Question

Calculate V_A (Alveolar Ventilation) based on the following information:

P_aO₂=100mmHg

F_iO₂=0.21

P_ECO₂=30mmHg

P_aCO₂=40mmHg

V_T=550mL

RR=16bpm

Please show every step.

Answer 1

VA=(Tidal Volume−Dead Space Volume)×Respiratory Rate

Partial pressure of CO2 in the expired air,P_ECO₂=30mmHg

Partial pressure of CO2 P_aCO₂=40mmHg

Tidal volume, V_T=550mL

Respiratory rate, RR=16bpm

1.First we have to calculate dead space volume,

Vd (Dead space volume) =vt*PaCO2-PECo2/PaCO2

PaCO2=40 mmHg

PECO2=30 mmHg

So when applying the formulae,

Vd (Dead space volume)= 550* 40-30/40

=550*10/40

=5500/40

Vd (Dead space volume)=137.5

WHEN WE ARE CALCYLATING   V_A (Alveolar Ventilation)

VA=(Tidal Volume−Dead Space Volume)×Respiratory Rate

Tidal volume =550 ; Dead space volume=137.5, respiratory rate = 16 bpm

When applying the formulae,

VA=550-137.5*16

=412.5*16

Alveolar ventilation , VA=6600 ml/min