Deep-breath frequency in bronchoconstricted monkeys (Macaca fascicularis).
Deep-breath frequency has been shown to increase in spontaneously obstructed asthmatic subjects. Furthermore, deep breaths are known to be regulated by lung rapidly adapting receptors, yet the mechanism by which these receptors are stimulated is unclear. This study tested the hypothesis that deep-breath frequency increases during experimentally induced bronchoconstriction, and the magnitude of the increased deep-breath frequency is dependent on the method by which bronchoconstriction is induced. Nine cynomolgus monkeys (Macaca fascicularis) were challenged with methacholine (MCh), Ascaris suum (AS), histamine, or an external mechanical resistance. Baseline (BL) and challenge deep-breath frequency were calculated from the number of deep breaths per trial period. Airway resistance (Raw) and tissue compliance (Cti), as well as tidal volume, respiratory rate, and minute ventilation, were analyzed for BL and challenged conditions. Transfer impedance measurements were fit with the DuBois model to determine the respiratory parameters (Raw and Cti). The flow at the airway opening was measured and analyzed on a breath-by-breath basis to obtain the ventilatory parameters (tidal volume, respiratory rate, and minute ventilation). Deep-breath frequency resulting from AS and histamine challenges [0.370 (SD 0.186) and 0.467 breaths/min (SD 0.216), respectively] was significantly increased compared with BL, MCh, or external resistance challenges [0.61 (SD 0.046), 0.156 (SD 0.173), and 0.117 breaths/min (SD 0.082), respectively]. MCh and external resistance challenges resulted in insignificant changes in deep-breath frequency compared with BL. All four modalities produced similar levels of bronchoconstriction, as assessed through changes in Raw and Cti, and had similar effects on the ventilatory parameters except that non-deep-breath tidal volume was decreased in AS and histamine. We propose that increased deep-breath frequency during AS and histamine challenge is the result of increased vascular permeability, which acts to increase rapidly adapting receptor activity.
Dybas
Joseph M
JM
Biomedical Engineering Dept., Boston Univ., 44 Cummington St., Boston, MA 02215, USA.
Andresen
Catharine J
CJ
Schelegle
Edward S
ES
McCue
Ryan W
RW
Callender
Natasha N
NN
Jackson
Andrew C
AC
D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D017165:Ascaris suum / Q000502:physiology; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction / Q000187:drug effects; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D002199:Capillary Permeability / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D001239:Inhalation / Q000502:physiology*; D008168:Lung / Q000098:blood supply / Q000502:physiology; D008252:Macaca fascicularis / Q000502:physiology*; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D012123:Pulmonary Ventilation / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000187:drug effects; D013990:Tidal Volume / Q000187:drug effects
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D006632:Histamine