Effects of High Flow Humidified Oxygen on Umbilical Artery Acid-base Balance in Cesarean Section Under Spinal Anesthesia

The Effectiveness of Binaural Beats on Midazolam Requirement During Cesarean Section With Spinal Anesthesia

Spinal anesthesia is the most commonly used anesthetic technique for cesarean section in developed countries, but vasodilation and a decrease in systemic vascular resistance caused by sympathetic blockade result in hypotension in 7-74% of parturients. The fetus receives oxygen from the mother via uteroplacental blood flow, and because uteroplacental circulation during pregnancy has minimal autoregulation, uterine blood flow changes in proportion to maternal blood pressure. Therefore, a reduction in uterine blood flow due to maternal hypotension can lead to fetal hypoxia or acidosis and is associated with low Apgar scores after birth.

Oxygen administration may offer potential benefits, such as improving maternal cerebral perfusion and preventing fetal ischemic injury, and thus low-flow oxygen via a conventional nasal cannula is commonly used. However, there are few studies evaluating the effects of high-flow oxygen administration on fetal well-being during cesarean section under spinal anesthesia. Low-flow oxygen delivery through a conventional nasal cannula, which is commonly used during cesarean section under spinal anesthesia, results in a fraction of inspired oxygen (FiO₂) of less than 40% due to dilution with ambient air. In contrast, OptiFlow THRIVE (Fisher and Paykel Healthcare, Panmure, Auckland, New Zealand) is a device capable of delivering high-flow oxygen through a nasal interface, allowing administration of 100% oxygen to the mother and potentially providing greater protection against fetal ischemic injury. Delivering non-humidified oxygen at flow rates above 10 L/min causes significant discomfort in awake patients, but OptiFlow THRIVE passes the gas through a heated humidification chamber immediately before delivery, enabling the administration of warmed and humidified oxygen even at high flow rates. Therefore, this study aims to compare high-flow nasal cannula oxygen therapy initiated upon operating room admission with conventional low-flow nasal cannula oxygen therapy during cesarean section under spinal anesthesia, assessing their effects on maternal hemodynamic parameters and, ultimately, on fetal acid-base status.

Study Overview

• Status: Not yet recruiting
• Conditions: Pregnancy; Cesarean Section; Spinal Anesthesia
• Intervention / Treatment: Device: high-flow nasal oxygen; Device: conventional nasal cannula oxygen

• Study Type: Interventional
• Enrollment (Estimated): 200
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Seung Hyun Kim, Professor; Phone Number: 82-10-3292-2351; Email: anesshkim@yuhs.ac

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Pregnant women aged 20 years or older with American Society of Anesthesiologists (ASA) physical status class 2-3 who are scheduled to undergo cesarean section under spinal anesthesia.

Exclusion Criteria:

A. Emergency surgery B. Patients in whom massive hemorrhage is anticipated, such as those with placenta previa C. Multiple pregnancy, preterm birth at less than 36 weeks of gestation, intrauterine growth restriction, or fetal anomalies D. History of hospitalization for preterm labor within the past 4 weeks requiring tocolytic therapy E. Respiratory diseases requiring oxygen therapy (e.g., moderate or severe asthma, chronic obstructive pulmonary disease) F. Individuals who are unable to read the consent form (e.g., illiterate individuals or foreigners who cannot read Korean)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Supportive Care
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: high-flow nasal oxygen group; The group receiving oxygen via a high-flow nasal cannula	Device: high-flow nasal oxygen; All patients will, upon admission to the operating room, be placed in the supine position and connected to standard monitoring. Once patient monitoring has been completed, patients in the high-flow nasal cannula oxygen group will receive 100% oxygen at 50 L/min via OptiFlow THRIVE. Thereafter, patients will be placed in the left lateral decubitus position, and spinal anesthesia will be performed at the lower lumbar level.
Active Comparator: conventional nasal cannula oxygen group; The group receiving oxygen via a conventional nasal cannula	Device: conventional nasal cannula oxygen; All patients will, upon admission to the operating room, be placed in the supine position and connected to standard monitoring. Once patient monitoring has been completed, patients in the conventional nasal cannula oxygen group will receive oxygen at 2 L/min via a nasal cannula. Thereafter, patients will be placed in the left lateral decubitus position, and spinal anesthesia will be performed at the lower lumbar level.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
umbilical arterial base deficit measured immediately after birth.	The attending obstetrician will obtain an umbilical arterial blood sample using a needle immediately after birth (immediately after umbilical cord clamping).	Immediately after birth (i.e., approximately 1 minute after umbilical cord clamping)

Collaborators and Investigators

• Sponsor: Yonsei University

Study record dates

Study Major Dates

• Study Start (Estimated): April 7, 2026
• Primary Completion (Estimated): March 31, 2027
• Study Completion (Estimated): March 31, 2027

Study Registration Dates

• First Submitted: March 31, 2026
• First Submitted That Met QC Criteria: March 31, 2026
• First Posted (Actual): April 7, 2026

Study Record Updates

• Last Update Posted (Actual): April 7, 2026
• Last Update Submitted That Met QC Criteria: March 31, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: 4-2025-1105

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