Therapeutic aspects of pulmonary emphysema.

The emphysema patient who suffers a bronchospastic crisis represents one of the most trying situations with which we, as physicians interested in chest diseases, are confronted. The allergic approach in most patients with pulmonary emphysema has proved to be so disappointing generally that many physicians are inclined to omit completely a serious evaluation of allergenic possibilities. Certainly even the partial conquest of the allergic bronchospastic component is cogent and a careful survey for potentially significant extrinsic offenders followed by desensitization may be fruitful in a small percentage of patients. It is always important to bear in mind that people with emphysema hav#{128} physiological derangements which are seriously compromised secondary to superimposed bronchospastic difficulties. Therefore, a few cardinal principles are worthy of review: 1) Adequate gas exchange, which takes place at the alveolar level, requires effective alveolar ventilation. There is an enormous quantitative difference between two individuals, each exhibiting a minute volume of 10 liters per minute-one of whom has a tidal air of 500 cc. who breathes 20 times per minute, and the other who breathes 40 times a minute with a tidal air of 250 cc. The significant difference lies in the consideration of the anatomical dead air space, which ordinarily is approximately 150 cc. for adult males. Effective alveolar ventilation in the first instance would be 500-150 cc. (the volume of the anatomical dead air space) or 350 times 20 breaths per minute, which equals 7000 cc. per minute; whereas in the second case we would have 250-150 cc. times 40 breaths per minute, which equals 4000 cc. per minute. Obviously there is a tremendous quantitative difference between 4000 and 7000 cc. of effective ventilation per minute. Based on this consideration, tracheotomy may be indicated in desperate situations, the purpose of tracheotomy being to diminish the volume of the anatomical dead air space as well as for suctioning secretions in such cases. 2) Many emphysema patients already exhibit varying degrees of diminished arterial oxygen saturation with or without an increase in the partial pressure of carbon dioxide in the arterial blood. The net effect of superimposed bronchospastic difficulties is to aggravate the existing degree of lowered arterial oxygen saturation and hypercapnia by diminishing further the ingress of oxygen and the egress of carbon dioxide. This circumstance is referred to as alveolar hypoventilation.