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The preterm neonatal baboon (Papio cynocephalus) at 74-82%(134 to 147 days) of term gestation (180 days) with an amniotic fluid (AF) L/S ratio of <0.7 has been found to consistently develop HMD. Ten dated pregnancies (134-180 days) confirmed by ultrasound determination of biparietal diameter were delivered by C-section. Birthweights were 495-988 gms. AF collected at delivery showed L/S ratios from 0.47 to 1.0. Phosphotidylglycerol was absent in all. The 6 animals with L/S ratios <0.7 developed HMD. They required resuscitation at birth by intubation and mechanical ventilation. Tachypnea, severe retractions, and poor air entry were present. Chest X-rays were consistent with HMD. The course was typical of HMD with a significant O2 requirement for >24 hrs followed by clinical improvement, usually rapid. Symptomatic patent ductus arteriosus was not encountered clinically. HMD was confirmed pathologically in 2 animals who died of complications <5 days. Four of eight animals were successfully weaned from the ventilator. This study shows that the preterm (<147 day) baboon naturally develops HMD when the L/S ratio is<0.7 and that when supported by methods presently used for human neonates with HMD they have a reasonable chance of recovery and survival. The preterm baboon may serve as a valuable model for the study of not only acute HMD but also its course and consequences. (Supported by the Ladies Forum of the SWFRE)

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