The 'Oxylog': an evaluation

The Oxylog is a portable instrument designed to measure the oxygen consumption ([Vdot]0 2 ) an ambulatory subject. Steady-state measurements have been made, using an Oxylog, of inspiratory volume ( [Vdot] 1 ) [Vdot]0 2 during bicycle ergometer exercise at work rates ranging from 30 to 150 W. These measurements have been compared with simultaneous measurements of expiratory volume ([Vdot] E ) and [Vdot]O 2 made using a dry gas meter and mass spectrometer. Four experiments were conducted, during which a total of 433 comparative measurements were made. In two experiments the Oxylog significantly underestimated [Vdot]O 2 (by 4-4 and 5-6%). Averaging over the four experiments, however, the underestimate reduced to 1-5%, which could be accounted for by a respiratory exchange ratio of approximately 0-9. There was, overall, no significant difference between [Vdot] 1 and [Vdot] E . It is concluded that the Oxylog is sufficiently accurate for the reliable determination of [Vdot]0 2 and of energy expenditure under field conditions.