Non-invasive estimation of shunt and ventilation-perfusion mismatch
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To investigate whether parameters describing pulmonary gas exchange (shunt and ventilation-perfusion mismatch) can be estimated consistently by the use of non-invasive data as input to a mathematical model of oxygen transport.
Investigations were carried out in the post-anaesthesia care unit, coronary care unit, and intensive care unit.
Data from ninety-five patients and six normal subjects were included for the comparison. The clinical situations differed, ranging from healthy subjects to patients with acute respiratory failure in the intensive care unit.
The experimental procedure involved changing the inspired oxygen fraction (FIO2) in 4–6 steps in order to obtain arterial oxygen saturations (SaO2) in the range from 90–100%. This procedure allows plotting a FIO2/SaO2 or FEO2/SaO2 curve, the shape and position of which was quantified using the mathematical model estimating pulmonary shunt and a measure of ventilation-perfusion mismatch (ΔPO2). This procedure was performed using either arterial blood samples at each FIO2 level (invasive approach) or using values from the pulse oximeter (non-invasive approach).
The model provided good fit to data using both the invasive and non-invasive experimental approach. The parameter estimates were linearly correlated with highly significant correlation coefficients; shuntinvasive vs shuntnon-invasive, r2 = 0.74, P <0.01, and ΔPO2invasive vs ΔPO2non-invasive, r2 = 0.97, P <0.001.
Pulmonary gas exchange can be described equally well using non-invasive data. The simplicity of the non-invasive approach makes the method suitable for large-scale clinical use.
KeywordsPulmonary gas exchange Biological models Ventilation-perfusion ratio Physiologic monitoring Oximetry
This work was partially supported by grants awarded by the Danish Heart Foundation, the Danish Research Academy under the DANVIS program, the Research Foundation for Northern Jutland County, and by the IT-committee under the Danish Technical Research Council.
- 11.Malczynski J, Korup E, Rees SE, Andreassen S, Thorgaard P, Toft E (1999) The lung alveolar- lung capillary oxygen pressure drop as a new measure of lung problems in left sided heart failure—a new approach to estimate cardial decompensation. Proc Nordic Congress in Cardiology, ReykjavikGoogle Scholar
- 12.Nunn JF (1993) Nunn's applied respiratory physiology. Butterworth-Heinemann, Oxford, UKGoogle Scholar
- 13.Lentner C (1990) Geigy scientific tables, vol. 5. Heart and circulation. CIBA-GEIGY, Basel, SwitzerlandGoogle Scholar
- 14.Benumof JL (1990) Respiratory physiology and respiratory function during anesthesia. In: Miller RD (ed) Anesthesia. Churchill Livingstone, New York, USA, p 523Google Scholar