CHAPTER 43 Basics of Ventilator


In the modern era, a sick patient’s care cannot be imagined without a mechanical ventilator. With growing life expectancy and the burden of comorbid illness, more patients get admitted to the intensive care unit (ICU) and require ventilatory support in one or the other forms. The orientation and understanding of the ventilator are a must for all intensivists.

A mechanical ventilator is an automated machine that transforms the energy in a predetermined manner to augment or replace the patient’s muscles in performing the work of breathing.

Components of a Ventilator

The functioning of a ventilator can be visualized in terms of the following components:

  • Power source.

  • Controls.

  • Monitors.

  • Safety features.

Power Source

It includes a gas supply system, batteries, and the power source for the mechanical ventilator.

Various Options for Power Supply

  • Gas pressure to operate inspiratory flow and run valves and switches by supplying mechanical power.

  • Gas pressure to drive inspiratory flow, and electrically powered valves and switches (most commonly used).

  • Electrically powered turbines/compressors for inspiratory gas flow as well as to run valves/switches.

The generation of inspiratory flows can be achieved in various ways (Table 43.1).

Table 43.1 Techniques of generation of inspiratory flows

Table 43.1 Techniques of generation of inspiratory flows




The gas supply from the gas pipeline or cylinder is used to generate required inspiratory flows

  • Achievable flow rate—200 L/min

  • Minimal battery power consumption

  • It requires a stable supply of pressurized gas, with a minimum flow and pressure of 120–150 L/min and 200 kPa, respectively


A compressor generates pressurized gas flows

  • Achievable flow rates—240 L/min

  • Able to compensate for a large amount of leaks

  • It does not require a compressed air supply

  • Does need compressed oxygen supply (120 L/min)


A flexible gas reservoir produces inspiratory flows

  • Can precisely control the composition of the gas mixture

  • Does not require 200 kPa supply (suitable for low-flow gas supply)

  • Has more moving parts and points and hence high chances of failure

  • Not suitable for NIV use because of inability to compensate for large leaks


The volume of the rigid chamber is mechanically manipulated to generate inspiratory flows

  • Controls the delivery of volume more accurately

  • More economical on gas use

  • Poor compensation for gas leak

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Dec 11, 2022 | Posted by in ANESTHESIA | Comments Off on CHAPTER 43 Basics of Ventilator

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