Overview of Ventilator Weaning
Mechanical ventilation is a commonly used method to support patients who are having trouble breathing. While it can be extremely beneficial, it’s not without risks. Long-term use of mechanical ventilation can increase chances of developing pneumonia, lung injury, injuries to the windpipe, and muscle weakness. Also, delaying the process of getting patients off the ventilation can lead to more serious health risks, longer hospital stays, and greater chance of needing long-term care.
Luckily, for about 70% of patients, the process of getting off the ventilator, also known as “weaning,” goes smoothly. This typically involves removing the ventilator (extubation) once the patient has successfully passed their first spontaneous breathing trial. However, for 30% of patients, this process can be more challenging, especially for those dealing with certain lung diseases, heart failure, or neuromuscular disorders.
It’s worth noting that nearly half of the time spent on the ventilator is dedicated to the weaning process. Here, we will discuss some of the common issues that can make it difficult to wean a patient off a ventilator, as well as the various tools doctors use to determine when a patient is ready to be extubated.
Anatomy and Physiology of Ventilator Weaning
Respiratory insufficiency, or the inability to breathe properly, is a common problem that usually prevents people from being able to be taken off a ventilator. This problem happens when the patient’s ability to breathe isn’t enough to meet their body’s demands.
In some cases, the use of a ventilator for an extended period, particularly if it is not regularly used by the patient, can cause the diaphragm to become weak or even shrink in size. Other things can also lead to weak respiratory muscles. These include taking too many steroids, sedatives, muscle relaxants, suffering from a disease that weakens the muscles, sepsis-related inflammation, not eating enough, and not moving. These factors often occur together in patients who are staying in the Intensive Care Unit (ICU), creating a cycle where getting weaker makes it harder to get off the ventilator, which leads to a longer stay in the ICU.
Heart failure is another obstacle that can make it difficult to stop using a ventilator. When people transition from using a machine to breathing on their own, significant changes happen in the body. Most notably, they lose the positive pressure in their chest that the ventilator was providing. This increases the amount of blood returning to the right side of the heart and puts more stress on the heart. This is particularly important for people in the ICU, who often have a positive fluid balance, meaning they have a higher than normal amount of fluid in their body. The increased work for the heart can lead to higher oxygen demands and put people with heart disease at risk of a heart attack.
How is Ventilator Weaning performed
There are many challenges to safely ending a patient’s need for mechanical ventilation, or the assistance in breathing via a machine. The goal is to properly time when a patient should stop using the ventilator, ideally within 24 hours of meeting the necessary conditions, and avoiding stopping too early or too late.
The process of weaning a patient off the ventilator involves several steps, including:
- Initiating intermittent mandatory ventilation (IMV) once the patient is ready. This means the machine will still assist in breathing, but allows for periods of normal breathing.
- Allowing the patient to breathe on their own for at least 30 minutes.
- Conducting a cuff-leak test, which is performed to check if the patient’s airway will stay open after the ventilator is removed.
The most important part of this process is carefully determining when the patient is ready to start being taken off the ventilator assistance.
Despite the risks of using mechanical ventilation for too long, some patients may continue using it for longer than necessary. This is because clinicians might underestimate a patient’s readiness to wean off mechanical ventilation. For example, patients who manage to take the tube out themselves often don’t need it put back in, indicating they could have been taken off the ventilator earlier.
This is why it is recommended to use certain protocols for assessing everyday if a patient is ready to try breathing on their own. However, there are certain things to consider before starting this process:
- Has the patient’s illness that required ventilation gotten better or gone away entirely?
- Is the patient stable in terms of blood circulation, without needing drugs to control blood pressure or serious heart rhythm problems?
- Is the patient getting enough oxygen?
- Is the patient awake and able to communicate properly?
While these factors certainly play a role, their presence or absence does not completely predict the success or failure of taking a patient off ventilation. This is why objective measures for readiness are needed. Some of these measures assess how much oxygen the patient needs, the strength of the respiratory muscles, and other aspects related to breathing.
Deciding when and how to take a patient off a ventilator is complicated and requires considering multiple factors. One commonly-used measure is the rapid shallow breathing index (RSBI), defined as the ratio of the rate of breathing (breaths per minute) to the amount of air breathed in with each breath (tidal volume). An RSBI less than 105 usually indicates the patient will succeed in breathing without the ventilator, while a score above 105 often means the patient will need the ventilator for longer.
Other tools can also be used to aid in the process and increase the chances of success. These include ultrasound to assess the movement and thickness of the diaphragm, which is the main muscle for breathing, checking the pressure in the airways, and delaying medications that make patients sleepy. Other factors, like the frailty of the patient and certain biochemical tests, can also give valuable information on the patient’s readiness to be weaned off the ventilator.
Possible Complications of Ventilator Weaning
If you’re on a respiratory machine (mechanical ventilation) in an ICU, doctors will do daily checks to see if you’re ready to stop using it. They do this with tests, like spontaneous breathing trials (SBT), if you meet certain health conditions. The key thing is to lower the amount of help you’re getting from the machine, typically using a setting called pressure support ventilation where the breaths it gives you aren’t as strong.
In some cases, you might get taken off the ventilator altogether for the test, with the help of something called a zero PEEP trial. If you make it without needing the machine for at least 30 minutes, and your vital signs stay stable (breathing rate less than 35, blood pressure okay, oxygen levels over 90%), the trial is considered a success. Doctors will also factor in how well you’re able to stay awake, handle respiratory secretions (like if you need to cough, for example), and whether you seem anxious or distressed. If it goes well, they’ll check for an air leak around the breathing tube (a cuff leak test) and look to take it out permanently.
If you’re not successful during this process, doctors will go through their findings carefully to figure out why it didn’t work and provide the necessary intervention you need to get better. The professional judgement of the healthcare team that’s looking after you is incredibly important during this process.
Sometimes, even if you’re not able to complete a spontaneous breathing trial, the medical team may still go ahead and remove your breathing tube (extubation) and support you using a mask-based (non-invasive) breathing machine. This technique is recommended by major health bodies for certain groups, such as elderly patients, patients with specific chronic respiratory conditions, and those who have a high carbon dioxide level. This has been shown to decrease time spent in the ICU for these patients.
If you don’t pass the spontaneous breathing trial, doctors can adjust the ventilator settings to gradually help you breathe on your own. There are various different methods that can be used based on your needs and clinical judgment of the health care team. The goal is to support your body’s effort to breathe on its own. This is approached carefully, focusing on the fundamental aspects of getting the right patient at the right time for the weaning process.
What Else Should I Know About Ventilator Weaning?
Weaning is the process of taking a patient off of a ventilator, a machine that helps them breathe, and letting them start breathing on their own again. Sometimes, weaning doesn’t go as planned, and there are a few common reasons for this:
- Cardiac dysfunction: This means the patient’s heart isn’t working as well as it should.
- Cognitive dysfunction: This means the patient is having trouble thinking clearly.
- Respiratory pump failure: This means the organs that help the patient breathe aren’t working properly.
- Respiratory muscle and diaphragmatic dysfunction: This means the muscles that help the patient breathe, including a muscle called the diaphragm, aren’t working as they should.
- Metabolic disorders: These are conditions that affect the way the body converts food into energy.