The Oxygen Car (OXCAR) in Pulmonary Rehabilitation of Patients with Respiratory Failure

Abstract

Training exercise with associated oxygen therapy is important in pulmonary rehabilitation. Some European countries are proposing an oxygen car (OXCAR*) as a simple and motivating solution to training exercise in the hospital or at home. The little car, carrying a cylinder of 3 cubic meters of oxygen, weighs 70 kg overall. An original system supplies oxygen to the mask only if the car is moving; this avoids inhalation of oxygen when the patient is at rest and obliges the patient to make an effort in order to obtain oxygen. Cylinders obtained from drugstores have enough oxygen for about 15 hours at a flowrate of 3 l/min. An easily adjustable brake (resistance device) varies the effort required by the patient. The power spent in walking the OXCAR under various conditions of brake and speeds was quantified on a treadmill, measuring the oxygen intake (VO₂ STPD). Work performed by pushing the oxygen car showed a remarkable proportionality to the speed of walking on a zero incline. The correlation between VO₂ and speed in km/h in the range of usual speeds (2 to 5 km/h, ie, 30 to 85 m/min was almost linear (r = 0.98). The energy outlay to push the OXCAR on a level floor at 3 km/h (50 m/min) is about 0.75 l/min of oxygen (=40 watts). The OXCAR is able to turn on a spot, so it can be used in narrow corridors or very small areas. Forty-one of 50 patients (82 per cent) with respiratory failure who were trained with the OXCAR daily for a week found that pushing the car provided greater motivation for engaging in training exercise than did walking, going up and down a stool, climbing stairs, or bicycling.