What is rhinomanometry?

Updated: Nov 04, 2019
  • Author: Samuel J Lin, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Rhinomanometry has evolved in recent years as an objective measurement of airway resistance. One of the earliest methods of measuring nasal airflow consisted of moving a pressure cannula along the nasal passage to measure pressure-flow relationships. [21] Active rhinomanometry refers to flow measurement from the respiratory cycle. The 3 types of active rhinomanometry include anterior, postnasal, and posterior rhinomanometry. Passive rhinomanometry uses airflow from an extrinsic source, such as an air pump. [1]

Anterior rhinomanometry measures unilateral airflow. Both nasal passages may be measured separately. [6] Anterior rhinomanometry and acoustic rhinomanometry are among the most common methods of clinical measurement of airflow. [9]

Posterior rhinomanometry, another form of measurement, utilizes a pressure sensor in the mouth. In this method, total flow from both nasal passages can be measured together, or each nasal passage can be measured separately. One disadvantage of posterior rhinomanometry is that not all patients are able to relax the soft palate sufficiently. In addition, an oral pressure sensor may be prone to artifact due to movement in a patient's mouth. [6] A significant number of patients seem to be unable to be studied using rhinomanometry for various reasons.

The use of a facemask during rhinomanometry rather than a nasal cannula may be more accurate, as nasal cannulae may erroneously dilate the nasal airway.

Passive rhinomanometry relies on the production of airflow from an external source. With a constant pressure, the flow is measured from the nasal mask. However, it has been noted that external introduction of airflow causes "reflex-evoked changes of the thickness of nasal mucosa.". [9] Accordingly, this method has found little clinical application.

Anterior rhinomanometry measures the transnasal pressure (see image below), which is the difference in pressure from the naris to the nasopharynx. In this method, a pressure probe is placed at the opening of the nostril not being tested. [9] The nasal passage acts as an extended tube and assumes the airway pressure of the nasopharynx equals the pressure at the naris of the nontested side. Total resistance can then be calculated from 2 unilateral measurements. However, anterior rhinomanometry cannot be used to measure airway resistance in patients with septal perforations.

Anterior rhinomanometry. Illustration by William E Anterior rhinomanometry. Illustration by William E. Walsh, CMI; Northwestern University medical student and certified medical illustrator.

Postnasal rhinomanometry uses a pressure sensor placed along the floor of the nose into the nasopharynx (see image below). A separate pressure transducer is located at the entrance of the nasal cavity. [9] Transnasal pressure differences are then measured.

Postnasal rhinomanometry. Illustration by William Postnasal rhinomanometry. Illustration by William E. Walsh, CMI; Northwestern University medical student and certified medical illustrator.

Posterior rhinomanometry involves placing a pressure sensor transorally into the posterior pharynx (see image below). Pressure differences from the nares to the nasopharynx are then measured. Total resistance is measured directly. In this method, patients must be coached to keep the intraoral tube in place. [6]

Posterior rhinomanometry. Illustration by William Posterior rhinomanometry. Illustration by William E. Walsh, CMI; Northwestern University medical student and certified medical illustrator.

Rhinomanometry yields flow-pressure curves. Laminar flow is based on a linear relationship between flow and pressure. Although airflow increases with increased transnasal pressure, higher pressures may yield more turbulent flow secondary to the effects of airway resistance. Turbulent flow results in a limitation of flow generated despite greater transnasal pressure differences. [9] As nasal obstruction occurs, the amount of flow that can be generated plateaus sooner as a result of turbulence, despite greater pressure changes.


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