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A nomogram to obtain pulmonary shuntflow (Qs/Qt)
European Journal of Intensive Care Medicine
|September 1, 1976
Summary
A new nomogram simplifies pulmonary shunt calculation in acute respiratory failure. This tool accurately estimates shunt fraction using key parameters like oxygen saturation and hemoglobin, aiding clinical decisions.
Area of Science:
- Cardiology
- Pulmonary Medicine
- Medical Devices
Background:
- Accurate determination of pulmonary shunt is crucial in managing acute respiratory failure.
- Existing methods for calculating shunt fraction can be complex and time-consuming.
Purpose of the Study:
- To present a simplified nomogram for determining pulmonary shunt.
- To aggregate key factors influencing pulmonary shunt in acute respiratory failure.
Main Methods:
- The nomogram is based on Leigh's et al. shunt-equation (1969).
- It incorporates arterial and venous oxygen saturation, Hb content, arterial oxygen tension, and barometric pressure.
- International mean values are used for less influential factors like vapor pressure and mixed venous oxygen tension.
Main Results:
- The nomogram shows a deviation of less than 1% from calculated shunt values within a specific PCO2 range (32-52 mm Hg).
- Errors do not exceed 1.5% even with higher PCO2 (up to 82 mm Hg) under certain conditions.
- The nomogram effectively illustrates the impact of different parameters on shunt determination.
Conclusions:
- The developed nomogram offers a simplified and accurate method for estimating pulmonary shunt.
- Potential errors in mixed venous saturation and arterial O2 tension measurements are highlighted.
- Recommendations are provided to minimize errors in blood-gas analysis, particularly PO2 determination.