Aim Evaluate the effects of disconnecting the ventilator tubing during surfactant instillation on lung function, haemodynamic side effects and surfactant distribution over the lungs.

Subjects Lung lavaged rabbits with severe respiratory failure.

Intervention 99mTc labelled Alvofact was instilled during ventilation or after disconnection of the ventilator tubing. Assessed were PaO2, dynamic compliance, cerebral bloodflow and after sacrifice lung compliances and surfactant distribution

Results After instillation PaO2 rose from 8.7 ± 1.3(mean ± sem) to 24.9 ± 6.4kPa with disconnection and 8.4± 0.8 to 32.4 ± 4.3kPa without. Dynamic compliance rose from 0.40 ± 0.05 ml/cmH2O/kg to 0.51 ± 0.03 and from 0.46± 0.05 to 0.51 ± 0.03 resp. Static lung compliance were 0.92± 0.08 ml/cmH2O/kg and 1.05 ± 0.04 resp. Surfactant distribution was non-uniform, 20% and 21% of the lung pieces received ± 20% of the mean amount of surfactant. Cerebral bloodflow fell 64 ± 11% and 61 ± 13% resp. (All: no significant differences between groups)

Conclusion Disconnection does not influence the effect of surfactant instillation on lung function, cerebral blood flow and distribution of surfactant over the lungs.