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PubMed2000

The effect of perfluorocarbon vapour on the measurement of respiratory tidal volume during partial liquid ventilation.

During partial liquid ventilation perfluorocarbon vapour is present in the exhaled gases. The volumes of these gases are measured by pneumotachometers. Error in measuring tidal volumes will give erroneous measurement of lung compliance during partial liquid ventilation. We aim to compare measured tidal volumes with and without perfluorocarbon vapour using tidal volumes suitable for use in neonates. Tidal volumes were produced with a 100 ml calibration syringe from 20 to 100 ml and with a calibrated Harvard rodent ventilator from 2.5 to 20 ml. Control tidal volumes were drawn from a humidifier chamber containing water vapour and the PFC tidal volumes were drawn from a humidifier chamber containing water and perfluorocarbon (FC-77) vapour. Tidal volumes were measured by a fixed orifice, target, differential pressure flowmeter (VenTrak) or a hot-wire anenometer (Bear Cub) placed between the calibration syringe or ventilator and the humidifier chamber. All tidal volumes measured with perfluorocarbon vapour were increased compared with control (ANOVA p < 0.001 and post t-test p < 0.0001). Measured tidal volume increased from 7 to 16% with the fixed orifice type flow-meter, and from 35 to 41% with the hot-wire type. In conclusion, perfluorocarbon vapour flowing through pneumotachometers gives falsely high tidal volume measurements. Calculation of lung compliance must take into account the effect of perfluorocarbon vapour on the measurement of tidal volume.

Animals↗
PubMed2000

Gravitational effects on volume distribution in a model of partial and total liquid ventilation.

To estimate regional lung volume during ventilation with liquids (e. g. perfluorochemicals, PFC) we developed a multi-compartment mathematical model of a lung and thorax. The height of the fluid column and the fluid's density determine alveolar pressure (PA). The weight of thoracic contents above any given gravitational plane influences pleural pressure (PPL). Transpulmonary pressure (PTP=PA&MINUS;PPL) and compliance of the lung and chest wall permit estimation of volumes. The results indicate the lung inflates almost uniformly during total liquid ventilation despite a substantial vertical PA gradient. Inflation uniformity is due to the offsetting vertical PPL gradient created by the added weight of the PFC and sustained by the relative rigidity of the chest wall. During partial liquid ventilation our model indicates that the combination of uniform PA with a large vertical gradient in PPL leads to a vertical PTP gradient and therefore relative over-inflation of the top of the lung. This effect increases with increasing PFC dose and with lung height.

Functional Residual Capacity↗
PubMed2001

Prevention of ventilator-induced lung injury with partial liquid ventilation.

BACKGROUND/PURPOSE: Pulmonary injury from mechanical ventilation has been attributed to application of excess alveolar pressure (barotrauma) or volume (volutrauma). The authors questioned whether partial liquid ventilation (gas ventilation of the perfluorocarbon filled lung, PLV) would reduce ventilator-induced lung injury. METHODS: A tracheostomy tube and carotid artery catheter were placed in anesthetized Sprague-Dawley rats (500 +/- 50 g). Bovine serum albumin (BSA) labeled with Iodine (I) 125 was administered intraarterially. Ventilation with tidal volume (TV) of 5 mL/kg was initiated. The rats were then selected randomly to a 30-minute experimental period of one of the following ventilation protocols: continued atraumatic gas ventilation (GV, TV, 5 mL/kg; n = 10); atraumatic gas ventilation combined with intratracheal administration of 10 mL/kg perfluorocarbon (GV-PLV, TV, 5 mL/kg, n = 10); barotrauma (BT, peak inspiratory pressure [PIP], 45 cm H(2)O; n = 10); barotrauma with PLV (BT-PLV, PIP, 45 cm H(2)O; n = 8); volutrauma (VT, TV, 30 mL/kg; n = 8); or volutrauma with PLV (VT-PLV, TV, 30 mL/kg; n = 10). Animals were killed and the amount of radiolabeled BSA in both lungs was measured and normalized to the counts in 1 mL of blood from that animal (injury index). Data were analyzed by analysis of variance (ANOVA) with post-hoc t test comparison between groups. RESULTS: There was a significant difference in the (125)I-BSA injury index when all groups were compared (P <.001 by ANOVA). Post-hoc analysis showed a significant decrease in the injury index when comparing BT versus BT-PLV (P =.024) and VT versus VT-PLV (P =.014). CONCLUSION: (125)I-BSA leak produced during high-pressure or high-volume mechanical ventilation is reduced by partial liquid ventilation.

Analysis of Variance↗
PubMed1999

Liquid ventilation attenuates pulmonary oxidative damage.

PURPOSE: Liquid perfluorochemicals reduce the production of reaction oxygen species by alveolar macrophages. We sought to determine whether the use of liquid perfluorochemicals in vivo during liquid ventilation would attenuate oxidative damage to the lung. MATERIALS AND METHODS: Healthy infant piglets (n = 16) were instrumented for mechanical ventilation and received intravenous oleic acid to create an acute lung injury. The animals were assigned to a nontreatment group receiving conventional mechanical ventilation or a treatment group receiving partial liquid ventilation with a liquid perfluorochemical. Following sacrifice, the bronchoalveolar lavage and lung parenchyma were analyzed for evidence of oxidative damage to lipids and proteins by determination of TBARS and carbonylated protein residues, respectively. RESULTS: Mortality in the control group was 50% at the completion of the study compared with no deaths in the partial liquid ventilation group (P = .025). The alveolar-arterial oxygen difference was more favorable following injury in the partial liquid ventilation group. The liquid ventilation group demonstrated a 32% reduction in TBARS (P = .043) and a 14% reduction in carbonylated protein residues (P = .061). CONCLUSION: These data suggest that partial liquid ventilation supports gas exchange and reduces mortality in association with a reduction in the production of reactive oxygen species and the concomitant attenuation of tissue damage during the early phase of acute lung injury.

Animals↗
PubMed1998

Changes in pulmonary vascular resistance in response to partial liquid ventilation.

BACKGROUND/PURPOSE: Partial liquid ventilation (PLV) with perfluorocarbons decreases pulmonary vascular resistance (PVR) in injured piglet lungs without supplemental oxygen. These PVR changes may result either from direct mechanical effects or improved arterial oxygenation. In an uninjured hypoxic model of elevated PVR the authors asked the following questions: (1) Does prophylactic or therapeutic PLV ameliorate the PVR response to hypoxia? (2) Do prophylactic and therapeutic PLV have different PVR effects? (3) Does supplemental oxygen modify PVR response to PLV? METHODS: Piglet (3 to 4 kg) lungs were isolated in situ without ischemia, hypoxia, or reperfusion injury. Pulmonary artery (PA) and left atrial (LA) cannulae were attached to a blood-primed extracorporeal membrane oxygenation (ECMO) perfusion circuit with a flow (QPA) of 80 mL/kg/min. Pressure-limited, volume-cycled ventilation (PIP < 25 mm Hg, Tv = 15 mL/kg) was initiated. PLV with perfluorodecalin (15 mL/kg) was administered endotracheally. Continuously monitored blood gas parameters allowed airway and extracorporeal adjustment of FiO2 to produce a PO2 appropriate to the experimental phase. PVR was calculated as (PPA - PLA/QPA). After a stable 30-minute normoxic baseline, animals were assigned randomly to three groups. In group I, control (n = 7), PVR was measured for 150 minutes in hypoxic lungs (FiO2 = 0.07, PPAO2 = 40 mm Hg, SPAO2 = 70%). In group II, prophylactic (n = 8), PLV was administered, followed by 90 minutes of hypoxia, and 60 minutes of oxygen recovery (FiO2 = 0.21-0.30, PPAO2 > 100 mm Hg, SPAO2 = 100%). In group III, therapeutic (n = 8), after 30 hypoxic minutes, PLV was administered and maintained for 90 minutes, followed by a 60-minute oxygen recovery phase. Results were expressed as mean +/- SEM. Statistical analysis of groups was performed by repeated measures of analysis of variance (ANOVA) and Tukey correction. RESULTS: In group I normoxic gas-ventilated PVR was 174+/-12 mm Hg/L/kg/min. After 90 hypoxic minutes PVR was 318+/-37 (P < .01 vbaseline). In group II baseline PVR was 183+/-14. PVR after 30 normoxic minutes of PLV was 199+/-14 (P = ns v baseline). After 90 hypoxic minutes, PVR was 350+/-31 (P < .01 v baseline, and PLV alone) followed by a decrease to 192+/-19 after 60 minutes of oxygen recovery (P = ns v baseline or PLV alone). In group III baseline PVR was 160+/-17 and 325+/-29 after 30 hypoxic minutes. After 90 hypoxic minutes of PLV, PVR was 366+/-22 (P = ns v hypoxia control, P < .01 v normoxic baseline). PVR recovered to 189+/-19 after 60 minutes of oxygen recovery (P = ns v baseline). CONCLUSIONS: Prophylactic/therapeutic PLV had no effect on hypoxia-induced increases in PVR and did not differ from each other. Although PLV alone decreases PVR in the injured lung without supplemental oxygen, elevated PVR associated with hypoxia was ameliorated only by supplemental oxygen in the liquid ventilated lung.

Animals↗
PubMed1976

Liquid ventilation of primates.

Three adult monkeys were anesthetized with ketamine and ventilated with fluorocarbon liquid [perfluoro bis (1, 4-isopropoxy) butane (Caroxin-D)] at 1 atmosphere on two separate occasions. During five runs, liquid ventilation was continued for 60 minutes. The sixth run was continued for ten minutes. Arterial blood gas levels during and after liquid ventilation were adequate for survival. Three years after the first period of liquid ventilation, the animals were killed. Approximately 0.001 mg of fluorocarbon per gram of tissue was present in the kidney, liver, brain, spleen, muscle, and heart. Fat contained approximately seven to nine times this amount, and the lung and pulmonary lymph nodes contained approximately 1,000 times this amount. In no case was it clinically evident that the monkeys had undergone periods of liquid ventilation. We conclude that primates can be ventilated successfully with liquid fluorocarbon on at least two separate occasions and can return to breathing air without obvious deleterious effects, but fluorocarbon is retained in small amounts for at least three years.

Adipose Tissue↗
PubMed2002

Cerebral oxygenation is affected by filling mode and perfluorochemical volume in partial liquid ventilation of healthy piglets.

Intrapulmonary administration of perfluorochemicals (PFC) has been suggested for reasons other than respiratory insufficiency. PFC application has been described to affect cerebral Hb concentration, however, data for healthy lungs are missing. Newborn piglets were randomized into 3 groups (30-ml slow-filling, 10-ml slow-filling and 30-ml rapid-filling), orally intubated and mechanically ventilated. Partial liquid ventilation (PLV) was initiated by filling the lung with PF5080 (10 or 30 ml/kg) at a rate of 1.5 ml/min (slow filling) or within 45 s (rapid filling). Vital signs, blood gases, tidal volume (VT) and changes in the cerebral concentration of oxygenated hemoglobin (HbO(2)) and total Hb were determined for up to 20 min. Rapid administration of PFC caused an immediate drop in HbO(2), PaO(2) and VT. The concentration of oxygenated and total Hb increased thereafter and remained high. We found a slow increase in PaCO(2), HbO(2) and total Hb in the 30-ml slow-filling group, but almost no changes in the 10-ml slow filling group (except for a decrease in PaO(2)). According to our data, PLV with 10 ml/kg should be preferred since cerebral alterations are minimal. If complete filling of the lung is needed PFC should be administered slowly to minimize side effects.

Animals↗
PubMed1997

Shunt and ventilation-perfusion distribution during partial liquid ventilation in healthy piglets.

Replacing gas in the lung with perfluorocarbon fluids (PFC) and periodically ventilating with a gas [partial liquid ventilation (PLV)] has been shown to improve oxygenation in models of respiratory distress syndrome. We hypothesized that the addition of PFC to healthy lungs would result in shunt, diffusion impairment, and increased ventilation-perfusion (VA/Q) heterogeneity. Previously, Mates et al. showed that O2 shunt and arterial-alveolar CO2 difference increased linearly with dose in piglets given graded intratracheal doses of PFC (10, 20, and 30 ml/kg followed by mechanical ventilation with 100% O2) (E.A. Mates, J. C. Jackson, J. Hildebrandt, W. E. Truog, T. A. Standaert, and M. P. Hlastala. In: Oxygen Transport to Tissue XVI, 1994, p. 427-435). Here we report VA/Q distribution in the same animals, showing a 50% increase in VA/Q heterogeneity during PLV independent of PFC dose. Ventilation heterogeneity was the major factor in this increase, and there was no significant change in dead space ventilation. We also report on five animals given a single 20 ml/kg dose of PFC and followed for 3 h. They showed an increase in shunt during PLV but no change in arterial-alveolar CO2 difference.

Animals↗
PubMed1981

Increased pulmonary vascular resistance during liquid ventilation.

The effect of liquid ventilation on pulmonary vascular resistance was studied in an isolated cat lung preparation in situ. Lungs were perfused with whole blood from a donor cat at a constant flow of 100 ml . min-1 kg-1. Pulmonary arterial venous pressures were measured, and pulmonary vascular resistance calculated during gas ventilation (control) and ventilation with fluorocarbon, FC-80. During control ventilation at a mean tidal volume (VT) of 28 +/- 1 (SEM) ml and lung volume of 108 +/- 8 (SEM) ml, pulmonary vascular resistance was 0.07 +/- 0.01 (SEM) PRU. During liquid ventilation at similar lung volumes, pulmonary vascular resistance increased by 62% to 0.12 +/- 0.03 (SEM) PRU (P less than 0.05). At greater liquid lung volumes reflecting optimum CO2 elimination, pulmonary vascular resistance increased by 115% over control values to 0.15 +/- 0.01 (SEM) PRU (P less than 0.005). These data demonstrate significant alterations in pulmonary circulation during liquid ventilation, and suggest that further studies should be completed before hyperbaric applications in human can be considered.

Animals↗
PubMed2005

A mathematical model of alveolar gas exchange in partial liquid ventilation.

In partial liquid ventilation (PLV), perfluorocarbon (PFC) acts as a diffusion barrier to gas transport in the alveolar space since the diffusivities of oxygen and carbon dioxide in this medium are four orders of magnitude lower than in air. Therefore convection in the PFC layer resulting from the oscillatory motions of the alveolar sac during ventilation can significantly affect gas transport. For example, a typical value of the Péclet number in air ventilation is Pe approximately 0.01, whereas in PLV it is Pe approximately 20. To study the importance of convection, a single terminal alveolar sac is modeled as an oscillating spherical shell with gas, PFC, tissue and capillary blood compartments. Differential equations describing mass conservation within each compartment are derived and solved to obtain time periodic partial pressures. Significant partial pressure gradients in the PFC layer and partial pressure differences between the capillary and gas compartments (P(C)-Pg) are found to exist. Because Pe>> 1, temporal phase differences are found to exist between P(C)-Pg and the ventilatory cycle that cannot be adequately described by existing non-convective models of gas exchange in PLV The mass transfer rate is nearly constant throughout the breath when Pe>>1, but when Pe<<1 nearly 100% of the transport occurs during inspiration. A range of respiratory rates (RR), including those relevant to high frequency oscillation (HFO) +PLV, tidal volumes (V(T)) and perfusion rates are studied to determine the effect of heterogeneous distributions of ventilation and perfusion on gas exchange. The largest changes in P(C)O2 and P(C)CO2 occur at normal and low perfusion rates respectively as RR and V(T) are varied. At a given ventilation rate, a low RR-high V(T) combination results in higher P(C)O2, lower P(C)CO2 and lower (P(C)-Pg) than a high RR-low V(T) one.

Adult↗
PubMed2001

A model of neonatal tidal liquid ventilation mechanics.

Tidal liquid ventilation (TLV) with perfluorocarbons (PFC) has been proposed to treat surfactant-deficient lungs of preterm neonates, since it may prevent pulmonary instability by abating saccular surface tension. With a previous model describing gas exchange, we showed that ventilator settings are crucial for CO(2) scavenging during neonatal TLV. The present work is focused on some mechanical aspects of neonatal TLV that were hardly studied, i.e. the distribution of mechanical loads in the lungs, which is expected to differ substantially from gas ventilation. A new computational model is presented, describing pulmonary PFC hydrodynamics, where viscous losses, kinetic energy changes and lung compliance are accounted for. The model was implemented in a software package (LVMech) aimed at calculating pressures (and approximately estimate shear stresses) within the bronchial tree at different ventilator regimes. Simulations were run taking the previous model's outcomes into account. Results show that the pressure decrease due to high saccular compliance may compensate for the increased pressure drops due to PFC viscosity, and keep airway pressure low. Saccules are exposed to pressures remarkably different from those at the airway opening; during expiration negative pressures, which may cause airway collapse, are moderate and appear in the upper airways only. Delivering the fluid with a slightly smoothed square flow wave is convenient with respect to a sine wave. The use of LVMech allows to familiarize with LV treatment management taking the lungs' mechanical load into account, consistently with a proper respiratory support.

Carbon Dioxide↗
PubMed1999

Comparison of exogenous surfactant therapy, mechanical ventilation with high end-expiratory pressure and partial liquid ventilation in a model of acute lung injury.

We have compared three treatment strategies, that aim to prevent repetitive alveolar collapse, for their effect on gas exchange, lung mechanics, lung injury, protein transfer into the alveoli and surfactant system, in a model of acute lung injury. In adult rats, the lungs were ventilated mechanically with 100% oxygen and a PEEP of 6 cm H2O, and acute lung injury was induced by repeated lung lavage to obtain a PaO2 value < 13 kPa. Animals were then allocated randomly (n = 12 in each group) to receive exogenous surfactant therapy, ventilation with high PEEP (18 cm H2O), partial liquid ventilation or ventilation with low PEEP (8 cm H2O) (ventilated controls). Blood-gas values were measured hourly. At the end of the 4-h study, in six animals per group, pressure-volume curves were constructed and bronchoalveolar lavage (BAL) was performed, whereas in the remaining animals lung injury was assessed. In the ventilated control group, arterial oxygenation did not improve and protein concentration of BAL and conversion of active to non-active surfactant components increased significantly. In the three treatment groups, PaO2 increased rapidly to > 50 kPa and remained stable over the next 4 h. The protein concentration of BAL fluid increased significantly only in the partial liquid ventilation group. Conversion of active to non-active surfactant components increased significantly in the partial liquid ventilation group and in the group ventilated with high PEEP. In the surfactant group and partial liquid ventilation groups, less lung injury was found compared with the ventilated control group and the group ventilated with high PEEP. We conclude that although all three strategies improved PaO2 to > 50 kPa, the impact on protein transfer into the alveoli, surfactant system and lung injury differed markedly.

Animals↗
PubMedDate not supplied

Recent innovations in total liquid ventilation system and component design.

In addition to partial liquid ventilation (PLV), total liquid ventilation (TLV) is being explored as a potential therapy to mitigate ventilator-associated lung injury and acute lung failure. TLV is ventilation of the completely liquid-filled lung using tidal flow of oxygenated perfluorochemical (PFC) liquid delivered by a "liquid ventilator." Most TLV research to date has focused on "small" lung (animals < 20 kg; vast majority < 5 kg), with primary relevance to its use in children. Recent investigations regarding TLV in larger lungs have helped define new design challenges for liquid ventilator systems to succeed as clinical products. Adult TLV requires the delivery of significantly higher liquid tidal volumes, with proportionately greater O2 and CO2 exchange. Although a simple scale-up of liquid ventilator components such as pumps, tubing, fittings, and gas and heat exchangers might be considered the most straightforward way to compensate for the increased demand, there are a number of practical problems with this approach. These include requirements to: 1) minimize priming volume, 2) minimize PFC evaporative loss, 3) suppress flow-induced cavitation in fittings and components, 4) monitor and control ventilation based on pressure signals exhibiting noise, 5) maintain ability and accuracy of delivered breaths in a fluid mechanical environment having higher inertial forces and pressure losses than for small lung systems, 6) use disposable or sterilizable fluid-contacting components, and 7) maintain PFC materials compatibility. TLV system and component innovations implemented on a new large-animal liquid ventilator prototype are presented. The advantages of new pumps, gas exchangers, and temperature-control components are discussed.

Adult↗
PubMed1994

Liquid ventilation: it's not science fiction anymore.

Liquid ventilation is, by all initial considerations, an unconventional concept. Decades of research, however, have found that by using perfluorocarbons, which are capable of holding high concentrations of critical gases such as oxygen and carbon dioxide, gas exchange optimal enough to support life is possible with no known toxic effects. The earliest method of liquid ventilation, tidal liquid breathing, involved infusion and active removal of tidal volumes of perfluorocarbons by a liquid ventilator for gas exchange. Recently, a new method of partial liquid breathing, called perfluorocarbon-associated gas exchange, makes the process of liquid ventilation simpler by using conventional gas ventilators. Current research is showing great promise in the use of liquid ventilation for patients with pulmonary pathology. Critical care nurses should become knowledgeable of this new mode of ventilation and be prepared to meet the special needs of this unique population.

Critical Care↗
PubMed1996

Evaluation of gas exchange, pulmonary compliance, and lung injury during total and partial liquid ventilation in the acute respiratory distress syndrome.

OBJECTIVE: To investigate whether pulmonary compliance and gas exchange will be sustained during "total" perfluorocarbon liquid ventilation followed by "partial" perfluorocarbon liquid ventilation when compared with gas ventilation in the setting of the acute respiratory distress syndrome (ARDS). STUDY DESIGN: A prospective, controlled, laboratory study. SETTING: A university research laboratory. SUBJECTS: Ten sheep, weighing 12.7 to 25.0 kg. INTERVENTIONS: Lung injury was induced in ten young sheep, utilizing a right atrial injection of 0.07 mL/kg of oleic acid followed by saline pulmonary lavage. Bijugular venovenous extracorporeal life support access, a pulmonary artery catheter, and a carotid artery catheter were placed. When the alveolar-arterial O2 gradient was >/= 600 torr and PaO2 </= 50 torr (</= 6.7 kPa) with an FIO2 of 1.0, extracorporeal life support was instituted. For the first 30 mins on extracorporeal life support, all animals were ventilated with gas. Animals were then ventilated with equal tidal volumes of 15 mL/kg during gas ventilation (n=5) over the ensuing 2.5 hrs, or with total liquid ventilation for 1 hr, followed by partial liquid ventilation for 1.5 hrs (total/partial liquid ventilation, n=5). MEASUREMENTS AND MAIN RESULTS: An increase in physiologic shunt (gas ventilation = 69 +/- 11%, total/partial liquid ventilation = 71 +/- 3%) and a decrease in static total pulmonary compliance measured at 20 mL/kg inflation volume (gas ventilation = O.48 +/- 0.03 mL/cm H2O/kg, total/partial liquid ventilation = 0.50 +/- 0.17 mL/cm H2O/kg) were observed in both groups with induction of lung injury. Physiologic shunt was significantly reduced during total and partial liquid ventilation when compared with physiologic shunt observed in the gas ventilation animals (gas ventilation = 93 +/- 8%, total liquid ventilation = 45 +/- 11%, p<.001; gas ventilation = 95 +/- 3%, partial liquid ventilation = 61 +/- 12%, p<.001), while static compliance was significantly increased in the total, but not the partial liquid ventilated animals when compared with the gas ventilated group (gas ventilation = 0.43 +/- 0.03 mL/cm H2O/kg, total liquid ventilation = 1.13 +/- 18 mL/cm H2O/kg, p <.001; gas ventilation = 0.41 +/- 0.02 mL/cm H2O/kg, partial liquid ventilation = 0.47 +/- 0.08, p = .151). In addition, the extracorporeal life support flow rate required to maintain adequate oxygenation was significantly lower in the total/partial liquid ventilation group when compared with that of the gas ventilation group (gas ventilation = 89 +/- 7 mL/kg/min, total liquid ventilation = 22 +/- 10 mL/kg/min, p <.001; gas ventilation = 91 +/- 12 mL/kg/min, partial liquid ventilation = 41 +/- 11 mL/kg/min, p < .001). Lung biopsy light microscopy demonstrated a marked reduction in alveolar hemorrhage, lung fluid accumulation, and inflammatory infiltration in the total/partial liquid ventilation animals when compared with the gas ventilation animals. CONCLUSIONS: In a model of severe ARDS, pulmonary gas exchange is improved during total followed by partial liquid ventilation. Pulmonary compliance is improved during total, but not during partial liquid ventilation. Total followed by partial liquid ventilation was associated with a reduction in alveolar hemorrhage, pulmonary edema, and lung inflammatory infiltration.

Animals↗
PubMed2000

Effect of perfluorochemical liquid ventilation on cardiac output and blood pressure variability in neonatal piglets with respiratory insufficiency.

Respiration and mechanical ventilation induce cyclic variation in cardiac output and blood pressure. We examined these phasic hemodynamic influences of mechanical ventilation during gas ventilation and partial and tidal liquid ventilation in 7 anesthetized and paralyzed young piglets (body weight, 3.0-4.9 kg) made respiratory-insufficient by repeated saline lung lavage. Nonlinear regression analysis of cardiovascular parameters vs. time was done to quantify respiratory-induced fluctuations in hemodynamic variables. The amplitude of oscillations was expressed as a percentage of the mean hemodynamic variable during the study period, and was called the relative oscillation amplitude. The relative oscillation amplitude of left ventricular stroke volume, left ventricular output, systemic arterial pressure, and systemic perfusion pressure was significantly larger (at least twofold) during tidal liquid ventilation compared to partial liquid ventilation. No such differences were observed between gas and partial liquid ventilation at comparable gas ventilator settings. We conclude that in this animal model, within-breath modulation of left ventricular output, systemic blood pressure, and perfusion pressure was significantly increased during tidal liquid ventilation as compared to partial liquid ventilation.

Animals↗
PubMed1998

High-frequency partial liquid ventilation in respiratory distress syndrome: hemodynamics and gas exchange.

Partial liquid ventilation using conventional ventilatory schemes improves lung function in animal models of respiratory failure. We examined the feasibility of high-frequency partial liquid ventilation in the preterm lamb with respiratory distress syndrome and evaluated its effect on pulmonary and systemic hemodynamics. Seventeen lambs were studied in three groups: high-frequency gas ventilation (Gas group), high-frequency partial liquid ventilation (Liquid group), and high-frequency partial liquid ventilation with hypoxia-hypercarbia (Liquid-Hypoxia group). High-frequency partial liquid ventilation increased oxygenation compared with high-frequency gas ventilation over 5 h (arterial oxygen tension 253 +/- 21.3 vs. 17 +/- 1.8 Torr; P < 0.001). Pulmonary vascular resistance decreased 78% (P < 0.001), pulmonary blood flow increased fivefold (P < 0.001), and aortic pressure was maintained (P < 0.01) in the Liquid group, in contrast to progressive hypoxemia, hypercarbia, and shock in the Gas group. Central venous pressure did not change. The Liquid-Hypoxia group was similar to the Gas group. We conclude that high-frequency partial liquid ventilation improves gas exchange and stabilizes pulmonary and systemic hemodynamics compared with high-frequency gas ventilation. The stabilization appears to be due in large part to improvement in gas exchange.

Animals↗
PubMed1998

Acute respiratory distress syndrome. Liquid ventilation.

In summary, the use of partial liquid ventilation with perfluorocarbon seems to be safe in neonates, children, and adults with ALI or ARDS. Partial liquid ventilation can be used for the following goals: recruitment of lung volume; enhancement or uniformity of lung inflation; improved oxygenation; improved lung compliance; and prevention or minimization of lung damage induced by mechanical ventilation. Partial liquid ventilation improved gas exchange and lung mechanics in test subjects. Cardiopulmonary interaction and long-term safety require further study. Extrapolations from animal data, however, suggest that there are no long-term undesired effects. The current clinical data strongly suggest that close monitoring and adjustment of ventilator parameters during drug instillation are necessary to reduce hypoxia, bradycardia, and pneumothorax. Further studies are required to explore the efficacy of partial liquid ventilation with perfluorocarbon in ALI or ARDS subjects, in particular, to evaluate the safety and efficacy of smaller doses; mechanical ventilation strategies; and outcomes. Additional research including large randomized studies is clearly required to answer these and other questions.

Animals↗