Design and effectiveness of a membrane-pump-driven ventilator for mice.

To perform mechanical ventilation of mice in the absence of highly expensive commercially available devices, we developed a membrane-pump-driven respirator and studied its practicability. The continuous airflow generated by the membrane pump was changed into an intermittent flow by using a multifunction timer. Tidal volume was adjusted by a rotary dimmer regulating the electric power onto the pump. The expiration air left the circuit through openings at the tube connection. Mice were ventilated with room air for 5 h with a tidal volume of approximately 200 muL. In group 1 (n = 6), ventilation was performed with a frequency of 110 min-1, in group 2 (n = 6) with a frequency of 150 min-1. Spontaneously breathing anesthetized mice (n = 6) served as controls. In addition we performed single-lung open-chest ventilation for 1 h in two animals. The parameters of arterial blood gas analyses were within the normal range except for moderate hyperventilation in group 2. Single-lung ventilation led to a significant decline (P < 0.05) of pO2 and SO2, whereas the pCO2 remained within the normal range. Respiratory rate, tidal volume and pressure limitation can be adjusted for optimal ventilation. In addition, the device provides a minimalized dead space and impedes potential alveolar damage caused by negative pressure generated by spontaneous inspiration during positive-pressure ventilation.