Introduction:
Postural orthostatic tachycardia syndrome (POTS) is a form of dysautonomia that can present as orthostatic tachycardia, dizziness, nausea, and anxiety, and many other symptoms that can be debilitating enough to cause functional impairment. The cardiopulmonary exercise test (CPET) has become a reliable test for evaluating the functional capacity (fc) in POTS patients. The test requires utilization of a bicycle ergometer, blood pressure apparatus, ECG, pulse oximeter, and a face mask that measures the oxygen uptake and carbon dioxide release. The 6-minute walk test (6MWT) is another test that can also be utilized to assess fc in patients.
Objective:
The aim of this study is to differentiate whether the 6MWT and CPET give similar results with regards to fc in POTS patients.
Methods:
A total of 27 POTS patients visiting the clinic consented to participate in the voluntary study. There were 2 males and 25 females, with ages between 16 to 58 years. For the 6MWT, we used wrist worn pulse oximeter, electronic tablet device, sphygmomanometer and a lap counter. Patients walked in a straight flat corridor which was marked at 3 meter intervals, for six minutes. At the end of 6 minutes, patients were asked to stop and the six minute walk distance (6MWD) was recorded. The predicted 6MWD, the distance the patient was expected to walk based on patient’s sex, age, height and weight was calculated by the application installed on the tablet. The percentage of the predicted 6MWD that was actually walked by the patients was calculated (6MWD % predicted), and considered as their fc. Using the electronic medical records, we obtained their CPET fc results, where fc was calculated as a percentage of the predicted maximal oxygen uptake per unit body weight per unit time (VO
2max
) that was actually consumed. The VO
2max
measurement depends on patient’s sex, age, weight and height. Pearson correlation coefficient was used to compare the results of the 6MWT (6MWD % predicted) and CPET (fc).
Results:
Pearson correlation coefficient shows that there is no linear association between the CPET (fc) results and 6MWT (6MWD % predicted) results in POTS patients, with p=0.3368.
Conclusion:
The results convey no statistically significant association between the CPET (fc) results and the 6MWT (6MWD % predicted) results in POTS patients; the results of the 6MWT were not similar to that of the CPET in terms of fc testing in POTS patients. This suggests that the 6MWT has limited utility in POTS patients.
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