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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4450_Библиотеки_им_академика_М_И_Перельмана
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and the nasopharynx is measured through a tube that is
fitted airtight to the nostril of the other side (▶ Fig. 2.146).
The subject is examined in a sitting position and is asked to
breathe quietly. The pressure–flow relationship of four to
five breathing cycles is averaged by a computer with a
sample frequency of at least 50 Hz and registered by an XY
recorder. Graphic representation uses the mirror-imaging
technique. Airflow (in cm3/s) is recorded on the ordinate,
the pressure gradient (in Pascal [Pa]) on the abscissa.
Inspiration is shown on the right of the rhinomanogram,
expiration on the left (▶ Fig. 2.147). It is important to follow
the recording online during the testing to check for any
leakage and irregular breathing.
Fig. 2.146Active anterior rhinomanometry. The subject is tested in a sitting position.
The pressure–flow relationship during quiet breathing is measured independently for
both nasal cavities. An airtight mask is fitted over the nose to measure flow through the
side to be tested. A tube is sealed to the nostril of the opposite side to measure the
pressure gradient between the nostril and the nasopharynx of the test side.
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Fig. 2.147Rhinomanogram of a normally functioning nose according to the
internationally accepted standard. XY recording of airflow (cm3/s) and pressure
difference (Pa) of five breathing cycles for the right nasal cavity, as found in a normal
nose. Inspiration on the right, expiration on the left.
According to the international standard, resistance is given
at the fixed pressure difference of 150 Pa. In a normal nose,
the median value for unilateral inspiratory nasal resistance
is 0.36 Pa/cm–3/s (range: 0.34–0.40) in the nondecongested
nose and 0.26 Pa/cm–3/s (range: 0.25–0.30) in the
decongested nose. If necessary, resistance can also be
given at 75 Pa or 100 Pa, but this should be clearly stated.
Total nasal resistance may be calculated from the pressure
values obtained for the left and right nasal cavity according
to the formula:
(2.1)
Active anterior rhinomanometry using a mask has a
number of advantages over other methods: it is well
tolerated and it allows measurement of both nasal cavities
independently; it is a dynamic way of testing nasal
breathing; and it measures nasal flow at different pressures
during active respiration.
To obtain reliable and reproducible results, the following
requirements should be met:
The mask must be wide enough to not deform the nasal
lobule. At the same time, it has to be narrow enough to
be airtight.
The tube by which the pressure gradient is measured
must be attached airtight to the nostril by adhesive
tape without distorting the lobule.
Diagnostic Value of Rhinomanometry
Rhinomanometry is an important diagnostic tool. It
provides objective information about nasal resistance by
determining flow versus pressure gradient. When
performed lege artis, it follows the laws of fluid dynamics
and is by definition correct (▶ Fig. 2.148).
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Fig. 2.148Pressure–flow curve in a patient with a septal deviation on the left;
subnormal pressure–flow curve on the right.
Inspir. Rl = 1.5 Pa/cm–3/s at 150 Pa
Inspir. Rr = 0.6 Pa/cm–3/s at 150 Pa
This objective information, however, does not always
correlate well with the subjective findings of the patient. In
a small percentage of cases, patients may report breathing
difficulties or doctors may find pathology while rhinometric
values are normal. Conversely, rhinomanometry may
produce an abnormal outcome even though the patient has
no complaints (▶ Fig. 2.149).
Fig. 2.149Rhinomanograms without nasal decongestion in a population of 100
individuals. White, normal; orange, borderline pathological; red, pathological. (Clement,
2008.)
Rhinomanometry only provides general information about
nasal resistance in relation to the dynamics of breathing.
As it only records flow and pressure gradient, it does not
give information about the localization of the obstruction.
The only exceptions are cases of alar collapse. Here,
rhinomanometry not only informs us about the location of
the collapse, but also about the pressure at which it occurs
(▶ Fig. 2.150).
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Fig. 2.150Inspiratory collapse of the anterior nasal segment on the left; subnormal
pressure–flow curve on the right.
Inspir. Rl = 0.8 Pa/cm–3/s at 150 Pa and 1.6 Pa/cm3/s at 300 Pa
Inspir. Rr = 0.6 Pa/cm–3/s at 150 Pa and 0.7 Pa/cm–3/s at 300 Pa
Rhinomanometry is not applicable in:
Very young children
Complete unilateral obstruction, and
Patients with a septal perforation
Other Rhinomanometric Techniques
In active posterior rhinomanometry, pressure
measurements are made with a tube posterior to the base
of the tongue while the subject breathes through the nose
with the mouth closed. Since many patients do not tolerate
a tube in the back of the mouth, this is not advised as a
standard method.
In passive rhinomanometry, a fixed amount of air (250 cm3)
is blown through a nasal cavity via a nozzle by external
means, while the subject is holding his or her breath. The
amount of pressure needed is measured. This method does
not represent normal breathing, and differences between
inspiration and expiration are not established.
Anemometry
Anemometry measures temperature changes of inhaled and
exhaled air at the level of the nostril over time, giving a
rough estimate of nasal patency changes over time. It is a
semiquantitative, indirect method that is used mainly in
sleep apnea studies to measure the nasal cycle.
There may be many therapies; there is only one diagnosis.
Objective Nonbreathing Tests
Acoustic Rhinometry
Acoustic rhinometry allows measurement of the crosssectional area and the volume of the nasal cavity. It
provides us with a curve that represents an estimate of the
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cross-sectional area of the nasal cavity as a function of
distance from the nostril. A click is presented to the nasal
cavity through a nose piece that is positioned parallel to
the sagittal plane and at 45° to the coronal plane (▶ Fig.
2.151). The reflected signal is recorded within the range of
0.1 to 10 kHz. The test is performed while the patient is
seated and holding his or her breath.
Fig. 2.151Acoustic rhinometry. The geometry of the nasal cavity is determined by
analyzing the reflection of acoustic clicks presented to the nasal cavity through a
nosepiece.
Two types of nose pieces exist:
1. The conical nose piece is introduced into the vestibule.
As it distorts the vestibule to a certain extent, it is not
recommended when measuring the nasal valve area. In
measuring the effect of nasal challenge; however, this
disadvantage does not cause a problem.
2. The anatomical plateau-shaped nose piece allows a
rather airtight seal with minimal or no distortion of the
ostium externum, especially when applied with some
Vaseline. Its disadvantage is that several models are
needed to fit different sizes and shapes of nostrils
(adults, children etc.).
The normal acoustic rhinometric curve has a characteristic
W-configuration showing two minimal cross-sectional areas
(MCA). The first one, MCA 1, is at about 1.5 cm and
represents the end of the nose piece and its junction with
the nose ([304]). The second one, MCA 2, corresponds with
the valve area (i.e., the nasal valve and the head of the
inferior turbinate), the flow-limiting segment (▶ Fig. 2.152
and ▶ Fig. 2.153). According to the ISCOANA (International
Standardization Committee for the Objective Assessment of
the Upper Airways), only MCA 2 is clinically relevant
because MCA 1 is considered an artifact due to the nose
piece.
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