Journal of Applied Physiology, Vol 71, Issue 1 322-327, Copyright © 1991 by American Physiological Society
Effects of pulmonary restriction on hypercapnic responses of heart-lung transplant recipients
S. R. Duncan, F. T. Kagawa, M. R. Kramer, V. A. Starnes and J. Theodore
Department of Medicine, Stanford University Medical Center, California 94305.
Previous studies of hypercapnic ventilatory responses (HCVR) in human
heart-lung transplant recipients (HLTX) have yielded conflicting results.
We compared the HCVR of restricted transplant recipients (HLTX-R) to
recipients with normal pulmonary function (HLTX-N), and normal controls
(C). HLTX-R exhibited limited tidal volume responses, whereas their
frequency responses were essentially identical to those of other subjects.
Accordingly, HCVR of HLTX-R (1.45 +/- 0.59 l.min-1.Torr CO2(-1)) were
significantly depressed compared with both HLTX-N and C (2.90 +/- 0.55 vs
3.05 +/- 1.23, respectively) (P less than 0.02). Despite undoubtedly
greater ventilatory impedances, airway (mouth) occlusion pressure responses
(Pm0.1) during hypercarbia of HLTX-R (0.46 +/- 0.28 cmH2O) were similar to
those of C (0.43 +/- 0.20) and paradoxically blunted compared with HLTX-N
(0.83 +/- 0.36) (P less than 0.02). We conclude that pulmonary reflexes are
superfluous for maintenance of HCVR in HLTX with normal respiratory
mechanics, whereas the presence of moderate restriction results in profound
depression of CO2 responses among these subjects.
