Pressure-controlled ventilation via a minitracheostomy tube: experimental study using a mechanical lung model

To obtain basic data on pressure-controlled ventilation (PCV) via a minitracheostomy tube (MTT), we conducted an experimental study using a mechanical lung model. MTTs with internal diameters of 4.0, 4.5-, and 5.0 mm were used. To examine the effectiveness of PCV via an MTT for the lung with low compliance, the ventilated volumes were measured at compliances ranging from 10 to 50 ml/cmH2O. The alveolar pressures and ventilated volumes of the 4.0-, 4.5-, and 5.0-mm MTTs were about 40%, 50%, and 60% of the values for the 8.0-mm endotracheal tube in the absence of air leakage, respectively, and in the presence of air leakage they fell a further 20%. To obtain a ventilated volume of 500 ml, the inspiratory pressures needed were 40, 30, and 20 cmH2O for the 4.0-, 4.5-, and 5.0-mm MTTs, respectively. In the model of low lung compliance (10 ml/ cmH2O), the ventilated volumes decreased to 40% of those seen in the normal compliance model (50 ml/cmH2O) at each inspiratory pressure, due to greater air leakage. PCV via an MTT produced acceptable ventilated volumes in the lung model with air leakage. However, our results indicate that under conditions of low lung compliance, PCV via a