subjective and objective ways of measuring the nasal airway including rhinomanometry,acoustic rhinometry,rhinosteriometry,etc

1. Measurement Of
The Nasal Airway
Presenter:Dr Ravindra Daggupati
Moderator:Dr SN Mukherjee

2. • Measures of nasal obstruction usually involve measurement
of nasal airflow or an assessment of the cross-sectional area
of the airway.
• It includes:
1.objective measurements
 Rhinomanometry
 Acoustic rhinometry
 Rhinosteriometry
 Peak nasal flow
 Nasalance
 Nasal spirometry
2.Subjective measures

3. • Objective measures:
• Rhinomanometry provides a functional measure of the nasal
airway resistance or conductance
• acoustic rhinometry provides an anatomical measurement of
cross-sectional area or nasal volume.

4. 1.RHINOMANOMETRY
• Nasal resistance to airflow is calculated from two
measurements: nasal airflow and transnasal pressure
• Nasal airflow can be measured by means of a flow head that
usually consists of a gauze resistance inside a cone-shaped
tube.
• The pressure difference across the gauze generated by airflow
through the tube is used to measure airflow.

5. • Transnasal pressure can be measured by relating the pressure at the
posterior nares to that at the entrance of the nostril, which will
normally be atmospheric pressure or nasal mask pressure
• It is of two types:
• Active rhinomanometry involves the generation of nasal airflow and
pressure with normal breathing.
• Passive rhinomanometry involves the generation of nasal airflow
and pressure from an external source, such as a fan or pump, to
drive air into the nose.

6. • Active rhinomanometry can be divided
into anterior and posterior methods
according to the location of the pressure-
sensing tube.
• In active anterior rhinomanometry, the
pressure-sensing tube is normally taped to
one nasal passage.
• The sealed nasal passage acts as an
extension of the pressure-sensing tube to
measure pressure in the posterior nares.
• With this method, nasal airflow is
measured from one nostril at a time and
the pressure-sensing tube is moved from
one side of the nose to the other.
• Therefore, the nasal resistance is
determined separately for each nasal
passage

7. • In active posterior
rhinomanometry the pressure-
sensing tube is held in the mouth
and detects the posterior nares
pressure when the soft palate
allows an airway to the mouth.
• Total nasal airflow can be
measured from both nasal
passages simultaneously.
• The right and left nasal airflows
can be measured separately by
taping off one nostril at a time.
• Total nasal resistance can be
determined directly from the
total nasal airflow and transnasal
pressure with this method.

8. • Passive rhinomanometry involves the direction of an external
flow of air through the nose and out of the mouth.
• The method may involve either measurement of a driving
pressure at a constant flow or measurement of the flow at a
constant pressure

9. • Nasal airway resistance can also be measured by use of a
head-out body plethysmograph (displacement type) and, with
this method, the flow head is located on the side of the body-
box and the pressure-sensing tube is passed along the floor of
the nasal cavity.
• This method has the advantage that the nose is unimpeded by
any mask

10. Equipment
• A mask is attached to a device that measures transnasal
pressure and flow and interfaces with a computer.
• For children, a smaller face mask can be used, but the test is
performed in the same way as for adults

11. Technique

20. Reporting Results
• The International Committee on Standardization of Rhinomanometry has
recommended that rhinomanometric values be expressed in
SI units, with
• pressure expressed in pascals (Pa) and
• flow expressed in cm3/sec
(100 Pa = 1.0 cm H2O; 1000 cm3/sec = 1 L/sec).
• Nasal resistance is reported in Pa/cm3/sec
(0.1 Pa/cm3/sec = 1 cm H2O/L/sec)
• Nasal resistance to airflow may be calculated from the following equation:

21. • Unilateral nasal airflow measured at a sample pressure point of 150 Pa
and bilateral nasal airflow measured at 75 Pa are recommended as
universal standards.
• However, the Asian population cannot always achieve these pressures
during normal quiet breathing and the lower sample pressures of 100 and
50 Pa, respectively, are generally accepted for nasal resistance
measurements in Japan.
• Total nasal resistance to airflow can be either determined directly using
the posterior method of rhinomanometry or it can be calculated by
combining the two separate values of nasal resistance for the two nasal
passages as shown in the formula below:

22. Pressure-Flow plot
• The accepted standard for displaying the
pressure-flow curve is to plot pressure on
the x-axis and flow on the y-axis.
• With this arrangement, the greater the
pressure-to-flow ratio (resistance), the
closer the curve is to the pressure axis
• Thus, curves representing a more
obstructed airway lie closer to the
pressure axis.
• Flattening of the curve may represent
limitation of flow from an airway
restriction such as collapse of the valve
area.
• The more obstructed the airway, the
greater the pressure required to generate
a certain flow.

23. Normal values
• In adult subjects free from signs of nasal disease, mean total resistance
has been reported to be around 0.23 Pa cm3/s with a range from 0.15 to
0.39 Pa cm
• Nasal resistance is at a maximum in the infant at around 1.2 Pa cm3/s and
declines to the adult value at around 16–18 years of age and then shows
only a slow decline with increasing age.
• with increasing age,
• 0.6 Pa cm3/s (age 5–12 years) to
• 0.29 Pa cm3/s (age 13–19 years) and
• 0.22 Pa (age>20 years) in males.
• The relationship between and nasal resistance was similar in females but,
inasal resistance was lower in females than males.

24. 2.Acoustic Rhinometry
Equipment
• A hollow plastic tube conducts a sound pulse (“click”) generated by
a trigger module into the nasal cavity.
• An appropriate external nosepiece is placed against the nares, with
care taken not to distort the nasal alae.
• The acoustic wave is reflected from the nose and recorded as digital
impulses by an analog-to-digital converter for computer analysis.
• Calculated area-distance graphs and volumes are generated
onscreen and printed with the use of mathematical algorithms.

25. Technique
• Testing should be performed in a
quiet room, with the patient seated
comfortably.
• The patient’s head may be stabilized
by fixing the gaze on a faraway
object.
• The subject may be requested to
hold their breath, but this is not
mandatory.
• The nosepiece is aligned against the
nares at an angle parallel to the nose
and held gently without causing alar
distortion.
• A seal is facilitated by use of a
surgical lubricant on the tip of the
nosepiece.

26. • The acoustic pulse is then
generated; the nosepiece should
be held still for 10 seconds.
• An appropriate curve is
generated on the computer
screen.
• The procedure is then repeated
on the other side.
• A second set of readings may be
taken 10 minutes after
application of oxymetazoline or
another suitable topical
decongestant.

27. • The graphs before and after decongestant application offer a
way of quantifying both mucosal and structural components
of obstruction.
• The curve generated on the computer from the reflected
sound waves shows an estimated distance in centimeters on
the x-axis and estimated cross sectional areas in square
centimetres on the y-axis. “0” is the nosepiece.
• The distance is commonly measured at 2, 4, and 6 cm; the
results become less accurate after 6 cm.

28. • The minimal cross-sectional
areas (CSAs) usually observed
are CSA1, CSA2, and CSA3.
• CSA1 is usually the nasal valve
area; CSA2 may be located at
the anterior head of the
inferior and/or middle
turbinate,CSA3 (mid-posterior
end of the middle turbinate)
• The graph is usually printed
with results “before” and
“after” decongestion
• The congestion factor may be
calculated and the sides
compared with each other.

29. Interpretation of Results
• Mucosal “congestion” may be measured by calculation of the “congestion
factor.”
• The severity of blockage is calculated by comparison with normative
standards.
• More than 2 standard deviations at each CSA is considered abnormal.
• The congestion factor may be designated as normal, mild, moderate,
severe, or markedly severe.

30. Comparison of Acoustic Rhinometry and
Rhinomanometry
• Rhinomanometry determines nasal patency in terms more
representative of how difficult it is for a person to breathe, and
acoustic rhinometry is preferable to study rapidly changing
mucovascular conditions and nasal volume changes.
• Both methods can give information about a site of obstruction, but
acoustic rhinometry gives more precise anatomic information.
• the assessment of the smallest dimension found by
rhinomanometry is physiologic MCA estimate.
• The smallest dimension determined by acoustic rhinometry the
anatomic MCA estimate

31. 3.Rhinostereometry
• The inferior nasal turbinate exhibits spontaneous congestion
and decongestion associated with the filling and emptying of
the nasal venous sinuses in the nasal epithelium that cause
the tip of the turbinate to move in position by several
millimetres.
• The technique of measuring the position of the inferior
turbinate by means of microscopy is termed
rhinostereometry.
• The subjects head is fixed rigidly by the subject biting onto a
tailor made tooth-splint fixed to the frame of the microscope
stand.

32. • The changes in position of the turbinate can be measured in
millimetres by means of a scale on the eye-piece of the
microscope.
• Studies on the nasal cycle have demonstrated that the
mucosal swelling causes the turbinate to change position by
up to 3.5 mm.
• Rhinostereometry has also been used to measure changes in
the swelling of the inferior nasal turbinate associated with
rhinitis medicamentosa.

33. 4.PEAK NASAL FLOW
• The peak inspiratory or expiratory airflow through the nose
associated with maximal respiratory effort can be used as a
measure of nasal conductance.
• The measurement is effort dependent and is less sensitive
than rhinomanometry or acoustic rhinometry in determining
small changes in conductance.

34. 5.Nasalance
• Nasometry is an objective technique that is used for the
assessment of the nasality of speech.
• It is based on a comparison of the acoustic output from the
nose and the mouth for a given spoken word or phrase
• There is an inverse relationship between nasalance and nasal
airway resistance, and subjects with nasal obstruction will
have a low measure of nasalance, whereas a subject with a
patent nose, especially after decongestion, will have a high
nasalance.

35. 6.Spirometry
• Measurement of the partitioning of nasal airflow can be made
by measuring the volume of air expired from each side of the
nose with a spirometer during a slow vital capacity manoeuvre.
• The partitioning ratio can be expressed on a scale from-
1to+1where0indicatesequalityofairflow through the nasal
passages, -1 left side completely blocked,+1 right side
completely blocked

36. Use of Objective Testing of the
Nasal Airway
• For Patients with Snoring and Sleep Apnea
• For Challenge Testing in Patients with Allergic Rhinitis
• To Assess the Effect of Treatment
• Acoustic rhinometry has shown changes in cross-sectional
area in patients with nasal polyps who are receiving systemic
steroid treatment.
• Nasal airway testing can help in the objective assessment of
the effect of surgery on the airway.
• Documentation of Improvement in Airway Dimensions after
Surgery
• Selection of Patients for Surgery

37. Subjective measures
• nasal sensations of airflow is related to stimulation of
trigeminal cold receptors
• Nasal sensations are important in the study of nasal disease,
as it is the patient’s perception of nasal sensations
(symptoms) that is of primary concern to the patient

38. • Studies on the effects of menthol on
nasal sensation of airflow clearly
demonstrate the lack of any correlation
between objective measures of nasal
airway resistance and subjective
measures of airflow.
• In patients with nasal obstruction
associated with common cold, ingestion
of a menthol lozenge causes a great
improvement in the sensation of nasal
airflow without any change in nasal
airway resistance,
• This is because the menthol vapour
causes an increase in the sensitivity of
cold receptors that detect nasal airflow,
and a perception of nasal decongestion,
without any objective change in nasal
resistance

39. Thank you