Clinical methods for studying the olfactory function of the nose. Set of odorants for olfactometry Set of odorants registration certificate

Rationale. Measuring the strength of smell makes it possible to judge the qualitative or quantitative impairment of the sense of smell and to evaluate the various effects of various nasal diseases on it. This is especially important before performing rhinological operations and assessing their results, for diagnosing perceptual disorders of smell, during professional selection, and medical examination, since an undiagnosed disturbance of smell is often determined in patients with nasal diseases.

Identifying existing hypo- or anosmia makes it possible to avoid claims that these disorders were caused by the operation.

Depending on what information is needed, specific tests can be performed to determine different aspects of the olfactory system. For rhinology, quantitative assessment of the sense of smell is important, since hypo- and anosmia are common symptoms in diseases of the nose, such as allergic rhinitis or chronic rhinosinusitis, due to impaired smell conduction. It is much more difficult to measure qualitative disorders, the so-called dysosmia (parosmia, cacosmia).

Target. The study of the function of the olfactory analyzer can be used to diagnose perceptual disorders of smell, before performing rhinological operations and to evaluate their results.

Indications. Evaluation of the results of therapy, diagnosis of perceptual disorders of smell and pathology of the anterior cranial fossa, assessment of professional suitability.

Methodology. Subjective methods typically include screening tests and sensation threshold measurements to quantify hypo- and anosmia. Qualitative type methods: odor identification tests and discrimination assessment. The study of olfaction includes preparation, delivery of an odorous substance to the olfactory zone and assessment of the reaction of the olfactory analyzer. Subjective examination methods are often used in practice because they can be carried out easily and quickly on a patient who is able to answer questions. Over the past 10 years, several certified screening methods for examining the sense of smell have been developed around the world, which can be carried out by both the doctor and the patient at home. To get a general idea of ​​the many different olfactory research methods, they can be divided into three categories.

Olfactory screening methods are designed in such a way that they can only determine whether a patient has a smell disorder or not. In clinical practice, subjective methods are most often used. The simplest method of research is to use a set of odorous substances.
It is necessary to have a standard set of 4-6 odorous substances in sealed bottles. It is necessary to examine each nostril separately to determine whether the disorder is unilateral or bilateral (lateralized screening). In children, the study is carried out with turundas moistened with various odorants, the smell of which is familiar to the subject. Starting with the lowest concentration, vessels with an odorous substance are brought to the patient one by one at a distance of 1 cm from the half of the nose being examined. After one normal breath, the subject must answer whether he smelled the smell and describe it.

The dilution of an odorous substance at which the patient perceived the odor characterizes the odor perception threshold, and the dilution that allows the odor to be recognized or characterized is the odor recognition threshold. Depending on the ability of the olfactory analyzer to recognize different odors, 4 degrees of hyposmia are distinguished: 1st degree (weak odor) - 0.5% acetic acid solution; 2nd degree (medium smell) - pure wine alcohol; 3rd degree (strong odor) - valerian tincture; 4th degree (very strong odor) - ammonia.

Quantitative tests (odorimetry) of olfactory function assess the smell threshold for certain odors (the lowest concentration of an odorant that can be detected by the person being tested at the moment), measuring the degree of impairment in the perception of odors. The recognition threshold (the concentration of an odorous substance, which allows not only to feel, but also to recognize the smell) will be slightly higher than the threshold of smell. Devices designed to determine these thresholds are called olfactometers.

There are two main methods of olfactometry: direct and indirect. In the direct method, the amount of odorant required to produce an olfactory sensation is measured. With the indirect method, quantitative indicators of the intensity of the stimulus are determined, for example, the time of perception of the odor, the concentration of the odorous substance in the solution, etc. There are two main types of olfactometers: with active inhalation, when the patient draws in air through the olives inserted into the nose, which first passes through the vessel, where it is saturated with an odorous substance (indications in this case depend on the strength of sniffing); and with forced injection of an odorous mixture.

In practical conditions, a quantitative study of olfaction is usually carried out using a large set of odorants, when solutions of various concentrations are prepared from the initial concentration of the odorant, which is taken as one. Along with determining the threshold of smell, in the differential diagnosis of olfactory disorders, a study of the adaptation process in the olfactory analyzer is used - olfactoadaptometry. Fatigue of the olfactory analyzer develops with prolonged continuous irritation by an odorous substance. The time after which the patient ceases to perceive the threshold dose of the odorous mixture determines the adaptation time. After the cessation of exposure to the odorous substance, the activity of the olfactory analyzer is restored. The patient's onset of perception of the previously established threshold dose of an odorous substance determines the readaptation time.

Qualitative olfactory tests are used to assess a wide range of qualitative olfactory impairments and to determine the ability to perceive and distinguish odors. The method of V.I. has found widespread use for qualitative characteristics of the sense of smell. Vojacek, based on the use of substances with odors of increasing strength, irritating mainly olfactory and trigeminal sensitivity. However, this method, even if performed absolutely correctly, has a number of disadvantages, since recognizing odors, even very familiar ones, often turns out to be an insoluble task for many patients. Assessment of the condition of the trigeminal nerve. In addition to olfactory hairs, the nasal mucosa also contains trigeminal nerve endings. They are needed to detect tactile sensations, pain and temperature changes. The use of special odorants with a component that irritates the trigeminal nerve is possible to assess its condition.

Factors influencing the result. It should be noted that the threshold of smell, even in healthy people, is very variable throughout the day and depends on various reasons: emotional state, state of the nasal cavity at a particular moment. The result of the study is also influenced by whether the subject was warned about the nature of the smell, whether he knew it before, therefore, to obtain more accurate data, a quantitative method was proposed.

Alternative Methods. Objective research methods. Registration of various unconditioned reflexes and reactions of the central nervous system after exposure to a stimulus is considered an objective method; it is convenient to use in pediatric practice. The following methods of objective olfactometry exist: registration of reflex phenomena after irritation of receptors (registration of olfactory-pupillary, olfactory-respiratory reflexes, reactions of the cardiovascular system, etc.); registration of bioelectrical activity of the brain after adequate stimulation; direct removal of biopotentials from the olfactory area. Registration of brain biopotentials upon stimulation of the olfactory analyzer is carried out using electroencephalography and an electronic counting device. However, widespread practical use of objective electroencephalographic olfactometry is impossible due to technical difficulties; therefore, subjective olfactometry methods based on the responses of the subject are widely used in clinical practice.

In addition to recording olfactory evoked potentials, objective methods include functional MRI and functional positron emission tomography, which can directly demonstrate functional changes in the central nervous system in response to odor stimulation. Currently, these methods are used only for scientific research, but they have the potential to become part of the standard clinical research.

Taste and smell are independent feelings from each other, but it is often difficult to draw a line between them only on the basis of the patient’s anamnesis and complaints. Since isolated taste disturbances are extremely rare, a simple test can be immediately carried out to rule out such a diagnosis. Taste sensitivity is determined using special solutions, such as: salty, sour, bitter, sweet, which makes it possible to detect the lack of perception of one of them. Loss or disturbance of taste can vary in severity.