Pleth variability index during preoxygenation could predict anesthesia-induced hypotension: A prospective, observational study

STUDY OBJECTIVE

To determine whether changes in the pleth variability index (PVi) during preoxygenation with forced ventilation for 1 min could predict anesthesia-induced hypotension.

DESIGN

Prospective, observational study.

SETTING

A tertiary teaching hospital.

PATIENTS

Ninety-six patients who underwent general anesthesia using total intravenous anesthesia were enrolled.

INTERVENTIONS

Upon the patient's arrival at the preoperative waiting area, a PVi sensor was affixed to their fourth fingertip. For preoxygenation, forced ventilation of 8 breaths/min in a 1:2 inspiratory-expiratory ratio was conducted using the guidance of an audio file. One minute after preoxygenation, anesthetic administration was initiated. Blood pressure was measured for the next 15 min.

MEASUREMENTS

We calculated the difference (dPVi) and percentage of change (%PVi) between the PVi values immediately before and after forced ventilation. Anesthesia-induced hypotension was defined as a mean arterial pressure of <60 mmHg within 15 min after the infusion of anesthetics.

MAIN RESULTS

Overall, 87 patients were included in the final analysis. Anesthesia-induced hypotension occurred in 31 (35.6%) of the 87 patients. Receiver operating characteristic curve analyses identified a cut-off value of -2 for dPVi, with an area under the curve of 0.691 (95% confidence interval [CI], 0.564-0.818; P < 0.001) and a cut-off value of -7.6% for %PVi, with an area under the curve of 0.711 (95% CI, 0.589-0.832; P < 0.001). Further, multivariate logistic regression analysis showed that a low %PVi with an odds ratio of 9.856 (95% CI, 3.131-31.032; P < 0.001) was a significant determinant of anesthesia-induced hypotension.

CONCLUSIONS

Hypotension frequently occurs during general anesthesia induction and can impact outcomes. Additionally, the percentage change in the PVi before and after preoxygenation using deep breathing can be used to predict anesthesia-induced hypotension.

Effect of reverse Trendelenburg position and positive pressure ventilation on safe non-hypoxic apnea period in obese, a randomized-control trial

PURPOSE

There is an elevated incidence of hypoxemia during the airway management of the morbidly obese. We aimed to assess whether optimizing body position and ventilation during pre-oxygenation allow a longer safe non-hypoxic apnea period (SNHAP).

METHODS

Fifty morbidly obese patients were recruited and randomized for this study. Patients were positioned and preoxygenated for three minutes in the ramp position associated with spontaneous breathing without additional CPAP or PEEP (RP/ZEEP group) or in the reverse Trendelenburg position associated with pressure support ventilation mode with pressure support of 8 cmH2O and an additional 10 cmH2O of PEEP while breathing spontaneously (RT/PPV group) according to randomization.

RESULTS

The SNHAP was significantly longer in the RT/PPV group (258.2 (55.1) vs. 216.7 (42.3) seconds, p = 0.005). The RT/PPV group was also associated to a shorter time to obtain a fractional end-tidal oxygen concentration (FEtO2) of 0.90 (85.1(47.8) vs 145.3(40.8) seconds, p < 0.0001), a higher proportion of patients that reached the satisfactory FEtO2 of 0.90 (21/24, 88% vs. 13/24, 54%, p = 0.024), a higher FEtO2 during preoxygenation (0.91(0.05) vs. 0.89(0.01), p = 0.003) and a faster return to 97% oxygen saturation after ventilation resumption (69.8 (24.2) vs. 91.4 (39.2) seconds, p = 0.038).

CONCLUSION

In the morbidly obese population, RT/PPV, compared to RP/ZEEP, lengthens the SNHAP, decreases the time to obtain optimal preoxygenation conditions, and allows a faster resuming of secure oxygen saturation. The former combination allows a more significant margin of time for endotracheal intubation and minimizes the risk of hypoxemia in this highly vulnerable population.

TRIAL REGISTRATION

NCT02590406, 29/10/2015.

Efficacy of preoxygenation administration in volunteers, in extending the end-expiration breath-hold duration for application to abdominal radiotherapy

Background and purpose

End expiration breath hold (EEBH) is the preferred motion management method for abdominal Stereotactic Ablative Body Radiotherapy (SABR) treatments. However, multiple short EEBHs are required to complete a single treatment session. The study aimed to determine the efficacy of preoxygenation with hyperventilation in extending an EEBH duration.

Materials and methods

We randomised 10 healthy participants into two arms, each included breathing room air and oxygen at a rate of 10 L per minute (l/min) without hyperventilation for four minutes, and normally for four minutes and with hyperventilation for one minute at a rate of 20 breaths/minute for hyperventilation. The type of gas was blinded from the participants for each test. EEBH durations were then recorded, as well as systolic blood pressure, SpO₂ and heart rate. A discomfort rating was also recorded after each breath hold.

Results

A significant increase in duration of almost 50% was observed between normal breathing of room air and breathing oxygen normally followed by hyperventilation. Vital signs remained consistent between the 4 tests. The tests were well tolerated with 75% of participants recording none or minimal discomfort.

Conclusion

Preoxygenation with hyperventilation could be used to increase the EEBH duration for abdominal SABR patients which would assist in the accuracy of these treatments and possibly resulting in a reduction of overall treatment times.

High-flow oxygen therapy versus facemask preoxygenation in anticipated difficult airway management (PREOPTI-DAM): an open-label, single-centre, randomised controlled phase 3 trial

Background

Difficult airway management remains a critical procedure with life-threatening adverse events. Current guidelines suggest high-flow therapy by nasal cannulae (HFNC) as a preoxygenation device in this setting. However, there is an evidence gap to support this recommendation.

Methods

The PREOPTI-DAM study is an open-label, single-centre, randomised controlled phase 3 trial done at Nantes University Hospital, France. Patients were aged 18-90 years with one major or two minor criteria of anticipated difficult airway management, and requiring intubation for scheduled surgery, were eligible. Patients with body mass index >35 kg/m² were excluded. Patients were randomly allocated (1:1) to receive 4-min preoxygenation by HFNC or facemask. Randomisation was stratified according to the intubation strategy (laryngoscopic versus fiberoptic intubation). The primary outcome was the incidence of oxygen desaturation ≤94% or of bag-mask ventilation during intubation. The primary and safety analyses included the intention to treat population. This trial is registered with ClinicalTrials.gov (NCT03604120) and EudraCT (2018-A00434-51).

Findings

From September 4 2018 to March 31 2021, 186 patients were enrolled and randomly assigned. One participant withdrew consent and 185 (99.5%) were included in the primary analysis (HFNC, N = 95; Facemask, N = 90). The incidence of the primary outcome was not significantly different between the HFNC and the facemask groups, respectively 2 (2%) versus 7 (8%); adjusted difference, -5.6 [95% confidence interval (CI), -11.8 to 0.6], P = 0.10. In the HFNC group, 76 patients (80%) versus 53 (59%) in the facemask group, reported good or excellent intubation experiences; adjusted difference 20.5 [95% CI, 8.3-32.8], P = 0.016. Comparing HFNC with facemask, severe complication occurred in 22 (23%) versus 27 (30%) patients (P = 0.29), and moderate complication in 14 (15%) versus 18 (20%) patients (P = 0.35). No death or cardiac arrest occurred during the study.

Interpretation

Compared with facemask, HFNC did not significantly reduce the incidence of desaturation ≤94% or bag-mask ventilation during anticipated difficult intubation but the trial was underpowered to rule out a clinically significant benefit. Patient satisfaction was improved with HFNC.

Funding

Nantes University Hospital and Fisher & Paykel Healthcare.

Comparison of preoxygenation efficiency measured by the oxygen reserve index between high-flow nasal oxygenation and facemask ventilation: a randomised controlled trial

BACKGROUND

High-flow nasal oxygenation and the oxygen reserve index (ORI), which is a non-invasive and innovative modality that reflects the arterial oxygen content, are used in general anaesthesia. This study compares the preoxygenation efficiency (measured by the ORI) of high-flow nasal oxygenation and facemask ventilation during the induction process.

METHODS

This single-centre, two-group, randomised controlled trial included 197 patients aged ≥ 20 years who underwent orotracheal intubation for general anaesthesia for elective surgery. The patients were randomly allocated to receive preoxygenation via facemask ventilation or high-flow nasal oxygenation. The ORI was measured and compared between both groups.

RESULTS

The ORI increased during preoxygenation in all patients. At 1 min of preoxygenation, the ORI was significantly higher in the high-flow nasal oxygenation group (0.34 ± 0.33) than in the facemask ventilation group (0.21 ± 0.28; P = 0.003). The highest ORI was not significantly different between the two groups (0.68 ± 0.25 in the high-flow nasal oxygenation group vs. 0.70 ± 0.28 in the facemask ventilation group; P = 0.505).

CONCLUSIONS

High-flow nasal oxygenation results in an oxygenation status similar to that provided by facemask ventilation during the induction process of general anaesthesia; therefore, high-flow nasal oxygenation is a feasible preoxygenation method.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT04291339).

Preoxygenation with standard facemask combining apnoeic oxygenation using high flow nasal cannula versuss standard facemask alone in patients with and without obesity: the OPTIMASK international study

BACKGROUND

Combining oxygen facemask with apnoeic oxygenation using high-flow-nasal-oxygen (HFNO) for preoxygenation in the operating room has not been studied against standard oxygen facemask alone. We hypothesized that facemask-alone would be associated with lower levels of lowest end-tidal oxygen (EtO2) within 2 min after intubation in comparison with facemask combined with HFNO.

METHODS

In an international prospective before-after multicentre study, we included adult patients intubated in the operating room from September 2022 to December 2022. In the before period, preoxygenation was performed with facemask-alone, which was removed during laryngoscopy. In the after period, facemask combined with HFNO was used for preoxygenation and HFNO for apnoeic oxygenation during laryngoscopy. HFNO was maintained throughout intubation. The primary outcome was the lowest EtO2 within 2 min after intubation. The secondary outcome was SpO2 ≤ 95% within 2 min after intubation. Subgroup analyses were performed in patients without and with obesity. This study was registered 10 August 2022 with ClinicalTrials.gov, number NCT05495841.

RESULTS

A total of 450 intubations were evaluated, 233 with facemask-alone and 217 with facemask combined with HFNO. In all patients, the lowest EtO2 within 2 min after intubation was significantly lower with facemask-alone than with facemask combined with HFNO, 89 (85-92)% vs 91 (88-93)%, respectively (mean difference - 2.20(- 3.21 to - 1.18), p < 0.001). In patients with obesity, similar results were found [87(82-91)% vs 90(88-92)%, p = 0.004]; as in patients without obesity [90(86-92)% vs 91(89-93)%, p = 0.001)]. SpO2 ≤ 95% was more frequent with facemask-alone (14/232, 6%) than with facemask combined with HFNO (2/215, 1%, p = 0.004). No severe adverse events were recorded.

CONCLUSIONS

Combining facemask with HFNO for preoxygenation and apnoeic oxygenation was associated with increased levels of lowest EtO2 within 2 min after intubation and less desaturation.

Effectiveness of preoxygenation by conventional face mask versus non-invasive ventilation in morbidly obese patients: measurable by the oxygen-reserve index?

Preoxygenation is a crucial manoeuvre for patients' safety, particularly for morbidly obese patients due to their reduced pulmonary reserve and increased risk for difficult airway situations. The oxygen reserve index (ORI™) was recently introduced as a new parameter of multiple wavelength pulse oximetry and has been advocated to allow assessment of hyperoxia [quantified by the resulting arterial oxygen partial pressure (PaO₂)]. This study investigates if ORI can be used to evaluate the impact of two different preoxygenation manoeuvres on the grade of hyperoxia. Two preoxygenation manoeuvres were sequentially evaluated in 41 morbidly obese patients: First, breathing 100% oxygen for 5 min via standard face mask. Second, after achieving a second baseline, 5 min of non-invasive ventilation (NIV) with 100% oxygen. The effect of preoxygenation on ORI compared to PaO₂ was evaluated and whether differences in the two preoxygenation manoeuvres can be monitored by ORI. Overall correlation of PaO₂ and ORI was significant (Spearman-Rho coefficient of correlation 0.818, p < 0.001). However, ORI could not differentiate between the two preoxygenation manoeuvres although the PaO₂ values for NIV preoxygenation were significantly higher compared to standard preoxygenation (median 505 mmHg (M1) vs. 550 mmHg (M3); p < 0.0001). In contrast, ORI values did not differ significantly (median 0.39 (M1) vs. 0.38 (M3); p = 0.758). Absolute values of ORI cannot be used to assess effectiveness of a preoxygenation procedure in bariatric patients, mainly because its range of discrimination is considerably lower than the high ranges of PaO₂ attained by adequate preoxygenation. Trial registration German Clinical Trials Register: DRKS00025023 (retrospectively registered on April 16th, 2021).

Non-invasive ventilation for preoxygenation before general anesthesia: a systematic review and meta-analysis of randomized controlled trials

Background and objectives

Preoxygenation is crucial for providing sufficient oxygen reservoir to a patient before intubation and enables the extension of the period between breathing termination and critical desaturation (safe apnoea time). Conventionally, face mask ventilation is used for preoxygenation. Non-invasive ventilation is a new preoxygenation method. The study objective was to compare the outcomes of non-invasive ventilation and face mask ventilation for preoxygenation.

Method

PubMed, Embase, Cochrane Library, and the ClinicalTrials.gov registry were searched for eligible studies published from database inception to September 2021. Individual effect sizes were standardized, and a meta-analysis was conducted using random effects models to calculate the pooled effect size. Inclusion criteria were randomised controlled trials of comparing the outcomes of non-invasive ventilation or face mask ventilation for preoxygenation in patients scheduled for surgeries. The primary outcome was safe apnea time, and the secondary outcomes were post-operative complications, number of patients who achieved the expired O₂ fraction (FeO₂) after 3 min of preoxygenation, minimal SpO₂ during tracheal intubation, partial pressure of oxygen in the arterial blood (PaO₂) and partial pressure of carbon dioxide (PaCO₂) after preoxygenation, and PaO₂ and PaCO₂ after tracheal intubation.

Results

13 trials were eligible for inclusion in this study. Significant differences were observed in safe apnoea time, number of patients who achieved FeO₂ 90% after preoxygenation for 3 min, and PaO₂ and PaCO₂ after preoxygenation and tracheal intubation. Only in the non-obese subgroup, no significant difference was observed in safe apnoea time (mean difference: 125.38, 95% confidence interval: − 12.26 to 263.03).

Conclusion

Non-invasive ventilation appeared to be more effective than conventional methods for preoxygenation. We recommend non-invasive ventilation based on our results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01842-y.

Preoxygenation: from hardcore physiology to the operating room

If we define the human body by the mass of the elements that compose it, we could say that we are oxygen and other elements. Oxygen, in addition to being fundamental in our composition, is an element that we constantly need to support cellular respiration and, therefore, life. Interestingly, despite its importance, humans have not developed mechanisms that allow us to store it and, therefore, we are unable to sustain life if we are deprived of ventilation, even for brief periods. Accordingly, the ability to induce the cessation of ventilation in a patient must be accompanied by different technical and non-technical skills that allow the patient's safety to be maintained in this highly vulnerable state. Through the use of basic mathematical tools and comparative physiology, we hereby propose to review the physiological foundations of preoxygenation to understand the reasons behind the clinical recommendations in this field.

Fraction of Expired Oxygen as a Measure of Preoxygenation Prior to Rapid Sequence Intubation in the Pediatric Emergency Department

BACKGROUND

Pulse oximetry (SpO₂) is a flawed measure of adequacy of preoxygenation prior to intubation. The fraction of expired oxygen (FeO₂) is a promising but understudied alternative.

OBJECTIVE

To investigate FeO₂ as a measure of preoxygenation prior to intubation in a pediatric emergency department.

METHODS

We conducted a prospective, observational study of patients 18 and younger. We collected data using video review, and FeO₂ was measured via inline sampling. The main outcomes were FeO₂ and SpO₂ at the start of preoxygenation, end of preoxygenation/start of intubation attempt, and the end of intubation attempt. We compared FeO₂ and SpO₂ at the end of preoxygenation for patients with and without oxyhemoglobin desaturation.

RESULTS

We enrolled 85 of 88 eligible patients during the 14-month study period. FeO₂ data were available at the start of preoxygenation for 53 of 85 patients (62%), and for the end of preoxygenation for 59 of 85 patients (69%). Median FeO₂ at the start and end of preoxygenation was 90% (interquartile range [IQR] 88, 92) and 90% (IQR 88, 92). Median SpO₂ at the start and end of preoxygenation was 100% (IQR 100, 100). There were 11 episodes of desaturation, with median FeO₂ at the start of intubation attempt of 89.5 (IQR 54.5, 91.5) and median SpO₂ of 100 (IQR 99, 100). Patients who did not have a desaturation event had a median FeO₂ of 90.0 (IQR 88.0, 92.0).

CONCLUSIONS

Measuring FeO₂ during rapid sequence intubation is challenging with feasibility limitations, but may be a more discriminatory metric of adequate preoxygenation.

Comparison of the effectiveness of high-flow nasal oxygen vs. standard facemask oxygenation for pre- and apneic oxygenation during anesthesia induction: a systematic review and meta-analysis

BACKGROUND

In recent years, high flow nasal oxygen (HFNO) has been widely used in clinic, especially in perioperative period. Many studies have discussed the role of HFNO in pre- and apneic oxygenation, but their results are controversial. Our study aimed to examine the effectiveness of HFNO in pre- and apneic oxygenation by a meta-analysis of RCTs.

METHODS

EMBASE, PUBMED, and COCHRANE LIBRARY databases were searched from inception to July 2021 for relevant randomized controlled trails (RCTs) on the effectiveness of HFNO versus standard facemask ventilation (FMV) in pre- and apenic oxygenation. Studies involving one of the following six indicators: (1) Arterial oxygen partial pressure (PaO2), (2) End expiratory oxygen concentration (EtO2), (3) Safe apnoea time, (4) Minimum pulse oxygen saturation (SpO2min), (5) Oxygenation (O2) desaturation, (6) End expiratory carbon dioxide (EtCO2) or Arterial carbon dioxide partial pressure(PaCO2) were included. Due to the source of clinical heterogeneity in the observed indicators in this study, we adopt random-effects model for analysis, and express it as the mean difference (MD) or risk ratio (RR) with a confidence interval of 95% (95%CI). We conducted a risk assessment of bias for eligible studies and assessed the overall quality of evidence for each outcome.

RESULTS

Fourteen RCTs and 1012 participants were finally included. We found the PaO2 was higher in HFNO group than FMV group with a MD (95% CI) of 57.38 mmHg (25.65 to 89.10; p = 0.0004) after preoxygenation and the safe apnoea time was significantly longer with a MD (95% CI) of 86.93 s (44.35 to 129.51; p < 0.0001) during anesthesia induction. There were no significant statistical difference in the minimum SpO2, CO2 accumulation, EtO2 and O2 desaturation rate during anesthesia induction between the two groups.

CONCLUSIONS

This systematic review and meta-analysis suggests that HFNO should be considered as an oxygenation tool for patients during anesthesia induction. Compared with FMV, continuous use of HFNO during anesthesia induction can significantly improve oxygenation and prolong safe apnoea time in surgical patients.

Noninvasive ventilation vs. high-flow nasal cannula oxygen for preoxygenation before intubation in patients with obesity: a post hoc analysis of a randomized controlled trial

BACKGROUND

Critically ill patients with obesity may have an increased risk of difficult intubation and subsequent severe hypoxemia. We hypothesized that pre-oxygenation with noninvasive ventilation before intubation as compared with high-flow nasal cannula oxygen may decrease the risk of severe hypoxemia in patients with obesity.

METHODS

Post hoc subgroup analysis of critically ill patients with obesity (body mass index ≥ 30 kg·m^-2) from a multicenter randomized controlled trial comparing preoxygenation with noninvasive ventilation and high-flow nasal oxygen before intubation of patients with acute hypoxemic respiratory failure (PaO₂/FiO₂ < 300 mm Hg). The primary outcome was the occurrence of severe hypoxemia (pulse oximetry < 80%) during the intubation procedure.

RESULTS

Among the 313 patients included in the original trial, 91 (29%) had obesity with a mean body mass index of 35 ± 5 kg·m^-2. Patients with obesity were more likely to experience an episode of severe hypoxemia during intubation procedure than patients without obesity: 34% (31/91) vs. 22% (49/222); difference, 12%; 95% CI 1 to 23%; P = 0.03. Among patients with obesity, 40 received preoxygenation with noninvasive ventilation and 51 with high-flow nasal oxygen. Severe hypoxemia occurred in 15 patients (37%) with noninvasive ventilation and 16 patients (31%) with high-flow nasal oxygen (difference, 6%; 95% CI - 13 to 25%; P = 0.54). The lowest pulse oximetry values during intubation procedure were 87% [interquartile range, 77-93] with noninvasive ventilation and 86% [78-92] with high-flow nasal oxygen (P = 0.98). After multivariable analysis, factors independently associated with severe hypoxemia in patients with obesity were intubation difficulty scale > 5 points and respiratory primary failure as reason for admission.

CONCLUSIONS

Patients with obesity and acute hypoxemic respiratory failure had an increased risk of severe hypoxemia during intubation procedure as compared to patients without obesity. However, preoxygenation with noninvasive ventilation may not reduce this risk compared with high-flow nasal oxygen. Trial registration Clinical trial number: NCT02668458 ( http://www.clinicaltrials.gov ).

Large variations of oxygen delivery in self-inflating resuscitation bags used for preoxygenation - a mechanical simulation

Background

Self-Inflating Resuscitation Bags (SIRB) are common and essential tools in airway management and ventilation. They are often used in resuscitation and emergency anaesthesia outside the operating theatre. There is a common notion that all SIRBs applied with a tight sealed mask will deliver close to 100 % oxygen during spontaneous breathing. The aim of the study was to measure the oxygen delivery of six commonly used SIRBs in a mechanical spontaneous breathing adult in vitro model.

Methods

Three SIRBs of each of the six models were evaluated for oxygen delivery during simulated breathing with an adult mechanical lung. The test was repeated three times per device (54 tests in total). The breathing profile was fixed to a minute volume of 10 L/min, a tidal volume of 500 mL and the SIRBs supplied with an oxygen fresh gas flow of 15 L/min. The fraction of delivered oxygen (FDO₂) was measured over a three-minute period. Average FDO₂ was calculated and compared at 30, 60 and 90 s.

Results

At 90 s all models had reached a stable FDO₂. Average FDO₂ at 90 s; Ambu Oval Plus 99,5 %; Ambu Spur II 99,8 %; Intersurgical BVM Resuscitator 76,7 %; Laerdal Silicone 97,3 %; Laerdal The Bag II 94,5 % and the O-Two Smart Bag 39,0 %. All differences in FDO₂ were significant apart from the two Ambu models.

Conclusions

In simulated spontaneous breathing, four out of six (by Ambu and Laerdal) Self-Inflating Resuscitation Bags delivered a high fraction of oxygen while two (Intersurgical and O-two) underperformed in oxygen delivery. These large variations confirm results reported in other studies. It is our opinion that underperforming Self-Inflating Resuscitation Bags might pose a serious threat to patients’ health if used in resuscitation and anaesthesia. Manufacturers of Self-Inflating Resuscitation Bags rarely provide information on performance for spontaneous breathing. This poses a challenge to all organizations that need their devices to deliver adequate oxygen during spontaneous breathing.

Airway Management in the Critically Ill Patient

Purpose of Review

This paper will evaluate the recent literature and best practices in airway management in critically ill patients.

Recent Findings

Cardiac arrest remains a common complication of intubation in these high-risk patients. Patients with desaturation or peri-intubation hypotension are at high risk of cardiac arrest, and each of these complications have been reported in up to half of all intubations in critically ill patient populations.

Summary

There have been significant advances in preoxygenation and devices available for performing laryngoscopy and rescue oxygenation. However, the risk of cardiovascular collapse remains concerningly high with few studies to guide therapeutic maneuvers to reduce this risk.

Comparison of hypoxemia, intubation procedure, and complications for non-invasive ventilation against high-flow nasal cannula oxygen therapy for patients with acute hypoxemic respiratory failure: a non-randomized retrospective analysis for effectiveness and safety (NIVaHIC-aHRF)

BACKGROUND

Optimization of preoxygenation procedure can help to secure the method of intubation by reducing the risks of severe hypoxemia and other problems. There is confusion for efficacy of non-invasive ventilation compared to high-flow oxygen therapy regarding occurrence of severe hypoxemia during the intubation procedure. The purpose of the study was to compare the difference between noninvasive ventilation and high flow oxygen therapy to prevent desaturation during laryngoscopy.

METHODS

Patients underwent high-flow nasal cannula oxygen therapy (HCO cohort, n = 161) or non-invasive ventilation procedure (NIV cohort, n = 154) for oxygenation and ventilation due to acute hypoxemic respiratory failure in the intensive care unit. Data before preoxygenation, preoxygenation, intubation, laryngoscopy, and complications of patients due to tracheal intubation were retrospectively collected and analyzed.

RESULTS

There was no difference between both cohorts for the demographical and clinical conditions of the patients before preoxygenation (p > 0.05 for all parameters), numbers of patients with severe hypoxia during the intubation procedure (35 vs. 45, p = 0.303), the time duration of laryngoscopy (p = 0.847), number of laryngoscopies attempts (p = 0.804), and immediate and late complications during the intubation procedure. The values of pulse oximetry were reported higher for patients of NIV cohort than those of HCO cohort during preoxygenation. Fewer numbers of patients were reported with severe hypoxia among patients of the NIV cohort than those of the HCO cohort (24 vs., 40, p = 0.042) who have moderate-to-severe hypoxemia (partial pressure of arterial oxygen to fraction of inspired oxygen ratio ≤ 200 mmHg) before preoxygenation. The most common complications were hypertension, pulmonary aspiration, and increased 30-day mortality.

CONCLUSIONS

When compared, there was no difference between non-invasive ventilation technique and high-flow oxygen therapy to minimize severe hypoxia prior to laryngoscopy and endotracheal intubation in patients with acute respiratory failure.

Emergency physician use of end-tidal oxygen monitoring for rapidsequence intubation

BACKGROUND

End-tidal oxygen (ETO2) monitoring is used by anesthesiologists to quantify the efficacy of preoxygenation before intubation but is generally not used in emergency departments (EDs). We have previously published our findings describing preoxygenation practices in the ED during blinded use of ETO2. The purpose of this investigation is to determine whether the unblinded use of ETO2 monitoring led to improvements in preoxygenation during rapid sequence intubation in the ED and also the oxygen device or technique changes that were used to achieve higher ETO2 levels.

METHODS

We conducted an interventional study at 2 academic EDs in Sydney, Australia and New York City, New York using ETO2 monitoring to investigate the preoxygenation process and effectiveness. We used data collected during a previous descriptive study for the control group, in which care teams in the same 2 EDs were blinded to the ETO2 value. In the study group, clinicians could utilize ETO2 to improve preoxygenation. Following an education process, clinicians were able to choose the method of preoxygenation and the techniques required to attempt to achieve an ETO2 level >85%. The primary outcome was the difference in ETO2 levels at the time of induction between the control and study group and the secondary outcome included the methods that were attempted to improve preoxygenation.

RESULTS

A convenience sample of 100 patients was enrolled in each group. The median ETO2 level achieved at the time of induction was 80% (interquartile range 61 to 86, overall range 73) in the control group and 90% in the study group (interquartile range 83 to 92, overall range 41); the median difference was 12 (95% confidence interval: 8, 16, P = < 0.001). The majority of oxygen device changes were from non-rebreather mask to bag-valve-mask (BVM) (15%, n = 15) and changes in technique from improvements in mask seal (54%, n = 34). The final device used in the study group was BVM in 87% of cases.

CONCLUSIONS

In 2 clinical studies of ETO2 in academic EDs, we have demonstrated that the use of ETO2 is feasible and associated with specific and potentially improved approaches to preoxygenation. A clinical trial is needed to further study the impact of ETO2 on the preoxygenation process and the rate of hypoxemia.

Study of early warning for desaturation provided by Oxygen Reserve Index in obese patients

Acute hemoglobin desaturation can reflect rapidly decreasing PaO₂. Pulse oximetry saturation (SpO₂) facilitates hypoxia detection but may not significantly decrease until PaO₂ < 80 mmHg. The Oxygen Reserve Index (ORI) is a unitless index that correlates with moderately hyperoxic PaO₂. This study evaluated whether ORI provides added arterial desaturation warning in obese patients. This IRB approved, prospective, observational study obtained written informed consent from Obese (body mass index (BMI) kg m^-2; 30 < BMI < 40) and Normal BMI (19 < BMI < 25) adult patients scheduled for elective surgery requiring general endotracheal anesthesia. Standard monitors and an ORI sensor were placed. Patient's lungs were pre-oxygenated with 100% FiO₂. After ORI plateaued, general anesthesia was induced, and endotracheal intubation accomplished using a videolaryngoscope. Patients remained apneic until SpO₂reached 94%. ORI and SpO₂ were recorded continuously. Added warning time was defined as the difference between the time to SpO₂ 94% from ORI alarm start or from SpO₂ 97%. Data are reported as median; 95% confidence interval. Complete data were collected in 36 Obese and 36 Normal BMI patients. ORI warning time was always longer than SpO₂ warning time. Added warning time provided by ORI was 46.5 (36.0-59.0) seconds in Obese and 87.0 (77.0-109.0) seconds in Normal BMI patients, and was shorter in Obese than Normal BMI patients difference 54.0 (38.0-74.0) seconds (p < 0.0001). ORI provided what was felt to be clinically significant added warning time of arterial desaturation compared to SpO₂. This added time might allow earlier calls for help, assistance from other providers, or modifications of airway management.Trial registration ClinicalTrials.gov NCT03021551.

Noninvasive ventilation support during fiberoptic bronchoscopy-guided nasotracheal intubation effectively prevents severe hypoxemia

Purpose

This study investigated the feasibility and efficacy of continuous noninvasive ventilation (NIV) support with 100% oxygen using a specially designed face mask, for reducing desaturation during fiberoptic bronchoscopy (FOB)-guided intubation in critically ill patients with respiratory failure.

Materials and methods

This was a single-center prospective randomized study. All patients undergoing FOB-guided nasal tracheal intubation were randomized to bag-valve-mask ventilation or NIV for preoxygenation followed by intubation. The NIV group were intubated through a sealed hole in a specially designed face mask during continuous NIV support with 100% oxygen. Control patients were intubated with removal of the mask and no ventilatory support.

Results

We enrolled 106 patients, including 53 in each group. Pulse oxygen saturation (SpO₂) after preoxygenation (99% (96%–100%) vs. 96% (90%–99%), p = .001) and minimum SpO₂ during intubation (95% (87%–100%) vs. 83% (74%–91%), p < .01) were both significantly higher in the NIV compared with the control group. Severe hypoxemic events (SpO₂ < 80%) occurred less frequently in the NIV group than in controls (7.4% vs. 37.7%, respectively; p < .01).

Conclusions

Continuous NIV support during FOB-guided nasal intubation can prevent severe desaturation during intubation in critically ill patients with respiratory failure.

Trial registration: ClinicalTrials.gov, NCT02462668. Registered on 25 May 2015, https://www.clinicaltrials.gov/ct2/results?term=NCT02462668.

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Our study is the first to evaluate NIV during FOB-guided nasotracheal intubation.

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NIV support during FOB-guided nasotracheal intubation was effectively prevented severe desaturation during intubation.

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We used a specially-designed intubation face mask to ensure that there was no interruption of NIV support during intubation.

Preoxygenation before intubation in adult patients with acute hypoxemic respiratory failure: a network meta-analysis of randomized trials

Background

Patients with acute hypoxemic respiratory failure are at risk for life-threatening complications during endotracheal intubation. Preoxygenation might help reduce the risk of hypoxemia and intubation-related complications. This network meta-analysis summarizes the efficacy and safety of preoxygenation methods in adult patients with acute hypoxemic respiratory failure.

Methods

We searched PubMed, EMBASE, and the Cochrane Library Central Register of Controlled Trials through April 2019 for randomized controlled trials (RCT) that studied the use of conventional oxygen therapy (COT), high-flow nasal cannula (HFNC), noninvasive ventilation (NIV), and HFNC and NIV as preoxygenation before intubation in patients with acute hypoxemic respiratory failure. Citations’ screening, study selection, data extraction, and risk of bias assessment were independently performed by two authors. The primary outcome was the lowest SpO₂ during the intubation procedure.

Results

We included 7 RCTs (959 patients). Patients preoxygenated with NIV had significantly less desaturation than patients treated with COT (mean difference, MD 5.53, 95% CI 2.71, 8.34) and HFNC (MD 3.58, 95% CI 0.59, 6.57). Both NIV (odds ratio, OR 0.43, 95% CI 0.21, 0.87) and HFNC (OR 0.49, 95% CI 0.28, 0.88) resulted in a lower risk of intubation-related complications than COT. There were no significant mortality differences among the use of NIV, HFNC, COT, and HFNC and NIV during preoxygenation.

Conclusions

In adult patients with acute hypoxemic respiratory failure, NIV is a safe and probably the most effective preoxygenation method.

High-flow Nasal Cannulae Versus Non-invasive Ventilation for Preoxygenation of Obese Patients: The PREOPTIPOP Randomized Trial

BACKGROUND

In obese patients, preoxygenation with non-invasive ventilation (NIV) was reported to improve outcomes compared with facemask. In this setting, high-flow nasal cannulae (HFNC) used before and during intubation has never been studied against NIV.

METHODS

The PREOPTIPOP study is a randomised, single-centre, open-labelled, controlled trial including obese patients requiring intubation before scheduled surgery. Patients were randomised to receive preoxygenation by HFNC or NIV. HFNC was maintained throughout intubation whereas NIV was removed when apnea occurred to perform laryngoscopy. The study was designed to assess the superiority of HNFC. The primary outcome was the lowest level of end-tidal oxygen concentration (EtO2) within 2 min after intubation. Secondary outcomes included drop in pulse oximetry and complications related to intubation.

MAIN FINDINGS

A total of 100 patients were randomised. The intent-to-treat analysis found median [IQR] lowest EtO2 of 76% [66-82] for HFNC and 88% [82-90] for NIV (mean difference - 12·1 [- 15·1 to - 8·5], p < 0·0001). Mild desaturation below 95% was more frequent with HFNC (30%) than with NIV (12%) (relative risk 2·5, IC 95% [1·1 to 5·9], p = 0·03) and median lowest SpO2 during intubation was 98% [93-99] in HFNC vs. 99% [97-100] in NIV (p = 0·03). Severe and moderate complications were not different but patients reported more discomfort with NIV (28%) vs. HFNC (4%), p = 0·001.

INTERPRETATION

Compared with NIV, preoxygenation with HFNC in obese patients provided lower EtO2 after intubation and a higher rate of desaturation < 95%.

FUNDING

Institutional funding, additional grant from Fisher & Paykel.

TRIAL REGISTRATION

Clinical trial Submission: April 10, 2017. Registry name: Preoxygenation Optimization in Obese Patients: High-flow Nasal Cannulae Oxygen Versus Non-invasive Ventilation: A Single-centre Randomised Controlled Study. The PREOPTIPOP Study. Clinicaltrials.gov identifier: NCT03106441 N°ID RCB: 2017-A00305-48. Institutional review Board: CPP Nord-Ouest I, registration number 019/2017. URL registry:https://clinicaltrials.gov/ct2/show/NCT03106441.

A survey of practice of rapid sequence induction for caesarean section in England

BACKGROUND

In view of newer techniques of preoxygenation and laryngoscopy and recent obstetric guidelines concerning the management of difficult intubation, we aimed to evaluate the current practice of rapid sequence induction for caesarean section in England.

METHODS

In 2017, 316 questionnaire surveys were posted to all 158 hospitals with caesarean section capabilities in England. At each hospital, one questionnaire was to be completed by the obstetric anaesthetic consultant lead and one by an anaesthetic trainee. Differences in responses between consultants and trainees, regardless of their place of work, were compared for all data using the chi-square and the Fisher's exact tests.

RESULTS

One-hundred-and-eighty complete questionnaires were returned, with an overall response rate of 57%, 98 (54%) from obstetric anaesthetic consultant leads and 82 (45.6%) from trainees). Both head up (57%) and ramped (56%) were the preferred positions for preoxygenation. Less than half of respondents (43%) preoxygenated until the surgeon was scrubbed. Cricoid pressure was used by almost all respondents (98%). Thiopentone (67%) was the most commonly chosen anaesthetic induction agent and most respondents (82%) supported a change to the use of propofol. Suxamethonium (92%) was the neuromuscular blocker of choice but more than half the respondents (52%) supported a change to rocuronium. In the event of a failed intubation, the rescue supraglottic airway device of choice was the i-gel® (65%).

CONCLUSIONS

Our survey demonstrated the significant variation in the practice of rapid sequence induction for caesarean section in obstetrics in the United Kingdom.

[Efficacy of preoxygenation using tidal volume breathing: a comparison of Mapleson A, Bain's and Circle system]

BACKGROUND

Efficacy of preoxygenation depends upon inspired oxygen concentration, its flow rate, breathing system configuration and patient characteristics. We hypothesized that in actual clinical scenario, where breathing circuit is not primed with 100% oxygen, patients may need more time to achieve EtO₂≥90%, and this duration may be different among various breathing systems. We thus studied the efficacy of preoxygenation using unprimed Mapleson A, Bain's and Circle system with tidal volume breathing at oxygen flow rates of 5L.min^-1 and 10L.min^-1.

METHODS

Patients were randomly allocated into one of the six groups, wherein they were preoxygenated using either Mapleson A, Bain's or Circle system at O₂ flow rate of either 5L.min^-1 or 10L.min^-1. The primary outcome measure of our study was the time taken to achieve EtO₂≥90% at 5 and 10L.min^-1 flow rates.

RESULTS

At oxygen flow rate of 5L.min^-1, time to reach EtO₂≥90% was significantly longer with Bain's system (3.7±0.67min) than Mapleson A and Circle system (2.9±0.6, 3.3±0.97min, respectively). However at oxygen flow rate of 10L.min^-1 this time was significantly shorter and comparable among all the three breathing systems (2.33±0.38min with Mapleson, 2.59±0.50min with Bain's and 2.60±0.47min with Circle system).

CONCLUSIONS

With spontaneous normal tidal volume breathing at oxygen flow rate of 5L.min^-1, Mapleson A can optimally preoxygenate patients within 3min while Bain's and Circle system require more time. However at O₂ flow rate of 10L.min^-1 all the three breathing systems are capable of optimally preoxygenating the patients in less than 3min.

Comparison of tidal volume and deep breath preoxygenation techniquesundergoing coronary artery bypass graft surgery: effects of hemodynamicresponse and arterial oxygenation

Background/aim: Different techniques exist for the preoxygenation of patients that will be operated on under general anesthesia. Preoxygenation with the deep breath (DB) method may affect cardiovascular stability, which is crucial for coronary artery bypass graft (CABG) patients. In this study, we aimed to compare the effects of the 3 min TVB preoxygenation technique and 1 min 8DBs technique on hemodynamic response and arterial oxygenation in patients with normal ejection fraction that were scheduled for elective CABG surgery. Materials and methods: Forty patients classified as ASA II?III and scheduled for elective CABG surgery were randomly assigned to TVB/3 min or 8DBs/1 min for preoxygenation. Cardiovascular variables, i.e. heart rate, mean arterial pressure, central venous pressure, cardiac index, systemic vascular resistance index, and stroke volume index, and arterial blood gas samples were analyzed before and after preoxygenation and at the end of the apneic period before intubation. Results: The preoxygenation methods affected the hemodynamic response similarly. PaO2 increased significantly with 8DBs compared to the TVB at the end of preoxygenation but was similar between the groups at the end of the apneic period (respectively, P: 0.03; P: 0.15). PaCO2 changes were similar between the groups. Conclusion: In patients with normal ejection fraction scheduled for CABG, 8DBs can be an alternative to TVB preoxygenation. Our results should be compared with those of other studies.

The oxygen reserve index (ORI): a new tool to monitor oxygen therapy

Supplemental oxygen is administered in the vast majority of patients in the perioperative setting and in the intensive care unit to prevent the potentially deleterious effects of hypoxia. On the other hand, the administration of high concentrations of oxygen may induce hyperoxia that may also be associated with significant complications. Oxygen therapy should therefore be precisely titrated and accurately monitored. Although pulse oximetry has become an indispensable monitoring technology to detect hypoxemia, its value in assessing the oxygenation status beyond the range of maximal arterial oxygen saturation (SpO₂ ≥97%) is very limited. In this hyperoxic range, we need to rely on blood gas analysis, which is intermittent, invasive and sometimes delayed. The oxygen reserve index (ORI) is a new continuous non-invasive variable that is provided by the new generation of pulse oximeters that use multi-wavelength pulse co-oximetry. The ORI is a dimensionless index that reflects oxygenation in the moderate hyperoxic range (PaO₂ 100-200 mmHg). The ORI may provide an early alarm when oxygenation deteriorates well before any changes in SpO₂ occur, may reflect the response to oxygen administration (e.g., pre-oxygenation), and may facilitate oxygen titration and prevent unintended hyperoxia. In this review we describe this new variable, summarize available data and preliminary experience, and discuss its potential clinical utilities in the perioperative and intensive care settings.

Respiratory support techniques to avoid desaturation in critically ill patients requiring endotracheal intubation: A systematic review and meta-analysis

PURPOSE

To evaluate which respiratory support method for critically ill patients undergoing endotracheal intubation (ETI) is associated with less desaturation.

METHODS

We searched PubMed, Cochrane Library, Scopus and CINAHL databases. We included randomized (RCT) and non-randomized (non-RCT) studies investigating any method of respiratory support before/during ETI compared to a reference control.

RESULTS

Apneic oxygenation (ApOx) was the most commonly investigated respiratory support technique for critically ill patients undergoing intubation (4 RCTs, 358 patients). Three of these studies investigated high-flow nasal cannula (HFNC) for ApOx while standard nasal cannula was used in one. Globally, ApOx was associated with higher minimum SpO₂ value compared to those receiving ETI without ApOx (mean difference 2.31%, 95% CI 0.42 to 4.20, p=0.02, I²=0%) but there were not significant differences between groups in severe hypoxemia and intubation related - complications. Concerning other techniques, noninvasive ventilation (NIV) was compared to bag-valve mask in only one RCT and it reduced the degree of desaturation.

CONCLUSIONS

ApOx was significantly associated with higher minimum SpO₂ registered during the intubation procedure. Further studies are needed to increase the number of included patients and demonstrate the benefit of ApOx and of other respiratory support methods (e.g. NIV, HFNC).

Preoxygenation and apneic oxygenation using Transnasal Humidified Rapid-Insufflation Ventilatory Exchange for emergency intubation

PURPOSE

Hypoxia is one of the leading causes of anesthesia-related injury. In response to the limitations of conventional preoxygenation, Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) has been used as a method of providing both preoxygenation and apneic oxygenation during intubation.

MATERIALS AND METHODS

In this prospective, observational study, THRIVE was introduced in a critical care unit (CCU), operating room (OR), and emergency department (ED) during emergency intubation of patients at high risk of hypoxia. Linear regression analysis tested for correlation between apnea time or body mass index and hemoglobin saturation (Spo₂).

RESULTS

Across 71 sequential patients, the interquartile range for apnea time and decrease in Spo₂ were 60 to 125 seconds and 0% to 3%, respectively. Significant desaturation occurred in 5 (7%) patients. There was no evidence of correlation between apnea time or body mass index and Spo₂ (R²=0.04 and 0.08 for CCU/ED and OR and 0.01 and 0.04 CCU/ED and OR, respectively). There were no complications reported from using THRIVE.

CONCLUSIONS

This study demonstrated that preoxygenation and apneic oxygenation using THRIVE were associated with a low incidence of desaturation during emergency intubation of patients at high risk of hypoxia in the CCU, OR, and ED. THRIVE has the potential to minimize the risk of hypoxia in these patient groups.

How to preoxygenate in operative room: healthy subjects and situations "at risk"

Intubation is one of the most common procedures performed in operative rooms. It can be associated with life-threatening complications when difficult airway access occurs, in patients who cannot tolerate even a slight hypoxemia or when performed in patients at risk of oxygen desaturation during intubation, as obese, critically-ill and pregnant patients. To improve intubation safety, preoxygenation is a major technique, extending the duration of safe apnoea, defined as the time until a patient reaches an arterial saturation level of 88% to 90%, to allow for placement of a definitive airway. Preoxygenation consists in increasing the lung stores of oxygen, located in the functional residual capacity, and helps preventing hypoxia that may occur during intubation attempts. Obese, critically-ill and pregnant patients are especially at risk of reduced effectiveness of preoxygenation because of pathophysiological modifications (reduced functional residual capacity (FRC), increased risk of atelectasis, shunt). Three minutes tidal volume breathing or 3-8 vital capacities are recommended in general population, mostly allowing achieving a 90% end-tidal oxygen level. Recent studies have indicated that in order to maximize the value of preoxygenation (i.e, oxygenation stores) obese and critically-ill patients can benefit from the combination of breathing 100% oxygen and non-invasive positive pressure ventilation (NIV) with end-expiratory positive pressure (PEEP) in the proclive position (Trendelenburg reverse). Recruitment manoeuvres may be of interest immediately after intubation to limit the risk of lung derecruitment. Further studies are needed in the field of preoxygenation in pregnant women.

[French national survey on difficult intubation in intensive care units]

OBJECTIVES

Assessing the theoretical knowledge, practical experience of French intensivists, and their compliance with French Anesthesiology and Critical Care Society's difficult airway algorithms of the expert's SFAR conference of 2006.

STUDY DESIGN

Prospective and descriptive national survey.

MATERIAL AND METHODS

An anonymous questionnaire with 40 questions was emailed to physicians working in intensive care units in France.

RESULTS

Five hundred and eight intensivists answered the survey. Ninety-seven percent of physicians reported having a portable storage unit for difficult intubation. As for practical experience, 421 physicians (83 %) have set up less than 10 laryngeal mask airway, 257 (51 %) have performed less than 10 intubations under fibroscopy and 269 (53 %) have never performed a cricothyroidotomy on mannequin, and 331 (65 %) on a patient. In case of emergency intubation, 29 % of them do not use a rapid sequence induction. Three hundred physicians (59 %) use capnography as monitoring of the endotracheal position. Two hundred and nine (42 %) consider they have not been trained to difficult intubation and 443 (87 %) would like to participate in high fidelity simulations mannequin.

CONCLUSIONS

National airway management algorithm was insufficiently followed. Alternative techniques do not seem to be mastered by all physicians. French intensivists expect more training on difficult intubation, including high fidelity simulation.

Effects of preoxygenation with the three minutes tidal volume breathing technique in the elderly

Background

Preoxygenation with tidal volume breathing for 3 min is commonly used technique. An end tidal expiratory oxygen concentration greater than 90% is considerd to be adequate for preoxygenation. The aim of this study was to check the effects of preoxygenation on elderly patients through the comparison with young patients during the 3 min tidal volume breathing technique.

Methods

Sixty patients from ASA class I or II who were scheduled for elective orthopedic general surgery were divided into an elderly (>65 yr) group and a control (25-65 yr) group. Patients were instructed in the technique of preoxygenation. Preoxygenation was accomplished with an appropriately sized face mask connected to an anesthesia machine with 100% oxygen during 3 min with patients in both groups. Expired O₂, CO₂ concentration and oxygen saturation were recorded simultaneously for 3 min.

Results

The elderly group showed significantly lower end tidal oxygen concentration than the control group from 50 sec to the end of study (180 sec) with the 3 min tidal volume breathing technique (P < 0.05). In 180 sec, the control group had over 90% (91.5%) end tidal oxygen concentration, but in the elderly group end tidal oxygen concentration could not reach 90% (86.2%). In oxygen saturation, the elderly group showed a significantly lower level until 40 sec from the start of study, and then two groups showed a similar levels of oxygen saturation until the end of study.

Conclusions

End tidal oxygen concentration did not reach 90% in 180 sec in the elderly group during preoxygenation with the 3 min tidal volume breathing technique.