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Biomedical subjects

B D Butler

Publications and source records attributed to B D Butler.

65 records · Page 4Linked to original sources
PubMed1983

Role of lung surfactant in cerebral decompression sickness.

Five dogs have been embolized by air infusion into the venous system, then sacrificed and the pulmonary vasculature isolated by ligatures while ventilation was maintained for a further hour. In a sixth animal, the embolization was omitted. The lungs were back-perfused with plasma from the same dog and successive aliquots of the back-flushings analysed by thin-layer chromatography (TLC), each spot being removed for phosphorus determination. The results showed that the major lipid component was the phosphatidyl cholines, while lysophosphatidyl cholines, phosphatidyl ethanolamines, and sphingomyelins were also identified in significant quantities. A phosphorus balance for the lungs showed a significant migration of phospholipids from the tissue into pulmonary blood, phosphatidyl cholines increasing by a factor of 10.6. This migration of surfactant is discussed as an important factor in determining whether trapped pulmonary air emboli are released into the arterial system when their surface area is reduced by pressurization, suggesting that recompression should not be too rapid.

Animals↗
PubMed1982

Boundary lubrication imparted by pleural surfactants and their identification.

Phospholipids have been identified in pleural washings from live dogs and were found to include phosphatidylethanolamines, sphingomyelin, and, predominantly, phosphatidylcholines. The extracts were highly surface active when studied on the Langmuir trough using a Wilhelmy balance and produced surface tension/area loops similar to those for synthetic phosphatidylcholines and phosphatidylethanolamines but differing from the pure dipalmitoyl derivative (DPL). The extracts, the synthetic surfactants and their mixtures, were all found to be good lubricants when tested by a standard method for evaluating textile "sizes." The results are consistent with the classical theory of "boundary" lubrication for which surfactant molecules would have an almost ideal molecular structure for adsorption, film cohesion, and mutual interaction of the hydrophobic ends. This concept is suggested as a mechanism that can explain some of the anomalies in the hydrodynamic theory of sliding of the pleurae and may possibly apply to other surfaces.

Animals↗
PubMed1981

A method of producing calibrated microtubules for air embolism studies.

Utilizing the differential absorption techniques in conjunction with gas injection methods has enabled the production of calibrated microtubules with diameters ranging from 14 to 300 micron. Nitrogen was blended with CO2, the "diluent" gas, to produce the initial bubbles, while tris(hydroxymethyl)-aminomethane hydrochloride (THAM) was used as an absorbent to remove the diluent gas from the bubbles. Hence, the diameters of the initial bubbles were significantly reduced with only the inert gas remaining. The Coulter counter was used for immediate size monitoring of the microtubules. To verify the inertness of the absorbent medium, nine anesthetized dogs were infused with increasing amounts of the solution. In five of the animals plasma surface tension and pH (arterial) were measured, while in the remaining four arterial blood pressure, heart rate, breathing frequency, and pulmonary artery pressure was measured before, during, and after the injections. Changes in plasma surface tension and pH were minimal while acceptable physiological values were recorded, all of which were in agreement with previous investigations. Differential absorption techniques provided a reliable means for producing calibrated micro-bubbles for air embolism studies.

Embolism, Air↗
PubMed1981

Size distribution of intravascular air emboli produced by decompression.

Intravascular bubbles formed by decompression have been measured in 7 living dogs to give 14 different determinations of size distribution. Larger bubbles were estimated by the terminal rise velocity technique using the Stokes equation, while smaller bubbles were determined simultaneously, using the Coulter counter. Bubble diameters of 19--700 micrometers were recorded, these reaching the venous sinus as showers of several hundred whose mean size tended to increase with post-decompression time. Average diameters were rather smaller than previously recorded from autopsy. The results are discussed as indicating that all venous bubbles were within a size range where they would be filtered out by the lungs unless this organ had been insulated.

Animals↗
PubMed1979

The lung as a filter for microbubbles.

A new ultrasonic Doppler device has been used noninvasively over the femoral artery of anesthetized dogs to prove that it can detect carefully calibrated microbubbles of 14--189 micrometers diam when these are infused directly into the aorta. The same evaluated technique has then been employed to detect any bubbles escaping into the arterial system when gas was infused into the venous system either as microbubbles or as a bolus. Results from 18 dogs showed that, under normal conditions, the lungs are a superb filter for bubbles and that any cutoff diameter is less than 22 micrometers. However, bubbles escaped entrapment when the lungs were severely overloaded with gas (20 ml) or were pretreated with a pulmonary vasodilator (aminophylline). The dog preparation and arterial Doppler device appear to be ideal for future studies to determine what other factors might compromise the capability of the lungs to filter microbubbles. Physiological parameters showed dramatic changes when bubbles were detected as escaping into the arterial system by comparison with their effect when retained within the lungs. Changes in respiration profile indicated that they may offer a useful index of the degree of venous embolization and, hence, a warning of impending overload leading to arterial embolization.

Air↗
PubMed1978

The kangaroo rat as a model for type I decompression sickness.

This study involved 720 exposures of 70 kangaroo rats trapped in West Texas and showed that decompression-induced tail biting in this animal provides a good animal model for marginal limb bends in man. That this phenomenon can be reversed by recompression and pathological examination of the tail both indicated that a similar mechanism is probably involved in kangaroo rats and humans. Quantitatively, the most susceptible 20% of kangaroo rats can reproduce the no-stop decompression limits for man for exposure times ranging from 5 min to 8 h, for both air and helium-oxygen. Even the average minimum no-tail-biting depth of 46.2 fsw (2.40 ATA) for this species is much closer to the minimum bends depth of man than to the equivalent depth for other animals of its size, and is as good as the goats'. Its size and habits make the kangaroo rat much more convenient than other animals to use as a model for marginal decompression sickness, and particularly attractive economically for testing long helium-oxygen schedules and other means of decompression sickness prevention.

Animals↗
PubMedDate not supplied

Biophysical aspects of gas bubbles in blood.

The widespread use of bubble oxygenators during cardiopulmonary bypass has raised questions concerning the production and introduction of gaseous microemboli (GME) into patients. An understanding of the complications associated with GME requires awareness of the biophysical and biochemical responses that occur between bubbles and blood. The production of GME as well as their interactions with each other and with blood products are examined. These interactions can influence the data collected from Doppler ultrasound devices and the development of organ dysfunction.

Cardiopulmonary Bypass↗