Basics of Mechanical Ventilation
Mechanical ventilation is a life-sustaining treatment. A mechanical ventilator is a machine that helps people breathe when they cannot get enough air on their own. The mechanical ventilator is also called a ventilator, respirator or breathing machine. Most patients who require ventilator support due to a serious illness are cared for in a hospital's Intensive Care Unit (ICU). People who need a ventilator for a longer period of time may be admitted to a regular hospital unit, a rehabilitation center, or cared for at home.
- To facilitate breathing work. Some people can breathe, but it is very difficult. They feel short of breath and uncomfortable.
- To breathe for a patient who is not breathing due to brain injury or injury (such as coma) or high spinal cord injury or very weak muscles.
- If a patient has had a serious injury or illness that causes breathing efforts to stop, a ventilator may be used to help the lungs breathe until the person recovers.
This description seems very simple and easy to understand even for a layman. In clinical practice, it may not be as simple as it seems, but it is a little more. Many people, including some doctors, look at a ventilator with disgust. Some find it very difficult to understand and manage. The truth is far from that; It's nothing very special; It is necessary to understand that, after all, a ventilator is a man-made machine, used worldwide by doctors, and there should be no difficulty in understanding and managing it.
In the past, anesthesiologists were expected to know how ventilators worked, as many of them were designed based on simple mechanical principles. Now, almost all modern fans are controlled by microprocessors (computerized) and the technology is so complex that
acquiring this extra knowledge is no longer reasonable or justifiable. Now we have the new generation of specialists in all hospitals, known as Biomedical Engineers, and they have the knowledge and maintain the machines.
Based on the construction concept, a fan can be defined as,
• “A ventilator is a machine – a system of related elements designed to alter, transmit and direct applied energy (pneumatic energy or electricity) in a predetermined manner to perform useful work, to augment or replace the patient's muscles in performing the breathing work.”
Basically, any ventilator must have two components to perform artificial ventilation.
A control mechanism (a brain): Command what to do to ventilate the patient.
A driving mechanism (a muscle): Carry out the work of ventilation as ordered by the control mechanism (brain).
modern fan FAN CLASSIFICATION
Air movement into the lungs is provided by contraction of the respiratory muscles, producing subatmospheric (negative) intrapleural and intraalveolar pressures. The pressure gradient thus formed between the upper airways and the alveoli allows air to move into the lungs. Exhalation is normally passive and the natural elastic recoil of lung tissue causes an increase in intra-alveolar pressure to reverse the pressure gradient and allow air to flow out of the lungs.
Mechanical ventilation is provided by applying a negative pressure around the chest or by generating a positive pressure above atmospheric pressure in the upper airways.
Although negative pressure ventilation does not require endotracheal intubation, it cannot overcome substantial increases in airway resistance or decreases in lung compliance and also limits patient access.
Therefore, due to the construction concept and priority in development, mechanical fans are broadly classified into two groups, namely Negative Pressure Fans and Positive Pressure Fans.
Mechanical ventilation modes:
Originally, the method by which a ventilator performs the respiratory cycle is called 'Mode' of ventilation. In other words, it must have all four phases of the respiratory cycle, namely, inspiratory phase, change from inspiration to expiration, expiratory phase and onset of inspiration (change from expiration to inspiration). Modes that have all four phases are known as “Standard Modes” (Ex: control mode, assist/control mode). There are several more recent techniques that have different characteristics and are applied in special situations, which can be called “Special Modes”.
After the advent of numerous forms of ventilation support, it is better defined as “the method or technique by which the patient and the ventilator interact to perform the ventilation cycle”.
More precisely, there are only two primary modes and the third “Assistance/Control” is a combination of the first two modes.
1. Controlled Mechanical Ventilation: CMV
2. Ventilation in assisted mode: Assist
3. Assisted/Controlled Ventilation: A/C Mode
Four of the others on the list are just modifications to the inspiratory phase, namely,
1. Pressure Support Ventilation: PSV
2. Pressure Controlled Ventilation: PCV
3. Inverse proportion ventilation: IRV
4. Proportional Assisted Ventilation: PAV
Another four on the list are modifications only in the Expiratory Phase. They are,
1. Zero end-expiratory pressure: (expiratory delay) ZEEP
2. Negative end-expiratory pressure: NEEP
3. Positive End Expiratory Pressure: PEEP
4. Continuous Positive Airway Pressure: CPAP ZEEP and NEEP are no longer in use
The other four modes are again not primary modes. They are called “Special Ventilation Modes”.
1. Synchronized Intermittent Mandatory Ventilation: SIMV
2. Biphasic Positive Airway Pressure: BIPAP
3. Ventilation with airway pressure release: APRV
4. Mandatory Minimum Volume: MMV
AVAILABLE MODES
There are two basic categories of modes: Controlled or Assisted.
Controlled Ventilation
In controlled ventilation, the ventilator starts breathing and performs all the work of breathing.
Assisted Ventilation
In assisted ventilation, the patient starts and ends all or some breaths, with the ventilator providing a variable amount of support throughout the respiratory cycle.
