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)). DESIGN AND SETTING: Prospective, observational study in a university research laboratory. SUBJECTS: Eight Yorkshire pigs weighing 12.0+/-0.5 kg, with lung injury induced by lung lavage. INTERVENTIONS: 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). MEASUREMENTS AND 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). CONCLUSION: The minimal OI is indicative for the Paw where oxygenation is optimal during HFOV in surfactant-depleted pigs.
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)). DESIGN AND SETTING: Prospective, observational study in a university research laboratory. SUBJECTS: Eight Yorkshire pigs weighing 12.0+/-0.5 kg, with lung injury induced by lung lavage. INTERVENTIONS: 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). MEASUREMENTS AND 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). CONCLUSION: The minimal OI is indicative for the Paw where oxygenation is optimal during HFOV in surfactant-depleted pigs.
Authors: Dick G Markhorst; Jos R C Jansen; Adrianus J van Vught; Huibert R van Genderingen Journal: Intensive Care Med Date: 2005-01-20 Impact factor: 17.440
Authors: Casper W Bollen; Gijs Th J van Well; Tony Sherry; Richard J Beale; Sanjoy Shah; George Findlay; Mehran Monchi; Jean-Daniel Chiche; Norbert Weiler; Cuno S P M Uiterwaal; Adrianus J van Vught Journal: Crit Care Date: 2005-06-21 Impact factor: 9.097