2003 OPEN FORUM Abstracts
DETERMINATION OF A TARGET GROUP OF ADULT ARDS PATIENTS FOR HIGH FREQUENCY OSCILLATORY VENTILATION (HFOV)
Karel Roubik, M.Sc., Ph.D., Jan Pachl*, M.D., Ph.D., Petr Waldauf*, M.D.
Czech Technical University, FEE, Dep. of Radioelectronics K337, Biomed. Lab.,
Technicka 2, CZ - 166 27, Prague 6, Czech Republic
*Charles University, 3rd School of Medicine, Dep. of Anesthesiology and CCM,
Srobarova 50, CZ - 100 34, Prague 10, Czech Republic
Background: HFOV is being increasingly used as a rescue application after failure of conventional mechanical ventilation (CMV). Nevertheless HFOV can be also ineffective. The aim of this study was to define a target group of adult ARDS patients suitable for HFOV treatment.
Method: A prospective observational study. 30 adults (55±19 years) fulfilling the ARDS criteria (Hypoxemic index HI = PaO2/FIO2 < 200 Torr, the X-ray criteria and PCWP <= 18 Torr) were indicated for HFOV as a "rescue" method on the day of admission or in case of failure of conventional mechanical ventilation (CMV) in treatment of ARDS. For the initial phase the HFOV parameters (SensorMedics 3100B) were: f = 5 Hz, TI/T = 0.5, initial continuous distension pressure (CDP) = mean airway pressure (MAP) during CMV + 0.5 kPa, FIO2 HFOV = FIO2 CMV, bias flow = 40-60 l/min, pressure amplitude (.P) and tidal volume (VT) were set iteratively according to the arterial gases. Data collection: FIO2 CMV, MAP, PIP, PEEP and HI before HFOV; CMV duration before and after HFOV; CDP, VT, Raw, FIO2 HFOV, HI and arterial gases during HFOV. According to ARDS type, each patient was included either to the group of patients with pulmonary ARDS (ARDSp) or extrapulmonary ARDS (ARDSexp). Differences between the recorded parameters in the groups were analyzed. Finally, other criteria already presented in literature were examined.
Results: After HFOV introduction, there was no significant increase in HI in ARDSp group (change from 129±48 to 133±52 Torr after 6 hours of HFOV), but a very significant improvement in ARDSexp (from 114±56 to 200±67 Torr, p<0.01). The figure shows the course of HI during HFOV; time 0 hrs designates the last values on CMV. Initial optimal CDP for the best HI was 19.8±6.4 cmH2O in ARDSp and 27.9±6.3 cmH2O in ARDSexp (p<0.01).
Discussion: According to EMOAT study (Well GTJ et al., NICU, C.H.V.E., Rocourt, Belgium, 2002), patients with OI>20 are suitable for HFOV. It was confirmed also by this study. The combination of ARDSexp and OI>20 assures a definitely positive effect of HFOV, but there are a number of remaining patients also taking profit from HFOV. Therefore the OI>20 criterion is too strict.
Conclusion: ARDSexp patients form a target group for HFOV.