Question

Q5. In a healthy male, normal values of QC02= 200 mL/min (STPD), Tidal volume = 510 mL (BTPS), Dead volume = 150 mL (BTPS), and respiratory rate is 12 breaths per minute. During exercise, QC02= 1000 mL/min (STPD), and respiratory rate increases to 20 breaths per minute. Assuming no change in PA, CO2, what is the new tidal volume [4points]?

Answer 1

Ans 5:

At normal situation,

Alveolar Ventilation = (Tidal volume - Dead volume) x Respiratory rate

= (510 - 150) x 12

= 360 x 12 = 4320 ml/ min

During exercise, as there is no change in PACO2, then Alveolar ventilation remains same i.e. 4320 ml/ min, Respiratory rate = 20 b/min and Dead volume = 150 ml

So,

Alveolar Ventilation = (Tidal volume - Dead volume) x Respiratory rate

then, Tidal volume = (Alveolar ventilation/ Respiratoy rate) + Dead volume

= (4320/ 20) + 150

= 216 + 150 = 366 ml

So, new tidal volume during exercise = 366 ml