Por América Torres
The 6-minute walk test (6MWT) is used to objectively assess the exercise capacity of patients with moderate to severe pulmonary diseases. Unlike pulmonary function tests, the 6MWT captures the often-coexisting extrapulmonary manifestations of chronic respiratory diseases, including cardiovascular diseases, frailty, sarcopenia, and cancer.
Unlike cardiopulmonary exercise testing, this test is low-complexity and safe. The patient is simply asked to walk as far as possible along a 30-meter corridor for a period of 6 minutes. The absolute distance in the 6MWT and changes in it are predictive of morbidity and mortality in patients with COPD, pulmonary arterial hypertension, pulmonary fibrosis, and other conditions. This underscores that the information obtained from this test is very useful in making management decisions for patients. In this blog, we discuss the fundamentals of the 6-minute walk test and its many clinical benefits.
How it is performed
How it is performed
As the name suggests, the goal of the 6-minute walk test is for patients to walk as far as possible for 6 minutes. The test should be conducted indoors, on a 30-meter long, flat, straight corridor with a firm, low-traffic surface. There should be a starting line marking the beginning and end of each 60-meter lap, the length of the corridor should be marked every 3 meters, and the turnaround points should be marked with a cone (such as an orange traffic cone). In general, the following aspects should be observed:
- Patients should wear comfortable clothing and appropriate walking shoes. Additionally, they should use their usual walking aids during the test (such as a cane or walker), if applicable. They should not have engaged in intense exercise in the 2 hours prior to the test. However, a light meal is acceptable before tests conducted early in the morning or early in the afternoon. They should continue with their usual medical regimen.
- Patients should use their prescribed oxygen therapy and manage their oxygen delivery device. If this is not possible, the assessor should walk slightly behind to avoid setting the pace.
- It is important to record how patients were assisted with oxygen, as subsequent tests should be performed in the same manner.
- Oxygen should not be adjusted during the study, as supplemental oxygen and its portability affect exercise performance, and the distance walked.
- Patients should rest for at least 10 minutes before starting the test.
During this time, blood pressure, heart rate, SpO2, and baseline levels of dyspnea and fatigue should be documented.
Guidelines from the ATS for the 6-Minute Walk Test
Guidelines from the ATS for the 6-Minute Walk Test
In 2002, the American Thoracic Society published its Clinical Practice Guidelines for the 6-Minute Walk Test. This document details the factors influencing the results, provides a brief step-by-step protocol for performing the test, describes the safety measures to be observed, proper patient preparation and procedures, and offers guidelines for interpreting the results. Among the most notable information contained in this document, we can mention:
Indications for the Test. The strongest indication for the 6MWT is to measure the response to medical interventions in patients with moderate to severe cardiac or pulmonary diseases. However, it also serves as a predictor of morbidity and mortality in patients.
Contraindications: Absolute contraindications include unstable angina within the previous month and myocardial infarction within the previous month. Relative contraindications include a resting heart rate of more than 120, a systolic blood pressure of more than 180 mm Hg, and a diastolic blood pressure of more than 100 mm Hg.
Other ATS guidelines
- Repeated tests should be performed at approximately the same time of day to minimize intraday variability.
- A warm-up period before the test should not be performed.
- The patient should sit at rest in a chair, located near the starting point, for at least 10 minutes before the test begins.
Clinical uses of the 6-Minute Walk Test
Clinical uses of the 6-Minute Walk Test
Now that we have briefly discussed how to perform the test and the ATS guidelines to ensure patient safety during it, let’s move on to some of its most notable clinical advantages.
COPD. There is a strong correlation between the distance walked in the 6-minute walk test and clinical outcomes in patients with COPD. This is likely because the test captures both pulmonary and extrapulmonary manifestations of the disease. In fact, comorbidities are likely responsible for more than 50% of deaths in patients with COPD.
A study on longitudinal changes in the 6-minute walk distance in 198 patients with severe COPD over a 2-year period found increased survival with increments in 6MWD when divided into discrete 100-meter increments.
On the other hand, in a prospective observational study of 2,110 patients with clinically stable COPD in stages II to IV, according to the Global Initiative for Chronic Obstructive Lung Disease, where 6-minute walk tests (6MWT) were performed at baseline and annually, the 6MWD thresholds with the highest sensitivity and specificity for hospitalization or 3-year mortality were 357 and 334 meters, respectively.
Idiopathic Pulmonary Fibrosis. The 6-minute walk test has been a useful predictor of outcomes in numerous clinical settings for patients with idiopathic pulmonary fibrosis (IPF). In a prospective observational study of patients newly diagnosed with IPF, a 6MWD ≤ 72% of the predicted value was a significant independent predictor of mortality, with a hazard ratio of 3.27. When added to a composite physiological index (calculated based on the extent of disease on CT scan, diffusing capacity of the lung for carbon monoxide [DLCO], FVC, and FEV1) and the Medical Research Council dyspnea scale score, the test was able to predict 3-year mortality with 100% specificity.
Lung Transplant. Before 2005, lung allocation largely depended on the time a patient had been on the waiting list, regardless of disease severity. In 2005, a new allocation system was implemented to seek a more equitable distribution of organs. The lung allocation score is a 0 to 100 scale that uses predictive criteria for both waitlist mortality and post-transplant mortality. The 6-minute walk test (6MWT) has been incorporated into the scoring system as a dichotomous variable (above or below 150 feet [45.7 meters]). However, there is ongoing controversy regarding the appropriate threshold or whether it is preferable to use it as a continuous variable.
A great solution for a simple test
A great solution for a simple test
The 6-minute walk test has established itself as a reliable measure of functional capacity, which is also simple to perform and interpret. The distance walked in 6 minutes is considered a predictor of mortality across a wide range of chronic respiratory conditions.
SCHILLER offers an easy-to-use solution that further simplifies the execution of this test. The DS-20 diagnostic station is a device that combines the most requested functions into a single unit: vital signs and physical assessment tools such as NIBP, TEMP, SpO2, NIBP, and 3- and 12-lead ECGs. In addition to these features, it also includes the capability to perform the 6-minute walk test.
The DS-20 diagnostic station is very easy to use, allowing you to perform all tests quickly and streamline triage:
- Quickly assess the patient in a single area.
- View all information on the large touchscreen of the DS-20.
- Store studies on your PC via Wi-Fi, LAN, or Ethernet.
- Use the barcode reader to avoid data entry errors.
It only takes a few minutes to discover the practical advantages of the DS-20 diagnostic station. Experience them in a no-cost, no-obligation demonstration (either in-person or remote).
REFERENCES
[1] Priya Agarwala, Steve H. Salzman. Six-Minute Walk Test. Chest. 2020 Mar; 157(3): 603–611. Published online 2019 Nov 2. doi: 10.1016/j.chest.2019.10.014
[2] ATS Statement Guidelines for the Six-Minute Walk Test. https://www.atsjournals.org/doi/full/10.1164/ajrccm.166.1.at1102
