Laryngoscopic examination reveals more or less congestion of the air-passages. "In ordinary respiration the glottis is widely open during inspiration, and at each expiration the arytenoid cartilages approach each other so as to narrow the glottis; but in the labored respiration of asthma the glottis is fixed in the condition of expiration; that is, the glottis is narrowed, and the air enters and is expired through the same narrow space."6
6 Steavenson, Spasmodic Asthma, p. 23.
The embarrassment of respiration and the pressure of the air in the distended alveolæ by impeding the capillary circulation of the lungs prevent the left auricle from receiving its full supply of blood; hence the pulse is small and weak during the paroxysm, but regains its natural volume as soon as its immediate effects are over. The action of the heart, like every other phenomenon of asthma, is subject to constant variation. At one moment it beats tumultuously, while at the next its action may be so feeble as to cause temporary syncope (Sée). The venous blood, unable to overcome the obstacles to its passage, is forced back into the vessels, causing distension of the cervical veins and the jugular pulse sometimes observed in severe attacks. The bluish hue of the face in bad cases is due to cyanosis resulting from insufficient aëration of the blood. The paroxysm is unattended with fever, the temperature, if altered at all, being rather below than above the normal. Coldness of the face and hands is quite a common symptom in protracted cases.
In addition to the nervous sensations described among the premonitory symptoms, patients have been known to suffer from disturbances of a more serious nature during the paroxysm. In some instances there is complete loss of consciousness, and Riegel7 states that such cases have been known to have tetanic convulsions of the trunk and extremities.
7 Loc. cit. p. 285.
The course of an attack of asthma is in most cases quite typical, the paroxysms recurring nightly for an indefinite period, and usually increasing in severity until, as in epilepsy and other nervous diseases, it finally exhausts itself. On awaking from the sleep which usually succeeds the final paroxysm the patient, unless the attack has been very mild and of short duration, feels weak and exhausted, but there is no tendency to the recurrence of the dyspnoea; on the contrary, he may expose himself with perfect impunity to the causes which at other times would be certain to produce an attack. The chest feels stiff and sore, the cough and expectoration diminish, and in a few days disappear, and if the disease has produced no organic lesion the patient returns to his usual state of health.
DURATION.—The duration of asthma, except in young persons and in those rare cases in which the cause can be discovered and removed, is very indefinite, the disease lasting for years, if not for life. As the patient grows older the attacks become less severe, but are more frequent. Sometimes a case which has recurred for years and defied the most energetic treatment will all at once recover of itself.
SEQUELÆ.—Although bronchial asthma is essentially a neurosis, and therefore purely functional in its character, it is rare for it to continue for any great length of time without causing some organic affection of the lungs or heart.
The most common sequel of asthma is emphysema. The bronchial tubes being more or less completely closed, either by contraction of their muscular fibres or by plugs of thick, viscid mucus, the air pent up in the parts beyond the obstruction is subjected to the negative pressure produced by the exaggerated inspiratory act, becomes rarefied, and, in obedience to the diminished resistance induced by the partial vacuum in the thorax, causes distension of the air-cells. This condition continues until, the tubes having again become pervious, the natural elasticity of the lung-tissue, aided by the expiratory muscles, forces out the air and permits them to return to their natural size. This is the transitory emphysema to which we have already alluded. Germain Sée8 regards it as analogous to the paralytic emphysema which occurs the moment the pneumogastric is divided. With repeated attacks the air-cells lose their elasticity and remain permanently dilated. Owing to the constant distension, the walls of the alveolæ become more and more attenuated, until, finally giving way, two or more of them coalesce, forming one large cell. The symptoms of this condition are the same as those of ordinary vesicular emphysema.
8 Op. cit., p. 637.