Malodour compounds instruments

Malodour compounds

Our perception of smell starts with chemical substances found in the air, which stimulate the receptor cells of the olfactory bulb. These substances, with different compositions and physicochemical structures, have two properties in common: volatility (the tendency of a liquid to evaporate) and solubility. However, no chemical equation exists for determining whether a substance will trigger a pleasant or unpleasant odour.

In the past, doctors believed that changes in the breath could be symptomatic of certain illness and attempted to identify them according to the unique odour of the patient. Modern breath analysis began in the 1970s, when Linus Pauling (Nobel Prize in chemistry) detected, but did not identify, more than 200 volatile organic compounds (VOCs) which were able to be separated by using gas chromatography techniques. For the first time, what we commonly consider “normal human breath” was shown to be gas with a complex composition.

The 3,000 compounds found in human breath.

Nowadays, we have available modern analytical instruments for identifying and measuring the different compounds exhaled by the human body. However, the use of these instruments is not widespread. The most well-known tests are those designed to detect a bacterium called Helicobacter pylori; a concentration of ethanol and acetaldehyde (known as alcohol tests); and those used to detect nitric oxide in asthma patients. And, one field which is generating a lot of interest from the scientific community the early diagnosis of lung cancer through the study of these exhaled compounds.

In the last 30 years, a diverse range of compounds has been identified, and it has also been confirmed that samples of exhaled air (coming from the same individual) can contain more than 200 VOCs. Some factors can influence the composition of human breath, such as physical condition, diseases, general state of health, the intake of certain foods and medicines, environmental factors and lifestyle. To date, over 3,000 different compounds have been detected in the breath. It is worth noting that the International Association for Breath Research (IABR) has a continuously updated database that documents all of the volatile substances of human and animal origin that have been discovered in different testing centres around the world.

Volatile compounds

Volatile compounds found in exhaled air can be classified into three main groups.

1. Volatile Organic Compounds (VOCs) of systemic origin

This group includes all COVs that circulate in the blood and are able to leave the body, whether via the lungs or by excretion through the salivary glands. The air exhaled from the lungs generally includes diverse types of chemical compounds that can be either organic (hydrocarbons, alcohols, ketones, aldehydes, esters, alkanes etc.), non-organic (nitrous oxide, molecular oxygen, carbon dioxide etc.), and even non-volatile compounds in condensed exhaled air (isoprostanes, cytokines, leukotrienes, hydrogen peroxide etc.). Indirectly, the origin of these compounds can also be external, whether absorbed through the skin as a contaminant, through the ingestion of foods or medicines, or through inhalation. In these cases also, the compounds are metabolised inside the body and excreted via exhalation.

Air leaving the lungs can also contain volatile compounds associated with certain diseases, which can essentially be considered biomarkers. Measuring and identifying these compounds can help to obtain an early diagnosis, and has consequently become a very promising, and quickly expanding, field of research in recent years. The following table shows some examples:

Biomarkers	Associated Diseases
Acetone	Diabetes mellitus and ketonemia
Nitrates and cyanide	“Helicobacter pylori” infection
Hydrogen disulphide and limonene	Liver disease and biliary cirrhosis
Aliphatic acids C2-C5 and methyl mercaptan	Decompensated cirrhosis
Dimethylamine and trimethylamine	Uremia and kidney failure

2. Volatile Organic Compounds (VOCs) of extrasystemic origin

All VOCs of extrasystemic/pulmonary origin that evaporate into the air are included in this group. Air leaving the lungs can be collect volatile compounds from other sources before leaving the mouth or nose. These VOCs may or may not be bacterial in origin, but are generally more connected to necrosis and decomposition. The origin of these compounds varies and can include different organs or areas of the body that come into contact with the route of the exhaled breath, such as the upper respiratory tract, the mouth or the digestive tract.

The most common extrasystemic VOCs that are associated with halitosis are indole and skatole phenols, putrescine and cadaverine proteins, and the hydrocarbon methane. These VOCs are the typical waste products that form as putrefying bacteria digest the protein compounds of the human body, resulting from processes of reduction, deamination or decarboxylation. There is a huge variety of VOCS. In a study in which samples of plaque bacteria (taken from the tongue and saliva) were incubated, more than 85 VOCs were identified, representing seven different groups of chemical compounds.

3. Volatile Sulphur Compounds (VSCs)

Volatile sulphur compounds (VSCs) contain sulphur. They are generally classified as a separate group due to their prevalence in, and relevance to, the analysis of halitosis, and may be systemic or extrasystemic. The most common compounds are hydrogen sulphide (H2S), methyl mercaptan (CH3SH) and dimethyl sulphide (CH3)2S. The analysis of exhaled air using gas chromatography has shown that the first two compounds described are the VSCs responsible for mouth odour in 90% of cases.

These substances form as a result of the decomposition of organic matter or the deterioration of protein compounds, during the metabolisation of methionine and cysteine amino acids. The main intraoral source of these compounds comes from the decomposition caused by the bacteria found in saliva, the gums, back of the tongue and mucous. The back of the tongue is considered the main source of VSCs, both in individuals with or without periodontal disease.

The main bacterial substrates are amino acids that contain sulphur: cysteine, cystine and methionine. These are identified in their free form in saliva, cervical fluid, or as a result of the proteolysis of various proteins found in the saliva. Epithelial cells, resulting from the shedding of epitheliums in the oral cavities, and also leukocytes, are an important source of such substrates. The production and emanation of VSCs apparently depends on a range of factors (approximately 74) such as the type of bacterial flora (greater prevalence of Gram-negative anaerobic bacteria); the physico-chemical conditions (pH alkaline saliva, low or partial oxygen pressure and lowered potential for oxidation reduction); and the overall substrates available in the saliva, cervical fluid and, to a lesser extent, from the diet.

Concept

We talk about halitosis open and accessible way, so that you can understand medical terminology that scientists use.

1. What is halitosis?
2. Physical and social consequences
3. Bad breath through the ages

Causes

The Breath Institute has discovered, on the basis of the latest international research, that there are over 80 possible causes of halitosis.

1. The composition of halitosis (bad breath)
2. Causes of halitosis (bad breath)
2.1 Oral causes
2.2 Respiratory causes
2.3 Digestive causes
2.4 Systemic causes, diet and habits
2.5 Neuropsychological causes

Diagnosis

We identify the most effective clinical methods when diagnosing precisely the halitosis’ origin, so that you can chose the best treatment.

1. Methods of diagnosis
1.1 Self-perception
1.2 Organoleptic tests
1.3 Breath gas measurement
1.4 Laboratory tests
2. Psychological tests
3. Signs and associated symptoms

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