Cardiopulmonary performance testing using a robotics-assisted tilt table: feasibility assessment in able bodied subjects

Abstract

Purpose: Robotics-assisted tilt table technology with integrated leg drives for basic stepping functionality is clinically available for patients with neurological impairments. Initially introduced for early rehabilitation, it provides cyclical stepping movement and physiological loading in immobilized patients. This technology provides stability and support in patients with neurological disorders for whom weakness, balance and coordination problems would preclude cardiopulmonary performance testing using a treadmill or cycle ergometer. This type of device may facilitate the estimation of peak oxygen uptake and other important cardiopulmonary performance parameters in patients who have neurological deficits. The aim of the present study was to assess the feasibility and safety of this device for peak cardiopulmonary performance testing in able-bodied subjects. Methods: A robotics-assisted tilt table (Erigo, Hocoma AG, Switzerland) was augmented with force sensors in the thigh cuffs and a work rate estimation algorithm. A custom visual feedback system was employed to guide the subjects' work rate and to provide real time feedback of actual work rate. Each subject carried out an incremental exercise test to the limit of functional capacity with a work rate increment of 5 W/minute in female subjects and 8 W/minute in males. Outcome measures were peak oxygen uptake (VO2peak), peak heart rate (HRpeak), respiratory exchange ratio (RER), peak work rate (WRpeak) and the Borg CR10 scale to measure exertion and leg fatigue. Results: 11 able-bodied subjects were included (9 male, 2 female; age 29.6±7.1 years: mean ± SD). Resting VO2 was 4.6±0.7 ml/kg/min and VO2peak was 32.4±5.1 ml/kg/min. All participants reached at least 85% of their predicted HRmax value. RER at peak VO2 was 1.02±0.07. Eight participants (72.7%) reached their peak VO2 in 8-12 minutes, which is considered the optimal duration. The average WRpeak was 65.7 W for males and 41.5 W for females. All participants reported a Borg CR10 value for exertion and leg fatigue of 7 or more. There were no serious adverse events. Conclusions: The robotics-assisted tilt table augmented with work rate estimation and a visual feedback system is a feasible and safe method for peak cardiopulmonary performance testing in able-bodied subjects. Future work will evaluate test-retest reliability and compare peak cardiorespiratory performance values with those obtained from a treadmill and a cycle ergometer. The approach will then be piloted in subjects with neurological impairments.