What causes atelectasis in post-operative (post-operative) patients?

From the Guidelines

Atelectasis in post-operative patients is primarily caused by shallow breathing patterns and decreased lung expansion during and after surgery, and can be prevented with strategies such as noninvasive positive pressure ventilation (NIPPV) or continuous positive airway pressure (CPAP), prophylactic mucolytics, prophylactic CPAP, and respiratory physiotherapy, as recommended by the European Society for Anaesthesiology and Intensive Care and European Society of Intensive Care Medicine (ESA/ESICM) guidelines 1. The pathophysiology of atelectasis in post-operative patients involves general anesthesia causing respiratory depression and altering normal breathing mechanics, while pain from surgical incisions leads patients to take shallow breaths to avoid discomfort. Prolonged supine positioning during surgery allows secretions to pool in dependent lung areas, and the lack of normal sighing and deep breathing prevents full alveolar expansion. Certain patient factors increase risk, including obesity, advanced age, smoking history, and pre-existing lung disease. Surgical factors also contribute, with upper abdominal and thoracic procedures carrying higher risk due to their proximity to the diaphragm. Some key points to consider in the prevention of atelectasis include:

• The use of NIPPV or CPAP in the postoperative period, as recommended by the ESA/ESICM guidelines 1
• The implementation of enhanced recovery pathways, which have been shown to reduce the incidence of postoperative pulmonary complications (PPCs) 1
• The use of prophylactic mucolytics, which have been found to have low-to-moderate quality of evidence to reduce incidence of PPCs 1
• The importance of respiratory physiotherapy, which has been found to have moderate evidence of benefit in the prevention of PPCs 1
• The potential benefits of goal-directed hemodynamic therapy and epidural analgesia in preventing PPCs 1.

From the Research

Causes of Atelectasis in Post-Op Patients

• Atelectasis occurs in most patients during general anesthesia and is the main cause of hypoxemia 2
• Pulmonary atelectasis is mainly caused by 3 factors: compression, gas absorption, and lack of surfactant 2
• Compression and gas absorption are the 2 most commonly implicated factors 2
• Lung collapse is accentuated if pure oxygen is inhaled during induction or if the patient is morbidly obese 2
• Laparoscopic, thoracic, and upper abdominal interventions also carry risk of lung collapse 2

Risk Factors for Atelectasis

• Morbid obesity 2, 3
• Preexisting lung disease or limited cardiopulmonary reserve 4
• Thoracic surgical procedures 5
• Patients with lung diseases are prone to increased bronchial secretions 5
• Age is not a factor in the amount of atelectasis 6
• Chronic obstructive lung disease may show less or even no atelectasis 6

Prevention and Treatment of Atelectasis

• Using positive end-expiratory pressure (PEEP) or a high tidal volume-thus providing a higher airway pressure (vital capacity maneuver)-or both in combination can prevent atelectasis or reopen collapsed lung tissue 2, 6
• Alveolar recruitment strategies have been tried in bariatric surgery, single-lung ventilation, laparoscopy, and adult respiratory distress syndrome 2
• Ventilation with a moderate fraction of inspired oxygen (FIO2, e.g. 0.3-0.4) can prevent the formation of atelectasis 6
• Intermittent "vital capacity"-manoeuvres together with PEEP reduces the amount of atelectasis and pulmonary shunt 6
• Prophylaxis includes preoperative and postoperative physiotherapy and medications, which should be graded in accordance to the individual patient's risk factors 5
• Large atelectasis requires bronchoscopy to remove mucous plugs 5
• Tracheostomy should be considered in patients with relapsing atelectasis or swallow disorders 5