The effects which drugs may, conceivably, have on respiration are of four varieties.
They may either stimulate or depress the respiratory center.
They may alter respiration indirectly by increasing or decreasing metabolism.
They may alter the general character of breathing, rapid and shallow or slow and deep, or thoracic or abdominal by producing changes in the mechanical conditions within the chest or abdomen, by acting on the circulation, the abdominal viscera or the thoracic or abdominal musculatures.
They also may alter respiration by acting as bronchoconstrictors or dilators, and hence altering the dead space in the chest, which necessitates a compensatory change in the ventilation.
The data which must be obtained in studying these various actions are: the carbon dioxid elimination and the oxygen absorption, which give the metabolism ; the carbon dioxid tension of the alveolar air and the ventilation of the lungs, which give