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Continuous non‐invasive monitoring of energy expenditure, oxygen consumption and alveolar ventilation during controlled ventilation: validation in an oxygen consuming lung model
Author(s) -
Holk K.,
Einarsson S. G.,
Svensson K. L.,
Bengtson J. P.,
Stenqvist O.
Publication year - 1996
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1996.tb04484.x
Subject(s) - respiratory quotient , medicine , ventilation (architecture) , dead space , oxygen , respiration , carbon dioxide , zoology , energy expenditure , resting energy expenditure , respiratory system , nuclear medicine , anesthesia , thermodynamics , physics , anatomy , chemistry , organic chemistry , quantum mechanics , biology
Background: We have developed a combined indirect calorimetric and breath‐by‐breath capnographic device (GEM) for respiratory monitoring: oxygen consumption (V̇O 2 ), carbon dioxide excretion (V̇CO 2 ), respiratory quotient (RQ), energy expenditure (EE), alveolar ventilation (V̇ A ) and dead space/total ventilation (V D /V T ). Methods: The device was tested in a lung model in which V̇O 2 was achieved by combustion of hydrogen. V̇CO 2 was achieved by delivering CO 2 into the single alveolus combustion chamber. V̇O 2 , V̇CO 2 , compliance, and anatomical dead space could be varied independently. Results: Measured V̇O 2 was 101±3% (SD) of set value at a F 1 O 2 <0.6 and 101±7% at a F 1 O 2 >0.6 during 15 hours of testing. The corresponding V̇CO 2 values were 99±2% and 102±7%. The GEM could with good accuracy measure accumulated energy expenditure (EE) during simulated unstable patient conditions up to a F 1 O 2 of 0.8. At F 1 O 2 above 0.8 V̇CO 2 and V̇O 2 could be estimated using a default RQ value of 0.85. On‐line estimated V̇ A and V D /V T values could be obtained at any F 1 O 2 up to 1.0. In a test sequence with stable V̇O 2 and V̇CO 2 the GEM adequately followed changes in V̇ A , induced by changes in anatomical dead space, breathing frequency and compliance. Conclusion: The overall performance of the device is satisfactory and well comparable with any equipment tested. It allows near‐continuous non‐invasive monitoring of EE, V̇O 2 , V̇CO 2 , V̇ A , V D /V T in ventilated, critically ill patients, providing a rationale for ventilator settings and nutritional support.