EFFECT OF THEOPHYLLINE ON EXERCISE PERFORMANCE IN PATIENTS WITH SEVERE CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background - Theophylline is a well known bronchodilator which has bee n used for more than 50 years in the treatment of obstructive pulmonar y diseases. In patients with severe chronic obstructive pulmonary dise ase whose cardiopulmonary performance is limited by their ventilatory capacity the administration of theophylline may improve exercise perfo rmance. Methods - A randomised, placebo controlled, double blind, cros sover trial was conducted in 22 patients with severe but stable diseas e. The patients (mean age 68 years) were studied before and after one month of placebo and one month of treatment with a sustained release p reparation of theophylline administered orally, The theophylline dose was adjusted until a blood level above 55.5 mu mol/l was achieved. The two treatments were administered in random order and separated by a t wo week washout period. After theophylline was administered for one mo nth a mean level of 68.2 mu mol/l was achieved. Pulmonary function tes ts, arterial blood gas measurements, maximal voluntary ventilation (MV V), and an incremental exercise test were performed before (baseline) and at the end of the first and second month of treatment. Results - P ulmonary function tests showed no improvement in the flow parameters b ut showed an improvement in MVV after treatment with theophylline. Pul monary gas exchange was improved after theophylline (resting arterial Po-2 8.91 v 8.59 kPa, PCO2 5.38 v 5.56 kPa). The incremental exercise study showed improvement in maximal work rate (86.5 v 75.0 watts) and maximal ventilation (Vemax) (46.7 v 43.0 l/min). The dyspnoea index on maximal effort (Vemax/MVV), anaerobic threshold, and oxygen pulse rem ained unchanged. Resting and exercise heart rate were higher after the ophylline. Conclusions - Theophylline improved cardiorespiratory perfo rmance in these patients with severe chronic obstructive pulmonary dis ease mainly by increasing the ventilatory capacity.