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NCT Number: NCT07343232

Correcting Hypocapnia in Aneurysmal Subarachnoid Hemorrhage.

Based on the clinical observation that over half of the patients in the management of aneurysmal subarachnoid hemorrhage(aSAH) present with spontaneous hyperventilation, which is significantly associated with delayed cerebral ischemia and poor neurological outcomes, this prospective pilot study is designed to investigate the safety and efficacy of normobaric facemask oxygen for hypocapnia in aSAH.

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Key information

Conditions

Aneurysmal Subarachnoid Hemorrhage (aSAH) Brain Diseases Cardiovascular Diseases Central Nervous System Diseases Cerebrovascular Disorders Hemorrhage Hypocapnia Intracranial Hemorrhages Nervous System Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms Signs and Symptoms Signs and Symptoms, Respiratory Subarachnoid Hemorrhage Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

School of Medicine Chinese University of Hong Kong-SHENZHEN

Shenzhen, Guangdong, 518000, China

Location contact

Xinyu Yang, MD

CONTACT

[email protected]

18622766038

Xinyu Yang, MD

PRINCIPAL_INVESTIGATOR

About this study

Spontaneous hyperventilation (SH) is highly prevalent following aneurysmal subarachnoid hemorrhage (aSAH) and is significantly associated with poor neurological outcomes.The core pathophysiological mechanism involves hypocapnia induced by hyperventilation, which triggers cerebral vasoconstriction and consequently leads to a decrease in cerebral blood flow (CBF).Although this response may transiently reduce intracranial pressure, persistent cerebral vasoconstriction markedly increases the risk of delayed cerebral ischemia (DCI) and secondary brain injury. Therefore, maintaining the arterial partial pressure of carbon dioxide (PaCO2) within the physiological range of mmHg is recommended to minimize the detrimental effects of hypocapnia.

Currently, there is a lack of standardized management strategies for hypocapnia resulting from SH after aSAH. Based on physiological principles, low-flow (<5 L/min) oxygen delivery via a facemask may effectively correct hypocapnia by promoting the rebreathing of carbon dioxide within the dead space of the facemask.10 A randomized controlled trial investigating psychogenic hyperventilation syndrome provides preliminary evidence for this approach, demonstrating that low-flow (3 L/min) facemask oxygen therapy can relieve symptoms more rapidly and improve patient comfort compared to traditional breathing training.11

However, high-level evidence regarding the safety, efficacy, and impact on neurological outcomes of using low-flow facemask oxygen therapy (functioning as a rebreathing mask) as a targeted intervention for correcting hypocapnia in aSAH patients remains scarce. Consequently, this proof-of-concept prospective study aims to systematically evaluate the operational safety and clinical effectiveness of rebreathing facemask oxygen therapy for correcting hypocapnia in patients with aSAH.

Who can participate

Healthy volunteers accepted: No

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

Inclusion criteria

  • Age > 18 years.
  • Confirmed diagnosis of aneurysmal subarachnoid hemorrhage (aSAH), with the presence of an aneurysm verified by computed tomography (CT), CT angiography (CTA), or digital subtraction angiography (DSA).
  • Hunt-Hess grade II-IV.
  • Presence of hypocapnia on arterial blood gas analysis, defined as PaCO2 < 35 mmH;
  • PaO2 > 90 mmHg.

Exclusion criteria

  • Presence of brain herniation or refractory intracranial hypertension, defined as a baseline intracranial pressure (ICP) > 25 mmHg that responds poorly to conventional ICP-lowering therapy;
  • Primary respiratory diseases (e.g., chronic obstructive pulmonary disease, severe asthma) known to cause chronically elevated baseline PaCO2;
  • Severe acid-base disturbances other than respiratory alkalosis.
  • Severe cardiac insufficiency, severe hepatic or renal dysfunction, malignant tumors, or other severe comorbidities that significantly impact prognosis;
  • Before the onset of the disease, the mRS score was greater than 2, and there were other factors causing disability.
  • Life expectancy < 3 months;
  • Any other condition deemed by the investigator to pose a high risk warranting exclusion.

Treatment and study plan

Normobaric Facemask Oxygen

Behavioral

Oxygen is to be delivered via a rebreathing facemask (ensuring no one-way valve is present), with a fractional inspired oxygen (FiO2) of 25-41% and an oxygen flow rate of ≤ 5 L/min.

The goals are to maintain patient SpO2 > 95%, PaCO2 between 35-42 mmHg, and, where feasible (particularly in centers with the capability for monitoring), an intracranial pressure (ICP) of < 15 mmHg.

Control Group

Behavioral

Using nasal cannula for oxygen inhalation or not using oxygen inhalation at all. Monitor and record the patient's SpO2, systolic blood pressure, diastolic blood pressure, PaCO2, and also monitor the intracranial pressure (ICP) at a center with monitoring capabilities.

Primary outcomes

  1. modified Rankin Scale (mRS) >3

    Time frame: 90-day follow-up visit

    The poor neurological outcome was considered to be mRs >3, indicating severe disability or death. The modified Rankin Scale (mRS) is a commonly used scale for measuring the degree of disability or dependence in the daily activities of people who have suffered a stroke or other causes of neurological disability. (Score Description: 0---No symptoms at all. 1---No significant disability despite symptoms; able to carry out all usual duties and activities. 2---Slight disability; unable to carry out all previous activities, but able to look after own affairs without assistance. 3---Moderate disability; requiring some help, but able to walk without assistance. 4--- Moderately severe disability; unable to walk without assistance and unable to attend to own bodily needs without assistance. 5---Severe disability; bedridden, incontinent and requiring constant nursing care and attention. 6---Dead.

  2. Incidence of delayed cerebral injury (DCI)

    Time frame: 30 days after onset

    The presence of new focal neurological signs or a documented decrease in the level of consciousness persisting for at least 1 hour (or a drop of at least 1 point in the total Glasgow Coma Scale score), deemed to be of ischemic origin, after ruling out other causes (such as hydrocephalus, toxic-metabolic disturbances, or seizures); or identification of a new cerebral infarction on CT or MRI imaging.

Secondary outcomes

  1. Montreal Cognitive Assessment (MoCA)

    Time frame: 90-day follow-up visit

    Cognitive function was evaluated using the Montreal Cognitive Assessment (MoCA), a standardized screening tool with scores ranging from 0 to 30, where higher scores indicate better cognitive performance and lower scores reflect greater cognitive impairment. Measure mean score or median compared between groups. And the rate of MoCA score of 20 or less between groups.

  2. Cerebral Vasospasm

    Time frame: Participants will be followed for the duration of the hospital stay, an expected average of 2 weeks

    Incidence of moderate and severe radiographic cerebral vasospasm (catheter angiogram, CTA, MRA) or incidence OR moderate and severe vasospasm by transcranial doppler (TCD) criteria.

  3. Glasgow Coma Score(GCS)

    Time frame: Enrollment, 30 days after onset, and 90-day follow-up visit

    The Glasgow Outcome Scale was used as secondary outcomes. The level of consciousness was assessed using the Glasgow Coma Scale (GCS), a standardized scale ranging from 3 to 15, where higher scores indicate a better neurological status (i.e., a higher level of consciousness), and lower scores reflect more severe impairment.

  4. The modified Rankin Scale (mRS)

    Time frame: 30 days after onset

    Shift analysis of mRS scores at 30 days after onset. The modified Rankin Scale (mRS) is a commonly used scale for measuring the degree of disability or dependence in the daily activities of people who have suffered a stroke or other causes of neurological disability. (Score Description: 0---No symptoms at all. 1---No significant disability despite symptoms; able to carry out all usual duties and activities. 2---Slight disability; unable to carry out all previous activities, but able to look after own affairs without assistance. 3---Moderate disability; requiring some help, but able to walk without assistance. 4--- Moderately severe disability; unable to walk without assistance and unable to attend to own bodily needs without assistance. 5---Severe disability; bedridden, incontinent and requiring constant nursing care and attention. 6---Dead. The higher scores indicate worse functional disability and lower scores reflect better functional independence.

  5. modified Rankin Scale (mRS)

    Time frame: 30 days after onset

    The rate of modified Rankin Scale (mRS) score > 3. The modified Rankin Scale (mRS) is a commonly used scale for measuring the degree of disability or dependence in the daily activities of people who have suffered a stroke or other causes of neurological disability. (Score Description: 0---No symptoms at all. 1---No significant disability despite symptoms; able to carry out all usual duties and activities. 2---Slight disability; unable to carry out all previous activities, but able to look after own affairs without assistance. 3---Moderate disability; requiring some help, but able to walk without assistance. 4--- Moderately severe disability; unable to walk without assistance and unable to attend to own bodily needs without assistance. 5---Severe disability; bedridden, incontinent and requiring constant nursing care and attention. 6---Dead. The higher scores indicate worse functional disability and lower scores reflect better functional independence.

  6. Barthel Index (BI) score

    Time frame: 90-day follow-up visit

    Activities of daily living were evaluated using the Barthel Index (BI), a functional assessment scale ranging from 0 to 100, where higher scores indicate greater independence in daily activities and lower scores reflect more severe functional dependence.

  7. All-cause mortality

    Time frame: 90-day follow-up visit

    Death caused by any reason.

  8. Complication of severe dependent survival

    Time frame: 90-day follow-up visit

    eg, chest or other infections

  9. Treated aneurysm rebleeding

    Time frame: 90-day follow-up visit

    Treated aneurysm rebleeding

  10. Probable or definite bleed from another aneurysm

    Time frame: 90-day follow-up visit

    Probable or definite bleed from another aneurysm

  11. Incidence of adverse events

    Time frame: 90-day follow-up visit

    Ischaemic stroke, Other intracranial haemorrhage, Cardiac, Cancer, Suicide, Renal failure, Infections not related to dependent survival, Other causes (eg, trauma, perforated ulcer, pulmonary embolus, neurodegenerative)

Study contacts

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

Xinyu Yang, MD

CONTACT

[email protected]

18622766038

Sponsors and collaborators

Lead sponsor

The Chinese University of Hong Kong, Shenzhen

Other

Registry information

Official study title

Safety and Efficacy of Normobaric Facemask Oxygen for Hypocapnia in Aneurysmal Subarachnoid Hemorrhage(FOCAL): A Prospective, Multicenter, Proof-of-concept Pilot Study

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Jan 15, 2026
Registry last updated
Jan 15, 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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