Table 1 Characteristics of the included studies

Baillard et al. [6] 2006

Two medical-surgical ICUs of 2 university hospitals in France

N = 53

Inclusion criteria:

Acute respiratory failure requiring intubation

Hypoxemia (PaO₂ < 100 mmHg with 10 L/min O₂ mask

Exclusion criteria: encephalopathy or coma, cardiac resuscitation, hyperkalemia (> 5.5 mEq/L)

3-min preoxygenation with a nonrebreather bag-valve mask driven by 15 L/min O₂

Patient allowed to breathe spontaneously with occasional assistance

3-min preoxygenation with NIV (PSV delivered by an ICU ventilator through a face mask adjusted to obtain an expired tidal volume of 7–10 ml/kg, FiO₂ 100%, PEEP 5 cmH₂O)

PaO₂:

COT, 68 [60–79]

NIV, 60 [57–89]

Drop in SpO₂ during endotracheal intubation

Regurgitation, new infiltrate on post-procedural chest X-ray, SpO₂ < 80% during intubation, ICU mortality

Vourc’h et al. [3] 2015

Six French ICUs (3 medical, 2 medical-surgical, one surgical)

N = 119

Inclusion criteria:

Adults (≥ 18 years) with acute hypoxemic respiratory failure (RR > 30 bpm and FiO₂ ≥ 50% to obtain > 90% oxygen saturation, and estimated PaO₂/FiO₂ < 300 mmHg) requiring endotracheal intubation in ICU after RSI

Exclusion criteria: cardiac arrest, asphyxia, intubation without RSI, Cormack-Lehane grade 4 glottis

4-min preoxygenation with high FiO₂ facial mask (15 L/min O₂ flow)

4-min preoxygenation with HFNC set to 60 L/min, of humidified oxygen flow (FiO₂ 100%); maintained in place throughout the endotracheal intubation

PaO₂/ FiO₂:

Facial mask, 115.7 ± 63

HFNC, 120.2 ± 55.7

Lowest SpO₂ during endotracheal intubation

Incidence of desaturation SpO₂ < 80%, cardiovascular collapse (SBP < 80 or vasopressor introduction or increasing doses more than 30%), aspiration, 28-day mortality

Jaber et al. [20] 2016

Single-center medical and surgical ICU in France

N = 49

Inclusion criteria: Patients with severe hypoxemic acute respiratory failure (RR > 30 bpm, FiO₂ requirement ≥ 50% to obtain > 90% SpO2 or an impossibility to obtain > 90% SpO₂, estimated PaO₂/FIO₂ < 300 mmHg) admitted to ICU requiring mechanical ventilation

Exclusion criteria: cardiocirculatory arrest

4-min 30° head-up inclination with HFNC (humidified O₂ flow 60 L/min, FiO₂ 100%) combined with NIV (PS 10 cmH₂O, PEEP 5 cmH₂O, FiO₂ 100%)

4-min 30° head-up inclination with NIV (PS 10 cmH₂O, PEEP 5 cmH₂O, FiO₂ 100%)

PaO₂/ FiO₂:

HFNC + NIV, 107 [74–264]

NIV, 140 [83–201]

Minimal SpO₂ during intubation, severe hypoxemia SpO₂ < 80%, cardiovascular collapse (SBP < 65 mmHg at least once or < 90 mmHg lasting 30 min despite 500–1000 ml crystalloid loading or requiring introduction or increasing doses by more than 30% of vasoactive support), cardiac arrest, 28-day mortality

Simon et al. [4] 2016

Single center in Germany

N = 40

Inclusion criteria:

Respiratory failure with hypoxemia (PaO₂/FiO₂ < 300 mmHg), indicated for endotracheal intubation, age ≥ 18 years

Exclusion criteria

Difficult airway, nasopharyngeal obstruction or blockage

3-min preoxygenation using a BVM (adult size AMBU SPUR II disposable resuscitator with oxygen bag reservoir and without PEEP valve or pressure manometer), O₂ 10 L/min. No manual insufflation performed during apneic period.

3-min preoxygenation using HFNC, oxygen flow 50 L/min, FiO2 1.0; left in place during the intubation procedure

PaO₂/ FiO₂:

BVM, 205 ± 59

HFNC, 200 ± 57

Lowest SpO₂ during intubation, adverse events (cardiac arrest, arrhythmia, hemodynamic instability, aspiration of gastric contents)

Baillard et al. [7] 2018

Six sites in France

N = 201

Inclusion criteria:

Adults patients (age > 18) with acute respiratory failure requiring intubation

Exclusion criteria:

Encephalopathy or coma, cardiac resuscitation, decompensation of chronic respiratory failure

3-min preoxygenation with non-rebreathing BVM with an oxygen reservoir driven by 15 L/min O₂; patient allowed to breathe spontaneously with occasional assists

3-min preoxygenation using NIV—pressure support mode delivered by an ICU ventilator through a face mask adjusted to obtain an expired tidal volume of 6–8 ml/kg, FiO2 1.0, PEEP 5 cmH₂O

PaO₂/FiO₂:

BVM, 126 [95–207]

HFNC, 132 [80–175]

Maximal value SOFA score within 7 days after intubation, requirement for an early stop of preoxygenation and immediate intubation, arrhythmia with hemodynamic failure, regurgitation, severe O₂ desaturation SpO₂ < 80%, 28-day mortality

Guitton et al. [5]

2019

Seven French ICU (4 medical, 2 medical-surgical, 1 surgical)

N = 184

Inclusion criteria:

Adults patients (age > 18) requiring intubation in the ICU, without severe hypoxemia (PaO2/FiO2 < 200 mmHg)

Exclusion criteria:

Intubation without RSI (cardiac arrest), fiberoptic intubation, asphyxia, nasopharyngeal blockade, grade 4 glottis on Cormack-Lehane scale

4-min preoxygenation in a head-up position with BVM (disposable self-inflating resuscitator with a reservoir bag, O₂ set at 15 L/min)

4-min preoxygenation in a head-up position with HFNC (60 L/min flow of headed and humidified oxygen FiO2 1.0, large or medium nasal cannulae chosen according to patients’ nostril size)

PaO₂/ FiO₂:

BVM, 375 [276, 446]

HFNC, 318 [242, 396]

Lowest SpO2 during intubation, SpO2 < 80%, aspiration, cardiac arrest, severe hypotension (SBP < 80 mmHg or vasopressor initiation or dose increment), 28-day mortality

Frat et al. [8]

2019

Twenty-eight ICUs in France

N = 313

Inclusion criteria:

Patients (age > 18) admitted to the ICU requiring intubation, had acute hypoxemic respiratory failure (RR > 25 bpm or signs of respiratory distress, PaO₂/FiO₂ < 300 mmHg regardless of oxygenation strategy)

Exclusion criteria:

Cardiac arrest, altered consciousness (GCS < 8)

3–5-min preoxygenation at 30° with HFNC with oxygen flow 60 L/min through a heated humidifier, FiO₂ 1.0. Clinicians performed a jaw thrust to maintain a patent upper airway, and continued high-flow oxygen therapy during laryngoscopy until endotracheal tube was placed into the trachea

3–5-min preoxygenation at 30° with NIV—pressure support ventilation delivered via a face mask connected to an ICU ventilator, adjusted to obtain an expired tidal volume 6–8 ml/kg of predicted body weight with PEEP 5 cmH₂O and FiO₂ 1.0

PaO₂/FiO₂:

HFNC, 148 ± 70

NIV, 142 ± 65

Occurrence of an episode of severe hypoxemia (SpO₂ < 80% for at least 5 s), lowest SpO₂ during intubation, arterial hypotension, sustained arrhythmia, cardiac arrest, regurgitation, new infiltrate on chest radiography, 28-day mortality