JMIR Publications

ABSTRACT

Background:

The six-minute walk test (6MWT) is a convenient method for assessing functional capacity in patients with cardiopulmonary conditions. It is usually performed in the context of a hospital clinic and so requires the involvement of hospital staff and facilities, with their associated costs.

Objective:

To develop a mobile-phone based system that allows patients to perform the 6MWT in the community.

Methods:

We developed two algorithms to compute the distance walked during a 6MWT using sensors embedded in a smartphone. One algorithm makes use of the global positioning system (GPS) to track the location of the phone when outdoors and hence compute the distance travelled. The other algorithm is meant to be used indoors and exploits the inertial sensors built into the phone to detect U-turns when patients walk back and forth along a corridor of fixed length. We included these algorithms in a smartphone app, integrated with wireless pulse oximeters and a back-end server. We performed Bland-Altman analysis of the difference between the distances estimated by the phone and by a reference wheel tape on 49 indoor tests and 30 outdoor tests, with 11 different smartphones (both iOS and Android operating systems). We also assessed usability aspects related to the app in a workshop with patients and clinicians using a technology acceptance model to guide discussion.

Results:

The mean difference between the smartphone-estimated distances and the reference values was -2.013 m (SD 7.84 m) for the indoor algorithm, and -0.80 m (SD 18.56 m) for the outdoor algorithm. The absolute maximum difference was, in both cases, below the clinically significant threshold. Two pulmonary hypertension patients, 1 cardiologist, 2 physiologists and one nurse took part in the workshop, where issues arising from the use of the 6MWT in hospital were identified. The app was demonstrated to be usable and the two patients with pulmonary hypertension were keen to use it in the long term.

Conclusions:

The system described in this paper allows patients to perform the 6MWT at a place of their convenience. Additionally, the use of pulse oximetry allows more information to be generated about the patient’s health status, possibly, more related to their real-life condition. Preliminary assessment has shown that the developed 6MWT app is highly accurate and well accepted by its users. Further tests are needed to assess its clinical value.