Pressure support ventilation increases cardiac output in neonates and infants

Fifteen neonates and infants were investigated during pressure controlled ventilation (PCV) and pressure support ventilation (PSV) on a Servo 300 ventilator. Changes in cardiac output (aortic mean blood flow velocity) were assessed with the Doppler technique. During PSV cardiac output increased by 16% (P < 0.01) compared with PCV with equal ventilation. Mean airway pressure decreased significantly during PSV compared with PCV, which may explain the increased cardiac output. During PSV, when inspiratory/expiratory (I:E) relations are dependent on the patient, we found a lower I:E ratio compared with PCV. It can be assumed that at least part of the decreased mean airway pressure is caused by the lower I:E ratio. As the heart rate was unchanged, the variations in cardiac output were caused by alterations in stroke volume. It is concluded that a patient triggered mode should be preferred providing that the neonate/infant has the ability to elicit the ventilator's triggering system.