is increased in The prevalence of COPD is increased in many parts of world as the result of ageing many parts of world as the result of ageing and increase in cigarette smoking.and increase in cigarette smoking.

Assessment of functional exercise Assessment of functional exercise capacity in pulmonary rehabilitationcapacity in pulmonary rehabilitation

Pulmonary rehabilitation is strongly endorsed as Pulmonary rehabilitation is strongly endorsed as an evidence based intervention for the an evidence based intervention for the management of patients with COPD.management of patients with COPD.

In clinical practice 6-minute walk test and In clinical practice 6-minute walk test and incremental shuttle walking test are commonly incremental shuttle walking test are commonly used to assess.used to assess.

Both tests have validity, reliability after one Both tests have validity, reliability after one familiarization test, capacity to detect changes familiarization test, capacity to detect changes following Pulmonary rehabilitation.following Pulmonary rehabilitation.

Compared with other lab based tests Compared with other lab based tests these have increased availability, low cost, these have increased availability, low cost, and because ground- based walking is and because ground- based walking is more representative of ADL. more representative of ADL.

Is the 6 MWD a valid measure ?Is the 6 MWD a valid measure ?

Demonstrated by moderate to good Demonstrated by moderate to good relationship between 6 MWD and VOrelationship between 6 MWD and VO2peak2peak

Examination of relationship between Examination of relationship between 6MWW ( product of Body weight and 6MWW ( product of Body weight and 6MWD) and VO6MWD) and VO2peak2peak reveals a stronger reveals a stronger

relationship than 6MWD because 6MWW relationship than 6MWD because 6MWW represents work done.represents work done.

Does 6MWD provide information Does 6MWD provide information about physical activity during daily about physical activity during daily

life?life?Dyspnoea during ADL in COPD patients due to Dyspnoea during ADL in COPD patients due to inactivity and associated problems of inactivity and associated problems of deconditioning and muscle weakness.deconditioning and muscle weakness.

Compared to healthy controls COPD patients Compared to healthy controls COPD patients spent less time standing and walking during spent less time standing and walking during ADL.ADL.

In one study (Pitta et al ) concluded that a In one study (Pitta et al ) concluded that a reduced 6MWD (<400m)is the best marker of reduced 6MWD (<400m)is the best marker of inactivity during daily life in patients with COPD.inactivity during daily life in patients with COPD.

Is 6MWD associated with survival?Is 6MWD associated with survival?

Stronger predictor of survival than FEVStronger predictor of survival than FEV11..

Because 6MWD is influenced by skeletal Because 6MWD is influenced by skeletal muscle dysfunction as well as pulmonary muscle dysfunction as well as pulmonary impairment and so reflects both the impairment and so reflects both the primary pulmonary and secondary primary pulmonary and secondary systemic manifestations of COPD.systemic manifestations of COPD.

selection of patients for lung selection of patients for lung volume reduction surgery or volume reduction surgery or

transplantationtransplantationIn patients undergoing LVRS reported that In patients undergoing LVRS reported that a 6MWD < 200m was associated with high a 6MWD < 200m was associated with high level of mortality 6 months post op.level of mortality 6 months post op.6MWT was a useful tool in the 6MWT was a useful tool in the assessment of when to list patients for assessment of when to list patients for lung transplantation and that a 6MWD of lung transplantation and that a 6MWD of <400m appeared to be a reasonable <400m appeared to be a reasonable marker corresponding to when a patient marker corresponding to when a patient should be listed.should be listed.

Is a reliable measure?Is a reliable measure?

Requires a strict standardization protocol.Requires a strict standardization protocol.

Factors that affect areFactors that affect are

- track length - track length

- course layout- course layout

-instructions-instructions

- encouragement- encouragement

- no of tests- no of tests

Familiarization test is needed for new.Familiarization test is needed for new.

Dypnoea is main limiting factor so repeat Dypnoea is main limiting factor so repeat the test after 20 – 30 min rest period by the test after 20 – 30 min rest period by which time the patient will recover.which time the patient will recover.

Familiarization test always ?Familiarization test always ?

No need in co morbid limiting statusNo need in co morbid limiting status- Musculoskeletal or claudication pain- Musculoskeletal or claudication pain- Cardiac disease – 85% of age - Cardiac disease – 85% of age

predicted Max HRpredicted Max HR- Profound oxygen desaturation - Profound oxygen desaturation

(SpO(SpO22 < 80 %).< 80 %).

When 6MWT is repeated at long – term When 6MWT is repeated at long – term follow up Familiarization test may be follow up Familiarization test may be neededneeded

Standardized protocol Standardized protocol

ATS guidelines:ATS guidelines:-safer, easier, better tolerated-safer, easier, better tolerated-better reflects ADL-better reflects ADL- do not walk along with patient- do not walk along with patient-pulse oxymetry is optional-pulse oxymetry is optional-do not use treadmill-do not use treadmill-do not use circular track-do not use circular track- count the laps with lap counter- count the laps with lap counter- Familiarization test is not needed for most - Familiarization test is not needed for most clinical settings. clinical settings.

Australian physio association & Australian physio association & aust lung foundationaust lung foundation

Perform in two occasion Perform in two occasion

Best result recordedBest result recorded

At least 30 min rest in betweenAt least 30 min rest in between

Walking track must be same for all testsWalking track must be same for all tests

Comfortable ambient temp and humidity Comfortable ambient temp and humidity should be maintained for all testsshould be maintained for all tests

Before test:Before test:- medical H/o,precautions, CI- medical H/o,precautions, CI- comfortable dress, footwear- comfortable dress, footwear- aviod eating before 2 hrs- aviod eating before 2 hrs- inhaled BD- inhaled BD- rest for 15 min before test- rest for 15 min before test

-record – BP,HR,SaO-record – BP,HR,SaO22, Dyspnoea , Dyspnoea scorescore

At the end:At the end:

- put a marker on the distance walked- put a marker on the distance walked

- seat the pt- seat the pt

- record – BP,HR,SaO- record – BP,HR,SaO22, Dyspnoea , Dyspnoea

scorescore

If patient stops during:If patient stops during:- allow to sit- allow to sit

- measure HR,SaO- measure HR,SaO22

- ask reason why stopped- ask reason why stopped

- record the time stopped- record the time stopped- tell that begin as soon as you feel - tell that begin as soon as you feel

betterbetter-monitor untoward symptom-monitor untoward symptom

Stop the test:Stop the test:

- chest pain - chest pain

- mantal confusion- mantal confusion

- light headedness- light headedness

-intolerable dyspnoea-intolerable dyspnoea

- leg cramp- leg cramp

-SaO-SaO2 2 <85% <85%

Normal 6MWDNormal 6MWD

Age , height, weight, gender are significant Age , height, weight, gender are significant contributorscontributors

Can predict by equation Can predict by equation

6 MWD 6 MWD pred pred = 218 + (5.14 * Ht cm – 5.32 = 218 + (5.14 * Ht cm – 5.32

* age ) – 1.80 * wt kg + 51.31 * gender.* age ) – 1.80 * wt kg + 51.31 * gender.

Male = 1Male = 1

Female = 0Female = 0

Different for geographical regions so Different for geographical regions so calculate own range.calculate own range.

Minimum clinically important Minimum clinically important difference (MCID)difference (MCID)

54 m54 m

What percentage achieve MCID?What percentage achieve MCID?

If standard protocol followed 1/3 can If standard protocol followed 1/3 can reach 54 mreach 54 m

Walking prescription Walking prescription

Prescribing ex on the base of 6MWD for Prescribing ex on the base of 6MWD for walking lapswalking laps

80% ( 6MWD 80% ( 6MWD ÷6 ) ×prescribed duration÷6 ) ×prescribed duration

6MWD 6MWD ÷6 = distance in 1 min÷6 = distance in 1 min

For distance in 30 min = 1 min distance ×30For distance in 30 min = 1 min distance ×30

For distance in 20 min = 1 min distance ×20For distance in 20 min = 1 min distance ×20

For distance in 10 min = 1 min distance ×10For distance in 10 min = 1 min distance ×10

Rollator Rollator

COPD pt less dyspnic in rollatorCOPD pt less dyspnic in rollator

6MWD can be used to quantify the 6MWD can be used to quantify the benefits of rollator and identify which benefits of rollator and identify which patient benefit from.patient benefit from.

To detect ex induced hypoxemiaTo detect ex induced hypoxemia

Desaturation common in 6MWD Desaturation common in 6MWD

Because of varying body position and un Because of varying body position and un supported arm while walking.supported arm while walking.

Marked desaturation during 6MWT is an Marked desaturation during 6MWT is an indication to prescribe an intermittent indication to prescribe an intermittent walking training protocol and identifies the walking training protocol and identifies the requirement of more frequent saturation requirement of more frequent saturation monitoring during ex.monitoring during ex.

Is useful in acute exacerbation of Is useful in acute exacerbation of COPD?COPD?

A low 6MWD < 367m associated with A low 6MWD < 367m associated with readmission readmission

Helps to quantify the impact of acute Helps to quantify the impact of acute exacerbation on a patient’s functional ex exacerbation on a patient’s functional ex capacity.capacity.

Has been used as a outcome measure of Has been used as a outcome measure of pul rehab following acute exacerbation .pul rehab following acute exacerbation .

Conclusion Conclusion

This review highlighted the clinical This review highlighted the clinical applications of 6MWD in patients with applications of 6MWD in patients with COPD undergoing pul rehab.COPD undergoing pul rehab.

Future research – further refine the Future research – further refine the applications, new applications in COPD.applications, new applications in COPD.