What does the presence of a compensated respiratory acidosis at rest with an elevated a-a gradient and development of a respiratory alkalosis at maximal exercise mean on a complex pulmonary exercise test mean.

Acidosis: Respiratory acidosis is usually caused by increased carbon dioxide. This is usually the result of hyperventilation or for example emphysema. Compensation is usually from the kidneys retaining bicarb. A a gradient is alveolar arterial oxygen gradient. The gradient is increased often the people with lung disease or for example with a pulmonary embolus.