Asthma is a disorder of respiration characterized by severe paroxysms of difficult breathing, usually followed by a period of complete relief, with recurrence of the attacks at more or less frequent intervals.
Asthma is an allergic reaction which manifests itself by spasmodic contraction of the smaller bronchial tubes, It is narrowing of the bronchial tubes, often accentuated by swelling of the lining epithelium, that is responsible for the great difficulty in breathing which is the characteristic feature of the condition.
There is a large number of substances to which the asthmatic subject may be hypersensitive, contact with which is responsible for an attack. These include pollens; the emanations of certain animals such as cats, dogs, horses; house dust; certain articles of diet; bacteria; the house dust mite. Fifty per cent of asthmatics in Japan are said to be allergic to butterflies. The discovery of the substance to which the individual is susceptible may sometimes be difficult. Thus, it may be noted that attacks of asthma occur when the patient goes to bed, and it may be found that these occur because he is susceptible to horse hair, with which the pillow is filled.
In other instances the difficulty may be due to the fact that the individual is hypersensitive to more than one substance. In many cases the specific susceptibility of the individual may be enhanced by some non-specific conditions, such as emotional disturbance, worry, indigestion or an infection such as a sore throat or a ‘cold in the head’.
There is another group of asthmatic subject in whom the asthma is due to sensitization to bacteria responsible for some chronic or repeated infection. For instance, an individual who is subject to repeated attacks of tonsillitis, sinusitis, or nasal catarrh may become sensitized to the causative organism, so that whenever he becomes infected with this organism he is liable to develop attacks of asthma.
The reason why asthma does not develop in all such individuals subject to repeated infections, is that such attacks only occur in the individual who has the tendency to develop hypersensitivity. This tendency is usually hereditary, and it will often be found that the asthmatic subjects suffers from other allergic conditions such as hay fever and urticaria (or nettle rash).
Asthma is more common in males than in females, and the first attack usually occurs in childhood.
There is a form of asthma which may not develop until later in life. This occurs in individuals who suffer from chronic bronchitis. A certain proportion of these people ultimately become sensitized to the organisms responsible for their chronic bronchitis and this sensitization may not develop until middle age.
The onset of an attack of asthma is usually sudden, although there may exist certain premonitory symptomswhich warn the sufferer of its approach, such as a feeling of discomfort, drowsiness, irritability and depression of spirits. The period when the asthmatic paroxysm comes on is generally during the night, or rather in the early hours of morning. The patient the awakes in a state of great anxiety and alarm, with a sense of weight and tightness across the chest which he feels himself unable to expand with freedom.
Respiration is performed with great difficulty, and is accompanied by wheezing noises. His distress rapidly increases, and he can no longer retain the recumbent position, but gets up, and sits or stands with his shoulder raised, his head thrown back, and his whole body heaving with his desperate efforts to breathe. His countenance is pale or livid, and wet with perspiration while his extremities are cold; his pulse is rapid, and may be irregular or intermitting.
All his clothing must be loose about him; he cannot bear to be touched, and the very presence of others around him seems to aggravate his distress. His one desire is to breathe fresh air; and he will place himself by an open window and sit for hours in the middle of the night, unmindful of the exposure. The paroxysm, after continuing for a variable length of time, often, often extending over may hours, begins to abate, the breathing becomes easier, and the subsidence of the attack is often marked by the occurrence of coughing with expectoration.
After the cessation of the attack the patient appears to be, and feels, comparatively well. In cases of long standing, however, the subject of asthma comes to bear permanent evidence of its effects. He is easily put out of breath on exertion and he requires to lie with his head elevated, circumstances to be ascribed to organic changes in the chest, which oft-recurring attacks of asthma are liable to induce. The paroxysms, although occasionally periodic, do not generally observe any regularity in their return.
They may recur each successive night for several days, or there may be no return for many weeks or months, this being to a large extend dependant on a renewal of the exciting cause.