The process by which air passes into and out of the lungs to allow the blood to take up oxygen and dispose of carbon dioxide. Breathing is controlled by the respiratory centre in the brainstem. When air is inhaled, the diaphragm contracts and flattens. The intercostal muscles (muscles between the ribs) contract and pull the ribcage upwards and outwards. The resulting increase in chest volume causes the lungs to expand, and the reduced pressure draws air into the lungs. When air is exhaled, the chest muscles and diaphragm relax, causing the ribcage to sink and the lungs to contract, squeezing air out.
In normal, quiet breathing, only about a 10th of the air in the lungs passes out to be replaced by the same amount of fresh air (tidal volume). This new air mixes with the stale air (residual volume) already held in the lungs. The normal breathing rate for an adult at rest is 13–17 breaths per minute. (See also respiration.)breathing difficulty Laboured or distressed breathing that includes a change in the rate and depth of breathing or a feeling of breathlessness. Some degree of breathlessness is normal after exercise, particularly in unfit or overweight people. Breathlessness at rest is always abnormal and is usually due to disorders that affect the airways (see asthma), lungs (see pulmonary disease, chronic obstructive), or cardiovascular system (see heart failure). Severe anxiety can result in breathlessness, even when the lungs are normal (see hyperventilation). Damage to the breathing centre in the brainstem due to a stroke or head injury can affect breathing. This may also happen as a side effect of certain drugs. Ventilator assistance is sometimes needed.At high altitudes, the lungs have to work harder in order to provide the body with sufficient oxygen (see mountain sickness). Breathlessness may occur in severe anaemia because abnormal or low levels of the oxygen-carrying pigment haemoglobin means that the lungs need to work harder to supply the body with oxygen. Breathing difficulty that intensifies on exertion may be caused by reduced circulation of blood through the lungs. This may be due to heart failure, pulmonary embolism, or pulmonary hypertension. Breathing difficulty due to air-flow obstruction may be caused by chronic bronchitis, asthma, an allergic reaction, or lung cancer. Breathing difficulty may also be due to inefficient transfer of oxygen from the lungs into the bloodstream. Temporary damage to lung tissue may be due to pneumonia, pneumothorax, pulmonary oedema, or pleural effusion. Permanent lung damage may be due to emphysema. Chest pain (for example, due to a broken rib) that is made worse by chest or lung movement can make normal breathing difficult and painful, as can pleurisy, which is associated with pain in the lower chest and often in the shoulder tip of the affected side.
Abnormalities of the skeletal structure of the thorax (chest), such as severe scoliosis or kyphosis, may cause difficulty in breathing by impairing normal movements of the ribcage.
n. the alternation of active inhalation (or inspiration) of air into the lungs through the mouth or nose with the passive exhalation (or expiration) of the air. During inhalation the *diaphragm and *intercostal muscles contract, which enlarges the chest cavity and draws air into the lungs. Relaxation of these muscles forces air out of the lungs at exhalation. (See illustration.) Breathing is part of *respiration and is sometimes called external respiration. There are many types of breathing in which the rhythm, rate, or character is abnormal. See also apnoea; bronchospasm; Cheyne–Stokes respiration; dyspnoea; stridor.
The reverse of the normal movements of breathing (see RESPIRATION). The chest wall moves in instead of out when breathing in (inspiration), and out instead of in when breathing out (expiration). The spaces between the ribs are indrawn on inspiration – a symptom seen in children with respiratory distress, say, as a result of ASTHMA or lung infections. Patients with CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) often suffer from paradoxical breathing; and trauma to the rib cage, with fractured sternum and ribs, also cause the condition. Treatment is of the underlying cause.... paradoxical breathing
A type of breathing which gets very faint for a short time, then gradually deepens until full inspirations are taken for a few seconds, and then gradually dies away to another quiet period, again increasing in depth after a few seconds and so on in cycles. It is seen in some serious neurological disorders, such as brain tumours and stroke, and also in the case of persons with advanced disease of the heart or kidneys. When well marked it is a sign that death is impending, though milder degrees of it do not carry such a serious implication in elderly patients.... cheyne-stokes breathing
a pattern of breathing seen in complete (or almost complete) airway obstruction. As the patient attempts to breathe, the diaphragm descends, causing the abdomen to lift and the chest to sink. The reverse happens as the diaphragm relaxes. It is almost always associated with use of the *accessory muscles of respiration and drawing in (recession) of the *intercostal muscles of the chest wall.... see-saw breathing
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