Dose monitoring in Partial Liquid Ventilation by infrared measurement of expired perfluorochemicals

Patients undergoing Partial Liquid Ventilation (PLV) with the perfluorochemical liquid perflubron (PFB) continuously evaporate the drug from the lung during ventilatory expiration. In this study, two infrared (IR) devices, a modified industrial analyzer ("experimental prototype") and a custom-designed device suitable for use in a clinical environment ("clinical prototype"), were calibrated and validated on the bench to measure a range of PFB concentrations (CPFB) in a gas stream. PFB loss from the lung (area under the CPFB-vs-time-curve) could be correlated during PLV simulation with changes in tidal volume, breathing rate, and variable CPFB-vs-time profiles. The two IR devices produced nearly identical measurements for the same CPFB standards (maximum deviation = 1.5%). The experimental IR prototype was tested in 17 anesthetized, paralyzed, and ventilated swine (42-53 kg) to quantify the total amount and rate of evaporate loss of PFB over 12 hours of PLV, both with and without periodic supplemental PFB doses. The residual PFB volumes in the animal lungs at the end of the study, as determined by a gravimetric postmortem lung method, were found to agree on average for all animals to within 10% of the residual PFB volume as predicted by the IR approach. Furthermore, the IR signal of CPFB does not appear to correlate with the absolute amount of PFB in the lungs, but may reflect the relative proportion of PFB-wetted airway and alveolar surface. The authors conclude that IR quantitation of PFB evaporative loss is acceptably accurate for extended periods of PLV and may be a useful tool in the clinic for PFB dose monitoring and maintenance, thereby helping to optimize PLV treatment.

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.

Integrating management concepts into licensed practical nurse and associate degree in nursing student clinical experiences

In an associate degree nursing program in which students have the option to take the practical nurse licensing examination at the end of the first year, management concepts and experiences are introduced during the second semester. Many students work as licensed practical nurses and are expected to manage care for groups of clients. Using this model, students work together to practice time management and leadership skills.

Photoplethysmographic documentation of improved microcirculation after pentoxifylline therapy

Pentoxifylline is the prototype of a new class of drugs that improve peripheral blood flow mainly by increasing red blood cell flexibility. Few studies have been performed to objectively evaluate the effect of the drug in a routine clinical setting. In 11 patients with intermittent claudication, photoplethysmography was used to monitor the effect of pentoxifylline on the microcirculation in the lower extremities. Values obtained improved significantly (p less than .0001) under therapy. Concomitant measurements of ankle-brachial indices showed no significant changes despite clinical improvement. Diabetic patients in this study seemed to benefit from treatment with pentoxifylline at least as much as nondiabetic patients. Photoplethysmography proved to be a very efficient and inexpensive method of studying the effects of pentoxifylline. Ankle-brachial indices are not a suitable method of detecting flow changes attributable to the mechanism of action of this drug.

Fascioliasis in dairy cows on irrigated pasture

The prevalence and severity of fascioliasis was studied in 87 dairy cows from 36 irrigated farms in Victoria. Evidence of Fasciola hepatica infection was found in 85 (98%) cows representing all but one of the herds. The mean fluke burden (7 +/- 6) in cows treated with anthelmintics at drying off was lower (p < 0.05) than in untreated cows (24 +/- 7). Haemoglobin levels in untreated cows (9.6 +/- 0.04) were higher (p < 0.05) than values obtained from treated animals (8.2 +/- 0.3). Severity of bile duct wall thickness and hepatic fibrosis was similar in both groups. None of the measured parameters was affected by the age of the cow. Although fascioliasis was prevalent in these cattle the level of infection was low.

Effects of steroids on the enzymatic pathways of lecithin production in fetal rabbits

The present study was undertaken to study the effect of corticosteroids on lecithin production in fetal lung. Rabbit fetuses were injected intraperitoneally with hydrocortisone succinate at 24 days of gestation and sacrificed at 27 days. Lung DNA concentration was not changed, but evidence is presented to suggest that total lung DNA content was decreased by saline injection and by steroid injection. Minimum surface tension of pooled lungs was increased by control injections but was reduced to ‘normal’ levels by the steroids. Steroids caused no significant change in lung total phospholipid or lecithin contents. The specific activity of labelled choline, methionine and palmitate indicated increased incorporation of choline and palmitate into lung lecithin in steroid-injected fetuses. It is suggested that steroids accelerate fetal lung development by influencing the composition of surfactant at the alveolar surface.