Asthma Medicines

Assessing enrichment of the blood with oxygen by the lung can be made by a noninvasive technique called oximetry, in which a sensor placed on the fingertip or earlobe can accurately measure oxygen saturation. Such a sensor is often immediately placed on an asthmatic patient who has been admitted to an emergency room. Oxygen saturation testing measures how much oxygen the blood has acquired in the air sacs of the lungs.

The oximeter transmits different wavelengths of light through small blood vessels called capillaries. The fingernail and earlobe are used since these small vessels are close to the surface of the skin. In these small blood vessels oxygen is carried by a protein called hemoglobin. As oxygen is used by the body, the hemoglobin undergoes a change that can be detected by a different absorption of light from the oximeter. This determine is made during each pulse beat and from the relative amounts of hemoglobin with and without oxygen, the saturation is determined. The patient’s pulse is also recorded.

This technique can be extremely helpful in evaluating bronchial asthma since oxygen levels will typically fall with significant degrees of airway obstruction. An asthma attack that reduces oxygen levels signifies a more severe episode and calls for aggressive medical treatment. Oximetry is painless and does not require blood sampling.

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Although there are differences from patient to patient, the asthma attack is typically characterized by shortness of breath and wheezing. Cough and mucus production may be prominent symptoms. In some patients wheezing may not occur and a cough may be the dominant symptom. The patient demonstrates a rapid rate of breathing, often with heaving of the chest and use of neck muscles to assist each breath. During an attack the patient is totally disabled. Even speech may be impossible due to severe breathlessness. The patient may be totally consumed by the effort to breathe and unable to eat or dress. The patient is often restless and unable to lie flat. Severe attacks may end in exhaustion, with ominous slowing of the respiratory rate and arrest of breathing.

Depending on the severity of the patient’s disease the attack may be totally or partially reversible, allowing the patient to assume normal activities between episodes. Patients with severe asthma, however, may remain to some degree symptomatic at all times.

It should be noted that the degree of wheezing can be misleading. The severity of the asthmatic attack should never be judged on this basis alone. Some patients who are capable of moving large amounts of air may produce more turbulence and audible wheezing than others who are so severely obstructed that their breaths are shallow and incapable of producing much sound.

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