Optiniv Method

[Natalí Stibb]

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Purpose: High-flow nasal cannula oxygen (HFNC) has the potential to provide apnoeic oxygenation. We decided to assess in a proof-of-concept study whether the addition of HFNC to non-invasive ventilation (NIV) could reduce oxygen desaturation during intubation, compared with NIV alone for preoxygenation, in severely hypoxaemic intensive care unit (ICU) patients with respiratory failure.

Methods: We conducted a randomised, controlled, single-centre trial with assessor-blinded outcome assessment in patients admitted to the ICU. Hypoxaemic patients requiring orotracheal intubation for respiratory failure were randomised to receive preoxygenation using HFNC [flow = 60 L/min, fraction of inspired oxygen (FiO2) = 100 %] combined with NIV (pressure support = 10 cmH2O, positive end-expiratory pressure = 5 cmH2O, FiO2 = 100 %) in the intervention group or NIV alone in the reference group prior to intubation. The primary outcome was the lowest oxygen saturation (SpO2) during the intubation procedure. Secondary outcomes were intubation-related complications and ICU mortality.

Results: Between July 2015 and February 2016, we randomly assigned 25 and 24 patients to the intervention and reference groups, respectively. In both groups the main reasons for respiratory failure were pneumonia and ARDS. During the intubation procedure, the lowest SpO2 values were significantly higher in the intervention group than in the reference group [100 (95-100) % vs. 96 (92-99) %, p = 0.029]. After exclusion of two patients from analysis for protocol violation, no (0 %) patients in the intervention group and five (21 %) patients in the reference group had SpO2 below 80 % (p = 0.050). We recorded no significant difference between the groups in intubation-related complications or ICU mortality.

Conclusions: A novel strategy for preoxygenation in hypoxaemic patients, adding HFNC for apnoeic oxygenation to NIV prior to orotracheal intubation, may be more effective in reducing the severity of oxygen desaturation than the reference method using NIV alone.

High-flow nasal cannula oxygen (HFNC) has the potential to provide apnoeic oxygenation. We decided to assess in a proof-of-concept study whether the addition of HFNC to non-invasive ventilation (NIV) could reduce oxygen desaturation during intubation, compared with NIV alone for preoxygenation, in severely hypoxaemic intensive care unit (ICU) patients with respiratory failure.

We conducted a randomised, controlled, single-centre trial with assessor-blinded outcome assessment in patients admitted to the ICU. Hypoxaemic patients requiring orotracheal intubation for respiratory failure were randomised to receive preoxygenation using HFNC [flow = 60 L/min, fraction of inspired oxygen (FiO2) = 100 %] combined with NIV (pressure support = 10 cmH2O, positive end-expiratory pressure = 5 cmH2O, FiO2 = 100 %) in the intervention group or NIV alone in the reference group prior to intubation. The primary outcome was the lowest oxygen saturation (SpO2) during the intubation procedure. Secondary outcomes were intubation-related complications and ICU mortality.

A novel strategy for preoxygenation in hypoxaemic patients, adding HFNC for apnoeic oxygenation to NIV prior to orotracheal intubation, may be more effective in reducing the severity of oxygen desaturation than the reference method using NIV alone.

Non-invasive ventilation (NIV) for preoxygenation of patients with severe hypoxaemic acute respiratory failure is associated with less hypoxaemia than preoxygenation with oxygen facial mask during intubation procedures [11]. Indeed, combining pressure-support (PS) with positive end-expiratory pressure (PEEP) limits alveolar collapse and atelectasis formation [12, 13], responsible for hypoventilation and low perfusion ventilation ratio [14]. Incidence of severe hypoxaemia defined by a peripheral capillary oxygen saturation (SpO2) of less than 80 % can be reduced by applying NIV preoxygenation, a method which is now used by 36 % of teams [10] for preoxygenation of patients with severe hypoxaemic acute respiratory failure.

However, although NIV can be safely applied for preoxygenation before the intubation procedure, NIV facial mask has to be taken off after preoxygenation in order to allow the passage of the orotracheal tube through the mouth. Furthermore, positioning the orotracheal tube into the trachea may take time, from a few seconds to several minutes in case of difficult intubation [10]. The hypoxaemic patient does not receive oxygen during this period, which contributes to the risk of severe hypoxaemia during intubation procedures [15, 16].

Using HFNC combined with NIV may have potential advantages over conventional NIV alone for preoxygenation before intubation procedures in hypoxaemic ICU patients. Some studies have assessed the preoxygenation effect of HFNC compared to oxygen facial mask or other devices, with conflicting results [19, 23, 24]. However, the technique of preoxygenation combining NIV and HFNC, respectively incorporating the concepts of prevention of alveolar derecruitment and of apnoeic oxygenation, has never been assessed and benefit remains to be established.

We aimed to assess in the OPTINIV study if preoxygenation combining HFNC and NIV compared to NIV alone could prevent desaturation during the intubation procedure and complications related to intubation in ICU severe hypoxaemic patients needing mechanical ventilation for hypoxaemic acute respiratory failure.

We hypothesized that in comparison to the reference preoxygenation method using NIV alone, a novel strategy of preoxygenation which combines HFNC with NIV would allow for a reduction of severe hypoxaemia during the intubation procedure in severe hypoxaemic respiratory failure patients.

The HFNC (Optiflow, Fisher & Paykel Healthcare, Auckland, NZ) combined with NIV for decreasing oxygen desaturation during intubation procedures in ICU hypoxaemic patients (OPTINIV) trial was an investigator-initiated, single-centre, randomised, controlled, two-arm trial. The OPTINIV proof-of-concept study took place in a mixed medical and surgical 16-bed ICU, in France. The OPTINIV protocol was previously published [25]. The Institutional Review Board of the University Hospital of Montpellier (France) approved the trial. On 13 May 2015, the study was approved by a central ethics committee (Comit de Protection des Personnes Sud-Mditerrane IV, Montpellier, France) with the registration number IDRCB 2015-A00708-41. The OPTINIV study was conducted in accordance with the Declaration of Helsinki and was registered at with trial identification number NCT02530957. Study design is detailed in the Supplementary Fig. 1.

Three methods of consent were used, as required by the institutional review board in accordance with the 2013 Declaration of Helsinki. If possible, the patient was included after written informed consent. However, the patient often cannot understand information given because of severe hypoxaemia. These patients were included after written informed consent was provided by next of kin or an emergency procedure (investigator signature) if next of kin was not present. When available, after recovery, patients were retrospectively asked for written consent to continue the trial.

Patients admitted to the ICU and requiring mechanical ventilation through an orotracheal tube were eligible in the study. Severe hypoxaemic acute respiratory failure was defined as a respiratory rate higher than 30 per minute, and a FiO2 requirement of 50 % or more [22] to obtain at least 90 % SpO2 (or an impossibility to obtain more than 90 % SpO2) and an estimated partial pressure of arterial oxygen (PaO2)/FiO2 ratio below 300 mmHg, in the 4 h before inclusion [23].

Patients fulfilling one or more of the following criteria were not included: age less than 18 years, pregnant or breastfeeding woman, protected person, intubation procedures in case of cardiocirculatory arrest, nasopharyngeal obstruction contraindicating the use of HFNC, and usual contraindications to NIV [26].

Blinding sequence of the OPTINIV trial. HFNC high-flow nasal cannula oxygen therapy, FiO 2 fraction of inspired oxygen, NIV non-invasive ventilation, PS pressure support, PEEP positive end-expiratory pressure. To allow blinding, a nasal cannula was positioned in each group. The operator performing the intubation blinded the group by placing a large sheet over the oxygen flow meter. Both groups received NIV. a In the interventional group (real HFNC + NIV), the nasal cannula was connected to the oxygen flow meter via a tube and oxygen set at 60 L/min and 100 % of FiO2 which was delivered to the patient. The interventional group consisted in applying a preoxygenation at 30 of head-up inclination with NIV (PS of 10 cmH2O, PEEP of 5 cm H2O, FiO2 = 100 %) and oxygen HFNC set at 60 L/min and 100 % of FiO2. b In the reference group (sham HFNC + NIV), no oxygen flow was administered by the nasal cannula to the patient. The tube connected to the nasal cannula positioned on the patient was hidden under the sheet, without connection to the oxygen flow meter. To mimic the noise of HFNC in the reference group, another nasal cannula was hidden under the sheet and connected to the oxygen flow meter, with a flow also set at 60 L/min. The reference group consisted in applying a preoxygenation at 30 of head-up inclination with NIV only (PS of 10 cmH2O, PEEP of 5 cmH2O, FiO2 = 100 %) without oxygen HFNC (nasal cannula positioned without any flow)

The reference group received 4 min preoxygenation at 30 of head-up inclination with NIV only (same parameters as in the interventional group) without HFNC (nasal cannula positioned without any flow, Fig. 1).

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