Pulmonary clearance of Serratia marcescens in calves

The pulmonary clearance rate of Serratia marcescens was determined in 17 calves exposed to an aerosol from a modified Hendersen apparatus. The mean bovine pulmonary clearance was 50.2 +/- 4.1% at postaerosolization hour (PAH) 1, 72.5 +/- 7.0% at 2 hours, 88.6 +/- 5.2% at 4 hours, 97.3 +/- 2.8% at 8 hours, and 99.9% at PAH 24 and 48. Regional pulmonary mean percent retention (MPR) of S marcescens in 10 calves was determined in dorsal or ventral and in cranial or caudal regions. Dorsal MPR was less than ventral MPR for PAH 1, 2, and 4, whereas cranial MPR was greater than caudal MPR for PAH 1, 2, 4, and 8. Difference in regional airway oxygen tensions was suggested as the most probable reason for differing regional MPR values.