Contents

1. Overview
2. The Grip
3. Optimising Bag-mask ventilation (BMV)

Overview

Methods of Oxygenation:

• Bag-mask
• LMA
• ETT
• Surgical Airway
• Other (jet ventilation and high flow)

The 3-axis model:

1. Oral axis (perpendicular to the bed)
2. Pharyngeal axis (just over 90^o to the oral axis)
3. Laryngeal axis

The aim of the 3 axis model is to highlight that the aperture to view the larynx and ventilate the lungs through an open mouth/nose is difficult unless the 3 axes are aligned. This is achieved through

• Positioning (sniffing the morning air, atlanto-occipital extension and lower c-spine flexion)
• Manoeuvres (jaw thrust, chin lift, head tilt)
• Adjuncts and instruments (laryngoscope, Guedel’s airway)

BMV apparatus:

The BMV apparatus is a self-inflating resuscitation system. Common models found around the hospital are the Ambu^TM(orange bag) and Laerdal^TM (yellow bag).

• PEEP valve: titrate 5-15 cmH₂O, delivers PEEP which improves oxygenation
• Self-inflating bag: adult size is around 2L in capacity, aim to deliver around 6-8 ml/kg tidal volume
• O2 bag: ensure attached to O2 supply and inflated

a) O2 reservoir

b) O2 tubing

c) Self-inflating bag

d) Pop-off valve

e) PEEP valve

f) Mask

g) Cuff to inflate mask

a) Squeeze bag ⅓ with one hand = 500ml, slow and small squeeze over 1-2s, 12 breaths/min

The Grip

The CE Grip

• C-grip (gentle pressure down)
  • Thumb: over the nasal/pointy part of the mask
  • 2nd finger: over the flatter part of the mask
• E-grip (over the bony part of the mandible, not the soft tissue)
  • 3rd finger: at the chin
  • 4th finger: in between along the mandible
  • 5th finger: angle of mandible

Tip: The goal is to bring the patient’s face to the mask, rather than pushing the mask down into the patient (makes the oral-pharyngeal/laryngeal angle less acute).

The Two-handed Grips

Require an assistant to bag

The Double CE Grip

• As above but with both hands
• Use when ventilation is difficult (e.g. elderly, not wearing dentures, obstructions, beard etc)

The Vice Grip

• Thenar eminences over the edges of the mask
• The remaining 4 fingers forming the E grip
• Use when smaller hands, weak grip, rescue bag-mask ventilation

Tip: If there is still a leak, ask an assistant to apply pressure over the area causing the leak.

a & b) One-handed CE grip

c) Double CE grip d) Vice grip

e) Bringing the patient’s face to the mask opens the airway f) Pushing the mask down closes the airway

Optimisation of BMV

1. Size

Fitting the mask

• Pointy part – over the nasal bridge
• Flat part – above the mental prominence (dip in between your bottom lip and chin)

Tip: size the mask to fit in between the above two parts, so it does not hang past the chin.

2. Positioning

‘Sniffing’ position – lower C-spine flexion + atlanto-occipital extension

• The tragus of the ear should be in line with the sternal angle

3. Paralysis

You will notice patients are easier to bag once they become paralysed.

NB: this may be a high risk option as the patient cannot breathe on their own. ONLY PERFORM IF YOU ARE A QUALIFIED AIRWAY PRACTITIONER.

4. Manoeuvres (goal is to align the 3 axis)

Jaw thrust

• Lifts soft tissue structures off the oropharynx, allowing easier passage of air
• 1st and 2nd fingers behind the angle of the mandible, then lift
  • Put the palms of your hands on the cheeks to get a better grip
• NB: painful in the awake patient

Chin lift

• Place finger over the mental prominence (under the chin) and lift up
• Can be used to maintain the jaw thrust more passively

Head tilt

• Place the top of patient’s head in palm of your hand and tilt along the atlanto-occipital axis (like exaggerating the ‘sniffing’ position)
• Aligns the oral and pharyngeal/laryngeal axis
  • Also useful when intubating or inserting LMA
• NB: do not perform on patients with unstable neck injuries (eg trauma, severe rheumatoid arthritis of the neck)

Combination

• Jaw thrust + opening mouth (advanced)

• • Sweep the tongue off the upper palate

a & b) Jaw thrust

c) Chin lift

d) Head tilt – LMA and laryngoscope

5. Adjuncts

Nasopharyngeal

• Use co-phenylcaine spray (mitigate risk of epistaxis and pain) and lubricant
• Sizing: tip of nose -> earlobe (where it sits in the nose)
• Insertion: insert at 90^o angle to the patient
• Caution in patients on anticoagulation, may be contraindicated in head trauma/base of skull fracture

a) Nasopharyngeal airway

Oropharyngeal (Guedel^TM)

• Green, yellow, red (increasing size order)
• Sizing: incisor -> angle of jaw (where it sits inside the mouth)
• Insertion: insert backwards, begin to rotate once halfway in, sweeping the tongue away
  • Tip: If it does not fully fit and is properly sized, try jaw thrust whilst gently pushing the rest in.

Guedel’s airway a) insert backwards, once halfway in slowly turn sideways, then insert the rest

Monitoring ventilation

• Look
  • Symmetrical rise and fall of the chest
  • Paradoxical rise and fall (‘see-saw’ breathing) – indicates obstruction
  • Fogging of the mask
• Auscultate
• Measure
  • etCO2 (can be attached to the BMV apparatus)
  • SpO2 (later sign – due to O2 reserve)

For more information you can view the video on the ABCs of Anaesthesia YouTube page:

Test Yourself

Case 1. An obese, bearded male smoker is undergoing laparoscopic cholecystectomy under general anaesthesia. Whilst awake the optimal sats reached are 95%.

Q1) While the patient is awake, what techniques can be used during pre-oxygenation?

Q2) Pre-oxygenation is complete with ETO2 of >80%, sats of 100%, sedation and paralysis is being given. The patient has a poor oxygen reserve and you want to ensure the patient receives good ventilation prior to intubation. What are some techniques to optimise bag mask ventilation?

Q3) As the paralytic agent kicks in, the patient becomes easier to BMV. The anaesthetist attempts to intubate but is unsuccessful on the 1st pass. What are the immediate next steps?

Potential Answers

A1

• Size the mask: fits over the nasal bridge and under the mental prominence
• Positioning: ‘sniffing’ position
• The Grip: double CE grip (gentle pressure)
• Reduce air leaks
  • Tegaderm around the mouth to reduce air leak (I’ve personally never had to use this)
  • If ongoing air leaks, ask an assistant to apply gentle pressure over air leaks
  • If ongoing issues, beard may need to be shaved

A2

• Manoeuvres: jaw thrust + head tilt
• The Grip: double CE grip -> if not working, vice grip
  • Assistant to help bag the patient
• If not maintaining sats, airway adjuncts: Guedel (large, bearded male) +/- NPA

A3

• A paralysed patient can NOT breathe for themself
• Go back to basics -> continue optimisation of BMV
• Consider an LMA with optimisation
• Retry ETT insertion using BURP, Bougie, new “Blade”/ video laryngoscopy

Congrats, you successfully ventilated the patient whilst they were intubated using video laryngoscopy. A surgical airway was avoided!

By Yannick De Silva

What is the problem?

 Much of the media reports carbon dioxide (CO₂) emissions but fails to address the impact that volatile inhaled anaesthetic gases have on the environment. Desflurane, in particular, is thousands of times more potent than CO₂ and is a significant contributor to greenhouse gas emissions (1). The effects of these emissions ultimately cause higher temperatures for current and future generations. Nitrous oxide (N₂O), a gas that may be combined with volatile gases, contributes to the destruction of the ozone layer (2). This permits more ultraviolet radiation to the earth, making us more susceptible to skin damage and melanoma. Interestingly, more than 95% of the anaesthetic gases used during surgery are exhaled and indirectly vented into the atmosphere (3). This may be following release from a hospital’s anaesthetic gas scavenging system, via leaks in anaesthetic machine valves and manifolds, or through the venting of part-full N₂O gas cylinders once returned to the supplier (4). When used as a combination, desflurane and N₂O have significantly higher global warming potential (GWP) compared to other flurane-N₂O combinations (5). We can liken the CO₂ emissions of these volatile gases to the equivalent emissions from driving for one MAC-hour, with N₂O and desflurane producing CO₂ emissions equating to 95 km and 320 km of driving respectively (6). Furthermore, while desflurane exerts most of its environmental effect over the initial 20 years after use, N₂O has longer-lasting impacts that can span over 100 years following its use (5). This poses obvious threats to our current and future generations.

What are the solutions?

When considering pragmatic solutions, it is important for anaesthetists to make shared decisions with the patient in the pre-operative period, without compromising the quality of care of the patient. Suggested clinical practice responses include:

• Recycle unmetabolised exhaled gas using a closed “circle system” (5)
• Avoid routine use of desflurane and N₂O, e.g. move desflurane vapourisers away (7)
• Consider total intravenous anaesthesia (TIVA) or regional anaesthesia instead (8)
• If gases are used, reduce fresh gas flow especially during maintenance phase (9)

Anaesthesia providers have a duty and responsibility to advocate for systems change in their workplace and the broader medical community (5). Through a collaborative approach with colleagues, gas suppliers, hospital quality improvement teams, and sustainability officers, anaesthetists can promote environmentally sustainable behaviours (10). Suggested systemic solutions for anaesthetic providers include:

• Foster a perioperative culture that values sustainability (11)
• Contribute to life cycle assessments for anaesthetic drugs (12)
• Lead sustainability audits within their hospitals
• Advocate for infrastructure development in hospitals
• Recommend suitable redesign for proposed renovation of operating theatres
• Design and follow a ‘5R’ approach to minimising anaesthetic waste – reducing, reusing, recycling, rethinking and researching (13)
• Strengthen environmental sustainability principles in continuous professional development courses

Where to from here?

The environmental impacts of desflurane and N₂O, commonly used inhalation anaesthetic agents used during surgery, cannot be underestimated. Specifically, desflurane contributes to greenhouse gas emissions and increases surface temperatures on our planet Earth. N₂O on the other hand, causes destruction of the ozone layer and makes us susceptible to skin damage and melanoma. Anaesthetists can undertake pragmatic clinical practice solutions to make meaningful systems changes. Ultimately, it is the responsibility of our healthcare providers to seed environmentally conscious behaviours amongst their colleagues, communities and networks. It would be interesting to survey whether the environmental impacts of anaesthetic gases feature in the preoperative discussion between anaesthetist and patient. It would also be worthwhile to explore whether other causes of perioperative environmental waste, such as single-use syringes and laryngoscopes, form part of this conversation.

References

1. McGain F. Five ways hospitals can reduce their environmental footprint [Internet]. The Conversation. 2018. Available from: https://theconversation.com/five-ways-hospitals-can-reduce-their-environmental-footprint-90390 (accessed Oct 2022)
2. Sherman JD, Chesebro BB. Inhaled anaesthesia and analgesia contribute to climate change. BMJ. 2022Jun8;
3. Yasny JS, White J. Environmental implications of anesthetic gases. Anesthesia Progress. 2012;59(4):154–8.
4. Seglenieks R, Wong A, Pearson F, McGain F. Discrepancy between procurement and clinical use of nitrous oxide: Waste not, want not. British Journal of Anaesthesia. 2022;128(1).
5. Shelton C, Knagg R, Sondekoppam R, McGain F. Towards zero carbon healthcare: Anaesthesia. BMJ. 2022;
6. Hanna M, Bryson GL. A long way to go: Minimizing the carbon footprint from anesthetic gases. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2019;66(7):838–9.
7. Shelton CL, Sutton R, White SM. Desflurane in modern anaesthetic practice: Walking on thin ice(caps)? British Journal of Anaesthesia. 2020;125(6):852–6.
8. Huang DA. Using a TCI infusion pump with propofol tiva for a rapid sequence intubation – my “preference card” [Internet]. Dr Andrew Huang’s Blog. 2021. Available from: https://drandrewhuang.wordpress.com/2021/02/20/using-a-tci-infusion-pump-with-propofol-tiva-for-a-rapid-sequence-intubation-my-preference-card/ (accessed Oct 2022)

9. Feldman JM. Managing fresh gas flow to reduce environmental contamination. Anesthesia & Analgesia. 2012;114(5):1093–101.
10. Sherman JD, McGain F, Lem M, Mortimer F, Jonas WB, MacNeill AJ. Net zero healthcare: A call for clinician action. BMJ. 2021;
11. McGain F, Muret J, Lawson C, Sherman JD. Environmental sustainability in anaesthesia and critical care. British Journal of Anaesthesia. 2020;125(5):680–92.
12. McGain F, Sheridan N, Wickramarachchi K, Yates S, Chan B, McAlister S. Carbon footprint of general, regional, and combined anesthesia for total knee replacements. Anesthesiology. 2021;135(6):976–91.
13. White SM, Shelton CL, Gelb AW, Lawson C, McGain F, Muret J, et al. Principles of environmentally‐sustainable anaesthesia: A global consensus statement from the World Federation of Societies of Anaesthesiologists. Anaesthesia. 2021;77(2):201–12.