Peripheral Inert‐Gas Exchange

Abstract

The sections in this article are: Basic Principles of Peripheral Tissue Exchange Inclusion of Pulmonary Gas Exchange in Tissue Inert‐Gas Uptake and Elimination Comparison of Multicompartment Models With Actual Data Consideration of Tissue‐Blood Diffusion of Inert Gases Diffusional Shunts Intertissue Diffusion Evaluation of Assumptions Application of Inert Gases to Measurement of Organ Perfusion Technique 1: Average Organ Blood Flow by Measurement of Prolonged Inert‐Gas Uptake Technique 2: Blood Flow by Arterial Bolus Injection and Subsequent Tissue Washout Analysis Technique 3: Blood Flow by Arterial Bolus Injection and Measurement of Height‐Area Ratio of Concentration‐Time Curve Technique 4: Local Injection of Tracer and Measurement of Blood Flow by Monitoring Subsequent Removal Evaluation of Methods for Measuring Tissue Perfusion With Inert Gases Summary

Kinetics of absorption atelectasis during anesthesia: a mathematical model

“…Wash-in of gas into the ventilated lung compartment, and equilibration of the vessel-rich compartment with the ventilated lung compartment, is rapid for both N 2 and N 2 O, largely complete within 5 min. The half-life (min) for changes in N 2 in the tissue groups are VRG (1.02), MG (22.7), FG (169), and VPG (113) and for N 2 O are VRG (0.74), MG (26.1), FG (75), and VPG (113) (29). The only major difference between the two gases is in the FG, which receives only 5% of cardiac output.…”

“…The tissue compartment models peripheral inert gas exchange, tissue O 2 extraction, and CO 2 production. It consists of four peripheral tissue subcompartments as described by Wagner (29).…”

“…The tissue compartment consists of four peripheral tissue subcompartments (see Fig. 1): vessel-rich group (VRG), muscle group (MG), fat group (FG), and vessel-poor group (VPG) as described by Wagner (29). Each has its individual blood flow, volume, and solubility for each inert gas.…”

Nitrogen back-diffusion during multiple-breath washout with 100% oxygen

“…The second breath hold was timed later in the washout, near the LCI point. The alveolar N 2 concentration owing to back-diffusion at this point can be estimated from a one-compartment steady-state model of gas exchange [10], considering that the rate of back-diffusion (from the blood to the alveolus) is equal to the rate of N 2 excretion by ventilation. Using estimates of normal adult alveolar ventilation (5 L·min −1 ), and our measured back-diffusion of 0.53 mL·s −1 , the estimated alveolar N 2 concentration is ∼0.6%, which constitutes about 1/3 of the total concentration at the LCI point (by definition, one-40th of 79% or 1.95%).…”