What is ventilation? What is minute ventilation?
ventilation: process by which air moves in and out of the lungs
minute ventilation: volume of air that enters or leaves lungs per minute: V(E) = Tidal Volume (Vt) x frequency (f)
Tidal Volume
- normal breathing
- varies with age, sex, body position and metabolic activity
- typically around 500 mL
- measured with spirometry
Give the definitions of the lung volumes
- Tidal volume: amount of air inhaled or exhaled in one breath during relaxed, quiet breathing
- Inspiratory reserve volume (IRV): amount of air in excess of tidal inspiration that can be inhaled with maximum effort
- Expiratory reserve volume (ERV): amount of air in excess of tidal expiration that can be exhaled with maximum effort
- Residual volme (RV): amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated between breaths and mixes with fresh on next inspiration
Give the definitions of the lung/ respiratory capacities
- Vital capacity (VC): amount of air that can be exhaled with max effort after max inspiration (ERV + TV + IRV); used to assess strength of thoracic muscles as well as pulmonary function
- Inspiratory capacity (IC): max amount of air that can be inhaled after a normal tidal expiration (TV + IRV)
- Functional residual capacity (FRC): amount of air remaining in lungs after normal tidal expiration (RV + VC)
- Total lung capacity (TLC): max amount of air lungs can contain (RV + VC)
FVC and FEV1
FVC - forcefully breathing out => most air is out in 1 second (FEV1)
- graph shows that there is a certain amount of volume that cannot be exhaled (curve tapers off) = RV
Explain the flow volume loop
can determine:
- FVC
- PEFR (peak expiratory flow rate): maximal flow rate achieved during expiratory maneuver
- expiratory flow rates
- instantaneous flow rate at which 50% of VC remains to be exhaled is the FEF50 or Vmax50
… 75% of VC has been exhaled is the FEF75
What is used in diagnosing lung disease? What are the two classifications of pulmonary diseases?
- measurements of pulmonary function such as FVC, FEV1, PEFR are useful in diagnosing lung disease
- classified as obstructive or restrictive
Obstructive diseases
- an obstruction to flow of air resulting in an increased resistance to the movement of air into or out of the airways
obstruction can be:
1. inside lumen
2. in airway wall
3. surrounding the airway
- most common = decrease in airway diameter
examples:
1. asthma
2. chronic bronchitis
3. aspiration of foreign material
What is the bronchial wall of an asthmatic individual like?
- characterized by increased responsiveness of the airways to various stimuli
- manifests as widespread narrowing of airways (bronchoconstriction) (increased resistance)
- excessive mucous secretion
- chronic inflammation
- chest tightening, wheezing, cough
- excess airway smooth muscle => more constriction
Restrictive airway diseases
- not possible to fully fill lungs with air => full expansion of lung is restricted in some manner
- can result from conditions that ‘stiffen’ the lungs; stiffness of chest walls; problems with muscles or nerves involved in respiration; physical abnormalities
can be due to:
1. alterations in the parenchyma
2. diseases of the pleura
3. diseases of the chest wall
4. diseases of neuromuscular apparatus
example: pulmonary fibrosis, in which elastic tissue is replaced with thickened fibrotic (scar) tissue
How are FVC and FEV1 affected in patients with lung disease?
Obstructive disease (asthma): FEV1 is reduced because an obstruction results in air moving slower, FVC is reduced because airways are more narrow (some airways will clamp shut permanently, not allowing any air out)
Restrictive disease (fibrosis): COME BACK
NOT DONE!!!
