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.