How does a respirator work? Types, indications and operating modes of the ventilator

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A ventilator is a basic device that supports or replaces the work of the lungs. The ventilator supports breathing in people whose lungs, for various reasons, cannot work on their own. How does this device work?

What is a respirator?

A ventilator is a device that supports the work of the lungs. It can be a life-saving machine if we suffer from a medical condition that makes it difficult to breathe properly or if we cannot breathe at all.

The ventilator helps to force air in and out of the lungs so that the body can get the oxygen it needs. The person in need of a respirator may wear a fitted mask to help the oxygen from the ventilator reach the lungs or, if the condition is more severe, a breathing tube that is inserted into the throat to provide oxygen to the lungs.

Respirators are most often used in a hospital setting. Your doctor will monitor the amount of oxygen being pumped into your lungs by a ventilator. Another name for a respirator is “artificial lung”.

See also: Despite slow ventilators, the number of deaths from COVID-19 is not declining. Why? We ask the doctor

Indications for the use of a respirator

Not being able to breathe properly independently is known as respiratory failure and is life-threatening.

If the brain, heart, liver, kidneys and other organs don’t get enough oxygen, they won’t be able to function as they should. A ventilator can help you get the oxygen your organs need to function.

Respirator and health problems

Many types of illnesses and conditions can cause breathing difficulties, including:

1. acute respiratory distress syndrome (ARDS);
2. chronic obstructive pulmonary disease (COPD);
3. asthma;
4. brain trauma;
5. cardiac arrest;
6. pneumonia;
7. collapsed lung;
8. hit;
9. coma or loss of consciousness;
10. drug overdose;
11. hypercapnic respiratory failure;
12. pneumonia;
13. myasthenia gravis (Latin. myasthenia gravis);
14. sepsis, blood infection;
15. injuries of the upper spinal cord;
16. premature lung development (in infants);
17. Guillain-Barry Syndrome;
18. amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig’s disease.

Respirator and surgery

People who are under general anesthesia for surgery may need a respirator while they sleep. This is because some anesthetic medications can make it difficult for you to breathe properly on your own in a sleep-like state.

You may need to use a respirator for a while during the operation:

1. During the operation. The ventilator can temporarily breathe for the patient while the patient is under general anesthesia.
2. During recovery from surgery. Sometimes, in very complex operations, a patient may need a respirator to help him breathe for hours or more after surgery.

See also: Most patients survive the anesthesia

How long should I be on a ventilator?

A ventilator can save lives, but its use is risky. It does not solve the problem that led a person to need a respirator; it simply helps the patient until other treatments become effective or the patient recovers on their own. Doctors always try to help patients disconnect from the ventilator as soon as possible.

“Weaning” refers to the process of disconnecting the patient from the ventilator. Some patients may only use the ventilator for a few hours or days, while others may require a longer ventilator. How long a patient needs to be connected to a ventilator depends on many factors. These can include overall strength, pre-ventilator lung health, and the number of other organs involved (such as the brain, heart, and kidneys). Some people will never get better enough to be disconnected from a ventilator.

See also: What is the disconnection from life support equipment in Poland?

How does a respirator work?

In its simplest form, a modern respirator consists of a compressed air tank or turbine, air and oxygen sources, a set of valves and tubing, and a disposable or reusable “patient circuit”. The air reservoir is pneumatically compressed several times per minute to provide the patient with room air or, in most cases, an air / oxygen mixture. If a turbine is used, it forces air through the ventilator equipped with a pressure regulating flow valve to meet patient-specific parameters. When the pressure is released, the patient will exhale passively due to the flexibility of the lungs, and the exhaled air is usually released through a one-way valve in the patient circuit called the patient’s manifold.

The ventilators can also be equipped with systems for monitoring and alerting parameters related to the patient (e.g., pressure, volume, and flow) and ventilator functions (e.g., air leak, power failure, mechanical failure), backup power, oxygen tanks, and remote control. The pneumatic system is now often replaced by a computer controlled turbo pump.

Modern ventilators are electronically controlled by a small built-in system that allows the pressure and flow characteristics to be fine-tuned to the individual patient’s needs. Finely tuned ventilator settings also serve to make ventilation more bearable and comfortable for the patient. Depending on the type of ventilation needed, the end of the patient circuit can be non-invasive (mask) or invasive (tube).

Respirator with a face mask

Using a face mask to deliver oxygen to the lungs is known as non-invasive ventilation.

With this type of ventilation, a fitting plastic mask is put on the nose and mouth. A tube will be attached to the mask forcing air into the lungs. This method is usually used in cases where breathing problems are less severe.

This method has several advantages.

1. It is more convenient than using a tube that passes through the throat;
2. Does not require sedation;
3. It allows you to talk, swallow and cough;
4. It can lower the risk of side effects and complications, such as infection and pneumonia, which are more common with ventilation through an endotracheal tube.

Respirator with endotracheal tube

In more severe cases, the patient will need an endotracheal tube in the throat and in the windpipe. This is called invasive ventilation. Typically, the patient will be given sedation prior to performing this procedure as it may cause pain and discomfort.

The endotracheal tube and the respirator perform different tasks. The ventilator forces a mixture of air and oxygen into the patient’s lungs to deliver oxygen to the body. The ventilator can also maintain a constant low pressure value, known as positive end expiratory pressure (PEEP), to prevent air bubbles in the lungs from collapsing. The endotracheal tube allows doctors and nurses to suck mucus out of the trachea.

If a patient has been diagnosed with an obstruction of the trachea, for example due to a tumor, or needs a respirator for a long time, they may need a tracheostomy surgery. During a tracheostomy, the surgeon makes a hole in the patient’s neck and windpipe and then inserts a breathing tube called a tracheostomy tube into the opening. The tracheostomy tube is then attached to a ventilator. The tracheostomy tube can remain in the patient’s body for as long as it is needed, but it does not have to be there permanently, and can be removed if the patient no longer needs it. You can talk and eat with a tracheostomy tube.

Respirator – types

The following can be mentioned among the types of respirators.

1. Stationary respirators – found in many variants. Depending on the model and manufacturer, they have various additional functions. They are used in hospital wards. 
2. Ambulance / transport respirators – their characteristic feature is high resistance to shocks and size, because they are much smaller than their stationary counterparts. However, this is not all, because these respirators are also adapted to work in difficult conditions (they are resistant to water and frost). They support the patient’s breathing during their transport to the hospital by ambulance or emergency helicopter. 
3. Neonatal respirators – designed especially for newborns, they operate in an appropriate operating mode for the ventilation of the youngest patients. What’s more, they also fit most types of incubators. This is one of the few devices in pathology and neonatal intensive care units.

Respirator – operating modes

Respirators can operate under various operating modes, among which the following can be mentioned:

1. respiration SIMV synchronized intermittent mandatory ventilation – guarantees a specific number of breaths, but the patient’s breaths are partially self-contained, reducing the risk of hyperinflation or alkalosis. Mandatory breaths are synchronized with spontaneous breaths. The disadvantages of SIMV are increased respiratory work and a tendency to reduce cardiac output, which can prolong ventilator dependency. Adding pressure support to spontaneous breaths may reduce some of the breathing work. SIMV has been shown to reduce cardiac output in patients with left ventricular dysfunction.
2. PSV respiration (pressure support ventilation) – allows the patient to determine the inflation volume and respiratory rate, therefore it can only be used to support spontaneous breathing. Pressure Support can be used to overcome the resistance of the ventilator tubing in the next cycle or to assist in spontaneous breathing. This mode is used thanks to specialized face masks.
3. PCIRV respiration (pressure controlled inverse ratio ventilation) – a pressure controlled ventilation mode where most of the time is spent at a higher (inspiratory) pressure. While early studies were promising, the risk of auto PEEP and haemodynamic deterioration due to shortened exhalation time and increased mean airway pressure generally outweighs the small potential for improved oxygenation.
4. APRV respiration (airway pressure release ventilation) – is a variation of CPAP (continuous positive airway pressure), which temporarily releases pressure during exhalation. This unique ventilation mode results in a higher mean airway pressure. Patients are capable of spontaneous ventilation at both low and high pressure, although typically most (or all) of the ventilation is done at high pressure. In the absence of breath samples, APRV and PCIRV are identical. As in PCIRV, a hemodynamic problem is a problem in APRV. Additionally, APRV usually requires increased sedation.
5. PEEP respiration (positive end expiratory pressure ventilation) – A method of ventilation in which airway pressure is kept above atmospheric pressure at the end of exhalation by a mechanical impedance, usually a valve, in the circuit. The goal of PEEP is to increase the volume of gas remaining in the lungs at the end of exhalation to reduce blood flow through the lungs and improve gas exchange. PEEP is performed in ARDS (acute respiratory distress syndrome) to allow the oxygen administered to decrease.
6. CPAP respiration (continuous positive airway pressure) – is a form of positive airway pressure ventilation (PAP) in which a constant pressure level, higher than atmospheric pressure, is constantly applied to the upper respiratory tract. The use of hypertension may be aimed at preventing the collapse of the upper respiratory tract, which occurs in obstructive sleep apnea, or at reducing respiratory function in conditions such as acute decompensated heart failure. CPAP therapy is very effective in treating obstructive sleep apnea.
7. CMV respiration (continuous mandatory ventilation) – in this mode, each breath is performed by the ventilator for the patient. The patient can also take additional breaths. They must have the parameters indicated by the ventilator. 
8. respiration AMV (assisted mechanical ventilation), assisted mechanical ventilation – this mode is based on the positive respiratory pressure generated.  
9. respiration IMV Intermittent mandatory ventilation – this mode is usually used in premature babies and newborns. The principle of operation is that the ventilator performs some of the breaths, and in between the mechanical action of the ventilator, the newborn can also breathe independently. However, it is very important that your own breathing does not conflict with the respirator’s breathing. 

What to expect when connected to a ventilator?

The ventilator itself does not cause pain, but the tube that is used to connect the patient to the ventilator can cause discomfort as it may cause a cough reflex or a gag reflex. The patient is unable to speak as the endotracheal tube passes between the vocal cords into the trachea. He also cannot eat orally while the tube is in place (if a respirator is used with a mask, we will likely be able to talk, swallow, and cough).

You may feel uncomfortable when air is being pushed into your lungs. It also happens that the patient is trying to exhale as the ventilator is trying to draw in air. This behavior It works makes it difficult for the ventilator to operate.

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Respirator and medications

People on respirators may be given medication (tranquilizers or painkillers) to make them feel more comfortable. These drugs can also make you feel sleepy. Medications that temporarily prevent muscle movement (depolarizing muscle relaxants) are sometimes used to allow the ventilator to do all the work for the patient. These drugs are usually used when a person has very severe lung trauma; their administration is stopped as soon as possible and always before disconnecting the ventilator from the patient.

The ventilator and monitoring of the patient’s condition

Most ventilator patients are monitored in the intensive care unit. Anyone using the ventilator in the intensive care unit will be connected to a monitor that measures heart rate, respiratory rate, blood pressure and oxygen saturation (“sat O2”). Other tests that may be performed include a chest x-ray and a blood draw to measure oxygen and carbon dioxide (“blood gases”).

Healthcare team members (including doctors, nurses) will use this information to assess the patient’s condition and make adjustments to the ventilator as needed.

See also: Anesthesiologist: unvaccinated, young people without any other diseases dominate in intensive care

Risk of connecting to a ventilator

A respirator can save our lives. However, like other treatments, it can cause potential side effects. This is more common when we use a respirator for a long time.

Some of the most common risks of being under a respirator include the following problems and ailments.

1. Infection. This is one of the major hazards of being under a respirator with the use of an endotracheal tube. The accumulation of fluid and mucus in the throat and trachea can allow germs to build up in the respiratory tract. These germs can then travel to our lungs. This can increase your risk of developing pneumonia. Sinus infections are also common with an endotracheal tube. We may need antibiotics to treat pneumonia or sinus infections.
2. Irritation. The airway can rub and irritate the throat or lungs. It can also make coughing harder, which helps to get rid of dust particles and irritants from the lungs.
3. Problems with the vocal cords. The endotracheal tube passes through the larynx where the vocal cords are located, which is the reason why you cannot speak when using a respirator. The endotracheal tube can damage the larynx.
4. Collapsed lung (pneumothorax). Occasionally, part of the lung may become weakened, creating a hole allowing air to leak and causing the lung to collapse. If the collapse of the lungs is severe enough, it can be fatal. To re-expand the lung, place a tube in the chest to help remove any leaking air. After the lung has healed, the tube can be removed.
5. Blood clots. Lying in the same position for a long time may increase the risk of a blood clot.
6. Side effects of drugs. Sedatives and pain relievers can make the patient appear confused or delirious (side effects may still affect the patient after stopping the medication). The healthcare team tries to adjust the right amount of medication for a person. Different people will react differently to each drug. If you need medication to prevent muscle movement, your muscles may feel weak for some time after you stop taking the medication. This may improve over time. Unfortunately, in some cases, muscle weakness lasts for weeks to months.
7. Nerve and muscle damage. Lying down for many days, taking sedatives, and not breathing on your own can result in nerve and muscle disorders.
8. Fluid retention. It can be caused by continuous infusions, drug toxicity, and renal failure.
9. Lung damage. The pressure of air introduced into the lungs by a respirator can damage the lungs. Doctors try to keep this risk to a minimum by using the least amount of pressure needed. Very high levels of oxygen can also be harmful to your lungs. Doctors only give as much oxygen as needed to make sure the body is getting enough oxygen to supply vital organs. Sometimes it is difficult to reduce this risk when the lungs are damaged. However, this damage can improve if a person is able to recover from a serious illness.
10. Inability to disconnect from a respirator. Sometimes the disease that caused the patient to require a ventilator does not go away despite treatment. When this happens, your healthcare team will discuss treatment issues with the continued use of the ventilator. Often times, the health care team will have these discussions with family members or with the patient if they are able to participate. In situations where a patient fails to recover or worsens, a decision may be made to discontinue use of the ventilator and allow the patient to die.

See also: How to help yourself with COVID-19? Respiratory hygiene is important

What to expect when disconnected from a ventilator?

If you use the respirator for a long time, it may be difficult to breathe on your own when the ventilator is no longer breathing for you.

It may turn out that after disconnecting the ventilator, the patient experiences a sore throat or the muscles of the chest weaken. This can happen because the muscles around the chest weaken as the ventilator does the work of breathing for us. Medications that we receive while using a respirator can also contribute to muscle weakness.

Sometimes it may take days or weeks for the lungs and chest muscles to return to normal. Your doctor may then advise you to slowly stop the ventilator. This means that the patient will not be completely disconnected from the ventilator. Instead, it will gradually move away from him until his lungs are strong enough to breathe on his own without the aid of the device.

If you have pneumonia or any other infection from using the ventilator, you may still feel unwell after disconnecting it. You should tell your doctor if you feel worse or develop new symptoms, such as a fever.

If you use a respirator for a long time, many of the muscles in your body will be much weaker than they used to be. Moving freely and carrying out everyday activities can prove challenging. The patient may then need physical therapy to regain their former muscle strength and be able to return to normal everyday life.

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