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Ventilators

Published on 18/8/2018 & updated on 18/8/2018
It provides artificial respiration. Artificial respiration is given to the patient because the cerebral cortex cannot survive without oxygen for more than 5 minutes. So proper external oxygen supply is given before heart muscle fails. Artificial respiration ventilates the alveoli with air. Inside intensive care unit, a patient often requires breathing assistance. Therefore, ventilators provide enriched oxygen, medicated air at a controlled temperature. They operate at different modes. Controlled breathing is the one in which breathing starts with a timing mechanism. It is utilized when patient cannot breathe completely on their own. It provides Inspiration and expiration at a fixed rate. Assisted breathing is patient initiated breathing. It is used when a person has breathing difficulty due to high airway resistance. Third mode is Assist – Control mode in which servo controlled ventilators are used that can switch to any mode depending on patient condition.

Methods of Artificial Respiration

Mechanical Methods of Artificial Respiration

During severe respiratory failures, artificial respiration is given for a longer time. Two types of Mechanical methods are
  1. Negative Pressure Ventilator
  2. Positive Pressure Ventilator

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Ventilators

Negative Pressure Ventilator

This method consists of airtight chamber and electrically driven pump. Pump is used to increase and decrease the pressure inside the chamber.
Procedure: The patient is made to sit inside the chamber with head and neck outside the chamber. When pressure inside the chamber increases, due to negative pressure chest wall expands. If chest wall expands, more air is drawn into the lungs. At the same time, when pressure in the chamber increases, expiration occurs. The method is used for respiratory muscle paralysis.

Positive Pressure Ventilator

This method inflates the lungs with intermittent positive pressure. A tube passes through mouth into the trachea. A pump delivers the oxygen supply or oxygen mixed with carbon di-oxide supply. Between each pump stroke, gas flow is disturbed. So gas is expelled.

Non-mechanical Methods of Artificial Respiration

Holgen – Nielson method and Mouth-to-Mouth breathing technique is used. Nielson method is also called as Backpressure arm lift method, which gives a better result.

Working of a Ventilator

working of a ventilator During inspiration process, the air compressor draws the air via air filter and gives it to the main solenoid. The main component is the bellows that has bottom and top valves attached on it. After the air reaches, the solenoid forces bottom inlet valve of bellow to open and lower outlet valve to close. Control valve allows the oxygen to pass into the chamber in a controlled manner. Bellow chamber has high pressure and so it compresses the bellows and forces the upper outlet valve to open. Hence, the oxygen enriched air passes through main solenoid, reaches the external tubes. Then it goes to bacterial filter, humidifier, nebulizer and lastly to lungs. Humidifier is used to prevent lung damage of the patient. It humidifies the oxygen using heat steam. Nebulizer produces spray of water or medication into patient’s inspiration air. They measure volume of exhaled air also and send alarm to stop expiration and start inspiration. Meanwhile, air compressor draws room air via inlet filter. They close the upper outlet valve of bellow chamber. Due to the weight of bellow, bottom chamber opens and main solenoid instructs the inlet valve of chamber to close. Volume of exhaled air is indicated using spirometer alarm. The expired air reaches main solenoid via outlet 2. The system electronics trips the solenoid at the end patient expiration.




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