Objective: Breathlessness is common in patients with cancer and is difficult to relieve. New approaches are required and need to be evaluated. This is difficult in part because there are no reliable measures of breathlessness. Ideally breathlessness should be linked to objective measures of ventilation. We have therefore explored the tolerability and repeatability of the incremental shuttle walking test (ISWT) in combination with a portable gas exchange measurement system (K4B2; Cosmed, Italy).
Method: 17 patients with lung cancer and an ECOG performance status of 0-2 have been recruited. The ISWT is performed twice on two consecutive days. The patient walks around a ten metre course at a speed dictated by audio signals from a tape cassette. The rate increases every minute until the patient is too breathless to continue or cannot maintain the required speed. Patients' breathe through a facemask attached to the K4B2 that allows ventilation, oxygen uptake and heart rate to be measured. Patients rate their breathlessness using a modified Borg scale. Repeatability was assessed as the standard deviation of the difference between tests (SDdiff) and the intraclass correlation coefficient (ICCC; valuesB/0.6 indicate poor repeatability).
Results: 16 patients completed the study and tolerated the facemask. One patient found the facemask too claustrophobic. Between day repeatability: Mean SDdiff ICCC Borg score 2.2 0.6 0.90 VO2 (ml/min) 1175 287 0.81 VE (L/min) 34.1 8.4 0.75.
Conclusion: The ISWT was acceptable and tolerable for the majority of patients. Using the Borg score as the main outcome, a within subject between day study would require 16 patients to reliably detect a change of 25% (power=90%).