Comparison of Different Oxygen Flow Rates During Preoxygenation Using High-Flow Nasal Oxygen

Not Applicable

Recruiting

• Conditions: Airway Anesthesia; Preoxygenation; High Flow Nasal Canula

• Registration Number: NCT06736132
• Lead Sponsor: Region Stockholm

Brief Summary

High-flow nasal oxygen (HFNO) has been used for many years to help people with breathing difficulties in the intensive care and after surgery. More recently, it has become a helpful tool during induction of anaesthesia to prevent oxygen levels from dropping when managing the airway. HFNO is particularly effective at delivering oxygen even when a patient is not breathing (apnoea), making it useful during surgeries on the voice box (larynx) because it eliminates the need for a breathing tube, giving surgeons a clear view.

HFNO is now also being used to prepare patients for anaesthesia (preoxygenation). Research shows that it works just as well as traditional tight-fitting oxygen masks while offering added benefits like better comfort for patients, easier handling for anaesthetists, and a smooth transition to oxygen delivery during apnoea.

One reason HFNO is effective is that it creates a mild pressure in the lungs, called positive end-expiratory pressure (PEEP), which improves oxygen storage in the lungs. This pressure depends on the flow rate of oxygen and is higher when the patient keeps their mouth closed. For every increase of 10 liters per minute in flow rate, HFNO generates 1 cmH2O of PEEP. This pressure helps increase the lung's capacity to hold oxygen, making the process of preoxygenation more efficient.

Most studies on HFNO for preoxygenation have used flow rates of up to 60 liters per minute. However, we don't yet know if higher flow rates could further improve preoxygenation or extend the time patients can safely go without breathing.

Detailed Description

High-flow nasal oxygen (HFNO) has long been employed to address respiratory distress in both the intensive care unit and post-anaesthesia unit. Over the past decade, HFNO has emerged as a valuable tool for preventing oxygen desaturation during airway management in the operating theatre. Notably, HFNO demonstrates effectiveness in oxygenating patients during extended periods of apnoea, providing a reliable method for apnoeic oxygenation. This technique serves as an alternative to mechanical ventilation in laryngeal surgical procedures, offering potential advantages such as a clear operating field for surgeons without the interference of a tracheal tube.

More recently, HFNO has found application in preoxygenation before anaesthesia induction. Studies indicate that the preoxygenation efficacy of HFNO is comparable to that of a standard tight-fitting facemask, with added benefits including enhanced patient comfort, improved ease of use as assessed by anaesthetists, and the potential for a seamless transition to apnoeic oxygenation.

One of the suggested mechanisms contributing to the favourable outcomes observed with HFNO in managing patients with respiratory distress is a flow-dependent positive end-expiratory pressure (PEEP) effect. When patients breathe with a closed mouth, HFNO appears to generate a PEEP effect of 1 cmH2O for every 10 l.min-1 of flow. Prior data has demonstrated that an elevated PEEP leads to a greater functional residual capacity (FRC) and improved preoxygenation effectiveness.

Previous studies investigating HFNO for preoxygenation have used flow rates ≤ 60 l.min-1. Consequently, the impact of higher flow rates on preoxygenation effectiveness and the extension of safe apnoea time remains uncertain.

In this randomised prospective study, we aim to investigate the effectiveness of preoxygenation from HFNO using different flow rates. Seventy-five patients (25 per group) scheduled for elective surgery at the Karolinska University Hospital, will be recruited. After a signed consent, the subject will be enrolled and randomised to preoxygenation using HFNO at flow rates of 45 l/min, 70 l/min or 95 l/min.

Routine perioperative monitoring, such as peripheral oxygen saturation (SpO2) and non-invasive blood pressure will be performed. Preoperatively, an arterial catheter will be inserted. An arterial blood gas will be attained before preoxygenation for base line data regarding PaCO2, PaO2 and pH.

To enable lung impedance measurement, all subjects will be applied an appropriately sized circumferential 16-electrode belt around the torso between the fourth and sixth intercostal spaces.

Patients will be positioned supine with the head elevated at 15 degrees. All groups will undergo preoxygenation using HFNO with the flow rate determined by the randomisation. All groups will be preoxygenated for 3 minutes using 100% oxygen and closed-mouth breathing. Immediately prior to anaesthesia induction, patients will evaluate the level of discomfort of preoxygenation. Thereafter, anaesthesia is induced.

Preoxygenation will be administered to all patients until the onset of apnoea, at which point oxygen delivery via HFNO will be immediately discontinued. The patient will then undergo intubation, with apnoea maintained until their oxygen saturation drops to 93%. Once this threshold is reached, mechanical ventilation with 100% oxygen will be initiated.

Study Timeline

• Status Verified: 2024-12
• Study First Submitted: 2024-12-09
• Study First Submitted QC: 2024-12-12
• Study First Posted: 2024-12-16
• Study Start: 2025-01-13
• Last Update Submitted: 2025-01-27
• Last Update Posted: 2025-01-29
• Primary Completion: 2026-06
• Study Completion: 2026-12

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 75

Inclusion Criteria

• Adult, 18-84 years old
• ASA 1-3
• BMI < 35
• Planned for elective surgery

Exclusion Criteria

• Cardiac disease (ischemic heart disease, heart failure (NYHA ≥2), ongoing arrhythmias, pulmonary hypertension)
• Severe asthma, moderate to severe COPD
• Pregnancy
• Smokers or former smoker last finished 1 year before inclusion
• Baseline oxygen saturation < 95%
• Nasal obstruction
• Known or anticipated difficult airway
• Patients with electrical active implants where lung impedance analysis is contraindicated
• Not capable of understanding study information and signing a written consent

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Safe apnoea time	From start of apnoea after anaesthesia induction until peripheral oxygen saturation drops to 93%. This time fram will probably be between 5 and 15 minutes.	Comparison of the time from start of apnoea until reaching a SpO2 = 93% between the different flow rates

Secondary Outcome Measures

Name	Time	Method
Tolerance of 360 seconds of apnoea	From apnoea start until 5 minutes of apnoea	Comparison between the three groups of the proportion of patients tolerating 360 seconds of apnoea
Arterial oxygen levels during preoxygenation	From start of preoxygenation until end of preoxygenation (approximately 3 to 4 minutes)	Comparison between the groups in PaO2 at 1 minute and 2 minutes of preoxygenation and at the start of apnoea
Discomfort assessment	From start of preoxygenation until the end of preoxygenation, this time fram will be three minutes.	Comparision between the groups in the level of discomfort during preoxygenation. Discomfort will be assessed on a scale from 1 to 10 (0 = no discomfort, 10 = maximal discomfort)
Lung impedance changes	From start of preoxygenation until end of apnoea (approximately 5 to 15 minutes)	Lung impedance measurement will be conducted before preoxygenation (baseline) after three minutes of pre-oxygenation and at the end of apnoea. Comparisons of these values, at the different time points, will be conducted between the three groups.

Trial Locations

Locations (1)

Karolinska University Hospital; 🇸🇪 Solna, Sweden