Oxygenation index, an indicator of optimal distending pressure during high-frequency oscillatory ventilation?
OBJECTIVE
To test the hypothesis that, during high-frequency oscillatory ventilation (HFOV) of pigs with acute lung injury, the oxygenation index (OI = Paw*FIO(2)*100/PaO(2)) is minimal at the lowest continuous distending pressure (Paw), where the physiological shunt fraction is below 0.1 (Paw(optimal)).


METHODS
Prospective, observational study in a university research laboratory.


METHODS
Eight Yorkshire pigs weighing 12.0+/-0.5 kg, with lung injury induced by lung lavage.


METHODS
After initiation of HFOV, the pigs were subjected to a stepwise increase of Paw to obtain under-inflation, optimal inflation and over-distension of the lungs (inflation) in series, followed by a similar decrease of Paw (deflation).


RESULTS
At each Paw level, the OI and physiological shunt fraction were determined. The OI reached a minimum of 6.2+/-1.4 at Paw 30+/-4 cmH(2)O during inflation and a minimum of 2.4+/-0.3 at Paw 13+/-2 cmH(2)O during deflation. Paw(optimal) was 32+/-6 cmH(2)O on the inflation limb and 14+/-2 cmH(2)O on the deflation limb. The difference between the Paw at minimal OI and Paw(optimal) was -1.9+/-4.2 cmH(2)O (NS) during inflation and -1.5+/-1.6 cmH(2)O (p<0.05) during deflation. In 15 out of the 16 comparisons, the difference in Paw was within one step (+/-3 cmH(2)O).


CONCLUSIONS
The minimal OI is indicative for the Paw where oxygenation is optimal during HFOV in surfactant-depleted pigs.
Department of Clinical Physics & Informatics, Vrije Universiteit Medical Center, PO Box 7057,1007 MB Amsterdam, The Netherlands. hr.genderingen@VUmc.nl
Huibert R
HR
van Genderingen
Johannus A
JA
van Vught
Jos R C
JR
Jansen
Elisabeth L I M
EL
Duval
Dick G
DG
Markhorst
Adrian
A
Versprille
D000818:Animals; D006612:High-Frequency Ventilation; D010100:Oxygen / Q000600:supply & distribution*; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome; D013552:Swine
D010100:Oxygen