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Ventilation‐perfusion relationships during graded exercise in the Standardbred trotter
Author(s) -
NYMAN G.,
BJÖRK M.,
FUNKQUIST P.,
PERSSON S. G. B.,
WAGNER P. D.
Publication year - 1995
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1995.tb04892.x
Subject(s) - cardiology , ventilation (architecture) , perfusion , hypoventilation , medicine , arterial blood , vo2 max , anesthesia , venous blood , cardiac output , hemodynamics , heart rate , respiratory system , blood pressure , thermodynamics , physics
Summary The aim of this study was to evaluate pulmonary function in Standardbred trotters during graded exercise. The exercise test consisted of 4 work loads corresponding to 10%, 42%, 70% and 96% of the individual V̇O 2max . Oxygen uptake was detected from an open bias flow system without valves. Cardiovascular and haemodynamic data were recorded at walk and during steady state exercise in 7 horses. Pulmonary gas exchange was assessed by conventional blood gas variables (arterial and mixed venous blood gas tensions) and the ventilation‐perfusion distribution V̇ A |Q̇ as estimated by the multiple inert gas elimination technique. The dispersion of perfusion and ventilation distribution respectively (SDQ) and the difference between measured PaO 2 and that predicted on the basis of amount of ventilation‐perfusion mismatching and shunt that was observed (predicted‐measured), were determined. The latter reflects mostly diffusion limitation. At the highest work load the PaCO 2 increased to 50.3 torr. V̇ A |Q̇ inequality increased significantly with exercise [mean log = 0.32 ± 0.03 (walk) and 0.46 ± 0.06 (heavy exercise), P < 0.01]. Alveolar‐capillary diffusion limitation of oxygen was evident at and above exercise at 70% of V̇O 2max . The arterial hypoxaemia seen during the highest work load was a result of a) hypoventilation, accounting for 4%, b) increase in V̇ A |Q̇ mismatch, accounting for 41% and c) considerable diffusion limitation of oxygen, accounting for 55%.