Routine pre-oxygenation using a Hudson mask. A comparison with a conventional pre-oxygenation technique

Compared Efficacy of Four Preoxygenation Methods for Intubation in the ICU: Retrospective Analysis of McGrath Mac Videolaryngoscope Versus Macintosh Laryngoscope (MACMAN) Trial Data

OBJECTIVES

Severe hypoxemia is the most common serious adverse event during endotracheal intubation. Preoxygenation is performed routinely as a preventive measure. The relative efficacy of the various available preoxygenation devices is unclear. Here, our objective was to assess associations between preoxygenation devices and pulse oximetry values during endotracheal intubation.

DESIGN

Post hoc analysis of data from a multicenter randomized controlled superiority trial (McGrath Mac Videolaryngoscope Versus Macintosh Laryngoscope [MACMAN]) comparing videolaryngoscopy to Macintosh laryngoscopy for endotracheal intubation in critical care.

SETTING

Seven French ICUs.

PATIENTS

Three-hundred nineteen of the 371 critically ill adults requiring endotracheal intubation who were included in the MACMAN trial.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Minimal pulse oximetry value during endotracheal intubation was the primary endpoint. We also sought risk factors for pulse oximetry below 90%. Of 319 patients, 157 (49%) had bag-valve-mask, 71 (22%) noninvasive ventilation, 71 (22%) non-rebreathing mask, and 20 (7%) high-flow nasal oxygen for preoxygenation. Factors independently associated with minimal pulse oximetry value were the Simplified Acute Physiology Score II severity score (p = 0.03), baseline pulse oximetry (p < 0.001), baseline PaO2/FIO2 ratio (p = 0.02), and number of laryngoscopies (p = 0.001). The only independent predictors of pulse oximetry less than 90% were baseline pulse oximetry (odds ratio, 0.71; 95% CI, 0.64-0.79; p < 0.001) and preoxygenation device: with bag-valve-mask as the reference, odds ratios were 1.10 (95% CI, 0.25-4.92) with non-rebreathing mask, 0.10 (95% CI, 0.01-0.80) with noninvasive ventilation, and 5.75 (95% CI, 1.15-28.75) with high-flow nasal oxygen.

CONCLUSIONS

Our data suggest that the main determinants of hypoxemia during endotracheal intubation may be related to critical illness severity and to preexisting hypoxemia. The differences across preoxygenation methods suggest that noninvasive ventilation may deserve preference in patients with marked hypoxemia before endotracheal intubation. Ongoing studies will provide further clarification about the optimal preoxygenation method for endotracheal intubation in critically ill patients.

Performance Comparison of Two Anaesthetic Facemasks

When considering anaesthetic masks, the quality of the mask-face seal is a key determinant of performance. This randomised crossover trial utilises expired oxygen concentration to compare the efficacy of two routinely used facemasks. Thirty subjects were randomised to breathe 100% oxygen via either a traditional reusable black rubber mask or the disposable Intersurgical Scented mask for three minutes. This was then repeated using the other mask. To compare the impact of mask design on the quality of the mask-face seal, it was necessary to minimise measures taken by the anaesthetist to correct for a poor seal. To achieve this, the anaesthetist was requested to hold the mask in a manner consistent with an airtight seal, but they were blinded to capnography and reservoir bag movement. Expired oxygen concentration was recorded at 15-second intervals. From the oxygen wash-in curves, the Intersurgical mask consistently outperformed the black rubber mask. At three minutes the Intersurgical mask performed better than the black rubber mask, with mean end-tidal oxygen concentrations of 86.9% vs. 81% respectively; P=0.008. These findings indicate that the soft cuff design of the intersurgical mask provided a better seal than the black rubber facemask.

Capnographic Analysis of Minimum Mandatory Flow Rate for Hudson Face Mask: A Randomized Double-blind Study

BACKGROUND

Oxygen supplementation through Hudson type face mask is frequently used in perioperative settings. Hudson mask is a variable rate performance device with the risk of rebreathing. Studies using capnography to find out an actual fraction of rebreathing in spontaneously breathing patients are not available.

AIMS

In this study, we analyzed the effects of different flow rates through Hudson mask with capnography on fractional inspired carbon dioxide (FiCO₂).

SETTING AND DESIGNS

Forty patients posted for minor surgeries under monitored anesthesia care were divided into four groups. They received oxygen flow rate of 3 L/min, 4 L/min, 5 L/min, and 6 L/min as per group division, through Hudson mask.

MATERIALS AND METHODS

Parameters such as pulse rate, noninvasive blood pressure, oxygen saturation, respiratory rate (RR), end-tidal carbon dioxide (EtCO₂), and FiCO₂ were noted at baseline. After starting oxygen supplementation, these parameters were monitored every minute for ten minutes. Statistical analysis was done using analysis of variance and Kruskal-Wallis test. Pearson correlation was used to establish a relation between RR and FiCO₂.

RESULTS AND CONCLUSIONS

EtCO₂ and FiCO₂ were comparable in all four groups with no statistical significance. There was strong positive correlation seen between RR and FiCO₂ at a flow rate of 3 L/min while negative correlation in other groups. We conclude that FiCO₂ is similar at all flow rates while breathing through Hudson mask. Increase in RR can cause increase in FiCO₂ at lower flow rate, which is within physiological tolerance limits.

McGRATH MAC videolaryngoscope versus Macintosh laryngoscope for orotracheal intubation in intensive care patients: the randomised multicentre MACMAN trial study protocol

INTRODUCTION

Critically ill patients with acute respiratory, neurological or cardiovascular failure requiring invasive mechanical ventilation are at high risk of difficult intubation and have organ dysfunctions associated with complications of intubation and anaesthesia such as hypotension and hypoxaemia. The complication rate increases with the number of intubation attempts. Videolaryngoscopy improves elective endotracheal intubation. McGRATH MAC is the lightest videolaryngoscope and the most similar to the Macintosh laryngoscope. The primary goal of this trial was to determine whether videolaryngoscopy increased the frequency of successful first-pass intubation in critically ill patients, compared to direct view Macintosh laryngoscopy.

METHODS AND ANALYSIS

MACMAN is a multicentre, open-label, randomised controlled superiority trial. Consecutive patients requiring intubation are randomly allocated to either the McGRATH MAC videolaryngoscope or the Macintosh laryngoscope, with stratification by centre and operator experience. The expected frequency of successful first-pass intubation is 65% in the Macintosh group and 80% in the videolaryngoscope group. With α set at 5%, to achieve 90% power for detecting this difference, 185 patients are needed in each group (370 in all). The primary outcome is the proportion of patients with successful first-pass orotracheal intubation, compared between the two groups using a generalised mixed model to take the stratification factors into account.

ETHICS AND DISSEMINATION

The study project has been approved by the appropriate ethics committee (CPP Ouest 2, # 2014-A00674-43). Informed consent is not required, as both laryngoscopy methods are considered standard care in France; information is provided before study inclusion. If videolaryngoscopy proves superior to Macintosh laryngoscopy, its use will become standard practice, thereby decreasing first-pass intubation failure rates and, potentially, the frequency of intubation-related complications. Thus, patient safety should benefit. Further studies would be warranted to determine whether videolaryngoscopy is also beneficial in the emergency room and for prehospital emergency care.

TRIAL REGISTRATION NUMBER

NCT02413723; Pre-results.

Evaluation of the self-inflating bag-valve-mask and non-rebreather mask as preoxygenation devices in volunteers

OBJECTIVE

To evaluate and compare the effectiveness and tolerability of preoxygenation with the self-inflating bag-valve-mask (BVM) and non-rebreather mask (NRM) as are used before emergency anaesthesia.

DESIGN

Device performance evaluation.

SETTING

Experimental study.

PARTICIPANTS

12 male and 12 female healthy volunteers (age range 24-47) with no history of clinically significant respiratory disease.

INTERVENTIONS

End-expiration oxygen measurements (F(E)O(2)) after 3 min of preoxygenation with BVM (without mechanical assistance) and NRM devices. Mask pressures were measured and subjective difficulty of breathing was also assessed with a visual analogue score (VAS).

PRIMARY AND SECONDARY OUTCOME MEASURES

The final F(E)O(2) achieved was 58.0% (SD 7.3%) for the NRM compared to 53.1% (SD 13.4%) for the BVM (p=0.072). Preoxygenation was associated with small increases in F(E)CO(2) that were greater for the BVM (0.50%; 95% CI 0.48 to 0.52) than the NRM (0.29%; 95% CI 0.31 to 0.28); this difference was statistically significant (p=0.028). Both devices were well tolerated on VAS assessment of difficulty of breathing although this was higher for the BVM than the NRM (median VAS 1.85/10 compared to 1.1/10; p=0.041). Inspiratory and expiratory mask pressures were higher for the BVM.

CONCLUSIONS

In healthy volunteers, the NRM performs comparably to the BVM in terms of the degree of denitrogenation achieved although neither performed well. Although it was well tolerated, the BVM was subjectively more difficult to breathe through and was associated with greater mask pressures and a small increase in F(E)CO(2) consistent with hypoventilation or rebreathing. Our results suggest that preoxygenation with the NRM may be a preferable approach in spontaneously breathing patients.