Acute Respiratory Distress Syndrome (ARDS)


This is a pretty hot topic lately. the presence of the acronym has increased exponentially all over the internet and media. Prior to two months ago, I’m betting you didn’t really think much about ARDS, but now I feel like I hear about it daily. Of course, my research direction definitely influences that. But so many topics I typically research or think about in my practice are becoming regular conversation topics these days.

ARDS has been so hot because it is the medical presentation we are hearing about with patients with COVID-19 that is resulting in need for critical and intensive care of otherwise healthy individuals.

ARDS comes in three sizes:

  • Mild (PaO2/FiO2 200-300 mmHg)
  • Moderate (PaO2/FiO2 100-200 mmHg)
  • Severe (PaO2/FiO2 <100 mmHg)

Clinically, you may see supplemental oxygen, NIV or HFNO, and mechanical ventilation utilized respectively at different levels of this diagnosis. For more about what those PaO2 measurements mean, check out this post.

What the heck do those numbers mean?

Just a reminder, SpO2 and PaO2 are not the same. See this article for more info on that.

FiO2 is the fraction of inspired oxygen. In room air, it is 0.21. That means that the normal room air we breath is about 21% oxygen. We modify this by adding supplemental oxygen which can increase the FiO2 up to 100%.

PaO2 is the partial pressure of oxygen in arterial blood. This is measured by ABG (arterial blood gases). Normal PaO2 is 80-100 mmHg.

So if we take what we now know, we can look at an example:

If your patient has an FiO2 of .21 (room air) and their ABGs are showing a PaO2 of 100 mmHg, 100 / .21 = 500 mmHg. This is a great number and you can see that this patient would not be considered in respiratory distress.

If you patient is on FiO2 of 0.6 and their ABGs are showing a PaO2 of 80 mmHg, 80 / .6 = 133 mmHg. This person would be in moderate respiratory distress even though they are already on supplemental oxygen and their PaO2 is technically in the normal range. They would probably need an increase in their FiO2 (provided by supplemental oxygen, NIV, or mechanical ventilation) to improve their situation.

What can we do about all these things?

The reasons we are so concerned about our patients having ARDS doesn’t stop after they are extubated. ARDS comes with a pretty heavy list of possible sequelae. When patients with COVID come home, we need to incorporate the risks of these sequelae in to our assessment and intervention process.

  • Long term pulmonary function impairments
  • lasting physical deficits
  • debility/long term strength deficits
  • poor emotional well-being
  • increased risk of heart disease, kidney disease, and strokes
  • Fatigue (about 70% of patient who experienced ARDS reported significant fatigue up to a year later)

So, if your patient is coming home after a diagnosis of ARDS or Acute Respiratory Failure (ARF), you need to be on the look out for other symptoms. Especially if your patient has other comorbidities, like COPD, you need to be thinking long term. You also need to look for places you can intervene! Look at that list. There are several places where expertly prescribed exercise can make a difference. You can get more information on the details of these deficits here!

What can we do about all these things?

Pulmonary rehab is more than just breathing exercises. Aerobic activity is one of the most powerful tools we have in pulmonary rehab and in physical therapy as a profession. Aerobic activity can impact debility, strength deficits, mental well-being, and risk of heart disease, just to make a few that are on the list!

I tend to utilize HIIT protocols for my patients that are tailored and customized to their specific level of function. HIIT has evidence to suggest that patients hate it less than continuous exercise, patient show improved compliance over the long term, and it invokes physiological and anatomical changes that improve the function and efficiency of the cardiac, pulmonary, and renal systems!

Why not work smarter and target all the affected systems simultaneously to improve their overall function? You can incorporate resistance training, reconditioning, and target specific deficits all at the same time! Customized HIIT programs are my choice intervention. And just because it’s high-intensity, doesn’t mean it’s too difficult. It’s really the alternating interval intensities that make these programs completely individualized and meet the patient at their current level. So you can apply these same concepts with lower level patients using lower level intensities.

Leave me a comment below telling me how you think “long term” for patients with pulmonary diagnoses!

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Tepper, S., Wruble, E., Stewart, E. (2020). Anatomy, histophysiology, and pathophysiology of COVID-19. Pacer Project. Retrieved from

Neufield, K. J., et al. (2020). Fatigue symptoms during the first year after ARDS. Chest. pii: S0012-3692(20)30686-3. doi: 10.1016/j.chest.2020.03.059. [Epub ahead of print]

Bauer, N., & Bartlo, P. (2020) Pulmonary Rehabilitation Post-Acute Care for COVID-19. PACER Project. Retrieved from

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