Article Text

other Versions

PDF
A simplified method for deriving shunt and reduced VA/Q in infants
  1. Lawrence Rowe (lawrence{at}keswickcottage.com)
  1. Norfolk and Norwich, University Hospital, United Kingdom
    1. John Gareth Jones (johngareth423{at}btinternet.com)
    1. University of Cambridge, United Kingdom
      1. David Quine
      1. Royal Infirmary of Edinburgh, United Kingdom
        1. Shetty S Bushan
        1. Royal Infirmary of Edinburgh, United Kingdom
          1. Benjamin J Stenson
          1. Royal Infirmary of Edinburgh, United Kingdom

            Abstract

            Background: Right to left shunt and reduced ventilation to well perfused alveoli (VA/Q) have quite different effects on the curve relating inspired oxygen (PIO2) to oxygen saturation (SpO2) and can be quantified non-invasively from measurements of SpO2 and inspired oxygen pressure (PIO2) using complex models of gas exchange. We developed a simpler and more readily applicable computerised “slide-rule” method of making these measurements.

            Aims: To describe the “slide-rule” method and determine the agreement between measurements derived with this and with the more complex model.

            Methods: Series of PIO2 vs SpO2 data points obtained during 43 studies in 16 preterm infants with bronchopulmonary dysplasia were analysed. % shunt and the degree of right shift (kPa) of the haemoglobin-oxygen dissociation curve (a measure of VA/Q) were determined for each dataset with both analytical methods and the results were compared using the method of Bland and Altman.

            Results: The computer slide rule method produced results for all 43 data sets. The more complex model could calculate results for 40/43 datasets. The mean difference (95% limits of agreement) between the two methods for measurements of shunt were minus 1.7% (minus 6.5 to + 3.5%) and for measurements of right shift were 0.3kPa (minus 2.9 to + 3.6kPa).

            Conclusion: The “slide-rule” method was a reliable technique for deriving shunt and right shift (reduced VA/Q) of the PIO2 vs SpO2 curve when compared with the more complex method. The new method should be widely applicable and should facilitate wider application of these measurements.

            Statistics from Altmetric.com

            Request permissions

            If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.