Preoxygenation

The goal of this observational study is to evaluate the relationship between preoperative cardiopulmonary performance indicators and preoxygenation efficiency along with oxygen reserve depletion in patients scheduled for elective surgery under general anesthesia. The main questions it aims to answer are: What is the relationship between Hand Grip Strength (HGS) and the time taken for end-tidal oxygen (EtO\_2) to reach 90% during preoxygenation? What is the relationship between the 6-Minute Walk Test (6MWT) distance and the Oxygen Reserve Index (ORI) depletion time during the apnea period? Participants will be asked to perform the following tasks during their preoperative and intraoperative care: Complete a 6-Minute Walk Test (6MWT) to determine preoperative functional capacity. Perform a Hand Grip Strength (HGS) test using a calibrated hand dynamometer to measure muscle strength. Undergo standardized preoxygenation with 100% oxygen via a tight-fitting face mask in the operating room while end-tidal oxygen (EtO\_2) and Oxygen Reserve Index (ORI) levels are continuously monitored.

The goal of this clinical trial is to evaluate the performance and physiological effects of different preoxygenation devices in healthy adult and pediatric volunteers (children aged 5-12 years). The study aims to determine how these devices influence oxygen delivery, airway pressure, and cardiopulmonary physiology during preoxygenation. The main questions it aims to answer are: * What fraction of inspired oxygen (FiO₂) is delivered by non-rebreather masks (NRM) compared to bag-valve masks (BVM) with and without positive end-expiratory pressure (PEEP)? * How do these devices differ in terms of generated PEEP, inspiratory effort, and their effects on lung ventilation and cardiac function? Researchers will compare NRM, BVM without PEEP, and BVM with PEEP (each with or without supplemental oxygen via nasal cannula) to evaluate differences in oxygenation and physiological effects. Participants will: * Complete multiple 3-minute preoxygenation sessions using each device in randomized order * Breathe spontaneously through each device, with or without additional oxygen via nasal cannula * Undergo non-invasive monitoring of oxygen concentration (FiO₂), respiratory parameters, airway pressures, and ultrasound assessment of the lungs, diaphragm, and heart * Perform a brief breath-holding maneuver to assess airway pressure generation

The purpose of this study is to compare the time required to reach an end-tidal oxygen (EtO2) value of 90% and the time until the Oxygen Reserve Index (ORI) drops below 0.55 during preoxygenation in sarcopenic and non-sarcopenic patients. The study aims to investigate the impact of sarcopenia on the oxygenation process.