Hi everyone, I'm Sindhya Rajeev. I work as an emergency physician at Stanford University in California. This lecture is a first in a series that will review ventilator management. In this lecture, we will focus on choosing the best initial ventilator settings for COVID-19 patients and I will be joined by Dr. Ben Lindquist, who is also an emergency medicine physician at Stanford University. Welcome, Ben. Thank you for having me. Managing ventilators is a broad topic. So what will we cover today? At the end of this lecture, we want you to be able to one, remember to prepare the equipment and post- intubation sedation medications before intubating the patient, two, select the appropriate initial ventilator settings for COVID-19 patients, and three, determine which ventilator settings to check and adjust based on your evaluation. Okay. Tell us how you approach this. If you are responsible for managing an intubated patient, the management steps start before intubation. In this section, we will go over the critical steps that need to be completed before intubating a patient. I cannot emphasize enough the importance of preparing before intubation. I've seen a physician intubate the patient, but the equipment to connect the patient to the ventilator or the sedation medication wasn't ready. This caused problems. What are the steps that need to be completed before intubation? We will start by preparing the tubes that connect the ventilator to the patient. This is an end-tidal CO2 monitor. It monitors carbon dioxide that comes through the tube. We use this to confirm that the endotracheal tube is in the correct location, in the trachea and not in the esophagus. It is attached like this to the ventilator tubing. If your hospital does not have an end-tidal CO2 monitor, you can use a CO2 colorimeter, which will turn from purple to yellow if it detects CO2. If you do not have any type of CO2 monitor, then you can confirm the location of the tube using chest x-ray, tube condensation, and breath sounds. Remember that breath sounds are difficult to hear in patients with COVID-19 ARDS. Now that we've attached the end-tidal CO2 monitor to the ventilator tubing, what's next? The next step is to place a filter on the end-tidal CO2 monitor that we just connected to the ventilator tubing. This filter prevents viral particles from the patient from entering the ventilator tubing and it prevents viral particles from being blown around the room when the ventilator is disconnected. After you have connected the filter like this to the end-tidal CO2 monitor, you can turn on the ventilator to make sure it has power and is ready to go. Even if you do not have a filter, there are ways to stop the virus from spreading. If possible, immediately after the endotracheal tube is placed, connect the endotracheal tube to the ventilator. Do not use a bag valve mask because switching from the bag valve mask to the ventilator can cause viral particles to spread in the air. When you need to disconnect the patient from the ventilator, even temporarily, use a hemostat to clamp shut the ventilator tubing close to the patient. Wrap medical tape around the tube where the hemostat will be clamped to prevent the tube from cracking. That's a great solution. Now, after the ventilator and attachments are set up, make sure to draw up the post sedation medications and have them ready. The post sedation medication will need to be started immediately after the intubation so that there is no time in between during which the patient wakes up and is biting on the tube or worse, pulls out the tube. We've now set up, if we have it, the end-tidal monitor and viral filter on the ventilator tubing. And we've drawn up the post-sedation medications. The doctor can now intubate the patient. In this section, we will go over initial critical steps after the doctor has placed the endotracheal tube. The first critical action after placing the endotracheal tube is to confirm that the tube is in the trachea. If you haven't end-tidal CO2 monitor, we do this by looking at the end-tidal CO2 waveform on the monitor. It should look like this. Keep in mind that when a patient is in cardiac arrest and receiving inadequate chest compressions, the end-tidal CO2 will not show a wave form even if the endotracheal tube is in the trachea. Also, the end-tidal CO2 reading may look normal if the endotracheal tube is in the right bronchus and only ventilating the right lung. Be sure to still listen to lung sounds and obtain a chest x-ray in addition to using the end-tidal CO2 monitor. Now let's discuss the initial ventilator settings. If we simplify it, the ventilator is a machine that pushes air into the patient. We need to tell the ventilator when and how to do this. The first step is to choose the assist control setting. Under the assist control setting, the ventilator delivers air at a set rate, and whenever the ventilator senses the patient starting to inhale. On this screen, each of these waves represents a breath that is delivered by the ventilator. On the pressure wave, the negative deflection is when the patient is initiating a breath. The ventilator senses this and assists by delivering air into the patient. The next question is how much air to provide the patient. If we give too little air, the lungs won't inflate enough as seen. But if we give too much air, as you see here, the lungs could be damaged and the patient could develop a pneumothorax. The goal is to give the correct amount of air each breath like this. The amount of air given to the patient each breath is called tidal volume. And for COVID-19 patients, the ideal tidal volume, or air given each breath, is eight milliliters per kilogram of ideal body weight. Take note that Sindhya said eight milliliters per kilogram of ideal body weight. A person's ideal body weight is based on their height. The formula will be provided in the handout. But for example, a man who is 175 centimeters tall, his ideal body weight is 70 kilograms based on the formula. So the tidal volume for this man would be eight milliliters times 70 kilograms, which is his ideal body weight, which equals 560 milliliters per breath. We decided how much air or a tidal volume to give the patient. Next, we decide how often to give breaths. This is a respiratory rate. If the respiratory rate is too slow, that patient will not get enough breaths. If it is too fast, the patient will get too many breaths. An ideal respiratory rate should be set. This is 16 breaths per minute. The next setting to choose is PEEP: Positive and Expiratory Pressure. In people with ARDS, the alveoli in the lungs, which are like balloons, expand when we breathe air in, and collapse when we exhale, and the air is laid out. As you see in this video, Without PEEP, the alveoli collapses when exhaling. But if the ventilator provides PEEP, the alveoli stay open throughout. There is a lot of benefit with using the correct amount of PEEP. When the alveoli stay open throughout, it reduces damage to the tissue caused by opening, closing, opening, closing. Also with the alveoli staying open, it allows for better gas exchange. What PEEP should we start with? We can start with a PEEP of 8, The final setting to choose is FiO2, or fraction of inspired oxygen. This determines how much oxygen is delivered each breath. After intubation, the initial FiO2 is set at 100%. Now we will show a video demonstrating how to choose these settings on a ventilator. The ventilator model and nob locations may be different from yours. But this is an example. After choosing the initial settings and attaching the patient to the ventilator, it is important to check the plateau pressure. The plateau pressure is the amount of pressure in the airway after you breathe in. You want this to be less than 30 centimeters of water to prevent lung injury, pneumothorax, and other complications. And this is demonstrated in this video. Here we show you how to check plateau pressure. Your ventilator will have a button that says inspiratory hold. You will need to press this button for three seconds, like this. After a few seconds, the plateau pressure will appear in the box. We have covered what to prepare before intubation and the immediate post intubation actions and initial ventilator settings. In this next section, we will learn how to adjust the ventilator settings based on the patient's response. If the patient remains stable on the initial ventilator settings, perform an arterial blood gas or ABG after 10 minutes of being on the ventilator. We will include a table with the normal ABG values in the handout. This table shows how to correct abnormalities. If the PCO2 is abnormal, you will need to adjust the tidal volume and or the respiratory rate. If the PCO2 is too high, increase the tidal volume and/or respiratory rate per the chart. If the PO2 is abnormal, you will need to adjust FIO2 or PEEP. For example, if the PO2 is too high, decrease Fi02 and/or PEEP per the chart and vice versa. If the patient continues to be hypoxic despite increasing FIO2 and PEEP, you can consider proning the patient. Proning a patient should be discussed and executed as a team. The handout includes a link demonstrating how to prone a patient. To review. you should now be able to: 1) Remember to prepare the equipment and post intubation sedation medications before intubating the patient. 2) Select the appropriate initial ventilator settings for COVID-19 patients. And 3) Determine which ventilator settings to check and adjust based on your evaluation. Thank you Ben for providing us your wisdom. Of course. Thanks for having me. And don't forget to download the handout. Take care.
