Systemic Arterial Gas Embolism (SAGE) is a rare but fatal complication characterized by the accidental entry of gas into the left heart system, which then travels through the systemic arterial circulation, leading to embolisms in critical organs such as the brain and heart. Compared to venous gas embolism, SAGE can cause catastrophic outcomes, such as acute cerebral infarction, myocardial infarction, or even death, with only a minimal volume of gas. Furthermore, recent studies have found that even subclinical micro-emboli, while not causing typical infarction symptoms, may activate inflammatory responses and the complement system, leading to long-term risks such as postoperative cognitive dysfunction. The potential impact of SAGE is far broader and more severe than previously recognized.

Bronchoscopy is a cornerstone in the diagnosis and treatment of respiratory diseases, with increasingly widespread applications. Theoretically, procedures involving the lungs-as gas-containing hollow organs-carry the highest risk of SAGE, especially during invasive interventions. Although the incidence of SAGE has been reported to be as high as 4.8% in similar procedures such as CT-guided percutaneous lung biopsy, far exceeding traditional perceptions, the risks associated with bronchoscopy have not received sufficient attention. Currently, reports of SAGE during bronchoscopy are limited to sporadic cases, and there is a lack of systematic prospective studies. As a result, the true incidence, high-risk procedural steps, and definitive risk factors remain unknown, leaving clinical diagnosis and prevention without evidence-based guidance.

To address this research gap, this study is designed as a prospective observational cohort study. It will be conducted at the Laoshan Branch of the Affiliated Hospital of Qingdao University and plans to enroll approximately 500 adult patients undergoing diagnostic or therapeutic bronchoscopy. This study will innovatively combine two non-invasive, highly sensitive monitoring techniques: transthoracic echocardiography (TTE) and transcranial Doppler (TCD). TTE will be used to monitor microbubble signals ("snowstorm-like echoes") in the cardiac chambers in real time and grade their severity, while TCD will be employed to sensitively detect high-frequency transient micro-embolic signals (HITS) in the cerebral arterial circulation, quantifying their number and intensity. Through synchronous intraoperative monitoring, the study aims to accurately capture gas emboli generated during procedures, regardless of whether they cause clinical symptoms.

The primary objective of this study is to determine the actual incidence of SAGE during various bronchoscopic diagnostic and therapeutic procedures. Secondary objectives include comparing the risk of gas emboli associated with different procedures (such as transbronchial lung biopsy, argon plasma coagulation, and laser therapy) and systematically identifying independent risk factors for SAGE through multivariate logistic regression analysis of patient baseline data, comorbidities, and procedural details.

Inclusion Criteria:

• Patients undergoing electronic bronchoscopy for diagnostic and/or therapeutic procedures. If the same patient undergoes multiple procedures, each procedure is considered an independent observation unit.

  • Intraoperative real-time transthoracic echocardiography (TTE) monitoring completed.

    • Age ≥ 18 years. ④ Signed informed consent.

Exclusion Criteria:

① Poor TTE image quality that prevents assessment of the presence of gas emboli in the cardiac chambers (judged independently by two ultrasound physicians; disagreements resolved through consultation).

② Critically ill patients requiring emergency bronchoscopy procedures (e.g., massive hemoptysis, foreign body aspiration, or severe bronchospasm requiring emergency intubation).

③ Presence of intracardiac shunts (e.g., patent foramen ovale, atrial septal defect, ventricular septal defect).

④ Missing key clinical data.

Patients undergoing video bronchoscopy at the Bronchoscopy Room of the Laoshan Branch of Qingdao University Affiliated Hospital.