Overview of Synchronized Intermittent Mandatory Ventilation
Synchronized intermittent mandatory ventilation, or SIMV, is a type of tool used in ventilators that helps the patient breathe. In this setup, the machine will pump a specific amount of air into the lungs a certain number of times, while still letting the patient take their own breaths. The machine tracks when the patient starts to take a breath and tries to match up, or “synchronize,” with that effort. This is unlike some other types of ventilators that take over all the breathing work for the patient. SIMV allows the patient’s breathing to influence how much air they get.
To help with the patient’s own breaths, a function called pressure support (PS) can be added. This PS gives some extra help to make the patient’s breaths bigger or deeper. SIMV has been in use since the 1970s, and it was first created to help patients who relied on ventilators to breathe, start breathing on their own again. It became very popular and, in the 1980s, nearly all hospitals preferred this method when trying to help patients stop using a ventilator.
Anatomy and Physiology of Synchronized Intermittent Mandatory Ventilation
Synchronized Intermittent Mandatory Ventilation, often just referred to as SIMV, is a mode that’s available on many breathing machines or ventilators. When SIMV was first created, they needed to add a special part to the ventilator, which they called a “tee-piece.” The “tee-piece” is a type of tube that is connected to a device used to create a fine mist of medicine. One end of the “tee-piece” is open to the air and connected to a place on the patient where a one-way valve is present.
This valve fits into a hole in another part of the ventilator knows as the “Y-piece.” When the ventilator is running, the valve closes and a set volume of air is delivered to the patient. But, when the patient breathes on their own, the valve opens, and the patient can inhale gas from the “tee-piece.”
Newer models of ventilators can provide SIMV without needing a “tee-piece”, thanks to the help of the machine’s computerised systems. This is done within a closed breathing system, which allows for easier delivery of ventilation and improved patient comfort.
Why do People Need Synchronized Intermittent Mandatory Ventilation
Synchronized intermittent mandatory ventilation, or SIMV, is often used to help patients gradually stop using a breathing machine (ventilator). From a health perspective, SIMV helps prevent a condition called respiratory alkalosis, which happens when you breathe out too much carbon dioxide. This can occur if the ventilator is doing too much of the work for your lungs. SIMV allows patients to breathe normally by letting their own lungs control the breathing process.
One thing to keep in mind with SIMV is, it can sometimes make breathing feel more difficult. To help with this, doctors can add something called ‘pressure support’ to the SIMV.
Breathing machines, also known as mechanical ventilators, are used in severe cases when a person’s lungs can’t bring in enough oxygen or expel enough carbon dioxide. Usually, this is the next step if non-invasive ventilation methods, which don’t require a tube in your windpipe, have not worked.
When a Person Should Avoid Synchronized Intermittent Mandatory Ventilation
Synchronized intermittent mandatory ventilation (or SIMV) is a type of tool used to help patients breathe. It can be set to automatically provide a certain number of breaths, each with a fixed amount of air (this is known as tidal volume). However, the patient can also take their own breaths if they have the strength to do it, with the amount of air they inhale determined by how hard they try.
The major advantage of SIMV comes into full effect when the patient is able to take their own breaths, not solely relying on the machine to breathe for them. This method of breathing support provides partial assistance, and the benefits are maximized when the patient has the ability to take spontaneous breaths.
Equipment used for Synchronized Intermittent Mandatory Ventilation
Synchronized intermittent mandatory ventilation is a mode of breathing support that needs a special kind of machine called a ventilator. This machine has to be programmed to work in this specific way.
Who is needed to perform Synchronized Intermittent Mandatory Ventilation?
Just like with any other way of using a machine to help you breathe, known as mechanical ventilation, using SIMV (Synchronized Intermittent Mandatory Ventilation) requires trained respiratory therapists. These trained therapists closely watch and adjust the machine that’s helping you breathe. Additionally, a doctor will oversee the whole process to ensure everything runs smoothly and safely.
Preparing for Synchronized Intermittent Mandatory Ventilation
Getting ready for the breathing support known as SIMV (Synchronized Intermittent Mandatory Ventilation) is much like preparing for other types of mechanical ventilation, which is a way a machine helps a patient to breathe. The first requirement is that the patient must have an advanced airway. This is a tube put into the mouth or nose to help air get into the lungs. Also, the patient needs to be showing signs of better breathing. When these conditions are met, doctors can then start planning to wean the patient off the machine. The weaning process involves gradually reducing the support from the machine, allowing the patient’s lungs to take over the work of breathing.
How is Synchronized Intermittent Mandatory Ventilation performed
When a patient is ready to start the process of being taken off a ventilator, it involves making the right adjustments to the settings on the machine. These settings include the amount of air the patient breathes in each time (tidal volume), how many times they breathe in a minute (respiratory rate), the pressure applied by the machine at the end of each breath (PEEP), the percentage of oxygen they’re breathing in (FiO2), and any additional support to make breathing easier if needed.
It is recommended that within 60 minutes of the patient being put on a ventilator, a sample of their arterial blood is taken. The results of this blood test will help the medical team adjust the ventilator settings to best suit the needs of the patient’s body.
There is a method called SIMV (Synchronized Intermittent Mandatory Ventilation) that’s rarely used when easing a patient off the ventilator. A survey showed that it’s rarely used for this process, its use ranges from 0 to 6% depending on the area. Instead, medical professionals tend to use other methods such as pressure support (which combines PEEP with helping the patient breathe) and T-piece (a device that allows the patient to breathe on their own while still connected to the ventilator). The use of these techniques varies depending on the area also, with pressure support ranging from 56.5 to 72.3% and T-piece ranging from 8.9 to 59.5%.
Possible Complications of Synchronized Intermittent Mandatory Ventilation
Patients being treated with mechanical ventilation can sometimes face complications, such as pneumonia related to the ventilator use (VAP), lung injuries due to air pressure (barotrauma), acute respiratory distress syndrome (ARDS, a severe lung condition), collapsed lung (pneumothorax), partial or complete collapse of lung tissue (atelectasis), and a loud, high-pitched wheezing sound when exhaling (post-extubation stridor).
VAP is typically identified as a new, non-clearing spot in a chest x-ray after a patient has been under mechanical ventilation for over 48 hours along with at least three symptoms like fever, abnormal levels of white blood cells, increased sputum production, abnormal breathing sounds, cough, or worsening transfer of oxygen from lungs to blood.
ARDS is determined using a set of criteria known as the Berlin definition. This means the pressure of oxygen in the patient’s blood is measured and compared to the amount of oxygen they are being given. ARDS has three levels: mild with less than or equal to 300 mm Hg ratio, moderate with less than or equal to 200 mm Hg ratio, and severe with less than or equal to 100 mm Hg ratio.
A study conducted on children in Egypt found that 39.9% or 29.5 out of 1000 daily ventilations experienced complications. These complications included VAPs (27.3% or 20.19 for every 1000 ventilator days), pneumothorax (10.6% or 7.82 for each 1000 ventilator days), atelectasis (4.4% or 3.28 for every 1000 ventilator days), and post-extubation stridor (2.4% or 1.76 for each 1000 ventilator days).
Another complication is asynchrony, which is when there’s a mismatch between what the patient needs and what the ventilator supplies – this can occur in terms of breathing rate, airflow, volume, or pressure. Studies involving newborn patients show that an assistive breathing device adjusted to match the patient’s neural activity produced significantly fewer asynchrony events. However, in adult patients with ARDS, there was no significant difference in ventilator asynchrony, the duration the patient needed to be on a ventilator, or the length of their hospital stay.
What Else Should I Know About Synchronized Intermittent Mandatory Ventilation?
When a patient is on a ventilator, there are different techniques the machine can use to help the patient breathe. One of these techniques is called Synchronized Intermittent Mandatory Ventilation (SIMV). If the patient doesn’t take a breath on their own, the ventilator will give them breaths at set times. This method was initially praised for making patients feel more comfortable, making breathing less of a strain, reducing instances where the patient and ventilator are out of sync, and making it easier for patients to be taken off the ventilator. However, newer studies have shown these benefits might not be as significant as first thought.
SIMV is still a commonly used method, particularly in intensive care units across the US. There’s a newer version of SIMV called airway pressure release ventilation (APRV) where the inhale is longer than the exhale. This reverse relationship between inhaling and exhaling helps improve oxygen supply to the patient.
Although SIMV was quite popular when it first came out, recent studies showed that it might not be the best method. For example, a study on premature babies showed that SIMV resulted in higher mean airway pressure, longer weaning time, longer need for post-extubation nasal continuous positive airway pressure support, and a higher rate of extubation failure when compared against pressure support ventilation with volume guarantee.
Similarly, in adults who had coronary artery bypass grafting, a different ventilation method called adaptive support ventilation resulted in lower instances of lung collapse, fewer changes in ventilator settings, fewer alarms, and shorter hospital stays compared to SIMV.
When a patient is put on a ventilator, doctors start to plan how to gradually reduce and then remove the ventilator support. However, studies have shown that SIMV is the least efficient method to achieve this when compared against pressure support ventilation, and intermittent trials with a breathing device called a T-piece. This was seen in patients with acute respiratory distress syndrome, who showed increased ventilator weaning duration time with SIMV. In patients who had a liver transplant, SIMV required more changes to settings and longer use of mechanical ventilation compared to adaptive support ventilation.