Albert J. Olszowka

A system of digital computer subroutines for blood gas calculations.

Abstract A system of digital subroutines which considers all possible relationships between the gas constituents of blood is described. The subroutines apply to blood samples with any level of hemoglobin and base excess. Two specific applications of the subroutines are given: 1) a program that will draw a Dill nomogram of the blood, and 2) a program that constructs Va/q lines.

Cardiac output determination by simple one-step rebreathing technique.

We have developed a rebreathing technique for measuring cardiac output in resting or exercising subjects. The data needed are the subjects CO2 dissociation curve, the initial volume and CO2 fraction of the rebreathing bag, and a record of CO2 at the mouth during the maneuver. From these one can obtain all the values required to solve the Fick equation. The combined error due to inaccuracy in reading the tracings and to the simplifying assumptions was found to be small (mean = 0.5%, SD ;.5%). Cardiac output values determined with this technique in normal subjects were on the average 2% higher than those obtained simultaneously with an acetylene rebreathing method (n = 49, SD = 11%). Among the advantages of the technique are that it requires analysis of a single gas, takes less than thirty seconds per determination, allows one to obtain repeated measurements at rapid intervals, is not affected by the ability of lung tissue to store CO2, and eliminates many of the assumptions usually made in non-invasive measurements of cardiac output.

Can a/ distributions in the lung be recovered from inert gas retention data?☆

It has been suggested that the true distribution of ventilation-perfusion ratios can be determined from measurements made during the excretion of six different inert gases. This report shows that a number of considerably different distribution patterns will yield the same retention data, even in the absence of analytical error. Therefore, although analysis of inert gas retention data will allow one to arrive at a VA/Q distribution, it will not necessarily be the correct distribution.

Assessment of Ventilation-Perfusion Inequalities by Arterial—Alveolar Nitrogen Differences in Intensive-care Patients

Gas-exchange units in the lung with low &OV0312;/&OV0422; give rise to an oxygen partial pressure lower in arterial blood than alveolar gas (A-aDi>.) an N2 partial pressure higher in arterial blood than in “ideal” mixed alveolar gas (a-ADx2). Both &OV0312;/&OV0422; maldistribution and direct right-to-left shunts can contribute to the A-aDo, but only low &OV0312;/&OV0422; will cause an a-ADx2. Twenty patients from an intensive care unit were studied by measurement of the A-aDo2. and a-ADx. In 14 patients breathing an enriched oxygen mixture A-aDo.’s averaged 183 mm Hg and a-ADx.’s, 69 mm Hg. In six patients breathing room air the mean A-aDo. was 47 mm Hg; three had no a-ADx.; the other three had a mean a-ADx. of 19 mm Hg. Hence, 17 of the 20 patients showed evidence of &OV0312;/&OV0422; mismatching. Using a two-compartment model, a mixing equation was derived to calculate the percentage flow (&OV0422;o/&OV0422;T) in a compartment with a &OV0312;/&OV0422; of essentially 0 necessary to produce the measured a-ADx,. This value ranged from 9 to 46 per cent of the cardiac output in those patients with a-ADx,’s. The classic technique of separating the &OV0312;/&OV0422; component of the A-aDo, by 100 per cent oxygen breathing was found to be misleading in eight of ten cases when compared with the a-ADx, method of assessing maldistribution. It appeared that units with low &OV0312;/&OV0422; became atelectatic when 100 per cent oxygen was breathed. It was postulated that the areas of low &OV0312;A/&OV0422; occur as a result of intermittent airway closure in the most dependent areas of the lung and also in the case of interstitial pulmonary edema with airway narrowing.

Amount and rates of CO2 storage in lung tissue

The slope of the lung tissue CO2 dissociation curve and the rate of storage of CO2 in the lung tissue were studied at 22 degrees C and at 37 degrees C in 21 isolated, bloodless dog lungs with a total of 465 separate observations. Results at the two temperatures were similar. The slope of the tissue dissociation curve of lung tissue at a PCO2 of 40 torr was approximately 0.3 ml CO2 X 100 g wet tissue-1 X torr-1. Normally, this storage was 90% complete in about 5 seconds. After carbonic anhydrase inhibition by acetazolamide, the total storage capacity was unchanged, but the rate at which storage occurred decreased significantly, so that it took about 25 seconds for 90% of the storage to be completed.

Regional differences in diffusive conductance/perfusion ratio in the shell of the hen's egg

Are both gas exchange and gas tensions uniform in different regions of the developing hens egg? To answer this question we measured the O2 uptake and CO2 production of the whole egg, and at the same time the O2 and CO2 tensions of the air cell. The gas exchange ratio (R) of the whole egg differed from R calculated from air cell PO2 and PCO2 values, in agreement with the findings of Visschedijk [Br. Poultry Sci. 9:173-184 (1968)], who measured gas exchange separately over both the air cell region and the remainder of the egg. We constructed a diffusive shell conductance/perfusion (G/Q) line on the O2-CO2 diagram from a blood nomogram for the chick embryo in late development [Olszowka et al., Fed. Proc. 46:512 (1987)], and used this to analyze our results. The G/Q ratio for the area of shell over the air cell differs from that for the remainder of the egg. Our analysis permits us to calculate, for each area, the regional shell conductance, blood flow, and O2 and CO2 tensions in the gas spaces between the shell and the chorioallantoic capillaries.

A blood-gas nomogram of the chick fetus: blood flow distribution between the chorioalllantois and fetus

This paper presents equations for quantifying the relationships between the O2 and CO2 concentrations and tensions in the blood of the 18-day chick fetus. A blood-gas nomogram showing these relationships is presented. Starting with the reported chorioallantoic artery and vein gas tensions and using the blood-gas equations, the range of embryonic arterial and venous gas tensions as well as the distribution of the cardiac output and the degree of mixing between the chorioallantoic and embryonic circulations are explored. It is concluded that at least 65% of the blood in the chorioallantoic artery consists of blood of embryonic mixed venous composition. A model of the blood flow distribution is proposed in which chorioallantoic and embryonic flows are equal, with 70% of the blood returning from the tissues of the embryo going to the chorioallantois and vice versa.

Exchanges of N2 between a gas pocket and tissue in a hyperbaric environment.

Abstract Rates of N2 exit or entrance from artificially-formed subcutaneous pockets in rats were measured in hyperbaric environments. The results show that N2 diffuses into or out of the pockets as a simple straight line function of ΔP, the difference of PN2 between the gas phase in the pocket and the dissolved gas in the animalś blood and tissues. A positive correlation between the exit or entrance rate, n2, and pocket PO2 suggests that n2 is related to local blood flow of the tissue around the pocket. Decreased n2, found in old pockets can be explained by decrease of both surface area and perfusion of the pocket.

Cardiovascular and pulmonary responses to increased acceleration forces during rest and exercise.

BACKGROUND The reduced cardiac output (CO) secondary to increased acceleration forces (+Gz) has applicability to daily life and pathophysiology. Increased +Gz and reduced CO affect the lung, resulting in reduced oxygen transport. A variety of studies have examined tolerance to high +Gz. METHODS The present study examines the effect of +1 to +3 Gz on steady-state cardiopulmonary variables at rest and while exercising at +2 Gz and +3 Gz. This study also looks at the deterioration of steady-state cardiopulmonary variables with sustained increased +Gz and after de-training in eight male centrifuge trained subjects. RESULTS CO (-1.53 L x min(-1)/+Gz), stroke volume (-30 ml/+Gz, SV), and pulmonary diffusing capacity (-3.42 ml x mmHg(-1)/+Gz, DL(co)) decreased linearly with increased +Gz at rest while heart rate (23 bpm/+Gz, HR), total peripheral resistance (0.0095 TPRU/Gz TPR), mean arterial pressure (13.2 mmHg/+Gz, MAP), and ventilation (4.13 L x min(-1)/+Gz, V(E)) increased linearly. During graded exercise, CO and SV increased less at +2 Gz and +3 Gz while MAP and VE increased more. Failure to endure increased +Gz and the effects of de-training were primarily due to the inability to regulate MAP. DISCUSSION The incremental increase in increased +Gz from 1 to 3 resulted in increased MAP, which was accomplished by increasing TPR sufficiently so as to offset the reduced CO. The effects of increased +Gz and reduced CO compromised lung function and oxygen transport (-18-30%), thus compromising exercise capacity. The failure to regulate MAP at lower increased +Gz levels resulted in intolerance to higher increased +Gz.

Hypoxia Due to Shunts in Pig Lung Treated with O2 and Fluorocarbon-derived Intravascular Microbubbles

Abstract: Rationale: Earlier work has shown that experimental conditions calling for improved tissue oxygenation could be assisted by i.v. infusion of a dodecafluoropentane emulsion (DDFPe) forming oxygen-transporting microbubbles. Objectives: The present work investigated the effect of DDFPe on hypoxia due to experimental shunts in the pig lung. Methods: Nineteen O2 breathing, anesthetized pigs had glass beads administered into the trachea so as to significantly depress arterial oxygen tension (PaO2). PaO2 was recorded for up to 12 hrs while 0.1 ml/kg DDFPe was administered 1–3 times. Main Results: The animals were divided into two groups based on arterial oxygen saturation (SaO2) after shunt induction, combined with oxygen breathing: the “SaO2 >90% group” (n=6) and the “SaO2 <90% group” (n=13). In the “SaO2 <90% group,” the PaO2 increased stepwise with each infusion from 56.6±2.9 to 88.6±14.6 mmHG (P≤0.001); improvements lasted about 2 hrs after each infusion. Mixed venous oxygenation also increased with the infusions, e.g. (1st infusion) from a PvO2 of 41.4±2.3 to 49.9±4.2 mmHg (P≤0.05) and SvO2 58.0±2.9% (P≤0.01), the venous changes supporting arterial oxygenation. At the same time, arterial CO2 levels fell. Arterial O2 and CO2 levels were paralleled by similar changes in muscle tissue. Pulmonary arterial pressures did not indicate any pulmonary embolization by bubbles. Toxic effects of the treatment were not observed. Conclusion: These results suggest that, on condition of successful toxicity testing, intravascular administration of a DDFPe and oxygen breathing may be beneficial in severe right-to-left shunting in humans.