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How Can Identical Tidal Volumes Lead to Different Outcomes in ARDS Patients with the Same Predicted Body Weight?

Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM

November 1, 2025

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Question

How can identical tidal volumes lead to different outcomes in ARDS patients with the same predicted body weight?

Answer

Even when ARDS patients share the same predicted body weight and receive identical tidal volumes, the impact of ventilation can vary significantly due to differences in functional lung volume. In some patients, much of the lung may be consolidated or collapsed, leaving only a small portion—the so-called “baby lung”—available for ventilation. Delivering standard tidal volumes in these cases results in higher stress and strain per unit of lung tissue, increasing the risk of ventilator-induced lung injury.

This heterogeneity emphasizes the need for individualized ventilator strategies. Clinicians must go beyond predictive formulas and assess each patient’s functional lung capacity through imaging, compliance trends, and clinical response. Recognizing that not all lungs of the same size behave the same way is essential to avoid overdistension, minimize injury, and improve outcomes in patients with severe respiratory failure.

This Ask the Expert is an edited excerpt from the course, Mechanical Power at a Glance, presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM.

keith lamb

Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM

Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM, is a respiratory therapist with over 22 years of clinical experience and is currently working in the Surgery/Trauma Service at the University of Virginia Medical Center in Charlottesville, Virginia. He is a fellow of both the American Association for Respiratory Care and the American College of Critical Care Medicine. Throughout his clinical career, Keith has held positions as ECMO Director, Research Coordinator, Clinical Specialist, Team Lead, and Staff Respiratory Therapist.

He has authored peer-reviewed publications and participated as Principal Investigator on numerous research initiatives. He is a published author with expertise in areas of respiratory critical care, and lectures in global topics nationally and internationally. His research and clinical work are centered on critical airway and sedation management, mechanical ventilation, and topics that pertain to the management of patients suffering from Acute Respiratory Distress Syndrome.

Related Courses

Mechanical Power at a Glance
Presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Video

Presenter

Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Course: #1840Level: Advanced1 Hour
  'the topic is very interesting and important'   Read Reviews
View CEUs/Hours Offered
Mechanical power pertains to the energy applied to the lungs of mechanically ventilated patients. We discuss approaches to minimizing mechanical power and the sequelae of excessive mechanical power.
Course Details
Key Concepts in the Management of Respiratory Failure Series: Invasive Mechanical Ventilation
Presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
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Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Course: #1629Level: Advanced1 Hour
  'Very well detailed'   Read Reviews
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This advanced course reviews invasive mechanical ventilation for patients with acute respiratory failure. The focus of the course is on increasing familiarity with findings in the current literature and includes future directions, theoretical information, and clinical and research applications. The invasive mechanical ventilation course is the second in the series and a stand-alone course examining the management of critically ill patients from the least invasive to most invasive modes of support.
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Key Concepts in the Management of Respiratory Failure Series: Extracorporeal Support (ECMO) and Adjunct Treatment
Presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
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Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Course: #1630Level: Advanced1 Hour
  'The ECMO portion at the beginning was great'   Read Reviews
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This advanced course reviews extracorporeal support (ECMO) and adjunct treatment for patients with acute respiratory failure. The focus of the course is on increasing familiarity with findings in the current literature and includes future directions, theoretical information, and clinical and research applications. The extracorporeal support and adjunct treatment course is the third in the series and a stand-alone course examining the management of critically ill patients from the least invasive to most invasive modes of support.
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Key Concepts in the Management of Respiratory Failure Series: Research Review and Case Reports
Presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Video

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Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Course: #1631Level: Advanced1 Hour
  'thoroughness of the content'   Read Reviews
View CEUs/Hours Offered
This advanced course reviews noninvasive support, invasive mechanical ventilation, extracorporeal support and adjunct treatment research and case reports. The focus of the course is on increasing familiarity with findings in the current literature and includes future directions, theoretical information, and clinical and research applications. The course is the fourth in the series and a stand-alone course examining the evidence and case reports of critically ill patients from the least invasive to most invasive modes of support.
Course Details
Key Concepts in the Management of Respiratory Failure Series: Non-invasive Support
Presented by Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Video

Presenter

Keith Lamb, RRT, RRT-ACCS, FAARC, FCCM
Course: #1628Level: Advanced1 Hour
  'Excellent, knowledgeable presenter'   Read Reviews
View CEUs/Hours Offered
This advanced course reviews noninvasive support for patients with acute respiratory failure. The focus of the course is on increasing familiarity with findings in the current literature and includes future directions, theoretical information, and clinical and research applications. The Noninvasive Support course is the first in the series and a stand-alone course examining the management of critically ill patients from the least invasive to most invasive modes of support.
Course Details