How does atelectasis cause fever?

From the Guidelines

Atelectasis causes fever through the accumulation of secretions, infection, and the body's inflammatory response to the collapsed lung tissue, and the most effective way to manage this is by addressing the underlying atelectasis promptly through deep breathing exercises and other interventions. When a portion of the lung collapses (atelectasis), it creates an environment where secretions can accumulate and stagnate, providing an ideal breeding ground for bacteria. These trapped secretions become infected, triggering an inflammatory response as the body attempts to fight the infection. This inflammation leads to the release of pyrogens (fever-producing substances) such as interleukins and tumor necrosis factor, which act on the hypothalamus to raise the body's temperature setpoint, resulting in fever. Additionally, even without infection, the body's inflammatory response to the collapsed lung tissue itself can generate cytokines that induce fever.

The risk of fever increases with the extent of lung collapse and the duration of atelectasis. According to the guidelines for evaluating new fever in adult patients in the ICU 1, the use of thoracic bedside ultrasound can be helpful in identifying pleural effusions and parenchymal or interstitial lung pathology in critically ill patients with fever and an abnormal chest radiograph. However, the presence of atelectasis may lower the specificity of this diagnostic tool.

Some key points to consider in the management of atelectasis-related fever include:

• The importance of early mobilization and deep breathing exercises to prevent the development of atelectasis
• The use of incentive spirometry and chest physiotherapy to help resolve existing atelectasis
• The potential need for bronchoscopy to remove mucus plugs in some cases
• The consideration of thoracic bedside ultrasound as a diagnostic tool in critically ill patients with fever and an abnormal chest radiograph, as suggested by the Society of Critical Care Medicine and the Infectious Diseases Society of America guidelines 1.

It is also worth noting that while the guidelines for the early management of adults with ischemic stroke 1 do not directly address the relationship between atelectasis and fever, they do highlight the importance of preventing pneumonia and other infections in patients who are at high risk for these complications. By addressing atelectasis promptly and effectively, healthcare providers can help prevent the development of fever and more serious complications like pneumonia.

From the Research

Atelectasis and Fever

• Atelectasis is a state of collapsed and non-aerated region of the lung parenchyma, which can occur due to various mechanisms such as airway obstruction, compression of parenchyma, and increased surface tension in alveoli and bronchioli 2.
• The development of atelectasis is common in both patients with and without lung injury during mechanical ventilation, and it may contribute to or attenuate lung injury by different possible mechanisms, including inflammatory activation or infection of the affected regional lung tissues 3.
• Atelectasis can lead to alveolar hypoxia, which can result in lung inflammation and injury, and this inflammation can cause fever 4.

Association between Atelectasis and Fever

• However, the existing evidence on the association between atelectasis and fever is contradictory, and some studies have found no significant association between postoperative atelectasis and fever 5, 6.
• A systematic review of eight studies found that only one study reported a significant association between postoperative atelectasis and fever, while the remaining studies indicated no such association 5.
• A retrospective analysis of 1,624 patients who underwent elective major upper abdominal surgery found no significant association between atelectasis and early postoperative fever (EPF) within 2 days after surgery 6.

Mechanisms of Atelectasis-Induced Fever

• The pathophysiologic mechanism of how atelectasis causes fever remains unclear, but it is thought to be related to the inflammatory response and the release of proinflammatory cytokines in response to alveolar hypoxia 4.
• The activation of nuclear factor (NF)-κB and hypoxia-inducible factor (HIF)-1α in lung epithelial cells may play a role in the inflammatory response and the development of fever in atelectatic lungs 4.