25. ARDS Precision Medicine & Phenotypes Roundtable

We’re very excited this week on Pulm PEEPs to be resuming our Roundtable series. We are joined by two outstanding critical care doctors to discuss precision medicine in the ICU, specifically ARDS phenotypes. This is a topic of increasing clinical and research interest, and personalized medicine in the ICU will certainly change the landscape of how care is delivered in the coming years and decades. We are honing in on ARDS today and how phenotyping can influence future research and clinical care.

Meet Our Guests

Carolyn Calfee is a Professor of Medicine and Anesthesia at the University of California, San Francisco. She is a leader in the field of ARDS research and a pioneer in the field of ARDS phenotyping research. She has received numerous NIH grants and has literally 100s of publications on ARDS and other topics. She is also a previous ATS CC Assembly chair, and in 2022 received the ATS Recognition Award for Scientific Accomplishments.

Annette Esper is an Associate Professor of Medicine at Emory University School of Medicine. She works clinically in critical care and is the Medical Director of the stepdown Intensive Care Unit at Grady Memorial Hospital. In addition to her clinical activities, Annette does both clinical and translational research in ARDS, and was the Assembly Chair for the ATS Critical Care Assembly from 2021 – 2022.

Key Learning Points

Berlin Criteria of ARDS:

— Acute symptoms developing within 7 days of a known insult

— Bilateral airspace opacites on chest imaging

— Hypoxemia not fully explained by cardiogenic pulmonary edema

— P:F ratio < 300 on a PEEP of 5

Heterogeneity in ARDS

— ARDS has a broad definition so it is comprised of people with a wide range of disease characteristics and severity

— There is heterogeneity in clinical characteristics, but also underlying biological drivers of disease

— Heterogeneity stymies research efforts to identify effective therapies in ARDS

Phenotyping in ARDS

— There are many ways of phenotyping for critical illness and ARDS

1. Etiology. Examples: COVID vs non-COVID, pulmonary vs non-pulmonary, bacterial vs viral

2. Physiologic phenotypes: Severity (Berlin criteria P:F ratio); Compliance, Ventilatory ratio

3. Biological phenotypes: Different underlying drivers of disease

— The motivation for phenotyping is to find treatment-responsive subgroups within the broader heterogeneous subgroups

— Phenotyping embodies more than risk factors, because it includes information about the host response, not just predictors of outcome

Biomarkers in ARDS

— There is probably a role for biomarkers in ARDS clinically and in research

> Prognostication

> Identify who will be responsive to specific therapies

> May not be one biomarker, will likely be a panel

— What is the perfect ARDS biomarker?

> Specific: identify a group of patients that are at risk, or respond to therapies differently

> Easily measurable at the bedside

> Reliable

> Reproducible

— Challengers in identifying useful biomarkers

> Heterogeneity of disease

> Real world applicability. For example, can you get IL-6 back in real-time? Can you apply it consistently when labs have different testing techniques and scales?

> Temporal stability – how do biomarkers change over the time course of ARDS?

— Biomarkers of interest

> Inflammatory markers (IL-6, IL-8, TNF)

> sRAGE – Soluble receptor for advanced glycation end products

> Highest levels on type 1 alveolar epithelial cells

> Seems to be a marker of alveolar epithelial injuries

> Meta-genomic sequencing of patients in a real-time environment

Latent class analysis

— Clustering technique that, agnostic to outcomes, looks for existing groups within the data

— Ideally, identifies biologically distinct phenotypes that may have different prognoses or response to therapy

Omics in ARDS

— Existing risk scores are quite limited, so using biological data to distinguish patients seems promising.

— Unbiased approach to identifying subgroups to identify patients that behave similarly biologically

— Omics is really thinking about endotyping patients and identifying the biological processes that are driving phenotypes

Hypo and hyperinflammatory phenotypes in ARDS

— Described by LCA incorporating demographics, clinical data, labs, vital signs, 6-8 plasma protein biomarkers

— Importantly, the groups were identified agnostically to outcomes.

— Distinguished by:

> Inflammatory biomarkers (IL-6, IL-8, TNF 1)

> Acidosis

> Shock, vasopressor requirement, and multi-system organ failure

— Consistently across 8 different data sets

— Both RCTs and observational cohorts

— Hyperinflammatory phenotype has dramatically worse clinically outcomes (higher mortality, fewer VFD)

— The different phenotypes respond differently to therapies retrospectively in RCTs

— The phenotypes did respond differently to PEEP, fluids conservative therapy, and simvastatin.

— This was not seen universally (rosuvastatin did not have differential treatment response)

— Note: We don’t really know that inflammation is at the heart of the pathogenesis of what distinguishes these two groups. The “hypoinflammatory” phenotype still has elevated levels of inflammatory biomarkers compared to controls.

What is next?

— This is all just subgroup analysis.

— These hypotheses still need to be tested prospectively

— Need to be able to easily identify the phenotypes quickly and easily

— Working on biomarker-based and non-biomarker-based clinical classifications

Key Quote:

Dr. Calfee “My takeaway point would be, there is no one best or one right way to phenotype these patients. I think there are numerous different approaches that we’re probably going to be using over the years. But I would say that what we want to focus on is what has the potential to change outcomes for our patients and to really identify individual patients or groups of patients that respond differently to therapies. And I think if we can keep that goal in mind and start testing some of these hypotheses prospectively we’re going to make progress.”

References and links for further reading

  1. Sinha P, Calfee CS. Phenotypes in ARDS: Moving Towards Precision Medicine. Curr Opin Crit Care. 2019;25(1):12-20. doi:10.1097/MCC.0000000000000571
  2. Calfee CS, Delucchi KL, Sinha P, et al. Acute respiratory distress syndrome subphenotypes and differential response to simvastatin: secondary analysis of a randomised controlled trial. Lancet Respir Med. 2018;6(9):691-698. doi:10.1016/S2213-2600(18)30177-2
  3. Matthay MA, Arabi YM, Siegel ER, et al. Phenotypes and personalized medicine in the acute respiratory distress syndrome. Intensive Care Med. 2020;46(12):2136-2152. doi:10.1007/s00134-020-06296-9
  4. Wilson JG, Calfee CS. ARDS Subphenotypes: Understanding a Heterogeneous Syndrome. Crit Care. 2020;24(1):102. doi:10.1186/s13054-020-2778-x
  5. Yang P, Esper AM, Martin GS. The Future of ARDS Biomarkers: Where Are the Gaps in Implementation of Precision Medicine? In: Vincent JL, ed. Annual Update in Intensive Care and Emergency Medicine 2020. Annual Update in Intensive Care and Emergency Medicine. Springer International Publishing; 2020:91-100. doi:10.1007/978-3-030-37323-8_7

21. Post Intensive Care Syndrome (PICS)

Today on Pulm PEEPs, we are joined by two pioneers in the field of post-intensive care outcomes and delirium research. Drs. Dale Needham and Wes Ely talk to us all about the Post Intensive Care Syndrome (PICS) and cover everything from how it was first recognized, to the impact it has, and, most importantly, what we can do to prevent it. This is a huge topic in the field of critical care and we’re thrilled to be delving into it with such knowledgeable guides.

Meet Our Guests

Wes Ely is the Grant W. Liddle Chair in Medicine and a Professor of Medicine at Vanderbilt University Medical Center. He is also the Associate Director of Aging Research at the VA Tennessee Valley Geriatric Research and Education Clinical Center and the co-director of the Critical, Illness, Brain Dysfunction and Survivorship Center. He has published 100s of manuscripts on critical illness survivorship and delirium. He also published a book called “Every Deep-Drawn Breath” about his and his patients’ experiences in the ICU and about the ramifications of critical illness. All net proceeds for the book are going to the CIBS Center Endowment for Survivorship

Dale Needham is a Professor of Medicine at Johns Hopkins, where he is also the Medical Director of the Critical Care Physical Medicine and Rehabilitation Program and the Director of the Outcomes After Critical Illness and Surgery Group. He is the author of 100s of publications focusing on post-ICU outcomes and has received numerous research grants from the NIH and other organizations.

Key Learning Points

Visit our website www.pulmpeeps.com to see the key learning points from this episode summarized in two infographics.

References and links for further reading

  1. Devlin JW, Skrobik Y, Gélinas C, et al. Executive Summary: Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU. Critical Care Medicine. 2018;46(9):1532-1548. doi:10.1097/CCM.0000000000003259
  2. Ely EW. The ABCDEF Bundle: Science and Philosophy of How ICU Liberation Serves Patients and Families. Crit Care Med. 2017;45(2):321-330. doi:10.1097/CCM.0000000000002175
  3. Mikkelsen ME, Still M, Anderson BJ, et al. Society of Critical Care Medicine’s International Consensus Conference on Prediction and Identification of Long-Term Impairments After Critical Illness. Crit Care Med. 2020;48(11):1670-1679. doi:10.1097/CCM.0000000000004586
  4. Needham DM, Sepulveda KA, Dinglas VD, et al. Core Outcome Measures for Clinical Research in Acute Respiratory Failure Survivors. An International Modified Delphi Consensus Study. Am J Respir Crit Care Med. 2017;196(9):1122-1130. doi:10.1164/rccm.201702-0372OC
  5. Needham DM, Wozniak AW, Hough CL, et al. Risk Factors for Physical Impairment after Acute Lung Injury in a National, Multicenter Study. Am J Respir Crit Care Med. 2014;189(10):1214-1224. doi:10.1164/rccm.201401-0158OC
  6. Semler MW, Bernard GR, Aaron SD, et al. Identifying Clinical Research Priorities in Adult Pulmonary and Critical Care. NHLBI Working Group Report. Am J Respir Crit Care Med. 2020;202(4):511-523. doi:10.1164/rccm.201908-1595WS
  7. Spruit MA, Holland AE, Singh SJ, Tonia T, Wilson KC, Troosters T. COVID-19: Interim Guidance on Rehabilitation in the Hospital and Post-Hospital Phase from a European Respiratory Society and American Thoracic Society-coordinated International Task Force. Eur Respir J. Published online August 13, 2020:2002197. doi:10.1183/13993003.02197-2020
  8. Turnbull AE, Sepulveda KA, Dinglas VD, Chessare CM, Bingham CO, Needham DM. Core Domains for Clinical Research in Acute Respiratory Failure Survivors: An International Modified Delphi Consensus Study. Crit Care Med. 2017;45(6):1001-1010. doi:10.1097/CCM.0000000000002435
  9. Ward DS, Absalom AR, Aitken LM, et al. Design of Clinical Trials Evaluating Sedation in Critically Ill Adults Undergoing Mechanical Ventilation: Recommendations From Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research (SCEPTER) Recommendation III. Crit Care Med. 2021;49(10):1684-1693. doi:10.1097/CCM.0000000000005049
  10. Ozga D, Krupa S, Witt P, Mędrzycka-Dąbrowska W. Nursing Interventions to Prevent Delirium in Critically Ill Patients in the Intensive Care Unit during the COVID19 Pandemic—Narrative Overview. Healthcare. 2020;8:578. doi:10.3390/healthcare8040578

6. PEEP in ARDS Roundtable

This week on Pulm PEEPs, Dave Furfaro and Kristina Montemayor are joined by experts in the field of critical care medicine and ARDS to discuss all things PEEP! Drs. Roy Brower, Sarina Sahetya, Todd Rice, and Elias Baedorf-Kassis discuss everything ranging from PEEP basics to their approach to optimizing PEEP in patients with ARDS.

Meet Our Guests

Roy Brower is a Professor of Medicine at Johns Hopkins where he served as the MICU director for over 33 years, and he has been one of the pioneers for lung-protective ventilation for patients with ARDS.

Elias Baedorf-Kassis is an Assistant Professor of Medicine at Beth Israel Deaconess Medical Center and Harvard Medical School. He is the Medical Director of Respiratory Care at BIDMC, and helps lead the VV-ECMO program.

Todd Rice is an Associate Profess of Medicine in the Division of Allergy, Pulmonary, and Critical Care Medicine at Vanderbilt University and Vice President for Clinical Trial Innovation and Operations in the Vanderbilt Institute for Clinical and Translational Research.

Sarina Sahetya is an Assistant Professor of Medicine at Johns Hopkins Hospital and does research in the diagnosis and treatment of ARDS.


Key Learning Points

Driving Pressure figure from Amato et al. 2015. Stress index figure from Hess 2014.
  • The plateau pressure can be measured on the ventilator with an inspiratory hold maneuver
  • Extrinsic PEEP is applied by the ventiilator, while intrinsic PEEP, or auto-PEEP, occurs when there is incomplete emptying of the lungs due to inadequate time for exhalation. This often happens with obstructive lung disease. Intrinsic PEEP can be measured on the ventilator with an end-expiratory hold maneuver
  • We utilize PEEP in all intubated patients to minimize atelectasis. When patients are supine, the heart moves back 2 cm and the diaphragm raises by 2 cm, so often the left lower lobe of the lung is compressed and there is atelectasis there. This is often seen on CXR:

References, Image Sources, and Further Reading

  1. Higher versus Lower Positive End-Expiratory Pressures in Patients with the Acute Respiratory Distress Syndrome. New England Journal of Medicine. 2004;351(4):327-336. doi:10.1056/NEJMoa032193
  2. Amato MBP, Meade MO, Slutsky AS, et al. Driving Pressure and Survival in the Acute Respiratory Distress Syndrome. New England Journal of Medicine. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639
  3. Writing Group for the Alveolar Recruitment for Acute Respiratory Distress Syndrome Trial (ART) Investigators. Effect of Lung Recruitment and Titrated Positive End-Expiratory Pressure (PEEP) vs Low PEEP on Mortality in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2017;318(14):1335-1345. doi:10.1001/jama.2017.14171
  4. Beitler JR, Sarge T, Banner-Goodspeed VM, et al. Effect of Titrating Positive End-Expiratory Pressure (PEEP) With an Esophageal Pressure-Guided Strategy vs an Empirical High PEEP-Fio2 Strategy on Death and Days Free From Mechanical Ventilation Among Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2019;321(9):846-857. doi:10.1001/jama.2019.0555
  5. LaFollette R, Hojnowski K, Norton J, DiRocco J, Carney D, Nieman G. Using pressure–volume curves to set proper PEEP in acute lung injury. Nursing in Critical Care. 2007;12(5):231-241. doi:10.1111/j.1478-5153.2007.00224.x
  6. Hess DR. Respiratory mechanics in mechanically ventilated patients. Respir Care. 2014;59(11):1773-1794. doi:10.4187/respcare.03410
  7. 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. 2020;65(5):583-589. doi:10.4187/respcare.07102
  8. Umbrello M, Chiumello D. Interpretation of the transpulmonary pressure in the critically ill patient. Ann Transl Med. 2018;6(19):383. doi:10.21037/atm.2018.05.31
  9. Kenny JES. ICU Physiology in 1000 Words: Driving Pressure & Stress Index. PulmCCM. Published February 13, 2016. Accessed January 1, 2022. https://pulmccm.org/review-articles/icu-physiology-in-1000-words-driving-pressure-stress-index/

Radiology Rounds – 12/28/21

Today we’re bringing you a special edition of Radiology Rounds complete with classic imaging, and some key critical care and ventilator physiology. This case is a perfect lead-in for next week’s Pulm PEEPs Roundtable on PEEP titration, so make sure to tune in!

How would you best describe the imaging findings?


There are bilateral, diffuse alveolar infiltrates noted on imaging with evidence of an air bronchogram on the CT image.

The patient develops worsening hypoxemia requiring mechanical intubation. The patient has multifocal pneumonia and requires intubation. ABG is performed and the calculated PaO2:FIO2 ratio is 150. How would you describe the severity of ARDS?


This patient has moderate ARDS based on a PaO2:FIO2 ratio that is between 100 and 200. The patient’s initial ventilator settings on volume control are:

Based on these parameters, we can also calculate the driving pressure. Driving pressure is calculated by using Pplat-PEEP. In this case, Pplat (30)-PEEP (10), would give a driving pressure of 20.