Am. J. Respir. Crit. Care Med.,
Volume 160, Number 3, September 1999, 906-912
Pulmonary Rapidly Adapting Receptor Stimulation Does
Not Increase Airway Resistance in Anesthetized Rabbits
JERRY
YU,
JU F.
ZHANG,
ANDREW M.
ROBERTS,
LYNELL C.
COLLINS,
and
EUGENE C.
FLETCHER
Department of Medicine and Department of Physiology and Biophysics, University of Louisville, Louisville, Kentucky
In open-chest artificially ventilated rabbits, removal followed by replacement of positive end-expiratory pressure (PEEP maneuver) favors stimulation of airway rapidly adapting receptors (RARs). The
purpose of the present study was to determine whether activation of RARs can cause bronchoconstriction. We measured airway pressure, airflow, and tidal volume, and calculated dynamic lung compliance and total lung resistance. PEEP maneuver increased airway pressure swings (16.4 ± 4% above
control; p = 0.0016) and decreased compliance (to 84.8 ± 2.8% of control; p = 0.0002) without
changing resistance (108.0 ± 4.4% of control; p = 0.85). On the other hand, the resistance increased
greatly (93 ± 13%, p < 0.01) after intravenous injection of acetylcholine or electrical stimulation of
vagal efferents, indicating that our system could detect increases in the resistance. In a separate
group, we stimulated RARs by stroking the trachea with a cotton tip (tickling), tickling produced
cough, manifested by increased pressure and flow without resistance changing. These changes were
abolished after paralysis with succinylcholine. Because we did not detect an increase in airflow resistance during activation of RARs by the PEEP maneuver and tickling, we conclude that increase in resistance may not be an important reflex component of airway RARs.
