OBJECTIVES: To study variations in the way pediatricians would evaluate and manage an infant with an apparent life-threatening event. SUBJECTS AND METHODS: A survey was mailed to the chief residents of all pediatric residency training programs in the United States in which respondents were presented with a simulated case and asked how they would manage an infant who had experienced an apparent life-threatening event that did not require resuscitation. The survey also explored each physician's tolerance of uncertainty, knowledge of apparent life-threatening events, experience, fear of litigation, responsiveness to parental demands, and propensity to order tests. MAIN OUTCOME MEASURES: Presumed decisions to prescribe antibiotics and/or order home apnea monitoring in a simulated case of an infant who had experienced an apparent life-threatening event not requiring resuscitation. RESULTS: Logistic regression analysis revealed 2 characteristics that made significant and independent contributions to respondents' presumed decision to prescribe antibiotics: (1) experience with an adverse outcome, and (2) propensity to order diagnostic tests. Presumed decisions to order a home apnea monitor were notably affected by fear of litigation. CONCLUSIONS: These findings suggest that differences in pediatricians' characteristics contribute to variations in care. Efforts to make management more uniform must consider that decisions are influenced by a host of different characteristics and experiences.

Clinical Competence↗

PubMed1998

Pulmonary embolization causes hypoxemia by redistributing regional blood flow without changing ventilation.

To explore mechanisms of hypoxemia after acute pulmonary embolism, we measured regional pulmonary blood flow and alveolar ventilation before and after embolization with 780-micrometers beads in five anesthetized, mechanically ventilated pigs. Regional ventilation and perfusion were determined in approximately 2.0-cm3 lung volumes by using 1-micrometers-diameter aerosolized and 15-micrometers-diameter injected fluorescent microspheres. Hypoxemia after embolization resulted from increased perfusion to regions with low ventilation-to-perfusion ratios. Embolization caused an increase in perfusion heterogeneity and a fall in the correlation between ventilation and perfusion. Correlation between regional ventilation pre- and postembolization was greater than correlation between regional perfusion pre- and postembolization. The majority of regional ventilation-to-perfusion ratio heterogeneity was attributable to changes in regional perfusion. Regional perfusion redistribution without compensatory changes in regional ventilation is responsible for hypoxemia after pulmonary vascular embolization in pigs.

Animals↗

PubMed1998

Pulmonary gas-exchange analysis by using simultaneous deposition of aerosolized and injected microspheres.

Numerical methods for determining end-capillary gas contents for ventilation-to-perfusion ratios were first developed in the late 1960s. In the 1970s these methods were applied to validate distributions of ventilation-to-perfusion ratios measured by the multiple inert-gas-elimination technique. We combined numerical gas analysis and fluorescent-microsphere measurements of ventilation and perfusion to predict gas exchange at a resolution of approximately 2.0-cm3 lung volume in pigs. Oxygen, carbon dioxide, and inert gas exchange were calculated in 551-845 compartments/animal before and after pulmonary embolization with 780-micrometers beads. Whole lung gas exchange was estimated from the perfusion- and ventilation-weighted end-capillary gas contents. Before lung injury, no significant difference existed between microsphere-estimated arterial PO2 and PCO2 and measured values. After lung injury, the microsphere method predicted a decrease in arterial PO2 but consistently underestimated its magnitude. Correlation between predicted and measured inert gas retentions was 0.99. Overestimation of low-solubility inert gas retentions suggests underestimation of areas with low ventilation-to-perfusion ratios by microspheres after lung injury. Regional deposition of aerosolized and injected microspheres is a valid method for investigating regional gas exchange with high spatial resolution.

Aerosols↗

PubMed1998