A Mathematical Approach for Gas Exchange in the Lungs; Balance Between Ventilation and Perfusion

Electrical impedance tomography measurements of regional ventilation and perfusion applied to etorphine-immobilized white rhinoceroses in lateral recumbency revealed a pronounced disproportional shift of the measured ventilation and perfusion toward the nondependent lung. The dependent lung was minimally ventilated and perfused, but still aerated. Perfusion was found primarily around the hilum of the nondependent lung. These shifts can explain the gas exchange impairments found in this study. Breath holding can redistribute ventilation.

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Excretion-retention diagram to evaluate gas exchange properties of vertebrate respiratory systems

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1982.243.3.r329 ◽

1982 ◽

Vol 243 (3) ◽

pp. R329-R338

Author(s):

A. Zwart ◽

S. C. Luijendijk

Keyword(s):

Gas Exchange ◽

Respiratory System ◽

Visual Inspection ◽

Mathematical Formulation ◽

Mass Conservation ◽

Correct Choice ◽

Model Free ◽

Respiratory Systems ◽

Complex Relationships ◽

Ventilation And Perfusion

Excretion [E = (PE - PI)/(PV - PI)] and retention [R = (Pa - PI)/(PV -PI)]are completely model-free defined variables which describe the dual input-output black-box representation of vertebrate respiratory systems under steady-state conditions. In the excretion-retention diagram (E-R diagram), E is plotted as a function of R. The application of the principle of mass conservation confines the possible combinations of E and R for a gas with a blood-gas partition coefficient, lambda, in a respiratory system with an overall ventilation, VT, and an overall perfusion, QT, to E = (lambda QT/VT) (1 - R). In general, E can be described as a continuous function of R. The mathematical formulation of this function depends on the configuration of the respiratory system. Easily recognizable curvatures are obtained for counter-cross, and cocurrent systems with and without parallel inhomogeneities. Visual inspection of actual E and R data displayed in an E-R diagram therefore allows the correct choice of the configuration of the respiratory system to be eventually used for further parameter estimation schemes. The E-R diagram is also a powerful tutorial tool for visualizing the complex relationships between the gas exchange of agents with different physical properties and the consequences of changes in ventilation and perfusion distribution within the respiratory system on gas transport.

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Ventilation‐perfusion ratio: A Mathematical Approach for Gas Exchange in the Lungs

The FASEB Journal ◽

10.1096/fasebj.2019.33.1_supplement.600.9 ◽

2019 ◽

Vol 33 (S1) ◽

Author(s):

Alejandro Pizano ◽

Paola Calvacci ◽

Felipe Giron ◽

Juan Cordovez

Keyword(s):

Gas Exchange ◽

Mathematical Approach ◽

Ventilation Perfusion Ratio

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Disruption of Diffusion

10.1093/med/9780190226459.003.0020 ◽

2017 ◽

Author(s):

Nayema Khan ◽

John Pawlowski

Keyword(s):

Gas Exchange ◽

Pulmonary Edema ◽

Pulmonary Complications ◽

Alveolar Space ◽

Disease States ◽

Pulmonary Capillary ◽

Air Space ◽

And Diffusion ◽

Pulmonary Status ◽

Ventilation And Perfusion

Adequate gas exchange in the lungs requires a balance between three key processes: ventilation (V), the flow of gas from the environment to the alveoli; perfusion (Q), the circulation to the pulmonary capillary beds; and diffusion of the gas from the alveolar space into the alveolar capillaries. This chapter discusses the management of diseases of the air space, which include secretions, pneumonia, pulmonary edema, and hemoptysis. Collectively these conditions result in the build-up of fluid in the alveolar space and thickening of the alveolar membrane, leading to a mismatch in ventilation and perfusion (V/Q mismatch). Both anesthesia and disease states can adversely affect gas exchange and the chapter discusses strategies to maximize a patient’s pulmonary status in order to minimize perioperative pulmonary complications.

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Endotoxemia increases relative perfusion to dorsal-caudal lung regions

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.4.1508 ◽

2001 ◽

Vol 90 (4) ◽

pp. 1508-1515 ◽

Cited By ~ 7

Author(s):

Anthony J. Gerbino ◽

William A. Altemeier ◽

Carmel Schimmel ◽

Robb W. Glenny

Keyword(s):

Spatial Distribution ◽

Acute Lung Injury ◽

Gas Exchange ◽

Lung Injury ◽

Vascular Response ◽

Regional Ventilation ◽

Fluorescent Microspheres ◽

Mechanically Ventilated ◽

Ventilation And Perfusion ◽

Time Point

Changes in the spatial distribution of perfusion during acute lung injury and their impact on gas exchange are poorly understood. We tested whether endotoxemia caused topographical differences in perfusion and whether these differences caused meaningful changes in regional ventilation-to-perfusion ratios and gas exchange. Regional ventilation and perfusion were measured in anesthetized, mechanically ventilated pigs in the prone position before and during endotoxemia with the use of aerosolized and intravenous fluorescent microspheres. On average, relative perfusion halved in ventral and cranial lung regions, doubled in caudal lung regions, and increased 1.5-fold in dorsal lung regions during endotoxemia. In contrast, there were no topographical differences in perfusion before endotoxemia and no topographical differences in ventilation at any time point. Consequently, endotoxemia increased regional ventilation-to-perfusion ratios in the caudal-to-cranial and dorsal-to-ventral directions, resulting in end-capillary Po 2 values that were significantly lower in dorsal-caudal than ventral-cranial regions. We conclude that there are topographical differences in the pulmonary vascular response to endotoxin that may have important consequences for gas exchange in acute lung injury.

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Spatial distribution of ventilation and perfusion in anesthetized dogs in lateral postures

Journal of Applied Physiology ◽

10.1152/japplphysiol.00377.2001 ◽

2002 ◽

Vol 92 (2) ◽

pp. 745-762 ◽

Cited By ~ 37

Author(s):

Hung Chang ◽

Stephen J. Lai-Fook ◽

Karen B. Domino ◽

Carmel Schimmel ◽

Jack Hildebrandt ◽

...

Keyword(s):

Blood Flow ◽

Gas Exchange ◽

Regional Blood Flow ◽

Linear Regression Analysis ◽

Regional Distribution ◽

Left Lung ◽

Vertical Gradient ◽

Fluorescent Microspheres ◽

Lateral Decubitus ◽

Ventilation And Perfusion

We aimed to assess the influence of lateral decubitus postures and positive end-expiratory pressure (PEEP) on the regional distribution of ventilation and perfusion. We measured regional ventilation (V˙a) and regional blood flow (Q˙) in six anesthetized, mechanically ventilated dogs in the left (LLD) and right lateral decubitus (RLD) postures with and without 10 cmH2O PEEP. Q˙ was measured by use of intravenously injected 15-μm fluorescent microspheres, and V˙a was measured by aerosolized 1-μm fluorescent microspheres. Fluorescence was analyzed in lung pieces ∼1.7 cm3 in volume. Multiple linear regression analysis was used to evaluate three-dimensional spatial gradients ofQ˙, V˙a, the ratio V˙a/Q˙, and regional Po 2 (PrO2 ) in both lungs. In the LLD posture, a gravity-dependent vertical gradient in Q˙ was observed in both lungs in conjunction with a reduced blood flow and PrO2 to the dependent left lung. Change from the LLD to the RLD or 10 cmH2O PEEP increased localV˙a/Q˙ and PrO2 in the left lung and minimized any role of hypoxia. The greatest reduction in individual lung volume occurred to the left lung in the LLD posture. We conclude that lung distortion caused by the weight of the heart and abdomen is greater in the LLD posture and influences both Q˙ andV˙a, and ultimately gas exchange. In this respect, the smaller left lung was the most susceptible to impaired gas exchange in the LLD posture.

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Physiological evaluation of a new quantitative SPECT method measuring regional ventilation and perfusion

Journal of Applied Physiology ◽

10.1152/japplphysiol.00092.2003 ◽

2004 ◽

Vol 96 (3) ◽

pp. 1127-1136 ◽

Cited By ~ 55

Author(s):

Johan Petersson ◽

Alejandro Sánchez-Crespo ◽

Malin Rohdin ◽

Stéphanie Montmerle ◽

Sven Nyrén ◽

...

Keyword(s):

Gas Exchange ◽

Single Photon ◽

Photon Emission ◽

Inert Gas ◽

Emission Computed Tomography ◽

Regional Ventilation ◽

Quantitative Spect ◽

Respiratory Gases ◽

Photon Emission Computed Tomography ◽

Ventilation And Perfusion

We have developed a new quantitative single-photon-emission computed tomography (SPECT) method that uses 113mIn-labeled albumin macroaggregates and Technegas (99mTc) to estimate the distributions of regional ventilation and perfusion for the whole lung. The multiple inert-gas elimination technique (MIGET) and whole lung respiratory gas exchange were used as physiological evaluations of the SPECT method. Regional ventilation and perfusion were estimated by SPECT in nine healthy volunteers during awake, spontaneous breathing. Radiotracers were administered with subjects sitting upright, and SPECT images were acquired with subjects supine. Whole lung gas exchange of MIGET gases and arterial Po2 and Pco2 gases was predicted from estimates of regional ventilation and perfusion. We found a good agreement between measured and SPECT-predicted exchange of MIGET and respiratory gases. Correlations ( r2) between SPECT-predicted and measured inert-gas excretions and retentions were 0.99. The method offers a new tool for measuring regional ventilation and perfusion in humans.

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Ventilasi dan Perfusi, serta Hubungan antara Ventilasi dan Perfusi

Jurnal Respirasi ◽

10.20473/jr.v2-i.1.2016.29-34 ◽

2019 ◽

Vol 2 (1) ◽

pp. 29

Author(s):

Afrita Amalia Laitupa ◽

Muhammad Amin

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Gas Exchange ◽

Oxygen Absorption ◽

Critical Determinant ◽

Lung Diffusion ◽

Diffusion Capacity ◽

Blood Flows ◽

Functional Factors ◽

Ventilation And Perfusion

Lung is a place for gas exchange where ventilation and perfusion occurs. Ventilation is the first step where sequential process of inhalation and exhalation take place. Meanwhile perfusion as the other step facilitates the gas exchange and tissue supply need. Blood flows through the lungs are equals as the amount of cardiac output where the factors that control cardiac output are mainly peripheral factors, also control pulmonary blood flow. In general condition, pulmonary blood vessels act as a passive tube, which can be increased with the increasing pressure and narrowed the pressure drop. Oxygen absorption level from lungs into bloodstream is a critical determinant for functional capacity, and an important factor wheter in normal conditions (including exercise) or even in illness state. Lung diffusion capacity is influenced by several geometric and functional factors. Gravitation influence systematic gradient in ventilation and perfusion distribution. Ventilation and blood flow variations at horizontal level also occur due to intrinsic anatomic variations and vascular geometry, as well as the differences in airway and vascular smooth muscle response which modifies the distribution. The change of integrity intrapleural chamber, hydrostatic pressure and osmotic imbalance, malfunction of surfactants, other intrinsic weakness of the branching system in the form of a progressive airway, and all the things that could potentially damage the structure of the lung can cause ventilation and diffusion dysfunction.

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Sporadic coordinated shifts of regional ventilation and perfusion in juvenile pigs with normal gas exchange

The Journal of Physiology ◽

10.1113/jphysiol.2007.136358 ◽

2007 ◽

Vol 583 (2) ◽

pp. 743-752 ◽

Cited By ~ 7

Author(s):

H. Thomas Robertson ◽

Blazej Neradilek ◽

Nayak L. Polissar ◽

Robb W. Glenny

Keyword(s):

Gas Exchange ◽

Regional Ventilation ◽

Ventilation And Perfusion

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Gas exchange during separate diaphragm and intercostal muscle breathing

Journal of Applied Physiology ◽

10.1152/japplphysiol.00628.2003 ◽

2004 ◽

Vol 96 (6) ◽

pp. 2120-2124 ◽

Cited By ~ 17

Author(s):

A. F. DiMarco ◽

A. F. Connors ◽

K. E. Kowalski

Keyword(s):

Gas Exchange ◽

Muscle Contraction ◽

Muscle Activation ◽

Arterial Oxygen ◽

Intercostal Muscle ◽

Rib Cage ◽

Diaphragm Paralysis ◽

Anesthetized Dogs ◽

Spinal Cord Level ◽

Ventilation And Perfusion

In patients with diaphragm paralysis, ventilation to the basal lung zones is reduced, whereas in patients with paralysis of the rib cage muscles, ventilation to the upper lung zones in reduced. Inspiration produced by either rib cage muscle or diaphragm contraction alone, therefore, may result in mismatching of ventilation and perfusion and in gas-exchange impairment. To test this hypothesis, we assessed gas exchange in 11 anesthetized dogs during ventilation produced by either diaphragm or intercostal muscle contraction alone. Diaphragm activation was achieved by phrenic nerve stimulation. Intercostal muscle activation was accomplished by electrical stimulation by using electrodes positioned epidurally at the T2 spinal cord level. Stimulation parameters were adjusted to provide a constant tidal volume and inspiratory flow rate. During diaphragm (D) and intercostal muscle breathing (IC), mean arterial Po2 was 97.1 ± 2.1 and 88.1 ± 2.7 Torr, respectively ( P < 0.01). Arterial Pco2 was lower during D than during IC (32.6 ± 1.4 and 36.6 ± 1.8 Torr, respectively; P < 0.05). During IC, oxygen consumption was also higher than that during D (0.13 ± 0.01 and 0.09 ± 0.01 l/min, respectively; P < 0.05). The alveolar-arterial oxygen difference was 11.3 ± 1.9 and 7.7 ± 1.0 Torr ( P < 0.01) during IC and D, respectively. These results indicate that diaphragm breathing is significantly more efficient than intercostal muscle breathing. However, despite marked differences in the pattern of inspiratory muscle contraction, the distribution of ventilation remains well matched to pulmonary perfusion resulting in preservation of normal gas exchange.

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