Airway management during sedation for dental treatment in people with intellectual disabilities: a review

Introduction

In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V), developed by the American Psychiatric Association (1), “intellectual disability” is classified as a “neurodevelopmental disorder” and is one of the so-called “developmental disorders”, and people with intellectual disabilities have impairments in cognitive functioning, such as learning, problem solving and judgment, and/or adaptive functioning, activities of daily life such as communication skills and social participation. Additionally, the intellectual and adaptive deficit begin early in the developmental period, typically before age 18 years for diagnosis. It is estimated that 1% to 2% of the population has an intellectual disability, and there were an estimated 107.6 million people with intellectual disabilities worldwide in 2019 (2). The World Health Organization (WHO) and United Nations International Children’s Emergency Fund (UNICEF) also estimated that, in 2019, 317 million children and young people were affected by health conditions contributing to a developmental disability (includes all categories of developmental disorders, not just neurodevelopmental disorders). Furthermore, they reported that these children encountered barriers to accessing healthcare and experienced lower quality of care than their peers (3).

Oral health is a very important health issue related to chewing, swallowing, nutrition, pronunciation, and overall health. It can be maintained through active oral care support by self and caregivers and others. However, the oral health of people with intellectual disabilities remains poor due to a complex combination of mental, physical and social problems, including low self-management skills and poor support systems (4). As a result, they often require invasive dental treatment. Unfortunately, it is often difficult to obtain cooperation for dental treatment from people with intellectual disabilities, especially those with severe intellectual disabilities, because they do not fully understand the need for dental treatment or may experience high levels of anxiety due to lack of understanding and/or sensory aversions to stimuli present in the dental environment. This often makes the provision of dental care to people with intellectual disabilities extremely difficult and requires some special management techniques.

Behavioral techniques based on cognitive-behavioral therapy are used to manage these individuals (5), but they require adequate preparation and time and are difficult to implement when the individual has acute symptoms or depending on the individual developmental level. In these cases, anesthetic management, such as general anesthesia or sedation, is a very useful technique for people with intellectual disabilities, as it makes it possible to avoid the use of forced physical restraints and helps to ensure the quality of medical care provided. The most appropriate method of anesthesia for dental treatment depends on the duration of treatment, type of treatment, patient background, and other case factors, but in some cases, sedation may be more appropriate than general anesthesia. For example, dental procedures often require multiple treatments, and some dental procedures are less invasive, such as brief intraoral examinations or dental procedures, and the ethics of the regular use of general anesthesia for routine examinations, scaling, and polishing are questionable (6). Therefore, sedation is frequently used during dental treatment for people with intellectual disabilities. However, dental treatment-related sedation of people with intellectual disabilities has different airway management characteristics from dental treatment-related sedation of others or other procedure-related sedation. The objective of this review is to enhance comprehension of the attributes of airway management in dental sedation for people with intellectual disabilities and to properly understand the usefulness of the techniques that have been attempted thus far to ensure safer and more secure airway management for this population. The ultimate goal is to provide them with safe and secure medical care and improve their health outcomes.

Characteristics of sedation for people with intellectual disabilities and dental treatment (Table 1)

Required sedation level

Sedation is a very effective management technique for general dental patients, and is generally used to remove more tension and anxiety for patients who are fearful of dental treatment. For safety reasons, minimal sedation or conscious sedation is preferred in these cases. But in dental treatment for people with intellectual disabilities, sedation have to be more challenging due to the patients’ intellectual disabilities. Because sedation for people with intellectual disabilities is performed as part of behavioral control aimed at preventing inappropriate behavior during dental treatment, such as getting up, removing medical equipment, etc., people with intellectual disabilities often have to be managed with “deep sedation”, which suppresses consciousness. Deep sedation is defined as an induced state of decreased consciousness in which the patient cannot be easily aroused, but is able to respond deliberately to repetitive or painful stimuli. As a result, spontaneous ventilation may be inadequate and/or it may not be possible for the airway to be independently maintained (7). Therefore, some airway intervention, such as airway monitoring, securing the airway by raising the chin, administering oxygen, etc., may be required to assist in maintaining a patent airway during such sedation.

Drug interactions

People with intellectual disabilities merely are not only impaired in intellectual activities; they also often have health problems that can affect anesthesia management in addition to their disabilities. One such problem is epilepsy. A very high percentage of people with intellectual disabilities have epilepsy as a complication. Previous studies have reported that the frequency of epilepsy in institutionalized patients ranges from 30–60% (8-11), and the prevalence of epilepsy in people with intellectual disabilities was estimated to be about 25% (12). Patients with epilepsy usually regularly take antiepileptic drugs.

Some people with intellectual disabilities may also exhibit aggressive behavior, in which case psychotropic medications are often used to manage their behavior. Although studies have been conducted in somewhat biased populations such as group homes, previous studies have reported that the percentage of people with intellectual disabilities taking antipsychotic medications was around 30% (13-16). Because the pharmacologic action of such antiepileptic and antipsychotic drugs is central nervous system inhibition, similar to that of sedatives, they interact with sedatives through various mechanisms and may potentiate their anesthetic effects and further deepening the level of sedation (17-19).

Conversely, drug interactions may weaken the effects of sedatives. It is well known that the typical antiepileptic drugs carbamazepine and phenytoin induce the expression of the drug-metabolizing enzyme CYP3A4 (20), which is the major metabolizing enzyme of benzodiazepines. Therefore, midazolam metabolism is enhanced in patients taking carbamazepine and/or phenytoin, and hence, the sedative effect of midazolam may be attenuated in patients taking these drugs (21,22).

Obesity

Obesity is now a global health problem, but it is a health problem of even greater concern for people with intellectual disabilities. Obesity rates have consistently been shown to be higher in adults with intellectual disabilities than in the general population (23). In a previous study, the crude prevalence rates of obesity and overweightedness in adults with intellectual disabilities were reported to be 20.7% and 28.0%, respectively (24). Other studies have shown higher rates of obesity [body mass index (BMI) ≥30 kg/m²] and morbid obesity (BMI ≥40 kg/m²) among adults with intellectual disabilities (age: 18 years or older) than in the general population, with prevalence rates of obesity of 38.3% versus 28% and prevalence rates of morbid obesity of 7.4% versus 4.2%, respectively (25). Various factors, including behavioral, environmental, and biological factors, contribute to the high prevalence of obesity among people with intellectual disabilities. Risk factors for obesity in people with intellectual disabilities include females and people that have less severe disabilities, live independently, are subject to less supervision, have Down syndrome, take medications that cause weight gain, engage in less moderate physical activity, or drink greater amounts of soda (24,25).

In relation to anesthesia management, obesity affects anatomical and physiological characteristics that are risk factors for severe airway obstruction and/or rapid oxygen desaturation (26), and several studies have shown that desaturation is the most common adverse event during sedation in obese patients (27-29). Moreover, these conditions are more severe during deep sedation, which inhibits respiratory function.

Characteristics of airway management during dental sedation

In humans, an inherent biological defense response acts to maintain the airway. When upper airway obstruction occurs during sleep, the respiratory center senses a reduction in ventilation and stabilizes ventilation by prolonging the inspiratory cycle (inspiratory effort), and the chemoreceptor and baroreceptor reflexes caused by hypoventilation-induced hypercarbia activate the muscles that open the upper airway through neuro-muscular compensatory responses. Thus, the upper airway-opening muscles are activated in order to ameliorate upper airway obstruction (30-32). However, during sedation these biological defense responses are suppressed due to decreased or absent levels of consciousness. In addition, the suppression of neuro-muscular compensatory responses decreases the muscle activity of the upper airway-opening muscles, and hence, upper airway patency becomes dependent on the morphological and anatomical characteristics of the upper airway. During conscious sedation, upper airway patency is maintained because the balance between the upper airway lumen and anatomical factors, such as the tongue, surrounding tissues, mandibular position, and bone structure, as well as muscle activity and the neuromuscular compensatory responses of the upper airway-opening muscles are preserved, although they are affected more than during wakefulness. On the other hand, during deep sedation the central and peripheral muscle-relaxing effects of anesthetics significantly suppress the muscle activity and neuro-muscular compensatory responses of the upper airway-opening muscles. Therefore, if the upper airway lumen is relatively narrow due to micrognathia, an enlarged tongue, obesity, or enlarged palatine tonsils, upper airway obstruction is more likely to occur (33). Furthermore, body position is also a factor, with the supine position, forward cervical bending, and an open mouth likely to inhibit upper airway patency (34-37).

Dental procedures involve several factors that make airway management during sedation difficult. In dental treatment, patients are forced to open their mouths and are placed in the supine position, and these inhibit upper airway patency as above. Moreover, dental procedures are performed in the oral cavity, and the oral cavity constitutes part of the airway. This means that the treatment site and airway overlap, and dental treatment is a major impediment to airway clearance during sedation. In addition, water is sprayed intraorally during tooth drilling, which is a major obstacle to airway management during sedation. Thus, airway management during sedation in dentistry poses significant risks and requires meticulous attention and assisting techniques.

New techniques for airway management during sedation in dentistry

Due to the above factors, sedation during dental procedures for people with intellectual disabilities poses unique challenges. The following techniques have been proposed to address airway management during these encounters.

Capnography

The monitoring of respiratory status during sedation is mainly carried out based on visual observations by the sedation administrator. However, this method is very uncertain and is highly dependent on the skill and experience of the sedation administrator. Another method of assessing respiration is pulse oximetry. This measures the amount of oxygen carried by hemoglobin in arterial blood and displays it as a percentage of oxygen saturation. Thus, during sedation, airway complications, such as partial or complete airway obstruction, reduce oxygen uptake and the oxyhemoglobin concentration, which can be detected as a reduction in oxygen saturation. However, it takes at least 20 to 30 seconds after airway obstruction for such changes in oxygen saturation to occur. Furthermore, if oxygen is administered the time between airway obstruction and the reduction in oxygen saturation will be longer.

Recent advances in medical equipment have made it possible to measure the expiratory partial pressure of carbon dioxide (ETCO₂) by capnography, even when the patient is not intubated, and to monitor the patient’s respiratory status using such equipment. Monitoring the ETCO₂ during sedation has been shown to facilitate the detection of respiratory depression and airway obstruction and to prevent hypoxia, and many guidelines strongly recommend monitoring the ETCO₂ during sedation (38-43). Cacho et al. showed that pulse oximetry only detected 11 of the 29 episodes (38%) of disordered respiration detected by capnography, and the mean delay exhibited by pulse oximetry was 38.6 seconds. Thus, they concluded that capnography is a more reliable method than pulse oximetry for detecting respiratory depression early (44). However, although sedation in dentistry has the characteristics mentioned above (mouth open, use of an intraoral vacuum, etc.), and difficulties in detecting exhalation are to be expected, capnography has been demonstrated to be useful during deep sedation for people with intellectual disabilities (45). The latter study showed that the use of capnography during deep sedation for dental treatment has the potential to significantly prevent the occurrence of hypoxia and is a highly recommended respiratory monitoring technique for sedation in dentistry, as in other areas.

Currently, there are two types of capnographic systems, side stream and mainstream. In side stream capnography, the CO₂ sensor is placed away from the airway, and a sample of air is aspirated from the patient’s airway via a sampling tube and pumped to the main unit. In mainstream capnography devices, the sample cell is placed directly in the patient’s airway. In the sample cell, an infrared sensor is attached to an adapter, which emits infrared light to a photodetector on the other side of the adapter. Light reaching the photodetector is used to measure the ETCO₂. This technique eliminates the need for gas sampling and produces a clear waveform that reflects the ETCO₂ in the patient’s airway in real time (46). The mainstream method is considered superior for detecting the ETCO₂ in non-intubated patients (47,48). However, mainstream systems can interfere with dental treatment because the CO₂ sensor is located near the nasal cavity. Dental treatment in the anterior maxillary region is particularly difficult when such CO₂ sensors are used.

Nasal high-flow (NHF) systems

NHF systems are oxygen delivery devices that are capable of delivering high-flow oxygen (up to 60 L/min) through a special nasal cannula. In addition, the absolute humidity of the gas and the fraction of inspired oxygen (FiO₂) can be adjusted (up to 1.0). The use of NHF systems is rapidly becoming a popular oxygen therapy option for the management of hypoxemic acute respiratory failure, and many clinical benefits have been reported (49-51). The possible mechanisms underlying these benefits are (I) the washout of the nasopharyngeal dead space by the high oxygen flow; (II) a reduction in the amount of work required for breathing; and (III) the provision of a degree of positive airway pressure (52).

Recently, NHF systems have been applied to respiratory management during sedation, and some studies showed that the use of such systems prevented hypoxia during sedation (53-55). During sedation, the anatomy of the upper airway may be the dominant factor governing upper airway collapsibility because the neural mechanisms that control the compensatory neuromuscular responses are severely impaired as mentioned above. Thus, airway obstruction may be more likely to occur during sedation, leading to decreased oxygen saturation. The maintenance of positive airway pressure by an NHF system may help to maintain the anatomical form of the upper airway (56). However, dental treatment is always performed with the mouth open, and an intraoral vacuum is used to suction away water sprayed into the mouth. The pressure produced by NHF systems differs between open- and closed-mouth conditions and has been shown to be lower in the open state (57-59). However, NHF systems have also been shown to be useful during sedation for dental treatment. Three clinical studies evaluating the usefulness of NHF systems during sedation for dental treatment have been reported. These studies suggested that NHF systems prevent hypoxia during dental sedation in adult patients (60), children (61), and obese patients with intellectual disabilities (62). In our study of obese patients with intellectual disabilities (62), we compared an NHF system (40% O₂, 37 ℃, and 40 L/min) with a conventional nasal cannula (5 L/min), and based on the results (lower arterial oxygen and carbon dioxide partial pressures were seen in the NHF group), we speculated that NHF systems generate positive airway pressure and ameliorate upper airway obstructions and reduction in the functional residual capacity caused by obesity. In addition, we also speculated that NHF systems reduced upper airway resistance and improved ventilation. A recent meta-analysis concluded that the use of NHF systems during procedural sedation can prevent hypoxemia (63), but not all studies that evaluated the usefulness of NHF during sedation have shown benefits from its use (64-67), and the effectiveness of NHF systems may be affected by the procedure, patient background factors, the NHF settings, and other factors, so further research is needed. In addition, NHF systems require special circuits and devices and have high running costs; therefore, the cost-benefit ratio should also be considered.

Respiratory sound monitoring

Confirmation of respiration and breath sounds by visual and auscultation is the most basic way to monitor respiration, but it is not easy to perform these measurements during dental procedures because the chest is often covered by clothing or coverings. Currently, breath sounds can be measured by a device as part of breath monitoring. The Masimo Rainbow Acoustic Respiration Rate device^TM (RRa monitor) can objectively monitor breath sounds. The RRa monitor is a new monitor that uses an adhesive respiratory acoustic sensor (RAS) worn on the neck to detect the acoustic signals generated by upper airway turbulence during inspiration and expiration. The signal-processing algorithm converts the detected acoustic pattern into respiratory cycles and calculates the respiratory rate. The RRa monitor non-invasively and continuously assesses a patient’s respiration and, together with the measurement of oxygen saturation (SpO₂), has the advantage of being able to simultaneously monitor ventilation and oxygenation.

Studies in a post-anesthesia care unit showed that the data obtained via the continuous assessment of the respiratory rate with the RRa monitor correlated well with those obtained with capnometry in extubated patients (68), and that the RRa monitor was more accurate and more sensitive at detecting pauses in ventilation than the capnometer (69). Also, in gastrointestinal endoscopy procedures performed under sedation, the RRa monitor was reported to be more accurate at assessing the respiratory rate and better at detecting apnea than impedance pneumography or capnometry (70). However, dental treatment frequently requires noisy equipment, and it is necessary to consider the effects of such noise on the RRa monitor.

Several studies have reported on the usefulness of the RRa monitor during sedation for dental treatment. Ouchi et al. (71) recorded the respiratory rate of spontaneous breathing during intravenous anesthesia without intubation in dental patients using the RRa monitor and capnography, and reported that the RRa monitor was superior at determining the respiratory rate. However, they noted that the RRa monitor may not accurately detect the respiratory rate when a dental air turbine is used. Similarly, Kim et al. (72) examined the influence of ultrasonic scaling on the detection of the respiratory rate using the RRa monitor during dental sedation and reported that the percentage of values missing from the data collected by the RRa monitor were 5.62%, 8.03%, and 23.95% in the preparation, sedation, and scaling periods, indicating an increased percentage of missing values in the scaling period. Therefore, they warned that using the RRa monitor alone for respiratory monitoring during ultrasonic scaling may be unsafe.

As stated above, the RRa monitor is a non-invasive and easy-to-use tool for measuring the continuous respiratory rate and is particularly good at detecting apnea. However, in environments where excessive noise may occur, such as during dental treatment, it should be used with consideration for the potential for missing data and should be used in conjunction with other respiratory monitors.

Conclusions

In the dental treatment of people with intellectual disabilities, sedation eliminates the need for physical restraints and allows for the provision of high-quality dental care to people with intellectual disabilities. However, sedation for people with intellectual disabilities requires strict airway management during its implementation because deep sedation is required for behavioral management, drug interactions between patients’ regular medications and anesthetics may make the depth of sedation deeper, and the prevalence rate of obesity is high among people with intellectual disabilities. Dental treatment usually involves patients being in the supine position with their mouths open, which make airway management during sedation more difficult. In the airway management of such sedation during dental treatment for people with intellectual disabilities, the use of capnography, NHF systems, and acoustic respiration monitors may increase patient safety. However, research in this area is still insufficient, both qualitatively and quantitatively, and further research is required.

Acknowledgments

Funding: None.

Footnote

Peer Review File: Available at https://joma.amegroups.com/article/view/10.21037/joma-24-17/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://joma.amegroups.com/article/view/10.21037/joma-24-17/coif). T.M. is the President of the Japanese Dental Society of Anesthesiology. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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