Lung mechanics during induced bronchoconstriction.
Pellegrino, Riccardo, Owen Wilson, Gilbert Jenouri, Joseph R. Rodarte.
Pulmonary Section, Baylor College of Medicine, One Baylor Plaza,
Houston, Texas 77030; and Fisiopatologia Respiratoria, Ospedale A.
Carle, 12100 Cuneo, Italy
APStracts 3:0174A, 1996.
In order to elucidate differences in lung mechanics, we investigated
the relative changes of partial forced expiratory flows, and lung
resistance (RL) and dynamic elastance (Edyn) and the effects of a
deep breath on maximal flows, Edyn and RL in eight asthmatics and
eight normal individuals during bronchial challenges with
methacholine (MCh), histamine (Hist), and adenosine 5'-triphosphate
(ATP). Asthmatics also underwent a challenge with hyperventilation of
dry and cold air. Lung volumes and flows were measured in a volume
-displacement body plethysmograph. Forced expiratory flows at 50%
(p50) and 30% (p30) of control FVC were measured from a partial vital
capacity maneuver starting from about 70% of control FVC and at the
same volumes, m 50 and m30, from a full FVC maneuver. RL and Edyn
were calculated over at least 10 tidal breaths from the linear
equation of motion. RL was also partitioned in inspiratory (RLi) and
expiratory lung resistance (RLe). Asthmatics were more sensitive to
all constrictor agents than normals (p <0.001, ANOVA). All
individuals were more sensitive to MCh and Hist than ATP on a molar
basis and as judged by maximum response. Different constrictor agents
did not induce specific patterns of relative changes of p50 or p30,
RL and Edyn. For a given decrement of 50 and p30, RL increased
significantly more in normals than in asthmatic individuals. The
ratio of RLi to RLe was always less than 1 at baseline, but became
greater than 1 in the majority of asthmatics and normals when RL
exceeded 12.2 +/- 0.9 cm H2/L/s suggesting tidal inspiration may have
induced transient bronchodilation in more constricted subjects.
Received 2 August 1994; accepted in final form 27 February 1996.
APS Manuscript Number A789-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96