Techniques of preoxygenation in patients with ineffective face mask seal

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.

Addition of Nasal Cannula Can Either Impair or Enhance Preoxygenation With a Bag Valve Mask: A Randomized Crossover Design Study Comparing Oxygen Flow Rates

BACKGROUND

A critical safety component of emergency anesthesia is the avoidance of hypoxemia during the apneic phase of a rapid sequence intubation. Preoxygenation with a bag valve mask (BVM) or anesthetic circuit may be improved with supplemental oxygen by nasal cannula (NC) if there is a mask leak. In addition, NC is recommended for apneic oxygenation after induction and may be placed before preoxygenation. However, the optimum NC flow rate for preoxygenation or whether the presence of NC alone creates a mask leak remains unclear.

METHODS

We performed a randomized crossover study on healthy volunteers comparing BVM alone and BVM with NC flow rates of 0 (NC-0), 5 (NC-5), 10 (NC-10), and 15 (NC-15) liters per minute (lpm). Our primary outcome was end-tidal oxygen (ETO2) after 3-minute preoxygenation.

RESULTS

There was no difference in ETO2 between NC-15, NC-10, or BVM-only at 3 minutes. NC-0 and NC-5 recorded significantly lower ETO2 at all times compared with NC-15, NC-10, or BVM-only (least difference NC-5, -7% [95% confidence interval {CI}, -4% to -10%), NC-0, 16% [95% CI, 13%-19%]). There was a difference in ETO2 between NC-15 and BVM-only at 1 minute (7%; 95% CI, 5%-9%), but not at 2 or 3 minutes. There was no difference in ETO2 between NC-10 and NC-15.

CONCLUSIONS

Our study found that NC at 0 and 5 lpm with a BVM is deleterious to preoxygenation and should be avoided. In addition, a lack of difference between NC-10 and BVM-only demonstrates that NC at flows of at least 10 lpm should not impair the preoxygenation process. While NC-15 may offer a benefit by reaching maximal ETO2 at 1 minute, this would need to be balanced against patient comfort.

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.

The utility of noninvasive nasal positive pressure ventilators for optimizing oxygenation during rapid sequence intubation

OBJECTIVES

The objective of the study is to investigate the feasibility of noninvasive nasal positive pressure ventilation (NINPPV) for optimizing oxygenation during the rapid sequence intubation in critically ill patients.

METHODS

A prospective, observational study was performed in an emergency department. Noninvasive nasal positive pressure ventilation was applied in the preoxygenation step and maintained until successful intubation. A pulse oximetry (Spo2) was continuously monitored throughout the procedure and recorded 5 times. The degree of interfering was surveyed with 10-point Likert scale.

RESULTS

Thirty patients were enrolled. The most of enrolled patients were diagnosed as pneumonia, acute heart failure, and traumatic brain injury. The Spo2 was increased to 100% (98%-100%) at the time of starting endotracheal intubation with NINPPV and maintained as 97% (95%-100%) until successful intubation (P< .001). Total apnea duration was 195 seconds (190-196). The degree of interfering intubation was 1 (0-1).

CONCLUSIONS

Noninvasive nasal positive pressure ventilation would be useful for optimizing oxygenation during rapid sequence intubation.