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

Official title

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

Overview

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.

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

Interventions

• 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

Primary outcome measures

• 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)]

Secondary outcome measures (4)

• 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)]
• 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)]
• 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)]
• 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)]

Eligibility criteria

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Observational model

Cohort

Study locations

France · 1 center

• Centre d'Oxygénothérapie Hyperbare du CHU de Lille — Lille

Identifiers

NCT: NCT07492030 · 2025_0047 · IDRCB

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗