Ventilation & Compliance 1 Flashcards
What is tidal volume (Vt)?
The volume of air breathed in or out of the lungs at each breath.
What is inspiratory reserve volume (IRV)?
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.
What is expiratory reserve volume (ERV)?
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration.
What is residual volume (RV)?
The volume of gas in the lungs at the end of a maximal expiration.
What is total lung capacity (TLC)?
TLC = IRV + Vt + ERV + RV
What is vital capacity (VC)?
VC = IRV + Vt + ERV
What is inspiratory capacity (IC)?
IC = Vt + IRV
What is function residual capacity (FRC)?
FRC = ERV + RV
What is FEV1?
Forced expired volume in 1 sec.
What is FEV1:FVC?
Fraction of forced vital capacity expired in 1 sec.
What is the normal value for tidal volume?
500ml
What is the normal value for IRV?
3000ml
What is the normal value for ERV?
1100ml
What is the normal value for residual volume?
1200ml
What is the average lung capacity (TLC)?
5800ml (6L)
Why is there a residual volume left in the lungs on expiration?
- To prevent the alveoli collapsing - if this were to happen then large amounts of energy would have to be invested to inflate them again.
- Allows constant gas exchange.
What is pulmonary ventilation?
It is the total air movement into and out of the lungs per minute (Vt x respiratory rate)(L/min)
This value is relatively insignificant in functional terms as it included anatomical dead space which is not involved in gas exchange.
What is alveolar ventilation?
The amount of fresh air reaching the alveoli per minute which is available for gas exchange.
(L/min)
What is the difference between pulmonary and alveolar ventilation?
Pulmonary ventilation accounts for total air movement of around 500ml, which includes around 150ml of anatomical dead space.
On expiration, 150ml of stale air leaves the alveoli but remains in the conducting zone. On inspiration, this stale air returns to the alveoli along with 350ml of fresh air available for gas exchange.
Alveolar ventilation only takes into account the air available for gas exchange (350ml) which is different from the pulmonary ventilation value (500ml).
What is hyper ventilation?
When the alveolar ventilation is higher than normal, this results from being relaxed.
Partial pressure of O2 rises (about 120 mm Hg)
Partial pressure of CO2 falls (about 20 mm Hg)
What is hypoventilation?
When the alveolar ventilation is lower than normal, this results from anxiety and higher respiratory rate and small/shallow breaths.
Partial pressure of O2 falls (about 30 mm Hg)
Partial pressure of CO2 rises (about 100 mm Hg)
What is considered normal alveolar ventilation?
4.2L/min
Tidal volume x resp. rate
(500ml x 12 breaths/min)
Why is there CO2 in our cells and blood if there is negligible quantities of CO2 in the atmosphere and we do not breathe it in?
Our bodies produce CO2 as a waste product during cellular respiration.
What is partial pressure?
The pressure exerted by a single gas in a mixture of gases.
E.g. partial pressure of O2 in the atmosphere (O2, N2, CO2, H2O)
Why is the partial pressure of oxygen lower in the alveoli than in the atmosphere?
- The air in the alveoli contains more water vapour than in the atmosphere (from passing through the nasal cavity)
- There is gas exchange taking place, residual volume, always air in the lungs.
- Stale air is being mixed with fresh air with alveolar ventilation.
What is the normal partial pressure of oxygen in the alveoli?
100 mm Hg
13.3 kPa
What is the normal partial pressure of carbon dioxide in the alveoli?
40 mm Hg
5.3 kPa
What is the normal partial pressure of oxygen in the arterials?
40 mm Hg
5.3 kPa
What is the normal partial pressure of carbon dioxide in the alveoli?
45 mm Hg
6 kPa
