BACKGROUND: Body posture, as a gravitational factor, has a clear impact on pulmonary ventilation and perfusion. In lung units with mismatched ventilation and perfusion, gas exchange and/or elimination of carbon dioxide can be impaired. In this situation, differences in the value of arterial and end-tidal carbon dioxide tension [Delta(PaCO2 - PETCO2)] are expected to increase. This study was conducted to observe how Delta(PaCO2 - PETCO2) changed according to the 3 different surgical positions, and to determine whether Delta(PaCO2 - PETCO2) is a reliable predictor of ventilation/perfusion mismatch when a patient is in different postural positions. METHODS: Fifty-nine patients were divided into either the chronic obstructive pulmonary disease (COPD) group (n = 29) or the non-COPD group (n = 30). PaCO2 and PETCO2 were measured during surgery in the supine, prone, and lateral decubitus positions after a 10 minute stabilization period. The Delta(PaCO2 - PETCO2) were calculated and compared among positions. RESULTS: The Delta(PaCO2 - PETCO2) decreased slightly in the prone position and increased significantly in the lateral decubitus position compared with the supine position in both groups. These patterns almost corresponded with the degree of ventilation/perfusion mismatch from the results of the radiological studies. The Delta(PaCO2 - PETCO2) in the COPD group was significantly greater than that in the non-COPD group at all surgical positions. CONCLUSIONS: Lateral decubitus position is associated with marked increase in Delta(PaCO2 - PETCO2), especially in patients with COPD. The Delta(PaCO2 - PETCO2) is a simple and reliable indicator to predict ventilation/perfusion mismatch at different surgical positions in patients with or without COPD.
Benzeneacetamides ; Carbon ; Carbon Dioxide ; Humans ; Lung ; Perfusion ; Piperidones ; Posture ; Prone Position ; Pulmonary Disease, Chronic Obstructive ; Pulmonary Ventilation ; Supine Position ; Ventilation ; Ventilation-Perfusion Ratio

BACKGROUND: In this study, we performed one-lung ventilation (OLV) in rabbits to assess the effects of OLV on the VA/Q ratio and the respiratory physiological changes using MIGET. METHODS: Ten male New Zealand white rabbits, weighing 3-4 kg were selected. To perform MIGET, six inactive gases (SF6, krypton, desflurane, enflurane, diethyl ether, acetone) in 500 ml normal saline were injected intravenously. During two-lung ventilation (TLV), and after OLV for 30 minutes, blood was sampled for blood gas analysis and MIGET, hemodynamic variables were measured. For MIGET, the concentrations of the injected inert gases were measured and converted to retention/excretion data; the VA/Q distribution curve was obtained using a computer. RESULTS: Systolic, mean, and diastolic pulmonary pressures were elevated significantly and pulmonary resistance was doubled (P<0.05) in OLV compared to TLV. Blood pH decreased in OLV. The calculated intrapulmonary shunt was 19% and 52%, TLV and OLV, respectively. The analysis of VA/Q using MIGET showed that the VA/Q distribution curve was wider and that the VA/Q area was larger in normal rabbits. And, that intrapulmonary shunt approximated to 11%. In the case of OLV, a significant increase in shunt was observed but no change in the amount of dead space at distribution area, (log SDQ, log SDV) remained the same, whereas the VA/Q distribution curve shifted toward the right. CONCLUSIONS: OLV in rabbits showed severe hypercapnia and hypoxemia leading to a considerable increase in shunt. Because of the wide range of VA/Q distribution in TLV, no significant changes in respiratory variables were observed during OLV.
Anoxia ; Blood Gas Analysis ; Enflurane ; Ether ; Gases ; Hemodynamics ; Humans ; Hydrogen-Ion Concentration ; Hypercapnia ; Krypton ; Lung* ; Male ; Noble Gases ; One-Lung Ventilation ; Rabbits ; Ventilation ; Ventilation-Perfusion Ratio*

OBJECTIVEThis study was to assess the reliability of perfusion/ventilation (Q/V) lung scintigraphy in the diagnosis and quantitative analysis of chronic thromboembolic pulmonary hypertension (CTEPH).

METHODSA total of 78 in-patients with pulmonary hypertension who had no history of congenital heart disease, valvular disease and acute pulmonary embolism were included in this study. All patients underwent Q/V scintigraphy for detecting CTEPH. The sensitivity, specificity and accuracy of Q/V scintigraphy were defined by comparing with the results of pulmonary angiography. Percentage of Perfusion Defect score (PPDs%) was calculated in patients with CTEPH confirmed by pulmonary angiography. The correlations between PPDs% and mPAP, PPDs% and SPAP were analyzed.

RESULTSThe sensitivity, specificity and accuracy of a high-probability Q/V scintigraphy interpretation were 96.0%, 81.1% and 86.9%, respectively, compared with 100%, 69.8% and 79.5% for the combination of high- and intermediate- probability Q/V scintigraphy interpretation. PPDs% was significantly correlated with mPAP and SPAP (r = 0.538 for mPAP, P < 0.01 and r = 0.456 for SPAP, P < 0.05).

CONCLUSIONPerfusion/ventilation lung scintigraphy is a valuable technique for diagnosis and quantitative analysis of CTEPH.

Humans ; Hypertension, Pulmonary ; diagnostic imaging ; Lung ; diagnostic imaging ; Pulmonary Embolism ; diagnosis ; diagnostic imaging ; Radionuclide Imaging ; Sensitivity and Specificity ; Ventilation-Perfusion Ratio

BACKGROUND: Endotoxin is a complex lipopolysaccharide molecule situated within the outer membrane of Gram-negative bacteria. Sepsis and acute respiratory failure (ARDS) can be induced by endotoxin. In order to introduce and develop the experimental model of ARDS in sepsis, we induced sepsis with the endotoxin and investigated the change of respiratory pathophysiology during sepsis using a multiple inert gas elimination technique (MIGET). METHODS: Ten New Zealand white rabbits were anesthetized and ventilated with a Harvard apparatus. In 5 rabbits, 2 mg/kg of lipopolysaccaride from E. coli was infused intravenously for 30 min (Toxin group). At 1, 2, 3, and 4 hours after endotoxin infusion, arterial blood gas, and hemodynamic profiles were checked. To perform the MIGET, six inert gases (SF6, krypton, desflurane, enflurane, diethyl ether, acetone) of widely varying solubility were infused peripherally and the excretion and retention data was determined from measurements of inert gas tensions in pulmonary arterial, systemic arterial blood samples and mixd expiratory gas sampling of pre and post septicemia using gas chromatography. We transformed and analysed the data into a V/Q distribution curve to find out the change of V/Q distribution curve. After the experiments, the animals were dissected and the lungs were extracted for wet/dry weight ratio (WW/DW) and microscopic examination. RESULTS: In the Toxin group, the pulmonary arterial pressures were increased and arterial oxygen tensions were decreased after the endotoxin infusion. The lung WW/DW were increased and inflammatory findings were seen in microscopic examination. In the MIGET, shunt, deadspace and log SDQ were increased in the toxin group, though there were wide V/Q distributions in the control group. CONCLUSIONS: We developed a successful endotoxin induced septic animal model, V/Q distribution curve and data using MIGET. The accomplishment of the experiment will not only allow us to better understand pulmonary pathophysiology of endotoxin induced sepsis using MIGET, but it will also contribute to other pulmonary physiology experiments associated with sepsis.
Animals ; Arterial Pressure ; Chromatography, Gas ; Enflurane ; Ether ; Gram-Negative Bacteria ; Hemodynamics ; Krypton ; Lung ; Membranes ; Models, Animal ; Models, Theoretical ; Noble Gases ; Oxygen ; Physiology ; Rabbits ; Respiratory Insufficiency ; Sepsis ; Solubility ; Ventilation-Perfusion Ratio*