Oxygen and Airway Actions for Medical Emergencies Occurring in Dental Practices

Medical emergencies can occur in dental offices. In fact, nearly 60% of dentists participate in the management of one to three medical emergencies annually.¹ In North America, studies report syncope as the most frequent event witnessed by dentists.² However, fatal emergencies are also possible. As a result of an increase in the number of older patients seeking dental treatment, dentists are faced with managing medically complex cases where significant comorbidities and polypharmacy can increase the frequency of adverse events.³ Dentists should always start by taking a comprehensive medical history and keep in mind that treatment plans may need to be altered or aborted in certain cases. Although the occurrence of life-threatening emergencies is infrequent in our field, adequate preparation and prevention are important to diminish the likelihood of poor outcomes resulting in morbidity or death. In other words, “to be forewarned is to be forearmed”.³

When a medical emergency occurs in your dental office, one of the most significant tasks of your team will be to prevent and/or correct insufficient oxygenation to critical organs.⁴ Consequently, within your planned response, oxygen is the single most important medication you will administer to your patient.^5,6 Therefore, all dental professionals must know how to correctly administer oxygen at therapeutic levels. In this article, we will review indications and contraindications for its use as well as oxygen delivery modalities.

Indications and Contraindications

Respiratory distress and failure, which can lead to hypoxemia or decreased levels of oxygen in the blood, should be treated promptly. However, recent studies show that indiscriminate administration of oxygen may increase morbidity and mortality. Therefore, a normoxic oxygenation strategy should be employed.⁷

In normal physiology, respiration is predominantly affected by levels of carbon dioxide (CO2) in the blood which are detected by peripheral chemoreceptors. Although these chemoreceptors can also detect low arterial oxygen levels (hypoxemia), they are more sensitive to increasing CO2 levels. Consequently, hypercapnia or an increase in CO2 levels, is considered as the main trigger of respiratory drive. However, for patients with chronic hypercapnic conditions like chronic obstructive pulmonary disease (COPD), respiration is pathologically triggered by hypoxemia and high levels of oxygen can lead to respiratory depression.8 Therefore, for these patients, a titrated approach is recommended when providing supplemental oxygen during an emergency.^4,9

For patients who are otherwise healthy, normoxic oxygen saturation targets are usually between 92 to 98%.¹⁰ On the other hand, for patients with chronic hypercapnic conditions, recommended target oxygen saturations are generally between 88 to 92%.⁹ In the dental office, pulse oximetry can be an acceptable non-invasive method to measure oxygen saturation if you are aware of its limitations. Artifact, poor peripheral perfusion, and anemia can be named as some of the causes of inaccuracy of this method. Nonetheless, pulse oximetry is commonly used as an indicator of the patient’s oxygen saturation.

Airway Management

The management of an airway starts with appropriate positioning of the patient to ensure patency. This can be rapidly achieved by using basic airway manoeuvres such as head tilt-chin lift or jaw-thrust to move the tongue and soft palatal tissues away from the posterior wall of the pharynx, which allows the passage of air to the lungs.¹⁰ Oropharyngeal (OPA) and nasopharyngeal (NPA) airways are also available to relieve upper airway obstructions. Readers are invited to seek further training with these devices and manoeuvres.

Oxygen Supply

Dental offices should always be equipped with oxygen cylinders. High-pressure “E” tanks mounted on a wheeled cart (Fig. 1) are often preferred since they allow flexibility and maneuverability. Dental teams should always perform routine checks on their oxygen supply before the start of a clinical day to ensure that empty or depleted tanks are replaced. This avoids unpleasant surprises during emergency situations.

Fig. 1

An “E” cylinder contains approximately 680 litres of oxygen (approximately 2,200 pounds per square inch). This will provide approximately 45 minutes of supplemental oxygen at a maximum flow rate of 12 Litres/minute.
The main valve of the cylinder is connected to a regulator which reduces the high pressure within the tank to a useful range. The remaining pressure within the cylinder can be shown by a gauge attached to the regulator. A flow meter controls the oxygen delivery and can be manually adjusted between 1 and 15 L/min.⁶ This allows us to titrate oxygen delivery to the patient’s needs.

To calculate how long an “E” cylinder will last while providing a continuous flow rate, the following formula can be used:11

DURATION = k * (P – R)
                                   F

Where:
D is the duration in minutes
k is the tank constant in PSI-1 liters-1 (0.28 for an “E” tank)
P is the tank gauge pressure in PSI
R is the Safe Residual Pressure in PSI, typically 200 PSI
F is the Flow in litres per minute

Oxygen Delivery Modalities

Dental offices can be equipped with various oxygen delivery devices and the staff need to be trained to use all of them proficiently (Table 1). To determine which oxygen delivery modality is appropriate, the patient should be examined. For spontaneously ventilating patients who experience hypoxemia, supplemental oxygen can be delivered through commonly used devices such as a nasal cannula, face mask or non-rebreather mask connected to an oxygen cylinder. However, when patients are apneic, positive pressure ventilation is required. In such cases, a bag-valve mask system would be the recommended device.⁴

Table 1: Flow Rate and Percentage of O2 Delivered by Different Devices

Oxygen delivery device	Flow rate (L/min)	Percentage of O2 delivered (%)
Nasal cannula	1-6	25-40
Facemask	6-10	40-60
Non-rebreather facemask	10-15	90-100
Bag-valve-mask (BVM)	12-15	= 100

Nasal Cannula:

Nasal cannula (Fig. 2) consist of a thin tube with 2 prongs that are inserted into the nares to supply oxygen. It is typically used with low oxygen flows (1 to 6 L/min). Flows above 4 L/min may be drying to nares. The actual concentration of oxygen delivered to the patient depends on the flow rate since each inspiration entrains a mixture of ambient room air along with the supplemental oxygen provided by the cylinder. Typically, each variation in flow by 1 L/min yields a 4% change in oxygen concentration of the gas mixture (Fraction of inspired oxygen or FIO2).⁵

Fig. 2

Face Masks:

The face mask (Fig. 3) fits over the mouth and nose of the patient and is held in place by an elastic around the back of the head. The efficacy of this device will be affected by the fit of the mask on the patient’s face. Face masks can deliver a higher concentration of oxygen than a nasal cannula, but they still entrain ambient air with each inspiration. When used with a flow rate of 6-10 L/min, a face mask can supply up to 60% concentration of oxygen.⁵

Fig. 3

Non-rebreather Face Masks:

This device consists of a face mask with an attached reservoir bag and one-way valves which prevent rebreathing of exhaled CO2 or entrainment of room air on inspiration. The presence of the reservoir bag allows for a larger volume of oxygen to be inspired with each breath. Therefore, the non-rebreather face mask (Fig. 4) can provide greater oxygen concentration with higher flows. On average, each increase in flow rate of 1 L/min will give an additional 10% concentration in inspired oxygen. This means that at rates above 10 L/min, nearly 100% oxygen is delivered to the patient.⁵

Fig. 4

Bag-valve-mask Devices:

The bag-valve-mask (BVM), a hand-operated device that comes in different sizes, can deliver positive pressure ventilation when patients are not breathing on their own. It can be used with room air or connected to an oxygen cylinder at high flows to deliver nearly 100% oxygen concentration.⁵ When using a BVM (Fig. 5), standing at 12 o’clock or at the head of the patient is considered the best position.⁶ While the thumb and index of the provider’s non-dominant hand form a “C” and grip the top of the mask to obtain an adequate seal over the patient’s face, the remaining three fingers make an “E” and can be used for a simultaneous head tilt-chin lift to ensure the patency of the airway. The other hand is used to gently squeeze the bag to produce a chest rise of approximately one second.^10,16 For adult patients, one breath should be delivered every five to six
seconds, whereas children require a breath every two to three seconds. If the bag is squeezed aggressively and large volumes of air are delivered to the patient, stomach insufflation and vomiting can occur which could ultimately result in aspiration.⁶

Fig. 5

Although BVM devices can be used by a single provider, it is easier to provide positive pressure ventilation with two trained and experienced rescuers.¹⁰ Literature supports that single rescuers traditionally are unable to obtain adequate mask seals while simultaneously opening the airway and delivering appropriate tidal volumes. Fatigue can also compromise the delivery of adequate tidal volumes.⁵ Therefore, we recommend that providers in dental practices work in teams to improve the quality of their BVM ventilation.

In conclusion, the provision of oxygen using various modalities is an important component of emergency management in the dental office. Dentists should invest time and resources to ensure that their offices have adequate equipment that is checked and maintained routinely. They also need to train their teams to be prepared to use this equipment during potentially life-threatening emergencies. As a result of having set protocols and proper training, the team’s efficiency will in turn increase the likelihood of favorable outcomes.

Oral Health welcomes this original article.

References

1. Muller, M.P., et al., A state-wide survey of medical emergency management in dental practices: incidence of emergencies and training experience. Emerg Med J, 2008. 25(5): p. 296-300.
2. Hutse, I., et al., Syncope in Dental Practices: A Systematic Review on Aetiology and Management. J Evid Based Dent Pract, 2021. 21(3): p. 101581.
3. Malamed, S.F. and D.L. Orr, Medical emergencies in the dental office. Seventh edition. ed. 2015, St. Louis, Missouri: Elsevier/Mosby. xvii, 550 pages.
4. Haas, D.A., Management of medical emergencies in the dental office: conditions in each country, the extent of treatment by the dentist. Anesth Prog, 2006. 53(1): p. 20-4.
5. Moore, P.A., The use of oxygen and airway modalities in dental office medical emergencies. Tex Dent J, 2004. 121(12): p. 1150-5.
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8. West, J.B., Respiratory physiology: the essentials. 2012: Lippincott Williams & Wilkins.
9. Abdo, W.F. and L.M. Heunks, Oxygen-induced hypercapnia in COPD: myths and facts. Crit Care, 2012. 16(5): p. 323.
10. American Heart Association, Advanced cardiovascular life support : provider manual. 2020, [Dallas, TX]: American Heart Association. vii, 202 pages.
11. University, W.M.C.o.C. Oxygen Tank Duration. 2013; Available from: http://www-users.med.cornell.edu/~spon/picu/calc/o2tankd.htm.
12. Mobile Oxygen Cylinder (Size: E) With Regulator, in https://www.homelifecare.com/product/oxygen-tank-size-e/.
13. Nasal Cannula, in https://commons.wikimedia.org/wiki/File:Nasal_cannula.jpg.
14. Face Mask, in https://commons.wikimedia.org/wiki/File:Facemask.JPG.
15. Non-rebreather Face Mask, in https://en.wikipedia.org/wiki/Non-rebreather_mask.
16. American Academy of Pediatrics. and American Heart Association., Pediatric advanced life support : Provider manual. 2016, Dallas, TX: American Heart Association. xiii, 352 pages.
17. Bag-valve-mask Device in https://products.redcross.ca/products/bag-valve-mask.

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About the Author

Dr. Mania Nik Kami completed her DMD at the University of Montreal in 2013. She then practised general dentistry for 8 years in remote communities of Northern Quebec before coming to Toronto to pursue her MSc degree. She is currently in her second year of the Graduate Dental Anaesthesia program at the University of Toronto.