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NCT Number: NCT07492030

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

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.

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Key information

Conditions

Necrotizing Fascitis Cellulitis Connective Tissue Diseases Fasciitis Fasciitis, Necrotizing Infections Inflammation Musculoskeletal Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Sepsis Septic Shock Shock Shock, Septic Skin Diseases, Infectious Skin and Connective Tissue Diseases Suppuration Systemic Inflammatory Response Syndrome

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

About this study

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

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

echography

Other

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

Primary outcomes

  1. Area under the receiver operating characteristic (ROC) curve constructed from central venous-arterial carbon dioxide tension difference measurements

    Time frame: After 15 minutes at maximum treatment pressure (T1)

    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

Secondary outcomes

  1. 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.

    Time frame: 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)

    The concordance between the two variables will be measured using Cohen's Kappa coefficient for each of the four time points.

  2. 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.

    Time frame: 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)

    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.

  3. 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.

    Time frame: After 15 minutes at maximum treatment pressure (T1)

    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.

  4. 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.

    Time frame: 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)

    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

Study contacts

Contact information is provided by the study sponsor or research team.

Nicolas DOGNON, Doctor

CONTACT

[email protected]

33 3 20 44 55 50

Sponsors and collaborators

Lead sponsor

University Hospital, Lille

Other

Collaborators

  • HyperbaricCare
  • Santelys Association

Registry information

Official study title

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

Acronym: SEPTICO2HBO

Important dates

Study start
2026
Primary completion
2027
Study completion
2028
First posted
Mar 25, 2026
Registry last updated
May 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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