Understanding Olfactometry: The Science of Smell Testing

Definition

Set of diagnostic tests used in the field of Otolaryngology to study the sense of smell (recognition of different types of odors and their intensities) and detect possible alterations.

The sense of smell is located inside both nostrils and is perceived as an olfactory sensation (perception of smells) and a thermotactile sensation (pressure differences and temperature changes) through the different nerve endings that converge in the olfactory nasal mucosa.

The study of smell can be aimed at detecting subjective alterations in olfactory perception (through the use of olfactometers, or strips of paper, pulp or bars impregnated with substances that give off odor) or can detect objective alterations in olfactory perception (by means of the use of the electroolfatogram or olfactory evoked potential)

How is the study done?

The study of smell is carried out in the Otorhinolaryngology Units.

A nasal cleansing should be performed before the start of the study.

In subjective studies, the patient remains seated, isolated from noise and in optimal conditions of temperature and humidity. The patient is given to smell samples of substances that give off different types of odor at different concentrations and that are located approximately one centimeter from his nostril; You are asked to breathe in normally and to recognize certain characteristics of the odor, such as: whether or not you identify the odor, its intensity, whether it is perceived as pleasant, irritating, and so on.

In objective studies, different technical devices are used that, connected to electrodes placed on the nasal mucosa, emit electrical stimuli that will provoke different olfactory perceptions in the form of neuroelectric impulses that will be detected and collected by the electrodes themselves for later interpretation. The patient remains lying down during the study.

The smell study can last between 15-30 minutes.

Preparation for the study

The study of smell does not require preparation except for proper prior nasal hygiene.

How it feels during and after the study

The study of smell is painless for the patient.

The patient may momentarily perceive some of the odors used during the procedure as unpleasant.

In objective studies by electroolfatogram and / or evoked potentials, a small transient irritation may appear on the mucosal surface on which the electrodes are applied.

Risks and contraindications of the study

The study of smell has no contraindications except for the presence of lesions in the nasal mucosa.

What is the study done for?

The study of smell makes it possible to detect alterations in the perception of odors of a quantitative nature (increase, decrease or absence of smell for one or more odors) and of a qualitative nature (to identify the odor or odors that the patient does not recognize). It allows to identify if the alteration of smell is located in the olfactory mucosa and / or in the nerve endings responsible for the sense of smell or, on the contrary, has another origin (oropharyngeal, central nervous system, etc.) that should be studied later by using more specific diagnostic tests.

The study of smell is a screaning test that should be expanded with subsequent complementary studies (in the case of detecting alterations in it) until the cause that causes said alterations is identified.