“The sole purpose of this article is not to dig into the full extent of ARDS, but to specifically talk about the nature of prone position.”
The Pre-brief
A 59 year-old-male with a past medical history for HTN, DM, and end-stage renal disease, now status post renal transplant on immunosuppression. He gets admitted into the ICU after being intubated in the Emergency Department and placed on lung-protective strategy on the ventilator (6 cc/kg of ideal body weight), and PEEP 12. His post-intubation arterial blood gas shows a pH of 7.39, a pCO2 of 39, PaO2 of 77 on 100% FiO2. On the way to the ICU, the team stopped at the CT scanner and showed bilateral ground-glass opacities, right worse than the left and negative for a pulmonary embolism. When he gets to the ICU, what would be the expected/recommended treatments?
A brief overview of Acute respiratory distress syndrome (ARDS):
ARDS is severe inflammatory lung injury leading to severe hypoxemia. The Berlin Criteria defines ARDS as acute onset, seven days or less; bilateral opacities noted on chest x-ray (CXR) or CT scan; The ratio of arterial oxygen partial pressure (PaO2) divided into the fractional inspired oxygen (FiO2) (P/F ratio) <300 mmHg with a minimum positive end-expiratory pressure (PEEP) of at least 5, and cannot be fully explained by cardiac failure.
Berlin Criteria, Levels of severity
Mild: A P/F ratio of 200-300 (27% Mortality)
Moderate: A P/F ratio of 100-200 (32% Mortality)
Severe: A P/F of <100 (45% Mortality)
There have only been two definitive therapies shown to reduce mortality in patients with severe ARDS. Those are lung-protective ventilation; you can read more about that here and prone positioning.
 What is prone positioning?
Prone positioning is the act of placing a patient facedown, on their belly, as opposed to lying flat on their back. Standardization of criteria in proning was set forth by the PROSEVA trial that showed a statistically significant reduction in 28-day mortality with proning.Â
How does proning work?
The suggested mechanism of action is as follows: While lying on your back (supine), the anterior portion of the lungs, the heart, and abdominal structures will increase the pressure exerted on the posterior lung structures. This collapse causes atelectasis, the fluid build-up will move to dependent lung structures (posterior lung fields) not allowing oxygenation. In association with this increase in pressure, the abdominal structures will displace cephalad and posterior and provoke worsening collapse of the posterior lung fields. Worsening ventilation and perfusion (V/Q) mismatch leads to the noted hypoxia seen in our patient at the beginning of the article.Â
When proned, the pressure on anterior structures is reduced, minimizing the expansion of the anterior chest wall, more evenly distributing the distending forces of ventilation throughout the lungs. In addition, the posterior portion of the lungs is more extensive, meaning they have more alveoli that can be recruited, conceding a greater area for the gas to be exchanged. Lastly, the diaphragm will move inferior when proned, allowing a reduction of compression on the lungs while contributing to less atelectasis and collapse. All of this combined will decrease the V/Q mismatch and improve oxygenation.
Now, back to the case that started us off, would he meet the criteria for pronation? His P/F ratio is 77. Yes, he would, so let’s see some steps that may help with pronation.
Tips for proning
Your institute may or may not have guidelines for proning patients; if so, please follow those guidelines. Below are some tips to help reduce accidental extubation, removal of vital lines and hemodynamic support, etc.
Make sure you have enough hands to help handle the situation, whether this is 3-4 helpers (depending on the size of patient) on each side, in even numbers so that each has a partner across from them. You will then need one to two respiratory therapists to hold and monitor the endotracheal tube/ventilator/tubing, and lastly, a leader of the pronation as the ever-watchful eyes.
I would highly recommend using a basic flat sheet under the patient and one top of the patient. In addition, make sure that you place padding (mepilex, for example) material on all bony prominences and pertinent soft tissue structures to help protect from pressure injuries. The cardiac leads will need to be taken off during the act of proning and transitioned to the back. However when the leads are on the back, one thing to remember is that they will be reversed (left to right) on the back.
Now, these two sheets you have set will allow you to roll them together into a tight “burrito” method, helping you keep control of proning. Once your “burrito” rolled, you will want to turn the patient perpendicular to the bed, exchange hands with your partner across from you, and fully complete the prone when everyone is ready. Again, I would highly suggest that all of this occurs with the respiratory therapist leading the count. This should be the case since the ETT is the essential device to remain in place during this procedure.
Once proned, the patient should remain so for 16 hours at the minimum; it is okay if it occurs for a more extended period. Supination occurs after this amount of time to complete nursing care and reevaluation of lung injury and compliance (Maximum 8 hours). If the patient’s oxygenation remains < 150 before the 8 hours is complete, it would be appropriate to re-prone before then. The PROSEVA trial saw a median number of 4 pronations during their trial.Â
The Debrief
- Lung protective ventilation and proning are the only interventions shown to reduce mortality in ARDS.
- If you notice this reduction in P/F ratio early in the course of illness make sure to advocate for pronation for your patient
- When proning, have plenty of help to ensure safety.
- Place mepilex anywhere a pressure injury may occur
- EKG leads to be taken off and placed on the back in reverse fashion.
- Know complications to watch for once proned.
References
- Curley MA. Prone positioning of patients with acute respiratory distress syndrome: a systematic review. Am J Crit Care. 1999;8(6):397-405.
- Guérin C, Reignier J, Richard JC, et al. Prone positioning in severe acute respiratory distress syndrome. N Engl J Med. 2013;368(23):2159-2168. doi:10.1056/NEJMoa1214103
- Scholten EL, Beitler JR, Prisk GK, Malhotra A. Treatment of ARDS With Prone Positioning. Chest. 2017;151(1):215-224. doi:10.1016/j.chest.2016.06.032
- Taccone P, Pesenti A, Latini R, et al. Prone positioning in patients with moderate and severe acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2009;302(18):1977-1984. doi:10.1001/jama.2009.1614
- The ARDS Definition Task Force*. Acute Respiratory Distress Syndrome: The Berlin Definition. JAMA.2012;307(23):2526–2533. doi:10.1001/jama.2012.5669
- Venus, K., Munshi, L., & Fralick, M. (2020). Prone positioning for patients with hypoxic respiratory failure related To covid-19. Canadian Medical Association Journal, 192(47). https://doi.org/10.1503/cmaj.201201
