What are the parameters for interpreting a 6-Minute Walk Test (6MWT)?

From the Guidelines

The 6-minute walk test (6MWT) is interpreted based on the distance walked in 6 minutes, with a longer distance indicating better functional capacity, and should be performed in a 30-m long, flat, straight corridor with a hard surface, as described in the guidelines by the American Thoracic Society 1. The test evaluates the global and integrated responses of all systems involved during exercise, including the pulmonary and cardiovascular systems, systemic circulation, peripheral circulation, blood, neuromuscular units, and muscle metabolism. When evaluating results, it's essential to consider the following key parameters:

• The distance walked in 6 minutes (6MWD)
• Oxygen saturation, heart rate, and perceived dyspnea at the beginning and end of the test, as recommended by the European Respiratory Review 1
• The patient's ability to pace themselves and stop or rest if necessary The test should be performed indoors, along a long, flat, straight, enclosed corridor with a hard surface, and the length of the corridor should be marked every 3 m, with turnaround points marked with a cone. The use of a treadmill is not recommended, as patients are unable to pace themselves on a treadmill, and the results are not interchangeable with corridor tests, as noted in the American Journal of Respiratory and Critical Care Medicine 1. For accurate interpretation, the test should be performed after the patient has been instructed to walk as far as possible for 6 minutes, and the tester should only use standard phrases of encouragement every minute with an even tone of voice. The patient should remain supervised throughout the test to ensure safety and accurate symptom assessment. It is also important to note that the 6MWT is a practical and simple test that requires minimal equipment, but it does not provide specific information on the function of each of the different organs and systems involved in exercise, as discussed in the European Respiratory Review 1.

From the Research

Parameters for Interpreting an MWT

The parameters for interpreting a 6-minute walk test (6MWT) include:

• Distance walked in 6 minutes (6MWD) [ 2 ]
• Oxygen saturation (SaO2) [ 2 ]
• Pulse rate [ 2 ]
• Degree of dyspnea (Borg scale) [ 2 ]
• Minimal clinically important difference (MCID) for change in 6MWT distance [ 3 ]

Reference Equations

Reference equations for predicting 6MWD in healthy adults have been established [ 2 ]:

• For men: 6MWD = (7.57 x heightcm) - (5.02 x age) - (1.76 x weightkg) - 309 m
• For women: 6MWD = (2.11 x heightcm) - (2.29 x weightkg) - (5.78 x age) + 667 m

Clinical Role and Technique

The 6MWT is a low-complexity, safe test that captures extrapulmonary manifestations of chronic respiratory disease [ 4 ]

• The test requires a 30-m minimally trafficked corridor and measures the distance walked in 6 minutes
• Factors that can affect walk distance include track layout, track length, oxygen amount and portability, learning effect, and verbal encouragement [ 4 ]

Prognostic Value

The 6MWT has been shown to be predictive of morbidity and mortality in patients with certain chronic respiratory conditions [ 5, 4 ]

• The absolute 6MWD and change in 6MWD are predictive of outcomes in patients with COPD, pulmonary arterial hypertension, and idiopathic pulmonary fibrosis [ 4 ]