Non-Invasive Dynamic Monitoring-Guided Oscillation and Lung Expansion for Airway Clearance in Severe Blunt Chest Trauma: A Clinical Study

Trauma is one of the top ten causes of death across all age groups, and among young adults under 45 years of age, trauma has remained the leading cause of death for nearly four decades. As a megacity, Beijing features complex traffic conditions and a dense population, resulting in a high incidence of multiple injuries such as traffic injuries and falls from height. Such trauma is often accompanied by multiple organ injuries, which not only makes treatment difficult and costly but also significantly increases the financial burden on families and causes losses in social productivity due to long-term rehabilitation requirements and loss of working capacity. Improving treatment protocols and promoting advanced technologies can improve patient survival and reduce the need for long-term care. Establishing an efficient prevention and treatment system helps reduce redundant consumption of medical resources, alleviate pressure on medical insurance funds, and thereby release more resources to support economic and livelihood development. Therefore, reducing trauma mortality in young and middle-aged adults plays a critical role in stabilizing the labor supply, promoting urban modernization, and implementing the Healthy China strategy.

More than one-quarter of trauma patients eventually die from chest trauma and its related complications . The risk of pulmonary infection in trauma patients is four times higher than that in non-trauma patients. Rib fractures, pulmonary contusion, hemothorax, and procedures such as closed thoracic drainage and endotracheal intubation are all important risk factors for pulmonary infection. In patients with severe blunt chest trauma, the proportion of fractures involving stable thoracic structures such as ribs and sternum can reach 36.1%. Such fractures not only cause severe pain but, more importantly, approximately 10% of patients may develop flail chest with paradoxical respiratory motion, which severely disrupts normal respiratory mechanics and impairs the patient's ability to clear the airway through active coughing.

The incidence of pulmonary contusion exceeds 70% in severely injured patients and accounts for more than 50% of all chest traumas, particularly in high-speed motor vehicle-related trauma-the predominant injury mechanism of trauma in China. Pulmonary contusion not only directly injures the lung parenchyma but, more crucially, significantly increases the risk of atelectasis when coexisting with flail chest. Atelectasis leads to local alveolar collapse, impaired gas exchange, and further deterioration of airway self-clearing capacity. Restrictive ventilatory disorders caused by atelectasis and flail chest, together with hemorrhage and exudation from pulmonary contusion, create a highly favorable environment for pulmonary infection. Studies have reported that the incidence of pulmonary infection in such patients can exceed 21%. Infection not only directly exacerbates respiratory failure but is also a key trigger for sepsis, acute respiratory distress syndrome (ARDS), and even multiple organ failure. These severe complications progress sequentially to form a fatal pathological cascade, markedly increasing the risk of death.

Therefore, in-depth research and establishment of an airway clearance protocol for patients with severe blunt chest trauma are critically important. Its core objective is to interrupt the fatal chain from rib fracture, pulmonary contusion, and atelectasis to severe infection and organ failure. By improving respiratory failure, ensuring systemic oxygen supply, supporting patients through the acute phase, and effectively preventing or treating complications such as pulmonary infection, the prognosis can be significantly improved, mortality reduced, and excessive consumption of medical resources decreased.Blunt chest trauma is mainly caused by high-speed motor vehicle crashes, occupational injuries, and falls from height. Injury often immediately damages bony structures including the ribs, sternum, scapula, and spine. The incidence of rib fractures among trauma admissions is as high as 10%. The vast majority of patients with rib fractures are prone to varying degrees of atelectasis due to pain and restricted thoracic movement. More than 30% develop secondary complications such as pulmonary infection, which becomes an important cause of death. Rib fractures not only induce severe pain-especially during deep breathing and coughing-but also severely impair chest wall mechanical stability, restrict respiratory excursion, reduce tidal volume, and weaken effective cough capacity. This mechanical dysfunction combined with pain suppresses ventilation, impairs airway clearance, leads to sputum retention, and significantly increases the risk of pulmonary infection and respiratory failure.

Currently, rib fractures are mainly managed conservatively. Multimodal analgesia (e.g., opioids or regional blocks) is commonly used in elderly patients; although pain is relieved, respiratory drive and cough reflex may be further suppressed. Surgical fixation may be considered in patients with flail chest or those under 65 years of age to enhance chest wall stability and reduce mortality. However, continuous airway clearance therapy is still required postoperatively; otherwise, complications such as ventilator-associated pneumonia, unplanned intubation, and prolonged ICU stay may still occur.

Pulmonary contusion refers to a pathological state in which chest trauma causes direct or indirect injury to the lung parenchyma, leading to edema or alveolar hemorrhage, resulting in structural and functional lung damage. Injury mechanisms include chest compression, inertial effects, and implosion effects, which can cause detachment of alveoli and pulmonary interstitium, laceration of small vessels, and destruction of cellular structures. Increased intra-alveolar hemorrhage and exudation, bronchiolar spasm, and extensive injury can also lead to lung consolidation and necrosis. Furthermore, injury can trigger inflammatory imbalance and immune dysfunction, resulting in systemic inflammatory response syndrome, apoptosis and necrosis of immune cells, and pulmonary edema due to increased pulmonary capillary permeability, which may progress to ARDS 24-48 hours after injury. Patients subsequently enter a post-traumatic immunosuppressive state with recurrent infections and complicated clinical courses.

Necrotic tissue, exudate, and blood accumulate within alveoli, forming an ideal environment for infection. Multiple studies have confirmed that pulmonary contusion is an independent risk factor for pulmonary infection in trauma patients. Therefore, the development of efficient, low-risk airway clearance techniques that do not compromise respiratory function has become critical to improving the prognosis of such patients.

Mechanical airway clearance techniques refer to therapeutic methods that remove airway secretions and maintain airway patency via mechanical means. Studies have shown that these techniques effectively eliminate secretions, regulate airflow to relieve dyspnea, prevent and reduce respiratory infections, and promote recovery of respiratory function, with significant benefits in delaying disease progression, alleviating symptoms, and enhancing exercise capacity and quality of life. However, their efficacy varies considerably among individuals, influenced by age, disease severity, airway pathophysiology, device usability, and comfort. Currently, literature on the application of such techniques in patients with severe blunt chest trauma remains relatively scarce.

Mechanical airway clearance techniques include airway expansion and lung recruitment, intrapulmonary/chest wall oscillation, and other adjuvant methods. Following blunt chest trauma, tracheal collapse often occurs, and mucus hypersecretion leads to obstruction of small airways and alveoli by mucus plugs, causing localized emphysema or atelectasis. Retained mucus plugs further aggravate airway obstruction. Lung expansion techniques increase intraluminal pressure to promote airway dilation, elevate alveolar pressure and ventilation volume, help reopen occluded small airways, recruit alveoli, and facilitate secretion drainage. Oscillation techniques are classified into intrapulmonary oscillation and chest wall oscillation. Intrapulmonary oscillation delivers high-frequency oscillatory waves into the central airways, propagating to small and medium airways, which loosens and liquefies mucus and metabolic debris. Shear forces generated by airflow changes help separate secretions from the airway wall while enhancing ciliary movement to promote expectoration. In contrast, chest wall oscillation is clearly unsuitable for chest trauma patients, especially those with concurrent rib fractures.

In our previous study, the investigators analyzed more than 30,000 cases from the National Trauma Center Database and found that 66.4% of patients with severe blunt chest trauma had concurrent rib fractures, 55.87% had multiple fractures (≥4 ribs), and 37.4% had combined pulmonary contusion. In a further prospective observational cohort study evaluating the efficacy of EIT-guided OLE in such patients, results demonstrated that this protocol improved the ventilation-perfusion ratio and oxygenation index and shortened total mechanical ventilation duration. Based on literature review and preliminary findings, the investigators propose the following hypothesis: the application of EIT-noninvasively monitored OLE airway clearance in patients with severe blunt chest trauma can improve the ventilation-perfusion ratio, shorten mechanical ventilation time, reduce the incidence of complications such as pulmonary infection and mortality, and decrease medical resource consumption.