An observational study in Desaturation, Apnea, Hypoxia and Oxygen Reserve Index, sponsored by Ankara City Hospital Bilkent. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 65 Years to 100 Years. Per ClinicalTrials.gov, last updated 2026-01-08.
Sponsored by Ankara City Hospital Bilkent · Observational
This prospective observational study aims to evaluate the relationship between the Oxygen Reserve Index (ORI) and tolerable apnea time in geriatric patients undergoing elective oncologic surgery under general anesthesia.
Patients aged 65 years and older will be monitored using standard anesthesia monitoring and Masimo Rainbow SET® Pulse CO-Oximetry during anesthesia induction and tracheal intubation.
Tolerable apnea time will be defined as the duration from the end of ventilation after intubation to a decrease in peripheral oxygen saturation (SpO₂) to 94%.
The primary objective is to assess the association between ORI warning time and tolerable apnea time. Secondary objectives include evaluating the association between ORI values, arterial blood gas parameters at predefined time points, and the Clinical Frailty Scale.
This study is a prospective, observational study. Patients aged 65 years and older who are scheduled for elective oncologic surgery at Ankara Bilkent City Hospital will be included. In all patients, the Clinical Frailty Scale will be routinely assessed during the preoperative period.
In this study, tolerable apnea time will be defined as the time until peripheral oxygen saturation (SpO₂), measured by pulse oximetry, decreases to 94%. Although SpO₂ values of 90% and above have been accepted in the literature, the World Health Organization defines normal SpO₂ as 95% and above and considers values of 94% and below as an indication for treatment.
The Oxygen Reserve Index (ORI) ranges from 0 to 1, and the ORI alarm value triggered by the device due to a downward trend will be recorded. ORI is a dimensionless index ranging from 1 (high oxygen reserve) to 0 (no oxygen reserve), which is measured by optically detecting changes in venous oxygen saturation (SvO₂) after arterial oxygen saturation (SpO₂) reaches 100%. ORI is measured using a multi-wavelength pulse co-oximeter placed on a fingertip.
In addition to routine anesthesia monitoring, including electrocardiography, pulse oximetry, and hemodynamic monitoring, patients will also be monitored using Masimo Rainbow SET® Pulse CO-Oximetry. Due to the oncologic nature of the surgeries and the associated risk of bleeding, close hemodynamic monitoring is required; therefore, invasive arterial blood pressure monitoring will be established in all patients before anesthesia induction.
All patients will be preoxygenated with 100% oxygen for 3 minutes. After establishing intravenous access, anesthesia induction will be performed using intravenous propofol at a dose of 2 mg/kg and fentanyl at a dose of 1 µg/kg. Neuromuscular blockade will be achieved with rocuronium at a dose of 0.6 mg/kg.
All patients will be intubated by an experienced anesthesiologist using a videolaryngoscope. Oxygen Reserve Index (ORI) and peripheral oxygen saturation (SpO₂) values will be recorded, and arterial blood gas analyses will be performed at five predefined time points: baseline (initial values), after 3 minutes of preoxygenation, after 2 minutes of bag-mask ventilation following intubation, during apnea when SpO₂ decreases to 94% without ventilation, and after 2 minutes of ventilation with 100% oxygen.
ORI warning time will be defined as the interval from the onset of the ORI alarm to the decrease of SpO₂ to 94%. SpO₂ warning time will be defined as the duration of the decrease in SpO₂ from 97% to 94%.
282 studies on the registry are indexed under Apnea; 54 are open to participants now.
This study's planned enrollment of 44 is below the median of 60 across 78 observational studies indexed under Apnea.
Browse Apnea studies →Ankara City Hospital Bilkent is the lead sponsor of 443 studies on the registry; 111 are open to participants now.
Counted across the registry records on this site, refreshed daily.
It will be studied in patients over the age of 65.
Inclusion criteria for the files/records/materials to be included in the study:
Records of patients aged 65 years and older, classified as I-III, who are scheduled for elective oncologic surgery.
Exclusion criteria for the files/records/materials to be included in the study:
Records of patients with advanced coronary artery disease; advanced heart failure and/or valvular heart disease; carotid artery stenosis; below 30%; rapid atrial fibrillation; (BMI) greater than 35 kg/m²; anticipated difficult airway; advanced-stage ; or dementia.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The primary outcome measure is the association between Oxygen Reserve Index (ORI) warning time and tolerable apnea time. ORI warning time is defined as the time interval from the onset of the ORI alarm triggered by a downward trend to the decrease of per
The primary outcome measure is the association between Oxygen Reserve Index (ORI) warning time and tolerable apnea time. ORI warning time is defined as the time interval from the onset of the ORI alarm triggered by a downward trend to the decrease of peripheral oxygen saturation (SpO₂) to 94%. Tolerable apnea time is defined as the duration from the end of ventilation after tracheal intubation to the decrease of SpO₂ to 94%.
Time frame: Peri-induction period at predefined time points baseline; after 3 minutes of preoxygenation; after 2 minutes of bag-mask ventilation following intubation; during apnea at SpO₂ 94%; and after 2 minutes of ventilation with 100% oxygen
Started Dec 2025 (actual). Primary completion is estimated for Feb 2026, 2 months after the start.
Of 35 observational studies under Apnea, half reached primary completion within 23 months of starting (the median), counting those still running; a quarter within 14 and three quarters within 38. This study's planned 2 months is below that.
How these figures are worked out, and which studies are left out of them.
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