Brain perfusion during two patient-triggered ventilation modes in preterm infants

Cerebral blood flow (CBF) is greatly influenced by mechanical ventilation. Pressure support ventilation combined with volume guarantee (PSV-VG) is a new patient-triggered ventilation modality that offers the patient greater liberality than the classical synchronized intermittent mechanical ventilation (SIMV); and thus, it might have a different effect on CBF.

Aim: To compare, in preterm infants, the influence on CBF of PSV-VG and SIMV.

Methods: In a crossover study design, 39 consecutive preterm babies, were switched from SIMV to PSV-VG and back again to SIMV. Doppler and echocardiographic examinations were done 30–60min. after each switch to measure: (1) Doppler pulsatility index of blood flow in the anterior cerebral artery (PIaca); and (2) superior vena cava blood flow (SVCF). Infants were grouped according to patency of ductus arteriosus (Non-PDA group and PDA group).

Results: Infants had a median gestational age of 26 wks (range, 22.9–34.7) and a birth weight of 770g (450–2450). Despite achieving similar gas exchange, ventilation pressures were significantly lower during PSV-VG. Without significant changes in heart rate or blood pressure, the influence of ventilation mode on CBF was significantly different in the two subgroups. Whereas in the Non-PDA group CBF increased significantly during PSV-VG (lower PIaca (p=0.001) and higher SVCF (p=0.04)), no change was detected in the PDA group.

Conclusion: When the duct is closed PSV-VG results in higher CBF, probably due to the lower ventilation pressures, with concomitant rise in venous return and cardiac output. However, this effect seems to be blunted when the duct is open. The potential advantage of new ventilation modes with respect to impact on the hemodynamic situation may be counteracted by the presence of an open duct.