All India Difficult Airway Association 2016 guidelines for the management of unanticipated difficult tracheal intubation in adults

The All India Difficult Airway Association (AIDAA) guidelines for management of the unanticipated difficult airway in adults provide a structured, stepwise approach to manage unanticipated difficulty during tracheal intubation in adults. They have been developed based on the available evidence; wherever robust evidence was lacking, or to suit the needs and situation in India, recommendations were arrived at by consensus opinion of airway experts, incorporating the responses to a questionnaire sent to members of the AIDAA and the Indian Society of Anaesthesiologists. We recommend optimum pre-oxygenation and nasal insufflation of 15 L/min oxygen during apnoea in all patients, and calling for help if the initial attempt at intubation is unsuccessful. Transnasal humidified rapid insufflations of oxygen at 70 L/min (transnasal humidified rapid insufflation ventilatory exchange) should be used when available. We recommend no more than three attempts at tracheal intubation and two attempts at supraglottic airway device (SAD) insertion if intubation fails, provided oxygen saturation remains ≥ 95%. Intubation should be confirmed by capnography. Blind tracheal intubation through the SAD is not recommended. If SAD insertion fails, one final attempt at mask ventilation should be tried after ensuring neuromuscular blockade using the optimal technique for mask ventilation. Failure to intubate the trachea as well as an inability to ventilate the lungs by face mask and SAD constitutes 'complete ventilation failure', and emergency cricothyroidotomy should be performed. Patient counselling, documentation and standard reporting of the airway difficulty using a 'difficult airway alert form' must be done. In addition, the AIDAA provides suggestions for the contents of a difficult airway cart.

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.

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.

Efficacy and Safety of Using High-Flow Nasal Oxygenation in Patients Undergoing Rapid Sequence Intubation

Objective

To assess the efficacy and safety of high-flow nasal oxygen (HFNO) therapy in patients undergoing rapid sequence intubation (RSI) for emergency abdominal surgery.

Methods

HFNO of 60 L.min^-1 at an inspiratory oxygen fraction of 1 was delivered 4 min before laryngoscopy and maintained until the patient was intubated, and correct intubation was verified by the appearance of the end-tidal CO₂ (EtCO₂) waveform. Transcutaneous oxygenation (SpO₂), heart rate and non-invasive mean arterial pressure were monitored at baseline (T0), after 4 min on HFNO (T1) and at the time of laryngoscopy (T2) and endotracheal intubation (ETI) (T3). An SpO₂ of <3% from baseline was recorded at any sampled time. The value of EtCO₂ at T3 was registered after two mechanical breaths. The apnoea time was defined as the time from the end of propofol injection to ETI. RSI was performed with propofol, fentanyl and rocuronium.

Results

Forty-five patients were enrolled. SpO₂ levels showed a statistically significant increase at T1, T2 and T3 compared with those at T0 (p<0.05); median SpO₂% (interquartile range) was 97% (range, 96%-99%) at T0, 99% (range, 99%-100%) at T1, 99% (range, 99%-100%) at T2 and 99% (range, 99%-100%) at T3. Minimal SpO₂ was 96%; no patient showed an SpO₂ of <3% from baseline; mean EtCO₂ at the time of ETI was 36±4 mmHg. Maximum apnoea time was 12 min.

Conclusion

HFNO is an effective and safe technique for pre-oxygenation in patients undergoing rapid sequence induction of general anaesthesia for emergency surgery.

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 (S_p O₂  < 90%) or severe hypoxaemia (S_p 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.

Effect of positive airway pressure during pre-oxygenation and induction of anaesthesia upon safe duration of apnoea

BACKGROUND AND AIMS

Induction of general anaesthesia per se as also the use of 100% oxygen during induction of anaesthesia, results in the development of atelectasis in dependent lung regions within minutes of anaesthetic induction. We aimed to assess the effect of application of a continuous positive airway pressure (CPAP) of 5 cm H2O during pre-oxygenation and induction of anaesthesia on the period of apnoea before the occurrence of clinically significant desaturation.

METHODS

In this prospective, randomised, and double-blind study, 40 patients posted for elective surgery were enrolled. Duration of apnoea was measured as the time from the administration of succinylcholine hydrochloride to the time when oxygen saturation fell to 93%. Student's t-test was used for comparing the duration of apnoea.

RESULTS

The safe duration of apnoea was found to be significantly longer in patients receiving CPAP of 5 cm H2O (Group P; n = 16) compared to the group receiving no CPAP (Group Z; n = 20), that is, 496.56 ± 71.68 s versus 273.00 ± 69.31 s (P < 0.001).

CONCLUSION

The application of CPAP of 5 cm H2O using a Mapleson A circuit with a fixed positive end-expiratory pressure device during 5 min of pre-oxygenation with 100% oxygen prior to the induction of anaesthesia provides a clearly longer duration of apnoea before clinically significant arterial desaturation occurs.

Techniques of preoxygenation in patients with ineffective face mask seal

Background:

Ineffective face mask seal is the most common cause for suboptimal pre-oxygenation. Room air entrainment can be more with vital capacity (VC) breaths when the mask is not a tight fit.

Aims:

This study was designed to compare 5 min tidal volume (TV) breathing and eight VC breaths in patients with ineffective face mask seal.

Methods:

Twenty eight ASA I adults with ineffective face mask seal were randomized to breathe 100% oxygen at normal TV for 5 min (Group TV) and eight VC breaths (Group VC) in a cross over manner through circle system at 10 L/min. End tidal oxygen concentration (EtO₂) and arterial blood gas analysis was performed to evaluate oxygenation with each technique.

Statistical and Analysis:

Data were analysed using SPSS statistical software, version 16. Friedman's two-way analysis of variance by ranks was used for non-parametric data.

Results:

Significant increase in EtO₂ (median 90) and PaO₂ (228.85) was seen in group TV when compared to group VC (EtO₂ median 85, PaO₂ 147.65), P<0.05. Mean total ventilation volume in 1 min in group VC was 9.4±3.3 L/min and more than fresh gas flow (10 L/min) in seven patients. In group TV, the fresh gas flow (50 L/5 min) was sufficient at normal TV (mean total ventilation in 5 min 36.7±6.3 L/min).

Conclusions:

TV breathing for 5 min provides better pre-oxygenation in patients with ineffective mask seal with fresh gas flow of 10 L/min delivered through a circle system.

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.

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.

Intubation practices for children in emergency departments and intensive care units across Australia and New Zealand: A survey of medical staff

OBJECTIVE

Intubation of children in the emergency setting is a high-risk, low incidence event. Standardisation of clinical practice has been hampered by a lack of high-quality evidence to support one technique over another. The aim of the present study is to determine clinician preference in intubation practice of children in EDs and ICUs in Australia and New Zealand to provide baseline information to allow future targeted research focused on improving the safety and efficacy of paediatric emergency airway management.

METHODS

The present study was a voluntary questionnaire undertaken by medical staff at registrar level or above in EDs and ICUs associated with the Paediatric Research in Emergency Departments International Collaborative (PREDICT) and Australia and New Zealand Intensive Care Society Paediatric Study Group (ANZICS PSG) research networks. Respondents reported on their individual intubation practices, with a focus on pre-oxygenation and apnoeic oxygenation techniques, and the use of video laryngoscopy.

RESULTS

A total of 502 clinicians were invited to complete the survey between May and October 2018 with 336 (66.9%) responded. There was marked variation in practice between ED clinicians and ICU clinicians in the techniques used for pre-oxygenation, the frequency of use of apnoeic oxygenation and the reported use of video laryngoscopy.

CONCLUSIONS

Within Australia and New Zealand there is considerable variation in paediatric emergency airway clinical practice, in particular with respect to pre-oxygenation, apnoeic oxygenation and use of video laryngoscopy. Definitive clinical trials are required to best inform clinical practice in this area.

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.

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.

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.

Volume-controlled inverse ratio ventilation improves safe apnea time in obese patients during the induction of general anesthesia: a randomized controlled trial

Background

Inverse ratio ventilation theoretically increases oxygenation in obese patients. However, it is unknown whether the use of inverse ratio ventilation prolongs the safe apnea time during the induction of anesthesia. The primary objective of our study was to compare the safe apnea time between obese surgical patients receiving inverse ratio ventilation and conventional ratio ventilation during the induction of anesthesia.

Methods

This study is a prospective, randomized controlled trial. Forty obese patients who underwent elective operation under general anesthesia with endotracheal intubation were randomly allocated into the conventional ratio ventilation (CRV) group (n = 20) and inverse ratio ventilation (IRV) group (n = 20). After the patients were preoxygenated through a face mask for 3 min, anesthesia induction was performed. When the patients lost consciousness and spontaneous breathing disappeared, non-invasive positive pressure ventilation was performed for 5 min, and the inspiratory-to-expiratory (I:E) ratio was set as 1:2 in the CRV group and 2:1 in the IRV group. Heart rate, systolic blood pressure, diastolic blood pressure, and pulse oxygen saturation were recorded at four time points: (i) before pre-oxygenation (T0), (ii) pre-oxygenation for 3 min (T1), (iii) non-invasive positive pressure ventilation for 3 min (T2), and (iv) non-invasive positive pressure ventilation for 5 min (T3). Arterial blood was collected at T0, T1, and T3 for arterial blood gas analysis, and arterial oxygen partial pressure and carbon dioxide partial pressure were recorded. The patient's expiratory oxygen fraction at T1, T2, and T3 were recorded. Peak airway pressure, plateau pressure and mean airway pressure were record at T2 and T3. The safe apnea time was recorded in both groups.

Results

Forty patients completed the study. Baseline parameters were comparable between the two groups. Safe apnea time was significantly longer (210.40 ± 47.47 vs. 153.80 ± 41.54 s, mean difference [95% CI], 56.55 [28.00-85.10], p = 0.0003) and the expired O2 fraction was higher (87.60 ± 2.39 vs. 91.60 ± 1.79, mean difference [95% CI], 4.00 [2.65-5.35], p < 0.0001) at T3 in the IRV group compared to the CRV group.

Conclusion

Volume-controlled inverse ratio ventilation at an I:E ratio of 2:1, compared to conventional ratio ventilation, provided a longer safe apnea time and higher expired O2 fraction in obese patients during the induction of anesthesia.

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.

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.

Assessment of Preoxygenation using Real-Time End-Tidal Oxygen Measurements Versus Single-Breath End-Tidal Oxygen Measurements in Healthy Volunteers

Objective

Preoxygenation decreases morbidity for patients requiring endotracheal intubation. However, rigorous means for determining adequate pre-oxygenation are limited in the emergency department (ED). End-tidal oxygenation (EtO2) monitoring could potentially improve preoxygenation in the ED. The accuracy of nasal cannula (NC) EtO2 in patients receiving supplemental oxygen is unknown. Our study examined the correlation between NC EtO2 and single-breath (SB) EtO2.

Methods

Healthy volunteers were randomized to receive supplemental oxygen via a nonrebreather mask (NRBM) or a noninvasive ventilation mask (NIV). Participants underwent 3-minute trials at 3 different settings: NRBM at 15 liters per minute (LPM), 35 LPM, and 55 LPM, or NIV at 40% fraction of inspired oxygen (FiO2), 70% FiO2, and 100% FiO2. NC EtO2 and SB EtO2 were obtained at the end of each trial.

Results

Complete data were obtained for 104 participants. Beta regression analysis revealed a strong correlation between NC EtO2 and SB EtO2 in the NIV group (pR2 = 0.7) and a moderate correlation (pR2 = 0.4) in the NRBM group. Mean differences in the NRBM arm were 13.1% (15 LPM), 18.0% (35 LPM), 17.1% (55 LPM), and 1.8% (40% FiO2), 5.1% (70% FiO2), and 10.1% (100% FiO2) in the NIV arm.

Conclusions

Supplemental oxygen led to an overestimation of NC EtO2 across both groups, with NRBM more than NIV. The correlation between SB EtO2 and NC EtO2 suggests NC EtO2 may be useful in assessing preoxygenation in real-time. Further study is needed to examine its clinical efficacy in preventing desaturation events during endotracheal intubation in the ED.