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Alveolar Gas Equation

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Ognjen Gajic – One of the best experts on this subject based on the ideXlab platform.

  • Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials.
    Critical Care, 2010
    Co-Authors: Hassan Siddiki, Marija Kojicic, Murat Yilmaz, Taylor Thompson, Rolf D. Hubmayr, Ognjen Gajic

    Abstract:

    Introduction: Dead-space fraction (Vd/Vt) has been shown to be a powerful predictor of mortality in acute lung injury (ALI) patients. The measurement of Vd/Vt is based on the analysis of expired CO2 which is not a part of standard practice thus limiting widespread clinical application of this method. The objective of this study was to determine prognostic value of Vd/Vt estimated from routinely collected pulmonary variables. Methods: Secondary analysis of the original data from two prospective studies of ALI patients. Estimated Vd/Vt was calculated using the rearranged Alveolar Gas Equation: Vd Vt 1 86 CO VE PaCO 2est

  • Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials
    Critical Care, 2010
    Co-Authors: Hassan Siddiki, Marija Kojicic, Murat Yilmaz, Rolf D. Hubmayr, Taylor B Thompson, Ognjen Gajic

    Abstract:

    Introduction Dead-space fraction (Vd/Vt) has been shown to be a powerful predictor of mortality in acute lung injury (ALI) patients. The measurement of Vd/Vt is based on the analysis of expired CO_2 which is not a part of standard practice thus limiting widespread clinical application of this method. The objective of this study was to determine prognostic value of Vd/Vt estimated from routinely collected pulmonary variables. Methods Secondary analysis of the original data from two prospective studies of ALI patients. Estimated Vd/Vt was calculated using the rearranged Alveolar Gas Equation: Vd / Vt = 1 − [ ( 0. 86 × V ˙ CO 2est ) / ( VE × PaCO 2 ) ] where V ˙ CO 2 est is the estimated CO_2 production calculated from the Harris Benedict Equation, minute ventilation (VE) is obtained from the ventilator rate and expired tidal volume and PaCO_2 from arterial Gas analysis. Logistic regression models were created to determine the prognostic value of estimated Vd/Vt. Results One hundred and nine patients in Mayo Clinic validation cohort and 1896 patients in ARDS-net cohort demonstrated an increase in percent mortality for every 10% increase in Vd/Vt in a dose response fashion. After adjustment for non-pulmonary and pulmonary prognostic variables, both day 1 (adjusted odds ratio-OR = 1.07, 95%CI 1.03 to 1.13) and day 3 (OR = 1.12, 95% CI 1.06 to 1.18) estimated dead-space fraction predicted hospital mortality. Conclusions Elevated estimated Vd/Vt predicts mortality in ALI patients in a dose response manner. A modified Alveolar Gas Equation may be of clinical value for a rapid bedside estimation of Vd/Vt, utilizing routinely collected clinical data.

Elisabetta Gallazzi – One of the best experts on this subject based on the ideXlab platform.

  • COMMENTARY Estimation of dead space fraction can be simplified in the acute respiratory distress syndrome
    , 2013
    Co-Authors: Davide Chiumello, Elisabetta Gallazzi

    Abstract:

    Acute lung injury and acute respiratory distress syndrome are characterized by a non-cardiogenic pulmonary edema responsible for a significant impairment of Gas exchange. The pulmonary dead space increase, which is due primarily to an alteration in pulmonary blood flow distribution, is largely responsible for carbon dioxide retention. Previous studies, computing the pulmonary dead space by measuring the expired carbon dioxide and the Enghoff Equation, found that the dead space fraction was significantly higher in the non-survivors; it was even an independent risk of death. The computation of the dead space not by measuring the expired carbon dioxide but by applying a rearranged Alveolar Gas Equation that takes into account only the weight, age, height, and temperature of the patient could lead to widespread clinical diffusion of this measurement at the bedside. In the previous issue of Critical Care, Siddiki and colleagues [1] presented the dead space fraction data collected at admission and on day 3 from two acute lung injury/acute respiratory distress syndrome (ALI/ARDS) databases (109 patients in the Mayo Clinic and 1,896 patients in the ARDS Network). The hospital mortality increased in direct proportion to an increase in the dead space fraction. For every 0.05 increment of the dead space fraction, the odds ratios for hospital mortality were 1.07 at day 1 and 1.12 at day 3. Thus, at first sight, the results of Siddiki and colleagues represent merely a repetition of previous studies [2-4]. However, their study added a novel element in that the dead space fraction was computed more simply than in the previous studies [2-4

  • Estimation of dead space fraction can be simplified in the acute respiratory distress syndrome
    Critical Care, 2010
    Co-Authors: Davide Chiumello, Elisabetta Gallazzi

    Abstract:

    Acute lung injury and acute respiratory distress syndrome are characterized by a non-cardiogenic pulmonary edema responsible for a significant impairment of Gas exchange. The pulmonary dead space increase, which is due primarily to an alteration in pulmonary blood flow distribution, is largely responsible for carbon dioxide retention. Previous studies, computing the pulmonary dead space by measuring the expired carbon dioxide and the Enghoff Equation, found that the dead space fraction was significantly higher in the non-survivors; it was even an independent risk of death. The computation of the dead space not by measuring the expired carbon dioxide but by applying a rearranged Alveolar Gas Equation that takes into account only the weight, age, height, and temperature of the patient could lead to widespread clinical diffusion of this measurement at the bedside.

Hassan Siddiki – One of the best experts on this subject based on the ideXlab platform.

  • Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials.
    Critical Care, 2010
    Co-Authors: Hassan Siddiki, Marija Kojicic, Murat Yilmaz, Taylor Thompson, Rolf D. Hubmayr, Ognjen Gajic

    Abstract:

    Introduction: Dead-space fraction (Vd/Vt) has been shown to be a powerful predictor of mortality in acute lung injury (ALI) patients. The measurement of Vd/Vt is based on the analysis of expired CO2 which is not a part of standard practice thus limiting widespread clinical application of this method. The objective of this study was to determine prognostic value of Vd/Vt estimated from routinely collected pulmonary variables. Methods: Secondary analysis of the original data from two prospective studies of ALI patients. Estimated Vd/Vt was calculated using the rearranged Alveolar Gas Equation: Vd Vt 1 86 CO VE PaCO 2est

  • Bedside quantification of dead-space fraction using routine clinical data in patients with acute lung injury: secondary analysis of two prospective trials
    Critical Care, 2010
    Co-Authors: Hassan Siddiki, Marija Kojicic, Murat Yilmaz, Rolf D. Hubmayr, Taylor B Thompson, Ognjen Gajic

    Abstract:

    Introduction Dead-space fraction (Vd/Vt) has been shown to be a powerful predictor of mortality in acute lung injury (ALI) patients. The measurement of Vd/Vt is based on the analysis of expired CO_2 which is not a part of standard practice thus limiting widespread clinical application of this method. The objective of this study was to determine prognostic value of Vd/Vt estimated from routinely collected pulmonary variables. Methods Secondary analysis of the original data from two prospective studies of ALI patients. Estimated Vd/Vt was calculated using the rearranged Alveolar Gas Equation: Vd / Vt = 1 − [ ( 0. 86 × V ˙ CO 2est ) / ( VE × PaCO 2 ) ] where V ˙ CO 2 est is the estimated CO_2 production calculated from the Harris Benedict Equation, minute ventilation (VE) is obtained from the ventilator rate and expired tidal volume and PaCO_2 from arterial Gas analysis. Logistic regression models were created to determine the prognostic value of estimated Vd/Vt. Results One hundred and nine patients in Mayo Clinic validation cohort and 1896 patients in ARDS-net cohort demonstrated an increase in percent mortality for every 10% increase in Vd/Vt in a dose response fashion. After adjustment for non-pulmonary and pulmonary prognostic variables, both day 1 (adjusted odds ratio-OR = 1.07, 95%CI 1.03 to 1.13) and day 3 (OR = 1.12, 95% CI 1.06 to 1.18) estimated dead-space fraction predicted hospital mortality. Conclusions Elevated estimated Vd/Vt predicts mortality in ALI patients in a dose response manner. A modified Alveolar Gas Equation may be of clinical value for a rapid bedside estimation of Vd/Vt, utilizing routinely collected clinical data.