Introduction COPD is the leading cause of morbidity and mortality worldwide. Develop progressive disability and impairment in quality of life. The prevalence of COPD is increased in many parts of world as the result of ageing and increase in cigarette smoking.
Assessment of functional exercise capacity in pulmonary rehabilitation Pulmonary rehabilitation is strongly endorsed as an evidence based intervention for the management of patients with COPD. In clinical practice 6-minute walk test and incremental shuttle walking test are commonly used to assess. Both tests have validity, reliability after one familiarization test, capacity to detect changes following Pulmonary rehabilitation.
Compared with other lab based tests these have increased availability, low cost, and because ground- based walking is more representative of ADL.
Is the 6 MWD a valid measure ? Demonstrated by moderate to good relationship between 6 MWD and VO 2peak Examination of relationship between 6MWW ( product of Body weight and 6MWD) and VO 2peak reveals a stronger relationship than 6MWD because 6MWW represents work done.
Does 6MWD provide information about physical activity during daily life? Dyspnoea during ADL in COPD patients due to inactivity and associated problems of deconditioning and muscle weakness. Compared to healthy controls COPD patients spent less time standing and walking during ADL. In one study (Pitta et al ) concluded that a reduced 6MWD (<400m)is the best marker of inactivity during daily life in patients with COPD.
Is 6MWD associated with survival? Stronger predictor of survival than FEV 1. Because 6MWD is influenced by skeletal muscle dysfunction as well as pulmonary impairment and so reflects both the primary pulmonary and secondary systemic manifestations of COPD.
selection of patients for lung volume reduction surgery or transplantation selection of patients for lung volume reduction surgery or transplantation In patients undergoing LVRS reported that a 6MWD < 200m was associated with high level of mortality 6 months post op. 6MWT was a useful tool in the assessment of when to list patients for lung transplantation and that a 6MWD of <400m appeared to be a reasonable marker corresponding to when a patient should be listed.
Is a reliable measure? Requires a strict standardization protocol. Factors that affect are - track length - course layout -instructions - encouragement - no of tests
Familiarization test is needed for new. Dypnoea is main limiting factor so repeat the test after 20 – 30 min rest period by which time the patient will recover.
Familiarization test always ? No need in co morbid limiting status - Musculoskeletal or claudication pain - Cardiac disease – 85% of age predicted Max HR - Profound oxygen desaturation (SpO 2 < 80 %). When 6MWT is repeated at long – term follow up Familiarization test may be needed
Standardized protocol ATS guidelines: -safer, easier, better tolerated -better reflects ADL - do not walk along with patient -pulse oxymetry is optional -do not use treadmill -do not use circular track - count the laps with lap counter - Familiarization test is not needed for most clinical settings.
Australian physio association & aust lung foundation Perform in two occasion Best result recorded At least 30 min rest in between Walking track must be same for all tests Comfortable ambient temp and humidity should be maintained for all tests
Before test: - medical H/o,precautions, CI - comfortable dress, footwear - aviod eating before 2 hrs - inhaled BD - rest for 15 min before test -record – BP,HR,SaO 2, Dyspnoea score
At the end: - put a marker on the distance walked - seat the pt - record – BP,HR,SaO 2, Dyspnoea score
If patient stops during: - allow to sit - measure HR,SaO 2 - ask reason why stopped - record the time stopped - tell that begin as soon as you feel better -monitor untoward symptom
Normal 6MWD Age, height, weight, gender are significant contributors Can predict by equation 6 MWD pred = (5.14 * Ht cm – 5.32 * age ) – 1.80 * wt kg * gender. 6 MWD pred = (5.14 * Ht cm – 5.32 * age ) – 1.80 * wt kg * gender. Male = 1 Female = 0
Different for geographical regions so calculate own range.
Minimum clinically important difference (MCID) 54 m
What percentage achieve MCID? If standard protocol followed 1/3 can reach 54 m
Walking prescription Prescribing ex on the base of 6MWD for walking laps 80% ( 6MWD ÷6 ) ×prescribed duration 6MWD ÷6 = distance in 1 min For distance in 30 min = 1 min distance ×30 For distance in 20 min = 1 min distance ×20 For distance in 10 min = 1 min distance ×10
Rollator COPD pt less dyspnic in rollator 6MWD can be used to quantify the benefits of rollator and identify which patient benefit from.
To detect ex induced hypoxemia Desaturation common in 6MWD Because of varying body position and un supported arm while walking. Marked desaturation during 6MWT is an indication to prescribe an intermittent walking training protocol and identifies the requirement of more frequent saturation monitoring during ex.
Is useful in acute exacerbation of COPD? A low 6MWD < 367m associated with readmission Helps to quantify the impact of acute exacerbation on a patient’s functional ex capacity. Has been used as a outcome measure of pul rehab following acute exacerbation.
Conclusion This review highlighted the clinical applications of 6MWD in patients with COPD undergoing pul rehab. Future research – further refine the applications, new applications in COPD.