Differential effect of recruitment maneuvres on pulmonary blood flow and oxygenation during HFOV in preterm lambs.
The effects of lung volume recruitment manouvres on pulmonary blood flow (PBF) during high-frequency oscillatory ventilation (HFOV) in preterm neonates are unknown. Since increased airway pressure adversely affects PBF, we compared the effects of two HFOV recruitment strategies on PBF and oxygenation index (OI). Preterm lambs (128+/-1 day gestation; term approximately 150 days) were anesthetized and ventilated using HFOV (10 Hz, 33% tI) with a mean airway pressure (Pao) of 15 cmH2O. Lung volume was recruited by either increasing Pao to 25 cmH2O for 1 min, repeated five times at 5-min intervals (Sigh group; n=5) or stepwise (5 cmH2O) changes in Pao at 5-min intervals incrementing up to 30 cmH2O then decrementing back to 15 cmH2O (Ramp group; n=6). Controls (n=5) received constant HFOV at 15 cmH2O. PBF progressively decreased (by 45+/-4%) and OI increased (by 15+/-6%, indicating reduced oxygenation) in controls during HFOV, which was similar to the changes observed in the Sigh group of lambs. In the Ramp group, PBF fell (by 54+/-10%) as airway pressure increased (r2=0.99), although the PBF did not increase again as the Pao was subsequently reduced. The OI decreased (by 47+/-9%), reflecting improved oxygenation at high Pao levels during HFOV in the Ramp group. However, high Pao restored retrograde PBF during diastole in four of six lambs, indicating the restoration of right-to-left shunting through the ductus arteriosus. Thus the choice of volume recruitment maneuvre influences the magnitude of change in OI and PBF that occurs during HFOV. Despite significantly improving OI, the ramp recruitment approach causes sustained changes in PBF.
Polglase
Graeme R
GR
School of Women's and Infants Health, M094 The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia. graeme.polglase@uwa.edu.au
Moss
Timothy J M
TJ
Nitsos
Ilias
I
Allison
Beth J
BJ
Pillow
J Jane
JJ
Hooper
Stuart B
SB
D000136:Acid-Base Equilibrium / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D035641:Chest Wall Oscillation; D005260:Female; D008168:Lung / Q000378:metabolism*; D010100:Oxygen / Q000097:blood*; D011247:Pregnancy; D011652:Pulmonary Circulation / Q000502:physiology*; D012756:Sheep
D010100:Oxygen