The automatic selection of ventilation parameters during the initial phase of mechanical ventilation.

OBJECTIVE

To test a method that allows automatic set-up of the ventilator controls at the onset of ventilation.

DESIGN

Prospective randomized crossover study.

SETTING

ICUs in one adult and one children's hospital in Switzerland.

PATIENTS

Thirty intubated stable, critically ill patients (20 adults and 10 children).

INTERVENTIONS

The patients were ventilated during two 20-min periods using a modified Hamilton AMADEUS ventilator. During the control period the ventilator settings were chosen immediately prior to the study. During the other period individual settings were automatically determined by the ventilatior (AutoInit).

MEASUREMENTS AND RESULTS

Pressure, flow, and instantaneous CO2 concentration were measured at the airway opening. From these measurements, series dead space (V(DS)), expiratory time constant (RC), tidal volume (VT, total respiratory frequency (f(tot), minute ventilation (MV), and maximal and mean airway pressure (Paw, max and Paw, mean) were calculated. Arterial blood gases were analyzed at the end of each period. Paw, max was significantly less with the AutoInit ventilator settings while f(tot) was significantly greater (P < 0.05). The other values were not statistically significant.

CONCLUSIONS

The AutoInit ventilator settings, which were automatically derived, were acceptable for all patients for a period of 20 min and were not found to be inferior to the control ventilator settings. This makes the AutoInit method potentially useful as an automatic start-up procedure for mechanical ventilation.