Effect of Heliox Breathing on Flow Limitation in Chronic Heart Failure Patients

¹ Istituto di Fisiologia Umana I, Università degli Studi di Milano, Milan, Italy
² Dept of Critical Care and Pulmonary Services, Evangelismos General Hospital, Medical School, University of Athens, Athens, Greece

^* To whom correspondence should be addressed. E-mail: matteo.pecchiari{at}unimi.it.

	Abstract

Patients with chronic heart failure (CHF) exhibit orthopnea and tidal expiratory flow limitation in the supine position. It is unknown whether the flow limiting segment occurs in the peripheral or central part of the tracheobronchial tree. The location of the flow limiting segment can be inferred from the effects of heliox (80% He, 20% O₂) administration. If maximal expiratory flow increases with this low density mixture, the choke point should be located in the central airways, where the wave-speed mechanism dominates. If the choke point were located in the peripheral airways, where maximal flow is limited by a viscous mechanism, heliox should have no effect on flow limitation and dynamic hyperinflation.

Tidal expiratory flow limitation, dynamic hyperinflation and breathing pattern were assessed in 14 stable CHF patients during air and heliox breathing at rest in sitting and supine position.

No patient was flow limited in the sitting position. In the supine posture 8 patients exhibited tidal expiratory flow limitation on air. Heliox had no effect on flow limitation, dynamic hyperinflation and only minor effects on the breathing pattern.

Lack of density dependence of maximal expiratory flow implies that in CHF patients the choke point is located in the peripheral airways.