Tuesday, 19 December 2017

Types of Ventilator Modes

There are mainly three different types of Ventilators:

A. Assist mode:

In the assist mode, the patient is able to control their breathing. But they are unable to take sufficient amount of air. So in the assist mode the inspiration can be triggered by the patient’s attempt to breath. So the ventilator help the patient to inspire when he wants to do so.

B. Control mode:

This type of ventilators are required especially for the patients who are unable to breath theemselves. Here the breathing is controlled by a timer set to provide desired respiration rate. In this mode the ventilator has complete control over the patient’s respiration.

C. Assist Control mode:

It has the features of both assist mode and control mode. As in assist mode, here also the ventilator is triggered by the patient’s attempt to breath. If the patient fails to breath within a predetermined level, the control mode come into action and the timer automatically triggers the device to inflate the lungs. This mode depends on the patient’s physical condition. Patient can breath as long as he can, and when he fails to do so, the machine takes over the control. The assist – control mode is mainly used in critical care settings.

The ventilators are also classified into the following types depending on the inflation of lungs.

a. Pressure cycled ventilators: In some patients the pressure of the breathed air will not be the specific peak airway pressure. In pressure cycled ventilators, the inflation of lungs continues till the delivered gas to the patients reaches a predetermined level of pressure.

b. Volume cycled ventilators: Due to various lung disorders caused due to smoking problems, some patients cannot inspire upto the desired volume. In volume cycled ventilators, the ventilation of lungs continues till a specified volume of gas has been delivered to the patient. Advantages of volume – cycled ventilation are the selection of variable modes of ventilation, improved patient-ventilator synchronism etc. Also the tidal volume can be simply adjusted.

c. Time cycled ventilators: As the name implies, the patient is supplied with oxygen and other gases for a certain period of time. Time – cycled ventilation occurs as the inspiratory phase begins and gas flows through the ventilator circuits into the patient’s lung until a timing mechanism in the ventilator reaches a preset level. Once the preset time is reached, the inspiratory phase ends and the patient passively exhales. During time-cycled ventilation tidal volume is not controlled directly. The ventilator delivers a tidal volume dependent on gas flow rate. The gas flow rate has to be adjusted to maintain a desired tidal volume and limit peak inspiratory pressure.


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