What is positive end-expiratory pressure (PEEP) therapy and how is it used with mechanical ventilation?

Answer

PEEP is a mode of therapy used in conjunction with mechanical ventilation. At the end of mechanical or spontaneous exhalation, PEEP maintains the patient's airway pressure above the atmospheric level by exerting pressure that opposes passive emptying of the lung. This pressure is typically achieved by maintaining a positive pressure flow at the end of exhalation. This pressure is measured in centimeters of water.

PEEP therapy can be effective when used in patients with a diffuse lung disease that results in an acute decrease in functional residual capacity (FRC), which is the volume of gas that remains in the lung at the end of a normal expiration. FRC is determined by primarily the elastic characteristics of the lung and chest wall. In many pulmonary diseases, FRC is reduced because of the collapse of the unstable alveoli. This reduction in lung volume decreases the surface area available for gas exchange and results in intrapulmonary shunting (unoxygenated blood returning to the left side of the heart). If FRC is not restored, a high concentration of inspired oxygen may be required to maintain the arterial oxygen content of the blood in an acceptable range.

Applying PEEP increases alveolar pressure and alveolar volume. The increased lung volume increases the surface area by reopening and stabilizing collapsed or unstable alveoli. This splinting, or propping open, of the alveoli with positive pressure improves the ventilation-perfusion match, reducing the shunt effect.

After a true shunt is modified to a ventilation-perfusion mismatch with PEEP, lowered concentrations of oxygen can be used to maintain an adequate PaO₂. PEEP therapy may also be effective in improving lung compliance. When FRC and lung compliance are decreased, additional energy and volume are required to inflate the lung. By applying PEEP, the lung volume at the end of exhalation is increased. The already partially inflated lung requires less volume and energy than before for full inflation.

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Media Gallery

An example of the Drinker and Shaw negative-pressure ventilator (iron lung).
The pressure, volume, and flow to time waveforms for assist-control ventilation.
The pressure, volume, and flow to time waveforms for controlled ventilation.
The components of mechanical ventilation inflation pressures. Paw is airway pressure, PIP is peak airway pressure, Pplat is plateau pressure.
The effects of decreased respiratory system compliance (A) and increased airway resistance (B) on the pressure-time waveform.
Determination of the lower inflection point to estimate the best (optimal) positive end-expiratory pressure (PEEP) from the pressure-volume hysteresis curve.
The effect of positive end-expiratory pressure (PEEP) on the pressure-time inflation curve.
The pressure, volume, and flow to time waveforms for synchronized intermittent mandatory ventilation (SIMV).
The pressure, volume, and flow to time waveforms for synchronized intermittent mandatory ventilation (SIMV) with pressure-support ventilation.
The flow to time waveform demonstrating auto–positive end-expiratory pressure (auto-PEEP).
The pressure, volume, and flow to time waveforms for pressure-regulated volume-controlled ventilation.
The pressure, volume, and flow to time waveforms for proportional-assist ventilation.
The pressure, volume, and flow to time waveforms for airway pressure–release ventilation.

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Author

Christopher D Jackson, MD Faculty, Department of Internal Medicine, University of Tennessee Health Science Center College of Medicine-Memphis; Staff Physician, Christ Community Health Services; Staff Physician, Baptist Memorial Hospital

Christopher D Jackson, MD is a member of the following medical societies: American College of Physicians, Memphis Medical Society, National Medical Association, Southern Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Muthiah P Muthiah, MD, FCCP, D-ABSM Associate Professor of Medicine, Division of Pulmonary and Critical Care and Sleep Medicine, Vice Chair for Internal Medicine (VA Academic Affairs), University of Tennessee Health Science Center College of Medicine; Director of Medical Intensive Care Unit (MICU), Memphis Veterans Affairs Medical Center

Muthiah P Muthiah, MD, FCCP, D-ABSM is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American Thoracic Society, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Zab Mosenifar, MD, FACP, FCCP Geri and Richard Brawerman Chair in Pulmonary and Critical Care Medicine, Professor and Executive Vice Chairman, Department of Medicine, Medical Director, Women's Guild Lung Institute, Cedars Sinai Medical Center, University of California, Los Angeles, David Geffen School of Medicine

Zab Mosenifar, MD, FACP, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, American Thoracic Society

Disclosure: Nothing to disclose.

Additional Contributors

Ryland P Byrd, Jr, MD Professor of Medicine, Division of Pulmonary Disease and Critical Care Medicine, James H Quillen College of Medicine, East Tennessee State University

Ryland P Byrd, Jr, MD is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society

Disclosure: Nothing to disclose.

Thomas M Roy, MD Chief, Division of Pulmonary Disease and Critical Care Medicine, Quillen Mountain Home Veterans Affairs Medical Center; Professor of Medicine, Division of Pulmonary Disease and Critical Care Medicine, Fellowship Program Director, James H Quillen College of Medicine, East Tennessee State University

Thomas M Roy, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Thoracic Society, Southern Medical Association, Wilderness Medical Society

Disclosure: Nothing to disclose.

Acknowledgements

Gregg T Anders, DO Medical Director, Great Plains Regional Medical Command , Brooke Army Medical Center; Clinical Associate Professor, Department of Internal Medicine, Division of Pulmonary Disease, University of Texas Health Science Center at San Antonio

Disclosure: Nothing to disclose.

Oleh Wasyl Hnatiuk, MD Program Director, National Capital Consortium, Pulmonary and Critical Care, Walter Reed Army Medical Center; Associate Professor, Department of Medicine, Uniformed Services University of Health Sciences

Oleh Wasyl Hnatiuk, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society

Disclosure: Nothing to disclose.

Semaan Georges Kosseifi, MD Fellow in Pulmonary/Critical Care Medicine, East Tennessee State University

Disclosure: Nothing to disclose.

What is positive end-expiratory pressure (PEEP) therapy and how is it used with mechanical ventilation?

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