This guide guides the clinical application of six-minute walking test (6MWT). The indications and various factors affecting the results are summarized, the specific operation scheme and safety inspection method are given, the correct preparation procedure of patients is described, and the clinical interpretation of the inspection results is provided. These suggestions are not intended to restrict the use of other procedures in research work, nor to discuss the topic of clinical exercise trials.
All the guidelines of the American Thoracic Society on pulmonary function test are the results of the knowledge conference. The draft was compiled by two members, P.L.E and R.J.Z, referring to Medline's comprehensive literature retrieval results from 1970 to 200 1 and adding suggestions from other members. The draft revised the issues raised by the working group accordingly. The guide attempts to expand the previously published methods and provide a theoretical basis for each specific proposal. The final recommendation is the unanimous opinion of the Committee. The Committee recommended a five-year review of the guidelines and encouraged further research in controversial areas.
Background of the six-minute walk test:
There are several different forms of objective evaluation of functional compensation ability. Some provide a very complete evaluation standard (high technical content) for all systems involved in the operation process, while others only provide basic information, with low technical content but simple operation. The choice of specific forms is based on the problems that need to be solved in clinic and the available resources. The most popular clinical exercise tests are stair climbing, 6MWT, walking test before and after, exercise asthma detection, heart load test (such as Bruce scheme) and cardiopulmonary exercise test in order of complexity. Other professional organizations have published the standard of heart stress test.
The evaluation of functional compensation ability usually only asks patients the following questions: "How many floors can you climb or how many blocks can you walk?" However, patients with different memories may overestimate or underestimate their actual functional compensation ability. Objective measurement is usually better than self-report. In the early 1960s, Balke put forward a simple method to evaluate the function compensation ability, that is, to measure the walking distance within a specified time. Then, a 12 minute outdoor walking test was developed to measure the energy of healthy people. Walking test is also suitable for evaluating the dysfunction of patients with chronic bronchitis. It is difficult to accommodate and let patients with respiratory diseases walk 12 minutes, and the effect of walking for 6 minutes is the same as that of walking 12 minutes. A recent review of functional walking tests holds that "compared with other walking tests, 6MWT is easier to manage, more tolerant and more reflective of daily activities".
6MWT is simple and easy to operate. It only needs a corridor of 65,438+000 feet (about 30 meters), without advanced training of sports equipment or technicians. Walking is an activity that everyone should do except the seriously ill. This test measures the distance that patients walk quickly on flat and hard ground in 6 minutes. It evaluates the overall response of all systems during exercise, including lung, cardiovascular system, systemic circulation, peripheral circulation, blood, neuromuscular units and muscle metabolism. It does not provide detailed information about the functions of different organs and systems involved in exercise or the exercise restriction mechanism like the maximum cardiopulmonary exercise test. Self-paced six-minute walking test to evaluate the level of sub-large-scale functional compensation. Most patients can't reach the maximum exercise during the six-minute walking test. They choose their own exercise intensity and allow them to stop walking and rest during the test. However, since most activities in daily life need to be completed at the second maximum level of exercise, the six-minute walking test can best reflect the level of functional compensation ability that can complete daily physical activities.
Indications and limitations of six-minute walking test;
6MWT is mainly used to measure the response of patients with moderate or severe heart or lung diseases to drug intervention, and can also be used to evaluate patients' functional status or predict morbidity and mortality (table 1 is a list of indications). In fact, after using 6MWT, the researchers think that its clinical effect (or the best trial) in determining the functional compensation ability of patients with these diseases or the changes of functional compensation ability after intervention has not been fully confirmed. The application of 6MWT in various clinical situations needs further study.
Table 1. Indications of six-minute walking test
Lung transplantation
pneumonectomy
Lung volume reduction surgery
Lung rehabilitation
chronic obstructive pulmonary disease (COPD)
Pulmonary hypertension
cardiac failure
pulmonary cystic fibrosis
Peripheral vascular disease
Fibromyalgia
Elderly patients
cardiac failure
idiopathic pulmonary arterial hypertension
Regular cardiopulmonary exercise test can comprehensively evaluate the response to exercise, objectively detect the damage of compensatory ability and function, determine the appropriate exercise intensity needed to prolong exercise, quantify the factors limiting exercise and clarify the basic pathophysiological mechanisms such as the role of different organ systems in exercise. 6MWT did not measure the maximum oxygen consumption, nor did it clarify the causes of dyspnea and the reasons or mechanisms of activity limitation after exercise. The information provided by 6MWT should be used as a supplement rather than a substitute for cardiopulmonary exercise test. Although there are many differences between the two functional tests, there are also good correlation reports. For example, there is a significant correlation between 6MWD and peak oxygen consumption in patients with advanced lung diseases (r = 0.73).
In some clinical cases, 6MWT can better evaluate the daily living ability of patients than peak oxygen consumption. For example, the correlation between 6MWD and formal quality of life test is good, and the change of 6MWT after interventional therapy is related to the improvement of patients' dyspnea. In COPD patients, 6MWT (coefficient of variation is about 8%) is more repetitive than FEV 1.0. Compared with 6MWT, the questionnaire test results of functional status are more variable in a short time (22-33%).
Walking back and forth test is similar to 6MWT, but it uses the sound signal of magnetic tape to adjust the speed of walking back and forth (43-45) at the distance of 10 meter. The walking speed will increase every minute, and the experiment will end when the patient can't reach the turn-back place within the specified time. This exercise process is similar to the maximum incremental exercise load test limited by symptoms. The advantage of round-trip walking test is that the correlation with peak oxygen consumption is better than that of 6MWT. Its disadvantages include poor effect, small scope of application and many potential cardiovascular problems.
Contraindications of six-minute walking test:
The absolute contraindications of 6MWT include unstable angina pectoris or myocardial infarction within 1 month. Relative contraindications include resting heart rate exceeding 120 beats/min, systolic blood pressure exceeding 180mmHg and diastolic blood pressure exceeding 100mmHg.
In any of the above cases, the patient should inform the doctor who applied for or instructed the examination, so that he can make a clinical evaluation and decide whether to carry out the examination. Before the examination, you should also review the ECG results within 6 months. Stable angina pectoris is not an absolute contraindication of 6MWT, but patients should be tested after using drugs for angina pectoris and prepare nitrate drugs for emergency treatment.
Theoretical basis of six-minute walking test;
Patients with the above risk factors have an increased risk of arrhythmia or cardiovascular disease during the trial. However, patients can decide the intensity of exercise according to their own situation during the experiment. Thousands of elderly people, patients with heart failure or cardiomyopathy have conducted experiments without ECG monitoring, and no serious adverse events have occurred. The above contraindications are based on the general view of researchers on the safety of 6MWT, out of caution. If these patients undergo 6MWT, no one knows whether there will be adverse events, so it is listed as a relative contraindication. (However, we strongly recommend that doctors do it under the supervision of the new store to minimize the risk of adverse events. )
Equipment required for six-minute walking test:
Preparation of patients for six-minute walking test;
Comfortable to wear.
Wear shoes suitable for walking.
Patients should use assistive devices (crutches, walkers, etc.). ) used in the experiment.
The patient's usual treatment plan should continue.
Diet should be light before the exam.
Patients should avoid excessive exercise within 2 hours before the test.
Measurement process of six-minute walking test:
Six-minute walking test practice test;
Practical experiments can be considered, but they do not need to be carried out in all medical institutions. If the exercise test is conducted, it is necessary to wait at least 1 hour before the second test, and the highest value of these two tests is taken as the baseline value of the patient.
Theoretical basis of practice test;
It is reported that the distance of the second six-minute walking test in one day only increased slightly, ranging from 0- 17%. A multicenter study of 470 patients with severe COPD showed that the patients received 6MWT twice, instead of on the same day, and the average increase of the second time was only 66 feet (5.8%) compared with the first time.
Twice a week, the results often reach a platform (without intervention). The effect of training is to improve coordination, find a suitable stride and overcome nervousness. /kloc-the effect of this practice or training has not been reported after 0/month, but it seems that it will gradually weaken (not lasting) after a few weeks.
Oxygen therapy in six-minute walking test:
If you need oxygen when walking at ordinary times, and intend to carry out experiments (after giving intervention other than oxygen therapy), you need to give the same oxygen supply mode and flow rate when walking. If the symptoms get worse during the experiment and the oxygen flow needs to be increased, it should be recorded on the worksheet and taken into account when explaining the change of six-minute walking distance. The report should also indicate the oxygen supply device: if the patient carries liquid oxygen or pushes/pulls oxygen cylinders, it is pulse oxygen supply or continuous oxygen supply, or the technician walks behind the patient with oxygen source (not recommended). Pulse and blood oxygen saturation should be measured at least 10 minutes after any change in oxygen supply.
Theoretical basis of oxygen therapy;
For patients with COPD or interstitial lung disease, oxygen can increase 6MWD. Studies on patients with severe respiratory diseases show that carrying oxygen bags (but not used for oxygen supply) can reduce 6MWD by 65,438+04% on average, but it can increase 6MWD by 20-36% when used for oxygen supply during the experiment.
Explain the results of the six-minute walking test;
Most 6MWTs will be carried out before and after the intervention. The first question to be answered after the completion of the two trials is whether the patient has made significant clinical improvement. There is a good quality control program, which is tested by the same technician. Through the practice test of 1 to 2, the short-term repeatability of 6MWD under these conditions is very good. Which of the following ways to express the change of 6MWD has the greatest clinical significance is still inconclusive. Percentage of absolute value, or percentage change of expected value. Before further study, we suggest using absolute values (for example, the patient's 6MWD increased by 50 meters).
The improvement of patients' 6MWD is not as obvious as the clinical improvement. In a study of 1 12 stable patients with severe COPD (half of them are women), the minimum 6MWD change associated with significant clinical changes is 54 meters (95% confidence interval is 37-7 1 meter). This study shows that for patients with chronic obstructive pulmonary disease, interventions that can increase 6MWD by more than 70 meters are of great significance (the reliability is 95%). The observation and study of 45 elderly patients with heart failure showed that the average change of 6MWD related to the significant change of clinical condition was 43 m. 6MWD is more sensitive to reflect the deterioration of heart failure symptoms than the improvement.
Average change of six-minute walking test after intervention:
In one study, patients with COPD or interstitial lung disease received oxygen inhalation (6 liters/minute), and the average 6MWD increased by about 83 meters (36%). An international COPD study shows that the use of inhaled hormone therapy can increase 6MWD by an average of 33 meters (8%). The study of exercise effect and diaphragmatic strength training shows that 6MWD can increase 50 meters (20%). The decrease of lung volume in very severe COPD patients can increase 6MWD by an average of 55 meters (20%).
A recent study shows that cardiac rehabilitation can increase the 6MWD of patients with heart disease by 170 m (15%). In 25 elderly patients with heart failure, ACEI (captopril 50 mg/day) can increase 6MWD by 64 meters (39%) on average, while the placebo group only increased by 8% on average.
Interpretation of functional state measurement results:
At present, there are no data results using the standard 6MWT method in healthy people. In one study, the median 6MWD of17 healthy men was about 580 meters, and that of 173 healthy women was about 500 meters. Another study reported that the average 6MWD of 565,438+0 healthy elderly people was 630m (53). Different research groups, different ways and frequencies of encouragement, different corridor lengths and different times of pre-test exercises will lead to different average 6MWD of healthy people. Age, height, weight and sex are independent influencing factors of 6MWD in healthy people, so these factors should be considered when interpreting the results. We encourage researchers to use the standard procedure of 6MWT to obtain data results of normal population.
The decrease of 6MWD is not specific and diagnostic. When the 6MWD drops, a comprehensive inspection should be conducted to find out the reason. The following related tests can be referenced: lung function, cardiac function, ankle-brachial ratio, muscle strength, nutritional status, bone function and cognitive function.
The conclusion of the six-minute walking test:
6MWT is a method to detect functional compensation ability, which is suitable for patients with at least moderate injury. This test is widely used in clinical evaluation of cardiopulmonary diseases before and after treatment and intervention. This guide provides the standard method of 6MWT. The committee that drew up this guide hopes that it will encourage people to do more in-depth research on 6MWT and make different studies comparable.