<i>Arterial Oxygen Saturation vs. Alveolar Oxygen Tension as a Measure of Venous Admixture and Diffusion Difficulty in the Lung</i>

Perkins, J. F.; Adams, William E.; Flores, Adolfo

doi:10.1152/jappl.1956.8.4.455

Cited by 8 publications

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“…Paf -Pat = AP1N2 (+.0 ) + AP2N2 (C Q2) = APCN2 [5] where the various values of APN2 are the excess at time t over the final' value at timef. APCN2 is the mean value of this excess in mixed end-capillary blood.…”

Section: Theorymentioning

confidence: 99%

“…Simpler methods of estimating unevenness of blood flow in relation to ventilation have been suggested. These are based on the rate of rise of arterial oxygen saturation (ear oximeter) during the inhalation of oxygen (4)(5)(6), analysis of gas samples obtained from various lobes of the lungs (7), continuous analysis of a single expiration (8), and the difference between the nitrogen tension of alveolar gas and urine (9,10). These simpler methods do not provide quantitative data on the degree of unevenness of pulmonary blood flow.…”

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The Determination of Uneven Pulmonary Blood Flow From the Arterial Oxygen Tension During Nitrogen Washout

Finley¹

1961

J. Clin. Invest.

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Many tests are available for measuring unevenness of pulmonary ventilation. In recent years tests of unevenness of pulmonary blood flow have been described, which utilize radioactive krypton (1) in patients with emphysema, radioactive oxygen in patients with mitral stenosis (2), and radioactive carbon dioxide in normal subjects (3). These studies provide quantitative data on the degree of unevenness of pulmonary blood flow but require expensive and complicated apparatus and are not easily adapted to clinical pulmonary function testing. Simpler methods of estimating unevenness of blood flow in relation to ventilation have been suggested. These are based on the rate of rise of arterial oxygen saturation (ear oximeter) during the inhalation of oxygen (4-6), analysis of gas samples obtained from various lobes of the lungs (7), continuous analysis of a single expiration (8), and the difference between the nitrogen tension of alveolar gas and urine (9, 10). These simpler methods do not provide quantitative data on the degree of unevenness of pulmonary blood flow.An ingenious graphical method of determining unevenness of perfusion of the lung in patients with chronic pulmonary emphysema has been worked out by Briscoe and co-workers (11). This method utilizes a nitrogen washout and wash-in technique and the arterial saturation (luring air-breathing. Its disadvantage is that other causes of arterial desaturation i.e., shunts and diffusion barriers cause an overestimation of the degree of unevenness of perfusion.In this laboratory we have devised a test which yields quantitative data for the determination of the fractional alveolar ventilation and pulmonary capillary blood flow that go to the well and poorly ventilated regions of the distribution of pulmonary blood flow to these regions and the anatomical shunts. The theory, method and results of these studies in normal subjects and in patients with cardiac and pulmonary disease are presented here. THEORYThe lungs can be divided into a well ventilated region (which need not be homogeneous) and a poorly ventilated region (subscripts 1 and 2, respectively). Arterial blood is a mixture of blood that has passed through these regions or through venous-to-arterial shunts. Its oxygen content (Ca) is related to the blood flows through the capillaries of the various regions (Q1, Q2) and through the shunt (Q8), and to their respective oxygen contents (Cl, C2 and Cv) as follows:Ca QT = C1 Q1 + C2Q2 + CQ9 [1] where Qi + Q2 + Qs = QT, the cardiac output. In this and subsequent formulations we omit, from our otherwise conventional (12) symbolization, the subscript c for capillary and the chemical subscript 02-It follows from Equation 1 that at any time (t) during the N2 washout:[2]Wre assume the following are constant in the later stages of the N2 washout: 1) the magnitude of the various blood flOwS (QI, Q2, Q., QT) relative to each other; 2) the arteriov5eiious 02) content difference (Ca -Cv). When we then 1 727(C. C.,) t -. 0.1.Ql + Q2

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Section: Theorymentioning

confidence: 99%

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confidence: 99%