Comparison of Oxygen Reserve Index and Spirometry in Predicting Respiratory Complications After Coronary Artery Bypass Surgery

NCT07063277 | Completed

• 2 other identifiers: Ankara Bilkent City Hospital 2TABED 1-25-1274
• Study Type: interventional
• Target: 142
• Locations: 1 country
• Sites: 1

Brief Summary

Coronary artery disease (CAD) is one of the most common cardiac conditions, primarily caused by atherosclerosis. Studies have shown that environmental factors such as lifestyle, diet, genetics, and air pollution contribute to the increasing prevalence of atherosclerosis. Despite advances in non-invasive and medical therapies, coronary artery bypass grafting (CABG) remains a definitive treatment in many cases. CABG is commonly performed using cardiopulmonary bypass (CPB), which increases the risk of additional complications. Among postoperative complications, pulmonary events are the most frequent and are closely associated with increased morbidity and mortality. Postoperative pulmonary complications (PPCs) significantly raise healthcare costs, prolong hospital stays, and worsen patient outcomes. Cardiac surgery increases susceptibility to PPCs through factors such as sternotomy, CPB, myocardial protection via hypothermia, and phrenic nerve injury. These factors impair thoracic compliance, diaphragm movement, and mucociliary function. Mechanical ventilation further contributes through inflammatory responses that may cause barotrauma and volutrauma. The incidence of PPCs varies from 1.96% to 43.7%, depending on patient characteristics, surgical type, and diagnostic criteria. With an aging population and more high-risk patients undergoing surgery, the incidence of PPCs is expected to rise. Reported preoperative risk factors include advanced age, active or recent smoking, BMI \>25, heart failure, prior myocardial infarction, chronic lung disease, type 2 diabetes mellitus, hypertension, and ASA score \>2. Intraoperative factors include prolonged anesthesia, CPB duration \>95 minutes, multiple grafts, and use of the internal mammary artery. Postoperative contributors include prolonged ventilation, nasogastric tube use, and insufficient nursing care. Common PPCs include atelectasis, pneumonia, bronchospasm, pulmonary embolism, pleural effusion, acute respiratory distress syndrome (ARDS), pneumothorax, hemothorax, and transfusion-related acute lung injury (TRALI). Atelectasis is observed in 30-72% of cases on postoperative chest X-rays. TRALI is the leading cause of transfusion-related death and is characterized by hypoxia and bilateral pulmonary infiltrates. Pleural effusions are associated with low BMI, female sex, atrial fibrillation, heart failure, valve surgery, and anticoagulant use. Phrenic nerve injury, often resulting from internal thoracic artery dissection or cold-induced damage during myocardial protection, leads to unilateral diaphragmatic dysfunction. Hospital-acquired infections, particularly pneumonia, are among the most common and costly non-cardiac complications following cardiac surgery. Pneumonia occurs in 2.4%-20% of cases, while ventilator-associated pneumonia affects 35.2% of patients intubated longer than 48 hours. ARDS is the most severe PPC, involving widespread alveolar injury, endothelial disruption, and non-cardiogenic pulmonary edema. Tension pneumothorax may also occur after chest tube removal. Spirometry is a standard preoperative test used to assess lung function, primarily through FEV₁ and FVC values. These measurements help detect obstructive or restrictive defects. FEV₁/FVC \<70% has been identified as an independent risk factor for PPCs. However, spirometry's predictive value is limited. A systematic review by Dankert et al. reported sensitivities ranging from 38% to 84% and specificities from 55% to 99%. Combined data yielded a sensitivity of 62%, specificity of 70%, and an area under the curve (AUC) of 0.74. Pulse oximetry alone cannot reliably indicate PaO₂ above 100 mmHg or provide information on oxygen reserve. The Oxygen Reserve Index (ORI) is a novel, continuous, and non-invasive parameter that evaluates oxygenation status in the mild hyperoxic range (PaO₂ 100-200 mmHg). ORI values range from 0.00 to 1.00 and correlate with changes in PaO₂. ORI \>0.24 corresponds to PaO₂ ≥100 mmHg when SpO₂ exceeds 98%, while ORI \>0.55 may indicate PaO₂ ≥150 mmHg. A declining ORI trend approaching 0.24, despite SpO₂ \>98%, can signal impending hypoxemia. Given the substantial impact of PPCs on postoperative outcomes and the limitations of spirometry in accurately predicting these complications, there is a need for more reliable preoperative assessment tools. The present study aims to compare the diagnostic performance of the Oxygen Reserve Index and spirometry in predicting postoperative respiratory complications in patients undergoing coronary artery bypass surgery. The goal is to identify a more accurate and effective method for preoperative pulmonary risk stratification.

Conditions

Coronary Arterial Disease (CAD); Coronary Artery Bypass Graft (CABG); Postoperative Pulmonary Complication

Keywords

Postoperative Pulmonary Complications; Coronary Artery Bypass Grafting; Oxygen Reserve Index; Spirometry; Cardiac Surgery Risk Assessment

Outcome Measures

Primary Outcomes (1)

• Incidence of Postoperative Respiratory Complications

  Postoperative respiratory complications, including but not limited to collapse of part or all of a lung (atelectasis), lung infection (pneumonia), the need for continued use of a breathing machine for an extended period after surgery (prolonged mechanical ventilation), or abnormalities in oxygen levels in the blood (oxygenation disorders), will be systematically assessed during the first 48 hours following the surgical procedure. Each event will be evaluated based on clinical symptoms such as shortness of breath, abnormal breath sounds, or decreased oxygen saturation. Additional confirmation will be obtained through diagnostic tools including chest imaging (such as chest X-ray), arterial blood gas analysis, and ventilator parameters. The presence, timing, and severity of each complication will be documented, as well as any medical or mechanical respiratory support required (such as supplemental oxygen, non-invasive ventilation, or reintubation)

  Postoperative 48 hours

Secondary Outcomes (8)

• Preoperative Peak ORI Value

  Preoperative period (within 24 hours prior to surgery)

• FEV₁ (Forced Expiratory Volume in 1 second)

  Preoperative period (within 24 hours prior to surgery)

• Intraoperative Respiratory Complications

  During surgery

• Intraoperative Hemodynamic or Surgical Complications

  During surgery

• Duration of Intensive Care Unit and Total Hospital Stay

  From the date of surgery until ICU and hospital discharge, assessed up to 180 days

Study Arms (1)

Preoperative Evaluation with ORI and Spirometry

EXPERIMENTAL

All participants in this arm will undergo preoperative evaluation using two non-invasive methods: the Oxygen Reserve Index (ORI) and spirometry. ORI will be measured via a fingertip pulse co-oximetry sensor, reflecting oxygen reserve within the PaO₂ range of 100-200 mmHg. Measurements will be taken during routine preoxygenation with room air and supplemental oxygen. Spirometry will be conducted according to standard pulmonary function testing protocols and will include FEV₁, FVC, and FEV₁/FVC ratio. The aim is to assess and compare the predictive value of ORI and spirometry for identifying postoperative respiratory complications in patients undergoing coronary artery bypass grafting (CABG). No therapeutic intervention will be applied.

Device: Preoperative Evaluation with ORI and Spirometry

Interventions

Preoperative Evaluation with ORI and Spirometry DEVICE

All participants in this single-arm diagnostic study will undergo preoperative evaluation involving two non-invasive respiratory assessment methods: the Oxygen Reserve Index (ORI) and spirometry. ORI will be measured using a multi-wavelength pulse co-oximetry sensor placed on the patient's fingertip. This sensor provides a continuous, real-time index (ranging from 0.00 to 1.00) that reflects the patient's oxygen reserve within a PaO₂ range of approximately 100-200 mmHg. Spirometry will be performed using standard pulmonary function testing protocols. Each patient will be instructed to perform forced expiratory maneuvers to obtain parameters including forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and the FEV₁/FVC ratio. These values will be recorded prior to surgery and interpreted according to internationally accepted reference ranges.

Preoperative Evaluation with ORI and Spirometry

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Undergoing elective coronary artery bypass grafting (CABG) surgery.
• Aged 18 years or older at the time of enrollment.
• Provided written informed consent to participate in the study.
• Medically stable and cooperative for preoperative respiratory assessments (ORI and spirometry).

You may not qualify if:

• Refusal to participate or failure to provide informed consent.
• Age under 18 years.
• Left ventricular ejection fraction below 40% on preoperative evaluation.
• Presence of cognitive impairment or psychiatric disorders preventing cooperation (e.g., dementia, Alzheimer's disease).
• Severe anemia defined as hemoglobin level below 8 g/dL.
• Undergoing emergency surgery rather than elective CABG.
• Anatomical or mechanical obstruction that may impair nasal oxygenation (e.g., severe nasal septum deviation, presence of a nasogastric tube).

Sponsors & Collaborators

• Ankara Bilkent Sehir Hastanesi: lead

Study Sites (1)

Ankara Bilkent City Hospital

Ankara, Turkey (Türkiye)

Location

Related Publications (9)

• Scheeren TWL, Belda FJ, Perel A. The oxygen reserve index (ORI): a new tool to monitor oxygen therapy. J Clin Monit Comput. 2018 Jun;32(3):379-389. doi: 10.1007/s10877-017-0049-4. Epub 2017 Aug 8.

  PMID: 28791567 RESULT

• Chen ST, Min S. Oxygen reserve index, a new method of monitoring oxygenation status: what do we need to know? Chin Med J (Engl). 2020 Jan 20;133(2):229-234. doi: 10.1097/CM9.0000000000000625.

  PMID: 31904726 RESULT

• Dankert A, Dohrmann T, Loser B, Zapf A, Zollner C, Petzoldt M. Pulmonary Function Tests for the Prediction of Postoperative Pulmonary Complications. Dtsch Arztebl Int. 2022 Feb 18;119(7):99-106. doi: 10.3238/arztebl.m2022.0074.

  PMID: 34939921 RESULT

• Yoshimi K, Oh S, Suzuki K, Kodama Y, Sekiya M, Seyama K, Fukuchi Y. Impact of Airflow Limitation on Comorbidities and Postoperative Complications in Patients Undergoing Thoracic Surgery: A Retrospective Observational Study. Ann Thorac Cardiovasc Surg. 2016 Jun 20;22(3):146-52. doi: 10.5761/atcs.oa.15-00301. Epub 2016 Mar 1.

  PMID: 26935262 RESULT

• Park HJ, Kim SM, Kim HR, Ji W, Choi CM. The value of preoperative spirometry testing for predicting postoperative risk in upper abdominal and thoracic surgery assessed using big-data analysis. J Thorac Dis. 2020 Aug;12(8):4157-4167. doi: 10.21037/jtd-19-2687.

  PMID: 32944327 RESULT

• Tanner TG, Colvin MO. Pulmonary Complications of Cardiac Surgery. Lung. 2020 Dec;198(6):889-896. doi: 10.1007/s00408-020-00405-7. Epub 2020 Nov 11.

  PMID: 33175990 RESULT

• Jensen L, Yang L. Risk factors for postoperative pulmonary complications in coronary artery bypass graft surgery patients. Eur J Cardiovasc Nurs. 2007 Sep;6(3):241-6. doi: 10.1016/J.EJCNURSE.2006.11.001. Epub 2007 Mar 7.

  PMID: 17347049 RESULT

• Thanavaro J, Taylor J, Vitt L, Guignon MS, Thanavaro S. Predictors and outcomes of postoperative respiratory failure after cardiac surgery. J Eval Clin Pract. 2020 Oct;26(5):1490-1497. doi: 10.1111/jep.13334. Epub 2019 Dec 25.

  PMID: 31876045 RESULT

• Mali S, Haghaninejad H. Pulmonary complications following cardiac surgery. Arch Med Sci Atheroscler Dis. 2019 Dec 31;4:e280-e285. doi: 10.5114/amsad.2019.91432. eCollection 2019.

  PMID: 32368683 RESULT

MeSH Terms

Interventions

Spirometry

Intervention Hierarchy (Ancestors)

Respiratory Function Tests; Diagnostic Techniques, Respiratory System; Diagnostic Techniques and Procedures; Diagnosis

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Anesthesiology and Reanimation Doctor, Principal Investigator

Study Record Dates

• First Submitted: June 25, 2025
• First Posted: July 14, 2025
• Study Start: July 5, 2025
• Primary Completion: December 12, 2025
• Study Completion: January 15, 2026
• Last Updated: February 23, 2026

Record last verified: 2026-02

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)