Case Part 2: The Iron Lung

Here is a summary of our patient Bob, who we met in Part 1 of the case.

  • Bob is a 65-year-old man with past medical history (PMH) of COPD and hypertension, presenting with one week of worsening shortness of breath, fevers, cough, fatigue, and loss of appetite.
  • Vitals showed high fever, as well as low O2 saturation and a high respiratory rate (which partially improved after being given an oxygen mask).
  • Labs showed normal white blood cell count and he was negative for the flu.
  • CT scan of his chest showed bilateral, diffuse ground glass opacities in his lungs, consistent with fluid in his lungs.
  • Bob was admitted to the hospital for supplemental oxygen and close monitoring.


It’s been a few days since Bob was admitted to the hospital and you are going to virtually check in with him. Before you talk to Bob, you check in with his nurse, who has some test results for you.

Nurse Morgan: The test you ordered for COVID-19 for Bob came back, and it’s positive.



Source:Baycare

Bob (Patient): Thank you for telling me about my diagnosis, doctor. I have been having a really hard time breathing for the past few minutes, even though I’m still using the oxygen mask. Can you help me?



Source:Alamy

Nurse Morgan: The patient told me he has been having a hard time breathing so I retook his vitals. Here they are:

Heart Rate Blood Pressure Temperature Oxygen saturation Respiratory Rate O2 flow rate
Patient (now) 110 90/50 103.2F 72% 35 6 L/min
Patient 2 days ago 95 120/70 102F 90% 21 6 L/min
Normal 60-100 110-140/60-80 98.6F 95-100% 12-20 --

What is intubation?

Intubation is the process of inserting a breathing tube (also called an endotracheal tube) through the patient’s mouth and into the trachea to assist with breathing. A patient can then be placed on a mechanical ventilator to breathe for the patient during severe illness or anesthesia for surgery.



Source:VeryWell Health

Watch this video from Covenant Health from 3:28-4:29 to learn about the intubation:



What is a mechanical ventilator?



Source:Hackaday

Once the patient is intubated, he will be attached to a mechanical ventilator. A mechanical ventilator is a machine that helps patients breathe when they are unable to breathe on their own due to severe illness or anesthesia. The ventilator is attached to the breathing tube in the patient’s trachea.

How does a ventilator compare to an oxygen mask?

  • An oxygen mask is worn on the outside of the body and requires the patient to keep breathing spontaneously on their own. The oxygen flows through the mask at a steady rate that is set by the healthcare providers. The main purpose of the oxygen mask is that the air the patient is breathing has a much higher percentage of oxygen than room air, which is 21% oxygen. For example, if a patient is on a mask receiving 4 L O2 / min, the air she is breathing is about 35% oxygen.
  • A ventilator can do the work of breathing for a patient. As shown in the video, the breathing tube is in the trachea. The ventilator uses pressure to push air into the lungs to simulate inhalation. Patients usually exhale on their own because the lungs are like a spring; the spring is stretched during inhalation and wants to recoil back after being stretched with air. You can also adjust the percentage of oxygen in the air you give the patient through the ventilator.

Controlling and Monitoring Ventilation



Source:Osmosis

These graphs are produced by the ventilator as it breathes for the patient. The shape of the curves helps healthcare providers know how to adjust the settings.

Here are some of the different variables that you set on the ventilator to help the patient breathe:

What is it? Example Ranges
Tidal volume How big of a breath do you want the patient to take? 4-6 mL/kg
Respiratory rate How fast do you want the patient to breathe? 12 - 20 breaths/min
FiO2 What percentage of oxygen is in the air flowing through the tube? Up to 1 (100%)
PEEP (Positive End Expiratory Pressure) This keeps the alveoli from closing at the end of a breath which helps decrease the amount of work it takes to continue breathing. 3-5 cm H2O

If you want to learn more about ventilators and practice controlling the ventilator settings on different patients, check out this great Ventilator Simulator by OPENPediatrics.

What are the patient’s vital signs now?


Heart Rate Blood Pressure Temperature Oxygen saturation Respiratory Rate O2 flow rate
Patient 100 105/60 103F 92% 12 100
Normal 60-100 110-140/60-80 98.6F 95-100% 12-20 --

The patient’s vital signs look a lot better thanks to your intervention, great job!

You have successfully treated a patient with COVID-19 and he made a full recovery! Proceed to the wrap up to learn more about COVID-19 and ARDS.