Effect of Lateral Versus Supine Positions on Postoperative Hypoxemia

Painless gastroscopy and colonoscopy have become essential modalities for the screening and diagnosis of digestive tract diseases, with their utilization increasing annually. However, hypoxemia remains the most common complication during these procedures, with reported incidences ranging widely from 1.8% to 69%. Severe hypoxemia can lead to adverse outcomes, including arrhythmias, hemodynamic decompensation, and hypoxic brain injury. Consequently, developing effective strategies to prevent hypoxemia in patients undergoing sedation for gastrointestinal (GI) endoscopy is of significant clinical value.

Current clinical research has primarily focused on hypoxemia occurring during the endoscopic procedure itself, whereas there is a paucity of high-quality evidence regarding the incidence and preventive measures of hypoxemia during the recovery phase. Specifically, the impact of body positioning on post-procedural hypoxemia remains largely unexplored. Emerging evidence suggests that the lateral decubitus position significantly reduces the incidence of hypoxemia during adult sedation. Anatomically, in the supine position, residual sedative effects combined with gravity cause the tongue and soft palate-structures lacking bony support-to collapse posteriorly, leading to upper airway obstruction. Conversely, the lateral position helps maintain a patent airway by preventing this collapse and optimizing the ventilation-perfusion (V/Q) matching, thereby stabilizing oxygenation.

Despite this theoretical basis, prospective studies investigating the effect of body positioning on recovery-phase hypoxemia in real-world settings are lacking. Therefore, this study hypothesizes that the lateral decubitus position reduces the incidence of recovery-phase hypoxemia compared to the supine position. Using prospective real-world data, we aim to validate this hypothesis and provide a simple, non-invasive, and cost-effective optimization strategy for clinical practice.

Inclusion criteria

• Age ≥ 18 years.
• Both sexes.
• American Society of Anesthesiologists (ASA) physical status classification I-III.
• Scheduled for combined painless esophagogastroduodenoscopy/colonoscopy or either of the two procedures.
• Ability to understand the study protocol and provide written informed consent.
• A broad set of inclusion criteria was adopted to enroll a patient population that better reflects routine clinical practice. The study aimed to enhance the generalizability of the findings by including patients with various comorbidities, such as preprocedural hypoxemia (room-air SpO₂ ≤ 90%), history of pulmonary surgery, obstructive sleep apnea (OSA), and other pulmonary conditions (including asthma, COPD, chronic bronchitis, emphysema, and pulmonary bullae).

Exclusion criteria

• Severe cardiovascular or cerebrovascular diseases.
• Pregnant patients.
• History of hypersensitivity to ciprofol.

Withdrawal Criteria:

• Endotracheal intubation required during the procedure.
• Voluntary withdrawal requested by the patient or their legal representative.