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Effect of single dose surfactant on pulmonary function
R Bhat1, K Dziedzic, V K Bhutani
1Department of Pediatrics, University of Illinois Medical Center, Chicago.
Insights
Exogenous surfactant therapy rapidly improved oxygenation and reduced airway resistance in preterm neonates with hyaline membrane disease. Lung compliance changes were delayed, suggesting other mechanisms contribute to initial benefits.
Area of Science:
- Neonatal Medicine
- Respiratory Physiology
- Pediatric Pulmonology
Background:
- Hyaline membrane disease (HMD) is a common respiratory distress in preterm infants.
- Exogenous surfactant administration is a standard treatment for HMD.
- Understanding the precise physiological effects of surfactant is crucial for optimizing neonatal care.
Purpose of the Study:
- To investigate the sequential changes in pulmonary mechanics following exogenous surfactant instillation in preterm neonates with HMD.
- To compare the effects of surfactant versus placebo on respiratory parameters over 96 hours.
Main Methods:
- A double-blind national study involving 15 preterm neonates (27-32 wk gestation, 0.88-1.55 kg birth weight).
- Pulmonary mechanics (dynamic compliance, resistance, work of breathing, tidal volume, minute ventilation) were measured before and at 2, 24, 60, and 96 hours post-instillation.
- Utilized pneumotachometry and esophageal balloon catheter for data acquisition.
Main Results:
- The surfactant group demonstrated immediate significant improvements in gas exchange ratio, mean airway pressure, and airway resistance (p < .05).
- Dynamic compliance (Cdyn) changes were observed at 24 hours post-surfactant.
- The control (placebo) group showed gradual improvement after initial deterioration.
Conclusions:
- Immediate oxygenation improvement post-surfactant is likely due to enhanced ventilation/perfusion matching and improved capillary stability, not solely compliance changes.
- Exogenous surfactant therapy provides rapid benefits in preterm neonates with HMD.
- Further research into the mechanisms of surfactant action is warranted.
Abstract:
Sequential changes in pulmonary mechanics in response to single dose exogenous surfactant instillation were studied in 15 preterm neonates who had hyaline membrane disease (HMD). The infants were part of a larger double-blind national study. Birth weight ranged from 0.88 to 1.55 kg, and gestational age was between 27 to 32 wk. There were six infants in the surfactant group and nine in the placebo group. Pulmonary mechanics were studied before and at 2, 24, 60, and 96 h after surfactant or sham instillation using a pneumotachometer and an esophageal balloon catheter. The variables studied were dynamic compliance (Cdyn), pulmonary resistance, work of breathing, tidal volume, and minute ventilation. Infants in the surfactant group showed an immediate and significant (p less than .05) improvement in gas exchange ratio, decreased mean airway pressure (9.7 +/- 0.9 to 7.9 +/- 0.4 cm H2O) and airway resistance (133 +/- 6.3 to 92 +/- 14.9 cm H2O/L.sec) (p less than .05). Changes in Cdyn were noted only at 24 h after surfactant instillation. In the control group, gradual improvement occurred after the initial deterioration. The findings suggest that the immediate improvement in oxygenation after surfactant instillation is the result of factors other than changes in lung compliance, such as improved ventilation/perfusion and better capillary stability with decreased leakage of fluid into alveoli.