Partial liquid ventilation: effects of liquid volume and ventilatory settings on perfluorocarbon evaporation

Abstract

During partial liquid ventilation perfluorocarbons are eliminated mainly by evaporation via the airways. The effects of intrapulmonary perfluorocarbon volume, respiratory rate, tidal volume, as well as the level of end-expiratory pressure on perfluorocarbon elimination from isolated lungs, were studied.Nonperfused rabbit lungs underwent partial liquid ventilation (2-15 mL?kg -1 perfluorocarbon) with variable levels of end-expiratory pressure (0-10 cmH 2 O), respiratory rates (15-60 breaths?min -1 ) and tidal volumes (3.3-10.0 mL?kg -1 ). Evaporative loss of perfluorocarbon was determined gravimetrically as rate of change in lung weight.At constant respiratory settings, intrapulmonary liquid volume determined evaporative loss in a nonlinear fashion. Mean evaporation at a liquid volume of 5 mL?kg -1 was 13% lower compared to evaporation at a liquid volume of 15 mL?kg -1 . Any increase in end-expiratory pressure reduced perfluorocarbon evaporation, e.g. by y50% when end-expiratory pressure was increased from 0 to 10 cmH 2 O. At constant endexpiratory pressure and perfluorocarbon filling evaporation increased in a linear fashion with increasing respiratory rate and tidal volume.In summary, the experiments suggested that evaporative loss of perfluorocarbons during partial liquid ventilation of isolated lungs is increased with increasing intrapulmonary liquid volume, respiratory rate and tidal volume and is reduced in a level-dependent fashion by the application of positive end-expiratory pressure. During partial liquid ventilation perfluorocarbons are instilled into the airways from where they are subsequently eliminated by evaporation via the bronchial system. This process is influenced by various factors, like the physicochemical properties of the liquids (especially vapour pressure), the dose instilled into the airways, intrapulmonary perfluorocarbon distribution and respiratory settings [1][2][3][4][5][6]. Only small amounts cross the alveolo-capillary membranes into the vascular space and are stored in intra-and extrathoracic lymph nodes as well as in other organs indicating systemic distribution [7][8][9].A major variable which appears to influence perfluorocarbon elimination is the amount of liquid within the lungs. It has been observed before that perfluorocarbon evaporation is not a constant process, but decreases over time [3]. Elimination also depends on the ventilatory settings, especially respiratory rate and tidal volume. In addition, the level of end-expiratory pressure may affect elimination since superimposing a positive end-expiratory pressure (PEEP) during partial liquid ventilation may increase functional residual capacity and alveolar ventilation [10][11][12][13][14][15][16]. Such effects are likely to influence intrapulmonary perfluorocarbon distribution as well as the air/liquid interface from which perfluorocarbons evaporate in the expired gas during partial liquid ventilation.It is difficult to control and vary these variables independently from each other during in vivo measurement...

Partial liquid ventilation: effects of positive end-expiratory pressure on perfluorocarbon evaporation from the lungs of anesthetized dogs

“…This finding is consistent with previous observations in which evaporation decreased over time during in vivo measurements [1,2,3] and in isolated rabbit lungs [4]. In the latter we observed that 10 ml/kg perfluorocarbon (PF-5080) is eliminated after 7 h. In contrast to our findings in dogs, we observed that PEEP reduces evaporative loss from isolated lungs [4]. It is possible that in isolated lungs PEEP redistributes more perfluorocarbon to dependent lung regions and ventilation to nondependent regions (which contain less liquid) than during the closed-chest condition, resulting in less evaporation from isolated lungs with increasing levels of end-expiratory pressure.…”

“…This finding is consistent with previous observations in which evaporation decreased over time during in vivo measurements [1,2,3] and in isolated rabbit lungs [4]. In the latter we observed that 10 ml/kg perfluorocarbon (PF-5080) is eliminated after 7 h. In contrast to our findings in dogs, we observed that PEEP reduces evaporative loss from isolated lungs [4].…”

“…This process is conditioned by various factors, including the physicochemical properties of the liquids (especially vapor pressure), dose instilled into the airways, intrapulmonary perfluorocarbon distribution, and minute ventilation [1,2,3,4]. Only small amounts cross the alveolocapillary membranes into the circulation and are stored in intra-and extrathoracic lymph nodes and other organs, indicating systemic distribution [5,6].…”

Partial liquid ventilation in acute salt water-induced lung injury

“…While one group received a single instillation another group received an additional continuous instillation until the end of the experiment. In previous studies, when using this particular perfluorocarbon (PF 5080; 3M, Neuss, Germany), we observed an elimination half time of a few hours [9,10]. Therefore, most of the liquid must have been eliminated from the lungs within the study period in the group with a single instillation.…”