Letter to the editor: Poor agreement in the calculation of venoarterial PCO2 to arteriovenous O2 content difference ratio using central and mixed venous blood samples in septic patients.

The bias and precision of four different methods for determining O2 saturation (SO2) were evaluated during a study of hypobaric hypoxia conducted with seven male subjects exposed progressively over a 40-day period to simulated altitudes from sea level (760 Torr) to 8,840 m (240 Torr). SO2 of arterial and mixed venous blood samples were measured with the Instrumentation Laboratory 282 CO-oximeter (CO-OX), the Radiometer ABL-300 (ABL), and the Lex-O2-Con-K (LEX). Noninvasive measurements of arterial SO2 were made with a Hewlett-Packard 47201A ear oximeter (EAR-OX). The CO-OX method was used as a secondary standard for comparison with the other methods because it has been validated against the classical Van Slyke method over a wide physiological range (Maas et al., Clin. Chim. Acta 29: 303-309, 1970). The LEX results most closely approximated but consistently underestimated those of the CO-OX: LEX = 0.93 CO-OX -0.86, standard error of the estimate (SEE) = 5.17, r = 0.98, n = 670. The ABL method appeared to combine two linear trends: for SO2 greater than 75%, ABL = 0.84 CO-OX +14.4, SEE = 1.77, r = 0.97, n = 369; less than 75%, ABL = 0.98 CO-OX +5.9, SEE = 4.44, r = 0.97, n = 486. The EAR-OX results were found to approximate those of the CO-OX at SO2 values only greater than 65%: EAR-OX = 1.07 CO-OX -6.12, SEE = 7.71, r = 0.98, n = 326.(ABSTRACT TRUNCATED AT 250 WORDS)

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Effects of cocaine on incremental treadmill exercise in horses

Journal of Applied Physiology ◽

10.1152/jappl.1993.75.6.2727 ◽

1993 ◽

Vol 75 (6) ◽

pp. 2727-2733 ◽

Cited By ~ 10

Author(s):

K. H. McKeever ◽

K. W. Hinchcliff ◽

D. F. Gerken ◽

R. A. Sams

Keyword(s):

Right Ventricular ◽

Blood Lactate ◽

Venous Blood ◽

Lactate Concentration ◽

Blood Lactate Concentration ◽

Ventricular Pressure ◽

Mixed Venous Blood ◽

Work Intensity ◽

Venous Blood Lactate ◽

Mixed Venous

Four mature horses were used to test the effects of two doses (50 and 200 mg) of intravenously administered cocaine on hemodynamics and selected indexes of performance [maximal heart rate (HRmax), treadmill velocity at HRmax, treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l, maximal mixed venous blood lactate concentration, maximal treadmill work intensity, and test duration] measured during an incremental treadmill test. Both doses of cocaine increased HRmax approximately 7% (P < 0.05). Mean arterial pressure was 30 mmHg greater (P < 0.05) during the 4- to 7-m/s steps of the exercise test in the 200-mg trial. Neither dose of cocaine had an effect on the responses to exertion of right atrial pressure, right ventricular pressure, or maximal change in right ventricular pressure over time. Maximal mixed venous blood lactate concentration increased 41% (P < 0.05) with the 50-mg dose and 75% (P < 0.05) with the 200-mg dose during exercise. Administration of cocaine resulted in decreases (P < 0.05) in the treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l from 6.9 +/- 0.5 and 6.8 +/- 0.9 m/s during the control trials to 4.4 +/- 0.1 m/s during the 200-mg cocaine trial. Cocaine did not alter maximal treadmill work intensity (P > 0.05); however, time to exhaustion increased by approximately 92 s (15%; P < 0.05) during the 200-mg trial.(ABSTRACT TRUNCATED AT 250 WORDS)

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Pulmonary diffusion in the dog lung

Journal of Applied Physiology ◽

10.1152/jappl.1962.17.6.885 ◽

1962 ◽

Vol 17 (6) ◽

pp. 885-892 ◽

Cited By ~ 7

Author(s):

Albert H. Niden ◽

Charles Mittman ◽

Benjamin Burrows

Keyword(s):

Carbon Monoxide ◽

Pulmonary Artery ◽

Experimental Animal ◽

Venous Blood ◽

Whole Body ◽

Mixed Venous Blood ◽

Pulmonary Diffusion ◽

Perfused Lung ◽

Pulmonary Arterial ◽

Mixed Venous

Methods have been presented for assessing pulmonary diffusion by the “equilibration technique” in the experimental intact dog and perfused lung while controlling ventilation with a whole body respirator. No significant change in diffusion of carbon monoxide was noted between open and closed chest anesthetized animals, with duration of anesthesia in the intact dog, or with duration of perfusion of the isolated dog's lung. There was no demonstrable difference in diffusion when arterialized blood was used as the perfusate in place of mixed venous blood in the lung perfusions suggesting that within the range studied the Po2, Pco2, and pH of pulmonary artery blood does not directly affect the diffusion of carbon monoxide. Retrograde perfusions of dogs' lungs did not significantly alter diffusion, suggesting that pulmonary venous resistance was not significantly lower than pulmonary arterial resistance in the perfused dog lung at the flows and pressures studied. The equilibration technique for measuring pulmonary diffusion and assessing the uniformity of diffusion was well suited to the study of pulmonary diffusing characteristics in the experimental animal. Submitted on January 8, 1962

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An electrical analyzer for carbon dioxide in respiratory gases

Journal of Applied Physiology ◽

10.1152/jappl.1962.17.1.126 ◽

1962 ◽

Vol 17 (1) ◽

pp. 126-130

Author(s):

Leon Bernstein ◽

Chiyoshi Yoshimoto

Keyword(s):

Carbon Dioxide ◽

Thermal Conductivity ◽

Medical Students ◽

Venous Blood ◽

Mixed Venous Blood ◽

The Subject ◽

Respiratory Gases ◽

Rebreathing Method ◽

Mixed Venous

The analyzer described was de signed for measuring the concentration of carbon dioxide in the bag of gas from which the subject rebreathes in the “rebreathing method” for estimating the tension of carbon dioxide in mixed venous blood. Its merits are that it is cheap, robust, simple to construct and to service, easy to operate, and accurate when used by untrained operators. (Medical students, unacquainted with the instrument, and working with written instructions only, obtained at their first attempt results accurate to within ±0.36% [sd] of carbon dioxide.) The instrument is suitable for use by nurse or physician at the bedside, and also for classes in experimental physiology. Some discussion is presented of the theoretical principles underlying the design of analyzers employing thermal conductivity cells. Submitted on July 13, 1961

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Respiratory measurements of cardiac output: from elegant idea to useful test

Journal of Applied Physiology ◽

10.1152/japplphysiol.01074.2001 ◽

2004 ◽

Vol 96 (2) ◽

pp. 428-437 ◽

Cited By ~ 41

Author(s):

Gabriel Laszlo

Keyword(s):

Cardiac Output ◽

Human Subjects ◽

Venous Blood ◽

The Body ◽

Mixed Venous Blood ◽

Indirect Determination ◽

Arterial Blood ◽

Pulmonary Capillary ◽

Pulmonary Arterial ◽

Mixed Venous

The measurement of cardiac output was first proposed by Fick, who published his equation in 1870. Fick's calculation called for the measurement of the contents of oxygen or CO2 in pulmonary arterial and systemic arterial blood. These values could not be determined directly in human subjects until the acceptance of cardiac catheterization as a clinical procedure in 1940. In the meanwhile, several attempts were made to perfect respiratory methods for the indirect determination of blood-gas contents by respiratory techniques that yielded estimates of the mixed venous and pulmonary capillary gas pressures. The immediate uptake of nonresident gases can be used in a similar way to calculate cardiac output, with the added advantage that they are absent from the mixed venous blood. The fact that these procedures are safe and relatively nonintrusive makes them attractive to physiologists, pharmacologists, and sports scientists as well as to clinicians concerned with the physiopathology of the heart and lung. This paper outlines the development of these techniques, with a discussion of some of the ways in which they stimulated research into the transport of gases in the body through the alveolar membrane.

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