Influence of blood Po2 on the stability of agitated saline contrast

Hyperoxic blood has a small stabilizing effect on agitated saline contrast compared with mixed venous blood, lending support to studies that show the reversal of exercise-induced blood flow through intrapulmonary arteriovenous anastomoses (Q̇IPAVA) with hyperoxia. These data support the possible presence of a local O2-dependent regulatory mechanism within the pulmonary vasculature that may play a role in Q̇IPAVA regulation.

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Intrapulmonary arteriovenous shunts of >15 μm in diameter probably do not contribute to arterial hypoxemia in maximally exercising Thoroughbred horses

Journal of Applied Physiology ◽

10.1152/japplphysiol.01230.2004 ◽

2005 ◽

Vol 99 (1) ◽

pp. 224-229 ◽

Cited By ~ 12

Author(s):

Murli Manohar ◽

Thomas E. Goetz

Keyword(s):

Maximal Exercise ◽

Venous Blood ◽

Blood Oxygenation ◽

Mixed Venous Blood ◽

Arteriovenous Shunting ◽

Arterial Hypoxemia ◽

Thoroughbred Horses ◽

Arteriovenous Shunts ◽

Exercise Induced ◽

Mixed Venous

The present study examined whether Thoroughbred horses performing strenuous exercise exhibit intrapulmonary arteriovenous shunting that may contribute to the observed arterial hypoxemia. Experiments were carried out on seven healthy, exercise-trained Thoroughbreds at rest, maximal exercise (galloping at 14 m/s on a 3.5% uphill grade for 120 s), and submaximal exertion (8 m/s on a 3.5% uphill grade for 150 s). Along with blood gas/hemodynamic parameters, intrapulmonary arteriovenous shunting was studied by injecting 15-μm-diameter microspheres, labeled with different stable isotopes, into the right atrium while simultaneous blood samples were being withdrawn at a constant rate from the pulmonary artery and the aorta. Arterial hypoxemia was observed only during maximal exercise. Also, despite significant pulmonary arterial hypertension during submaximal and maximal exertion, 15-μm microspheres did not traverse the pulmonary microcirculation to appear in the aortic blood. Thus our findings did not support a role for intrapulmonary arteriovenous shunts of >15 μm in diameter in the exercise-induced arterial hypoxemia in racehorses. Interestingly, our observation that, in going from 30 to 120 s of maximal exertion, arterial O2 tension had remained unchanged despite significant reductions in mixed venous blood O2 tension, hemoglobin-O2 saturation, and O2 content also discounts the importance of intrapulmonary arteriovenous shunts in causing arterial hypoxemia. This is because, assuming that a constant fraction of total pulmonary blood flow bypasses the gas-exchange areas of the equine lungs via intrapulmonary arteriovenous shunts during 30–120 s of maximal exertion, the observed significant reductions in mixed venous blood oxygenation should cause a significant reduction in arterial O2 tension, which was not the case in our horses. Thus it is suggested that intrapulmonary arteriovenous shunting probably does not contribute to the exercise-induced arterial hypoxemia in racehorses.

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NaHCO3 does not affect arterial O2 tension but attenuates desaturation of hemoglobin in maximally exercising Thoroughbreds

Journal of Applied Physiology ◽

10.1152/japplphysiol.01083.2003 ◽

2004 ◽

Vol 96 (4) ◽

pp. 1349-1356 ◽

Cited By ~ 14

Author(s):

Murli Manohar ◽

Thomas E. Goetz ◽

Aslam S. Hassan

Keyword(s):

Maximal Exercise ◽

Venous Blood ◽

Pulmonary Hemorrhage ◽

Physiological Saline ◽

Mixed Venous Blood ◽

Maximal Heart Rate ◽

Arterial Hypoxemia ◽

Arterial Blood ◽

Exercise Induced ◽

Mixed Venous

The objective of the present study was to examine the effects of preexercise NaHCO3 administration to induce metabolic alkalosis on the arterial oxygenation in racehorses performing maximal exercise. Two sets of experiments, intravenous physiological saline and NaHCO3 (250 mg/kg iv), were carried out on 13 healthy, sound Thoroughbred horses in random order, 7 days apart. Blood-gas variables were examined at rest and during incremental exercise, leading to 120 s of galloping at 14 m/s on a 3.5% uphill grade, which elicited maximal heart rate and induced pulmonary hemorrhage in all horses in both treatments. NaHCO3 administration caused alkalosis and hemodilution in standing horses, but arterial O2 tension and hemoglobin-O2 saturation were unaffected. Thus NaHCO3 administration caused a reduction in arterial O2 content at rest, although the arterial-to-mixed venous blood O2 content gradient was unaffected. During maximal exercise in both treatments, arterial hypoxemia, desaturation, hypercapnia, acidosis, hyperthermia, and hemoconcentration developed. Although the extent of exercise-induced arterial hypoxemia was similar, there was an attenuation of the desaturation of arterial hemoglobin in the NaHCO3-treated horses, which had higher arterial pH. Despite these observations, the arterial blood O2 content of exercising horses was less in the NaHCO3 experiments because of the hemodilution, and an attenuation of the exercise-induced expansion of the arterial-to-mixed venous blood O2 content gradient was observed. It was concluded that preexercise NaHCO3 administration does not affect the development and/or severity of arterial hypoxemia in Thoroughbreds performing short-term, high-intensity exercise.

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Effect of intrapleural pressure on pulmonary shunt through atelectatic dog lung

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1963.205.6.1187 ◽

1963 ◽

Vol 205 (6) ◽

pp. 1187-1192 ◽

Cited By ~ 14

Author(s):

T. N. Finley ◽

T. R. Hill ◽

J. J. Bonica

Keyword(s):

Blood Flow ◽

Spontaneous Breathing ◽

Pulmonary Blood Flow ◽

Venous Blood ◽

Left Lung ◽

Mixed Venous Blood ◽

Pulmonary Shunt ◽

Intrapleural Pressure ◽

Flow Through ◽

Mixed Venous

During spontaneous breathing of oxygen, the pulmonary shunt through the left lung, made atelectatic by occlusion of its airway, was calculated from the O2 and CO2 tension of the arterial and mixed venous blood. At intrapleural pressure swings of -3 to -12 cm H2O, the relative blood flow through the atelectatic lung was reduced to 21.6% of the pulmonary blood flow (normal 45%). With wider swings of intrapleural pressure, average -7.5 to -24 cm H2O, the relative blood flow through the atelectatic lung increased to 45% of the pulmonary blood flow, probably because resistance to blood flow increased in the overdistended right lung. The pulmonary shunt through atelectatic lung varied directly with the increased negativity of the intrapleural pressure.

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Nasal strips do not affect pulmonary gas exchange, anaerobic metabolism, or EIPH in exercising Thoroughbreds

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.6.2378 ◽

2001 ◽

Vol 90 (6) ◽

pp. 2378-2385 ◽

Cited By ~ 20

Author(s):

Thomas E. Goetz ◽

Murli Manohar ◽

Aslam S. Hassan ◽

Gordon J. Baker

Keyword(s):

Blood Lactate ◽

Anaerobic Metabolism ◽

Maximal Exercise ◽

Venous Blood ◽

Pulmonary Hemorrhage ◽

Mixed Venous Blood ◽

Arterial Hypoxemia ◽

Thoroughbred Horses ◽

Exercise Induced ◽

Mixed Venous

The present study was carried out to examine whether nasal strip application would improve the exercise-induced arterial hypoxemia and hypercapnia, diminish anaerobic metabolism, and modify the incidence of exercise-induced pulmonary hemorrhage (EIPH) in horses. Two sets of experiments, control and nasal strip experiments, were carried out on seven healthy, sound, exercise-trained Thoroughbred horses in random order, 7 days apart. Simultaneous measurements of core temperature, arterial and mixed venous blood gases/pH, and blood lactate and ammonia concentrations were made at rest, during submaximal and near-maximal exercise, and during recovery. In both treatments, whereas submaximal exercise caused hyperventilation, near-maximal exercise induced significant arterial hypoxemia, desaturation of Hb, hypercapnia, and acidosis. However, O2 content increased significantly with exercise in both treatments, while the mixed venous blood O2 content decreased as O2 extraction increased. In both treatments, plasma ammonia and blood lactate concentrations increased significantly with exercise. Statistically significant differences between the control and the nasal strip experiments could not be discerned, however. Also, all horses experienced EIPH in both treatments. Thus our data indicated that application of an external nasal dilator strip neither improved the exercise-induced arterial hypoxemia and hypercapnia nor diminished anaerobic metabolism or the incidence of EIPH in Thoroughbred horses performing strenuous exercise.

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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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