The Role of Oxygen Reserve Index (ORi) in Apneic Ventilation

Obesity is a complex and chronic disease that significantly impacts respiratory physiology. It leads to increased work of breathing and reduced compliance of the chest wall. In morbidly obese individuals, there is a marked reduction in total lung capacity, vital capacity, forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). Additionally, due to their elevated metabolic demands, these patients exhibit higher oxygen consumption rates.

The Oxygen Reserve Index (ORi) (Masimo Corp., Irvine, CA, USA) is an advanced, continuous, and non-invasive parameter that provides a relative indication of arterial partial pressure of oxygen (PaO₂).

ORI monitoring can be particularly beneficial in patients at risk for inadequate preoxygenation, those with difficult mask ventilation, hypoxemic patients with aspiration risk, rapid sequence induction scenarios, obese individuals, ICU intubations, and invasive ventilation cases. It has also been shown to provide early warnings of desaturation in select patient groups, contributing to improved patient safety.

Inclusion criteria

• 18-60 years
• ASA 1-2
• Mallampati score <2
• Scheduled for elective laparoscopic cholecystectomy under general anesthesia

Exclusion criteria

• <18 and >60 years
• ASA 3-4
• Initial ORI value below 0.24