A novel mechanical ventilator providing flow-controlled expiration for small animals.

For investigating the effects of mechanical ventilation on the respiratory system, experiments in small mammal models are used. However, conventional ventilators for small animals are usually limited to a specific ventilation mode, and in particular to passive expiration. Here, we present a computer-controlled research ventilator for small animals which provides conventional mechanical ventilation as well as new type ventilation profiles. Typical profiles of conventional mechanical ventilation, as well as flow-controlled expiration and sinusoidal ventilation profiles can be generated with our new ventilator. Flow control during expiration reduced the expiratory peak flow rate by 73% and increased the mean airway pressure by up to 1 mbar compared with conventional ventilation without increasing peak pressure and end-expiratory pressure. Our new ventilator for small animals allows for the application of various ventilation profiles. We could analyse the effects of applying conventional ventilation profiles, pressure-controlled ventilation and volume-controlled ventilation, as well as the novel flow-controlled ventilation profile. This new approach enables studying the mechanical properties of the respiratory system with an increased freedom for choosing independent ventilation parameters.