High Flow Oxygen During Operative Hysteroscopy.
Condition: Endometrium; Hypertrophy, Cervix; Anesthesia; Apnea, Postanesthetic
MeSH terms: Hypertrophy
Study type: Interventional

Summary: 
      High-flow nasal cannula (HFNC) oxygen therapy represents an open circuit ventilation system
      that uses flows up to 70 L/min of 100% oxygen through the Optiflow THRIVETM device (Fisher
      and Paykel Healthcare Ltd, Auckland, New Zealand). Compared to conventional oxygen therapy
      systems, the heating and humidification of the flows facilitate tolerability by the patient,
      allow to reach higher and more stable inspiratory fractions of oxygen, produce a
      flow-dependent effect of continuous positive airway pressure and by reducing dead space, have
      the potential to increase alveolar volume and improve gas exchanges.

      The use of HFNC is increased in anesthesia as the only airways management technique during
      short-term procedures under procedural sedation or general anesthesia.

      Operative hysteroscopy is a short-term procedure (<30 minutes), usually performed in a
      day-hospital regimen, under procedural sedation. In case of apnea and/or hypoventilation, or
      for long and complex hysteroscopic procedures, the patient can be ventilated through facial
      or laryngeal masks.

      The primary objective of this prospective randomized controlled trial is to compare the rate
      of success of ventilation using the THRIVE device to laryngeal mask ventilation during
      operative hysteroscopies under procedural sedation.

      Secondary objectives will be the comparison of the percentage of complications in terms of
      inability to manage the airways, episodes of hypotension, cardiac arrhythmias, post-operative
      nausea and vomiting, degree of dyspnea and comfort of the patient in the Post-Anesthesia Care
      Unit between the two methods.
    

Detailed description: 
      High-flow nasal cannula (HFNC) oxygen therapy represents an open circuit ventilation system
      that uses flows up to 70 L/min of 100% oxygen through Optiflow THRIVETM (transnasal
      humidified rapid-insufflation ventilatory exchange) device (Fisher and Paykel Healthcare Ltd,
      Auckland, New Zealand).

      Compared to conventional low-flows oxygen therapy systems, the heating and humidification of
      the flow facilitate tolerability by the patient, ensure an efficient muco-ciliary function
      and allow to reach higher and more stable inspiratory fractions of oxygen.

      The system produces a flow-dependent effect of continuous positive airway pressure of about 1
      cmH20 for every 10L/min increase in oxygen flow and a reduction of the dead space, having the
      potential to increase the alveolar volume thus improving gas exchanges.

      The resulting reduction in respiratory rate and the improvement of thoracoabdominal synchrony
      minimize the onset of respiratory fatigue in the patient.

      Initially introduced for the treatment of acute hypoxemic respiratory failure, HFNC oxygen
      therapy is increasingly used also in anesthesia as the only airways management technique
      during short-term procedures performed under sedation (e.g. digestive endoscopy) or under
      general anesthesia (such as microlaryngoscopies).

      Compared to low-flows oxygen systems, the greater CO2 elimination capacity could reduce the
      incidence of hypoventilation and apnea episodes potentially associated with patient sedation.

      Operative hysteroscopy is a brief procedure, normally lasting <30 minutes, usually performed
      in a day-hospital regime under procedural analgo-sedation, with conventional ventilatory
      support through a face mask/laryngeal mask.

      The primary objective of this study is the comparison of the rate of success in airways
      management via the THRIVE system versus positive pressure ventilation by I-gel laryngeal mask
      during 180 hysteroscopies performed under general anesthesia.

      Secondary objectives are: the comparison of intraoperative and postoperative complications
      between the two groups.

      Materials and methods Patient monitoring throughout the procedure will include automatic
      noninvasive, intermittent (every 5 minutes) blood pressure monitoring, 3-leads
      electrocardiogram, peripheral oxygen saturation (SpO2), bispettral index (BIS),
      transcutaneous capnography with TCM5 Radiometer monitor.

      Upon arrival in the operating room, the patient will assume the lithotomic position; a
      peripheral venous cannula will be placed at the level of the hand or forearm and it will
      begin the infusion of Ringer Lactate solution 3 ml/kg/h. Omeprazole 40 mg and dexamethasone 4
      mg will be administered before the procedure as standard internal practice.

      In the THRIVE group, dedicated Optiflow THRIVETM nasal cannulas will be positioned for 100%
      high flow oxygen therapy at an initial flow of 30 L/min. After induction of anesthesia and
      throughout the procedure the flow of oxygen will be increased to 70 L/min.

      In the control group (CONTROL) after induction of anesthesia the patient will be mechanically
      ventilated through an I-Gel laryngeal mask.

      General anesthesia, as per normal clinical practice, will be induced and maintained by
      target-controlled infusion (TCI) of propofol (7 mcg/Kg) by Orchestra Infusion system
      (Fresenius Kabi) and fentanyl 1.5 mcg/kg and in both groups. Propofol infusion rate will be
      between 3-4 mcg/ml for propofol, so to maintain a level of sedation monitored via BIS between
      40-50. Paracetamol 1g, ondansetron 4 mg and ketorolac 30 mg will also be administered as per
      normal clinical practice.

      In case of desaturation episodes, defined as a SpO2< 94% or increases in tcCO2 above 65 mmHg,
      the patient will be assisted with positive pressure ventilation through a facial or laryngeal
      mask or oro-tracheal intubation based on clinical judgment of the anesthesiologist.

      At the end of the hysteroscopy the patient will be transferred to the Post-Anesthesia Care
      Unit (PACU) for 3 hours of post-procedural monitoring as required by internal protocol for
      day-surgery procedures. Standard monitoring will include non-invasive, intermittent (every 15
      minutes) blood pressure monitoring, 3-leads electrocardiogram and peripheral oxygen
      saturation (SpO2).

      One hour after the end of the procedure and before discharge from the PACU the patient will
      be asked to quantify the perceived degree of dyspnea with the Borg dyspnoea score and the
      degree of comfort using a Visual Numeric Scale (VAS) ranging from 0 to 10. In case of
      SpO2<94%, additional oxygen will be administered by means of a Venturi-type face mask with
      FiO2 40%. Discharge from the PACU will require an Aldrete score of 9-10.

      Statistics The data will be analyzed according to an intention-to-treat principle. Clinical
      and demographic characteristics of the sample will be described through descriptive
      statistical techniques. Continuous quantitative variables with normal distribution will be
      reported as mean and standard deviation; as median and interquartile range the non-normal
      variables.

      Categorical variables and missing data will be presented as absolute values and percentage, n
      (%).

      Continuous variables will be compared with the Student t-test in case of normal distribution
      or, if not, with the Mann-Whitney test for independent samples. The normality of the
      distribution of the variables will be verified graphically by histograms and with the
      Shapiro-Wilk test.

      Continuous variables with repeated measurements will be compared with a mixed-effect linear
      regression model. The type of airway management used and the timing at which the measurements
      will be performed will be considered as fixed effects; a random effect related to the patient
      will also be added.

      The assumption of normality of the residues of the model will be graphically verified by
      histograms and Q-Q plots. The P-values will be obtained with the likelihood ratio test of the
      complete model with the effect in question with respect to the model without the effect. The
      estimates of the predictors used in the model will be reported with the relative 95%
      confidence intervals and P-values obtained with the Wald test.

      In case of failure of the technique, defined as a transcutaneous concentration of carbon
      dioxide (tcCO2) > 60 mmHg and/or SpO2 < 94% in any of the study groups, a time-to-event
      (Kaplan-Meier) analysis will be carried out that takes into account the different duration of
      the procedures and therefore the different risk ranges for the possible onset of hypercapnia
      and / hypoxemia.

      Differences between categorical data will be reported in terms of relative risk or risk
      differences, 95% confidence intervals and p-values based on the Χ2 test or fisher's exact
      test.

      The significance level will be set for α < 0.05. All analyses will be performed with the
      statistical software R version 4.1.2 (R Foundation for Statistical Computing, Austria).

      Continuous variables with repeated measurements will be compared with a mixed-effect linear
      regression model. Normality of distribution will be verified with the Shapiro-Wilk test.
      Continuous variables will be compared with Student t - or Mann Whitney test; categorical
      variables with the Chi-square test.

      Sample size calculation In 2021, Kim et al. compared the safety of high flow oxygen therapy
      to conventional low-flow oxygen support for gastrointestinal endoscopic procedures performed
      under sedation reporting minimum values of peripheral saturation detected by pulse-oximeter
      higher in the high-flow group (99.8%) compared to low-flow oxygen therapy (95.1%).

      To our knowledge, no study has compared these two methods during operative hysteroscopies
      under procedural sedation.

      Based on literature and on the results from an internal registered pilot study in which we
      investigated the success rate of THRIVE as unique airway management technique in this
      setting, assuming a similar success rate of 95% for THRIVE and laryngeal mask ventilation,
      for a unilateral confidence interval of 95% and a 90% test power, we estimated a minimum
      sample of 82 patients per group to test a non-inferiority limit of 10%. The sample was
      increased to 90 patients for group to take into account any dropouts.
    

Intervention name(s): Transnasal humidified rapid-insufflation ventilatory exchange (THRIVE).; LMA
Intervention type(s): Device; Device
Intervention description(s): In the THRIVE group, dedicated Optiflow THRIVE nasal cannulas will be positioned for 100% high flow oxygen therapy at an initial flow of 30 L/min. After induction of anesthesia and throughout the procedure the flow of oxygen will be increased to 70 L/min.; Mechanical ventilation performed by a laringeal mask
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: High flow nasal cannula Oxygen; Procedural sedation; Apnoeic ventilation; Operative hysteroscopy; THRIVE