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What are the anatomic boundaries of the nasal valve? What are two objective way to measure nasal obstruction?

Nasal valve is the narrowest part of the nose but c greatest resistor to produce the most turbulent airflow. It is formed by:

  1. The lower edge of the upper lateral cartilages
  2. The anterior end of the inferior turbinate.
  3. The adjacent nasal septum together c the surrounding soft tissues.

The following are two objective ways to measure nasal obstruction:

Rhinomanometry:

Two measurement are used to calculate Nasal resistance to air flow. These are:

  • Nasal airflow
  • Transnasal pressure

These two parameter are measure by using manometers (differential pressure transducer). This is why the study of nasal resistance to air flow is termed “Rhinomanometry” .

Nasal air flow is

  •  measured by flow head consisting of gauze resistance inside a cone shape tube.
  • Pressure difference across the gauze generated by airflow through tube.

Transnasal pressure:

  • Measured by relating the pressure at posterior nares to that at the entrance of the nostril (atmospheric pressure/ nasal mask pressure)

Active Rhinomanometry

  • Generation of nasal airflow and pressure c normal breathing.
  • Based on the location of the pressure serving tube

1. Anterior rhinomanometry

  • Tube taped to one nasal passage and sealed nasal passage act as an extension of the pressure seming tube to measure pressure in posterior nares.
  • Nasal airflow measured from 1 nostril at a time. Total resistance =sum of bilateral (surgical tape used to seal)
  • Most commonly used

2. Posterior Method

  • Tube held in mouth.
  • Detect post nares pressure when soft palate allow an airway to the mouth.
  • Simultaneous measured of both nasal passage or separately by tapping off one.
  • Disadvantages: Not all patient can obtain an airway around soft palate into mouth.

Passive Rhinomanometry

  • Generation of nasal airflow pressure from an external source (fan/pump) to drive air into the nose direction of an external flow of air through nose out of the mouth.
  • Measures either:
    • driving pressure at the constant flow
    • Measurement of flow at constant pressure
  • Separate upper and lower airways.

Nasal airway resistance can also be measured by heat out body plethysmography (displacement types).

  • Flow head (side of body box )
  • Pressure serving tube passed along the floor of nasal cavity.

R=ΔP/V

R= resistance to airflow in cm H2O/Lit/sec(Pa/cm³)

ΔP=transnasal pressure in cm H2O or Pa

V= nasal airflow in liters/cm³ (does not consider separate components of laminar and turbulent airflow)

x/y plotter shows curvilinear relation for ΔP/V plot

Nasal airflow∝ trans nasal pressure. but higher the pressure ∼limited the airflow due to friction/turbulent airflow.

  1. Universal standard: Unilateral nasal airflow measured at sample pressure point of 150 Pa.

B/L nasal airflow measured at 75 Pa(For Asian 100 and 50 Pa)

Adult: N total resistance= 0.15 -0.39 Pa cm³s³

Infant>Adult

Male>Female

2. Acoustic Rhinometry: Acoustic pulse are generated from a spark source/speaker and the sound pulse is transmitted along a tube into the nose.

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