Evaluation of the Association Between Fresh Gas Flow Rate During Inhalational Anesthesia and Perioperative Pulmonary Aeration Assessed Using the Lung Ultrasound Score in Patients Undergoing Septoplasty: A Prospective Observational Study

This was a prospective, single-center observational cohort study conducted at Fatih Sultan Mehmet Training and Research Hospital. Adult patients aged 18 to 65 years with American Society of Anesthesiologists physical status I or II who underwent elective surgery for nasal septal deviation under general anesthesia were evaluated.

All participants provided written informed consent before enrollment. Anesthetic management was performed according to routine institutional clinical practice. The fresh gas flow rate was determined independently by the attending anesthesiologist and was not assigned or modified by the research protocol. Participants were subsequently classified into two observational cohorts according to the documented fresh gas flow rate used during inhalational anesthesia: 1 L/min or 3 L/min. No randomization was performed.

Lung ultrasound examinations were performed at five perioperative time points: before induction of anesthesia, after tracheal intubation, before extubation, 15 minutes after admission to the post-anesthesia care unit, and approximately 30 minutes after admission or immediately before discharge from the post-anesthesia care unit.

Lung aeration was evaluated in 12 thoracic regions using a modified lung ultrasound score. Each region was scored from 0 to 3 according to the observed ultrasound pattern. A score of 0 represented normal aeration, while scores of 1, 2, and 3 represented mild, moderate, and severe loss of aeration, respectively. The total score ranged from 0 to 36, with higher scores indicating greater loss of lung aeration.

The primary objective was to compare perioperative changes in the lung ultrasound score between patients receiving fresh gas flow rates of 1 L/min and 3 L/min during routine anesthesia. Additional recorded variables included heart rate, systolic, diastolic, and mean arterial pressure, peripheral oxygen saturation, perfusion index, end-tidal carbon dioxide, inspired and expired oxygen concentrations, body temperature, peak airway pressure, airway resistance, and dynamic lung compliance. Early postoperative findings, including pain intensity, nausea, vomiting, and shivering, were also evaluated in the post-anesthesia care unit.