End-tidal Oxygen Concentration Research Articles

Efficacy of high-flow nasal oxygenation during induction of general anaesthesia in parturients living with obesity: a two-centre, prospective, randomised clinical trial.

High-flow nasal oxygenation has been shown to improve oxygenation during induction of anaesthesia in parturients who are not obese. However, data on the efficacy of high-flow nasal oxygen in parturients living with obesity are lacking. This study investigated the effects of high-flow nasal oxygenation on pre-oxygenation and apnoea oxygenation during tracheal intubation in parturients living with obesity. This prospective, randomised clinical trial was conducted at two tertiary hospitals and included parturients with BMI > 30 kg.m-2 undergoing scheduled caesarean delivery under general anaesthesia. Parturients were allocated randomly to standard facemask or high-flow nasal oxygen groups (oxygen flow rates 10 l.min-1 and 50 l.min-1, respectively). The primary outcome measure was arterial partial pressure of oxygen after 3 min of pre-oxygenation. 54 patients completed the study. The arterial partial pressure of oxygen after 3 min of pre-oxygenation was significantly lower in parturients allocated to the standard facemask group compared with those allocated to the high-flow nasal oxygen group (mean (SD) 40.1 (8.9) kPa vs. 53.8 (9.7) kPa, p < 0.001). End-tidal oxygen concentration on commencing ventilation was also lower in parturients allocated to the standard facemask group compared with those allocated to the high flow-nasal oxygen group (mean (SD) 78.3 (5.38)% vs. 86.2 (5.10)%, p < 0.001). The arterial partial pressure of carbon dioxide post tracheal intubation and fetal outcomes were similar in both groups. Pre-oxygenation using high-flow nasal oxygenation provided a higher arterial partial pressure of oxygen and end-tidal oxygen concentration during general anaesthesia induction than standard facemask oxygenation in parturients living with obesity; however, the differences were not clinically meaningful. High-flow nasal oxygenation may be considered as an alternative option for pre-oxygenation during rapid sequence induction in parturients living with obesity.

11 The Effect of Apneic Oxygenation on End-Tidal Oxygen Concentration During Rapid Sequence Intubation

11 The Effect of Apneic Oxygenation on End-Tidal Oxygen Concentration During Rapid Sequence Intubation

Role of Alveolar-Arterial Difference in Estimation of Extravascular Lung Water in COVID-19-Related ARDS.

The dominant feature of COVID-19-associated ARDS is gas exchange impairment. Extravascular lung water index is a surrogate for lung edema and reflects the level of alveolocapillary disruption. The primary aim was the prediction of extravascular lung water index by the alveolar-arterial oxygen difference. The secondary aims were in determining the relationship between the extravascular lung water index and other oxygenation parameters, the [Formula: see text], end-tidal oxygen concentration, pulmonary oxygen gradient ([Formula: see text] minus end-tidal oxygen concentration), and [Formula: see text]. This observational prospective single-center study was performed at the Department of Anaesthesiology and Intensive Care, The University Hospital in Ostrava, The Czech Republic, during the COVID-19 pandemic, from March 20, 2020, until May 24, 2021. The relationship between the extravascular lung water index and alveolar-arterial oxygen difference showed only a mild-to-moderate correlation (r = 0.33, P < .001). Other extravascular lung water index correlations were as follows: [Formula: see text] (r = 0.33, P < .001), end-tidal oxygen concentration (r = 0.26, P = .0032), [Formula: see text] minus end-tidal oxygen concentration (r = 0.15, P = .0624), and [Formula: see text] (r = -0.15, P = .01). The alveolar-arterial oxygen difference does not reliably correlate with the extravascular lung water index and the degree of lung edema in COVID-19-associated ARDS.

Pre-oxygenation using high flow humidified nasal oxygen or face mask oxygen in pregnant people – a prospective randomised controlled crossover non-inferiority study (The HINOP2 study)

BackgroundAirway guidelines recommend pre-oxygenation of obstetric patients to an end tidal oxygen concentration (etO2) ≥90%. High flow nasal oxygen (HFNO) achieves this in 60% of pregnant people. However face mask (FM) pre-oxygenation also may not achieve this target in all patients. In this study we determined whether HFNO pre-oxygenation is non-inferior to FM pre-oxygenation. MethodsThis randomised controlled crossover non-inferiority trial was conducted on healthy participants of gestational age ≥37 weeks in a simulated environment. Participants underwent pre-oxygenation for three minutes with HFNO and FM oxygen in randomised order. HFNO was delivered at a maximal flow of 70 l.min-1 and FM oxygen at 10 l.min-1. The primary outcome was etO2 on first expired breath after pre-oxygenation. Non-inferiority was defined as a mean difference in first etO2 between groups of ≤5%. ResultsSeventy participants were randomised with 62 analysed. Age (mean (SD)), gestation (median (IQR)), and body mass index (median (IQR)), were 34.7 (4.6) years, 39 (38.4, 39.4) weeks, 29 (26.6, 32.4) kg.m-2 respectively. First etO2 after HFNO pre-oxygenation was greater than after FM pre-oxygenation (HFNO pre-oxygenation mean (SD) 90.2 (3.9)% versus FM pre-oxygenation 88.7 (3.0)%; mean difference = 1.45%, 95% CI 0.19 to 2.72%; p = 0.025. Forty-four (71%) participants achieved ≥90% first etO2 concentration after HFNO pre-oxygenation versus 27 (44%) after FM pre-oxygenation (p = 0.002). ConclusionsIn this cohort of pregnant people at term in a simulated environment, pre-oxygenation with HFNO was not inferior to FM pre-oxygenation. FM pre-oxygenation did not achieve pre-oxygenation targets in over 50% of participants.

Partial Pressure of End-Tidal Oxygen and Blood Lactate During Cardiopulmonary Exercise Testing in Healthy Older Participants and Patients at Risk of Cardiac Disease.

The partial pressure of end-tidal oxygen (PETO2) and end-tidal oxygen concentration (ETO2) are among the indices that can be measured by exhaled gas analysis. Several observational studies have shown that skeletal muscle function is impaired in patients with cardiac disease; thus, the assessment of skeletal muscle function is important. Additionally, although it has recently been suggested that the difference in PETO2 from rest to the ventilatory anaerobic threshold (VAT) reflects oxygen availability in peripheral factors, primarily skeletal muscle, the evidence for this is not well established. Therefore, we hypothesized and investigated whether increased blood lactate (BLa) levels, resulting from decreased skeletal muscle and mitochondrial oxygen availability, and PETO2 dynamics during cardiopulmonary exercise testing (CPET) would be related. All participants performed the symptomatic limited CPET, and their BLa levels were measured. The difference in PETO2 and ETO2 from rest to VAT determined by the V-slope method (ΔPETO2 and ΔETO2) was calculated and compared with the increase in BLa due to exercise testing. We recruited 22 healthy older participants (nine males; 69.4 ± 6.8 years) and 11 patients with cardiovascular risk (eight males; 73.0 ± 8.8 years). ΔPETO2 and ΔETO2 did not differ between the two groups (P = 0.355 and P = 0.369, respectively), showing no correlation between increase in BLa from rest to VAT, but were significantly correlated with an increase in BLa from rest to the end of exercise (ΔPETO2, P = 0.030; ΔETO2, P = 0.029). The correlation was particularly pronounced among those at cardiovascular risk (ΔPETO2, P = 0.012; ΔETO2, P = 0.011). ΔPETO2 and ΔETO2 from rest to VAT during CPET may be useful as indices reflecting skeletal muscle oxygen utilization capacity.

Use of a Nasal Cannula as a Preoxygenation Adjunct: A Randomized Crossover Study.

Preoxygenation prior to induction of general anesthesia is intended to increase the oxygen reserve in the lungs. This technique delays the onset of hypoxemia during the placement of the tracheal tube. To observe the benefits of oxygen through nasal cannula when used as an adjunct during preoxygenation. We enrolled 30 healthy volunteers and conducted a sequence of six preoxygenation tests. These included 3-minute tidal volume breathing and 8 vital capacity breaths, with and without oxygen flowing through the nasal cannula as an adjunct. Subjects were kept at a supine position with a face mask on their faces. Their baseline vitals were measured and end-tidal O2 (ETO2) was recorded at the end of each test. The comfort of each technique was also assessed. When comparing the efficacy of the two preoxygenation methods, we found that the addition of oxygen through the nasal cannula improved the efficacy of preoxygenation with both the 3-minute tidal volume breathing method and the 8 vital capacity method (p < 0.001). The three-minute tidal volume breathing technique had higher end-tidal oxygen when compared to the eight vital capacity breaths. The administration of oxygen through a nasal cannula during preoxygenation improves the efficacy of preoxygenation in healthy volunteers. Tidal volume breathing for three minutes achieves a higher end-tidal oxygen concentration compared to eight vital capacity breaths over one minute.

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

To compare the effect of different amounts of fresh oxygen flow on oxygen reserve in patients undergoing general anesthesia. 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. 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). 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.

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

PurposeThere 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).MethodsFifty 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.ResultsThe 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).ConclusionIn 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 registrationNCT02590406, 29/10/2015.

Validation of two preoxygenation techniques, 3 min tidal volume breath and eight vital capacity breath techniques in tribal and non-tribal population of Eastern India

Background: Preoxygenation during anesthesia can be done by 3 min tidal volume breath and eight vital capacity breath in 1 min, conventionally. Population of our country is not homogenous. Aims and Objectives: The present study was conducted to validate preoxygenation processes in people of eastern India. Materials and Methods: Total 140 patients of ASA grade I and II, age group 20–50 posted for surgeries under GA were allotted in TV and VC group. Every odd number and even number patient was tested for TV method and VC method, respectively, with a Magill circuit and airtight face mask with 100% oxygen flow at a rate of 10 L/min. Time and number of breaths were noted when end tidal oxygen concentration ≥90% in TV and VC group, respectively. Results: In TV method, the mean time (in minute) was 3.10±0.27 and 3.13±0.24 for tribal and non-tribal sub-group (P=0.80); 3.02±0.37 and 3.10±0.27 for tribal and non-tribal male (P=0.57); and 3.18±0.05 and 3.16±0.21 for tribal and non-tribal female (P=0.57). In VC method, mean number of VC breaths was 8.32±0.60 and 8.43±0.74 for tribal and non-tribal sub-group (P=0.76); 8.75±0.49 and 8.23±0.70 for tribal and non-tribal male (P=0.42); and 8.20±0.60 and 8.60±0.72 for tribal and non-tribal female (P=0.16). Patients completing preoxygenation in TV and VC method – tribal: 22% and 53%, non-tribal: 4% and 62%, tribal male: 22% and 20%, non-tribal male: 8% and 68%, tribal female: 0% and 60%, and non-tribal female: 0 and 57%, respectively. Conclusion: No significant difference found between tribal and non-tribal groups of both sexes in each method. Completion of preoxygenation was higher in VC group, though not tested statistically.

Evaluation of High Flow Nasal Oxygenation as a Technique for Preoxygenation in Full Term Pregnant Women

Background and Aims: Obstetric airway guidelines recommend preoxygenation before the induction of general anesthesia to achieve an end tidal oxygen concentration of ≥90%. Recently, high flow nasal oxygenation (HFNO) has been evaluated as a technique for delivering a high concentration of oxygen using high flow rates to patients. We evaluated the use of HFNO as a technique for preoxygenation in full-term pregnant women. Methods: A cross-sectional observational study was conducted on 100 term pregnant women. They underwent preoxygenation using HFNO for 4 minutes (30 L/min for 30 secs followed by 50 L/min for 210 secs) and end tidal oxygen concentration (ETO2) was measured at the end of preoxygenation. The primary outcome was the percentage of women who achieved an expired oxygen concentration of ≥90% for the first expired breath. The secondary outcome was the acceptability and comfort of HFNO as compared to facemask preoxygenation using a 4-point Likert scale. Results: The percentage of women who achieved expired oxygen concentration of ≥90% after 4 minutes of HFNO preoxygenation was 32% [95% confidence interval (CI):22.7-41.3%] with the mean end tidal oxygen (SD) being 86.67 (3.4). 71% [mean (SD): 2.94 (0.92)] found nasal cannula and 56% [mean (SD): 2.67 (1.21)] found facemask comfortable and acceptable for preoxygenation (P value, 0.05). Conclusion: Although HFNO is a comfortable technique, when used for preoxygenation for 4 minutes, it did not achieve an acceptable level of preoxygenation (ETO2 ≥90% in 95% of individuals). Therefore, it is an inadequate technique for preoxygenation in term pregnant women.

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

Journal-related Activities and Other Special Activities at the 2022 American Society of Anesthesiologists Meeting

The application of a surgical face mask over different oxygen delivery devices; a crossover study of measured end-tidal oxygen concentrations

BackgroundThe application of a surgical face mask over oxygen delivery devices is now a widespread recommendation in the setting of the Coronavirus disease pandemic. This addition is designed to reduce droplet spread, but this also changes the nature of these devices, and may alter the amount of oxygen delivered to a patient. This research investigated how placing a surgical face mask over both a simple plastic mask (“Hudson mask”) and nasal cannula altered the concentration of available oxygen measured at the nares.MethodsWe measured the inspired and end-tidal oxygen concentrations of five healthy non-smoking volunteers. Oxygen was delivered via nasal cannula and also a simple plastic face mask, at flow rates of 2, 4, 6 and 8 l per minute, with and without an overlying surgical face mask.ResultsAdding a surgical mask over nasal cannula caused an appreciable rise in the end-tidal oxygen concentrations at all the measured oxygen flow rates 2, 4, 6, 8 L/minute. With the Hudson mask, there was a rise in oxygen concentration at 4 and 6 L/minute. For example, at a flow rate of 4 l/min via nasal cannula, available oxygen concentration increased from 24 to 36%, and via the Hudson mask the concentration rose from 27 to 38%.ConclusionsThe addition of a surgical face mask over both nasal cannula and a Hudson mask resulted in an increased available oxygen concentration. This may be valuable where more advanced oxygen devices are not available, or alternatively providing adequate supplemental oxygen at lower flow rates and thus making critical savings in oxygen usage.

Abstract No. : ABS1297: Evaluation of High flow humidified nasal oxygenation as a technique for preoxygenation in full term pregnant women

Background & Aims:Obstetric airway guidelines recommend preoxygenation before the induction of general anaesthesia to achieve an end tidal oxygen concentration of > 90% .We evaluated the use of high flow humidified nasal oxygenation (HFNO) as a technique for preoxygenation in full term pregnant women.Methods:A cross sectional observational study was conducted in 100 term pregnant women. They underwent preoxygenation using HFNO for 4 minutes (30l/min for 30 seconds 50l/min for 210 secs) and end tidal oxygen concentration was measured at the end of preoxygenation. The primary outcome was the percentage of women who achieved an expired oxygen concentration of >90% for the first expired breath. The secondary outcome was the acceptability and comfort for the HFNO as compared to facemask preoxygenation using 4-point Likert scale. A cross sectional observational study was conducted in 100 term pregnant women. They underwent preoxygenation using HFNO.Results:The percentage of women who achieved expired oxygen concentration of >90% after 4 minutes of HFNO preoxygenation was 32% [ 95% confidence interval (CI):22.7-41.3%] with the mean end tidal oxygen(SD) being 86.67(3.4). 71% [mean (SD): 2.94(0.92)] found nasal cannula and 56% [mean (SD): 2.67(1.21)] found facemask comfortable and acceptable for preoxygenation (P value, 0.05).Conclusion:HFNO is a comfortable technique, but when used for 4minutes preoxygenation, it does not achieve an acceptable level (ETO2 >90% in 95% of individuals). Therefore, it is an inadequate technique for preoxygenation in term pregnant women.TableExpired oxygen concentration(ET02) after 4 minutes of HFNO.VariableMean±SDMedian (25th-75th percentile)95% CI for meanRangeExpired oxygen concentration86.67±3.487 (84-90)85.996-87.34478-91

Effect of high fresh gas flow and pattern of breathing on rapid preoxygenation

Background and Aims:Preoxygenation is supplementation of 100% oxygen prior to induction of general anaesthesia to increase the body’s oxygen stores. Efficacy of preoxygenation can be increased by optimising fresh gas flow (FGF) rate and pattern of breathing.Methods:Based on pattern of breathing—Tidal Volume Breathing (TVB) or Deep Breathing (DB) and FGF-10 L/min or 15 L/min—100 subjects of the American Society of Anesthesiologists physical status I/II posted for elective surgery were recruited and randomised into four groups: T10 - TVB with 10 L/min; D10 - DB with 10 L/min; T15 - TVB with 15 L/min; and D15 - DB with 15 L/min. A tight-fitting anaesthesia mask along with continuous positive airway pressure of 5 cm of H2O with 20° head-up was used for preoxygenation. The total time taken and the total number of breaths required to achieve end tidal oxygen concentration (EtO2) of 90% were noted. Exhaled tidal volume (Vte), end tidal carbon dioxide, fraction of inspired oxygen, and EtO2 were recorded at each breath. Analysis of variance (ANOVA) was used for inferential statistics and Tukey’s honestly significant difference (HSD) test was used to calculate mean difference in total time and number of breaths amongst the groups.Results:Total time taken was significantly low (P < 0.001) in DB compared to TVB (D10: 70.2 ± 19.91, D15: 68.4 ± 20.27 vs T10: 112.28 ± 47.96, T15: 113.6 ± 48.57 seconds). Number of breaths was significantly high (P < 0.001) in TVB with 22.84 ± 8.73, 23.76 ± 11.64, 10.56 ± 3.69, and 8.32 ± 1.8 in T10, T15, D10 and D15, respectively. Vte was significantly low in TVB (P < 0.001).Conclusion:Rapid preoxygenation can be achieved by DB at high FGF of a minimum of 10 L/min.

Investigation of the optimal method of oxygen administration with simultaneous use of a surgical mask: a randomized control study

PurposeFrom the perspective of infection prevention during the Coronavirus disease 2019 (COVID-19) pandemic, a recommendation was made to use surgical masks after extubation in patients in the operating room. For compliance with this recommendation, anesthesiologists need to administer oxygen to the patient with an oxygen mask over the surgical mask. However, no studies have investigated whether this method allows good maintenance of oxygenation in patients. This study aimed to investigate which method of oxygen administration lends itself best to use with a surgical mask in terms of oxygenation.MethodWe administered oxygen to the study subjects using all the following three methods in random order: an oxygen mask over or under a surgical mask and a nasal cannula under the surgical mask. Oxygenation was assessed using the oxygen reserve index (ORi) and end-tidal oxygen concentration (EtO2).ResultThis study included 24 healthy volunteers. ORi values with administration of oxygen were higher in the order of a nasal cannula under the surgical mask, an oxygen mask under the surgical mask, and an oxygen mask over the surgical mask, with median values of 0.50, 0.48, and 0.43, respectively, and statistically significant differences between all groups (P < 0.001). EtO2 values were in the same order as ORi, with median values of 33.0%, 31.0%, and 25%, respectively, and statistically significant differences between all groups (P < 0.001).ConclusionWearing a surgical mask over the nasal cannula during oxygen administration is beneficial for oxygenation and might help prevent aerosol dispersal.

O.3 High-flow humidified nasal oxygen versus facemask oxygen for preoxygenation of pregnant women: A prospective randomised controlled crossover study

Introduction: Airway management guidelines recommend the preoxygenation of obstetric patients to an end-tidal oxygen (etO2) concentration of 90% or more prior to general anaesthesia. A previous study showed that despite a plausible role for high-flow humidified nasal oxygen (HFNO) in this context, only 60% of participants achieved this target after t hree minutes of HFNO. [1] Tan PCF, Millay OJ, Leeton L, Dennis AT. High-flow humidified nasal preoxygenation in pregnant women: a prospective observational study. Br J Anaesth 2019;122:86-91. Google Scholar This was vastly lower than reported rates with face mask (FM) oxygen. We conducted a randomised controlled crossover trial to determine if HFNO is non-inferior to FM oxygen for increasing etO2 concentration after simulated preoxygenation of women in late pregnancy (gestational age ⩾ 36 weeks).

Comparison between oxygen reserve index and end-tidal oxygen concentration for estimation of oxygenation during pre-oxygenation via a tight-fitted face mask: A prospective observational study.

Comparison between oxygen reserve index and end-tidal oxygen concentration for estimation of oxygenation during pre-oxygenation via a tight-fitted face mask: A prospective observational study.

The efficacy of high flow nasal oxygenation for maintaining maternal oxygenation during rapid sequence induction in pregnancy: A prospective randomised clinical trial.

High-flow nasal oxygenation (HFNO) for pre-oxygenation in rapid sequence induction (RSI) has only been assessed in volunteer parturients without intubation. To evaluate the efficacy of HFNO in comparison with the conventional facemask for oxygenation during RSI for caesarean section under general anaesthesia. Operating room in a tertiary hospital. Prospective randomised, controlled study. Thirty-four healthy parturients undergoing general anaesthesia for caesarean section. Parturients were randomly assigned to HFNO or standard facemask (SFM) group. The primary outcome measure was the PaO2 immediately after intubation. Secondary outcomes included lowest saturation throughout the intubation procedure, end-tidal oxygen concentration (EtO2) on commencing ventilation, blood gas analysis (pH, PaCO2), fetal outcomes and intubation-related adverse events. PaO2 in the HFNO group was significantly higher than that in SFM group (441.41 ± 46.73 mmHg versus 328.71 ± 72.80 mmHg, P < 0.0001). The EtO2 concentration in the HFNO group was higher than that in the SFM group (86.71 ± 4.12% versus 76.94 ± 7.74%, P < 0.0001). Compared to baseline, PaCO2 immediately after intubation also increased significantly in both groups (HFNO group: 30.87 ± 2.50 mmHg versus 38.28 ± 3.18 mmHg; SFM group: 29.82 ± 2.57 mmHg versus 38.05 ± 5.76 mmHg, P < 0.0001), but there was no difference in PaCO2 between the two groups. There was no difference in lowest saturation, intubation times, duration of apnoea, pH value or fetal outcomes. Compared with SFM, HFNO provided a higher PaO2 and EtO2 immediately after intubation in parturients. HFNO is safe as a method of oxygenation during RSI in parturients undergoing general anaesthesia for caesarean section. Clinical trial ChiCTR1900023121.

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

BackgroundThe 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). MethodsUsing 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. ResultsTwenty 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. ConclusionFace 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.

Anaesthesia and orphan disease: A patient with neuromyotonia undergoing single lung ventilation.

Anaesthesia and orphan disease: A patient with neuromyotonia undergoing single lung ventilation.