High-Frequency Oscillatory Ventilation in Adults: Discussion
The purpose of the current study was to summarize the experience with HFOV therapy in three Toronto medical/surgical ICUs. We observed the following. First, HFOV is used as rescue therapy in adults with ARDS due to a wide variety of etiologies, when patients are already requiring high Fio2 and/or high airway pressures. Second, the use of HFOV is associated with improvements in ventilation and oxygenation, the latter permitting significant reductions in delivered Fio2. Third, 26% of patients had HFOV therapy discontinued due to difficulties with oxygenation, ventilation, or hemodynamics. Fourth, the incidence of pneumothorax is higher in this population than in other reported ARDS patients. Fifth, compared with survivors, nonsurvivors are older, have higher severity of illness, require higher peak pressures during CV, and have received CV for a greater number of days prior to receiving HFOV therapy.
Our findings are similar to those of previous observational trials-’ and those of one randomized controlled trial, showing that HFOV therapy is a safe and effective mode of ventilation in the treatment of ARDS in adults. The observational studies reported improvements in oxygenation and adequate ventilation in adults with severe ARDS treated with HFOV. Two of these trials” identified the fact that a greater number of pretreatment days receiving CV was significantly associated with mortality. In both studies, the 30-day mortality rates were quite high (Fort et al, 53%; Mehta et al, 67%). However, HFOV was applied as rescue therapy to patients requiring high Fio2 and/or ventilatory pressures, and deaths were due to multiple organ failure, not to hypoxemia.
There is only one randomized trial evaluating HFOV in adults. In this multicenter trial, 148 adults with ARDS were randomized to CV or HFOV. The HFOV group showed early improvement in Pa02/Fl02 ratio compared with the conventional group, however, the difference did not persist beyond 24 h. The 30-day mortality rate was 37% in the HFOV group, and 52% in the CV group (p = 0.102). There were no significant differences in hemodynamic variables, oxygenation failure, ventilation failure, or barotrauma between the two groups.