Previous studies demonstrated that high-frequency oscillatory ventilation (HFOV) begun at birth limits the development of alveolar proteinaceous edema in premature monkeys at risk for hyaline membrane disease (HMD). We hypothesized that exogenous surfactant combined with HFOV would lead to even further reductions in edema. Twenty Macaca nemestrina monkeys were delivered at 134 d gestation (term = 168 d) and treated with either HFOV or conventional mechanical ventilation (CMV) from the first breath; modified bovine surfactant (Survanta [beractant]) was introduced into the trachea over the first few minutes of life. These animals were compared with 20 animals treated with either CMV or HFOV but without surfactant. At 6 h the lung was rapidly frozen in situ during inflation for determination of the volume fraction of alveolar edema. The combined use of surfactant and HFOV from the first breath reduced alveolar proteinaceous edema (3 +/- 1%; mean +/- SEM) from that seen with CMV alone (27 +/- 3%, p < 0.0001), CMV after surfactant (21 +/- 3%, p < 0.0001), and HFOV alone (13 +/- 3%, p < 0.015). We conclude that the use of surfactant with HFOV after premature birth is superior to either surfactant or HFOV alone in reducing lung injury during the first few hours of life. We speculate that this reduction in lung injury may reduce the incidence or severity of bronchopulmonary dysplasia.
The effect of oxygen breathing on shunt and ventilation-perfusion ratios (VA/Q) in anesthetized rats was studied using a modification of the multiple inert gas elimination technique. Base-line analyses showed hypoxemia in some animals breathing room air (arterial O2 tensions 48-70 Torr) associated with intrapulmonary shunts ranging from 0 to 22%, and variable low VA/Q lung regions as determined by calculation of the inert gas arterial-alveolar difference curve. Of nine rats that breathed 100% oxygen for 30 min, three showed increases in shunt (0% leads to 19%, 1.5% leads to 16%, 11% leads to 40%). These three animals had larger preexisting low VA/Q regions than the six that developed no shunt (0.48 +/- 0.15 vs. 0.17 +/- 0.03 (mean +/- SD); P less than 0.05). These data are compatible with the theory of absorption atelectasis. This study documents the usefulness of the inert gas elimination technique for studying pulmonary gas exchange problems in small animals.
Total liquid ventilation (LV) lowers airway pressures and potentially reduces barotrauma in models of hyaline membrane disease. LV eliminates surface tension by eliminating the air-perfluorochemicals (PFC) interface but does not eliminate interfacial tension (IT) at the lung/PFC interface. We hypothesized that pretreatment with exogenous surfactant before LV would shift the overall pressure-volume (PV) curve to the left, compared with LV without surfactant. Sequential quasi-static PV curves were obtained in 10 excised lungs (saline, air, PFC), with one-half randomized to exogenous surfactant replacement before LV. Analysis revealed that maximal inflation pressures were reduced during LV compared with baseline air curves. Addition of exogenous surfactant to LV further reduced maximal inflation pressures. A novel approach was used to transform these PV curves to estimates of in situ IT-volume curves. Estimated maximal IT at 20 ml/kg in preterm lamb lungs on air inflation after surfactant was 51 mN/m, compared with 40 mN/m for LV alone and with 27 mN/m for the combination of surfactant and LV. We conclude that the IT-reducing properties of the PFC studied (perflubron) can be augmented through the use of exogenous surfactant.
Chronic lung disease in prematurely born infants, defined as the need for increased inspired oxygen at 28 days of age, was thought to be more common in some institutions than in others. To test this hypothesis, we surveyed the experience in the intensive care nurseries at Columbia and Vanderbilt Universities, the Universities of Texas at Dallas, Washington at Seattle, and California at San Francisco, the Brigham and Women's Hospital in Boston, Texas Children's Hospital in Houston, and Mt Sinai Hospital in Toronto. The survey included 1,625 infants with birth weights of 700 to 1,500 g. We confirmed the relationship of risk to low birth weight, white race, and male sex. Significant differences in the incidence of chronic lung disease were found between institutions even when birth weight, race, and sex were taken into consideration through a multivariate logistic regression analysis. Columbia had one of the best outcomes for low birth weight infants and the lowest incidence of chronic lung disease.
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