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ab
Fig. 25.7 Depiction of anterior masked rhinomanometry.
A full face mask (b) is being used to avoid any distortion
by the nasal alae. The pressure detection for the nasopha-
25.3.4 Nasal Resistance or
Conductance
Resistance at a given point during the cycle of
pressure and ow values can be obtained by
dividing pressure by the corresponding ow at
that point. Conductance is used by some and is
the ratio of ow over pressure, the inverse of
resistance. Typically resistance (or conductance)
values are taken from inspiration, though some
devices also report expiratory values.
Since rhinomanometry measures the simulta-
neous ow and pressure for the entire length of
ryngeal pressure is done with the tube that is sealed to the
left nostril (a)
the nasal airway, it is generally thought that it pri-
marily reects the minimal effective cross-
sectional airway. Figure25.9 shows an example
in which the cross-sectional area of an airway is
smallest posteriorly rather than in the valve area.
In this example, the right valve area has a smaller
cross section than the left valve area, but the cross
sections further posteriorly are smaller still with
the left being the least. In this patient, the left
side, which had the smallest overall cross section,
is the same side that has the higher measured
resistance and the same side where the patient
felt the greatest obstruction.
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Fig. 25.8 Two methods of measuring the nasopharyngeal
pressure in posterior rhinomanometry. The gure on the
left shows the pressure detection tube being held in the
oropharynx with the lips sealed (A) and the patient holding the soft palate open (B). The gure on the right shows
Slice 11
2.00
1.80
1.60
1.40
1.20
) of unilateral nasal
2
1.00
0.80
0.60
0.40
0.20
0.00
airway at given distance (in mm)
Cross-sectional area (in cm
Right
Left
Right 1.10
Left 1.59
Slice 11
020
Flow 150
Slice 37
Slice 37
Right 0.98
Left 0.83
40
Distance into nasal airway from nasal inlet (in mm)
Res 150 Reff lns VR Rvert lns Sx side Sxs subj
526
404
0.29
0.37
the pressure catheter (C) passing along the oor of one of
the nasal passages back to the nasopharynx. The small
dimension of the tube is considered to have negligible
effect on the airow measurement on that side
Slice 60
Right
Left
Slice 82
360.50 left worst
Slice 60
Right 1.01
Left 0.87
60
0.33
0.45
Slice 82
Right 0.71
Left 0.41
80 100 120
0.37 50
Fig. 25.9 The plot of the cross-sectional area of right
(blue) and left (pink) nasal airway as one goes further
back (along the x-axis in mm) in the nasal airway. A 3D
reconstruction was done from high-resolution CT scans,
and successive cross-sectional areas were calculated per-
pendicular to the center vector of airow through the nasal
airway. Note that at the valve area (30mm in) the right-
sided cross-sectional area is smaller, but that (at
80–90 mm) the smallest overall cross-sectional area
occurs posteriorly on the opposite (left) side of the nose
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25.4 Rhinomanometry Has Been
Instrumental
inUnderstanding Elements
ofNasal Physiology
25.4.1 Measuring Changes That
Occur inthePassage ofAir
Through theNose
withGrowth andwithAge
Children have smaller nasal passages and thus
higher average nasal resistance. Nasal resistance
has been shown to decrease as children grow to
adulthood. Interestingly, Thulesius found nasal
resistance to decrease as adults aged [17].
25.4.2 Measuring theNasal Cycle
Unilateral nasal resistance measurements have
been used to document the periodicity of the nasal
cycle. One side of the nose is put at rest as the
other is open and doing the work of humidifying,
warming, and ltering the air. In some patients, it
was found to be fairly regular, and in others, it was
shown to be rather irregular [18, 19].
25.4.4 Quantitating Airway Change
withRecumbency
Hasagawa has used rhinomanometry to demonstrate the signicant increase in nasal resistance
that can occur with recumbency [22]. Just as our
cardiovascular system has to make appreciable
adjustments to maintain the same blood ow to
our brain and extremities when we change to
recumbency, the same regulatory parasympathetic/sympathetic pathways affect the relative
congestion of the nasal tissues, particularly in
certain individuals, resulting in increased nasal
resistance and obstruction in the recumbent
position.
25.4.5 Assessing Nasal Airway
Change withExercise andCO
Studies using rhinomanometry have shown the
opening of the nose with exercise [23].
Measurements of nasal resistance revealed the
increase in nasal obstruction occurring as
increased amounts of CO2 is delivered in the
inspired air [24].
2
25.4.3 Discovering theCause
ofDownside Obstruction
When Lying onOne’s Side (or
withPressure Application
inYoga)
When asked why the downside of the nose
becomes more obstructed when lying on one’s
side, many will say it is due to “gravity.”
Rhinomanometry was used to demonstrate that
this is not the case. Haight [20, 21] mapped the
pressure receptors on the side of the body that
when activated cause relative congestion of the tissues on that side of the nose. This phenomenon is
also known to Yoga practitioners who apply pressure with a hand placed in the axilla to enhance the
breathing through the opposite nostril.
In the nasal cycle, one side of the nose is put at rest
as the other is open and is doing the work of
humidifying, warming, and ltering the air.
25.4.6 Finding theNormal Range
andAbnormal Range ofNasal
Resistance Values
If nasal resistance is measured in a standardized
fashion for a large group of people, it is possible
to show the distribution of “normal” resistance
values for that population. This has been done for
the sides of the nose as well as the total nose. By
then comparing the nasal resistance of a patient
against this distribution of normal values, one can
determine if the patient has nasal resistance that
is far outside the normal range [25].
25.4.7 Measuring Disturbance
inNasal Respiratory Function
By measuring a large group of patients who complained of the symptom of nasal obstruction, it
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was possible to describe the range of resistance
values that are “abnormal” [26]. The signicance
of an abnormal unilateral resistance value must be
considered in the light of the variation that occurs
with the nasal cycle in the non- decongested nasal
airway. Measuring the unilateral nasal airway after
thorough decongestion can eliminate a major portion of the contribution of the nasal cycle in many
individuals, but it will also change the overall
range of “normal” and “abnormal” values to lower
resistance ranges [25]. The total resistance of the
nasal airway is relatively constant [22] through the
course of the nasal cycle in the non-decongested
nose. Some investigators have therefore suggested
the use of total resistance as a value to measure the
degree of nasal obstruction.
Pressure receptors on the downside of the body
cause the downside nasal airway to have higher
resistance.
25.4.7.1 When Is Disturbance
intheNasal Airstream
Signicant?
If an abnormal value of nasal resistance is measured, is this always of signicance? By “signicance” in patients, we usually mean that they are
experiencing a symptom or condition that warrants treatment. Like an abnormal audiogram, it
is the patient’s choice as to whether any condition
conrmed or found by a test is treated. Like any
test, it is possible to have an abnormal result, but
for a patient not to feel that they have sufcient
symptoms to be treated.
25.4.7.2 Studying theCorrelation
ofElevated Resistance
withtheSymptom ofNasal
Obstruction
There continues to be active debate about whether
objective measurements of the nasal airway correlate with the symptom of nasal obstruction
[27–33]. There has also been interesting work
about the sensation of nasal obstruction being
related to cold receptors that are stimulated by
menthol- like compounds [34]. If there is more
resistance to airow, then is it the narrower airway causing less ow and thus less cold receptor
stimulation that causes the sensation of
obstruction?
Elevated values of nasal resistance have been
shown to correlate with the symptom of nasal
obstruction [26, 35, 36]. Several studies have
looked at which parameter derived from the
pressure- ow curve data obtained by rhinomanometry would best correlate with symptoms.
Two studies [35, 37] found the maximal resistance during normal respiration to be a parameter
that correlated with symptoms better than other
parameters. Phillip Cole (personal communication) explained this best, noting that the greatest
time during the respiratory cycle (Fig.25.1) was
spent at the extremes of the pressure and ow
curves; thus, it would follow that a parameter
from this location would have the greatest correlation with patient’s symptoms.
In general, recumbency increases nasal resistance.
The variability of the nasal cycle and “subjective” symptoms introduces some noise in demonstrating this correlation. It is most easily shown for
larger values of unilateral obstruction and in
patients who are experiencing symptoms (as
opposed to studies on patients who had no symptoms of nasal obstruction). When studies have
been done looking for a correlation with the sensation of obstruction in subjects who are not experiencing obstruction, there is more “noise”
(variation) making the correlation less clear [38].
Most subjects with nasal obstruction are able to
distinguish the side with the higher resistance and
to give a grading of their obstruction that correlates with other patients who are experiencing
obstruction of their nose [35]. This ability to perceive the side of the highest resistance has been
quantitated and found to be best when there is
more than a slight difference in resistance between
the sides of the nose at the time of the test [39].
25.4.7.3 Providing Objective
Assessment When Crusting
andDysfunction ofNasal
Lining Occur
DuetoDisturbance
intheAirstream
When considering the symptoms of nasal obstruction, the question arises as to whether a patient can
have a nasal airway that is too open and a corresponding measure of nasal resistance that is too low.
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While this is not a common scenario in the measurement of nasal resistance, patients with noses
that appear widely patent, dry, and crusty can be
shown to have lower resistance. This would suggest
that a surgeon’s goal of lowering resistance when
treating the nasal airway needs to be tempered in
this case by maintaining the normal physiologic
range of nasal resistance for the unilateral and total
nasal airways. This is consistent with the avoidance
of disrupting nasal physiology by such procedures
as the total removal of turbinate tissues.
Another interesting application of rhinomanometry that can be applied in this context
is the measurement of nasal resistance in a
patient who complains of symptoms suggesting the type of nasal dysfunction found in
patients with the “empty nose syndrome”, but
in whom the exam looks reasonable. Normal
measured nasal resistance in this context would
support looking for other explanations for the
patients’ symptoms.
25.4.8 Studying theAirow
inConditions ofVarying
Temperature andHumidity
Rhinomanometry has shown that nasal resistance
increases when a patient breathes colder than
normal air [23].
By measuring nasal resistance, studies have
looked for whether breathing air of different
humidities resulted in any change in amount of
nasal obstruction. Ivarsson and Malm found no
signicant difference in breathing air of different
percent humidities [40].
Exercise resulting in a higher pulse rate decreases
nasal resistance.
ogy that would account for the symptoms.
Furthermore, some patients who have only
minimal symptoms have what appears to be
dramatic anatomic obstruction. It is in these
cases that objective testing can be particularly
helpful in being the “tiebreaker.” In the rst
example, if airway testing demonstrates a signicant nasal restriction, it agrees with the
patient’s complaints and makes us look further
for the cause. If the airway testing shows a
widely patent airway, it supports our exam
observations and cautions that a procedure to
increase the dimension of the airway to try to
help this patient’s feeling of obstruction would
be ill advised.
This use of the test results relies on the
knowledge that there is a correlation between
measured airway restriction and the symptom of
nasal obstruction for many patients, giving us an
objective basis for comparison to use with the
patient who seems to have contradictory ndings. Further clinical examples have been
described [41].
25.5.2 For Assessment ofSurgical
Candidate’s Chances
ofOptimal Outcome
Studies have been done showing the value of rhinomanometric results in optimizing the selection
of patients who will be helped by nasal airway
surgery [42, 43].
25.5.3 To Analyze Changes
inPatients Who Do Not Have
Symptomatic Improvement
withSurgery
25.5 Clinical Applications
ofRhinomanometry
25.5.1 When Things Do Not Add
UpDuring Clinical Assessment
We have all been confronted with the cases in
which a patient complains bitterly about nasal
obstruction, but we are not able to see pathol-
We all want to learn from our patients who continue to have symptoms despite our surgical
intervention for their airway. Rhinomanometry,
applied as noted in Sect. 25.5.1, can suggest
whether it is the still unhappy patient’s symptoms
that are exceptional (patients with an unusually
high resistance threshold for comfort) or whether
there is still some measurable obstruction in the
airway.
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25.5.4 Challenge Testing
Some patients may have reactions to airborne
antigens yet have negative skin testing. In these
cases, a more direct method of identifying allergens and degree of allergic response can be done
with challenge testing [44–48]. Rhinomanometry
is done rst. Then the patient inhales the challenging antigen. Subsequent rhinomanometry
can detect signicant change in nasal obstruction
caused by the antigen in an allergic patient.
25.6 Summary/Conclusion
Anterior rhinoscopy or endoscopic examination of
the nasal airway alone do not tell us about the
function of the nasal airway. An objective measurement method is needed to have better information. Rhinomanometry may be the answer and it is
the measurement of airow through the nose and
pressure across the nose during breathing. During
inspirations, the curves go downward with a
decrease in pressure and the corresponding movement of air in the direction of the lungs. During
expiration, the curves move upward corresponding
to pressure increasing and causing the movement
of air out of the nose. Dividing the maximum pressure reached during normal inspiration by the
highest ow gives a nasal resistance value that correlates with the symptom of nasal obstruction in
symptomatic patients. It is of paramount importance of understanding nasal physiology. Besides
understanding normal physiology, this objective
test, rhinomanometry, plays a signicant role in
understanding the change of physiology in nasal
disturbances, and after its correction.
Acknowledgment The author is grateful to Prof John
Pallanch for his support for updating this chapter.
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Acoustic Rhinometry
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Abbreviations
AR Acoustic rhinometry
CT Computed tomography
MRI Magnetic resonance imaging
Pearls
• Acoustic rhinometry technique is principally
based on the computation of cross-sectional
area—distance curves from the analysis of the
reected sound waves by the anatomical structures in the nasal cavity.
• Acoustic rhinometry measurements of the
healthy adult nasal cavity are reasonably accurate to the level of the paranasal sinus ostia.
Beyond this point, acoustic rhinometry overestimates cross-sectional areas.
• The nasal valve is identied by a pronounced
minimum (the rst minimum after the nostril)
on the acoustic rhinometry area–distance
E. Hizal
Department of Otorhinolaryngology Head and Neck
Surgery, SBU Gulhane Training and Research
Hospital, Ankara, Turkey
Department of Audiology, SBU Gulhane Faculty of
Health Sciences, Ankara, Türkiye
O. Cakmak (*)
European and International Board Certied on Facial
Plastic Surgery, FACEISTANBUL, Istanbul, Turkey
curve. However, the second, third and fourth
local minima on the acoustic rhinometry area–
distance curve do not correspond to any anatomic structure in the nasal passage. These
three minima are caused by acoustic resonances in the portion of the nasal cavity
beyond the nasal valve.
• Acoustic rhinometry fails to provide quantitative information about paranasal sinus volume, paranasal sinus ostium size, nasal cavity
volume between the nostril and choana and
the effects of decongestion on the volume of
the nasal mucosa. The diagnostic value of this
method is limited with the anterior part of the
nasal cavity.
• Clinical studies that do not take the limitations
of the technique into account may easily lead
to misinterpretations.
26.1 Introduction
Acoustic rhinometry (AR) was introduced as an
objective tool for the assessment of the nasal cavity geometry in 1989 by Hilberg etal. [1]. AR
measurements require minimum patient cooperation and can be performed practically, quickly
and easily. Due to its advantages, the technique is
widely accepted in a short time. Clinical applications of acoustic rhinometry include determination of the localization and degree of an intranasal
anatomic pathology that affects nasal patency,
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
Ö. Ö. Celebi, T. M. Önerci (eds.), Nasal Physiology and Pathophysiology of Nasal Disorders,
https://doi.org/10.1007/978-3-031-12386-3_26
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evaluation of the results of a nasal surgery, such
as septoplasty, turbinate surgery, assessment of
the effects of medications on the nose that are
used systemically or topically and comparison of
different therapeutic methods. Furthermore, AR
gives idea about the reversible component of the
nasal obstruction as the measurements before and
after decongestion of the nose can be compared.
In other terms, AR is potentially useful in the
assessment of the nasal cavity geometry, nasal
patency and results of various medical and surgical therapies. However, complex anatomy of the
nasal cavity, operator mistakes and factors inherent to the AR algorithms and physics may inuence the measurement of the area–distance
function in the nose and lead to systematic errors.
In this chapter, we will try to give some essential
information on AR and attempt to cover important aspects of the technique, especially from the
clinical point of view.
26.2 History
There have been numerous efforts to understand
the nature and functions of the nose throughout
the centuries. First records in written history
describing the nasal cavity can be found in the
Papyrus Ebers of ancient Egypt, because of its
functional importance in mummication process.
Since then, different methods for the examination
of nose have been used. Evolution of the scientic method has given rise to attempts to meet the
need for more quantitative evaluation methods.
In line with this, a simple nasal patency test was
introduced by Zwaardemaker and modied by
Glatzel, in which the size of the vapour condensation on a cold metal plate or mirror caused by
the expired air through one side of the nose was
compared to the other [2]. Evaluation of the
sound during forced expiration (introduced by
Bruck) or humming (introduced by Spiess) was
proposed to give a diagnostic idea about the
occluded side of the nose [3]. Twentieth century
has witnessed brilliant developments which facilitated the use of more quantiable and objective
nasal evaluation tools, such as rhinomanometry
and acoustic rhinometry.
Acoustic waves can be used to determine the
location of objects in different media, i.e. gases
(air), liquids (water) or solids (earth’s crust).
Indeed, some animals, such as bats, whales or
dolphins, are using sound for object detection for
millions of years. The use of sound for object
detection in water was rst documented by
Leonardo Da Vinci, who proposed inserting a
tube into water and place an ear to the tube in
order to detect vessels [4]. Evolution of the scientic method within decades and development of
physical and mathematical techniques have led to
the development of acoustics as a science and
physical properties of the sound have started to
be illuminated. Accumulation of scientic data in
turn gave rise to innovative thoughts and technological applications of the knowledge on acoustics have started to emerge. One of those
applications was SONAR (sound navigation and
ranging) systems which have been used for
detecting submarines in World War I.Acoustic
waves have also been used for object detection in
solids, i.e. seismic surveys that aimed to investigate underground structures in the earth’s crust.
Through the use of electronics and development
of modern computer systems, sound measurement and analysis reached new levels of complexity and accuracy. Acoustic reections have
been used to assess the geometry of upper airways, including pharynx, glottis, trachea and
lungs after the 1970s. Acoustic rhinometry was
then rst introduced by Hilberg etal. in 1989 [1].
26.3 Theoretical Background
andCriticism
The basic idea behind the acoustic rhinometry
method is similar with other methods of acoustic
object location and consists of impacting an incident acoustic wave into a medium to generate a
reected acoustic wave. The size and the location
of an object through the route of acoustic waves
can be determined by calculation of the amplitude
of reected waves and the time difference between
the incident and reected waves, respectively.
However, some phenomena related with the inherent nature of acoustic waves and acoustic proper-
26 Acoustic Rhinometry
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ties of the medium in which the wave propagates
interfere with the measurements and make calculations complicated. Acoustic waves are longitudinal waves that oscillate along the same direction as
they move. During their route, they exhibit some
characteristic patterns, like reection and diffraction. Reection can be dened as the change in
direction of the wave at an interface between two
different media. Diffraction is, in general, bending
of the waves around small obstacles and scattering
of waves past small ostia. Similar effects occur
when sound waves travel through a medium with
varying acoustic impedance. As the waves propagate within a medium (gas, liquid or solid), they
are reected by structures or dissimilar media on
their route. But some of the waves penetrate
through those structures or media and continue to
propagate. The waves that remain on their route
will be reected again by other structures or dissimilar media. Additional reections, thus, will be
added to the acoustic image and analysis and comparison of the waves that are sent into and reected
back from a heterogeneous or irregular medium
will become almost impossible. A solution to this
problem, i.e. analysis of the acoustic image with
multiple backward reections, was offered by
Ware and Aki in 1969 [5]. By the Ware–Aki algorithm it was then possible to analyse the sound
waves that were reected by different layers
through the route of the wave. Ware–Aki algorithm, which is used in acoustic rhinometry technique however, has some assumptions regarding
the ideal properties of airway. This algorithm
assumes that the sound waves are plane waves, and
it does not account for losses (airway wall nonrigidity, viscous losses) or non- planar wave propagation effects [6–8]. In order to understand the
reasons of some artefacts and errors on acoustic
rhinometry area–distance curves, these assumptions will be explained briey.
The rst reconstruction algorithm used in
acoustic reectometry was developed under the
ideal conditions of no losses in the propagating
wave and that all frequencies were covered by the
acoustic pulse. The assumption of planar wave
propagation is fundamental to passage area measurements made with AR.Waves are assumed to
propagate along the axis of the airway in one
dimension. If the frequency of the sound waves is
high and therefore the wavelengths are too short,
sound waves do not move along a plane and start
to be reected between the walls of the nasal cavity. This, in turn, causes additional delays in the
reected waves, complicates the relation between
incident and reected waves and eventually affects
cross-sectional area and distance computations. In
other words, planar wave assumption determines
and limits the spatial resolution and the frequency
bandwidth of the method, and imposes limitations
on the transverse sizes of an airway model [6–8].
Spatial resolution is dened as the smallest
axial distance that separates two cross-sectional
areas that can still be resolved by AR. In rigidwalled airways, the spatial resolution is approximately equal to one-sixth of the shortest
wavelength of the incident sound pulse. The frequency bandwidth of the incident sound pulse is
important in determining the spatial resolution of
the technique, and hence has a major inuence on
the accuracy of AR measurements. The limited
frequency bandwidth of the AR technique may
increase the rise distance, and thereby produce a
smoother incline in the area–distance curve [6, 9].
The Ware–Aki algorithm is valid under the
condition that the acoustic impedance of the onedimensional acoustic pathway is continuous. If
there is a nite sudden jump in the acoustic
impedance, the transformations and the potential
functions used in the mathematical formulation
of this algorithm are not well dened. In other
words, the Ware–Aki algorithm is not suitable for
calculating the area–distance function at locations where there are abrupt changes in the acoustic impedance [6–9].
It has been argued that any form of energy loss
or sound wave attenuation would reduce the
amplitude of the reected wave, which, in turn,
would lead to area underestimation. Viscous
forces, transmission losses and internal losses
that take place as the sound wave is transmitted
through the constriction in an airway model have
all been attributed to area underestimations that
occur with AR.However, the main reason of area
underestimations distal to an anterior constriction
seems to be a “barrier effect”, i.e. “barrier” created by the anterior constriction reects most of
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