why is PaCO2 normal in shunt vs Dead space

Normal PaCO2 = 38.3mmHg +/- 7.5mmHg (95% limits, 2 standard deviation.)ĭifference between arterial PaCO2 and end-tidal PCO2 => Thus by convention, arterial and 'ideal' alveolar PCO2 values are taken to be identical. Shunt of 10% will cause an alveolar-arterial PCO2 gradient of about 0.7mmHg. => It is much lower in PCO2 because the CO2-free gas from anatomical dead space dilutes even more.

Mixed expired PCO2 is the partial pressure of CO2 in the expired gas during a tidal breath. => It is lower than 'ideal' alveolar PCO2, because the almost CO2-free gas from alveolar dead space dilutes and lower the end-tidal PCO2. => ASSUMED to be representative of alveolar gas What is the end tidal CO2? How does it differ from arterial CO2 tension and the mixed expired CO2 tension? What factors influence its value? (1995)Įnd-tidal PCO2 is the partial pressure of CO2 at the end of expiration during tidal breathing. Briefly describe the potential causes of a difference between measured end-tidal and arterial partial pressure of carbon dioxide (03B11) (96B7)

Why is PaCO2 normal in shunt vs Dead space