Influence of ventilatory technique on pulmonary baroinjury in baboons with hyaline membrane disease

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Abstract
To assess the influence of ventilatory technique on pulmonary baroinjury in experimental hyaline membrane disease, we randomized 24 premature baboons to six treatment groups according to ventilator (PPV, positive pressure ventilator; HFO, high frequency oscillator; HFI, high frequency flow interrupter) and O2 therapy Flo2 as clinically indicated, or Flo2 1.0). PaCO2 was adjusted by varying pressure amplitude, and for PPV, also by rate (< 60/min). HFO and HFI were set at a frequency of 10 Hz. Animals were cared for with standard NICU techniques until death or sacrifice at 11 days. One animal died at delivery and was excluded from data analysis. There were no intergroup differences in Paw, Pa/Ao2, PaCO2 or oxygenation index (IO2 = [Pa/AO2]/Paw) prior to death of the first study animal at 13 h. Animals who subsequently developed airleak had higher Paw, lower Pa/AO2, and lower IO2 during this period. The degree of airleak was significantly less with HFO compared to PPV or HFI. The effect of O2 exposure did not appear different with respect to the degree of airleak or the frequency of severe tracheal injury, although survival was shortened. Severe tracheal injury was more frequent with HFI compared to PPV or HFO. BPD was found only in 100% O2 exposed animals surviving > 1 wk. Management of premature baboons with HFO and appropriate O2 resulted in less severe airleak, 100% survival, and no evidence of severe tracheal injury or BPD. These outcomes were not achieved with clinically similar strategies using PPV or HFI.