Interactive ventilation: first experience with patient controlled weaning by using a Siemens-SV 300 Automode® ventilator

Introduction

The new Siemens SV-300 A ventilator switches automatically between control and support mode of ventilation. At the first sign of respiratory effort, the ventilator allows the patient to breathe spontaneously with a preset pressure or volume support. In case of apnea, the ventilator automatically changes to a preset volume or pressure control mode. In our study the combination of pressure control and pressure support mode was used. 20 patients (pts) who underwent brain tumor surgery were randomized either to the Automode^®-Group (n = 10, age 24–76 years, mean 49.7) or to the conventional weaning procedure with manually regulated SIMV-mode (Manual Mode, n = 10, age 22–70, mean 47.9) immediately after entering the ICU. Time from entering the study to extubation (weaning time) was measured. PCO₂-Levels during the weaning period were measured for each patient in fixed time intervals. The number of manipulations on the respirator during the whole weaning period was counted for each patient.

Aim of the study

Identification of malfunctions, cases of apnea and comparison of average weaning time, pCO₂ levels and number of manipulations necessary during the weaning period.

Results

In the Automode^®-Group no malfunctions or cases of apnea were observed. Average weaning time was shorter in the Automode^®-Group (Fig. 1), pCO₂-levels seemed to be more stable (Fig. 2). The number of manipulations on the respirator were significantly lower in the Automode^®-Group (Fig. 3).

Conclusions

With the new Automode^®-option weaning seems to be more comfortable for the patient and the staff taking care. Automode^® is an approach to adapt the machine to the patient and not the patient to the machine. Spontaneous ventilation is possible at an early point and at every time during the whole weaning process. PCO₂ levels seem to be more stable as a sign of a better adaptation to the patients ventilatory needs. Shortening of the total weaning time seems to be possible. Significant reduction of alarm beeps and consecutively less manipulations on the respirator (no apnea alarm, no struggling with SIMV-mode) reduce stress for the nursing staff.

Figure 1

Average weaning time (minutes, 10 pts each group with STD).

Figure 2

Mean pCO₂-levels during weaning period (mmHg with STD for each patient).

Figure 3

Average number of manipulations.