Optimum criteria for the diagnosis of ventricular septal defect from measurements of blood oxygen saturation

A combination of physical findings, x-ray films and fluoroscopy, electrocardiography, vectorcardiography, cardiac catheterization including oxygen analysis, indicator-dilution curves, and selective angiocardiography was employed to evaluate 259 consecutive patients undergoing right heart catheterization. All patients were classified on the basis of existing shunts. The present report concerns 63 patients with no shunts and 70 patients with a left-to-right shunt through a ventricular septal defect alone.

A method employing oxygen analysis of right heart blood was evaluated as an isolated diagnostic technic. Blood specimens were obtained in rapid sequence during withdrawal of the catheter from the pulmonary arteries. Spectrophotometric measurements of blood oxygen saturation were appropriately grouped. The difference in means between the right ventricular outflow tract and right atrium was standardized with the estimated standard deviation and the statistical significance determined from the t -distribution.

Reliability was defined as the probability of correctly excluding a shunt when none exists. Sensitivity was defined as the probability of diagnosing an existing shunt. By use of the 1-per cent level of signfiicance as critical the method employed was 98.4 per cent reliable and 97.1 per cent sensitive.

Sequential sampling is of vital importance. The value of larger numbers of specimens is illustrated, and the relationship of sensitivity and reliability to the size of the shunt and the number of blood specimens analyzed is illustrated.

The reliability and sensitivity of our method and criteria appear superior to previous criteria currently in use.

Cardiorespiratory effects of large pneumothorax in conscious and anesthetized dogs

Ventilation, arterial blood gases, diffusing capacity for carbon monoxide, and flow and pressure in the pulmonary circulation were measured in conscious and pentobarbital-anesthetized dogs at intervals up to 5 hr after intrapleural injection of air. Pneumothorax of twice the functional residual capacity increased the frequency of breathing and reduced physiological dead space in both conscious and anesthetized dogs, but conscious dogs were otherwise unaffected. In contrast, the arterial blood oxygen saturation fell, pulmonary artery pressure rose, and carbon monoxide diffusing capacity was reduced in anesthetized dogs despite greatly increased respiratory minute volume and alveolar ventilation. Ventilation was depressed by anesthesia alone in controls and improved gradually during the experiments. Pentobarbital anesthesia appeared to augment cardiorespiratory depression or abolish compensatory reactions evoked by pneumothorax to produce effects in anesthetized dogs which did not occur in their conscious counterparts. The potent effects of pentobarbital anesthesia on ventilation, pulmonary circulation, and carbon monoxide diffusing capacity, emphasize the advantage of conscious subjects in cardiorespiratory studies.

Submitted on July 25, 1962

Solubility of carbon dioxide in serum from 15 to 38 C

The solubility of carbon dioxide in serum has been determined from 15 to 38 C. Consideration was given to the water, lipid, protein, and electrolyte composition of the serum which influences the solubility. It was concluded that the direct determination of the solubility of carbon dioxide in serum yields significantly different values from those extrapolated from 38 C based on an assumed parallel relationship between serum and water. New solubility factors and pK's have been calculated from this information.

Submitted on July 5, 1962

PULMONARY EXCHANGE AS RELATED TO ALTERED PULMONARY MECHANICS IN ANESTHETIZED DOGS

Pulmonary mechanics and gas exchange were studied in supine anesthetized dogs, with and without periodic hyperinflations of the lungs, and after a single forced deflation. After a period without hyperinflations the lung compliance decreased to 66% of control values and patchy atelectasis was observed, but no changes were observed in diffusing capacity (Dl) or per cent venous admixture ( Qva/ Qt). Following a single forced deflation the compliance was 40% of control. Dl was 40% and Qva/ Qt 180% of control values, respectively. These data could be accounted for if there was an accompanying shift of blood flow from atelectatic to nonatelectatic areas, the compensation being very nearly complete for moderate, but less than complete for marked reductions in compliance. Alternative explanations of the apparent compensation are: 1) preferential initial atelectasis of regions with high ventilation-perfusion ratios (as proposed by Farhi) and 2) substantial reductions in compliance without closure of air space, as might result from changes in surface forces with time.

aerotonometer; atelectasis; venous admixture; mechanics of breathing; compliance of dog lungs; diffusion capacity of dog lungs; ventilation perfusion; relationships of dog lungs

Submitted on October 28, 1963

GASEOUS DIFFUSION FROM ALVEOLI TO PULMONARY VESSELS OF CONSIDERABLE SIZE

Thirty patients have been presented in whom the appearance of inhaled hydrogen gas at an electrode in the wedge position of a pulmonary artery was seen to occur within two seconds. In 13 of these patients the appearance of hydrogen occurred with equal or nearly equal rapidity in a pulmonary artery at least 3 mm in diameter. In 11 patients increasing alveolar oxygen tension by the inhalation of a single breath of 100% oxygen or by voluntary hyperventilation produced a rapid response at the wedge position as well. It is concluded that the rapid appearance of hydrogen and oxygen is due to direct diffusion of the inhaled gas from the alveoli to the pulmonary arterial blood.

THE SECRETION OF OXYGEN INTO THE SWIM-BLADDER OF FISH. 3. THE ROLE OF CARBON DIOXIDE

The secretion of carbon dioxide accompanying the secretion of oxygen into the swim-bladder of the bluefish is examined in order to distinguish among several theories which have been proposed to describe the operation of the rete mirabile, a vascular countercurrent exchange organ. Carbon dioxide may comprise 27 per cent of the gas secreted, corresponding to a partial pressure of 275 mm Hg. This is greater than the partial pressure that would be generated by acidifying arterial blood (about 55 mm Hg). The rate of secretion is very much greater than the probable rate of metabolic formation of carbon dioxide in the gas-secreting complex. It is approximately equivalent to the probable rate of glycolytic generation of lactic acid in the gas gland. It is concluded that carbon dioxide brought into the swim-bladder is liberated from blood by the addition of lactic acid. The rete mirabile must act to multiply the primary partial pressure of carbon dioxide produced by acidification of the blood. The function of the rete mirabile as a countercurrent multiplier has been proposed by Kuhn, W., Ramel, A., Kuhn, H. J., and Marti, E., Experientia, 1963, 19, 497. Our findings provide strong support for their theory. The unique structure of the gas-secreting complex of the swim-bladder of the bluefish, Pomatomus saltatrix L., is described.

TOLERANCE OF DOG LUNG TO HYPERTHERMIC PERFUSION

Hyperthermia of the left lung of the dog was produced by pulmonary artery perfusion in 29 animals. It was found that the lung tolerates tissue temperatures up to 43 C for periods as long as 60 min without significant permanent disturbance of structure or function as measured by blood gas analysis, angiography, and contralateral pulmonary artery ligation. Elevation of the lung temperature above 43 C for periods longer than 10–12 min resulted in partial or total destruction of pulmonary tissue. Data are presented regarding perfusion techniques, factors affecting lung tolerance to hyperthermia, and possible areas for future study.

MEASUREMENT OF PULMONARY EDEMA

Two methods for the measurement of pulmonary edema are compared. The first method, which permits serial measurements in vivo, depends on the difference in mean transit time of a water label and an intravascular label. The second method is a postmortem one in which total lung water is measured and allocated to the pulmonary blood or to pulmonary extravascular water.

Three groups of six dogs each were studied: controls, a group with pulmonary edema produced by elevating pulmonary venous pressure, and a group with pulmonary edema produced by alloxan. The isotopic as compared with the postmortem method accounted for 71% of the pulmonary extravascular water found in the controls, 94% in high pressure edema and 57% in alloxan edema. Shunting, as measured by a large fall in PaO 2 despite 100% oxygen breathing, became marked in a second group of five alloxan dogs and only 31% of the postmortem pulmonary extravascular water was measured by the isotope method.

It is concluded that the isotope transit time method is a useful one for the serial measurement of pulmonary edema in vivo. The edema water is determined more accurately when pulmonary edema is due to elevated pulmonary venous pressure than when due to increased vascular permeability.