Continuous Positive Airway Pressure Modulates Effect of Inhaled Nitric Oxide on the Ventilation-Perfusion Distributions in Canine Lung Injury: Data Analysis

Continuous Positive Airway Pressure Modulates Effect of Inhaled Nitric Oxide on the Ventilation-Perfusion Distributions in Canine Lung Injury: Data AnalysisThe method for estimating the distributions of continuous Va/Q ratios was described by Wagner et al. Six inert gases (sulfur hexafluoride, ethane, cyclopropane, enflurane, diethyl ether, and acetone) were dissolved in lactated Ringer’s solution and infused into a peripheral vein at a constant rate set at 0.05 percent of Ve for at least 40 min. Arterial and mixed venous blood and expired gas samples were collected during stable conditions confirmed by constancy (±5 percent) of Ve, FE02, FECO2, and CO. Expired gas samples were collected with an appropriate time delay from a heated mixing chamber. canadian neighbor pharmacy viagra

Concentrations of the inert gases were measured with a gas chromatograph (HP 5890, Hewlett-Packard, Waltham, Mass) and blood-gas partition coefficients were determined.
Arterial to mixed venous (retention) and mixed expired to mixed venous (excretion) concentration ratios of the inert gases were used to obtain retention-solubility and excretion-solubility relationships. By formal mathematical analysis with enforced smoothing, these relationships were transformed into a 50-com-partmental distribution plot of blood flow and ventilation against Va/Q.’ Intrapulmonary shunt defined as fraction of Qt perfusing essentially nonventilated alveoli (Va/Q <0.005), low Va/Q as fraction of the pulmonary blood flow (Qt) perfusing poorly ventilated lung areas (0.005<Va/Q <0.1), high Va/Q as fraction of Ve ventilating poorly perfused lung areas (10<Va/Q <100), dead space as fraction of Ve ventilating nonperfused lung areas (Va/Q >100), mean Va/Q ratio of perfusion (Q) and ventilation (V), and logarithmic standard deviations of perfusion (logSDQ) and ventilation (logSDv) were derived from the 50-compartment model. Predicted values for РаОг were calculated from the recovered Va/Q distributions as described. The index DISPr-e* was calculated as the root mean square difference of measured retentions and excretions corrected for dead space. It is an overall index of Va/Q heterogeneity with a minimum value of zero (homogeneous lung) and a maximum value of 100 (100 percent shunt, 100 percent dead space).

This entry was posted in Lung injury and tagged acute lung injury, continuous positive airway pressure, Nitric oxide, pulmonary gas exchange, ventilation-perfusion distribution.