Evaluation of the Upper Airway
in Patients with Snoring and OSA
Royal National Throat, Nose & Ear Hospital, London
Edited by Chris Idzikowski, ISBN 978-953-51-0293-9, 202 pages, Publisher: InTech, Chapters published March 14, 2012 under CC BY 3.0 license
Snoring and obstructive sleep apnoea (OSA) both exhibit multilevel upper airway
obstruction. The Importance of evaluating the dynamics of the obstructing upper airway
cannot be emphasised enough. Accurate assessment and evaluation of the upper airway
could potentially lead to improved surgical and non-surgical treatment outcomes. Most of
these patients would have undergone an ambulatory sleep study or a polysomnography
prior to deciding what treatment modality is going to be offered to them. Treatment options
available include nasal continuous positive airway pressure (nCPAP), mandibular
advancement splints (MAS) or surgery. In terms of selecting a treatment option, in cases
where the sleep study has confirmed moderate or severe OSA, nCPAP would be favoured.
In the remainder and the nCPAP failed patients, further evaluation of the upper airway is
useful and necessary. This chapter will not address sleep studies but will discuss various
methods of assessing the upper airway and will include clinical evaluation of the upper
airway during wakefulness and sleep.
2. Clinical examination
This can be quite easily conducted in out patient setting and addresses the patency of the
nasal passage as well as the assessment of different segments of the pharynx. Anterior
rhinoscopy using a simple nasal speculum allows visualisation of the anterior aspect of the
nasal cavity and helps in identifying problems of caudal dislocation of the septum and if the
nasal valve area is compromised. However, a rigid endoscope is more useful in a more
comprehensive evaluation of the nasal passage and will identify problems such as deviated
nasal septum, nasal polyps (fig. 1) and rhinosinusitis. The identification of these
pathological features is important as they may be a cause of failed compliance and efficacy
in the nCPAP patients.
Simple oropharyngeal cavity examination provides the clinician with useful information
and of note would be the size and grading of palatine tonsils, the length of the soft palate
and uvula and more subtle features such as redundant pharyngeal folds. Friedman tongue
position1 and Mallampati2 grading are also utilised by many clinicians in order to select
patients who may be suitable for palatal surgery. For example in patients with Friedman
tongue position 3 or 4 (figs. 2 & 3) palatal surgery is unlikely to be successful. In contrast
Friedman tongue position 1(fig. 4) would yield better results following palatal surgery. One
must however take in to account that as this assessment is done during wakefulness it may not
truly reflect what happens to the upper airway during sleep as there must undoubtedly be
some variation in the muscle tone in the state of wakefulness and different stages of sleep.
Fig. 1. Nasal Polyps
Fig. 2. Friedman tongue position 3
Evaluation of the Upper Airway in Patients with Snoring and OSA
Fig. 3. Friedman tongue position 4
Fig. 4. Friedman tongue position 1
Probably the most useful equipment in assessing the upper airway is the flexible fibreoptic
nasopharyngoscope which is widely available and allows brilliant visualisation of all
aspects of the naso, oro and hypopharynx. Local anaesthesia in the form of a nasal spray can
be used in allowing an easier and tolerable insertion of the scope and the different segments
of the pharynx are carefully assessed. The patient could be asked to simulate a snoring
sound to try and ascertain the level responsible for causing the turbulent airflow resulting in
the snoring sound. Herzog3 has reported a study based on simulating snoring sound in
order to establish a model of grading upper airway obstruction. However, not all patients
can simulate snoring and some may do this with mouth open or closed and these patients
are usually sitting up whilst during sleep patients may be supine, prone or in lateral
positions. In any case the fact that the muscle tone variation in sleep and wakefulness must
also be borne in mind. Another commonly used technique during the flexible endoscopic
assessment is the Mullers4 manoeuvre. This essentially is a reversed Valsalva procedure
which some patients do find difficult to perform. Furthermore, there is subjective variation
in the assessment of the degree of collapse noted in different segments of the pharynx and
thus the reliability of this technique may be questioned.
Xrays of the maxilla and mandible in the form of cephalometry5 may provide useful data of
various parameters and dimensions controlling the upper airway. This can be particularly
useful when the patient is being considered for invasive surgery such as maxillomandibular
advancement or indeed when considering patients for MAS, though for the
latter it is presently used for research purposes only. The limitation of this evaluation
technique is that it provides a two dimensional image and that so during wakefulness. It
also exposes the patient to considerable amount of radiation.
In contrast, computed tomography (CT) scanning and magnetic resonance imaging (MRI)
provide more sophisticated imaging and allows objective cross sectional area and
volumetric analysis. 6, 7 They are both more expensive than the cephalometry and the CT
scans would also involve radiation. The MRI is quite noisy but is excellent at delineating soft
tissue margins as well as fat deposition in the parapharyngeal space. For research reasons
cine CT and dynamic MRI studies have been conducted to evaluate the upper airway but it
is not considered to be practical or cost effective for routine use.
4. Acoustic analysis
This form of evaluation is safe in that there is no radiation involved and it is relatively
cheap. It can be performed easily during sleep and at patient’s home and simultaneously
with polysomnography. Multiple night recordings can be carried out and based on sound
frequency spectrum, acoustic analysis can potentially discern simple snoring from OSA.8
Attempts have been made to correlate snoring sound frequency with different levels of
obstruction and comparisons of this technique have been made to others such as drug
induced sedation endoscopy.9
The sensitivity and specificity of this technique has often been questioned and although it
can provide useful screening process, its role in helping with selecting treatment modalities
is somewhat limited.10 The other problems in studies with acoustic analysis are that of
variation of software and the choice of central or fundamental frequency in determining the
site of obstruction.
5. Pressure transducers
Numerous devices have been described which can measure pressure changes in different
segments of the upper airway during an obstructive episode. Different numbers of
transducers can be used to measure pressures at different levels of upper aerodigestive tract
ranging from the nasopharynx to the oesophagus. The transducers are attached to a catheter
which is introduced though the nose in a similar fashion to a nasogastric tube. This device
can be left in-situ during sleep thus allowing an overnight recording.
Evaluation of the Upper Airway in Patients with Snoring and OSA
One of the more recent devices illustrated in figures 5 and 6 and known as Apnea-Graph
AG200 (MRA, Medical UK) seems quite promising in that it is capable of combining
polysomnography data with pressure recording thus providing the clinician with
information regarding the severity of OSA as well as giving some idea regarding the
anatomical obstructive segment in the individual patient. Essentially, it relies on measuring
pressure and airflow simultaneously at different levels in the pharynx. It stores and analyses
the cardio-respiratory data of a patient with simultaneous recording of two different sites in
the upper airway using a micro-pressure and temperature transducer catheter. Tvinnereim11
et al published an encouraging study illustrating the importance of using this pressure
catheter evaluation before embarking on surgical treatment. Singh12 et al also demonstrated
some usefulness of this technique, though they had some reservations about the ability of
this device to accurately detect hypopharyngeal obstruction. They compared the Apnea-
Graph to polysomnography. In addition they assessed correlation in some of these patients
pharyngeal obstruction data to that seen whilst performing drug induced sleep endoscopy
(DISE) and concluded the latter to be superior as it allowed visualisation of the upper
airway and was also more useful in indentifying lateral wall collapse. They also commented
that in their group of patients, some found it difficult to tolerate the catheter for the whole
night and stressed that as the catheter moves during respiration the transducers would also
move thus the accuracy of the levels identified could be questioned. Another point to note is
that this device has fixed transducers on a catheter and has a fixed reference transducer and
does not take in to account that all patients are morphologically different and therefore the
positioning will not be identical in all patients.
Fig. 5. The Apnea-Graph device with its components: a pulsoximeter and the fine bore nasal
catheter with four transducers
Fig. 6. Silver ‘reference’ marker indicating the correct position of the Apnea-Graph catheter
6. Sleep nasendoscopy
Sleep nasendoscopy (SNE) which is also known as drug induced sedation endoscopy (DISE)
was pioneered at our institute.13 The beauty of this technique lies in the fact that it allows a
three dimensional visualisation of the upper airway during sleep albeit drug induced. This
assessment is carried out in an operating theatre setting with the help of an anaesthetist who
provides sedation to the patient and closely monitors the patients cardiovascular and
respiratory parameters. The sedative agents commonly used are midazolam or propofol,
however in some units both the drugs are used.
Drug induced sleep is different from natural physiological sleep but one could argue that
the drug used for sedation has the same effect on the different segments of the pharynx thus
it would allow us to compare the proportionate obstruction caused at each anatomical level
in a similar manner that may exist in natural sleep.
An audit of 2,485 procedures performed over a period of 10 years at our institute has
demonstrated that SNE correlates well with apnoea-hypopnoea index and mean oxygen
desaturation.14 We have also demonstrated the usefulness of SNE in predicting treatment
success in snorers using MAS.15,16 Similarly, SNE has allowed site specific target selection in
surgical patients and improved surgical outcomes in our group of patients undergoing laser
assisted palatoplasty with or without tonsillectomy has been reported.17-19
Sleep nasendoscopy assessment of snoring is useful as it provides evaluation of the upper
airway in the dynamic mode during sleep. However, numerous controversies and debates
have arisen and attempts have been made to address some of these by various authors.
For instance, criticisms made by Marais20, whilst comparing snorers and non-snorers, it was
claimed that snoring was produced during SNE in a large number of the non-snorers and
was not produced in many of the snorers. This was challenged by Berry et al21,
demonstrating in their study using target controlled infusion of propofol during SNE that
all their snorers and non-snorers responded as expected.
Evaluation of the Upper Airway in Patients with Snoring and OSA
Similarly, questions and concerns that arose about test-retest reliability and of inter-rater
reliability of SNE have been elegantly addressed by studies conducted by Rodriguez-Bruno
et al22 and Kezirian et al23 respectively.
Bispectral index monitoring (BIS) has provided an adjunct to the assessment of sleep
nasendoscopy in determining the level of sedation required for snoring assessment.24 BIS
(figs. 7 & 8) monitor is a neurophysiological monitoring device which continually analyses a
patient’s electroencephalogram during sedation and general anaesthesia to assess the level
of consciousness and depth of anaesthesia.
Fig. 7. Four sensor BIS electrode attached on patient’s forehead
Fig. 8. BIS Monitor reading during Sleep Nasendoscopy
The issue of assessing the patient at the correct moment has not previously been addressed
and this indeed is an important point as one has to bear in mind the pharmacology and the
pharmacokinetics of the different drugs used during sedation. If the patient is assessed too
early, the muscle relaxation effect of the drug may be over emphasised and if the patient is
assessed too late then important anatomical aspect of the obstructive episodes may be
missed. Thus the depth of sedation during which the assessment is conducted should be as
close to the levels of depth of natural sleep. Evaluation only occurs as a snap shot of a
patients whole sleep cycle. However, combining it with BIS values of patients undergoing
natural sleep allows a more accurate assessment of sleep disordered breathing.
Finally, a couple of studies have compared awake assessment with SNE in the same group
of patients and advocate that SNE is superior; further highlighting the point that there is
muscle tone variation in control of upper airway during wakefulness and that during
obstructive episodes in sleep. It appeared that hypopharyngeal or laryngeal obstruction
could be missed in up to a third of the patients if the assessment was carried out in the
awake state only.25, 26
In order to attain a successful outcome in treating patients with obstructive upper airway in
snorers and OSA it is crucial to evaluate the upper airway dynamics very carefully. Apart
from its usefulness in research, imaging has a relatively minor role to play in evaluation
except in maxillo-mandibular advancement surgery.
Site specific treatment in these patients is required and therefore techniques that offer
localisation of these anatomical obstructive segments would prove useful. In the author’s
opinion the two techniques that appear to do so are sleep nasendoscopy and the Apnea-
Graph. This view has also been supported by a recent evidence based review article on
assessment of obstruction level and selection of patients for obstructive sleep apnoea
Sleep nasendoscopy appears somewhat superior as it allows visualisation of the upper
airway whereas the Apnea-Graph merely looks at the pressure values and relies on correct
positioning of the transducers. Out-patient clinical examination of the nose and the
oropharynx is of paramount importance as it will help identifying potential nCPAP patients
who may fail this form of therapy if there is an obvious anatomical problem.
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Edited by Dr. Chris Idzikowski
Hard cover, 190 pages
Published online 14, March, 2012
Published in print edition March, 2012
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concentrating on different focus groups, from adults to pregnant women, adolescents, children and
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