ABSTRACT
The primary function of the respiratory system is to effectively manage oxygen uptake and carbon dioxide output. The load imposed on the lung depends on the metabolic activity of the body, and can change over a wide range, primarily influenced by body temperature and muscle activity. The lung has a huge reserve capacity and, despite more than 50-fold changes in oxygen consumption and carbon dioxide production, the arterial and mixed venous blood gases are maintained remarkably constant. The normal range of
blood gas tensions is = 4.8-5.9 kPa and = 11.3 - 13.3 kPa. The first signs of pulmonary impairment usually manifest during exercise, when the demands on
functional capacity are high. Respiratory failure is defined by >6.7 kPa and
< 8.0 kPa (breathing room air) measured at sea level and without metabolic alkalosis.
