Validation of the Use of the Arteriovenous Tension Difference in CO2 Under Hyperbaric Conditions (SEPTICO2HBO)

Use of Central Venous-arterial Carbon Dioxide Tension Difference to Diagnose Low Cardiac Output in Patients With Septic Shock Undergoing Hyperbaric Oxygen Therapy

The central venous-arterial carbon dioxide tension difference is used daily in intensive care to establish peripheral tissue hypoperfusion, mainly mediated by a low cardiac index.

The partial pressures of gases (oxygen, carbon dioxide) increase in the blood of patients breathing 100% oxygen in hyperbaric conditions.

Thus, the validity of this biomarker in situations of acute circulatory failure during a hyperbaric oxygen therapy session has not been established.

The objective of the study is therefore to establish the diagnostic performance of the central venous-arterial carbon dioxide tension difference in the diagnosis of a low cardiac index in patients with septic shock undergoing hyperbaric oxygen therapy for necrotizing fasciitis.

Study Overview

• Status: Not yet recruiting
• Conditions: Septic Shock; Cellulitis; Necrotizing Fascitis
• Intervention / Treatment: Other: Echography

Detailed Description

Adult patients diagnosed with necrotizing fasciitis and receiving OHB treatment for the first time will be offered participation in the study if they meet the following inclusion criteria:

• Diagnosis of necrotizing fasciitis complicated by septic shock as defined by the Surviving Sepsis Campaign
• Indication for HBOT according to the criteria of the 2016 European Consensus Conference
• Patient intubated and ventilated prior to the HBOT session, receiving intravenous sedation at doses sufficient to be in a passive ventilation state
• Patient equipped with a central venous line in the superior vena cava allowing central venous blood gas analysis
• Patient with an arterial catheter allowing arterial blood gas analysis

• Study Type: Observational
• Enrollment (Estimated): 74

Contacts and Locations

• Study Contact: Name: Nicolas DOGNON, Doctor; Phone Number: 33 3 20 44 55 50; Email: nicolas.dognon@chu-lille.fr

Study Locations

• France
  • Lille, France, 59037
    • Centre d'Oxygénothérapie Hyperbare du CHU de Lille
    • Contact: Nicolas DOGNON, Doctor; Phone Number: 33 3 20 44 55 50; Email: nicolas.dognon@chu-lille.fr

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

Adult patients diagnosed with necrotizing dermo-hypodermitis who are receiving OHB treatment for the first time at the Regional Hyperbaric Oxygen Therapy Center at Lille University Hospital, a tertiary referral center where complementary hyperbaric oxygen therapy treatment for necrotizing dermo-hypodermitis in the Hauts-de-France region is centralized.

Description

Inclusion Criteria:

• Diagnosis of necrotizing fasciitis complicated by septic shock as defined by the Surviving Sepsis Campaign
• Indication for HBOT according to the criteria of the 2016 European Consensus Conference
• Patient intubated and ventilated prior to the HBOT session, receiving intravenous sedation at doses sufficient to be in a passive ventilation state
• Patient equipped with a central venous line in the superior vena cava allowing central venous blood gas analysis
• Patient with an arterial catheter allowing arterial blood gas analysis

Exclusion Criteria:

• - Minors
• Pregnant women
• Persons deprived of their liberty (prisoners, persons under guardianship or trusteeship)
• Persons not affiliated with or not covered by a social security system
• Patients on spontaneous ventilation
• Patients without an echocardiographic assessment window (anechoic)
• Severe ARDS according to the Berlin classification
• Technical impossibility of sampling central arterial or venous blood
• Absolute contraindication to hyperbaric oxygen therapy (undrained pneumothorax, unstable angina or acute myocardial infarction, severe asthma attack)

• Relative contraindication to hyperbaric oxygen therapy

  • Respiratory: Chronic respiratory failure, severe pulmonary emphysema
  • Circulatory: Rhythm or conduction disorders
  • Neurological: uncontrolled epilepsy
  • ENT: sinusitis, otitis, chronic rhinitis; laryngocele; acute otitis media; osteospongiosis
  • Ophthalmic: retinal detachment

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Adult patients diagnosed with necrotizing fasciitis and receiving OHB; Adult patients diagnosed with necrotizing fasciitis and receiving OHB treatment for the first time will be offered participation in the study if they meet the following inclusion criteria: Diagnosis of necrotizing fasciitis complicated by septic shock as defined by the Surviving Sepsis Campaign; Indication for HBOT according to the criteria of the 2016 European Consensus Conference; Patient intubated and ventilated prior to the HBOT session, receiving intravenous sedation at doses sufficient to be in a passive ventilation state; Patient equipped with a central venous line in the superior vena cava allowing central venous blood gas analysis; Patient with an arterial catheter allowing arterial blood gas analysis

Other: Echography; Cardiac output is estimated by taking three measurements of the time-velocity integral using pulsed Doppler at the level of the left ventricular outflow tract, known as the subaortic time-velocity integral (TVI). The systolic ejection volume is calculated by multiplying the subaortic TVI by the area of the aortic outflow tract diameter. Cardiac output is calculated by multiplying this systolic ejection volume by the patient's heart rate. The cardiac index is calculated by dividing cardiac output by the patient's calculated body surface area. Blood gas sampled from central arterial and venous catheters at the four stages of the experimental plan Cardiac output and blood gases will be measured: After 15 minutes of ventilation on a hyperbaric ventilator at ambient pressure in the chamber with FIO2 equivalent to that of the intensive care unit (T0).; After 15 minutes at maximum treatment pressure, i.e., 2.5 ATA under FIO2 at 1 (T1); After 75 minutes at the plateau following the star

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Area under the receiver operating characteristic (ROC) curve constructed from central venous-arterial carbon dioxide tension difference measurements	used to define low cardiac output measured as a cardiac index < 2.2 L/min/m² by cardiac echocardiography under hyperbaric oxygenation conditions after 15 min at the maximum treatment pressure of 2.5 ATA under FIO2 at 1 (T1) Maximum treatment pressure i.e., 2.5 ATA under FIO2 at 1	After 15 minutes at maximum treatment pressure (T1)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the concordance at different time points (T0, T1, T2, and T3) between the definition of low cardiac output by cardiac index <2.2 L/min/m² (gold standard) and the Pvc-aCO2 value according to the threshold of 6 mmHg.	The concordance between the two variables will be measured using Cohen's Kappa coefficient for each of the four time points.	After 15 minutes at ambiant pressure in the hyperbaric chamber (T0), after 15 minutes at 2.5 ATA under FIO2 at 1 (T1), after 75 minutes following the start of the session (T2), and 15 minutes after the end of HBOT session (T3)
Compare cardiac index values measured at T0, T1, T2, and T3 according to three pre-specified groups classified according to Pvc-aCO2 values established by Ospina-Tasco´n et al.: < 6 mmHg; (2) 6.0-9.9 mmHg; (3) ≥ 10 mmHg.	The cardiac index will be measured by cardiac echocardiography under hyperbaric oxygenation conditions. The three groups will be determined according to Pvc-aCO2 values established by Ospina-Tasco´n et al.: (1) < 6 mmHg; (2) 6.0-9.9 mmHg; (3) ≥ 10 mmHg.	After 15 minutes at ambiant pressure in the hyperbaric chamber (T0), after 15 minutes at 2.5 ATA under FIO2 at 1 (T1), after 75 minutes following the start of the session (T2), and 15 minutes after the end of HBOT session (T3)
Evaluate the performance of transcutaneous oximetry variations from the subclavian reference electrode after passive leg raising, a non-invasive procedure, as a diagnostic tool for preload dependence.	Area under the receiver operating characteristic (ROC) curve contructed from measurements of transcutaneous oximetry variationsbefore and after passive leg raising (ΔPTcO2). A patient will be considered "preload dependent" if the subaortic ITV measured by echocardiography varies by sup > 10 % under hyperbaric oxygenation conditions after 15 minutes at the maximumtreatment pressure of 2.5 ATA under FIO2 at 1 (T1). The correlation between ΔPTcO2 and the variation in subaortic ITV measured by echocardiography after passive legraising will so also measured.	After 15 minutes at maximum treatment pressure (T1)
Describe clinical parameters related to blood pressures, echocardiographic data and respiratory mechanics changes induced in patients admitted for necrotizing fasciitis complicated by septic shock under hyperbaric oxygen therapy.	at each time point (T0, T1, T2, and T3), will be measured : Systolic/diastolic/mean arterial pressures; Heart rate; Systolic/diastolic/mean pulmonary arterial pressures estimated by transthoracic echocardiography; End-expiratory central venous pressure by transthoracic echocardiography through analysis of the inferior vena cava.; Cardiac index estimated by echocardiography; TAPSE and S' wave,; Mitral flow analysis; Indexed systemic vascular resistance estimated using Ohm's law. (PAM-PVC)/IC; Indexed pulmonary vascular resistance estimated using the formula : RPT = 10 (Vmax IT/VTI p) + 0.16; Right ventriculo-arterial coupling measured by the TAPSE/PAPs ratio; Tidal volume relative to theoretical ideal weight; Adjusted external PEEP and total PEEP; Driving pressure measured as plateau pressure minus total PEEP; Respiratory system compliance measured as Vt/(Pplat - total PEEP); R/I ratio: recruitment-to-inflation ratio; Airway opening pressure	After 15 minutes at ambiant pressure in the hyperbaric chamber (T0), after 15 minutes at 2.5 ATA under FIO2 at 1 (T1), after 75 minutes following the start of the session (T2), and 15 minutes after the end of HBOT session (T3)

Collaborators and Investigators

• Sponsor: University Hospital, Lille
• Collaborators: Santelys Association; HyperbaricCare

Study record dates

Study Major Dates

• Study Start (Estimated): June 15, 2026
• Primary Completion (Estimated): September 15, 2027
• Study Completion (Estimated): March 15, 2028

Study Registration Dates

• First Submitted: March 10, 2026
• First Submitted That Met QC Criteria: March 18, 2026
• First Posted (Actual): March 25, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 11, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: cellulitis; cardiac index; HBO; gapCO2; necrotizing fascitis
• Additional Relevant MeSH Terms: Musculoskeletal Diseases; Pathologic Processes; Connective Tissue Diseases; Infections; Sepsis; Systemic Inflammatory Response Syndrome; Inflammation; Skin Diseases, Infectious; Suppuration; Shock; Pathological Conditions, Signs and Symptoms; Skin and Connective Tissue Diseases; Fasciitis; Shock, Septic; Cellulitis; Fasciitis, Necrotizing; Physical Phenomena; Radiation; Radiation, Nonionizing; Ultrasonic Waves; Sound; High-Energy Shock Waves
• Other Study ID Numbers: 2025_0047; IDRCB (Other Identifier: 2025-A01568-41)

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