INTERMITTENT POSITIVE PRESSURE VENTILATOR (IPPV)

Typical Number in Hospital: 30

Cost Bands: 4

References: 2

This is the most common form of ventilator used during anaesthesia or in intensive care (life support) to assist or replace the patient's own Respiratory effort. It consists of a mechanism for inflating the lungs in a rhythmic pattern, usually via a cuffed tube inserted into the trachea. This is sometimes called a lung ventilator, or is referred to by some feature of its operation (e.g. minutes volume divider).

It consists of a Breathing circuit containing bellows, bags, tubes, valves, filters, and measuring transducers, and a drive and control circuit including timing devices, motors, solenoids and valves. There are a large number of variations on the main theme, a few of which are given below.

1. Application - whether it is to be used during anaesthesia, or for intensive care. Some types cannot be used for both.

2. Breathing circuit - whether suitable for use in closed, open, or T-piece circuits.

3. Driving force - whether driven by electric motor, compressed gas, or from a continuous flow anaesthetic machine.

4. Type of ventilation - main types include constant pressure, volume, or flow.

5. Method of cycle timing - this may be by time, preset volume, pressure, or triggered by the patient.

6. Respiratory pattern - particular machines may be able to vary the relative lengths of the phases and be able to provide positive, atmospheric, or negative pressure during all or part of the expiratory phase.

7. Other features which may need specification when selecting an automatic IPPV for a specific job are the peak inspiratory flow rate, flexibility of performance, ease of sterilization, portability, and suitability for particular patients such as infants, or those with low compliance lungs.