Main types of ventilator

1. Constant pressure ventilator

When inhaling, the ventilator pumps a certain pressure of gas into the airway, which causes the alveoli to expand, and the airway pressure gradually rises. When the predetermined pressure is reached, the airflow is terminated and turned into the expiratory phase. The tidal volume of this type of ventilator is related to the preset pressure, inspiratory time, and flow rate of the ventilator. If the flow rate is low, the inspiratory time is short, the predetermined pressure is low, and the tidal volume is small, otherwise the tidal volume is increased. Decreased lung compliance or increased airway resistance with bronchospasm can reduce tidal volume.

The disadvantage of this type of ventilator is that when the airway pressure increases, the tidal volume cannot be guaranteed. The advantage is that when the airway leaks, it must also maintain a certain pressure and maintain proper ventilation. Keep pressure and keep capacity.

2. Constant volume ventilator

The ventilator pumps a fixed volume of gas into the airway and lungs of the patient, producing inspiratory and expiratory actions. The advantage of this type of ventilator is that it can guarantee a certain tidal volume in a closed airway state within a safe pressure range. The disadvantage is that airway leakage cannot be compensated, and excessive airway pressure can also cause hypoventilation. In short, this type of ventilator does not guarantee pressure.

3.Timed ventilator

It is a timing, pressure-limiting and constant-flow ventilator. The ventilator generates airflow and enters the airway for a predetermined time. Inhalation stops and expiration occurs. During the expiratory phase, low-pressure airflow still passes through the airway. Its inspiratory time, respiration frequency, inspiratory / exhalation ratio, and inspiratory oxygen concentration can be adjusted.

The above classification is based on the conversion of inspiratory and expiratory phases. There are also classifications by control method (electric, pneumatic) and use. Another type is a high-frequency ventilation ventilator, which is characterized by high breathing frequency, low tidal volume, and non-closed air circuit operation.