Respiratory Physiology Lecture 2 part 9: Ventilation Flashcards
Tidal volume
volume of inspired air at each breath
Approximately how much air is inspired (in tidal volume)?
~0.5 L
Total/minute ventilation
total amount of air moved into the respiratory system per minute
Total/minute ventilation = ??
Total/minute ventilation = Tidal volume x respiratory frequency
= 0.5 L x 15 bpm (Breaths per minute)
= 7.5 L/min
Alveolar ventilation
amount of air moved into the alveoli per minute
What does alveolar ventilation depend on?
It depends on the anatomical dead space
How much is anatomical dead space?
0.15 L
Alveolar ventilation = ??
Alveolar ventilation = (TV - anatomical dead space) x frequency
VA = (VT - VD) x frequency
= (0.5 - 0.15) L x 15 bpm
= 5.25 L/min
Why is alveolar ventilation lower than total/min ventilation?
due to anatomical dead space consideration
What zone is anatomical dead space in?
conductive zone
How much of normal breath is not available for gas exchange?
~ ⅓ (1-2 L)
VA = (VT - VD) x frequency
Alveolar ventilation
What happens to anatomical dead space with breath size?
anatomical dead space is constant regardless of breath size
Effects of Breathing Pattern on Alveolar Ventilation
Normal quiet breathing → 4200 mL/min (VA)
Shallow & fast → 0 mL/ min (VA)
Deep & shallow → increase (VA)
How does breathing patter effect minute ventilation?
stays the same