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At least 19 recordsLinked to original sources

PubMed1979

The inaccuracy of using 100% oxygen to determine intrapulmonary shunts in spite of PEEP.

The use of 100% oxygen to determine intrapulmonary shunting has been widely advocated. This study was performed to determine the clinical application of this technique in critically ill patients on PEEP. Determinations of intrapulmonary shunting using FIO2 of 0.45 and 1.0 were performed on 18 patients. Machine error was also calculated. Shunt calculations increased by an average of 52% (29% corrected for machine error) with the use of an FIO2 of 1.0 and returned to previous levels when an FIO2 of 0.45 was reinstituted. There was no statistical difference in shunt increase between patients on high (greater than or equal to 15 cm H2O) or low (less than 15 cm H2O) PEEP. The use of 100% oxygen to calculate intrapulmonary shunting in patients on PEEP is misleading in both physiological and methodological terms.

Blood Gas Analysis↗

PubMed1978

Oxygen-related intrapulmonary shunting in obstructive pulmonary disease.

A simple and previously validated double-indicator technique was used to quantitate shunt in patients with obstructive pulmonary disease at rest, during exercise, and during breathing of 100 percent oxygen. The method avoids several inherent difficulties encountered in previous double-indicator techniques and is independent of the fraction of oxygen in the inspired gas. Sixteen resting patients with mild obstructive pulmonary disease were found to have intrapulmonary shunting less than or equal to 0.7 percent of the cardiac output (mean, 0-3 +/- 0.2 percent [SD]). During submaximal exercise, shunting was also low (mean, 0.3 +/- 0.1 percent of cardiac output). After breathing pure oxygen for 30 minutes, 11 patients had similar results; however, in four patients, breathing 100 percent oxygen caused an increase intrapulmonary shunting to 1 to 6 percent of the cardiac output. It is concluded that some patients with obstructive pulmonary disease develop intrapulmonary shunting in response to breathing oxygen.

Cardiac Output↗

PubMed1979

Influence of cardiac output on intrapulmonary shunt.

The effect of changing cardiac output on intrapulmonary shunt was studied in the setting of hemorrhagic pulmonary edema induced by intravenous oleic acid in 17 alpha-chloralose-anesthetized dogs. The dogs were mechanically ventilated and cardiac output was alternately depressed and augmented using either pharmacologic means or mechanical alteration of venous return. Following oleic acid, the measured ventilation-perfusion distributions, as measured by the multiple inert gas elimination technique, demonstrated a two-compartment blood flow distribution consisting of shunt and normal units. Changes in cardiac output were not associated with change in the shape of the distributions but there was a significant linear correlation between the level of cardiac output and the shunt fraction. The shunt fraction also varied directly with the mixed venous partial oxygen pressure and inversely with the pulmonary vascular resistance. These data suggest that shunt and nonshunt vessels behave differently in response to alterations of blood flow and emphasize that any interpretation of changes in shunt in the setting of diffuse lung injury must be interpreted in light of changes in cardiac output.

Animals↗

PubMed1975

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.

Acid-Base Equilibrium↗

PubMed1979

Effect of dopamine on intrapulmonary shunt fraction and oxygen transport in severe sepsis with circulatory and respiratory failure.

The hemodynamic response to a dopamine HCl infusion (10 microgram/kg per min) was measured in 25 adult patients with severe sepsis: there were 6 patients with circulatory hyperdynamic states, 9 patients with myocardial failure, and 10 with hypovolemia. Each patient also had acute respiratory failure. Changes of intrapulmonary shunt fraction (Qs/Qt), arterial and mixed venous oxygen tension (PaO2 and PvO2), oxygen transport, and oxygen consumption (VO2) were evaluated before and after dopamine infusion. Dopamine infusion produced clinical improvement and increased cardiac output. The hemodynamic response seemed to differ slightly according to the pattern of circulatory failure: chronotropic effect appeared to be predominant in hyperdynamic states, whereas inotropic effect appeared to be predominant in myocardial failure or hypovolemia. Moreover, in hypovolemic patients we noted a rise in pulmonary capillary wedge pressure suggesting an additional increase in venous return. During this treatment, we also noted a worsening of the Qs/Qt despite the increase in pulmonary blood flow; this worsening did not prevent significant improvements in VO2, but the improvement in PVO2 was offset by increased Qs/Qt and PaO2 remained unchanged.

Adult↗

PubMed1979

An improved program to calculate intrapulmonary shunting.

A computer program was developed to calculate intrapulmonary venous admixture on a Texas Instruments TI 59 programmable calculator. The program incorporates the following characteristics: 1) a correction for saturated water vapor pressure which varies with body temperature; 2) a mathematical model of the standard oxyhemoglobin dissociation curve; and 3) correction factors for shifts of the dissociation curve due to variations in pH and carbon dioxide tension. It also corrects oxygen tensions obtained at electrode temperature to those at patient temperature, and calculates variations of the Bunsen solubility coefficient of oxygen in blood with body temperature.

Bionics↗

PubMed1979

[Determination of intrapulmonary shunt in acute lung failure and during therapy by means of extracorporeal oxygenation (author's transl)].

The reasons for the especial importance of acute lung failure within the framework of intensive medicine are elaborated. In most cases acute lung failure can be successfully treated by timely ventilation and support for the heart-function. If conventional therapy fails, extracorporeal long-term oxygenation by means of a membrane oxygenator can be a successful technique, provided that a very critical indication is available. The magnitude of the intrapulmonary right-left shunt S is an important parameter for the assessment of the extent of acute lung failure and its prognosis, and also in the establishment of the indication for the use of extracorporeal oxygenation and the therapeutic process. The derivation of simple extended shunt equations for any form of extracorporeal oxygenation is possible on the basis of measurements of blood-flow and oxygen transport. This represents an important contribution to the mathematical description of a therapeutic technique.

Biological Transport↗

PubMed1979

[A study of the alveolar-arterial oxygen gradients and intrapulmonary shunt under the action of NAB-365, a new exogenous catecholamine of selective beta-2 action (author's transl)].

Thirty patients were studied using NAB-365 (clenbuterol), an exogenous catecholamine with selective beta-2 action to determine various parameters of pulmonary physiopathology. They included: alveolar-arterial gradients in partial oxygen pressures, coefficient of respiratory inefficacy, alveolar ventilation, and intrapulmonary venoarterial short circuits. By studying these parameters before and after clinical administration of clenbuterol we were able to demonstrate a decrease in the alveolar-arterial oxygen gradients (p less than 0.001), decrease in the respiratory inefficacy coefficient (p less than 0.001), increase in alveolar ventilation (p less than 0.001), and a shunt decrease (p less than 0.0025). The drug improves diffusion and oxygenation without affecting the adrenergic cardiac receptors.

Clenbuterol↗

PubMed1975