Pulmonary blood flow distribution during partial liquid ventilation.

Regional pulmonary blood flow was investigated with radiolabeled microspheres in four supine lambs during the transition from conventional mechanical ventilation (CMV) to partial liquid ventilation (PLV) and with incremental dosing of perfluorocarbon liquid to a cumulative dose of 30 ml/kg. Four lambs supported with CMV served as controls. Formalin-fixed, air-dried lungs were sectioned according to a grid; activity was quantitated with a multichannel scintillation counter, corrected for weight, and normalized to mean flow. During CMV, flow in apical and hilar regions favored dependent lung (P < 0.001), with no gradient across transverse planes from apex to diaphragm. During PLV the gradient within transverse planes found during CMV reversed, most notably in the hilar region, favoring nondependent lung (P = 0.03). Also during PLV, flow was profoundly reduced near the diaphragm (P < 0.001), and across transverse planes from apex to diaphragm a dose-augmented flow gradient developed favoring apical lung (P < 0.01). We conclude that regional flow patterns during PLV partially reverse those noted during CMV and vary dramatically within the lung from apex to diaphragm.

Comparison of self-inflating bags with anesthesia bags for bag-mask ventilation in the pediatric emergency department.

OBJECTIVE: To compare bag-mask ventilation performed by emergency department (ED) personnel using anesthesia bags (AB) and self-inflating bags (SIB). SETTING: ED in a teaching children's hospital where the AB is the device used during resuscitations. DESIGN: Experimental study. Bag-mask ventilation was evaluated with an infant resuscitation mannequin equipped to measure airway volumes and pressures. Pediatric residents, ED nurses, and pediatric emergency medicine fellows performed bag-mask ventilation with AB and SIB and rated their confidence using each device. MAIN OUTCOME MEASURE: Ventilation failure rates. RESULTS: Seventy subjects participated (17 interns, 16 junior residents, 13 senior residents, 10 fellows, and 14 nurses). There were 13 failures with the AB (18.6%) versus 1 (1.4%) with the SIB (P < 0.01) [95% confidence interval: 5-29%], with a significant difference even after excluding the least experienced subjects. There was no difference in high pressure breaths delivered (SIB 19% vs AB 15%, P = 0.4) and a higher incidence of hyperventilation with the SIB (67 vs 25%, P < 0.01). While using the SIB, 19 (27%) of the subjects did not turn on the O2 flow. There was no difference in pretest confidence rating, but the posttest confidence rating was higher for the SIB (P < 0.05). CONCLUSIONS: Compared to SIB use for bag-mask ventilation in an ED, AB use resulted in more ventilation failures, no advantage in preventing excessive airway pressures, and less confidence among operators. The SIB should be the first choice for bag-mask ventilation in the ED, with attention to maximize oxygen delivery.