Non-invasive estimation of shunt and ventilation-perfusion mismatch

Abstract

Pulmonary gas exchange can be described equally well using non-invasive data. The simplicity of the non-invasive approach makes the method suitable for large-scale clinical use.

Lung ventilation–perfusion imbalance in pulmonary emphysema: assessment with automated V/Q quotient SPECT

“…The observed finding of heterogeneous high or low V/Q distribution on V/Q quotient SPECT and broadened V/Q distribution on V/Q profile in our patients with emphysema indicates the co-existence of a shunt effect and waste ventilation [3,6,8,9,12,17]. Regional lung V-Q balance in patients with emphysema should be variously impaired according to the degree of alveolar destruction, airway obstruction, increased lung tissue compliance, air trapping, hyperinflation and resultant compression of bronchioles or small vasculatures, collateral ventilation, and hypoxic vasoconstriction associated with ventilation disturbance [4,[15][16][17][18][19].…”

“…The assessment of lung ventilation (V)-perfusion (Q) imbalance in diseased lungs is important, since such imbalance significantly impairs alveolar gas-exchange function [1][2][3][4][5]. V/Q quotient single photon emission computed tomography (SPECT) derived from combined V-Q SPECT study is a useful tool for objective assessment and quantitation of lung V-Q imbalance on cross-sectional lungs [6][7][8][9][10][11][12].…”

Reproduction of inert gas and oxygenation data: a comparison of the MIGET and a simple model of pulmonary gas exchange

“…However, the MIGET has, due to its complexity, not been used routinely in clinical practice. It has been shown that simpler models, such as that presented here, can be identified from routinely available clinical data [9,10] and may therefore be useful in a clinical setting. In evaluating the role of this simpler model it is necessary to compare it against the reference method, this being the MIGET.…”

“…Recently, a simpler model has been presented [8,9]. This represents the lung as four different compartments: anatomical dead space, shunt, and then two gas exchange compartments with different _ V= _ Q ratios.…”

Measuring gas exchange with step changes in inspired oxygen: an analysis of the assumption of oxygen steady state in patients suffering from COPD

“…The model consist of three compartments, where two are ventilated and perfused representing gas exchange in the lungs, and the third representing pulmonary shunt. The equations describe the transport of oxygen at steady state from the ventilator or air into the tissues: (1-4) oxygen flow into the alveoli and blood ( _ VO 2 ) in total and addition from each compartment; (5) total expired oxygen fraction (FetO 2 ); (6, 7) Oxygen partial pressure (PcO 2(1) , PcO 2(2) ) in the compartments; (8) drop in O 2 partial pressure from expired gas to capillary blood; (9) mixed concentration of arterial blood (CaO 2 ); (10)(11)(12)(13)(14) relationship between oxygen partial pressure (PO 2 ), saturation (SO 2 ) and concentration (CO 2 ) in the capillary compartments calculated from the oxygen dissociation curve (ODC) and blood variables; (15)(16) concentration of oxygen in the lung capillary compartments (CcO 2(1) , CcO 2(2) ) combining venous concentration (CvO 2 ) and the increase in oxygen concentration resulting from alveolar equilibration; (17) venous oxygen concentration (CvO 2 ) combining arterial oxygen concentration (CaO 2 ) and the drop in oxygen concentration as a result of consumption in the tissues. f, breathing frequency; _ VA, alveolar ventilation; PB, barometric pressure; PH 2 O, water vapor pressure; ScO 2 , Capillary oxygen saturation; O 2 cap, oxygen capacity; Hb, total hemoglobin; HbMet, methemoglobin; HbCO, carboxyhemoglobin; aO 2 , oxygen equilibrium constant contrast, SpO 2 response to a change in FIO 2 will be delayed by the previously mentioned circulation delay.…”