Positive end-expiratory pressure differentially alters pulmonary hemodynamics and oxygenation in ventilated, very premature lambs.
In mature lungs, elevated positive end-expiratory pressure (PEEP) reduces pulmonary blood flow (PBF) and increases pulmonary vascular resistance (PVR). However, the effect of PEEP on PBF in preterm infants with immature lungs and a patent ductus arteriosus is unknown. Fetal sheep were catheterized at 124 days of gestation (term approximately 147 days), and a flow probe was placed around the left pulmonary artery to measure PBF. At 127 days, lambs were delivered and ventilated from birth with a tidal volume of 5 ml/kg and 4-cmH(2)O PEEP; PEEP was changed to 0, 8, and 12 cmH(2)O in random order, returning to 4 cmH(2)O between each change. Increasing PEEP from 4 to 8 cmH(2)O and from 4 to 12 cmH(2)O decreased PBF by 20.5 and 41.0%, respectively, and caused corresponding changes in PVR; reducing PEEP from 4 to 0 cmH(2)O did not affect PBF. Despite decreasing PBF, increasing PEEP from 4 to 8 cmH(2)O and 12 cmH(2)O improved oxygenation of lambs. Increasing and decreasing PEEP from 4 cmH(2)O significantly changed the contour of the PBF waveform; at a PEEP of 12 cmH(2)O, end-diastolic flow was reduced by 82.8% and retrograde flow was reestablished. Although increasing PEEP improves oxygenation, it adversely affects PBF and PVR shortly after birth, alters the PBF waveform, and reestablishes retrograde flow during diastole.
Polglase
Graeme R
GR
Fetal and Neonatal Research Group, Department of Physiology, Monash University, Australia. gpolglase@obsgyn.uwa.edu.au
Morley
Colin J
CJ
Crossley
Kelly J
KJ
Dargaville
Peter
P
Harding
Richard
R
Morgan
David L
DL
Hooper
Stuart B
SB
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D005333:Fetus / Q000502:physiology; D005865:Gestational Age; D006439:Hemodynamics / Q000502:physiology; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration; D011651:Pulmonary Artery / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology*; D012121:Respiration, Artificial; D012756:Sheep; D014655:Vascular Resistance