Stertor Health Dictionary

The process in which air passes into and out of the lungs so that the blood can absorb oxygen and give o? carbon dioxide and water. This occurs 18 times a minute in a healthy adult at rest and is called the respiratory rate. An individual breathes more than 25,000 times a day and during this time inhales around 16 kg of air.

Mechanism of respiration For the structure of the respiratory apparatus, see AIR PASSAGES; CHEST; LUNGS. The air passes rhythmically into and out of the air passages, and mixes with the air already in the lungs, these two movements being known as inspiration and expiration. INSPIRATION is due to a muscular e?ort which enlarges the chest, so that the lungs have to expand in order to ?ll up the vacuum that would otherwise be left, the air entering these organs by the air passages. The increase of the chest in size from above downwards is mainly due to the diaphragm, the muscular ?bres of which contract and reduce its domed shape and cause it to descend, pushing down the abdominal organs beneath it. EXPIRATION is an elastic recoil, the diaphragm rising and the ribs sinking into the position that they naturally occupy, when muscular contraction is ?nished. Occasionally, forced expiration may occur, involving powerful muscles of the abdomen and thorax; this is typically seen in forcible coughing.

Nervous control Respiration is usually either an automatic or a REFLEX ACTION, each expiration sending up sensory impulses to the CENTRAL NERVOUS SYSTEM, from which impulses are sent down various other nerves to the muscles that produce inspiration. Several centres govern the rate and force of the breathing, although all are presided over by a chief respiratory centre in the medulla oblongata (see under BRAIN – Divisions). This in turn is controlled by the higher centres in the cerebral hemispheres, so that breathing can be voluntarily stopped or quickened.

Quantity of air The lungs do not completely empty themselves at each expiration and re?ll at each inspiration. With each breath, less than one-tenth of the total air in the lungs passes out and is replaced by the same quantity of fresh air, which mixes with the stale air in the lungs. This renewal, which in quiet breathing amounts to about 500 millilitres, is known as the tidal air. By a special inspiratory e?ort, an individual can draw in about 3,000 millilitres, this amount being known as complemental air. By a special expiratory e?ort, too, after an ordinary breath one can expel much more than the tidal air from the lungs – this extra amount being known as the supplemental or reserve air, and amounting to about 1,300 millilitres. If an individual takes as deep an inspiration as possible and then makes a forced expiration, the amount expired is known as the vital capacity, and amounts to around 4,000 millilitres in a healthy adult male of average size. Figures for women are about 25 per cent lower. The vital capacity varies with size, sex, age and ethnic origin.

Over and above the vital capacity, the lungs contain air which cannot be expelled; this is known as residual air, and amounts to another 1,500 millilitres.

Tests of respiratory e?ciency are used to assess lung function in health and disease. Pulmonary-function tests, as they are known, include spirometry (see SPIROMETER), PEAK FLOW METER (which measures the rate at which a person can expel air from the lungs, thus testing vital capacity and the extent of BRONCHOSPASM), and measurements of the concentration of oxygen and carbon dioxide in the blood. (See also LUNG VOLUMES.)

Abnormal forms of respiration Apart from mere changes in rate and force, respiration is modi?ed in several ways, either involuntarily or voluntarily. SNORING, or stertorous breathing, is due to a ?accid state of the soft palate causing it to vibrate as the air passes into the throat, or simply to sleeping with the mouth open, which has a similar e?ect. COUGH is a series of violent expirations, at each of which the larynx is suddenly opened after the pressure of air in the lungs has risen considerably; its object is to expel some irritating substance from the air passages. SNEEZING is a single sudden expiration, which di?ers from coughing in that the sudden rush of air is directed by the soft palate up into the nose in order to expel some source of irritation from this narrow passage. CHEYNE-STOKES BREATHING is a type of breathing found in persons suffering from stroke, heart disease, and some other conditions, in which death is impending; it consists in an alternate dying away and gradual strengthening of the inspirations. Other disorders of breathing are found in CROUP and in ASTHMA.... respiration

This is usually attributed to vibrations of the soft PALATE, but there is evidence that the main fault lies in the edge of the posterior pillars of the FAUCES which vibrate noisily. Mouth-breathing is necessary for snoring, but not all mouth-breathers snore. The principal cause is blockage of the nose, such as occurs during the course of the common cold or chronic nasal CATARRH; such blockage also occurs in some cases of deviation of the nasal SEPTUM or nasal polypi (see NOSE, DISORDERS OF). In children, mouth-breathing, with resulting snoring, is often due to enlarged TONSILS and adenoids. A further cause of snoring is loss of tone in the soft palate and surrounding tissues due to smoking, overwork, fatigue, obesity, and general poor health. One in eight people are said to snore regularly. The intensity, or loudness, of snoring is in the range of 40–69 decibels. (Pneumatic drills register between 70 and 90 decibels.) Bouts of snoring sometimes alternate with SLEEP APNOEAS.

Treatment therefore consists of the removal of any of these causes of mouth-breathing that may be present. Should this not succeed in preventing snoring, then measures should be taken to prevent the sufferer from sleeping lying on his or her back, as this is a habit strongly conducive to snoring. Simple measures include sleeping with several pillows, so that the head is raised quite considerably when asleep; alternatively, a small pillow may be put under the nape of the neck. If all these measures fail it may be worth trying the traditional method of sewing a hairbrush, or some other hard object such as a stone, into the back of the snorer’s pyjamas. Thus, if they turn on their back, they are quickly awakened. (See also STERTOR.)... snoring