=> anatomical dead space increases by 20mL for each L of lung volumeĮ.g.The Respiratory System’s Primary Function Is the Transport of Oxygen and Carbon Dioxide Between the Environment and the Tissues => at infancy, anatomical dead space is higher for body weight (3.3mL/kg) => modified: V D/V T = (P aCO2 - P ECO2)/P aCO2Īdditional notes Factors influencing anatomical dead space NB: P ECO2 is the partial pressure in MIXED expired gas, NOT end-tidal gasĮnghoff modification - using measured arterial PaCO2 as an estimate of the ideal alveolar PACO2 F ACO2 = fractional concentration of CO2 in alveolusīohr equation: V D/V T = (P ACO2 - P ECO2)/P ACO2.F ECO2 = fractional concentration of CO2 in mixed expired air.=> V T x (F ACO2 - F ECO2) = V D x F ACO2 Using vs expired volume graph, anatomical dead space is taken to be at the mid-point of the transition from conducting zone to gas exchange zone.īy using Bohr's equation and Bohr's methodīased on 'all expired CO2 comes from alveolar gas', and dead space doesn't eliminate CO2.During the following expiration, increases from 0% (pure dead space gas) to equilibrium (pure alveolar gas) (i.e.

Measurement Measurement of anatomical dead spaceīased on rapid dilution of gas already in lung (N2 or CO2) by inspired gas (100% O2). When using mask or anaesthetic circuit tubing, this adds to the conducting zone. during exercise), physiological dead space is reduced (due to reduction in alveolar dead space).Īlveolar dead space is the part of the inspired gas which passes through the anatomical dead space to mix with gas at the alveolar level, but does not participate in gas exchange. The difference between anatomical dead space and physiological dead space is alveolar dead space.

Physiological dead space is the part of the tidal volume which does not participate in gas exchange. Write short notes on physiological dead space (1990)ĭefinition - the volume occupied by gas which does not participate in gas exchange in lung.Īnatomical dead space is the volume of the conducting airways.Īnatomical dead space is constant regardless of circulation.

Lung dead space definition