Prolonged partial liquid ventilation in spontaneously breathing awake animals

Objective: To date, studies of partial liquid ventilation (PLV) have examin ed its effects acutely in anesthetized and mechanically ventilated subjects . We set out to develop a model of prolonged PLV in awake, spontaneously br eathing animals. Design: Animal case series Setting: Cardiopulmonary physiology laboratory. Subjects: Fifteen New Zealand white rabbits (3.2 +/- 0.39 kg). Interventions: Animals were anesthetized and instrumented with a novel tech nique allowing percutaneously assisted placement of an intratracheal cathet er with a subcutaneously tunneled externalized free end. After anesthetic r ecovery, PLV was performed in spontaneously breathing unsedated animals. Measurements and Main Results: Evaporative losses were determined using a s ingle 10 mL/kg perflubron dose (n = 5); hourly radiographs were obtained un til residual perflubron was minimal. For prolonged PLV (n = 10), a 10-mL/kg initial perflubron dose was followed every 4 hrs with 5-mL/kg supplements. Radiographs were obtained immediately before and after perflubron administ ration and were scored (0-5) by a radiologist blinded to dosing regimen and time interval. Data were analyzed with ANOVA and Student's t-test with cor rection for multiple comparisons. Initial filling was nearly complete (scor e = 4.8 +/- 0.42); lungs were maintained approximately half-filled through 4 hrs (score = 2.53 +/- 0.71). By 6 hrs, the majority of perflubron had eva porated (score = 1.75 +/- 0.53). Over 24 hrs, radiographs documented contin uous perflubron exposure (postfill = 4.53 +/- 0.64, prefill= 3.40 +/-. 0.71 , average = 3.97 +/- 0.43); scores were comparatively higher after filling (after = 4.53 +/- 0.64, before = 3.4 +/- 0.71, p < .001). Left and right lu ng volumes were equivalent (left = 4.06 +/- 0.47, right = 3.89 +/- 0.39, p = .027). All animals survived the 24 hrs of PLV. Conclusions: Percutaneously assisted intratracheal cannulation with cathete r exteriorization permits prolonged PLV in spontaneously breathing, unsedat ed animals. Continuous perfluorocarbon exposure with this method is reprodu cible, consistent, and well tolerated for 24 hrs in uninjured animals.