Correcting Hypocapnia in Aneurysmal Subarachnoid Hemorrhage.

NCT ID: NCT07343232

Last Updated: 2026-01-15

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Total Enrollment: 80 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2026-01-01
• Study Completion Date: 2026-10-30

Brief Summary

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.

Detailed Description

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.

Conditions

Aneurysmal Subarachnoid Hemorrhage (aSAH)

Study Design

• Observational Model Type: COHORT
• Study Time Perspective: PROSPECTIVE

Study Groups

Normobaric Facemask Oxygen

Patients who received oxygen via a rebreathing facemask (ensuring no one-way valve is present), with a fractional inspired oxygen (FiO2) of 25-40% and an oxygen flow rate of ≤ 5 L/min.

Normobaric Facemask Oxygen

Intervention Type: 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

Patients who received oxygen via nasal cannula or did not receive oxygen therapy.

control group

Intervention Type: 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.

Interventions

Normobaric Facemask Oxygen

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.

Intervention Type: BEHAVIORAL

control group

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.

Intervention Type: BEHAVIORAL

Eligibility Criteria

Inclusion Criteria

1. Age > 18 years.

2. 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).

3. Hunt-Hess grade II-IV.

4. Presence of hypocapnia on arterial blood gas analysis, defined as PaCO2 < 35 mmH;

5. PaO2 > 90 mmHg.

Exclusion Criteria

1. 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;

2. Primary respiratory diseases (e.g., chronic obstructive pulmonary disease, severe asthma) known to cause chronically elevated baseline PaCO2;

3. Severe acid-base disturbances other than respiratory alkalosis.

4. Severe cardiac insufficiency, severe hepatic or renal dysfunction, malignant tumors, or other severe comorbidities that significantly impact prognosis;

5. Before the onset of the disease, the mRS score was greater than 2, and there were other factors causing disability.

6. Life expectancy < 3 months;

7. Any other condition deemed by the investigator to pose a high risk warranting exclusion.

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

The Chinese University of Hong Kong, Shenzhen

OTHER

Sponsor Role: lead

Responsible Party

Renzhi Wang

director of department

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Renzhi Wang, MD

Role: STUDY_CHAIR

CUHK-Shenzhen

Xinyu Yang

Role: PRINCIPAL_INVESTIGATOR

CUHK-Shenzhen

Locations

School of Medicine Chinese University of Hong Kong-SHENZHEN

Shenzhen, Guangdong, China

Countries

China

Central Contacts

Xinyu Yang, MD

Role: CONTACT

cuhkshzhyang@outlook.com

18622766038

Facility Contacts

Xinyu Yang, MD

Role: primary

cuhkshzhyang@outlook.com

18622766038

References

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Reference Type: RESULT

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Reference Type: RESULT

PMID: 34331211 (View on PubMed)

Su R, Li HL, Wang YM, Zhang L, Zhou JX. Association of dynamic changes in arterial partial pressure of carbon dioxide with neurological outcomes in aneurysmal subarachnoid hemorrhage. Heliyon. 2024 Oct 10;10(20):e39197. doi: 10.1016/j.heliyon.2024.e39197. eCollection 2024 Oct 30.

Reference Type: RESULT

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Carrera E, Schmidt JM, Fernandez L, Kurtz P, Merkow M, Stuart M, Lee K, Claassen J, Sander Connolly E, Mayer SA, Badjatia N. Spontaneous hyperventilation and brain tissue hypoxia in patients with severe brain injury. J Neurol Neurosurg Psychiatry. 2010 Jul;81(7):793-7. doi: 10.1136/jnnp.2009.174425. Epub 2009 Dec 3.

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Reference Type: RESULT

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Coles JP, Minhas PS, Fryer TD, Smielewski P, Aigbirihio F, Donovan T, Downey SP, Williams G, Chatfield D, Matthews JC, Gupta AK, Carpenter TA, Clark JC, Pickard JD, Menon DK. Effect of hyperventilation on cerebral blood flow in traumatic head injury: clinical relevance and monitoring correlates. Crit Care Med. 2002 Sep;30(9):1950-9. doi: 10.1097/00003246-200209000-00002.

Reference Type: RESULT

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Robba C, Battaglini D, Abbas A, Sarrio E, Cinotti R, Asehnoune K, Taccone FS, Rocco PR, Schultz MJ, Citerio G, Stevens RD, Badenes R; ENIO collaborators. Clinical practice and effect of carbon dioxide on outcomes in mechanically ventilated acute brain-injured patients: a secondary analysis of the ENIO study. Intensive Care Med. 2024 Feb;50(2):234-246. doi: 10.1007/s00134-023-07305-3. Epub 2024 Jan 31.

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Reference Type: RESULT

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Other Identifiers

CUHKShenzhen

Identifier Type: -

Identifier Source: org_study_id