PRESSURE SUPPORT REDUCES INSPIRATORY EFFORT AND DYSPNEA DURING EXERCISE IN CHRONIC AIR-FLOW OBSTRUCTION

Exercise training has been of limited success in patients with severe chronic airflow obstruction (CAO), in part because of the reduced vent ilatory capacity and excessive dyspnea experienced. Pressure support ( PS) is a new form of mechanical ventilation which can effectively assi st ventilation when applied noninvasively to patients in acute respira tory failure. It was hypothesized that PS might also be used to improv e exercise performance, and ultimately physical conditioning, in ambul atory patients with CAO undergoing exercise training. To begin to addr ess this concept, the objectives of the present study were (1) to exam ine the feasibility of providing PS to exercising patients with CAO an d (2) to determine its effects on breathing pattern, inspiratory effor t, and dyspnea. Flow and volume, mouth, esophageal, and gastric pressu re were measured in seven patients with severe CAO (mean FEV(1) = 0.75 +/- SEM 0.09 L) performing constant workload bicycle exercise (33 +/- 6 watts) during control conditions and with the application of PS (ap proximately 10 cm H2O). PS increased minute ventilation as a result of changes in both tidal volume and respiratory rate. This occurred desp ite marked reductions in inspiratory effort, as indicated by the press ure-time integrals of esophageal (68 +/- 5% control, p < 0.0005) and t ransdiaphragmatic pressure (52 +/- 8% control, p < 0.0005). Using a 5- point bidirectional scale to assess changes in dyspnea, breathlessness improved significantly with the addition of PS (2.3 +/- 0.6, p < 0.05 ) and worsened to a similar degree when it was removed (2.1 +/- 0.5, p < 0.05). In conclusion, PS was well tolerated in exercising patients with severe CAO and effectively assisted ventilation, reducing both in spiratory effort and dyspnea. These results indicate that further work is warranted to determine whether PS can facilitate exercise recondit ioning and improve physical fitness in patients enrolled in an exercis e training program.