From low-tidal-volume ventilation to lowest-tidal-volume ventilation

Introduction

The therapeutic measures of lung-protective mechanical ventilation used in treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) have revived the interest in high-frequency ventilation (HFV). The reduction of the tidal volume during the conventional ventilation (CV) in terms of low-tidal-volume ventilation is not unboundedly feasible. However, HFV allows a further reduction of tidal volume. Established HFV techniques are high-frequency oscillation (HFO), high-frequency percussive ventilation (HFPV) and superimposed high-frequency jet ventilation (SHFJV). The aim of this study was to evaluate the amelioration of the oxygenation index (OI).

Methods

Twenty-four patients with ALI/ARDS admitted to an ICU were involved. Haemodynamic parameters, blood gas analysis, ventilation pressures (positive end-expiratory pressure (PEEP), plateau and mean airway pressures) were measured. The use of HFV was indicated if the OI was still lower than 200 under CV. The initial parameters (plateau and mean airway pressure, PEEP, I:E ratio, ventilation frequency and FiO₂) were chosen as the latest setups of the CV. We randomly used one of the abovementioned techniques to treat patients with ALI/ARDS. The clinically relevant parameters were proved every 4 hours and ventilation was adopted.

Results

All patients treated with HFV showed an amelioration of OI within 24 hours after the start (Figure 1). Furthermore, we registered a significant increase of OI after 24 hours compared with basis CV (Figure 1). However, we did not measure any significant changes between the three HFV techniques at this time point. We observed less/no haemodynamic disturbances with SHFJV and HFPV compared with HFO. It was therefore important to clinically stabilize the patients.

Figure 1

Conclusion

We achieved a significant amelioration of the OI using HFV rather than with CV. Each of the HFV techniques, however, needs a period of a few hours to predict that the technique is responding or nonresponding.