PMID- 2295108
OWN - NLM
STAT- MEDLINE
DCOM- 19900212
LR  - 20181113
IS  - 0832-610X (Print)
IS  - 0832-610X (Linking)
VI  - 37
IP  - 1
DP  - 1990 Jan
TI  - A clinical comparison of indices of pulmonary gas exchange with changes in the 
      inspired oxygen concentration.
PG  - 69-76
AB  - Several indices have been introduced as convenient alternatives to calculation of 
      the physiological shunt fraction (Qs/QT) for the assessment of pulmonary gas 
      exchange. These include: the arterial-alveolar oxygen tension ratio (a/APO2), the 
      arterial oxygen tension-inspired oxygen concentration ratio (PaO2/FIO2), the 
      respiratory index (RI), [A-a)DO2/PaO2) and the alveolar-arterial oxygen tension 
      difference [A-a)Do2). These indices are in use clinically despite the fact that 
      they may not accurately predict gas exchange in situations where FIO2, Qs/QT or 
      arterial-venous oxygen content is changing. The clinical stability of each of 
      these indices, relative to the behaviour of the physiological shunt, was 
      therefore investigated prospectively in ten mechanically ventilated postoperative 
      adults as FIO2 was varied from 0.30 to 1.00. None of the indices studied reliably 
      reflected the behaviour of the physiological shunt. As FIO2 was increased 
      incrementally from 0.30 to 1.00, 42 to 55 per cent of the measured changes in 
      these indices were opposite in direction to the corresponding changes in the 
      physiological shunt. The maximum magnitudes of the opposite changes were 
      substantial; 24 and 22 per cent for the a/APO2 and PaO2/FIO2 ratio respectively, 
      67 per cent for the RI and 101 per cent for the (A-a)DO2. We conclude that the 
      use of any of these indices for clinical assessment of a patient's gas exchange 
      defect when FIO2 is varying can be substantially misleading.
FAU - Herrick, I A
AU  - Herrick IA
AD  - Department of Anaesthesia, Queen's University, Kingston, Ontario, Canada.
FAU - Champion, L K
AU  - Champion LK
FAU - Froese, A B
AU  - Froese AB
LA  - eng
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Can J Anaesth
JT  - Canadian journal of anaesthesia = Journal canadien d'anesthesie
JID - 8701709
SB  - IM
MH  - Aged
MH  - Humans
MH  - Middle Aged
MH  - Pulmonary Gas Exchange/*physiology
MH  - *Respiration
MH  - Respiration, Artificial
MH  - *Weights and Measures
EDAT- 1990/01/01 00:00
MHDA- 1990/01/01 00:01
CRDT- 1990/01/01 00:00
PHST- 1990/01/01 00:00 [pubmed]
PHST- 1990/01/01 00:01 [medline]
PHST- 1990/01/01 00:00 [entrez]
AID - 10.1007/BF03007487 [doi]
PST - ppublish
SO  - Can J Anaesth. 1990 Jan;37(1):69-76. doi: 10.1007/BF03007487.