Biomedical subjects

H W Calderwood

Publications and source records attributed to H W Calderwood.

At least 19 recordsLinked to original sources

PubMed1979

Renal function and cardiovascular responses during positive airway pressure.

The authors determined cardiovascular, renal, and hormonal responses to increased airway pressure during continuous positive-pressure ventilation (CPPV) and continuous positive airway pressure (CPAP). Nine healthy, hydrated laboratory swine had appropriate catheters placed to allow for measurement of intrapleural, aortic, inferior vena caval, and left ventricular end-diastolic pressures; cardiac output; and urinary flow. Samples of arterial blood were analyzed for oxygen and carbon dioxide tensions, pH, plasma vasopressin, osmolality, and creatinine and sodium concentrations. Urine was analyzed for osmolality and creatinine and sodium concentrations, and volume was recorded. Intrapleural pressure was subtracted from left ventricular end-diastolic pressure to calculate transmural pressure, a reflection of left ventricular filling pressure. Glomerular filtration rate and urinary free-water and osmolal clearances were also calculated. Expiratory left ventricular filling pressure was decreased equally by CPAP and CPPV. However, inspiratory left ventricular filling pressure and cardiac output were decreased by CPPV only. Urinary flow and glomerular filtration rate were decreased equally by CPAP and CPPV. Sodium excretion was decreased and plasma vasopressin increased by CPPV, but not by CPAP. Urinary free water and osmolal clearances were not changed by either ventilatory pattern. Although many of the renal-function variables were affected similarly by CPPV and CPAP, these alterations were not influenced solely by cardiac output or vasopressin, because only CPPV depressed cardiac output and increased vasopressin levels.

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↗

PubMed1975

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 Ringer's 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, HCO3- and in-vivo 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 concomitant depression of arterial pH. No pneumothorax occurred. High PEEP was well tolerated with intermittent manditory ventilation, intravascular volume expansion, and careful cardiovascular monitoring.

Animals↗

PubMed1975

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

The authors evaluated the efficacy of continuous positive-pressure ventilation (CPPV) and methylprenisolone alone and in combination as therapy for near-drowning in 80 dogs that had aspirated distilled water (22 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. (Key words: Drowning, fresh-water; Hormones, adrenal, methylprednisolone.)

Adrenal Cortex Hormones↗

PubMed1975

Residual levels and biochemical changes after ventilation with perfluorinated liquid.

Twenty-three beagle dogs were ventilated with perfluorinated liquid, perfluoro-1-isopropoxy-hexane (Caroxin-F) for 1 h and were reconverted to gaseous breathing. Hematologic and biochemical changes were studied in five dogs for 1 yr and the remaining animals were followed for evidence of retained Caroxin-F for up to 3 yr. We found that the dogs could be ventilated with liquid Caroxin-F and returned to spontaneous breathing of gaseous oxygen with normal blood gas exchange within 24-72 h. Serum alkaline phosphatase, serum cholesterol, and white blood cell count increased with liquid ventilation but returned to normal in less than 1 wk. Trace amounts of Caroxin-F were detected by chromatography in all tissues studied for the entire 3-yr period. The highest levels of Caroxin-F were found in the lungs and associated lymph nodes. No histologic evidence of the presence of Caroxin-F was seen except for local accumulations of vacuolated macrophages in the lungs and associated lymph nodes. We conclude that Caroxin-F can be breathed without residual deleterious effects, even though trace amounts remained for at least 3 yr.

Alkaline Phosphatase↗

PubMed1975

Cardiopulmonary effects of xylazine in dogs.

Effects of the drug xylazine were determined on arterial pH, arterial oxygen pressure (PaO2), arterial carbon dioxide pressure (PaCO2), aortic blood pressure, aortic flow, heart rate, pulse pressure, stroke volume, and peripheral resistance of dogs. The drug was given intravenously (IV) with and without atropine and was given intramuscularly (IM) without atropine. After IV administration of xylazine (1.1 mg/kg), arterial pH, PaO2, and PaCO2 values were not changed from control values. However, the drug did produce a statistically significant decrease in heart rate, decrease in aortic flow, initial increase in blood pressure followed by decrease, and increase in peripheral resistance. Stroke volume and pulse pressure were not significantly changed. Atropine (0.02 mg/kg, IV) did not significantly change any of the effects produced by xylazine. Intramuscular administration of xylazine (2.2 mg/kg) did not produce significant changes in arterial pH, PaO2, or PaCO2. Heart rate and aortic flow decreased significantly, but statistically significant changes did not occur in aortic blood pressure or peripheral resistance; however, the changes in these last 2 values were in the same direction and were of similar magnitude as those which occurred afger IV administration of xylazine.

Animals↗

PubMed1974