Ventilation and carbon dioxide exchange in exercising horses: effect of inspired oxygen fraction

1995 ◽  
Vol 78 (2) ◽  
pp. 654-662 ◽  
Author(s):  
N. Pelletier ◽  
D. E. Leith
Keyword(s):  
Minute Ventilation ◽  
Venous Blood ◽  
Co2 Production ◽  
Carbon Dioxide Exchange ◽  
Mixed Venous Blood ◽  
O2 Consumption ◽  
Oxygen Fraction ◽  
Thoroughbred Horses ◽  
Flow Through ◽  
Fick Equation

Thoroughbred horses (TB) have no ventilatory response to added CO2 during near-maximal exercise. To see whether that reflects mechanical limits to ventilation or the control of breathing, we examined the effects of varying inspired O2 fraction (0.16, 0.21, or 0.30) in five normal TB standing quietly and galloping at 10 and 14 m/s on a level treadmill. We measured gas exchange (O2 consumption and CO2 production) and ventilation with a flow-through mask system. We also measured PO2, PCO2, and O2 contents in arterial and mixed venous blood and calculated cardiac output by using the Fick equation. Low inspired O2 fraction (0.16 vs. 0.21) had significant effects in TB galloping at 14 m/s. Arterial PO2 then was 38 Torr compared with 56 Torr for horses on air. Tidal volume and minute ventilation were 20% greater than their corresponding values on air, which were 12 liters and 1,475 l/min, respectively, whereas respiratory frequency did not change. O2 consumption and CO2 production were unchanged, but alveolar ventilation was 6% greater, despite increased alveolar and physiological dead spaces, so arterial PCO2 was lower (45 vs. 50 Torr on air). Thus, hypoxia was an effective stimulus to breathing, and minute ventilation was not mechanically limited in TB breathing air at the speeds studied.

Derivation of CO2 output from oscillations in arterial pH

1987 ◽  
Vol 62 (3) ◽  
pp. 880-891 ◽  
Author(s):  
B. A. Cross ◽  
R. P. Stidwill ◽  
K. D. Leaver ◽  
S. J. Semple
Keyword(s):  
Maximum Rate ◽  
Venous Blood ◽  
Co2 Flux ◽  
Limited Range ◽  
Co2 Production ◽  
Mixed Venous Blood ◽  
Co2 Partial Pressure ◽  
Co2 Output ◽  
Arterial Ph ◽  
Small Rise

Theory predicts that the rate of rise of the oscillation in arterial CO2 partial pressure (PaCO2) is linearly dependent on CO2 flux from venous blood to alveolar gas. We have measured, in the anesthetized cat, CO2 output (VCO2) and oscillations in arterial pH. The pH signal was differentiated to give the maximum rate of fall of pH on the downstroke of the oscillation (dpH/dt decreases max). Since oscillations in pH are due to oscillations in arterial PCO2, dpH/dt decreases max was considered to be equivalent to the maximum rate of rise of the PCO2 oscillation. VCO2 was increased by ventilating the intestines with CO2 and by the intra-arterial infusion of 2,4-dinitrophenol. VCO2 was decreased by filling the intestines with isotonic tris(hydroxymethyl)methylamine buffer. The maximum range of VCO2 covered was 7.8–51 ml/min, and the mean range was from 13.6 +/- 1.3 to 29.7 +/- 1.6 (SE) ml/min. Although CO2 loading produced a small rise and CO2 unloading a small fall in mean PaCO2, the changes were not statistically significant, so that overall the response was close to isocapnia. Over the limited range of VCO2 studied there was a highly significant linear association between dpH/dt decreases max and VCO2 which supports the contention that the slope of the upstroke of the PaCO2 oscillation is determined by the CO2 flux from mixed venous blood to alveolar gas. As such this slope is a potential chemical signal linking ventilation to CO2 production.

Effects of glycogen depletion and work load on postexercise O2 consumption and blood lactate

1979 ◽  
Vol 47 (3) ◽  
pp. 514-521 ◽  
Author(s):  
S. S. Segal ◽  
G. A. Brooks
Keyword(s):  
Blood Lactate ◽  
Slow Component ◽  
Minute Ventilation ◽  
Co2 Flux ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Co2 Production ◽  
O2 Consumption ◽  
Glycogen Depletion ◽  
Heavy Exercise

To study a possible relationship between blood lactate and O2 consumption (VO2) after exercise, 11 male subjects exercised on a bicycle ergometer at moderate and heavy work loads in both normal glycogen and glycogen-depleted states. At rest, glycogen depletion resulted in significantly lowered blood glucose and lactate concentrations, CO2 production (VCO2), respiratory exchange ratio (R), and minute ventilation (VE). With the exception of glucose, these variables changed more in response to heavy exercise (HE: 2 min at a mean of 1,750 kg.m/min) than to moderate exercise (ME: 2 min at a mean of 1,000 kg.m/min). At either work load, VCO2, R, and lactate showed consistently greater responses in the normal glycogen state. The slope of the initial component of the postexercise VO2 curve was unaffected by either work load or lactate. Although the slope of the slow component of the postexercise VO2 curve became significantly more negative after HE, it was unaffected by the level of lactate. These results are inconsistent with the hypothesis of a “lactacid O2 debt.” Exercise intensity was the predominant factor influencing the magnitude and kinetics of postexercise VO2. Glycogen depletion resulted in lower VCO2, R, and blood lactate, but higher VE during heavy exercise. The results suggest that factors, in addition to CO2 flux to the lungs, influence VE during exercise.

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

2005 ◽  
Vol 99 (1) ◽  
pp. 224-229 ◽  
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.

scholarly journals Postpneumonectomy alveolar growth does not normalize hemodynamic and mechanical function

1999 ◽  
Vol 87 (2) ◽  
pp. 491-497 ◽  
Author(s):  
Shin-Ichi Takeda ◽  
Murugappan Ramanathan ◽  
Aaron S. Estrera ◽  
Connie C. W. Hsia
Keyword(s):  
Cardiac Output ◽  
Minute Ventilation ◽  
Lung Resection ◽  
Venous Blood ◽  
Structural Response ◽  
Respiratory Muscles ◽  
Blood Gases ◽  
Mixed Venous Blood ◽  
Power Requirement ◽  
Normal Mean

Immature foxhounds underwent 55% lung resection by right pneumonectomy ( n = 5) or thoracotomy without pneumonectomy (Sham, n = 6) at 2 mo of age. Cardiopulmonary function was measured during treadmill exercise on reaching maturity 1 yr later. In pneumonectomized animals compared with Sham animals, maximal oxygen uptake, ventilatory response, and cardiac output during exercise were normal. Arterial and mixed venous blood gases and arteriovenous oxygen extraction during exercise were also normal. Mean pulmonary arterial pressure and resistance were elevated at a given cardiac output. Dynamic ventilatory power requirement was also significantly elevated at a given minute ventilation. These long-term hemodynamic and mechanical abnormalities are in direct contrast to the normal pulmonary gas exchange during exercise in these same pneumonectomized animals reported elsewhere (S. Takeda, C. C. W. Hsia, E. Wagner, M. Ramanathan, A. S. Estrera, and E. R. Weibel. J. Appl. Physiol. 86: 1301–1310, 1999). Functional compensation was superior in animals pneumonectomized as puppies than as adults. These data indicate a limited structural response of conducting airways and extra-alveolar pulmonary blood vessels to pneumonectomy and suggest the development of other sources of adaptation such as those involving the heart and respiratory muscles.

A respiratory venous chemoreceptor in the young puppy

1975 ◽  
Vol 38 (5) ◽  
pp. 819-826 ◽  
Author(s):  
K. R. Kollmeyer ◽  
L. I. Kleinman
Keyword(s):  
Minute Ventilation ◽  
Venous Blood ◽  
Blood Gases ◽  
High Ratio ◽  
Mixed Venous Blood ◽  
Extracorporeal Circuit ◽  
Shunt System ◽  
Newborn Animal ◽  
Venous Circulation ◽  
Arterial Blood

An extracorporeal venovenous shunt system utilizing a membrane oxygenator to alter venous blood gases was used to study the regulation of ventilation in 28 newborn and 4 adult dogs. There was no effect of the extracorporeal circuit per se (without the oxygenator in the system) on essential cardiovascular or respiratory function. When the puppies were placed on the extracorporeal circuit with the oxygenator in the system to effect changes in mixed venous blood gas composition there was a significant increase in venous P02 (Pv02), a decrease in venous Pco2 (Pvco2), a rise in venous pH (PHv), and a marked fall in minute ventilation (VE). There were no significant changes in cardiovascular function or arterial blood gases to account for the depression of ventilation. Acute changes in Pvo2 produced appropriate directional changes of VE under conditions where other arterial and venous blood gases were held constant. At a low Pvco2/Paco2 ratio, ventilation was depressed compared to those conditions with a high ratio. At any Pvc02/Paco2 ratio, ventilation could be depressed by raising the Pvo2. In adult animals ventilation could not be altered by changing venous blood gases. These experiments support the existence of a respiratory chemoreceptor sensitive to both PO2 and PCO2 in the prepulmonary or venous circulation of the newborn animal.

Influence of blood Po2 on the stability of agitated saline contrast

2020 ◽  
Vol 129 (6) ◽  
pp. 1341-1347
Author(s):  
Lindsey M. Boulet ◽  
Tyler D. Vermeulen ◽  
Paul D. Cotton ◽  
Glen E. Foster
Keyword(s):  
Regulatory Mechanism ◽  
Venous Blood ◽  
Pulmonary Vasculature ◽  
Mixed Venous Blood ◽  
Arteriovenous Anastomoses ◽  
Stabilizing Effect ◽  
Flow Through ◽  
Exercise Induced ◽  
The Stability ◽  
Mixed Venous

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.

Measurement and analysis of gas exchange during exercise using a programmable calculator

1980 ◽  
Vol 49 (3) ◽  
pp. 456-461 ◽  
Author(s):  
D. Y. Sue ◽  
J. E. Hansen ◽  
M. Blais ◽  
K. Wasserman
Keyword(s):  
Gas Exchange ◽  
Respiratory Exchange Ratio ◽  
Minute Ventilation ◽  
Co2 Production ◽  
O2 Consumption ◽  
Exercise Tests ◽  
Programmable Calculator ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
End Tidal

Although exercise testing is useful in the diagnosis and management of cardiovascular and pulmonary diseases, a rapid comprehensive method for measurement of ventilation and gas exchange has been limited to expensive complex computer-based systems. We devised a relatively inexpensive, technically simple, and clinically oriented exercise system built around a desktop calculator. This system automatically collects and analyzes data on a breath-by-breath basis. Our calculator system overcomes the potential inaccuracies of gas exchange measurement due to water vapor dilution and mismatching of expired flow and gas concentrations. We found no difference between the calculator-derived minute ventilation, CO2 production, O2 consumption, and respiratory exchange ratio and the values determined from simultaneous mixed expired gas collections in 30 constant-work-rate exercise studies. Both tabular and graphic displays of minute ventilation, CO2 production, O2 consumption, respiratory exchange ratio, heart rate, end-tidal O2 tension, end-tidal CO2 tension, and arterial blood gas value are included for aid in the interpretation of clinical exercise tests.

Effect of metabolic rate on ventilatory roll-off during hypoxia

1994 ◽  
Vol 76 (6) ◽  
pp. 2310-2314 ◽  
Author(s):  
W. M. Gershan ◽  
H. V. Forster ◽  
T. F. Lowry ◽  
M. J. Korducki ◽  
A. L. Forster ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Minute Ventilation ◽  
Face Mask ◽  
Co2 Production ◽  
O2 Consumption ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Series Of Experiments ◽  
Carotid Arterial ◽  
Arterial Po2

This study was done to determine 1) whether goats demonstrate the roll-off phenomenon, i.e., a secondary decrease in minute ventilation (VE), after an initial hyperventilation during various levels of hypoxia and, if so, 2) whether roll-off could be due to changes in metabolic rate. We hypothesized that roll-off occurs in the goat during hypoxia but is not due to hypometabolism. To answer question 1, eight unanesthetized adult goats were exposed to 15–20 min of hypoxia at 0.15, 0.12, and 0.09 inspired O2 fraction (FIO2), resulting in 60, 40, and 30 Torr arterial PO2, respectively. Goats were fitted with a face mask connected to a spirometer to measure VE, and arterial blood gas samples were obtained via carotid arterial catheters. Roll-off was seen with 0.15 and 0.12 FIO2, whereas VE steadily increased with 0.09 FIO2. During hypoxia, arterial PCO2 fell 2, 3, and 7 Torr at 0.15, 0.12, and 0.09 FIO2, respectively. In the second series of experiments, nine different goats were exposed to 30 min of 0.12 FIO2. O2 consumption and CO2 production were measured five times during baseline and hypoxia. VE increased to 32% above baseline values after 2 min of hypoxia and then gradually decreased by 18%. Changes in breathing frequency and tidal volume contributed to the roll-off. O2 consumption decreased (P = 0.0029, analysis of variance) and CO2 production increased (P = 0.0027) during hypoxia, although both changes were small (< 7%) compared with the eventual 18% decrease in VE. We conclude that the adult goat demonstrates the roll-off phenomenon during moderate levels of hypoxia. (ABSTRACT TRUNCATED AT 250 WORDS)

Effect of elastic loading on ventilatory pattern during progressive exercise

1985 ◽  
Vol 59 (1) ◽  
pp. 34-38 ◽  
Author(s):  
A. D. D'Urzo ◽  
K. R. Chapman ◽  
A. S. Rebuck
Keyword(s):  
Minute Ventilation ◽  
Co2 Production ◽  
O2 Consumption ◽  
Mean Values ◽  
Ventilatory Responses ◽  
Elastic Load ◽  
Ventilatory Pattern ◽  
Progressive Exercise ◽  
Elastic Loading ◽  
Fibrotic Lung Disease

Ventilatory responses to progressive exercise, with and without an inspiratory elastic load (14.0 cmH2O/l), were measured in eight healthy subjects. Mean values for unloaded ventilatory responses were 24.41 +/- 1.35 (SE) l/l CO2 and 22.17 +/- 1.07 l/l O2 and for loaded responses were 24.15 +/- 1.93 l/l CO2 and 20.41 +/- 1.66 l/l O2 (P greater than 0.10, loaded vs. unloaded). At levels of exercise up to 80% of maximum O2 consumption (VO2max), minute ventilation (VE) during inspiratory elastic loading was associated with smaller tidal volume (mean change = 0.74 +/- 0.06 ml; P less than 0.05) and higher breathing frequency (mean increase = 10.2 +/- 0.98 breaths/min; P less than 0.05). At levels of exercise greater than 80% of VO2max and at exhaustion, VE was decreased significantly by the elastic load (P less than 0.05). Increases in respiratory rate at these levels of exercise were inadequate to maintain VE at control levels. The reduction in VE at exhaustion was accompanied by significant decreases in O2 consumption and CO2 production. The changes in ventilatory pattern during extrinsic elastic loading support the notion that, in patients with fibrotic lung disease, mechanical factors may play a role in determining ventilatory pattern.

Effect of intrapleural pressure on pulmonary shunt through atelectatic dog lung

1963 ◽  
Vol 205 (6) ◽  
pp. 1187-1192 ◽  
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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