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At least 19 recordsLinked to original sources
PubMed1986

Computer simulation of mammalian gas-exchange.

Gas exchange efficiency is dependent upon the distribution of ventilation to perfusion throughout the lung, as well as the position and shape of the oxygen and carbon dioxide dissociation curves, and the composition of mixed venous blood. Computer simulation has allowed practical investigation of these relationships. A BASIC program suitable for small microcomputers is presented which calculates the arterial blood gases and gas transport corresponding to an arbitrary VA/Q distribution and mixed venous composition. The needed theory and equations are developed, the program is discussed, and an example is presented.

Carbon Dioxide↗
PubMed2006

Evidence from mosquitoes suggests that cyclic gas exchange and discontinuous gas exchange are two manifestations of a single respiratory pattern.

In this paper we demonstrate that the apparent pattern of gas exchange in insects, as observed using flow-through respirometry, is strongly affected by the rate of flow of air through the system. This is true not only because of the time constant of the respiratory chamber in which the insect resides, but also due to the effect of flow rate on the residence time of air as it passes through the detection chamber in the gas analyzer. It is demonstrated that insects respiring with a discontinuous gas exchange pattern can appear to be using a cyclic respiratory pattern. The effects of flow rate on the respiratory pattern discerned are illustrated using the mosquito Culiseta inornata. It is demonstrated that these mosquitoes respire discontinuously. They are among the smallest insects to date in which the discontinuous gas exchange cycle has been observed.

Animals↗
PubMed1994

Perfluorocarbon associated gas exchange (PAGE): gas ventilation of the perfluorocarbon filled lung.

BACKGROUND: Throughout most of the second half of this century, progress in respiratory life support was dominated by modernization of the mechanical ventilator. We have now entered an era in which the fundamental physiology of lung function can be manipulated to improve lung performance in hope of reducing morbidity and mortality and thereby decreasing the cost of intensive care. MAIN FINDINGS: Despite its almost alien technology, perfluorocarbon tidal liquid breathing is an effective means to support respiration in normal and surfactant deficient lungs. A second, technique, perfluorocarbon associated gas exchange (PAGE), has recently been shown effective in normal lungs and in several animal models of lung disease. Both techniques appear to improve pulmonary function when pulmonary surface tension is elevated. CONCLUSIONS: PAGE improves lung function and poses opportunities to reduce pulmonary morbidity and diminish the cost of intensive care.

Animals↗
PubMedDate not supplied

[Gas exchange and gas transport in deeply cooled rats during slow and rapid warming using artificial pulmonary ventilation].

Artificial lung ventilation (ALV) was shown to restore the gas exchange in rats following their cooling to brain temperature 17.0-17.6 degrees C. However, the ALV proved ineffective if applied in 22.1 +/- 2.1 min after cessation of breathing. Fast warming up of the animals increased oxygen consumption and carbon dioxide production, and caused a less obvious metabolic acidosis in the rats in the course of recovering from hypothermia.

Animals↗
PubMedDate not supplied

[Central hemodynamics, gas exchange, and gas oxygen-transporting function in combined anesthesia using xenon during operations under extracorporeal circulation].

The advantages of xenon include its good hemodynamic profile and possible cardioprotective properties. The investigation was undertaken to study central hemodynamics, lung gas exchange, and blood oxygen-transporting function in xenon anesthesia in patients operated on under extracorporeal circulation (EC). Fifteen patients aged 41-69 years operated on for coronary heart disease were examined. The severity of the patients' baseline status corresponded to NYHA functional classes I to IV. The duration of an operation was 251 +/- 10 min; that of EC was 97 +/- 5 min; aortic ligation lasted 59 +/- 3 min. After induction of anesthesia with propofol via concentration-regulated infusion (CRI) and with fentanyl, delivery of xenon was initiated at concentrations of 47 +/- 1 to 52.5 +/- 1%, which was mixed with oxygen. Propofol CRI was used during EC. After the latter, xenon was inhaled at concentrations of 47.7 +/- 1 to 53.3 +/- 1%. The mean arterial pressure (BP(mean)), heart rate (HR), and cardiac index (CI) remained unchanged during xenon anesthesia in the preperfusion period. After EC during xenon anesthesia, CI significantly rose with a moderate increase in HR without inotropic support. BP(mean) was moderately, but statistically significantly decreased. Prior to and following EC, there were no changes in the values of blood oxygen-transporting function.

Adult↗
PubMed1994

Analysis of factors affecting gas exchange in intravascular blood gas exchanger.

A mathematical model of an intravascular hollow-fiber gas-exchange device, called IVOX, has been developed using a Krogh cylinder-like approach with a repeating unit structure comprised of a single fiber with gas flowing through its lumen surrounded by a coaxial cylinder of blood flowing in the opposite direction. Species mass balances on O2 and CO2 result in a nonlinear coupled set of convective-diffusion parabolic partial differential equations that are solved numerically using an alternating-direction implicit finite-difference method. Computed results indicated the presence of a large resistance to gas transport on the external (blood) side of the hollow-fiber exchanger. Increasing gas flow through the device favored CO2 removal from but not O2 addition to blood. Increasing blood flow over the device favored both CO2 removal as well as O2 addition. The rate of CO2 removal increased linearly with the transmural PCO2 gradient imposed across the device. The effect of fiber crimping on blood phase mass transfer resistance was evaluated indirectly by varying species blood diffusivity. Computed results indicated that CO2 excretion by IVOX can be significantly enhanced with improved bulk mixing of vena caval blood around the IVOX fibers.

Blood Gas Analysis↗
PubMed1995

Perfusion through vessels open in zone 1 contributes to gas exchange in rabbit lungs in situ.

We previously found that up to 15% of the normal cardiac output can flow through lungs that are entirely in zone 1 and that the zone 1 pathway utilizes alveolar corner vessels. Because of the proximity of these vessels to alveoli, we hypothesized that lungs perfused under zone 1 conditions would exchange gas. We used the multiple inert gas elimination technique to assess the ventilation-perfusion (VA/Q) distribution under zones 1 and 2 in six rabbit lungs perfused with tris(hydroxymethyl)aminomethane-buffered Tyrode solution containing 1% albumin, 4% dextran, and papaverine (25 mg/l). High-frequency oscillation (tidal volume = 2.8 ml at 20 Hz, bias flow = 1 l/min) kept alveolar pressure (PA) nearly constant at 10 or 20 cmH2O. Pulmonary arterial pressure was set 2.5 cmH2O below or 5 cmH2O above PA (zones 1 and 2, respectively). Pulmonary venous pressure was kept at 0 cmH2O, with zero reference being the bottom of the lung. At PA of 10 cmH2O, flow was 64 +/- 40 and 5 +/- 3 ml/min (P < 0.05) and the mean VA/Q for perfusion was 1.1 +/- 0.4 and > 5 (P < 0.05) in zones 2 and 1, respectively. At PA of 20 cmH2O, flow was 89 +/- 36 and 22 +/- 13 ml/min (P < 0.05) and the mean VA/Q for perfusion was 0.8 +/- 0.3 and 3.7 +/- 2.4 (P < 0.05) in zones 2 and 1, respectively. Shunt averaged < 5% of total flow in all conditions. Blood flowing through vessels remaining open under zone 1 conditions 1) exchanges gas, 2) does not occur through anatomic or physiological shunts, and 3) may explain the high VA/Q seen with positive end-expiratory pressure.

Albumins↗
PubMed1976

Gas exchange in air sacs: contribution to respiratory gas exchange in ducks.

Air sac gas exchange was studied in ducks by measuring the rates of inert gas uptake and of O2 and CO2 equilibration in caudal thoracic air sac whose ventilation was prevented by surgival sealing of the ostia. The data were analyzed on a model incorporating three possible routes by which air sac gas could be exchanged with the surrounding tissue: (1) into the blood perfusing the air sac walls; (2) into the adjoining air sac via tissue membranes; (3) into the bronchial system of the lung via diffusion through lung tissue bordering upon the caudal thoracic air sac. Exchange rates of gases via the two latter paths were found to be small as compared with the first route. From application of model parameters to O2 and CO2 exchange in air sacs under physiological conditions the following conclusions were drawn: (1) the caudal thoracic air sac makes the major contribution to total gas exchange between air sacs and blood; (2) this exchange can account for less than 5% of total respiratory gas exchange; (3) the exchange is too small to account for the O2 and CO2 partial pressures in caudal thoracic air sacs of ducks. Other mechanisms like gas exchange in neopulmonic parabronchi, which conduct air to the caudal air sacs during inspiration or re-inspiration of dead space appear to play a more significant role in the deviation of O2 and CO2 partial pressures in the caudal air sacs from those in inspired air.

Air Sacs↗
PubMed1977

Recent advances in pulmonary gas exchange.

Abnormal gas exchange frequently accompanies general anesthesia, and the mechanisms are probably variable and multiple. This chapter has focused on recent advances in both experimental and theoretical approaches to gas exchange in general, with emphasis on the potentially important areas for the anesthesiologist wishing to study gas during anesthesia. Experimentally it is clear that if complex multifactorial mechanisms of abnormal gas exchange are to be described, methods must developed that give significantly more information than is available by standard techniques. Even while such methods are beginning to appear, it is probable that even the most sophisticated of approaches cannot give all of the fine detail one might seek, and that critical evaluation of just what information can be obtained is of great importance. Notwithstanding the practical limitations of such methods, much can be gained by taking advantage of digital computer models of the lung. In only ten years since such models were first introduced, the understanding of complex interactions in pulmonary gas exchange has certainly exceeded the sum of previous knowledge in this area and has allowed clear-cut conclusions of fundamental importance to be reached.

Anesthesia↗
PubMed1999

Intravascular gas exchange.

Intravascular gas exchange, in which miniaturized hollow fibre oxygenators are inserted into the caval veins, has been proposed as a simpler and safer alternative to extracorporeal support in severe respiratory failure. One such device, the IVOX (intravascular oxygenator), has undergone clinical trials (160 implants) and, despite individual benefits, was found to be limited in its gas exchanging capacity. The peculiarities of oxygen physiology render pre-pulmonary oxygenation inefficient and variable, whereas carbon dioxide clearance is much more predictable. Several devices are currently undergoing development and may offer substantially enhanced gas exchange. The new devices, which may be several years from widespread clinical assessment, offer exciting therapeutic options in severe respiratory failure but are unlikely to completely replace extracorporeal techniques in the most severe forms of respiratory failure.

Equipment Design↗