High frequency oscillation (HFO) is increasingly used to support adults with ARDS. Little data are available to guide the transition to conventional mechanical ventilation (CMV); commonly this occurs when mean airway pressure has been weaned below 24 cmH2O. This study aimed to identify predictive factors for successful transition from HFO to CMV.
Retrospective chart review of all patients receiving HFO in our institutions from 2000 to 2005. Data are presented as mean ± SD. Student’s t-test was used for comparisons.
117 patients received HFO, with a mean age 50.9 ± 18.8 years. We excluded from analysis patients who died on HFO (n=10), or who were transitioned for withdrawal of care (n=25) or other reasons (e.g. hemodynamic compromise or deterioration on HFO, n=17). The remaining 65 patients were transitioned to CMV with a view to weaning. Of these, 24 (37%) died a mean of 19.1 ± 24.1 days after transition (“non-survivors”) and 41 (63%) survived to discharge (“survivors”). Comparing non-survivors with survivors, no differences were noted in illness severity when HFO was initiated (APACHE II 19.1 ± 6.8 and 21.1 ± 8.3, p=0.20; PaO2/FiO2 ratio 105 ± 43.3 and 120 ± 74.0, p=0.49; oxygenation index 32.1 ± 13.6 and 34.4 ± 16.4, p=0.39). At the time of transition to CMV, no difference was noted between non-survivors and survivors in mean airway pressure (23.6 ± 2.6 cmH2O and 24.6 ± 3.9 cmH2O, p=0.062) or ventilator frequency (4.90 ± 1.59 Hz and 4.93 ± 1.84 Hz, p=0.43). However, non-survivors had significantly worse oxygenation at transition than survivors (PaO2/FiO2 ratio 191 ± 74.3 and 224 ± 72.3, p<0.05; OI 14.4 ± 6.1 and 12.0 ± 3.3, p<0.05).
Despite similar severity of illness and oxygenation at initiation of HFO, patients who did not survive following successful transition to CMV demonstrated worse oxygenation parameters at the time of transition.
These finding may suggest a role for oxygenation indices in the decision to transition from HFO to CMV.
Satomi Shiota, Consultant fee, speaker bureau, advisory committee, etc. Speakers fees