Certified Pulmonary Function Technologist (CPFT) Practice Exam

What is the low calibration gas concentration for CO2 in a blood gas analyzer?

1. 2%

2. 5%

3. 8%

4. 12%

The correct answer is: 5%

In the context of calibrating a blood gas analyzer, the low calibration gas concentration for carbon dioxide (CO2) is typically around 5%. This is because the calibration process must account for the physiological range of CO2 in human blood, which generally reflects levels encountered in normal respiratory function and metabolic processes. Setting the low calibration concentration at 5% allows for an accurate baseline that corresponds with the lowest expected levels in arterial blood under normal conditions. This concentration is critical to ensure that the analyzer can correctly interpret and report CO2 levels, especially in cases of respiratory acidosis or alkalosis, where the CO2 levels might vary significantly. While other concentrations provided in the options may be relevant in various contexts or different devices, they do not serve as the standard low calibration point for CO2 in a blood gas analyzer, thus reinforcing 5% as the most appropriate choice.