PURPOSE: Bronchoalveolar lavage (BAL) in ventilated neonates is a modification of routine endotracheal suction and is a potentially useful technique in studying the evolution and resolution of pulmonary inflammation. Therefore, this study is designed to investigate the effects of BAL on blood gases, blood pressure and heart rate in ventilated newborn infants with respiratory disease. METHODS: Fourteen premature infants were lavaged and all were intubated for respiratory distress syndrome and ventilated by a pressure-limited ventilator. Heart rate and mean arterial blood pressure were recorded during a 3 minute pre-lavage period and then for 5 minutes after the procedure. Arterial blood gases were obtained from an indwelling arterial catheter immediately before and 1 minute after BAL. RESULTS: Clinically significant hypoxemia (<30mmHg) was not induced in any infant and decreases in PaO2 were not statistically significant. Increases in PaCO2 and decreases in pH were statistically significant (P<0.01, P<0.05), but they were not clinically important. And the ranges of PaCO2 and pH after the procedure were from 26.6 to 55.1mmHg and from 7.18 to 7.46, respectively. Clinically important tachycardia (>200/min) or bradycardia (<110/min) were not induced in any infant. Heart rate and mean arterial blood pressure tended to increase at 1 minute post- BAL and those recovered completely within 5 minutes post-BAL. Readings of transcutaneous oxygen obtained from the 14 infants showed to be recovered completely within 4 minutes post- BAL. CONCLUSION: These changes appear to be qualitatively and quantitatively similar to those described after routine endotracheal suction.