What are the principles of ventilators medical


Synonym: respirator
English: respirator

1 definition

A Ventilator is a technical device that is used for ventilation therapy for patients with respiratory insufficiency.

2 basics

Ventilators use an endotracheal tube or tracheal cannula to generate excess pressure in the nasopharynx so that air flows into the lungs (inspiration phase).

Expiration takes place passively through the physiological retraction forces of the lungs. In order to ensure reliable function, a ventilator must control and maintain inspiration, the change to expiration, the expiration itself and the renewed change to inspiration.

3 pressure versus flow

In principle, breathing can be controlled in two different ways:

  • Pressure generators
  • Flow generators

With a flow, a breathing gas mixture is given into the lungs at a fixed flow rate. Even if the resistance in the lungs changes, the entire preset volume is given. This allows a variable part of the tidal volume to be ventilated past the lungs in the event of leaks in the ventilation system (e.g. insufficient blocking of the tube).

In the case of pressure generators, a fixed pressure is used to insufflate the breathing gas. As the airway pressure increases during inspiration, the volume insufflated decreases continuously. If the airway resistance increases acutely, the insufflated volume also decreases. If there is a leak, the ventilator will still try to reach the preset pressure and improve ventilation.

4 control principles

In principle, a ventilator can control ventilation according to volume, pressure or time. Maximum values ​​can be specified for inspiration, and when they are reached, a transition is made to expiration.

With volume control, inspiration continues until a defined inspiration volume is reached. Similarly, the pressure-controlled respirators are ventilated until a preset airway pressure is reached. Timed respirators inspire over a predetermined period of time.

In the case of the respirators, for example, a maximum pressure or a maximum volume can be given as a limitation, and when this is reached, a switchover to expiration occurs at the latest. A volume-controlled ventilator can be pressure-limited, or a pressure-controlled device can be volume-limited.

By varying the control and ventilation parameters, many different ventilation techniques can be used for ventilation therapy.

5 triggers

A trigger is a microprocessor-controlled component of modern ventilation devices, which recognize the patient's own breathing drive and only start inhalation when requested by the patient (assisted ventilation - IPPB). It can be used when weaning long-term ventilators.

6 components of the respirator

A ventilator essentially consists of the following components:

  • Drive and control system (electronically controlled, electrically driven)
  • Gas mixing device for supplying and mixing the breathing gas
  • Patient system (breathing tubes, humidifiers, valves)
  • Monitoring and operating unit

See also:Ventilation, ventilation therapy