Explain the causes of the differences between measured end tidal and arterial partial pressures of carbon dioxide.
The main points for a pass were
• Normal value for the difference between end tidal and arterial C02
• Physiological factors e.g. alveolar dead space, failure to plateau of the capnograph
• Pathological factors e.g. cardiac arrest, air embolism, asthma.
• Sampling site errors etc
A common mistake was to state that dead space caused the difference between end tidal and
arterial carbon dioxide but not which type of dead space. The Bohr equation was not