In the setting of exercise physiology the body is able to maintain a constant pH, arterial PCO2 and PaO2. This is maintained by hyperventilation.
The pH balance in the human body is tightly regulated by both renal and pulmonary physiology. In the setting of increased tissue build up of CO2, the body hyperventilates to remove the excess. If a venous blood gas (VBG) was performed in a person undergoing physical exercise it is likely that an acidosis would be found due to the build up of CO2. It is also likely that PvO2 would be decreased due to increased O2 consumption during exercise. A normal arterial blood gas (ABG) has the following range of values: pH 7.35-7.45, PaO2 80-100, PCO2 35-45, HCO3 22-26.
Allingham reviews the use of arterial blood gas measurements for family physicians. The author discusses the power of the ABG to determine issues with gas exchange, lung pathology, and metabolic abnormalities. The patients immediate ventilation status can be determined by a paC02 of less than 37 indicating hyperventilation and 43 or more indicating hypoventilation. In the absence of a metabolic abnormality the pH should respond appropriately and if it does not a secondary metabolic process is also at play.
Wasserman et al. reviews the methods that the body uses to maintain its pH during exercise. The authors discuss that the main mechanism is ventilation of CO2, but that it can be affected in patients with underlying illness such as COPD and CHF.
Answer 1: This ABG represents respiratory failure with chronic metabolic compensation.
Answer 3: This ABG represents a venous blood gas for this scenario.
Answer 4: This ABG represents an uncompensated metabolic alkalosis.
Answer 5: This ABG represents acute respiratory alkalosis.
Allingham JD. Arterial blood gases: a clinical review for family physicians. Can Fam Physician. 1981 Oct;27:1605-13.
PMID:21289824 (Link to Abstract)
Wasserman K, Cox TA, Sietsema KE. Ventilatory regulation of arterial H(+) (pH) during exercise. Respir Physiol Neurobiol. 2014 Jan 1;190:142-8.
PMID:24369924 (Link to Abstract)