Bruce C. Ruiz

Pulmonary aspiration: effects of volume and pH in the rat

To evaluate the effect of volume of aspirates with different pHs on mortality associated with pulmonary aspiration, hydrochloric acid solutions were injected into the tracheas of 336 Sprague-Dawley rats. The rats were divided randomly into 33 groups, were observed for 96 hr after aspiration, and wer

The Effects of Fluid Volume in Seawater Drowning

Excerpt The effect of drowning by total immersion in seawater on the serum electrolytes, blood constituents, and cardiovascular system of dogs was reported by Swann and Spafford (1). In their exper...

Cardiorespiratory effects of high positive end-expiratory pressure.

Five healthy rhesus monkeys were ventilated with intermittent mandatory ventilation and 20 torr positive end-expiratory pressure (PEEP) for 8 hours. PEEP was increased to 25 torr and the monkeys were ventilated for 4 more hours. Lactated Ringers solution and human salt-poor albumin were used to expand plasma and extracellular fluid volume throughout the entire period of study. Homologous blood was administered to maintain hematocrit at control levels and maintenance fluids were infused to maintain transmural pulmonary capillary wedge pressure at 5 to 15 torr. Although cardiac output, mean aortic blood pressure, oxygen consumption, venous admixture, transmural pulmonary capillary wedge pressure, HCO,-and in-cico base excess were not changed when intermittent mandatory ventilation was employed, cardiac output and blood pressure were significantly depressed by brief periods of controlled mechanical ventilation when alternated with intermittent mandatory ventilation. Sporadic increases in arterial-venous oxygen content difference occurred. Arterial carbon dioxide tension was elevated moderately, with a concomtant depression of arterial pH. No pneumothorax occuned. High PEEP was well tolerated with intermittent manditory ventilation, intravascular volume expansion, and careful cardiovascular monitoring.

Effects of Ventilatory Patterns on Arterial Oxygenation after Near-drowning in Sea Water

Forty-three dogs were anesthetized and subjected to aspiration of 22 ml/kg of sea water. After 5 minutes, fluid was drained from the lungs by gravity; 33.1 ± 5.9 ml/kg were recovered. Thirty-four dogs were apneic at this time and were treated with intermittent positive-pressure ventilation with a self-inflating bag. Forty-five minutes later, the 40 animals that survived were divided into four equal groups; one group breathed spontaneously and served as a control, the second was treated with IPPV, the third breathed spontaneously against 10 cm H2O PEEP, and the fourth received IPPV plus PEEP (i.e., CPPV). Arterial oxygen tensions of the animals in both groups with PEEP significantly increased during the 75-minute treatment period. By 48 hours two more dogs had died; however, Pa2s had returned to normal in the 38 that survived, regardless of me mode of treatment It is concluded that gravity drainage and immediate mechanical ventilation of victims who aspirate large quantities of sea water are important, since 40 of the 43 animals were resuscitated after being submerged for 5–10 minutes. Blood-gas data showed that positive end-expiratory pressure, with or without mechanical ventilation, significantly increased PaO2 after aspiration of sea water, suggesting that it is indicated in the treatment of sea-water near-drowning victims. Two case reports of human victims of near-drowning in sea water which support the animal studies are presented.

A program for calculation of intrapulmonary shunts, blood-gas and acid-base values with a programmable calculator.

With a desk-top, programmable calculator, it is now possible to do complex, previously time-consuming computations in the blood-gas laboratory. The authors have developed a program with the necessary algorithms for temperature correction of blood gases and calculation of acid-base variables and intrapulmonary shunt. It was necessary to develop formulas for the Po2 temperature-correction coefficient, the oxyhemoglobin-dissociation curve for adults (withe necessary adjustments for fetal blood), and changes in water vapor pressure due to variation in body temperature. Using this program in conjuction with a Monroe 1860-21 statistical programmable calculator, it is possible to temperature-correct pH,Pco2, and Po2. The machine will compute alveolar-arterial oxygen tension gradient, oxygen saturation (So2), oxygen content (Co2), actual HCO minus 3 and a modified base excess. If arterial blood and mixed venous blood are obtained, the calculator will print out intrapulmonary shunt data (Qs/Qt) and arteriovenous oxygen differences (a minus vDo2). There also is a formula to compute P50 if pH,Pco2,Po2, and measured So2 from two samples of tonometered blood (one above 50 per cent and one below 50 per cent saturation) are put into the calculator.

Distribution and retention of fluorocarbon in mice and dogs after injection or liquid ventilation

Abstract Three groups of mice (strain ICR) were injected with either fluorocarbons FX-80, Caroxin-D, or with isotonic saline. The growth rates among these groups were not statistically different at 48 weeks. Seventeen to 19 months after the fluorocarbons were injected sc or ip, mice were sacrificed and the concentration of fluorocarbon in various tissues was determined by gas chromatography. In a second experiment, the lungs of dogs were ventilated with Caroxin-D fluorocarbon for 1 hr, after which they were reconverted to breathing gas. Twenty to 23 months later they were sacrificed, and the concentration of fluorocarbon in various tissues was determined. Except for the source of introduction of the fluorocarbon (the lung in dogs, which contained approximately 160 mg of fluorocarbon/100 g of tissue), other tissues in both dogs and mice contained minute quantities of fluorocarbon (approximately 0.1 mg/100 g). The highest concentration of fluorocarbon was found in fat.

The ineffectiveness of steroid therapy for treatment of fresh-water near-drowning.

The authors evaluated the efficacy of continuous positive-pressure ventilation (CPPV) and methyl-prenisolone alone and in combination as therapy for near-drowning in 80 dogs that had aspirated distilled water ml/kg or 44 ml/kg). Forty dogs were treated with mechanical ventilation for one hour and 40 for 24 hours. Blood-gas tensions, pH, cardiac output and intrapulmonary shunt (Qs/Qt) were measured frequently for 24 hours. Blood-gas tensions and pH were again measured 48 and 72 hours and seven days later in survivors. Arterial oxygen tension (Pao2) decreased and Qs/Qt increased in all animals following aspiration and before therapy. Forty dogs received methylprednisolone intravenously (30 mg/kg) (20 breathed spontaneously and 20 had CPPV). There was a significant increase in Pao2 and decrease in pulmonary shunt in dogs that were ventilated mechanically compared with animals that breathed spontaneously. Treatment with methylprednisolone made no difference in blood gases, pulmonary shunt, or survival rates. Thus, no evidence to support the use of methylprednisolone in the treatment of the pulmonary lesion of fresh-water near-drowning was found.

Pulmonary lavage with liquid fluorocarbon in a model of pulmonary edema.

An animal model of a specific type of acute pulmonary edema was produced by instilling a concentrated sucrose solution into each mainstem bronchus of 20 dogs. The resulting disease was treated with either 100 per cent oxygen via fixed-volume ventilation with PEEP at 10 cm H2O (control group), or pulmonary lavage with oxygenated Caroxin-D fluorocarbon liquid for one hour followed by reconversion to breathing 100 per cent oxygen by mechanical ventilation with PEEP. More edema fluid was recovered during the washout period (22.8 ± 8 ml/kg) than during the corresponding time in the control group (14.2 ± 10 ml/kg). The washout group also had a significantly higher and more prolonged elevation in Pao2 than the control group. Pulmonary lavage with fluorocarbon in the treatment of acute, massive pulmonary edema appeared beneficial and warrants further study.

Oxygenation by ventilation with fluorocarbon liquid (FX-80).

Thirty-six mongrel dogs were ventilated with oxygenated fluorocarbon liquid (FX-80) for an hour and then reconverted to breathing gaseous oxygen. For several days after breathing this liquid, the dogs were hypoxemic while they breathed air. The authors attributed this to residual fluorocarbon in the lung and/or partial airway closure. By ten days after liquid ventilation, Pao2s had returned to pre-experimental control levels. Pathologic examination of the lungs three hours after termination of liquid ventilation disclosed an acute exudative inflammatory reaction largely confined to the bronchioles. By 72 hours the acute reaction had subsided and the dominant change consisted of vacuolated intra-alveolar macrophages, presumably containing fluorocarbon. At ten days, macrophages were still present, but generally in much smaller numbers; after a month only scattered small groups were found. At 18 months the lungs were normal.

Pulse oximetry fails to accurately detect low levels of arterial hemoglobin oxygen saturation in dogs.

The accuracy of two commercially available pulse oximeters (the Ohmeda Biox 3700, software version “J,” and the Nellcor N-100) in detecting low levels of arterial hemoglobin oxygen saturation (SaO2) was evaluated in 10 dogs in which hypoxia was induced by stopping the fresh gas flow into the anesthesia machine circle system. Measurements made in vivo with the pulse oximeters, with detectors placed on the tongue, were compared with measurements made in vitro using an IL 282 CO-Oximeter as SaO2 decreased toward zero. Measurements from the two oximeters correlated poorly over the range from 0 to 100% SaO2 (r = 0.69). In this range, the correlation between Nellcor N-100 measurements and those of the CO-Oximeter had an r of 0.82, a regression line slope of 0.82, and a y intercept of 14.8; the correlation between the Ohmeda Biox 3700 and the CO-Oximeter had an r of 0.83, a regression line slope of 0.66, and a y intercept of 32.7. The correlation with the CO-Oximeter was similar for both the Ohmeda and the Nellcor pulse oximeters at an SaO2 of 80% or more. However, when SaO2 was less than 80%, measurements by pulse oximetry correlated less well with CO-Oximeter measurements (r = 0.62, slope = 0.64, and y intercept = 21.0 for Nellcor; r = 0.71, slope = 0.67, and y intercept = 32.4 for Ohmeda). When SaO2 was less than 60%, both oximeters inaccurately indicated the co-oximetry values (r = 0.36 and y intercept = 26.1 for the Nellcor; r = 0.48 and y intercept = 33.2 for the Ohmeda). In this animal model, with pulse oximeter measurements obtained from the tongue and with rapidly decreasing SaO2, measurements of SaO2 by pulse oximetry become inaccurate in comparison with co-oximetry measurements at low levels of SaO2.