scholarly journals The Role of the Gills and Branchiostegites in Gas Exchange in a Bimodally Breathing Crab, Holthuisana Transversa: Evidence for a Facultative Change in the Distribution of the Respiratory Circulation

1984 ◽  
Vol 111 (1) ◽  
pp. 103-121 ◽  
Author(s):  
H. H. TAYLOR ◽  
PETER GREENAWAY
Keyword(s):  
Gas Exchange ◽  
Venous Return ◽  
Venous Blood ◽  
Mixed Venous Blood ◽  
Substantial Fraction ◽  
Air Breathing ◽  
Arterial Circulation ◽  
Circulation Patterns ◽  
Gill Lamellae

The respiratory circulation was investigated in air-breathing and waterbreathing Holthuisana transversa von Martens by analysis of the distribution of radioactive microspheres injected into the haemocoel at seven locations. The gills and putative lungs (branchiostegites and membraneous thoracic walls) both trap approximately 90% of the microspheres entrained in their afferent circulations. The main blood supply to the branchiostegites is from the venous sinuses and constitutes a substantial fraction of the total venous return, which is consistent with earlier inferences, based on morphological information, of their possible involvement in gas exchange. In airbreathing crabs, a mechanism exists which directs a greater proportion of the total venous return via the lungs. From the sinus at the base of walking leg 2, the ratio lung: gill flow was estimated as 86.9: 13.1 ± 5.7% in hydrated crabs that had been air-breathing for more than 1 day, and 19.5:80.5 ± 7.12% in water-breathers. A factor in this circulatory switch may be an increase in branchial resistance in air caused by surface tension of water adherent to the gill lamellae. The direct arterial circulation to the gills represents about 3% of cardiac output and is therefore an insignificant component of the total respiratory circulation. Patterns of microsphere distribution among different gills and different regions of the lung provide information on flow patterns within the thoracic sinus. Neither the thoracic sinus as a whole nor the inf rabranchial sinuses can be considered as reservoirs of truly mixed venous blood in H. transversa.

Influence of G-suit abdominal bladder inflation on gas exchange during +GZ stress

1985 ◽  
Vol 58 (2) ◽  
pp. 506-513
Author(s):  
H. I. Modell ◽  
P. Beeman ◽  
J. Mendenhall
Keyword(s):  
Gas Exchange ◽  
Time Course ◽  
Venous Blood ◽  
Blood Gas Analysis ◽  
Gas Analysis ◽  
Mixed Venous Blood ◽  
Blood Gas ◽  
Series Of Experiments ◽  
Spontaneously Breathing ◽  
Arterial Po2

Available data relating duration of +GZ stress to blood gas exchange status is limited. Furthermore, studies focusing on pulmonary gas exchange during +GZ stress when abdominal restriction is imposed have yielded conflicting results. To examine the time course of blood gas changes occurring during exposure to +GZ stress in dogs and the influence of G-suit abdominal bladder inflation on this time course, seven spontaneously breathing pentobarbital-anesthetized adult mongrel dogs were exposed to 60 s of up to +5 GZ stress with and without G-suit abdominal bladder inflation. Arterial and mixed venous blood were sampled for blood gas analysis during the first and last 20 s of the exposure and at 3 min postexposure. Little change in blood gas status was seen at +3 GZ regardless of G-suit status. However, with G-suit inflation, arterial PO2 fell by a mean of 14.7 Torr during the first 20 s at +4 Gz (P less than 0.01, t test) and 20.6 Torr at +5 GZ (P less than 0.01). It continued to fall an additional 10 Torr during the next 40 s at both +4 and +5 GZ. Arterial PO2 was still 5–10 Torr below control values (P less than 0.05) 3 min postexposure. A second series of experiments paralleling the first focused on blood gas status during repeated exposure to acceleration. Blood gas status was assessed in five dogs during the late 20 s of two 60-s exposures separated by 3 min at 0 GZ. No significant differences between the initial and repeated exposures were detected. The data indicate that G-suit abdominal bladder inflation promotes increased venous admixture.

Analysis of abnormalities of capillary CO2 exchange in vivo

1991 ◽  
Vol 70 (4) ◽  
pp. 1686-1699 ◽  
Author(s):  
A. Bidani
Keyword(s):  
Cardiac Output ◽  
Gas Exchange ◽  
Venous Blood ◽  
Co2 Exchange ◽  
Transport Processes ◽  
Complete Inhibition ◽  
Mixed Venous Blood ◽  
Moderate Exercise ◽  
Significant Chemical

Capillary CO2 exchange in vivo is affected by several interdependent reactions and transport processes. A mathematical model that includes all the significant chemical and transport events that are presumed to occur during capillary gas exchange has been used to investigate the effect of inhibition of 1) erythrocyte HCO(3-)-Cl- exchange, 2) lung carbonic anhydrase (CA) activity with access to plasma, and 3) erythrocyte CA activity on overall pulmonary CO2 excretion (VCO2) during rest and moderate exercise. Any decrement in VCO2 due to inhibition of HCO(3-)-Cl- exchange and/or CA activity, should result in compensatory alterations in cardiac output and/or an increase in the mixed venous blood-to-alveolar PCO2 gradient [(delta PCO2)V-A] to restore steady-state VCO2. Our computations show that complete inhibition of erythrocyte anion exchange would require a compensatory increment in cardiac output of approximately 30-40% or an increase in (delta PCO2)V-A from 6 to 8.3 Torr at rest and from 12 to 15.6 Torr during moderate exercise, if lung CA activity is intact. In the absence of availability of lung CA activity to plasma, the necessary (delta PCO2)V-A is 10.5 Torr at rest and 19.5 Torr during moderate exercise. Complete inhibition of lung and erythrocyte CA activity is predicted to require (delta PCO2)V-A of 39.1 Torr at rest and 74.2 Torr during moderate exercise. These results suggest that HCO(3-)-Cl- exchange might not be vital to maintenance of CO2 transfer and perhaps has a more important role in minimizing the changes in plasma pH associated with microvascular gas exchange in vivo.

Respiratory Function in the South American Lungfish, Lepidosiren Paradoxa (Fitz)

1967 ◽  
Vol 46 (2) ◽  
pp. 205-218
Author(s):  
KJELL JOHANSEN ◽  
CLAUDE LENFANT
Keyword(s):  
Gas Exchange ◽  
Venous Blood ◽  
South American ◽  
O2 Uptake ◽  
The South ◽  
Mechanical Agitation ◽  
Air Breathing ◽  
Arterial Blood ◽  
Dissociation Curves ◽  
Branchial Arteries

1. Respiratory properties of blood and pattern of branchial and pulmonary gas exchange have been studied in twelve specimens of the South American lungfish, Lepidosiren paradoxa (Fitz). 2. Haematocrit ranged from 14 to 19% and blood oxygen capacity from 4.9 to 6.8 vol. %. The blood had a high affinity for O2 with a P50 value of 10.5 mm. Hg at Pco2 6 mm. Hg and temperature 23° C. The Bohr effect was low. 3. The CO2 dissociation curves show a steep ascending slope resulting in a relatively high CO2 combining power at physiological values of blood Pco2 The Haldane effect was small. Buffering capacity of oxygenated whole blood was high and exceeded that in typical water breathers. 4. Air breathing was prominent and intervals between air breaths varied from 3 to 10 min. Branchial respiratory movements were extremely shallow and showed a labile frequency. Air breathing was stimulated by hypoxic and hypercarbic water while hyperoxygenated water had no effect. Branchial respiratory rate showed a marked acceleration in response to mechanical agitation of the water. 5. Gas exchange was predominantly carried out by pulmonary breathing. In less than 10 min. the PO2 of expired gas dropped from 150 mm. Hg to less than 30 mm. Hg. The shallow branchial breathing with very low ventilation values resulted in a low O2 uptake via the gills. 6. Blood-gas analysis documented a clear selective passage of blood through the only partially divided heart. A consistently higher PO2 in dorsal aortic than in pulmonary arterial blood indicates a preferential passage of pulmonary venous blood to the anterior branchial arteries giving rise to most of the systemic circulation while systemic venous blood was largely conveyed to the most posterior branchial arteries giving rise to the pulmonary arteries. 7. The oxygen uptake for fish resting in water with access to air averaged 53.4 ml./hr./kg. Exposure to air lowered the O2 uptake markedly. 8. The increased importance of pulmonary breathing in Lepidosiren is discussed in relation to the transition from water breathing to air breathing.

Oxygen uptake in air and water in the air-breathing reedfish Calamoichthys calabaricus: role of skin, gills and lungs

1982 ◽  
Vol 97 (1) ◽  
pp. 179-186
Author(s):  
R. Sacca ◽  
W. Burggren
Keyword(s):  
Gas Exchange ◽  
Oxygen Uptake ◽  
Natural Environment ◽  
Average Duration ◽  
O2 Uptake ◽  
Total Oxygen ◽  
Air Exposure ◽  
Air Breathing

The reedfish Calamoichthys calabaricus (Smith) is amphibious, making voluntary excursions on to land (in a simulated natural environment) an average of 6 +/− 4 times/day for an average duration of 2.3 +/− 1.3 min. Oxygen uptake is achieved by the gills, skin and large, paired lungs. In water at 27 degrees C, total oxygen uptake is 0.088 ml O2/g.h. The lungs account for 40%, the gills 28%, and the skin 32% of total VO2. Total oxygen uptake during 2 h of air exposure increases from 0.117 ml O2/g.h to 0.286 ml O2/g.h, due largely to an enhanced lung VO2 and a small increase in skin VO2. Calamoichthys is both capable of aerial gas exchange and adapted to maintain O2 uptake during brief terrestrial excursions.

Adrenal component to pulmonary hypertension caused by nicotine administration in the dog

1980 ◽  
Vol 49 (1) ◽  
pp. 66-72 ◽  
Author(s):  
M. B. Maron ◽  
D. A. Rickaby ◽  
C. A. Dawson
Keyword(s):  
Pulmonary Hypertension ◽  
Arterial Pressure ◽  
Left Atrial ◽  
Venous Return ◽  
Venous Blood ◽  
Main Pulmonary Artery ◽  
Mixed Venous Blood ◽  
Lung Lobe ◽  
Nicotine Administration ◽  
Lower Lung

In this study, we investigated the possibility that the adrenal gland contributes to nicotine-induced pulmonary hypertension using a canine left lower lung lobe (LLL) preparation that was pump-perfused with mixed venous blood at constant flow and outflow pressure. Main pulmonary artery, left atrial, and LLL arterial pressures were monitored to assess the responses of the animal's intact right lung and isolated LLL. With the adrenal venous return intact, injection of 10-26 micrograms/kg nicotine into the left ventricle or ascending aorta resulted in a 42% increase in LLL arterial pressure and a 70% increase in the pulmonary arterial-left atrial pressure gradient (Ppa-Pla). When the adrenal venous return was interrupted, the increases in LLL arterial pressure and Ppa-Pla were reduced to 6 and 10%, respectively. The LLL response could be eliminated by alpha-adrenergic receptor blockade, suggesting that adrenal catecholamines may contribute to the pulmonary hypertension induced by nicotine infusion.

Oxygen respiratory gas analysis by sine-wave measurement: a theoretical model

1996 ◽  
Vol 81 (2) ◽  
pp. 985-997 ◽  
Author(s):  
C. E. Hahn
Keyword(s):  
Gas Exchange ◽  
Dead Space ◽  
Venous Blood ◽  
Sine Wave ◽  
Inert Gas ◽  
Mixed Venous Blood ◽  
Arterial Blood ◽  
Partial Pressures ◽  
The Mean ◽  
Mixed Venous

A sinusoidal forcing function inert-gas-exchange model (C. E. W. Hahn, A. M. S. Black, S. A. Barton, and I. Scott. J. Appl. Physiol. 75: 1863–1876, 1993) is modified by replacing the inspired inert gas with oxygen, which then behaves mathematically in the gas phase as if it were an inert gas. A simple perturbation theory is developed that relates the ratios of the amplitudes of the inspired, end-expired, and mixed-expired oxygen sine-wave oscillations to the airways' dead space volume and lung alveolar volume. These relationships are independent of oxygen consumption, the gas-exchange ratio, and the mean fractional inspired (FIO2) and expired oxygen partial pressures. The model also predicts that blood flow shunt fraction (Qs/QT) is directly related to the oxygen sine-wave amplitude perturbations transmitted to end-expired air and arterial and mixed-venous blood through two simple equations. When the mean FIO2 is sufficiently high for arterial hemoglobin to be fully saturated, oxygen behaves mathematically in the blood like a low-solubility inert gas, and the amplitudes of the arterial and end-expired sine-wave perturbations are directly related to Qs/QT. This relationship is independent of the mean arterial and mixed-venous oxygen partial pressures and is also free from mixed-venous perturbation effects at high forcing frequencies. When arterial blood is not fully saturated, the theory predicts that QS/QT is directly related to the ratio of the amplitudes of the induced-saturation sinusoids in arterial and mixed-venous blood. The model therefore predicts that 1) on-line calculation of airway dead space and end-expired lung volume can be made by the addition of an oxygen sine-wave perturbation component to the mean FIO2; and (2) QS/QT can be measured from the resultant oxygen perturbation sine-wave amplitudes in the expired gas and in arterial and mixed-venous blood and is independent of the mean blood oxygen partial pressure and oxyhemoglobin saturation values. These calculations can be updated at the sine-wave forcing period, typically 2–4 min.

Mechanism of pulmonary gas exchange and CO2 transport during breath holding

1959 ◽  
Vol 14 (5) ◽  
pp. 706-710 ◽  
Author(s):  
John C. Mithoefer
Keyword(s):  
Gas Exchange ◽  
Lung Volume ◽  
Venous Blood ◽  
Volume Shrinkage ◽  
Breath Holding ◽  
Mixed Venous Blood ◽  
Co2 Transport ◽  
Arterial Blood ◽  
Mixed Venous ◽  
Haldane Effect

Experiments describe the changes in PaCOCO2 and lung volume shrinkage during breath holding with O2 in man and the PaCOCO2, pH and CO2 content of arterial and mixed venous blood during breath holding in the dog. An explanation is offered for the aberrations in CO2 transport and exchange which occur during apnea. A self-perpetuating cycle is established during breath holding which is initiated by the arrest of the ventilatory output of Co2. The arterial PaCOCo2 rises rapidly as a result of decreased clearance of Co2 from venous blood, the concentrating effect of lung volume shrinkage and the Haldane effect from oxygenation of hemoglobin. The venous PaCOCO2 rises more slowly because of the uptake of Co2 by the tissues and the Haldane effect from reduction of oxyhemoglobin. By this mechanism the Co2 output into the lungs progressively falls and eventually stops. The cycle then is reversed and Co2 moves from lungs to arterial blood. Submitted on March 2, 1959

Effect of local pulmonary blood flow control on gas exchange: theory

1982 ◽  
Vol 53 (5) ◽  
pp. 1100-1109 ◽  
Author(s):  
B. J. Grant
Keyword(s):  
Blood Flow ◽  
Gas Exchange ◽  
Flow Control ◽  
Pulmonary Blood Flow ◽  
Venous Blood ◽  
Pulmonary Gas Exchange ◽  
Mixed Venous Blood ◽  
Regulatory Effect ◽  
Local Ventilation ◽  
Blood Flow Control

The effect of local pulmonary blood flow control by local alveolar O2 tension on steady-state pulmonary gas exchange is analyzed with techniques derived from control theory. In a single homogeneous lung unit with normal inspired and mixed venous blood gas composition, the homeostatic effect on local ventilation-perfusion ratios (VA/Q) regulation occurs over a restricted range of VA/Q. The homeostatic effect is maximal at a moderately low VA/Q (about 0.4) due to the slope of the O2 dissociation curve. In a multicompartment lung with a lognormal distribution of VA/Q, regulation of arterial O2 tension varies with the extent of inhomogeneity. At mild degrees of inhomogeneity where local pulmonary blood flow (Q) control acts predominantly on the lower VA/Q of the Q distribution, the regulatory effect is best. At severe degrees of inhomogeneity where local Q control acts mainly on the higher VA/Q of the Q distribution, the regulatory effect is worse, and positive-feedback behavior may occur. Local Q control has the potential of reducing the deleterious effects of lung disease on pulmonary gas exchange particularly when it operates in association with other regulatory mechanisms.

scholarly journals Control of ventilation during exercise in patients with central venous-to-systemic arterial shunts

1988 ◽  
Vol 64 (1) ◽  
pp. 234-242 ◽  
Author(s):  
K. E. Sietsema ◽  
D. M. Cooper ◽  
J. K. Perloff ◽  
J. S. Child ◽  
M. H. Rosove ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Minute Ventilation ◽  
Venous Blood ◽  
Work Rate ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Arterial Circulation ◽  
Arterial Blood ◽  
Constant Work Rate ◽  
End Tidal

The diversion of systemic venous blood into the arterial circulation in patients with intracardiac right-to-left shunts represents a pathophysiological condition in which there are alterations in some of the potential stimuli for the exercise hyperpnea. We therefore studied 18 adult patients with congenital (16) or noncongenital (2) right-to-left shunts and a group of normal control subjects during constant work rate and progressive work rate exercise to assess the effects of these alterations on the dynamics of exercise ventilation and gas exchange. Minute ventilation (VE) was significantly higher in the patients than in the controls, both at rest (10.7 +/- 2.4 vs. 7.5 +/- 1.2 l/min, respectively) and during constant-load exercise (24.9 +/- 4.8 vs. 12.7 +/- 2.61 l/min, respectively). When beginning constant work rate exercise from rest, the ventilatory response of the patients followed a pattern that was distinct from that of the normal subjects. At the onset of exercise, the patients' end-tidal PCO2 decreased, end-tidal PO2 increased, and gas exchange ratio increased, indicating that pulmonary blood was hyperventilated relative to the resting state. However, arterial blood gases, in six patients in which they were measured, revealed that despite the large VE response to exercise, arterial pH and PCO2 were not significantly different from resting values when sampled during the first 2 min of moderate-intensity exercise. Arterial PCO2 changed by an average of only 1.4 Torr after 4.5-6 min of exercise. Thus the exercise-induced alveolar and pulmonary capillary hypocapnia was of an appropriate degree to compensate for the shunting of CO2-rich venous blood into the systemic arterial circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood oxygen transport in the free-swimming hagfish, Eptatretus cirrhatus

1986 ◽  
Vol 123 (1) ◽  
pp. 43-53 ◽  
Author(s):  
R. M. Wells ◽  
M. E. Forster ◽  
W. Davison ◽  
H. H. Taylor ◽  
P. S. Davie ◽  
...  
Keyword(s):  
Venous Blood ◽  
Mixed Venous Blood ◽  
Oxygen Binding ◽  
Blood Oxygen ◽  
Binding Data ◽  
Gas Measurements ◽  
Hyperbolic Equilibrium

Arterial and mixed venous blood were sampled through chronically implanted cannulae from rested and swimming hagfish. PaO2 remained high when hagfish were swum for 15 min at a velocity of 20 cm s-1. PvO2 fell from 17.2 mmHg at rest to 3.5 mmHg after swimming, and the arteriovenous pH difference increased from 0.15 to 0.25 pH units. Whole blood oxygen equilibrium curves were essentially hyperbolic (Hill's n value = 1.38) and gave a half-saturation PO2 (P50) value of 12.3 mmHg at pH 7.8 and 16 degrees C. A CO2-Bohr factor (phi = delta logP50/delta pH) of −0.43 and a limited buffering capacity of the blood, amounting to approx. 4 slykes, were observed. The role of the blood in transporting oxygen and carbon dioxide both at rest and after swimming is established by in vivo blood gas measurements and in vitro oxygen-binding data. The low internal PvO2 at rest is close to the P50 measured under similar conditions and the hyperbolic equilibrium curve permits further oxygen unloading when PvO2 falls during swimming.

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