Gas exchange and its control in non-steady-state systems: the consequences of evolution from water to air breathing in the vertebrates

1988 ◽  
Vol 66 (1) ◽  
pp. 109-123 ◽  
Author(s):  
G. Shelton ◽  
P. C. Croghan
Keyword(s):  
Steady State ◽  
Gas Exchange ◽  
Dynamic Models ◽  
Continuous Process ◽  
Circulatory System ◽  
Lung Ventilation ◽  
Burst Duration ◽  
Air Breathing ◽  
Arterial Blood ◽  
Dissociation Curves

Control of breathing and gas exchange has been extensively investigated in unimodal animals, particularly mammals, in which ventilation is characteristically a regular and continuous process and gas exchange approximates to a steady-state system. Both static and dynamic models have been developed in control-theory analyses. Similar analyses are possible in unimodal fish, though few have been carried out. Control in bimodal animals, such as air-breathing fish and amphibians, is more difficult to understand and model. The evolutionary change from water to air breathing in vertebrates involves not only the adjustment of many control processes but also the development, in the early stages, of non steady states in gas exchangers, blood, and tissues. A simple control-system model, differing from mammalian counterparts in its greater emphasis on storage functions and its intermittently activated controller, is described for two suggested stages in the evolution of air breathing. The first of these stages is air gulping, in which a fixed and rather brief pattern of air breathing is activated by internal signals generated as a result of the inadequacy of the gills to provide sufficient oxygen for tissue metabolism. The second stage is that of burst breathing, in which lung ventilation is both begun and ended by internal signals so that burst duration is variable. The effects of adjusting parameters on variables of evolutionary importance, such as dive duration, burst duration, store renewal, and metabolic rate, can be examined in these two versions of the model. Refinements to incorporate arterial and venous compartments in the circulatory system, the shunting of venous and arterial blood streams in the heart, realistic oxygen dissociation curves, controller inputs from a wider range of sources, and the capacity to respond to some conditions with changes in ventilation rate as well as in burst and dive durations, are being developed. They should make the complex, non-steady-state interactions between gas exchangers, circulating blood, and tissues easier to understand and indicate the likely steps toward the evolution of steady-state systems seen in birds and mammals.

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.

scholarly journals Development of blood pressure and cardiac reflexes in the frog Pseudis paradoxsus

1992 ◽  
Vol 263 (3) ◽  
pp. R602-R608
Author(s):  
W. W. Burggren ◽  
J. E. Bicudo ◽  
M. L. Glass ◽  
A. S. Abe
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Arterial Blood Pressure ◽  
Body Mass ◽  
Mean Arterial Blood Pressure ◽  
Lung Ventilation ◽  
Air Breathing ◽  
Paulo State ◽  
Arterial Blood ◽  
Nearly Continuous

Systemic arterial blood pressure and heart rate (fH) were measured in unanesthetized, unrestrained larvae and adults of the paradoxical frog, Pseudis paradoxus from Sao Paulo State in Brazil. Four developmental groups were used, representing the complete transition from aquatic larvae to primarily air-breathing adults. fH (49-66 beats/min) was not significantly affected by development, whereas mean arterial blood pressure was strongly affected, being lowest in the stage 37-39 larvae (10 mmHg), intermediate in the stage 44-45 larvae (18 mmHg), and highest in the juveniles and adults (31 and 30 mmHg, respectively). Blood pressure was not significantly correlated with body mass, which was greatest in the youngest larvae and smallest in the juveniles. In the youngest larvae studied (stages 37-39), lung ventilation was infrequent, causing a slight decrease in arterial blood pressure but no change in heart rate. Lung ventilation was more frequent in stages 44-45 larvae and nearly continuous in juveniles and adults floating at the surface. Bradycardia during both forced and voluntary diving was observed in almost every advanced larva, juvenile, and adult but in only one of four young larvae. Developmentally related changes in blood pressure were not complete until metamorphosis, whereas diving bradycardia was present at an earlier stage.

scholarly journals Ventilation and gas exchange during treadmill locomotion in the American alligator (Alligator mississippiensis)

2000 ◽  
Vol 203 (11) ◽  
pp. 1671-1678 ◽  
Author(s):  
C.G. Farmer ◽  
D.R. Carrier
Keyword(s):  
Gas Exchange ◽  
Large Volume ◽  
Low Frequency ◽  
Lung Ventilation ◽  
Alligator Mississippiensis ◽  
Air Breathing ◽  
Air Convection ◽  
Exercise Ventilation ◽  
Anatomical Characters ◽  
Treadmill Locomotion

A number of anatomical characters of crocodilians appear to be inconsistent with their lifestyle as sit-and-wait predators. To address this paradoxical association of characters further, we measured lung ventilation and respiratory gas exchange during walking in American alligators (Alligator mississippiensis). During exercise, ventilation consisted of low-frequency, large-volume breaths. The alligators hyperventilated severely during walking with respect to their metabolic demands. Air convection requirements were among the highest and estimates of lung P(CO2) were among the lowest known in air-breathing vertebrates. Air convection requirements dropped immediately with cessation of exercise. These observations indicate that the ventilation of alligators is not limited by their locomotor movements. We suggest that the highly specialized ventilatory system of modern crocodilians represents a legacy from cursorial ancestors rather than an adaptation to a lifestyle as amphibious sit-and-wait predators.

Cardiovascular responses to diving and involuntary submergence in the rhinoceros auklet (Cerorhinca monocerata Pallas)

1992 ◽  
Vol 70 (12) ◽  
pp. 2303-2310 ◽  
Author(s):  
Richard Stephenson ◽  
Michael S. Hedrick ◽  
David R. Jones
Keyword(s):  
Steady State ◽  
Lung Ventilation ◽  
Cardiovascular Responses ◽  
Arterial Blood ◽  
Cerorhinca Monocerata ◽  
Arterial Blood Oxygen ◽  
Lactate Levels ◽  
Progressive Accumulation ◽  
Physiological Research ◽  
Rhinoceros Auklet

Cardiovascular responses during diving behaviour were recorded via a cannulated carotid artery in five rhinoceros auklets. Heart rate and mean arterial blood pressure were unchanged from predive values during both escape and feeding dives. The responses to feeding dives and escape dives did not differ. Acidosis, accompanying elevated steady-state plasma lactate levels during escape diving activity, was partially compensated by lung ventilation between dives. The absence of progressive accumulation of lactate in the blood implies that an aerobic steady state was attained, despite the short intervals between dives (2.4 ± 0.4 s). Arterial blood oxygen tension was maintained at reduced levels (50–60 mmHg; 1 mmHg = 133.322 Pa) for up to 32 min of continuous escape diving activity. Immersion of restrained auklets or capture of diving auklets in a net provoked a rapid and intense bradycardia. Growth of hand-reared auklet nestlings peaked at a time corresponding to the natural fledging age for this species but the urge to leave the nest box was not triggered by reduced food availability, as has been suggested for wild semi-precocial alcids. Potential pitfalls in the maintenance and use of alcids in physiological research are discussed.

Control of arrhythmic breathing in bimodal breathers: Amphibia

1988 ◽  
Vol 66 (1) ◽  
pp. 6-19 ◽  
Author(s):  
Robert G. Boutilier
Keyword(s):  
Control System ◽  
Gas Exchange ◽  
Lung Ventilation ◽  
Breath Holding ◽  
Breath Hold ◽  
Breathing Patterns ◽  
Gas Exchanges ◽  
Air Breathing ◽  
Activity State ◽  
Breath Pattern

Amphibians employ a system of gas exchange whereby various combinations of the lungs, gills, and skin are used to exploit gas exchanges in both air and water (bimodal breathing). Continuous lung ventilation is rarely observed in these animals. Instead, the dominant breath pattern is arrhythmic in nature and is believed to have evolved in response to a periodic need to supplement aquatic gas exchange. Such a need is largely dependent on the activity state of the animal concerned and its capacity for aquatic gas exchange. The overall control system appears to be one that turns lung ventilation on and off by trigger signals arising from chemo- and mechano-sensitive receptors responding to changing conditions during periods of breath holding and breathing. In amphibians in which the aquatic exchanger is a major avenue for CO2 elimination, [Formula: see text] levels in the lungs and blood do not change substantially in the latter stages of a breath hold. Under these conditions falling levels of oxygen may be the primary stimulus to terminate the breath hold and initiate breathing. There is, however, some interaction between the two gases since elevated CO2 levels affect the sensitivity of the predominantly O2-mediated response. Another major component in determining air-breathing patterns in these animals is their ability to delay the onset of breathing when certain behavioural activities take precedence over the need for additional gas exchange.

Gas Exchange and Transport During Intermittent Breathing in Chelonian Reptiles

1979 ◽  
Vol 82 (1) ◽  
pp. 75-92 ◽  
Author(s):  
WARREN W. BURGGREN ◽  
GRAHAM SHELTON
Keyword(s):  
Gas Exchange ◽  
Venous Blood ◽  
Lung Ventilation ◽  
Gas Composition ◽  
Blood Gas ◽  
Carbon Dioxide Gas ◽  
Arterial Blood ◽  
Limited Function ◽  
Pulmonary Arterial ◽  
Arteries And Veins

1. The oxygen and carbon dioxide gas tensions in lung gas and blood from the central and peripheral arteries and veins have been measured in unrestrained, undisturbed turtles (Pseudemys scripta) and tortoises (Testudo graecd). 2. Lung and blood gas composition fluctuates widely with intermittent and irregular lung ventilation. The pulmonary gas exchange ratio, which progressively falls during apnoea to as low as 0.2-0.3 in Pseudemys, rises dramatically to over 1.5 during lung ventilation in both species. It is postulated that CO2, which has been passively stored by entering the tissues along gas tension gradients during apnoea, becomes rapidly eliminated into the lungs during ventilation. In diving Pseudemys the lung has only a limited function as a CO2 sink compared to the tissues, but the lung acts as a large oxygen store, which can be drawn upon during apnoea through periodic increases in lung perfusion. 3. Blood gas tensions in the various systemic arches reflect the proximity of the arch's origin to the systemic or pulmonary venous blood streams in the ventricle. Thus, the brachiocephalic artery and right aorta have identical blood gas compositions while the composition of the left aorta is intermediate between these and that in the pulmonary. These relationships are unaffected by normal intermittent breathing. However, this does affect both the origin and composition of systemic and pulmonary arterial blood, such that the greatest proportion of oxygenated blood perfuses the systemic vascular bed during lung ventilation, while the greatest proportion of deoxygenated blood perfuses the lungs during apnoea. 4. These data are discussed in the light of the marked cardiovascular adjustments to intermittent breathing, which occur in chelonian reptiles.

Influence of Bohr-Haldane effect on steady-state gas exchange

1982 ◽  
Vol 52 (5) ◽  
pp. 1330-1337 ◽  
Author(s):  
B. J. Grant
Keyword(s):  
Steady State ◽  
Gas Exchange ◽  
Venous Blood ◽  
Gas Composition ◽  
Blood Gas ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Venous Blood Gas ◽  
Mixed Venous ◽  
Haldane Effect

The influence of the Bohr-Haldane effect (BH) on steady-state gas exchange has previously been described by its effect of gas transfer from the blood when arterial and venous blood gas tensions were held constant. This report quantifies by computer analysis the effects of BH when either or both arterial and venous blood gas tensions are subject to change. When mixed venous blood gas composition is held constant, elimination of BH from a single lung unit typically reduces CO2 output by 6.5% and O2 uptake by 0.5%. Similar effects occur in a two-compartment lung model whether alveolar ventilation-perfusion (VA/Q) mismatch occurs in a parallel or series ventilatory arrangement. When arterial blood gas composition is held constant, elimination of BH increases systemic venous CO2 partial pressure, but O2 partial pressure is hardly affected in the absence of metabolic acidosis. When both mixed venous and arterial blood gas tensions vary and gas exchange is stressed by VA/Q inequality, altitude, anemia, or exercise, elimination of BH predominantly affects mixed venous rather than arterial blood gas tensions. it is concluded that BH may act primarily to reduce tissue acidosis.

scholarly journals d-Cystine di(m)ethyl ester reverses the deleterious effects of morphine on ventilation and arterial blood gas chemistry while promoting antinociception

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benjamin Gaston ◽  
Santhosh M. Baby ◽  
Walter J. May ◽  
Alex P. Young ◽  
Alan Grossfield ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Intracellular Signaling ◽  
Dimethyl Ester ◽  
Diethyl Ester ◽  
Blood Gas ◽  
Negative Effects ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Gas Chemistry ◽  
Ventilatory Drive

AbstractWe have identified thiolesters that reverse the negative effects of opioids on breathing without compromising antinociception. Here we report the effects of d-cystine diethyl ester (d-cystine diEE) or d-cystine dimethyl ester (d-cystine diME) on morphine-induced changes in ventilation, arterial-blood gas chemistry, A-a gradient (index of gas-exchange in the lungs) and antinociception in freely moving rats. Injection of morphine (10 mg/kg, IV) elicited negative effects on breathing (e.g., depression of tidal volume, minute ventilation, peak inspiratory flow, and inspiratory drive). Subsequent injection of d-cystine diEE (500 μmol/kg, IV) elicited an immediate and sustained reversal of these effects of morphine. Injection of morphine (10 mg/kg, IV) also elicited pronounced decreases in arterial blood pH, pO2 and sO2 accompanied by pronounced increases in pCO2 (all indicative of a decrease in ventilatory drive) and A-a gradient (mismatch in ventilation-perfusion in the lungs). These effects of morphine were reversed in an immediate and sustained fashion by d-cystine diME (500 μmol/kg, IV). Finally, the duration of morphine (5 and 10 mg/kg, IV) antinociception was augmented by d-cystine diEE. d-cystine diEE and d-cystine diME may be clinically useful agents that can effectively reverse the negative effects of morphine on breathing and gas-exchange in the lungs while promoting antinociception. Our study suggests that the d-cystine thiolesters are able to differentially modulate the intracellular signaling cascades that mediate morphine-induced ventilatory depression as opposed to those that mediate morphine-induced antinociception and sedation.

scholarly journals Causes, Effects and Methods of Monitoring Gas Exchange Disturbances during Equine General Anaesthesia

Animals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 2049
Author(s):  
Elżbieta Stefanik ◽  
Olga Drewnowska ◽  
Barbara Lisowska ◽  
Bernard Turek
Keyword(s):  
Gas Exchange ◽  
General Anaesthesia ◽  
Near Infrared ◽  
Respiratory Acidosis ◽  
Monitoring Methods ◽  
Arterial Blood Gas ◽  
Complementary Method ◽  
Arterial Blood ◽  
Operative Complications ◽  
Post Operative Complications

Horses, due to their unique anatomy and physiology, are particularly prone to intraoperative cardiopulmonary disorders. In dorsally recumbent horses, chest wall movement is restricted and the lungs are compressed by the abdominal organs, leading to the collapse of the alveoli. This results in hypoventilation, leading to hypercapnia and respiratory acidosis as well as impaired tissue oxygen supply (hypoxia). The most common mechanisms disturbing gas exchange are hypoventilation, atelectasis, ventilation–perfusion (V/Q) mismatch and shunt. Gas exchange disturbances are considered to be an important factor contributing to the high anaesthetic mortality rate and numerous post-anaesthetic side effects. Current monitoring methods, such as a pulse oximetry, capnography, arterial blood gas measurements and spirometry, may not be sufficient by themselves, and only in combination with each other can they provide extensive information about the condition of the patient. A new, promising, complementary method is near-infrared spectroscopy (NIRS). The purpose of this article is to review the negative effect of general anaesthesia on the gas exchange in horses and describe the post-operative complications resulting from it. Understanding the changes that occur during general anaesthesia and the factors that affect them, as well as improving gas monitoring techniques, can improve the post-aesthetic survival rate and minimize post-operative complications.

scholarly journals Accumulation of Prostacyclin in Rat Brain during Haemorrhagic Hypotension—Possible Role of PGI2 in Autoregulation

1984 ◽  
Vol 4 (1) ◽  
pp. 107-109 ◽  
Author(s):  
E. Shohami ◽  
A. Sidi
Keyword(s):  
Blood Pressure ◽  
Steady State ◽  
Control Group ◽  
Prostaglandin E ◽  
Cortical Tissue ◽  
Arterial Blood ◽  
Haemorrhagic Hypotension ◽  
Potent Vasodilator ◽  
Prostaglandin F

The effect of haemorrhagic hypotension on the levels of prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and 6-keto prostaglandin F1α (6-keto-PGF1α) in cortical tissue of rats was studied. Lightly anesthetized rats were subjected to steady-state hypotension for 15 min, with a mean arterial blood pressure of 80, 60, and 40 mm Hg, and compared to a control group of normotensive rats. No significant change was found in the levels of PGE2 and TXB2. The level of 6-keto-PGF1α increased from 7.8 ± 0.9 to 14.1 ± 1.9 pg/mg protein (p < 0.02) at 80 mm Hg. Our findings suggest that prostacyclin, which is a potent vasodilator, might play a role in setting the lower limit of the autoregulation range.

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