Clinical Skills: Mechanical ventilation - conventional ventilators
Hello, this video covers how to set up and monitor conventional ventilation modes. Normally you do everything on this list but to keep things concise, this video will focus on the steps in blue and will also cover frequently asked questions, tips, troubleshooting and include a summary as a word of caution.
We're not covering every possible type of equipment on the market. Make sure you understand how your own equipment works and how it may affect your procedure.
Here's all the equipment you'll need a ventilator, humidified oxygen source, an oxygen saturation monitor, personal protective equipment, suction equipment and a self inflating bag to set up your patient, turn your ventilator on and make sure you're connected to a humidified oxygen source, then connect your patient to an oxygen saturation monitor.
There are two main ways to deliver ventilation with a ventilator volume, assist control and pressure mode ventilation. Let's start by looking at volume controlled ventilation in volume assist control ventilation.
We want to program the ventilator to deliver a specific volume of breath to the patient at a certain rate, which means the pressure will be variable and your volume will be set at a constant rate this is important to know for patients with restrictive lung disease like acute respiratory distress syndrome, also called ARDS where forcing a set volume of air into non compliant lungs can cause trauma.
First select the tidal volume or VT, we want to deliver the typical initial VT is 6 to 8 mils per kilogram. Let's say our patient is 60 kg.
So let's start with seven mils per kilogram and set our tidal volume at 420 mils. Next, we need to set our peak flow respiratory rate and inspiration time which all go hand in hand.
Typical flow rates are usually set at 60 L per minute but can be increased to deliver breasts more quickly. If required, the flow rates can be programmed explicitly by us.
Our ventilator will generally adjust the amount of flow needed to deliver our set tidal volume. Next is respiration rate and inspiration time.
Normal adult respiration is 12 to 20 breast per minute and typical inspiratory time settings are 0.8 to 1.2 seconds. We want to set a respiratory rate for our patient of 15 breaths per minute.
So for ease of illustration, let's set our inspiratory time at two seconds. If we make an inspiratory expiratory ratio of 1 to 1, the expiratory time will also be two seconds and this will create four second breaths.
So in 60 seconds, our patient will receive 15 breaths and the ventilator will draw as much flow as needed to provide this rate of respiration for reference inspiratory expiratory ratio settings for a typical adult are 1 to 1.521 to 2.
A trick to remember this ratio is to think about your own breathing. We expire longer than we inspire.
Next, we'll select the level of peak and expiratory pressure or peak, which is the volume of air that remains in the lungs after exhalation, normal physiologic peep is 3 to 5 centimeters of H2O.
As your patient's lungs get better, they'll be able to manage ventilation with lower end pressures. So an initial higher peep can be decreased gradually.
Finally, we'll set our F IO two. When we initially intubate and ventilate a patient, we want to optimize their ventilation and oxygenation.
So we set the F IO 2 to 100%. And then wean down gradually.
Remember F IO two greater than 60% for extended periods of time can cause lung damage, especially in hypersensitive neonatal lungs.
So we want to wean below that number as soon as we can. Our goal for oxygenation is a PA O2 of 60 to 80 millimeters of mercury and an S AO two of 92% and higher.
Let's say our patient has been ventilated for a little while. So we'll set our F IO two at 60% to start.
Another volume mode of ventilation is volume synchronized, intermittent mechanical ventilation or volume SIMV. In this mode are example, tidal volume peak flow respiration rate, inspiration, time peak and F IO two will all be the same, but we'll be adding a trigger sensitivity level.
The trigger sensitivity allows the ventilator to sense when there is a decrease in system pressure. A negative pressure caused by a patient trying to take a breath.
The ventilator will then ensure your patient will receive the targeted volumes of breath programmed. So if your patient is able to inspire large volumes, that's great.
The ventilator will not assist with the breath. On the other hand, if your patient is not meeting the targeted volumes, the ventilator will assist to ensure the volumes are reached.
A typical flow trigger setting is 1 to 3 L below the set baseline flow trigger sensitivity works inversely, a higher sensitivity number on your ventilator makes it less sensitive to patient attempts at breathing.
A low sensitivity number on your ventilator will make it more sensitive and quicker to trigger breasts on patient demand.
Now, in pressure modes of ventilation, we need to program our ventilator to deliver a set pressure into our patient's lungs rather than a set volume.
Pressure, ventilation is effective for patients with decreased lung compliance or with respiratory rest is necessary and pressure assisted control ventilation instead of a tidal volume will set a peak inspiratory pressure or pip, this is the amount of pressure delivered in a coordinated manner to the patient.
Every breath that the patient takes is fully assisted with a tidal volume created by the set pressure. A typical pip in a person with healthy lungs is 20 to 25 centimeters of H2O.
So let's program that in to our ventilator, remembering that our patient has sick lungs and that a pip nearing 40 centimeters of H2O is a cause for concern.
The rest of the setup is the same. We'll still need to set our peep of five centimeters of H2O respiratory rate of 15 breaths per minute, an inspiratory time of one second and an F IO two of 60%.
You choose your settings appropriate to your patient's ideal body weight, not their actual body weight and their clinical condition.
So just like we were able to program the ventilator to support natural breasts in volume modes of ventilation with pressure, synchronized intermittent mechanical ventilation or pressure SIMV.
Our patient can also trigger breasts in pressure. SI MV will set all the same parameters.
The peak flow, the respiratory rate, the inspiration time, the peak and the F IO two, except instead of volume, we're going to set our peak inspiratory pressure.
With that added setting of trigger sensitivity. The last pressure mode of conventional ventilation is called pressure support ventilation and is often considered a weaning mode because it needs our patient to be stable enough to initiate their own breasts.
But because breathing through an endotracheal tube has a resistance that feels like breathing through a straw. It is also often a mode used between SI MV breasts to help offset the increased work of breathing needed with spontaneous breasts.
In this setting, the pressure support is adjusted to create appropriate minute ventilation and tidal volume to achieve these parameters.
Pressure support is generally set between 10 to 14 centimeters of H2O. So we'll set ours at 10 centimeters of h2o.
Ok. Now that we've established our ventilator settings, we're ready to connect the ventilator tubing securely to the end of our endotracheal tube, ensure the patient is comfortable with optimal sedation and analgesia prior to connecting and suctioning their airway to ensure patency after hooking up the ventilator.
The last and most important thing to remember is to set your ventilator alarms, set your alarms with tight parameters, 1 to 2 points above and below our programmed settings.
Most ventilators already have preprogrammed alarms. But for visualization, let's start with our tidal volume.
Our tidal volume is set at 420 mils to be delivered with each breath. So we'll program our low alarm to sound at 380 mils.
And our high to sound at 460 MS so that we're rapidly notified of volume loss or overload in our circuit. Then we'll set our high pip at 40 our low at 15, our high peep at seven and our low at four and are low F IO two at 90%.
Cardiovascular compromise or collapse is caused by the positive intrathoracic pressure created in mechanical ventilation.
This positive pressure can create functional changes in the patient's circulating blood volume because of a decrease in the amount of blood returning to the right side of the heart.
Clinical signs will show up as decreased BP, decreased cardiac output, which includes modeling of the skin and increased capillary refill time and acute changes in the heart rate.
Really high MPA can also cause barotrauma or air leak disease. The increase in intrathoracic pressure from the positive pressure.
Ventilation can cause extrapulmonary damage to occur. This pressure damage causes pneumothorax, pneumopericardium, pneumomediastinum, pneumoperitoneum and subcutaneous emphysema volume trauma occurs if volumes are too high for lungs that are stiff and non compliant.
Large volumes create high plateau pressures, meaning high levels of static distended alveolar pressure which can damage the already compromised lungs.
Patients are also at a high risk for developing ventilator associated pneumonia or VAP. Here are a bunch of strategies to help prevent vap in your patient, auto peep is another common complication of mechanical ventilation where air gets trapped in the lungs at the end of expiration because of incomplete expiration time.
It's associated with several factors including short expiratory time, prolonged inspiratory times, bronchospasm airway closure or collapse and hyperexcretion of mucus.
To name a few auto peep causes increased intrathoracic pressure due to stacking of breasts that can result in consequences as severe as cardiovascular compromise or collapse.
If you notice a higher peep than is set on the ventilator, which means that you're not returning to the baseline. This could be a problem.
Consult the practitioner immediately. If you suspect this issue, here are some frequently asked questions.
When would we want to use volume, assisted breasts versus pressure assisted breasts? The use of volume versus pressure assisted breasts for your patient is a clinical decision which depends on the available evidence and modes.
Clinical goals and practitioner preference. Is there an ideal temperature of humidified oxygen?
Yeah, there is humidified. O2 should remain between 34 °C and 41 °C.
Higher temperatures run the risk of thermal injury and lower temperatures decrease O2 humidity. Are there any quick troubleshooting tricks for ventilation?
Yeah. There is the pneumonic dope can help you quickly run through causes of unexplained alarms or sudden respiratory or cardiovascular changes in your patient.
Here's one quick tip, do not interrupt peep unless absolutely necessary. This will cause alveolar derecruitment and may cause a long delay in reestablishing lung volumes.
Here is a handy chart to help you troubleshoot. Common ventilator alarms, neonates have unique ventilatory issues and needs like short inspiratory times rapid and often irregular respiration rates and non compliant lungs.
Ventilatory treatment options is guided by and differs depending on gestational age in patients with acute respiratory distress syndrome, where inflammation in both lungs is so severe that the lung tissue itself becomes damaged and creates leakage of blood and plasma into the air spaces.
Our key focus when ventilating should be on plateau pressures, plateau pressure is the pressure delivered to the small airway and alveoli at the end of inspiration and is measured during an inspiratory pause on the ventilator.
This number should remain less than 30 millimeters of mercury in A DS patients to provide gentle management for these severely sick lungs by providing a tidal volume of 4 to 6 mils per kilogram, significantly less than the typical tidal volume.
This will allow for a lower gentler plateau
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