PEEP PEEP PEEP

Ventilator management can be one of the more intimidating aspects of caring for critically ill patients both in the ED and in the prehospital setting.   There are several great #FOAMed resources out there on varying aspects of ventilator management including the well-known series by Dr. Weingart of emcrit.org (here and here).  Ventilator management can be an absolutely massive topic but for this post, and specifically for the embedded video below, I wanted to do a little deeper dive on only one of the components of ventilatory management: PEEP. The video goes into the details of what PEEP is, what it does for you from an oxygenation standpoint, and what it can do to the patient from a hemodynamic standpoint.  The concept of intrinsic and extrinsic PEEP is also explored (including a discussion of what happened when you apply external PEEP to a patient that already has intrinsic PEEP <spoiler> their lungs don’t explode (usually).

One of the takeaways from the video should be the hemodynamic changes that occur with the application of PEEP. Take a look at the figures below to get a closer look at the changes that occur in thoracic venous resistance and right ventricular afterload with the application of PEEP.  For a deeper dive into the interplay of venous return and cardiac output, the 2 part article series by Funk, et al published in Critical Care Medicine in 2013 (links in the references) are HIGHLY recommended reading.

Step 1 - Application of PEEP to "normal" (not significantly volume depleted individuals)

PEEP-1.png

Step 2 - Administration of Volume

PEEP-2.png

Step 3 - Cardiac Output Changes in the setting of Significant Volume Depletion and High Levels of PEEP

Significant decreases in cardiac output are possible when applying PEEP to patients with volume depletion. Likewise, high levels of PEEP will lead to greater decreases in cardiac output due to significant increases in afterload and thoracic venous resistance.
Significant decreases in cardiac output are possible when applying PEEP to patients with volume depletion. Likewise, high levels of PEEP will lead to greater decreases in cardiac output due to significant increases in afterload and thoracic venous resistance.

A Point of Emphasis & Clarification...

As pointed out on twitter by Scott Weingart, changes in PEEP increase right ventricular after load but can reduce left ventricular afterload.

@UCMorningReport Jeff, comments don't seem to be working on TtS site: great work on PEEP post! may want to make clear that PEEP [cont..]

— Scott Weingart (@emcrit) June 17, 2014

@UCMorningReport increases afterload on RV but decreases afterload on the LV latter is 1 of the prime motivations for the use of CPAP in APE

— Scott Weingart (@emcrit) June 17, 2014

References

  • DeGiorgi, A. & White, M. (2008) Ventilator Management: Maximizing Outcomes in Caring for Asthma, COPD, and Pulmonary Edema. Emergency Medicine Practice. 10 (8)
  • Funk, D., Jacobsohn, E., & Kumar, A. (2013) The Role of Venous Return in Critical Illness and Shock - Part 1: Physiology. Critical Care Medicine. 41 (1): 255-62. doi: 10.1097/CCM.0b013e3182772ab6
  • Funk, D., Jacobsohn, E., & Kumar, A. (2013) The Role of Venous Return in Critical Illness and Shock - Part 2: Shock and Mechanical Ventilation. 41 (2):573-9. doi: 10.1097/CCM.0b013e31827bfc25
  • Carmez, P., Borges, J., Tucci, M., Okamoto, V., Carvalho, C., Kacmarek, R., Malhotra. A, Velasco, I., Amato, M. (2005) Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation. Critical Care Medicine. 33 (7): 1519-28.