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Ventilation‐perfusion relationships during exercise in Standardbred trotters with red cell hypervolemia
Author(s) -
FUNKQUIST PIA,
WAGNER P. D.,
HEDENSTIERNA G.,
PERSSON S. G. B.,
NYMAN GÖREL
Publication year - 1999
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.2042-3306.1999.tb05199.x
Subject(s) - ventilation (architecture) , medicine , perfusion , treadmill , cardiology , hemodynamics , blood flow , anesthesia , mechanical engineering , engineering
Summary In order to evaluate the pulmonary gas exchange during exercise in Standardbred trotters with red cell hypervolaemia (RCHV), 12 horses with RCHV were compared with 9 normovolaemic (NV) horses. V̇ o 2 and V̇ co 2 were determined with an open bias flow system. Cardiovascular and haemodynamic data were recorded during exercise at 4 different speeds on a treadmill. 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 was estimated by the multiple inert gas elimination technique. V̇ A and AaD o 2 were calculated. Dispersions of perfusion and ventilation distribution (SDQ, SDV) were determined. HR, RR, Q̇t, V̇ o 2 , V̇ A , log SDV, C(a‐***v) o 2 and lactate did not differ between groups. The degree of hypoxaemia was more pronounced in the RCHV than in the NV (Pa o 2 = 54 and 59 mmHg; AaDO 2 = 41 and 34 mmHg in RCHV and NV, respectively, at highest workload). Further, pH was lower in the RCHV and Pa co 2 and V̇CO 2 was significantly higher in the RCHV during the course of exercise (pH = 7.24 and 7.29; Pa co 2 = 56 and 51 mmHg; V̇ co 2 = 156 and 135 ml/kg x min in RCHV and NV, respectively, at highest workload). The Pa o 2 predicted from the V̇ A /Q̇ distribution was higher than actually measured in blood during heavy exercise which may suggest a certain diffusion limitation over the alveolar‐capillary membranes in both groups but there was no difference between the 2 groups. The more pronounced hypoxaemia observed in RCHV trotters was mainly caused by increased V̇ A /Q̇ mismatch expressed as a significantly increased log SDQ (0.78 and 0.45 in RCHV and NV, respectively, at highest workload).