To PEEP or Not to PEEP? Applying Positive End Expiratory Pressure During Anesthesia

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July 2026

In this VETgirl online veterinary continuing education video, Amanda M. Shelby, RVT, VTS (Anesthesia & Analgesia) details how to apply positive end expiratory pressure (PEEP) as a ventilation strategy to patients under general anesthesia. Tune in to learn how, when, and why to use PEEP!

PEEP can be used in spontaneous, manually assisted, or mechanically ventilated patients to assist with minimizing atelectasis, maintaining functional residual capacity (FRC), and assisting in minimizing intrapulmonary shunting. It works by maintaining a pre-set degree of positive airway pressure at the end of expiration.

Observe the patient manometer, without PEEP the patient manometer should rest at or near 0 cmH2O. When PEEP is applied to the anesthetic machine after the adjustable pressure limiting (APL) valve, also commonly called ‘pop-off valve’, a positive pressure at expiration should be observed on the patient manometer, as seen here. In this example, a fixed PEEP valve of 5 cmH2O was used.

PEEP valves can be added to most anesthetic machines or ventilators. They are manufactured as ‘add-on’ devices either as fixed at various pressures or adjustable. Some anesthetic machines and ventilators have electronic PEEP options in their configurations. There are several options for where to place a PEEP valve within a circle system; however, this VETgirl prioritizes placing it after the APL valve so that the PEEP is always reflected on the patient manometer. It is important to note that when PEEP is used, the reservoir bag or ventilator bellow will appear to bulge slightly or bellows will remain ‘full’. Resist the urge to depress the reservoir bag as this will result in loss of PEEP.

It is important to note that while PEEP can be helpful in a variety of clinical situations, maintaining some positive pressure during expiration can result in cardiovascular depression, especially magnified in hypovolemic patients. Use of excessively high PEEP could contribute to lung injury or barotrauma. PEEP is often implemented in specific patient populations such as obese, geriatric, end-stage pregnancy, patients with large cranial abdominal masses or otherwise increased intra-abdominal pressure, thoracic procedures, some forms of lower airway diseases, and large animals undergoing general anesthesia, especially when these patients are positioned in lateral or dorsal recumbency for prolonged periods of time. Implementation of ventilation strategies such as PEEP should be at the discretion of the veterinarian who assesses the patient.

**What do you do if you don’t have a manufactured PEEP valve but you need it apply it to a patent—create your own. Grab a disposable suction canister with a lid and a ruler. Fill the canister to the depth (in centimeters) of PEEP you want…here we are demonstrating 10 cmH2O (so 10 cmH2O PEEP) and place the scavenging hosing from the APL valve of the anesthetic machine into the depth of the water. This VETgirl connects an F-air canister by MacGyver-ing suction hosing with an old ET tube connector to avoid waste gas exposure.

‘Homemade’ PEEP with a suction jar (Photo courtesy of Amanda M. Shelby)

At VETgirl we hope you enjoyed this instructional video on how to apply a positive end-expiratory pressure or PEEP valve to an anesthetic machine or mechanical ventilator.

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