Nomogram for Prediction of Alveolo-arterial Gradient During One-lung Ventilation

The cause of hypoxia during one-lung ventilation is a common anaesthetic problem seen during thoracic surgery and is associated with increased fraction of shunted blood. This shunt occurs because the lung not participating in respiration stops saturating the blood with oxygen. The importance of our study is to collect some of the patient's parameters on a nomogram in the preoperative period, to predict the shunt fraction that will occur during one-lung ventilation and to make preparations and interventions accordingly.

Study Overview

• Status: Completed
• Conditions: One-lung Ventilation

Detailed Description

The shunt that occurs during one lung ventilation varies for each patient and depends on many parameters. In this study, our aim was to predict the level of shunting during anaesthesia using readily available preoperative data. It is important to predict the hypoxia that will develop due to the shunt and to plan the methods that can be applied to reduce the shunt in terms of patient safety. One of the most reliable data reflecting the shunt level is the gradient of alvelo- arterial oxygen concentration. The calculation of alveolo-arterial oxygen gradient (A-a O2 gradient) is based on easily accessible parameters (pO2, pCO2, FiO2, age). The secondary aim of the study is to follow how the A-a O2 gradient (oxygen difference between alveolar and arterial blood) changes over time during surgery.

Demographic data, planned operation, comorbidities, side of surgery, ASA score, preoperative haemoglobin level, FEV1 (forced expiratory volume in 1 minute), FEV1/FVC (forced expiratory volume in 1 minute/forced vital capacity) ratio and EF (ejection fraction) will be recorded before surgery.FEV1, FEV1/FVC ratio values will be measured by spirometry test. Spirometry is a preoperative test routinely performed in all patients undergoing one lung ventilation. EF will be measured by preoperative echocadiography, which is also performed during the preoperative preparation of all patients scheduled for lung surgery. Patients undergoing VATS (video-assisted thoracoscopy) surgery with planned lung resection, lobectomy, pulmonectomy, segmentectomy etc. will be included in the study and all will be operated in the lateral decubitus position.

Once the patient is on the operating table, routine haemodynamic monitoring (heart rate, non-invasive blood pressure and blood oxygen saturation) will be performed.

The patient will then have an arterial cannula inserted for invasive arterial monitoring. It is a routine practice in major surgeries for blood gas monitoring, haemorrhage monitoring and monitoring of sudden blood pressure fluctuations. After insertion of the arterial cannula, blood gas will be taken in room air and arterial pO2 (partial oxygen pressure), arterial pCO2 (partial carbon dioxide pressure) and arterial SpO2 (oxygen saturation) will be recorded. At the same time, a venous blood sample (from any vein in the upper limb) will be taken in room air and vSpO2 (venous blood oxygen saturation) will be recorded. The difference between SpO2 of arterial and venous blood is determined as Delta-SpO2 and is a specific parameter of this study.

All patients will undergo general anaesthesia and orotracheal intubation with a double lumen tube.

For anaesthesia induction, 1 mcg/kg fentanyl, 2 mg/kg propofol and 0.6 mg/kg rocuronium will be administered .After adequate mask ventilation and complete muscle relaxation, a double lumen intubation tube will be placed into the trachea by direct laryngoscopy. After the position of the tube and whether it is in the correct bronchus is supported by bronchoscopy, the patient will be connected to the mechanical ventilator and lateral decubitus (provided that the side to be operated on remains on top) will be given. Ventilator parameters will be selected the same for all patients. During two-lung ventilation, tidal volume 8 ml/kg, respiratory rate 12, peep 5, and FiO2 (fraction of inspired oxygen) = 60%. During one-lung ventilation, tidal volume will be set to 6 ml/min, respiratory rate 15, peep 5, and FiO2 = 70%. All patients will be ventilated in volume control mode.

At this stage, EtCO2 (end-tidal carbon dioxide) will be measured separately in both lungs. For this, first the airway from the lower lung will be clamped and the EtCO2 value will be recorded (dEtCO2 - dependent lung EtCO2). Then, vice versa, the airway from the lower lung will be clamped and the EtCO2 value obtained (ndEtCO2 - non-dependent lung EtCO2) will be recorded. The difference between these two values, D-EtCO2 (delta - end-tidal carbon dioxide) will be added to the data.

After these steps, one-lung ventilation will be started and the first A-a oxygen gradient will be recorded 30 minutes after initiation of OLV. The consequent calculations of OLV will be made every 30 minutes until the end of the surgery. The consequent measurements are necessary for estimation the A-a gradient change over time.

• Study Type: Observational
• Enrollment (Actual): 40

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Maltepe
    • Istanbul, Maltepe, Turkey (Türkiye), 34844
      • Bezmialem Vakif University Dragos Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study includes patients with pulmonary diseases, indicated for surgery. Among them are pulmonectomy, segmentectomy, lobectomy or wedge resections. All these types of surgery require one-lung (non-operating lung) ventilation. The patients should be electively operated, aged more that 18 years and must have no other pulmonary conditions (like fibrosis, pneumonia, lung oedema or interstitial lung disease) that could interfere with Alveolo-arterial gradient calculations.

Description

Inclusion Criteria:

• Patients scheduled for elective VATS surgery.
• Age over 18 years.
• ASA 1-4 patients.

Exclusion Criteria:

• Patient refusal.
• Age below 18 years.
• Conditions that may impair oxygen diffusion: pulmonary oedema, fibrosis, interstitial lung disease, pneumonia.
• Emergency surgery.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Video assisted thoracoscopic surgery patients; Patients, assigned for elective lung surgery, older than 18 years and requiring one-lung ventilation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Alveolo-arterial gradient	The gradient of oxygen concentration between alveoli and arterial blood, achieved after patient switch from double lung to one lung lung ventilation. Is calculated automatically, based on oxygen tension in arterial and venous blood, which measured by blood gas analysis.	30 mins after intubation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Alveolo-arterial gradient change	The gradient of oxygen concentration between alveoli and arterial blood, achieved after patient switch from double lung to one lung lung ventilation. It is measured be blod gas analysis. The secondary outcome involves the changes of the first outcome throughout the surgery and is measured every 30 minutes	After switching to one lung ventilation

Collaborators and Investigators

• Sponsor: Bezmialem Vakif University
• Collaborators: Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital
• Investigators: Principal Investigator: Nigar Kangarli, MD, Anesthesiology and Reanimation Department, Specialist

Publications and helpful links

General Publications

• Karzai W, Schwarzkopf K. Hypoxemia during one-lung ventilation: prediction, prevention, and treatment. Anesthesiology. 2009 Jun;110(6):1402-11. doi: 10.1097/ALN.0b013e31819fb15d.
• Parab SY, Chatterjee A, Saxena RS. The utility of gradient of end-tidal carbon dioxide between two lungs in lateral decubitus position in predicting a drop in oxygenation during one-lung ventilation in elective thoracic surgery- A prospective observational study. Indian J Anaesth. 2021 Oct;65(10):744-749. doi: 10.4103/ija.ija_591_21. Epub 2021 Oct 29.
• Alday E, Nieves JM, Planas A. Oxygen Reserve Index Predicts Hypoxemia During One-Lung Ventilation: An Observational Diagnostic Study. J Cardiothorac Vasc Anesth. 2020 Feb;34(2):417-422. doi: 10.1053/j.jvca.2019.06.035. Epub 2019 Jun 28.

Study record dates

Study Major Dates

• Study Start (Actual): June 1, 2024
• Primary Completion (Actual): November 1, 2024
• Study Completion (Actual): November 1, 2024

Study Registration Dates

• First Submitted: April 17, 2024
• First Submitted That Met QC Criteria: April 18, 2024
• First Posted (Actual): April 19, 2024

Study Record Updates

• Last Update Posted (Actual): December 24, 2025
• Last Update Submitted That Met QC Criteria: December 18, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: One lung ventilation; Nomograms; Alveolo-arterial gradient
• Other Study ID Numbers: Nkangarli001

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No