Reflex responses to positive end-expiratory pressure

When positive end-expiratory pressure (PEEP) is applied to rabbits there is a large depression of cardiac output. The authors investigated the baroreceptor and lung stretch reflex responses to PEEP in rabbits to determine if reflex responses are important in causing the depression of cardiac output which occurs with PEEP. With PEEP there was a depression of cardiac output and blood pressure, no change in heart rate, and an increase in systemic vascular resistance. The responses to PEEP were similar after vagotomy and after a large dose of atropine, but, after treatment with phenoxybenzamine, blood pressure was lower during PEEP and systemic vascular resistance did not increase. The data suggests that lung stretch response is not an important factor in the cardiovascular response to PEEP in rabbits.