Pulmonary artery, aortic and oesophageal pressure changes during high intensity treadmill exercise in the horse: a possible relation to exercise‐induced pulmonary haemorrhage

Abstract

Summary This study investigated changes in packed cell volume (PCV), pulmonary artery and aortic pressures, and the interaction between oesophageal pressure and pulmonary artery and aortic pressures during strenuous exercise in the horse. It was hypothesised that oesophageal pressure changes summate with pulmonary artery and aortic pressures during exercise and contribute to exercise‐induced pulmonary haemorrhage (EIPH). Acute treadmill exercise (10 m/sec, 3° incline) produced increases in heart rate (HR) from 50 to 202 beats/min; mean pulmonary artery pressure (PAP) from 28 to 80 mmHg; mean aortic pressure (AP) from 108 to 157 mmHg; and PCV from 0.35 to 0.52 litres/litre. EIPH was observed in three of seven horses after treadmill exercise, but no differences in the above variables were observed between the two groups of horses. Electronic subtraction of the oesophageal pressure signal from PAP and AP signals indicated peak transmural pressures of approximately 150 mmHg pulmonary and 175 mmHg aortic pressure. The elevated PAP associated with exercise appeared related more to increased HR and less to PCV (blood viscosity) or AP (bronchial). Both pulmonary artery and aortic peak transmural vascular pressures were substantially influenced by oesophageal pressure changes; peak and mean pulmonary artery and aortic pressures were significantly higher than resting pressures, and may conceivably contribute to EIPH.

Técnica para avaliação da pressão arterial pulmonar de equinos durante o exercício progressivo em esteira rolante

“…O primeiro relato de que a PAP aumenta em equinos durante o exercício, em relação a valores de repouso, foi de Parks & Manohar (1983). Tal incremento, que ocorre visando otimizar o influxo de sangue para os pulmões para suprir a elevada demanda de oxigênio durante o esforço, é substancialmente maior em equinos do que em outras espécies, devido ao grande volume de massa muscular recrutado para a realização do exercício (Erickson et al 1990). Posteriormente, Magid et al (2000) verificaram valores de PAP (mmHg) média de equinos em posição quadrupedal em repouso (27,6±1,1) e, durante o exercício intenso (107,7±4,5).…”

“…Estudos avaliando a PAP durante o exercício tem sido realizados buscando informações sobre a etiologia e prevenção da hemorragia pulmonar induzida pelo exercício, já que a hipertensão capilar pulmonar parece predispor à ocorrência da enfermidade (Erickson et al 1990, Manohar et al 1993, Mills et al 1996, Ducharme et al 1999, Funkquist et al 2000, Magid et al 2000. A avaliação de PAP em testes ergométricos tem revelado ainda sinais de alterações hemodinâmicas em equinos apresentando insuficiência mitral (Gehlen et al 2004) e fibrilação atrial (Gehlen et al 2006).…”

La mécanique ventilatoire en tant que facteur limitant de la santé des animaux domestiques

“…Bien que de nombreuses hypothèses aient été avancées pour expliquer ce phénomène, il est hautement probable que ces hémorragies soient dues à des ruptures de vaisseaux pulmonaires, engendrées par d'importantes et soudaines modifications de la pression transmurale . En effet, l'exercice intense induit d'une part, une augmentation considérable des pressions sanguines pulmonaires (Erickson et al 1990) et d'autre part, des pressions très négatives dans les voies aériennes (Art et al 1988). Des changements soudains de cette pression transmurale dans un poumon distendu par l'hyperventilation constituent un stress largement suffisant pour induire des lésions de ces parois vasculaires (Fu et al 1992 ;Poole & Erickson, 2007).…”

Exercise‐induced pulmonary perfusion redistribution in heaves

“…During near maximal exercise, PAP mean ranges upward of 80 torr in healthy horses (Erickson et al 1990). No report concerning the measurement of PAP mean in the exercising 'heavey' horse was found in the literature.…”