Sleep apnoea
Anatomy of the upper airway Fig 3
Continued »
apnoea-hypopnoea syndrome (SAHS) in the ı950s. They titled an article published in the American Journal of Medicine in ı956 ‘Extreme obesity associated with alveolar hypoventilation: a Pickwickian syndrome’. This was in homage to Charles Dickens, whose main character Joe (Fig 2) in The Pickwick Papers (ı836) falls asleep in any situation at any time of day. Pickwickian syndrome can still be found in medical dictionaries to this day. In ı964, a study showed that 9ı per cent
of snoring patients had a narrow pharynx, elongated soft palate and uvula. This led in due course to tracheostomy being the first successful treatment – despite serious disadvantages, including recurrent purulent bronchitis and speech difficulties.
Sleep apnoea Pickwickian syndrome is now commonly called obstructive sleep apnoea (OSA) and we should distinguish between the two types – obstructive sleep apnoea and central sleep apnoea (CSA). OSA is the result of the mechanical
collapse of the upper airway, whereas CSA arises from a reduction or lack of brainstem activity regulating the respiratory muscles activity in failing to
send a message to the respiratory muscles to breathe. Each type of apnoea is managed differently.
Where does airway collapse occur? The upper (pharyngeal) airway from the hard palate to the larynx is made up of hard tissues – the hard palate, the maxilla and mandible, the nasal turbinates, the hyoid bone (anteriorly) and cervical vertebrae (posteriorly) and a collapse of the tube in between. The pharynx has
three segments: from top to bottom the nasopharynx, the oropharynx and the hypopharynx. The nasopharynx
connects the nose to the mouth and remains open when surrounding muscles flex so that the person can continue breathing. The salpingopharyngeal fold and tubal tonsils surround it. The soft palate (velum or muscular palate) separates the
nasopharynx from the oropharynx, which extends from the uvula to the level of the hyoid bone. The oropharynx is divided into the retroglossal pharynx (from the soft palate to the epiglottis) and the hypopharynx (from the epiglottis to the larynx). In addition, the area between the retropalatal and retroglossal pharynx is also called the velum (Fig 3).
OSA and bony structures We’ll look now at what bony structures can predispose to OSA. Any abnormalities in the hard tissues such as the mandible, maxilla, hard palate and hyoid bone can contribute to the displacement of the soft structures, such as the
tongue. This, in turn, can lead to airway obstruction. Bony protuberances along the cervical vertebrae can also lead
to airway obstruction. The most common skeletal abnormally likely to lead to OSA is a short mandible. Shiroh Isono et al published in the
Fig 2 Continued » Ireland’s Dental magazine 39
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