Overview of Adaptive Support Ventilation
Adaptive support ventilation (ASV) is a modern kind of mechanical ventilation, a process to help a person breathe using a machine. It was introduced in the Galileo ventilator, a device made by Hamilton Medical, in 1994. A doctor named Hewlett first brought it up in 1977. He described it as mandatory minute ventilation (MMV), a method of supporting breathing with pressure control that can change as needed. The person who gets the credit for this invention is Dr. Fleur T Tehrani. She used a revised Otis equation to create this technology.
The reason ASV is also known as the “no mode”, “integrated mode”, or “three in one way” is due to its unique characteristic of changing its settings based on the patient’s needs, which is not commonly found in other mechanical ventilation processes. Other types of mechanical ventilation include proportional assist ventilation (PAV), neurally adjusted ventilatory assistance (NAVA), and knowledge-based systems (KBS).
Why do People Need Adaptive Support Ventilation
Adaptive support ventilation (ASV) is a type of breathing support that has several advantages. One of these is the ability to recognize when a patient starts to breathe on their own more quickly. Research has found that ASV can help patients get off breathing support quicker, requires fewer adjustments, and triggers fewer alarms compared to traditional breathing support methods.
How ASV works is by seamlessly transitioning between two modes. When a patient isn’t breathing on their own, it uses pressure control ventilation. But when the patient starts to breathe spontaneously, it switches to adaptive pressure support ventilation. This has led to quicker recovery times in patients with chronic obstructive pulmonary disease (COPD) in various clinical trials.
ASV is also flexible; it can be used at any point when a patient is on a breathing machine, from the moment a tube is placed in their airway (intubation) to the moment it is removed (extubation).
Different methods have been tested in using ASV to improve patient outcomes after heart surgery. For instance, after elective coronary artery bypass grafting — a type of heart surgery to improve blood flow to the heart — a study compared two weaning strategies for ASV. The study found that gradually reducing the target minute ventilation (the amount of air a patient breathes in a minute) had better outcomes. Patients recovered quicker and were able to leave the hospital earlier than those who had a constant target minute ventilation. This also led to better quality of life and lower hospital costs for patients who used ASV with this method.
When a Person Should Avoid Adaptive Support Ventilation
There are some situations when it’s not advisable to use a type of breathing therapy called adaptive support ventilation (ASV). Unfortunately, individuals who are obese or have just had major heart or lung surgery may find it hard to use ASV. This is because these individuals may have difficulty maintaining the right amount of air in their lungs after each breath, a situation known as low functional residual capacity (FRC). People who frequently lose air from their lungs, or ‘derecruit’, might be at a higher risk. Those who suffer from restrictive lung disease typically need smaller amounts of air flow during each breath.
An additional limitation of ASV is that it’s only available on one type of breathing machine called Hamilton ventilators. If you use a different breathing machine, then you won’t be able to use ASV. One more potential issue with ASV is that it doesn’t allow you to manually adjust the volume of air or the rate of breaths. However, in certain situations like hypercapnic respiratory failure (when you have too much carbon dioxide in your blood), you might need to change these settings.
Equipment used for Adaptive Support Ventilation
Adaptive support ventilation (ASV) is a sophisticated form of breathing support for people who cannot breathe independently. Mechanically controlled, ASV uses a system of interactive controls linked to a computerized processor. These controls assess the person’s breathing and make any necessary adjustments in real-time during each inhaled and exhaled breath. It then tailors the support according to the individual person’s need to ensure optimal assistance.
ASV works by taking in data such as the person’s weight, height, and gender, and the desired amount of air needed per minute, calculated based on their ideal body weight (IBW). It combines all these details with real-time data from the ventilator, such as resistance and compliance, to provide the ideal setting unique to each person. This type of ventilator assistance can be used for patients with both short-term and long-term respiratory problems, and during the process of transitioning off the ventilator (weaning).
Key settings on ASV that are important to note include:
- Height – It’s needed to calculate the ideal body weight for optimal ventilator settings.
- Weight – It helps figure out the ‘dead space’ (the portion of each breath that doesn’t reach the lungs).
- Gender
- Minimum required volume of airflow, which varies based on medical conditions like Asthma or ARDS, body temperature, and altitude.
- Trigger – the base rate of airflow, set at 2 L/min.
- Expiratory trigger sensitivity – the initial setting range in patients with COPD is between 25% and 40%.
- Tube resistance compensation – it’s set fully at 100% to help with breathing ease.
- High-pressure alarm
- Positive end-expiratory pressure (PEEP) – additional pressure applied at the end of each breath to keep the lungs open.
- Fraction of inspired oxygen (FiO2) – the concentration of oxygen in the air the patient breathes.
Who is needed to perform Adaptive Support Ventilation?
Adaptive support ventilation (ASV) is a system that is very useful, especially when there aren’t enough respiratory therapists (these are specialists who assist patients with their breathing) in intensive care units. ASV uses automation, which means it can make small but important adjustments to a patient’s ventilator automatically without the need for a human to do it. Studies have shown that ASV leads to fewer alarms going off and less need for manual adjustments.
When a patient starts trying to breathe on their own, ASV automatically lowers the amount of breathing assistance, which is called “pressure support” (PS). This is important because sometimes these small changes in support are not noticed by non-automated systems or human operators, which can slow down the process of getting the patient off the ventilator. With ASV, there is less reliance on specially trained people to look after a patient on a ventilator.
Preparing for Adaptive Support Ventilation
When doctors need to help a patient to breathe, they may use a method known as Adaptive Support Ventilation (ASV). This commonly comes into play for patients who are having trouble with their respiratory system or are under anesthesia. The goal of ASV, like other forms of ventilation, is to make sure the patient’s lungs are getting enough oxygen and removing carbon dioxide correctly. Here’s how it works in simpler terms:
ASV makes sure the conditions of the breath a patient takes in and releases are just right. Things like the volume of the breath, the level of pressure, and the amount of pure oxygen in the air are all adjusted based on the patient’s needs. If the patient is able to breathe on their own, the machine can help boost their efforts. If they can’t, the machine can take over altogether. The intention behind this function is to mimic the body’s natural breathing rhythm, reducing the strain on the respiratory muscles and encouraging the patient to resume spontaneous breathing where they can.
The patient’s underlying clinical condition is factored into the machine’s settings, to make sure the pattern of breathing provided is the most beneficial for their individual circumstances. It takes into account whether the patient can breathe independently and aims to prevent rapid breathing, excess pressure in the lungs, and too much “dead-space” air (the part of the breath that doesn’t participate in gas exchange). It’s shown to be a rather effective method when compared to other types of assisted breathing techniques. So, in essence, ASV is like a highly intelligent, adaptable support system for a patient’s lungs. This approach helps to prevent unnecessary stress and paves the way for the patient’s recovery.
Possible Complications of Adaptive Support Ventilation
The main purpose of a mode of treatment known as adaptive support ventilation (ASV) is to make sure that enough air gets to the small sacs in the lungs, reduce the effort required to breathe, and help the patient switch to the best breathing pattern. This type of ventilation does this by actively preventing damage to the lungs caused by too much pressure, too much volume, and trapping of air.
When too much air is pushed into the lungs during ventilation, it can harm the lung tissue. This happens through the deactivation of surfactant – a substance that helps the lungs inflate and reduces their susceptibility to damage – and an increase in the small blood vessels’ leakiness.
What Else Should I Know About Adaptive Support Ventilation?
1. Patients recovering from heart surgery often need help from a machine (ventilator) to breathe properly afterwards. A ventilation system called ASV (Adaptive Support Ventilation) is found to be as effective in helping these patients breathe on their own again as compared to other systems. The time to start breathing without the machine’s help (extubation) depends upon the patient’s condition after the surgery. Shorter times are preferred as it can lead to less time spent in the intensive care unit (ICU) and hospital, hence reducing costs. The ASV system is also found to have fewer alarms and requires fewer adjustments than other systems. This makes it more efficient for patients who have just undergone heart surgery.
2. People with long-term lung diseases that require help with their breathing can also benefit from the ASV system. It is found to be more cost-effective since it demands less personnel to be monitored.
3. There are specific lung conditions like Acute Respiratory Distress Syndrome (ARDS) where the patient’s lungs are severely damaged. The ASV mode of ventilation is beneficial in such cases since it can tune itself to adjust the airflow pressure, reducing the risk of lung injury compared to other modes.
4. In cases of severe Chronic Obstructive Pulmonary Disease (COPD), a condition that obstructs airflow from the lungs, either NIV (Non-invasive ventilation) or IPPV (Invasive positive pressure ventilation) can be applied. Research has shown that ASV ventilation is a good alternative to others with no significant differences in survival rate. It also resulted in fewer patients needing breathing tubes.
5. There isn’t much information available about the use of the ASV system for children’s conditions. However, few small studies and case accounts have reported positive results from its use.