Ventilation & compliance 1 Flashcards
(33 cards)
State Dalton’s Law
The total pressure of a gas mixture is the sum total of the pressures of the individual gases.
Effect of hyperventilation and hypoventilation on PCO2 and PO2
Hyperventilation: PO2 will rise and PCO2 will fall
Hypoventiation: PO2 decreases and PCO2 increases
Functions of Type l & Type ll Pneumocytes
Type l: Thin walled cells allows gas exchange
Type ll: specialised cells that secretes surfactant liquid
What is surfactant?
-phospholipid containing liquid produced by Type ll alveolar cells.
What is surface tension?
tension caused by the attraction of water molecules
Function of surfactant
- Reduces surface tension on alveolar surface membrane, hence preventing alveoli to collapse
- increases lung compliance
- more effective in small alveoli than large as surfactant molecules come closer together and become more concentrated
Describe the stimulation of surfactant production
stimulated by thyroid horemeones and cortisol towards end of pregnancy
- 25 weeks gestation ; complete by 36 weeks
- saccular stage
What do premature babies suffer from in terms of surfactant production? State the treatment
- Infant Respiratory distress syndrome ( IRDS)
- treat with aerosol can of surfactant and corticosteroids given to mother
What is compliance?
Change in volume relative to change in pressure
-represents stretchability of lungs
What does high/low compliance indicate?
High compliance: large increase in lung volume for decrease in pressire
Vice versa
What is emphysema?
Loss of elastic tissue, hence expiration requires effort
What does fibrosis mean?
- Accumulation of fibrous tissue,( due to fibrosis/scarring) hence inspiration requires effort
- leads to stiffness of lung
Obstructive vs restrictive lung disease
Obstructive: obstruction of airflow on expiration. Causes increased airway resistance
Restrictive: restriction of lung expansion. Leads to loss of lung compliance + lung stiffness
State examples of obstructive lung disorders
Asthma
COPD - Chronic bronchitis (inflammation of the bronchi ) & Emphysema ( destruction of alveoli, loss of elasticity)
State examples of restrictive lung disorders
Fibrosis: (formation/development of excess fibrous connective tissue
Infant respiratory distress syndrome: (insufficient surfactant prod.)
Oedema:
Pneumothorax:
What is spirometry?
A technique used to measure lung function. Measurements classed as static/dynamic
Describe what is meant by static + dynamic lung volumes
Static:volume exhaled is measured
Dynamic: time taken to exhale a certain volume is measured
State the effect of Obstructive lung disease on FVC, FRC+ FEV1
FEV1:decreases
FVC: can be normal
FRC:increases
FEV1.FVC: decreases
State the effect of pulmonary fibrosis on absolute rate of airflow, total volume and the ratio
The absolute rate of airflow decreases + total volume is also reduced due to the limitations of lung expansions. The ratio is constant but can increase
What is the tidal volume?
The volume of air breathed in/out of lungs at each breath
What is the expiratory reserve volume (ERV) + IRV?
- The maximum volume of air expelled from the lungs in normal expiration
- The maximum volume of air drawn out from lungs in normal inspiration
What is the residual volume?
The volume of gas in lungs at the end of maximal expiration
What is the vital capacity?
- Maximam volume of air that can be exhaled after maximal inspiration
- TV + ERV + IRV
What is the Total lung capacity?
- All the air that can be inhaled in lungs
- vital capacity + residual volume?
