Most of us have never heard the term mechanical ventilation before the COVID-19 pandemic. However, the history of mechanical ventilators dates back to the second century. Medical research has defined it as a device that blows air into the larynx. At first, the researchers used the device on dead animals. The ‘iron lung’ was the first mechanical ventilator used on human beings in 1929.
The advancement in science and technology has revolutionized the world. Nowadays, mechanical ventilators are more advanced and effective.
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These mechanical devices are commonly used for COVID-19 patients who find difficulty breathing because of severe lung infection. These play a critical role in saving human lives amid this pandemic because they help a person breathe. Despite innumerable benefits, mechanical ventilation also involves certain risks.
A weaning program is switching a patient off from mechanical ventilation. Although choosing when to wean is a personal decision in many cases, weaning for a person feeling difficulty in breathing is always the decision of the physician treating him.
What is Mechanical Ventilation?
Mechanical ventilation is the process of providing artificial breathing to a patient who is finding difficulty in taking in and out the oxygen and carbon dioxide. A mechanical ventilator is a machine that blows air into the patient’s larynx to assist in breathing. The Roman physician Galen was the first to use this automated machine in the second century for a dead animal. Medical science recommends using mechanical ventilation for the patients losing their spontaneous breathing due to injury or disease.
A ventilator, respirator, or breathing machine is the instrument used for breathing assistance for a person with low oxygen levels and severe shortness of breath due to an infection. The use of these machines is common around the world nowadays amid the coronavirus pandemic. It is a form of life support for the patients under severe attack of the COVID-19.
Why do We Use Mechanical Ventilation?
Artificial breathing is used in patients suffering from acute lungs infection due to injury or disease to
- Ensure delivery of high concentration Oxygen to lungs
- Help patients get rid of Carbon Dioxide
- Decrease the amount of energy a patient uses on breathing to enable his body to fight the infection and speed up the recovery
- Help a patient breathe who is unable to breathe due to nervous system injury or infectious diseases or have weak muscles.
- Assist a patient in breathing who loses consciousness due to drug overdose, build-up of toxins in the body, or severe infection
What are the Types of Mechanical Ventilation?
There are two types of mechanical ventilation.
- Positive Pressure Ventilation
- Negative Pressure Ventilation
1-Positive Pressure Ventilation
It is the ventilation process in which air is blown into a patient’s lungs through a machine. Positive pressure ventilators were developed in the 1950s to assist persons with respiratory tract paralysis or polio. These machines use tubes to push the air into the patients’ lungs. Positive pressure ventilation is of two types, invasive and noninvasive ventilation.
Invasive Ventilation
Mechanical ventilation involving any instrument inside the trachea through the mouth is termed invasive ventilation.
Endotracheal Intubation
Ventilation in which a tube is inserted into the patients’ airway (trachea) through the mouth is endotracheal intubation.
Tracheostomy
In this ventilation, a tube is inserted in the airway (trachea) through an airway hole.
Noninvasive Ventilation
Noninvasive ventilation involves the usage of masks with ventilators to push air into the patients’ larynx. These ventilators are easy to use at home. Noninvasive ventilators are also of three kinds.
Continuous Positive Airway Pressure (CPAP)
It delivers constant and steady air pressure to the lungs throughout its usage.
Autotitrating Positive Airway Pressure (APAP)
In this ventilation process, the respirators change air pressure to the lungs according to the patients’ breathing patterns.
Bilevel Positive Airway Pressure (BiPAP)
The breathing machine used in this ventilation process delivers air with different pressure for inhalation and exhalation.
2-Negative Pressure Ventilation
Negative pressure ventilation is the process of sucking the air into the lungs through chest expansion and contraction. It is also of two kinds, the iron lung and chest cuirass.
Iron Lung
The ‘iron lung’ was the first mechanical ventilators used for human beings. In this ventilation process, a metal cylinder was used to envelop the patients’ bodies up to the neck. These ventilators are rare now.
Chest Cuirass
This ventilation process uses a small shell strapped around the patients’ chest to create negative pressure.
How Does Mechanical Ventilation Work?
The mechanical ventilation process for a patient depends on the type of ventilation he needs and the severity of the breathing issue. Usually, healthcare professionals insert an endotracheal tube (ET) into the patient’s windpipe or trachea through the mouth or nose. The other end of the line is then connected to the breathing machine to help the patient breathe. Here, it is pertinent to mention that the endotracheal tube and ventilators perform various functions. For example, they push the air and oxygen into the lungs, maintain constant low air pressure to save air sacs from collapsing, and help doctors remove mucous from the patients’ airways.
However, tracheostomy is recommended for patients with blockage in the trachea or tumor. In this process, a surgeon inserts a tracheostomy or breathing tube into the airway by making a hole in the neck and trachea. However, the process cannot be used for long. Patients under this ventilation can talk and eat. Modern ventilation machines provide pressure-controlled, volume-controlled, or dual-controlled ventilation.
What to Expect While on Ventilator?
As healthcare professionals recommend using a ventilator in acute conditions, it is not painful but uncomfortable. A person with a breathing tube in the trachea cannot walk, talk, and eat. However, patients with a trach tube can speak with special devices and eat certain foods on doctors’ recommendations.
Being on a ventilator requires patients to lie still on their stomachs in bed. The healthcare professionals forbid to lie on the back to ensure proper blood and oxygen supply to the lungs. The doctors, nurses, respiration therapists, and their support staff continually monitor the patients on the ventilators. They take regular chest X-rays and blood samples to judge the effectiveness of ventilators for the patients. The team adjusts the airflow of the ventilators and other settings based on these results.
What are the Benefits of Mechanical Ventilation?
The main benefits of mechanical ventilation are:
- It provides rest to the respiratory muscles because the patient does not need to work hard for breathing.
- Helps patients get adequate oxygen and exhale carbon dioxide.
- It gives patients hope to recover soon because they feel normal to breathe.
- Saves life by saving the air sacs from collapsing.
- Keeps airway stable by avoiding injury from aspiration.
It is also worth mentioning that mechanical ventilation cannot heal a patient. However, it provides the patients with a recovery chance through medication and treatment help.
Risks Involved in Mechanical Ventilation
Despite being a life-saving process, mechanical ventilation is also risky. Following are the risk factors involved in mechanical ventilation for more extended periods.
Infection
The primary risk factor involved in mechanical ventilation is an infection because an artificial breathing tube’s insertion allows germs to enter the lungs. Pneumonia and sinus infections are common in patients on ventilators. The patient may need antibiotics to fight the invading germs. Sometimes, it becomes so severe that the patient needs to be shifted to the intensive care unit.
Irritation
Irritation is another risk factor involved in mechanical ventilation. It is due to the rubbing of the artificial breathing tube with the tissues in the trachea. Some patients may develop irritation in the throat. Continuous irritation may cause inflammation in the lungs that lead to a chest cavity in later stages. Patients with irritation can show various symptoms.
Lungs Injury
Although there are rare chances that the patients may develop lung injury by mechanical ventilation, it can still occur. Certain factors can cause lung damage or injury when the patient is on artificial breathing. For example, the patient may suffer from oxygen toxicity if too much oxygen continuously reaches the lungs. The person can also suffer Pneumothorax due to the air leakage in the area between the chest walls.
Sometimes, too much pressure on the lungs may cause damage. The patient may suffer from lung disease that can make breathing even more difficult for him.
Vocal Cord Damage
Another rare complication that may arise from mechanical ventilation is vocal cord damage. The larynx has vocal cords that enable a person to speak. During the automated ventilation process, an artificial breathing tube is inserted into the larynx that may cause irritation in the vocal cords or even damage them. The patients may feel difficulty in speaking or change in voice. In some rare cases, the patient loses the ability to speak.
Weaning from Mechanical Ventilation
As we know that artificial ventilation is recommended only for those patients who cannot breathe independently, it is almost impossible to wean a patient off these devices. It happens in patients dependent on mechanical ventilation for considerably more extended periods. Their lungs become used to assistive breathing over time. Therefore, it is not recommended to remove the automatic ventilation system immediately from the patient. It can cause certain complications and even lead to death. Instead, always wait for the patient to be healthier and rely on his spontaneous breathing.
It is beneficial to reduce the air pressure during the weaning process and test the patients’ breathing system. Medical science also recommends the T-tube test. These tests enable healthcare professionals to analyze whether they can remove mechanical ventilation or not. It also allows the doctors to test the spontaneous breathing of the patient is working correctly or not.
However, if the results of these tests are not satisfactory, weaning from mechanical breathing is delayed. During this time, the doctors may need to consider the strategies contributing to the patients’ breathing system. One of the most effective strategies is synchronized intermittent mandatory ventilation that allows the health professionals to customize settings according to the patients’ needs. In this technique, a specified number of inflations are delivered to the lungs and checked whether spontaneous breathing is working or not. The process is repeated until the patient is recovered.
What are the Criteria for Weaning from Mechanical Ventilation?
Before weaning the patient from mechanical ventilation, the healthcare workers have to perform two tests.
- Wean Screen
- Weaning Performance Trial
Both the processes involve the analysis of weaning screens. Usually, the physicians do these screens daily and check whether the lungs are stable, and all other parameters are within the normal range. The recommended parameters are the PEEP parameter should always be less than 5-8cmH20 and FiO2 be less than 0.5.
Here, it is pertinent to mention that the patients with stable hemodynamics and solid neuromuscular functions pass weaning screen tests easily. After passing the test, they need a proper diet and minerals to boost their spontaneous breathing. They should avoid using drugs, especially steroids, that may cause weakness.
Bottom Line
The entire discussion proves that sudden weaning from mechanical ventilation is not possible if you want to save the patients’ life. Instead, always follow specific strategies to boost spontaneous breathing.
References
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