The FlightBridgeED Podcast

In this episode of the FlightBridgeED Podcast, part of our "Every Breath They Take" series on respiratory critical care, Dr. Michael Lauria explores whether we truly protect the lungs during mechanical ventilation. While the best evidence suggests keeping tidal volumes at 6 cc/kg and plateau pressures below 30 cm H2O, is that enough? ARDS is a complex lung pathology, and as we unravel its intricacies, there may be more to consider.

Join us as we explore the popular concept of driving pressure and introduce the emerging idea of mechanical power. While plateau pressure remains the gold standard, these additional metrics may provide further guidance for adjusting ventilation strategies and minimizing ventilator-induced lung injury, especially in critical care transport settings. Whether you're new to the field or a seasoned professional, this episode offers valuable insights into advanced respiratory management.

Listen to FlightBridgeED anywhere you get your podcasts, or visit us at flightbridgeed.com/explore. While there, explore our other fantastic, free content and award-winning courses to help you excel in your critical care practice.

TAKEAWAYS
  • Mechanical ventilation is a double-edged sword. It can maintain oxygenation and ventilation but can also damage the lungs.
  • Lung protective ventilation prevents ventilator-induced lung injury, especially in acute respiratory distress syndrome (ARDS).
  • Maintaining a plateau pressure below 30 cmH2O is an essential goal in lung protective ventilation.
  • Driving pressure, the difference between plateau pressure and PEEP, is a surrogate for transpulmonary pressure and may be a useful parameter to consider in lung protective ventilation.
  • Keeping driving pressure < 15 cmH2O may be beneficial. 
  • Driving pressure might be helpful in titrating peep and optimizing lung recruitment, as well as in identifying patients who may benefit from smaller tidal volumes, even if the plateau pressure is below 30.
  • Mechanical power, which represents the energy delivered to the lung over time, is a newer concept that requires further research to determine its role in lung protective ventilation.
  • Optimizing the ventilatory and inspiratory flow rates (in addition to peep, plateau pressure, and tidal volume) may help reduce mechanical power below 17-22 J/min.
REFERENCES
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  2. Azizi BA, Munoz-Acuna R, Suleiman A, et al. Mechanical power and 30-day mortality in mechanically ventilated, critically ill patients with and without Coronavirus Disease-2019: a hospital registry study. J Intensive Care. Apr 6 2023;11(1):14. doi:10.1186/s40560-023-00662-7
  3. Battaglini D, Fazzini B, Silva PL, et al. Challenges in ARDS Definition, Management, and Identification of Effective Personalized Therapies. J Clin Med. Feb 9 2023;12(4)doi:10.3390/jcm12041381
  4. Battaglini D, Sottano M, Ball L, Robba C, Rocco PRM, Pelosi P. Ten golden rules for individualized mechanical ventilation in acute respiratory distress syndrome. J Intensive Med. Jul 2021;1(1):42-51. doi:10.1016/j.jointm.2021.01.003
  5. Bellani G, Laffey JG, Pham T, et al. Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries. Jama. Feb 23 2016;315(8):788-800. doi:10.1001/jama.2016.0291
  6. Bugedo G, Retamal J, Bruhn A. Driving pressure: a marker of severity, a safety limit, or a goal for mechanical ventilation? Crit Care. Aug 4 2017;21(1):199. doi:10.1186/s13054-017-1779-x
  7. Chiumello D, Froio S, Mistraletti G, et al. Gas exchange, specific lung elastance and mechanical power in the early and persistent ARDS. J Crit Care. Feb 2020;55:42-47. doi:10.1016/j.jcrc.2019.09.022
  8. Coppola S, Caccioppola A, Froio S, et al. Effect of mechanical power on intensive care mortality in ARDS patients. Crit Care. May 24 2020;24(1):246. doi:10.1186/s13054-020-02963-x
  9. Cressoni M, Cadringher P, Chiurazzi C, et al. Lung inhomogeneity in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med. Jan 15 2014;189(2):149-58. doi:10.1164/rccm.201308-1567OC
  10. Duan J, Wang S, Liu P, et al. Early prediction of noninvasive ventilation failure in COPD patients: derivation, internal validation, and external validation of a simple risk score. Ann Intensive Care. Sep 30 2019;9(1):108. doi:10.1186/s13613-019-0585-9
  11. Gattinoni L, Collino F, Camporota L. Mechanical power: meaning, uses and limitations. Intensive Care Med. Apr 2023;49(4):465-467. doi:10.1007/s00134-023-06991-3
  12. Gattinoni L, Marini JJ, Pesenti A, Quintel M, Mancebo J, Brochard L. The "baby lung" became an adult. Intensive Care Med. May 2016;42(5):663-673. doi:10.1007/s00134-015-4200-8
  13. Gattinoni L, Tonetti T, Quintel M. Regional physiology of ARDS. Crit Care. Dec 28 2017;21(Suppl 3):312. doi:10.1186/s13054-017-1905-9
  14. Goligher EC, Dres M, Patel BK, et al. Lung- and Diaphragm-Protective Ventilation. Am J Respir Crit Care Med. Oct 1 2020;202(7):950-961. doi:10.1164/rccm.202003-0655CP
  15. Guérin C, Papazian L, Reignier J, Ayzac L, Loundou A, Forel JM. Effect of driving pressure on mortality in ARDS patients during lung protective mechanical ventilation in two randomized controlled trials. Crit Care. Nov 29 2016;20(1):384. doi:10.1186/s13054-016-1556-2
  16. Ogbu OC, Martin GS, Murphy DJ. A Few Milliliters of Prevention: Lung-Protective Ventilation Decreases Pulmonary Complications. Crit Care Med. Oct 2015;43(10):2263-4. doi:10.1097/ccm.0000000000001234
  17. Paudel R, Trinkle CA, Waters CM, et al. Mechanical Power: A New Concept in Mechanical Ventilation. Am J Med Sci. Dec 2021;362(6):537-545. doi:10.1016/j.amjms.2021.09.004
  18. Sahetya SK, Hager DN, Stephens RS, Needham DM, Brower RG. PEEP Titration to Minimize Driving Pressure in Subjects With ARDS: A Prospective Physiological Study. Respir Care. May 2020;65(5):583-589. doi:10.4187/respcare.07102
  19. Serpa Neto A, Deliberato RO, Johnson AEW, et al. Mechanical power of ventilation is associated with mortality in critically ill patients: an analysis of patients in two observational cohorts. Intensive Care Med. Nov 2018;44(11):1914-1922. doi:10.1007/s00134-018-5375-6
  20. Simonis FD, Binnekade JM, Braber A, et al. PReVENT--protective ventilation in patients without ARDS at start of ventilation: study protocol for a randomized controlled trial. Trials. May 24 2015;16:226. doi:10.1186/s13063-015-0759-1
  21. Tongyoo S, Viarasilpa T, Deawtrakulchai P, Subpinyo S, Suppasilp C, Permpikul C. Comparison of limited driving pressure ventilation and low tidal volume strategies in adults with acute respiratory failure on mechanical ventilation: a randomized controlled trial. Ther Adv Respir Dis. Jan-Dec 2024;18:17534666241249152. doi:10.1177/17534666241249152
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Creators & Guests

Host
Dr. Michael Lauria
FlightBridgeED Chief Medical Director | Content Creator/Host

What is The FlightBridgeED Podcast?

The FlightBridgeED Podcast provides convenient, easy-to-understand critical care medical education and current topics related to the air medical industry. Each topic builds on another and weaves together a solid foundation of emergency, critical care, and prehospital medicine.

The content of this podcast is based on medical fact and evidence-based practice from credible, authoritative sources but is not a substitute for your institution's policies, procedures, common sense, or good judgment. The views and opinions are those of Eric Bauer and FlightBridgeED in their entirety. This is the FlightBridgeED podcast, critical care and emergency medicine education for nurses and paramedics.

Hello everybody, and welcome back to the FlightBridgeED Podcast. I'm your host, Dr. Michael Lauria. I'm an Emergency Medicine, EMS, and Critical Care physician with a special interest and focus on Critical Care Transport, and I’m currently active as a flight and retrieval physician.

Today's episode is one I've been meaning to do for a while, and it’s on lung protective ventilation. The big question: Are we really protecting the lungs? Mechanical ventilation is a double-edged sword; while it's a technique to keep people alive and maintain oxygenation and ventilation, it can also cause significant damage to lung tissue. Sometimes, it may even make things worse.

Ventilator-induced lung injury, or VILI, is something we see all the time in the ICU, and it's something we strive to prevent as much as possible. In the context of today's discussion, I’ll be focusing on lung protective ventilation in the setting of Acute Respiratory Distress Syndrome (ARDS). While there are other conditions that can affect lung compliance, we’ll focus on ARDS because it’s a condition flight crews deal with frequently, and it’s become particularly prominent in the wake of COVID-19.

When done properly, lung protective ventilation can minimize secondary ventilator-induced injuries and improve patient outcomes. For a long time, we used a binary approach: obstructive ventilation for obstructive pathologies like COPD and asthma, and lung protective ventilation for everyone else, ventilating at 6 cc/kg. However, recent research, including the Prevent Trial, has shown us that in non-ARDS patients, it’s okay to ventilate a little more liberally, up to 8 cc/kg.

That said, the ARMA Trial in 2000 set the standard for lung protective ventilation, comparing tidal volumes of 12 cc/kg to 6 cc/kg. This was a significant reduction, but it remains unclear what the perfect tidal volume is for all patients. The key takeaway from the ARMA Trial is the importance of maintaining plateau pressures below 30 cm H2O, and ideally below 27 cm H2O.

We know from the ARMA trial that plateau pressures above 30 cm H2O significantly increase mortality. While we try to aim for lower pressures, there is some gray area. For instance, I consider plateau pressures between 27 and 30 cm H2O to be a caution zone, where we should carefully monitor and make adjustments as needed.

When plateau pressures exceed 30 cm H2O, we should reduce tidal volumes to decrease the strain on the lungs. A reasonable lower limit for tidal volume is around 4 cc/kg, provided we can maintain a pH of at least 7.15.

Now, this is all common practice for critical care transport, but I also want to talk about two newer concepts: driving pressure and mechanical power.

Driving pressure is the difference between plateau pressure and PEEP (Positive End-Expiratory Pressure). It’s essentially a surrogate for the amount of pressure required to deliver a specific tidal volume, given the lung’s compliance. This concept gained attention in 2015 when Amato and colleagues demonstrated that driving pressure, rather than plateau pressure, was the best predictor of mortality in ARDS patients.

The challenge with driving pressure is determining whether it’s simply a reflection of sicker lungs or if it’s actually causing more damage. Some evidence suggests we should aim for driving pressures below 15 cm H2O, even if the plateau pressure is acceptable. In certain cases, it may be worth reducing tidal volume further to decrease driving pressure.

The second concept I want to discuss is mechanical power, which refers to the total energy delivered to the lungs over time. This idea was introduced by Gattinoni and colleagues and involves more dynamic measurements, such as tidal volume, respiratory rate, and inspiratory flow.

Mechanical power may be a more comprehensive way to assess ventilator-induced lung injury. By considering how fast we deliver breaths, how often, and at what pressures, we can better understand how much strain we are putting on the lungs.

There’s growing observational data suggesting that mechanical power above certain thresholds (around 22-25 J/min) correlates with increased mortality. However, we’re still waiting for more robust randomized controlled trials to confirm this concept as a standard of care.

In practice, I keep these newer concepts in mind, but I always start with the basics: maintaining plateau pressure below 30 cm H2O, reducing tidal volumes as needed, and considering driving pressure and mechanical power when appropriate.

Ultimately, while some of these newer metrics may guide our decisions in the future, they should not yet be codified into practice without further evidence. That said, intelligent clinicians should be aware of them as potential tools in their ventilator management strategies.

That wraps up today’s episode on lung protective ventilation. Thank you all for tuning in, and as always, fly safe.