Open AccessPlethysmographic Comparison of Breathing Pattern in Heaves (Recurrent Airway Obstruction) Versus Experimental Bronchoconstriction or Hyperpnea in Horses
Author(s) -
Hoffman Andrew M.,
Oura Trisha J.,
Riedelberger Klaus J.,
Mazan Melissa R.
Publication year - 2007
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/j.1939-1676.2007.tb02945.x
Subject(s) - medicine , bronchoconstriction , ventilation (architecture) , hyperpnea , anesthesia , tidal volume , airway obstruction , abdomen , cardiology , respiratory system , airway , surgery , mechanical engineering , engineering
Background : Horses with recurrent airway obstruction (heaves) are described as exhibiting “increased abdominal effort,” but it is unknown whether this translates to an effective contribution to ventilation. Hypothesis : We hypothesized that heaves is characterized by asynchrony between rib cage and abdominal motions, and that the abdominal component is the major contributor to ventilation. Animals : The rib cage versus abdominal motion in naturally occurring heaves (n = 15) was compared to controls at rest (n = 7) and during hyperpnea because of lobeline treatment, and the effects of histamine‐induced bronchoconstriction in controls (n = 10). Methods : Flow patterns, phase angle (9) between the rib and abdominal compartments, abdominal (V abd ) contribution to tidal volume (V T ), and lung mechanics were measured. Results : Findings unique to the heaves group included the loss of biphasic expiratory flow, severely increased 9 with the abdomen consistently lagging behind the rib cage, and a reduced contribution of the abdomen to ventilation. A subgroup of heaves (n = 5) with abdominal paradox showed a significant ( P < .05) reduction in tidal volume, and increased respiratory rate. Bronchodilation reduced 9 in heaves ( P = .06), but 9 remained significantly higher after bronchodilation than found in controls. Conclusions and Clinical Importance : We conclude that breathing pattern in horses with heaves is characterized by severe rib cage/abdominal asynchrony, with the rib cage motion in synchrony with flow, therefore dominating ventilation. In a subset of heaves, the abdominal compartment (diaphragm, abdominal muscles) was completely out of synchrony with flow (“abdominal paradox”) despite the clinical appearance of “increased abdominal effort.”