Overview of Noninvasive Ventilation
Non-invasive ventilation (NIV), a kind of breathing support that doesn’t require a tube in the windpipe, has a history that goes back to the 18th century. It was first reported by a Scottish doctor named John Dalziel. In 1864, Alfred F. Jones patented the first American tank respirator, a device that could help people breathe without a surgical procedure.
In 1938, a new form of NIV was introduced to treat a condition called pulmonary edema (fluid build-up in the lungs). Even earlier, in 1878, a different type of pressure was added to NIV by a doctor named Oertel to help with breathing difficulty. It’s called intermittent positive pressure.
During the polio epidemic, when the mortality rate was very high (over 80%), an anesthesiologist from Copenhagen, named Bjorn Ibsen, introduced positive pressure ventilation which was applied via a small hole in the windpipe. This method was effective, reducing the mortality rate to nearly 40%, but it required manual effort since there were no machines available to provide this type of ventilation at the time.
In the past 100 years, positive pressure ventilation has greatly improved and is now commonly used to help patients with breathing failure. It has proven to be effective in preventing the need for a breathing tube when compared to standard oxygen therapy in an emergency situation. One of the most common forms of this treatment is the Bilevel Positive Airway Pressure (BPAP).
Recent guidelines from American Thoracic Society/European Respiratory Journal support the use of NIV for acute flare ups of chronic obstructive pulmonary disease (long-term lung disease) and acute respiratory failure caused by fluid build-up in the lungs. Evidence and recommendations also support the use of NIV in other situations of acute respiratory failure, such as after surgery or chest injury. Several studies also show that NIV can be beneficial in various long-term lung diseases.
Anatomy and Physiology of Noninvasive Ventilation
Lung compliance is a fancy medical term that refers to how easily our lungs expand and contract with every breath we take. It’s a bit like how easily a balloon inflates when you blow into it. This is calculated using a formula that takes into account the volume of the lungs and the pressure within them.
The lung’s pressure is what keeps it from collapsing on itself, kind of like the air inside the balloon keeps the balloon from deflating. When we breathe in, our diaphragm muscle contracts, lowering the pressure inside our lungs and making them expand.
Just like there are different types of balloons – some blow up easily whereas others need more force – there are variations in lung compliance, depending on the health of our lungs. Lung diseases can impact this. For instance, emphysema, a lung condition that damages the air sacs in your lungs, makes it harder for the lungs to expand and contract. This is like having a balloon that’s harder to inflate – even with a lot of pressure, it doesn’t increase much in size.
In contrast, conditions like acute respiratory distress syndrome and fluid in the lungs due to heart problems, can make the lungs too flexible like a very thin balloon. This happens because the fluid filled air sacs stretch the lungs too much.
To help with these situations, doctors use a non-invasive method called NPPV which stands for noninvasive positive pressure ventilation. This method applies extra pressure to the lungs to make it easier for them to inflate and deflate, reducing the effort it takes to breathe.
By using this technique, doctors can provide relief to patients and help them breathe easier even when the lungs are not at their best.
Why do People Need Noninvasive Ventilation
Based on the 2020 guidelines laid out by the American Thoracic Society and the European Respiratory Society, a therapy called Noninvasive Positive Pressure Ventilation (NPPV) is strongly recommended for people experiencing severe breathing difficulties, also known as acute respiratory failure (ARF).
Using a device known as Bi-level Positive Airway Pressure (BPAP) is recommended for individuals suffering from severe or sudden breathlessness and raised acidity levels in the blood due to severe flare-up of Chronic Obstructive Pulmonary Disease (COPD). In medical terms, it’s known as acute or acute-on-chronic respiratory acidosis where the pH level is 7.35 or lower.
If a patient is not immediately deteriorating, BPAP can be used to prevent the need for a machine to take over their breathing via a tube inserted into their windpipe, known as endotracheal intubation and mechanical ventilation.
Moreover, BPAP or Continuous Positive Airway Pressure (CPAP), another type of breathing device, can help individuals suffering from fluid build-up in the lungs due to heart problems, a condition called cardiogenic pulmonary edema.
The same sources suggest that NPPV can also benefit certain other groups of patients with acute respiratory failure, although these recommendations are more conditional. This includes patients with weakened immune systems, individuals who have had recent surgery, people in the final stages of cancer or other terminal illnesses who are troubled by shortness of breath, patients with chest injuries, and high-risk patients to prevent post-extubation respiratory failure, a complication after removal of the breathing tube.
In addition to acute situations, NPPV has also proven beneficial for chronic respiratory diseases. That includes long-term stable COPD conditions with increased carbon dioxide in the blood (hypercapnia), obesity hypoventilation syndrome, a condition that causes poor breathing during sleep in obese individuals, obstructive sleep apnea, a disorder that involves repeated stops and starts in breathing while sleeping, breathing difficulties due to nerve and muscle diseases, and restrictive thoracic disorders, conditions where the chest muscles can’t expand fully.
When a Person Should Avoid Noninvasive Ventilation
Some conditions make it completely unsafe for certain medical procedures to be performed. These include:
* Injuries or burns to the face
* A blockage in the upper part of your airway that cannot be removed
* Constantly throwing up
* If a person’s heart or breathing has stopped
Some conditions, while not making it completely impossible, still make the procedure more risky. These include:
* Recent surgery to the face, upper airway, or upper part of your digestive system
* If a person might breathe something into their lungs that they shouldn’t, such as vomit
* Very low oxygen levels in the blood that pose a threat to life
* If a person’s overall health condition is unstable due to factors such as very low blood pressure, a heart attack that needs immediate intervention, unchecked lack of blood flow to the heart or irregular heart rhythms
* If a person is confused or agitated
* A blockage in your intestines
* A lot of fluids in the lungs
* A certain area of the lung is solid and inflamed
* A pocket of air in the chest that is not drained
* Very serious health problems at the same time
Equipment used for Noninvasive Ventilation
The parts that make up a non-invasive positive pressure ventilation (NPPV) machine are:
First, the NIV device. This machine uses different kinds of modes to help patients breathe properly. One of these is continuous positive airway pressure (CPAP), which provides a steady flow of air to keep airways open. Another is bilevel positive airway pressure (BPAP). BPAP uses two modes: Spontaneous and Spontaneous/Timed (S/T). The Spontaneous mode boosts the patient’s own breathing, while the S/T mode offers a backup breathing rate which is slightly slower than the patient’s own rate.
Modern NPPV devices have more features to monitor and assist with breathing. They include something called averaged volume-assured pressure support (AVAPS). AVAPS helps deliver a consistent volume of air to the patient in each breath. It uses a specific system to automatically determine and adjust the pressure needed to maintain the ideal volume of air for each breath. Additionally, AVAPS can be paired with auto–expiratory positive airway pressure (AVAPS-AE) to help keep a patient’s upper airways open.
BPAP S/T mode and AVAPS have some differences. BPAP S/T mode has a fixed pressure, while AVAPS has a minimum and maximum pressure. AVAPS also offers the feature of Auto PS, which means it automatically adjusts the patient’s pressure support.
Aside from the NIV device, there are many kinds of masks to choose from, such as nose masks, nose-mouth masks, and helmets. Each type of mask has its own pros and cons.
The NPPV circuit also includes tubing, an oxygen supply, a power supply, and a humidifier to increase the moisture content of the air used for ventilation.
Who is needed to perform Noninvasive Ventilation?
Non-invasive positive-pressure ventilation (NPPV – a way of helping your breathing without using a tube) should be started and adjusted by doctors who have a lot of experience with it and who know how to watch and control it closely. These doctors often come from different fields such as internal medicine, anesthesiology (they help with managing pain or putting you to sleep), surgery, emergency medicine, lung health, and critical care. Having a team that knows the device and can handle any issues is very important during this process. This team is usually made up of respiratory therapists (professionals who specialize in breathing problems) or nurses who have a lot of experience in critical care. They all work together to make sure your breathing is helped in the best way possible.
How is Noninvasive Ventilation performed
Starting noninvasive positive-pressure ventilation, or NPPV, requires careful planning. NPPV helps patients who have difficulty breathing to get enough air. The patient, the type of mask, and the ventilator equipment have to be chosen carefully. For the procedure to work, the patient needs to cooperate and understand what’s happening, so everything should be explained to them clearly. Once this is completed and the mask fits well, the ventilator is connected and switched on.
The ventilator settings must be adjusted carefully, according to protocols that doctors use. This is done with the help of nurses and respiratory therapists and must be monitored closely. The specific protocols depend on the situation and the issue that the patient is facing. Keeping an eye on the effectiveness of the treatment is crucial, especially considering the patient’s comfort and their body’s responses.
In an emergency setting, the respirator settings are adjusted based on the patient’s condition. Patients with sleep apnea, a condition causing them to stop breathing during sleep, may need to have the ventilator pressure adjusted based on their body weight. In patients with high levels of carbon dioxide in their blood (hypercapnia), like in acute COPD (a lung disease causing difficulty in breathing), doctors may raise the pressure support to help reduce carbon dioxide levels.
In seriously ill patients with both hypercapnia and sleep apnea, settings require careful balance so that the patient can breathe sufficiently and comfortably without collapsing their airways. Once the patient has got adjusted, the pressure can then be slowly reduced. At the same time, doctors need to ensure patient’s comfort and the correct function of the respirator. They need to make sure the patient’s blood pressure and heart rate stay stable.
Chronic conditions also require careful adjustments of the ventilator settings. In COPD patients with high levels of carbon dioxide, noninvasive ventilation improves survival and reduces symptoms, especially when a high-intensity pressure support is used. The goal of the treatment is to lower or normalize the carbon dioxide levels. Specific titration protocols are used in obesity hypoventilation syndrome, a condition where obese people have low oxygen levels and high carbon dioxide levels in their blood during sleep. If there are signs of obstructive sleep apnea, adjustments in the positive airway pressure need to be made.
For patients with thoracic restrictive disorder, a group of diseases that weaken the muscles making breathing difficult, similar protocols are used. The treatment regimen of NPPV needs to be customized to each individual patient based on their specific condition and monitoring their blood gas levels and oxygen levels. Regular follow-ups and check-ups are needed to make sure the treatment is effective and working well for the patient.
Possible Complications of Noninvasive Ventilation
When undergoing non-invasive positive pressure ventilation (NPPV), which is a type of breathing support given using a face mask, some common complications can arise. The most usual issue tends to be a discomfort with the mask. More serious side effects can include a skin rash due to an allergic reaction or infection, and more rarely, pressure sores on the bridge of your nose. Other complications may include Aerophagia, which is excessive swallowing of air leading to bloating, and sialorrhea, which is excessive saliva production.
Sometimes, people might feel uneasy due to pressure-related side effects such as discomfort, ear and sinus pain, or gastric insufflation, which is the presence of excessive air or gas in your stomach or intestinal tract. Serious side effects from pressure can include pneumothorax, which is a collapsed lung, Pneumocephalus, which is air or gas within your cranial cavity, and pneumomediastinum, which is air or gas in the middle part of your chest. These are particularly seen in patients with COVID-19 pneumonia using NPPV.
Aspiration, which is when food, stomach acid or saliva is inhaled into the lungs, is another serious complication of NPPV. Selection of suitable patients who are at low risk of aspiration is crucial when planning NPPV treatment. Sedation hasn’t been extensively studied for NPPV because it’s thought to increase the aspiration risk and lead to slowed or labored breathing.
Occasionally, in patients with both breathing problems and weakened heart function, NPPV can cause a drop in blood pressure. This is due to increased pressure inside the chest, increased pressure on the right side of the heart after it pumps, and less blood returning to the heart before it pumps.
Finally, some patients may face an issue when the assisted breathing system doesn’t match their own breathing rhythm, which can lead to trouble exchanging oxygen and carbon dioxide. This can cause unnecessary strain on your breathing muscles. Such problems can occur in two ways; either due to an inability to adequately switch from inhaling to exhaling, which can often occur in a COPD condition, or there can be a failure to trigger the device to give an assisted breath. This can be seen in neuro-muscular diseases such as ALS, where the patient can’t generate enough pressure during inhalation to start the assisted breathing.
What Else Should I Know About Noninvasive Ventilation?
Respiratory failure is a severe condition that can endanger your life, causing about 30% of hospital deaths. The typical treatment for respiratory failure is to put a tube in the throat and provide artificial breathing with a machine (this is called mechanical intubation and ventilation). However, this treatment can involve many risks. For example, inserting the breathing tube can cause issues like spasms in the voice box or airways, incorrect placement of the tube, inhaling food or liquid into the lungs, and a sudden drop in blood pressure. Being on a breathing machine for a long time can also injure the lungs, cause pneumonia, or lead to issues with the digestive system, such as stomach ulcers and harmful bacteria in the gut.
Using a different type of breathing support, called NPPV (non-invasive positive pressure ventilation), has been shown to decrease the need for a breathing tube in various conditions such as COPD (a lung disease that causes breathlessness), heart-related lung fluid buildup, and pneumonia. It could also be used to prevent the need for re-inserting the breathing tube in patients with increased carbon dioxide levels in their blood. Yet, NPPV takes time and resources, and should only be done by clinicians and health staff who are experienced in its use.
A few key things to remember:
– Start treatment as soon as possible.
– If your blood is more acidic (arterial pH less than 7.35) than usual and there’s high carbon dioxide level, this shows that you might have acute or chronic hypercapnia respiratory failure which might require intensive care treatment.
– The initial focus is to normalize the acidity level of blood in patients with this form of respiratory failure.
– High-intensity pressure support (which treats respiratory failure by providing positive pressure) is necessary if there are very high levels of carbon dioxide in the blood. Its aim is to either normalize carbon dioxide or lower it by 20% from the earlier levels.
– If obstructive sleep apnea (a condition causing pauses in breathing while sleeping) is suspected, a certain level of positive airway pressure (10% of actual body weight) should be adjusted, especially if there has been no other airway pressure adjustment done.