Preoxygenation is the process of supplying the patient a high inspired fraction of oxygen prior to an airway intervention or induction of general anesthesia. Prolonging safe apnea duration is the primary aim of preoxygenation and preoxygenation is recommended for all patients before induction of general anesthesia.~Atelectasis is the most common postoperative pulmonary complication and is associated with usage of high inspired fraction of oxygen. Modified lung ultrasound scoring is an effective and noninvasive method to determine atelectasis. In this study we will observe the effects of different oxygen concentrations during preoxygenation before induction of general anesthesia in spontaneous breathing patients with modified lung ultrasound scores .~Patients undergoing general anesthesia for elective surgery meeting the criteria will be acknowledged about the study. After written consents are taken patients will be randomised into two groups by coin method. One group will receive %80 oxygen for 3 minutes and other group will receive %100 oxygen for 3 minutes during preoxygenation. Each participants demographic data will be collected. 12 quadrants of thorax divided by midsternal line, anterior axillary and posterior axillary lines will be examined by the usage of modified lung ultrasound score before and at the end of preoxygenation for all individuals. Randomisation, lung ultrasound scoring and preoxygenation will be done by different experienced anesthesiologists so the observers of this study would be blinded for the results. Patients will be blinded for the concentration of oxygen. Modified lung scores of each group would be compared at the end of the study.
The goal of this study is to observe the effects of different oxygen concentrations during preoxygenation in spontaneous breathing patients with modified lung ultrasound scores before induction of general anesthesia. Preoxygenation is a routine and recommended procedure for patients undergoing general anesthesia. Atelectasis is a common side effect of general anesthesia and usage of high concentration oxygen is a probable cause of it. Using lower oxygen concentrations in preoxygenation may help reducing the atelectasis and it can be assessed by lung ultrasound.