Obesity Surgery, January 2015
Low cardiopulmonary fitness, measured by oxygen uptake peak (VO2pk), is associated with postoperative complications and mortality. Obese people have difficulty in performing the cardiopulmonary exercise test, which requires maximal exertion. The incremental shuttle walking test (ISWT) and 6-min walking test (6MWT) have been used to assess cardiorespiratory capacity, mortality, and complications in the postoperative phase. However, the physiological response elicited by these tests in obese people is unknown. This study analyzed and compared cardiopulmonary fitness (oxygen uptake [VO2] and CO2 output [VCO2]) in the ISWT and 6MWT in obese adults using a telemetry system.
Fifteen obese patients (10 women; mean age 39.4 ± 10.1 years; mean body mass index 43.5 ± 6.8 kg/m2) with normal forced vital capacity (% FVC 93.7) performed the 6MWT and ISWT in the field in this cross-sectional study. Metabolic (VO2pk, VCO2) and respiratory (minute ventilation; VE) variables were recorded using telemetry.
Obese patients performed the ISWT with an incremental and exponential cardiopulmonary response, with higher VO2pk (15.4 ± 2.9 ml/kg/min), VCO2 (1.7 ± 0.7 l/min), and VE (51.4 ± 21.3 l/min) than the 6MWT (VO2pk = 13.2 ± 2.59 ml/kg/min, VCO2 = 1.4 ± 0.6 l/min; VE = 41.2 ± 16.6 l/min (all p < 0.01). They also demonstrated more effort intensity, assessed by VO2, (p = 0.006) and heart rate (p = 0.04) in the ISWT than the 6MWT. In the 6MWT, patients showed a fast rise in ventilatory and metabolic response, reaching a plateau.
The ISWT test generated superior metabolic and ventilatory stress than the 6MWT and may be more suitable for assessing cardiopulmonary fitness than self-paced tests.