Comparison of Different Oxygen Flow Rates During Preoxygenation Using High-Flow Nasal Oxygen (PREFLOW2)
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.
Study Overview
Status
Intervention / Treatment
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 Type
Enrollment (Estimated)
Phase
- Not Applicable
Contacts and Locations
Study Locations
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-
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Solna, Sweden, 17176
- Karolinska University Hospital
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-
Participation Criteria
Eligibility Criteria
Ages Eligible for Study
- Adult
- Older Adult
Accepts Healthy Volunteers
Description
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 Plan
How is the study designed?
Design Details
- Primary Purpose: Treatment
- Allocation: Randomized
- Interventional Model: Parallel Assignment
- Masking: Double
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Active Comparator: High-flow nasal oxygen, flow rate 45 l/min
Preoxygenation using high-flow nasal oxygen with a flow rate of 45 l/min
|
In this study, we will use high-flow nasal oxygen for preoxygenation in patients undergoing elective anaesthesia.
Preoxygenation with high-flow nasal oxygen is most often performed at flow rates of <50 l/min.
In this study, patients will be randomised to preoxygenation using high-flow nasal oxygen and flow rates of 45 l/min, 70 l/min or 95 /min.
|
|
Experimental: High-flow nasal oxygen, flow rate 70 l/min
Preoxygenation using high-flow nasal oxygen with a flow rate of 70 l/min
|
In this study, we will use high-flow nasal oxygen for preoxygenation in patients undergoing elective anaesthesia.
Preoxygenation with high-flow nasal oxygen is most often performed at flow rates of <50 l/min.
In this study, patients will be randomised to preoxygenation using high-flow nasal oxygen and flow rates of 45 l/min, 70 l/min or 95 /min.
|
|
Experimental: High-flow nasal oxygen, flow rate 95 l/min
Preoxygenation using high-flow nasal oxygen with a flow rate of 95 l/min
|
In this study, we will use high-flow nasal oxygen for preoxygenation in patients undergoing elective anaesthesia.
Preoxygenation with high-flow nasal oxygen is most often performed at flow rates of <50 l/min.
In this study, patients will be randomised to preoxygenation using high-flow nasal oxygen and flow rates of 45 l/min, 70 l/min or 95 /min.
|
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Safe apnoea time
Time Frame: 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
|
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.
|
Secondary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Tolerance of 360 seconds of apnoea
Time Frame: From apnoea start until 5 minutes of apnoea
|
Comparison between the three groups of the proportion of patients tolerating 360 seconds of apnoea
|
From apnoea start until 5 minutes of apnoea
|
|
Arterial oxygen levels during preoxygenation
Time Frame: 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
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From start of preoxygenation until end of preoxygenation (approximately 3 to 4 minutes)
|
|
Lung impedance changes
Time Frame: 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.
|
From start of preoxygenation until end of apnoea (approximately 5 to 15 minutes)
|
|
Discomfort assessment
Time Frame: 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)
|
From start of preoxygenation until the end of preoxygenation, this time fram will be three minutes.
|
Other Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Differences in end-tidal and arterial carbon dioxide levels
Time Frame: From start of apnoea until end of apnoea (approximately 5 to 10 minutes)
|
Exploratory outcome.
Describe the differences in end-tidal and arterial carbon dioxide levels immediately following termination of apnoea.
|
From start of apnoea until end of apnoea (approximately 5 to 10 minutes)
|
|
Rate of arterial carbon dioxide increase during apnoea
Time Frame: From start of apnoea until end of apnoea (approximately 5 to 10 minutes)
|
Exploratory outcome.
We will investigate the rate of increase in arterial carbon dioxide levels during the apnoeic period.
|
From start of apnoea until end of apnoea (approximately 5 to 10 minutes)
|
Collaborators and Investigators
Sponsor
Collaborators
Study record dates
Study Major Dates
Study Start (Actual)
Primary Completion (Estimated)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Other Study ID Numbers
- DNR: 2024-04565-01
- SLS-1000363 & SLS-999871 (Other Grant/Funding Number: Läkaresällskapet)
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
IPD Plan Description
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
product manufactured in and exported from the U.S.
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