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Figure 1 | Acta Veterinaria Scandinavica

Figure 1

From: Effect of sedation with detomidine and butorphanol on pulmonary gas exchange in the horse

Figure 1

Distribution of ventilation-perfusion ratio (V A /Q) in one horse (444 kg). The top panel represent the VA/Q distribution in an unsedated horse (Unsedated). The middle panel represent the VA/Q distribution 15 minutes after intravenous detomidine administration (Detomidine). The lower panel represent the VA/Q distribution 15 minutes after additional intravenous injection of butorphanol (Detomidine & Butorphanol). Note the impaired arterial oxygen tension (PaO2) during sedation in the middle and bottom panel. During sedation with detomidine, cardiac output (Qt) decreased and there was an increase in ventilation-perfusion mismatch (broader base of ventilation-perfusion ratio and increased SD of blood flow log distribution (log SDQ)) compared to the unsedated horse. The intrapulmonary shunt was minimal. During sedation with detomidine and butorphanol, the impaired PaO2 was a result of persistent low cardiac output and an additional reduction in expired minute ventilation (VE). After addition of butorphanol the distribution of VA/Q improved as the reduced ventilation and persistent low blood flow matched well. No increase in intrapulmonary shunt was evident during subsequent butorphanol administration.

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