Answer:
This is an alveolar gas equation question and it is used to approximate the partial pressure of oxygen in the alveolus (PAO2):
The equation states;
PₐO₂ = P₁O₂ - (PₐCO₂/R) = [(PB - PH₂O) × F₁O₂ - (PₐCO₂/R)] ...................Eqn 1
where
PₐO₂ = Alveolar partial pressure of O2 = 115mmHg
P₁O₂ = Inspired partial pressure of O2 = 150mmHg
PB = barometric pressure,
PH₂O = Water vapor pressure (usually 747 mmHg),
F₁O₂ = fractional concentration of inspired oxygen,
and R = gas exchange ratio. (Usually around 0.8)
FₐO₂ = Fraction of alveolar O₂
(O₂) = 1L/min = 1dm³
From eqn 1. we have
PₐCO₂ = (P₁O₂ - PₐO₂)/R
= (150 - 115)x0.8
PₐCO₂ = 28mmHg
Similarly from Eqn 1, we have
F₁O₂ = (PₐO₂ + PₐCO₂/R)/(PB - PH₂O)
F₁O₂ = (115 + (28/.8))/(747 - 47)
F₁O₂ = 0.21
Now to find the Alveolar Ventilation A, we will use this equation;
O₂ = A(F₁0₂ - FₐO₂) .................Eqn 2
But FₐO₂ = PₐO₂/(PₐO₂ + PₐCO₂)
FₐO₂ = 115/ (115+28) = 0.8
A = O₂/(F₁0₂ - FₐO₂)
A = 0.001/(0.21 - 0.8)
A = 0.00169m³/min
Hence, the aveolar ventilation is 0.00169m³/min
