Performances and limits of Bag-Valve-Device for pre-oxygenation and manual ventilation: A comparative bench and cadaver study.

INTRODUCTION: Bag-Valve-Device (BVD) is the most frequently used device for pre-oxygenation and ventilation during cardiopulmonary resuscitation (CPR). A minimal expired fraction of oxygen (FeO2) above 0.85 is recommended during pre-oxygenation while insufflated volume (VTi) should be reduced during manual ventilation. The objective was to compare the performances of different BVD in simulated conditions. METHODS: Nine BVD were evaluated during pre-oxygenation: spontaneous breathing patients were simulated on a test lung (mild and severe conditions). FeO2 was measured with and without positive end-expiratory pressure (PEEP). CO2 rebreathing was evaluated. Then, manual ventilation was performed by 36 caregivers (n = 36) from three hospitals on a specific manikin; same procedure was repeated by 3 caregivers (n = 3) on two human cadavers with three of the nine BVD: In non-CPR scenario and during mechanical CPR with Interrupted Chest Compressions strategy (30:2). RESULTS: Pre-oxygenation: FeO2 was lower than 0.85 for three BVD in severe condition and for two BVD in mild condition. FeO2 was higher than 0.85 in eight of nine BVD with an additional PEEP valve (PEEP 5 cmH2O). One BVD induced CO2 rebreathing. Manual ventilation: For non-CPR manual ventilation, mean VTi was within the predefined lung protective range (4-8 mL/kg PBW) for all BVD on the bench. For CPR manual ventilation, mean VTi was above the range for three BVD on the bench. Similar results were observed on cadavers. CONCLUSIONS: Several BVD did not reach the FeO2 required during pre-oxygenation. Manual ventilation was significantly less protective in three BVD. These observations are related to the different BVD working principles.

Pre-oxygenation using high-flow nasal oxygen versus tight facemask in trauma patients undergoing emergency anaesthesia.

BACKGROUND: Patients suffering from major traumatic injuries frequently require emergency anaesthesia. Due to often compromised physiology and the time-sensitive management, trauma patients may be more prone to desaturate during induction of anaesthesia. We hypothesised that pre-oxygenation using high-flow nasal oxygen would decrease the risk of desaturation during induction of anaesthesia in trauma patients and the study therefore aimed to compare the frequency of desaturation when pre-oxygenation was performed with high-flow nasal oxygen or a traditional facemask. METHODS: This exploratory, prospective, before-and-after study was conducted at the Karolinska University Hospital, Sweden. Adult (≥18 years of age) patients suffering major traumatic injuries needing emergency anaesthesia were included around the clock. Patients were pre-oxygenated using a tight-fitting facemask during the first nine months of enrollment. High-flow nasal oxygen was then introduced as a method for pre-oxygenation of trauma patients. The primary outcome was the proportion of patients desaturating <93% during induction of anaesthesia, assessed from the start of pre-oxygenation until one minute after intubation. Secondary outcomes included perceived difficulty of pre-oxygenation among anaesthetists (assessed on a scale between 1 and 10) and safety outcomes, such as incidence of regurgitations and intracranial gas (assessed radiologically). RESULTS: Data from 96 patients were analysed. Facemask pre-oxygenation was performed in 66 patients, while 30 patients were pre-oxygenated with high-flow nasal oxygen. The most frequent trauma mechanisms were stabbing injuries (n = 34 (35%)) and fall injuries (n = 21 (22%)). There were no differences in patient characteristics between the groups. Eight (12%) versus three (10%) patients desaturated <93% in the facemask and high-flow nasal oxygen group respectively, OR 0.81 (95% CI 0.20-3.28), p = .76. Anaesthetists assessed pre-oxygenation using high-flow nasal oxygen as easier compared to facemask pre-oxygenation. No patient in any group showed signs of regurgitation. Among patients with facial or skull fractures requiring anaesthesia before radiology was performed, intracranial gas was seen in four (40%) patients pre-oxygenated with a facemask and in no patient pre-oxygenated with HFNO (p = .23). CONCLUSION: In this prospective study investigating trauma patients undergoing emergency anaesthesia, we could not see any difference in the number of patients desaturating when pre-oxygenation was performed with high-flow nasal oxygen compared to a tight-fitting facemask. Pre-oxygenation using high-flow nasal oxygen was assessed as easier compared to facemask pre-oxygenation.

A quasi-experimental study of fresh oxygen flow on patients' oxygen reserve during mask-assisted ventilation under general anesthesia induction.

Background: To compare the effect of different amounts of fresh oxygen flow on oxygen reserve in patients undergoing general anesthesia. Methods: Seventy-two patients were enrolled in this quasi-experimental study. Patients were randomly divided into experimental groups with a fresh oxygen flow of 1 L/min, 2 L/min, 4 L/min, and 8 L/min (denoted as G1, G2, G3, and G4, respectively) for 2 min of mask-assisted ventilation. Safe apnea time (SAT) was the primary endpoint; SAT was defined as the time from the cessation of ventilation to the time the patient's pulse oxygen saturation (SpO2) decreased to 90%. Ventilation indicators such as end-tidal oxygen concentration (EtO2), end-tidal carbon dioxide partial pressure (EtCO2), SpO2, and carbon dioxide (CO2) elimination amount, during mask-assisted ventilation, were the secondary endpoints. Results: The SAT of G1, G2, G3, and G4 were 305.1 ± 97.0 s, 315 ± 112.5 s, 381.3 ± 118.6 s, and 359 ± 104.4 s, respectively (p > 0.05). The EtO2 after 2 min of mask-assisted ventilation in groups G1, G2, G3, and G4 were 69.7 ± 8.8%, 75.2 ± 5.0%, 82.5 ± 3.3%, and 86.8 ± 1.5%, respectively (p < 0.05). Also, there was a moderate positive correlation between the fresh oxygen flow and EtO2 (correlation coefficient r = 0.52, 95% CI 0.31-0.67, p < 0.0001). The CO2 elimination in the G1 and G2 groups was greater than that in the G4 group (p < 0.05). There was no significant difference in other indicators among the groups (all p > 0.05). Conclusion: The amount of fresh oxygen flow during mask-assisted ventilation was positively correlated with EtO2. Also, even though there was no significant difference, the patients' oxygen reserves increased with the increase in fresh oxygen flow.

Pressure-controlled versus manual facemask ventilation for anaesthetic induction in adults: A randomised controlled non-inferiority trial.

BACKGROUND: Pressure-controlled face mask ventilation (PC-FMV) with positive end-expiratory pressure (PEEP) after apnoea following induction of general anaesthesia prolongs safe apnoea time and reduces atelectasis formation. However, depending on the set inspiratory pressure, a delayed confirmation of a patent airway might occur. We hypothesised that by lowering the peak inspiratory pressure (PIP) when using PC-FMV with PEEP, confirmation of a patent airway would not be delayed as studied by the first return of CO2 , compared with manual face mask ventilation (Manual FMV). METHODS: This was a single-centre, randomised controlled non-inferiority trial. Seventy adult patients scheduled for elective day-case surgery under general anaesthesia with body mass index between 18.5 and 29.9 kg m-2 , American Society of Anesthesiologists (ASA) classes I-III, and without anticipated difficult FMV, were included. Before the start of pre-oxygenation and induction of general anaesthesia, participants were randomly allocated to receive ventilation with either PC-FMV with PEEP, at a PIP of 11 and a PEEP of 6 cmH2 O or Manual FMV, with the adjustable pressure-limiting valve set at 11 cmH2 O. The primary outcome variable was the number of ventilatory attempts needed until confirmation of a patent airway, defined as the return of at least 1.3 kPa CO2 . RESULTS: The return of ≥1.3 kPa CO2 on the capnography curve was observed after mean ± SD, 3.6 ± 4.2 and 2.5 ± 1.9 ventilatory attempts/breaths with PC-FMV with PEEP and Manual FMV, respectively. The difference in means (1.1 ventilatory attempts/breaths) had a 99% CI of -1.0 to 3.1, within the accepted upper margin of four breaths for non-inferiority. CONCLUSION: Following induction of general anaesthesia, PC-FMV with PEEP was used without delaying a patent airway as confirmed with capnography, if moderate pressures were used.

Pre-oxygenation using high-flow nasal oxygen in parturients undergoing caesarean section in general anaesthesia: A prospective, multi-centre, pilot study.

BACKGROUND: Parturients undergoing caesarean section in general anaesthesia have an increased risk of desaturating during anaesthesia induction. Pre- and peri-oxygenation with high-flow nasal oxygen prolong the safe apnoea time but data on parturients undergoing caesarean section under general anaesthesia are limited. This pilot study aimed to investigate the clinical effects and frequency of desaturation in parturients undergoing caesarean section in general anaesthesia pre- and peri-oxygenated with high-flow nasal oxygen and compare this to traditional pre-oxygenation using a facemask. METHODS: In this prospective, non-randomised, multi-centre study we included pregnant women with a gestational age ≥30 weeks undergoing caesarean section under general anaesthesia. All parturients were asked to participate in the intervention group consisting of pre-oxygenation using high-flow nasal oxygen. Parturients declining participation were pre-oxygenated with a traditional facemask. Primary outcome was the proportion of parturients desaturating below 93% from start of pre-oxygenation until 1 min after tracheal intubation. Secondary outcomes investigated end-tidal oxygen concentrations after tracheal intubation and the proportion of parturients with signs of regurgitation. RESULTS: A total of 34 parturients were included, 25 pre- and peri-oxygenated with high-flow nasal oxygen and 9 pre-oxygenated with facemask. No difference in patient or airway characteristics could be seen except for a higher BMI in the high-flow nasal oxygen group (31.4 kg m-2 [4.7] vs. 27.7 kg m-2 [3.1]; p = .034). No woman in any of the two groups desaturated below 93%. The lowest peripheral oxygen saturation observed, in any parturient, was 97%. There was no difference detected in end-tidal oxygen concentration after tracheal intubation, 87% (6) in the high-flow nasal oxygen group vs 80% (15) in the facemask group (p = .308). No signs of regurgitation, in any parturient, were seen. CONCLUSION: Pre- and peri-oxygenation with high-flow nasal oxygen maintain adequate oxygen saturation levels during induction of anaesthesia also in parturients. Regurgitation of gastric content did not occur in any parturient and no other safety concerns were observed in this pilot study.

Variability in oxygen delivery with bag-valve-mask devices: An observational laboratory simulation study.

A bag-valve-mask (BVM) is a portable handheld medical device commonly used in airway management and manual ventilation. Outside of the operating theatre, BVM devices are often used to pre-oxygenate spontaneously breathing patients before intubation to reduce the risk of hypoxaemia. Pre-oxygenation is considered adequate when the end-tidal expiratory fraction of oxygen is greater than 0.85. There are reports that some BVM devices fail to deliver a satisfactory inspired oxygen (FiO2) in spontaneously breathing patients due to variability in design. The primary aim of this study was to evaluate the efficacy of oxygen delivery of a broad range of adult and paediatric BVM devices at increasing tidal volumes using a mechanical lung to simulate spontaneous ventilation. The secondary aim was to evaluate the effect of BVM design on performance.Forty BVM devices were evaluated in a laboratory setting as part of a safety assessment requested by HealthShare New South Wales. The oxygen inlet of each BVM device was primed with 100% oxygen (15 l/min) for two min. The BVM device was then attached to the mechanical lung and commenced spontaneous breathing at a fixed respiratory rate of 12 breaths/min with an inspiratory: expiratory ratio of 1:2. For each device FiO2 was measured after two min of spontaneous breathing. This process was repeated with small (250 ml), medium (500 ml) and large (750 ml) tidal volumes simulating adult breathing in adult BVM devices, and small (150 ml), medium (300 ml) and large (450 ml) tidal volumes simulating paediatric breathing in paediatric BVM devices. The test was repeated using up to five BVM devices of the same model (where supplied) at each tidal volume as a manufacturing quality control measure.Eight of the 40 devices tested failed to deliver a FiO2 above 0.85 for at least one tidal volume, and five models failed to achieve this at any measured tidal volume. Concerningly, three of these devices delivered a FiO2 below 0.55. Six of the eight poorly performing devices delivered reducing concentrations of inspired oxygen with increasing tidal volumes. Devices which performed the worst were those with a duckbill non-rebreather valve and without a dedicated expiratory valve.Several BVM devices available for clinical use in Australia did not deliver sufficient oxygen for reliable pre-oxygenation in a spontaneously breathing in vitro model. Devices with a duckbill non-rebreather valve and without a dedicated expiratory valve performed the worst. It is imperative that clinicians using BVM devices to deliver oxygen to spontaneously breathing patients are aware of the characteristics and limitations of the BVM devices, and that the standards for manufacture are updated to require safe performance in all clinical circumstances.

[The role of HFNC oxygen in pre-oxygenation prior to intubation and the practice of invasive procedures]. / Place de l'oxygénothérapie haut débit dans la pré-oxygénation pour l'intubation et la pratique des gestes invasifs.

Over recent years, High Flow Nasal Cannula (HFNC) oxygen therapy has been more and more extensively applied in numerous medical settings, and it is now carried out in invasive procedures such as pre-oxygenation before orotracheal intubation, often leading to complications. More generally, pre-oxygenation is aimed at maintaining the highest possible oxygen saturation for extended periods of time. With this in mind, HFNC seems as effective as standard oxygen delivery with regard to hematosis in patients with mild or moderate hypoxemia, and it presents the advantage of reducing the adverse events associated with intubation. That said, during pre-oxygenation of patients with severe hypoxemia, non-invasive ventilation (NIV) is probably more effective than HFNC, especially in the prevention of respiratory events. However, in patients with little or no hypoxemia undergoing risky procedures such as bronchial endoscopy, HFNC allows better oxygen saturation than standard methods. To summarize, even though NIV remains useful in unstable patients, especially in decreasing desaturation episodes, HFNC could represent a reasonable alternative in case of poor tolerance, allowing continuous oxygenation of patients requiring digestive endoscopy or trans-esophageal ultrasound.

Ease and comfort of pre-oxygenation with high-flow nasal oxygen cannulae vs. facemask: a randomised controlled trial.

The Difficult Airway Society recommends that all patients should be pre-oxygenated before the induction of general anaesthesia, but this may not always be easy or comfortable and anaesthesia may often be induced without full pre-oxygenation. We tested the hypothesis that high-flow nasal oxygen cannulae would be easier and more comfortable than facemasks for pre-oxygenation. We randomly allocated 199 patients undergoing elective surgery aged ≥ 10 years to pre-oxygenation using either high-flow nasal oxygen or facemask. Ease and comfort were assessed by anaesthetists and patients on 10-cm visual analogue scale and six-point smiley face scale, respectively. Secondary endpoints included end-tidal oxygen fraction after securing a definitive airway and time to secure an airway. A mean difference (95%CI) between groups in ratings of -0.76 (-1.25 to -0.27) cm for ease of use (p = 0.003) and -0.45 (-0.75 to -0.13) points for comfort (p = 0.006), both favoured high-flow nasal oxygen. A mean difference (95%CI) between groups in end-tidal oxygen fraction of 3.89% (2.41-5.37%) after securing a definitive airway also favoured high-flow nasal oxygen (p < 0.001). There was no significant difference between groups in the number of patients with hypoxaemia (Sp O2 < 90%) or severe hypoxaemia (Sp O2 < 85%) lasting ≥ 1 min or ≥ 2 min; in the proportion of patients with an end-tidal oxygen fraction < 87% in the first 5 min after tracheal intubation (52.2% vs. 58.9% in facemask and high-flow nasal oxygen groups, respectively; p = 0.31); or in time taken to secure an airway (11.6 vs. 12.2 min in facemask and high-flow nasal oxygen groups, respectively; p = 0.65). In conclusion, we found pre-oxygenation with high-flow nasal oxygen to be easier for anaesthetists and more comfortable for patients than pre-oxygenation with a facemask, with no clinically relevant differences in end-tidal oxygen fraction after securing a definitive airway or time to secure an airway. The differences in ease and comfort were modest.

High-Flow Nasal Oxygenation and Its Applicability in COVID Patients.

High-flow nasal oxygenation (HFNO) is a type of oxygen therapy that provides humidified and heated oxygen through a nasal cannula at much higher flow rates than standard oxygen therapy, while also allowing control over the fraction of inspired oxygen (FIO2). Compared to standard oxygen therapy, it is much more comfortable for the patient and seems to alleviate most of the problems associated with standard oxygen therapy, such as dry nose, dry throat and nasal pain. It also provides a variety of benefits that can reduce the incidence of escalating treatment and initiating mechanical ventilation in COVID patients with acute hypoxemic respiratory failure (AHRF). This article provides an overview of HFNO and its current applications in COVID patients during the pandemic.

Pre-oxygenation with facemask oxygen vs high-flow nasal oxygen vs high-flow nasal oxygen plus mouthpiece: a randomised controlled trial.

High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min-1 by facemask; 50 l.min-1 by high-flow nasal cannulae only; or 50 l.min-1 by high-flow nasal cannulae plus 15 l.min-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.

Safety and efficacy of high-flow nasal oxygen for pre-oxygenation before anesthesia induction: a meta-analysis / 中华麻醉学杂志

Objective:To systematically review and evaluate the safety and efficacy of high-flow nasal oxygen (HFNO) for pre-oxygenation before anesthesia induction.Methods:Pubmed, Cochrane Library, Embase, China National Knowledge Infrastructure, Wanfang Database, China Science and Technology Journal Database and China Biomedical Literature Database were searched from inception to March 2022.All randomized controlled trials comparing HFNO and facemask ventilation for pre-oxygenation before anesthesia induction were collected.Two researchers independently assessed the quality of trials and extracted data.The primary outcome was the safe apnea time, the secondary outcomes were the lowest SpO 2 during intubation, oxygenation-related complications, patient comfort, PaO 2 and PaCO 2 before and after pre-oxygenation and after intubation.Meta-analysis was performed using RevMan 5.4 software. Results:Seventeen randomized controlled trials involving 843 patients were included in this meta-analysis.The results of meta-analysis showed that the safe apnea time was significantly longer ( MD=67.61, 95% CI 5.94-129.28, P=0.03), the lowest SpO 2 was higher during tracheal intubation ( MD=3.27, 95% CI 2.25-4.29, P<0.01), and PaO 2 was higher after pre-oxygenation ( MD=54.39, 95% CI 9.32-99.46, P=0.02) in the patients using HFNO than those using facemask ventilation.There were no statistically significant differences in the other outcomes ( P>0.05). Conclusions:HFNO for pre-oxygenation before anesthesia induction can significantly prolong the safe apnea time, increase the lowest SpO 2 during tracheal intubation, and improve the levels of PaO 2 after pre-oxygenation, and HFNO does not affect the patient′s comfort or increase the development of preoxygenation-related complications when compared with facemask ventilation.

Study on bioleaching of heavy metals and resource potential from tannery yard sludge.

Tannery sludge that has accumulated in the natural environment of a tannery industrial zone for a long time contains large amounts of toxic heavy metal elements such as Cr, which has a serious impact on the surrounding environment. This study used indigenous acidophilic sulfur-oxidizing bacteria from local tannery wastewater treatment plants to examine the effects of bioleaching on the removal of heavy metals in local tannery sludge accumulated in the natural environment. The effect of pre-oxygenation on bioleaching was investigated, and trends of sludge dewaterability during bioleaching and changes in the total amount of heavy metals, total nitrogen (TN), and total phosphorus (TP) during bioleaching were determined. Changes in the contents of different bound forms of heavy metals in tannery yard sludge during the bioleaching process were revealed. The experimental results showed that pre-oxygenation treatment of tannery yard sludge can shorten the bioleaching period (by at least 4 days) and improve the removal efficiency of all heavy metals. To ensure sludge dewaterability, the pH of the leaching system at the end of the bioleaching must not be lower than 1.67. The main components of heavy metals were stable in the tannery yard sludge, which critically affected the final removal efficiency of all heavy metals. The dissolution process of heavy metals showed that the morphology of heavy metals changed from stable to unstable forms in the bioleaching process, further dissolving into the liquid phase to be removed. In this experiment, the removal efficiency of all heavy metals in the tannery yard sludge was higher than 88.49%, and these heavy metals had good stability in morphology (the stable forms accounted for more than 87% of the total). In addition, the TN content in the remaining sludge was 27.9 g/kg, which is much higher than fertilizer TN requirements, indicating a high potential for resource utilization. Therefore, the method of bioleaching to remove heavy metals in tannery yard sludge for reuse is worthy of in-depth study and promotion.

Injectable oxygenation therapeutics: evaluating the oxygen delivery efficacy of artificial oxygen carriers and kosmotropes in vitro.

The aim of this paper was to utilise an existing in vitro setup to quantify the oxygen offloading capabilities of two different subsets of injectable oxygenation therapeutics: (1) artificial oxygen carriers (AOCs), which bind or dissolve oxygen and act as transport vectors, and (2) kosmotropes, which increase water hydrogen bonding and thereby decrease the resistance to oxygen movement caused by the blood plasma. Dodecafluoropentane emulsion (DDFPe) was chosen to represent the AOC subset while trans sodium crocetinate (TSC) was selected to represent the kosmotrope subset. PEG-Telomer-B (PTB), the surfactant utilised to encapsulate DDFP in emulsion form, was also tested to determine whether it affected the oxygen transport ability of DDFPe. The in vitro set-up was used to simulate a semi closed-loop circulatory system, in which oxygen could be delivered from the lungs to hypoxic tissues. Results of this study showed that (1) 0.5 ml of a PFC outperformed 6.25 ml of a kosmotrope in a controlled, in vitro setting and (2) that PTB and sucrose do not contribute to the overall oxygen transportation efficacy of DDFPe. These results could be therapeutically beneficial to ongoing and future pre-clinical and clinical studies involving various oxygenation agents.

Pre-oxygenation using high-flow nasal oxygen vs. tight facemask during rapid sequence induction.

Pre-oxygenation using high-flow nasal oxygen can decrease the risk of desaturation during rapid sequence induction in patients undergoing emergency surgery. Previous studies were single-centre and often in limited settings. This randomised, international, multicentre trial compared high-flow nasal oxygen with standard facemask pre-oxygenation for rapid sequence induction in emergency surgery at all hours of the day and night. A total of 350 adult patients from six centres in Sweden and one in Switzerland undergoing emergency surgery where rapid sequence induction was required were included and randomly allocated to pre-oxygenation with 100% oxygen using high-flow nasal oxygen or a standard tight-fitting facemask. The primary outcome was the number of patients developing oxygen saturations <93% from the start of pre-oxygenation until 1 min after tracheal intubation. Data from 349 of 350 patients who entered the study were analysed (174 in the high-flow nasal oxygen group and 175 in the facemask group). No difference was detected in the number of patients desaturating <93%, five (2.9%) vs. six (3.4%) patients in the high-flow nasal oxygen and facemask group, respectively (p = 0.77). The risk of desaturation was not increased during on-call hours. No difference was seen in end-tidal carbon dioxide levels in the first breath after tracheal intubation or in the number of patients with signs of regurgitation between groups. These results confirm that high-flow nasal oxygen maintains adequate oxygen levels during pre-oxygenation for rapid sequence induction.

Apnoeic oxygenation for emergency anaesthesia of pre-hospital trauma patients.

BACKGROUND: Efficient and timely airway management is universally recognised as a priority for major trauma patients, a proportion of whom require emergency intubation in the pre-hospital setting. Adverse events occur more commonly in emergency airway management, and hypoxia is relatively frequent. The aim of this study was to establish whether passive apnoeic oxygenation was effective in reducing the incidence of desaturation during pre-hospital emergency anaesthesia. METHODS: A prospective before-after study was performed to compare patients receiving standard care and those receiving additional oxygen via nasal prongs. The primary endpoint was median oxygen saturation in the peri-rapid sequence induction period, (2 minutes pre-intubation to 2 minutes post-intubation) for all patients. Secondary endpoints included the incidence of hypoxia in predetermined subgroups. RESULTS: Of 725 patients included; 188 patients received standard treatment and 537 received the intervention. The overall incidence of hypoxia (first recorded SpO2 < 90%) was 16.7%; 10.9% had SpO2 < 85%. 98/725 patients (13.5%) were hypoxic post-intubation (final SpO2 < 90% 10 minutes post-intubation). Median SpO2 was 100% vs. 99% for the standard vs. intervention group. There was a statistically significant benefit from apnoeic oxygenation in reducing the frequency of peri-intubation hypoxia (SpO2 < =90%) for patients with initial SpO2 > 95%, p = 0.0001. The other significant benefit was observed in the recovery phase for patients with severe hypoxia prior to intubation. CONCLUSION: Apnoeic oxygenation did not influence peri-intubation oxygen saturations, but it did reduce the frequency and duration of hypoxia in the post-intubation period. Given that apnoeic oxygenation is a simple low-cost intervention with a low complication rate, and that hypoxia can be detrimental to outcome, application of nasal cannulas during the drug-induced phase of emergency intubation may benefit a subset of patients undergoing emergency anaesthesia.

A prospective, up-down sequential allocation study investigating the effectiveness of vital capacity breaths using high-flow nasal oxygenation versus a tight-fitting face mask to pre-oxygenate term pregnant women.

BACKGROUND: The role of high flow nasal oxygenation (HFNO) for pre-oxygenation before obstetric general anaesthesia remains unclear. This study aimed to determine the number of vital capacity breaths using HFNO required to pre-oxygenate 90% of parturients to an end-tidal oxygen concentration fraction (FETO2) of ≥0.90 (termed EN90). METHODS: Using up-down, sequential allocation trial design, volunteer term parturients undergoing caesarean delivery were investigated with HFNO with their mouth closed, followed by mouth open, and if FETO2 ≥0.90 was not achieved after a maximum of 20 vital capacity breaths, pre-oxygenation was attempted with a face mask. The primary outcome was the number of vital capacity breaths required using HFNO (mouth open and closed) to achieve EN90. Secondary outcomes included assessment of EN90 using mouth open versus mouth closed and face mask pre-oxygenation, maternal satisfaction and evaluation of fetal cardiotocography. RESULTS: Twenty women at term were recruited. Successful pre-oxygenation occurred in 4 (20%), 3 (15%) and 14 (70%) women with HFNO mouth closed, HFNO mouth open, and via face mask respectively. At up to 20 vital capacity breaths, face mask pre-oxygenation was more successful at achieving EN90 compared with both HFNO with a closed (P=0.006) or open (P=0.001) mouth. Closed mouth HFNO did not outperform open mouth pre-oxygenation. CONCLUSION: Face mask pre-oxygenation is more effective at achieving EN90 compared with to HFNO within a clinically acceptable number of vital capacity breaths. Further studies are needed to determine the role of HFNO in optimising the time before desaturation and for apnoeic oxygenation in term parturients.

Oxygenation before Endoscopic Sedation Reduces the Hypoxic Event during Endoscopy in Elderly Patients: A Randomized Controlled Trial.

BACKGROUND: Sedation endoscopy increases patient and examiner satisfaction but involves complications. The most serious complication is hypoxia, the risk factors for which are old age, obesity, and American Society of Anesthesiologists physical status of 3 or greater. However, clear evidence of oxygenation during sedation endoscopy for elderly people is lacking in US, European, and Korean guidelines. METHOD: This study was conducted for 1 year starting in August 2018 to evaluate whether pre-oxygenation use 1 min before sedation endoscopy could reduce the incidence of hypoxia in patients older than 65 years of age. A total of 70 patients were divided into the non-oxygenated group (n = 35; control group) and oxygen-treated group (n = 35; experimental group) during endoscopy. RESULT: The incidence of hypoxia was 28 (80%) in the control group versus 0 (0%) in the pre-oxygenated group. Factors related to hypoxia in the non-oxygenated group were a relatively high dose of midazolam and concomitant injection with narcotic analgesics such as pethidine. CONCLUSION: The incidence of hypoxia during sedation endoscopy is high in patients over 65 years, but oxygenation during endoscopic sedation in elderly people can significantly reduce the incidence of intraprocedural hypoxic events.