• Br J Anaesth · Mar 2023

    Observational Study

    Ventilatory ratio, dead space, and venous admixture in acute respiratory distress syndrome.

    • Roberta Maj, Paola Palermo, Simone Gattarello, Serena Brusatori, Rosanna D'Albo, Carmelo Zinnato, Mara Velati, Federica Romitti, Mattia Busana, Johannes Wieditz, Peter Herrmann, Onnen Moerer, Micheal Quintel, Konrad Meissner, Barnaby Sanderson, Davide Chiumello, John J Marini, Luigi Camporota, and Luciano Gattinoni.
    • Department of Anaesthesiology, Medical University of Göttingen, University Medical Centre Göttingen, Göttingen, Germany; Department of Anaesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Milan, Italy.
    • Br J Anaesth. 2023 Mar 1; 130 (3): 360367360-367.

    BackgroundVentilatory ratio (VR) has been proposed as an alternative approach to estimate physiological dead space. However, the absolute value of VR, at constant dead space, might be affected by venous admixture and CO2 volume expired per minute (VCO2).MethodsThis was a retrospective, observational study of mechanically ventilated patients with acute respiratory distress syndrome (ARDS) in the UK and Italy. Venous admixture was either directly measured or estimated using the surrogate measure PaO2/FiO2 ratio. VCO2 was estimated through the resting energy expenditure derived from the Harris-Benedict formula.ResultsA total of 641 mechanically ventilated patients with mild (n=65), moderate (n=363), or severe (n=213) ARDS were studied. Venous admixture was measured (n=153 patients) or estimated using the PaO2/FiO2 ratio (n=448). The VR increased exponentially as a function of the dead space, and the absolute values of this relationship were a function of VCO2. At a physiological dead space of 0.6, VR was 1.1, 1.4, and 1.7 in patients with VCO2 equal to 200, 250, and 300, respectively. VR was independently associated with mortality (odds ratio [OR]=2.5; 95% confidence interval [CI], 1.8-3.5), but was not associated when adjusted for VD/VTphys, VCO2, PaO2/FiO2 (ORadj=1.2; 95% CI, 0.7-2.1). These three variables remained independent predictors of ICU mortality (VD/VTphys [ORadj=17.9; 95% CI, 1.8-185; P<0.05]; VCO2 [ORadj=0.99; 95% CI, 0.99-1.00; P<0.001]; and PaO2/FiO2 (ORadj=0.99; 95% CI, 0.99-1.00; P<0.001]).ConclusionsVR is a useful aggregate variable associated with outcome, but variables not associated with ventilation (VCO2 and venous admixture) strongly contribute to the high values of VR seen in patients with severe illness.Copyright © 2022 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

      Pubmed     Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…