From the Guidelines
Positive end-expiratory pressure (PEEP) therapy will result in a decrease in extravascular lung water, which is option (a). PEEP works by maintaining positive pressure in the airways at the end of expiration, which prevents alveolar collapse and improves oxygenation, as noted in a study published in 2024 1. This positive pressure pushes fluid from the alveolar spaces back into the pulmonary circulation, thereby reducing extravascular lung water, especially in conditions like pulmonary edema. Some key points to consider when using PEEP include:
- PEEP actually decreases cardiac preload by increasing intrathoracic pressure, which reduces venous return to the heart, as discussed in a study from 2016 1.
- It increases, not decreases, atrial natriuretic peptide due to atrial stretching.
- PEEP also increases, not decreases, functional residual capacity by preventing alveolar collapse at the end of expiration, which is valuable in treating conditions like acute respiratory distress syndrome (ARDS), where maintaining alveolar recruitment and reducing pulmonary edema are therapeutic goals, as supported by a study from 2017 1. In terms of specific guidance, a low PEEP strategy (defined as <10 cm H2O) should be considered for mild ARDS, while a high PEEP strategy can be used for moderate to severe ARDS with careful monitoring for hemodynamic side effects, as recommended in the 2024 study 1. Overall, the use of PEEP is an important consideration in the management of patients with respiratory distress, and its effects on extravascular lung water, cardiac preload, and functional residual capacity must be carefully balanced to achieve optimal outcomes.
From the Research
Effects of Positive End-Expiratory Pressure Therapy
- The application of positive end-expiratory pressure (PEEP) therapy has several effects on the body, including:
- Increase in extravascular lung water: Studies have shown that PEEP can increase extravascular lung water due to a decrease in lung lymph flow 2.
- Decrease in cardiac preload: PEEP can decrease venous return to the heart, leading to a decrease in cardiac preload 3, 4.
- Decrease in atrial natriuretic peptide: PEEP has been shown to decrease the release of alpha-atrial natriuretic peptide, which can contribute to fluid retention and renal dysfunction 3, 4.
- Increase in functional residual capacity: PEEP is used to improve gas exchange and increase functional residual capacity, recruit air spaces, and decrease pulmonary shunt in patients suffering from respiratory failure 5, 2.
Answer to the Question
Based on the evidence, the correct answer is: (a) decrease in extravascular lung water is incorrect, as PEEP can actually increase extravascular lung water 2. (b) increase in cardiac preload is incorrect, as PEEP can decrease cardiac preload 3, 4. (c) decrease in atrial natriuretic peptide is correct, as PEEP has been shown to decrease the release of alpha-atrial natriuretic peptide 3, 4. (d) decrease in functional residual capacity is incorrect, as PEEP is used to increase functional residual capacity 5, 2.