Ventilation And Compliance Flashcards
Volume of anatomical dead space
150ml
TLC total lung capacity
5800ml
ERV expiratory reserve volume
1100ml, big breath out after normal expiration
TV tidal volume
500ml, normal breaths in and out
IRV inspiratory reserve volume
3000ml, big breath on top of tidal volume (added is inspiratory capacity)
FRC functional residual capacity
expiratory reserve plus residual volume
RV residual volume
1200ml Always there
FEV1
Forced expired volume in 1 second
Pulmonary (minute) ventilation
Total air movement in and out of lungs
Alveolar ventilation
Fresh air getting to alveoli
PO2 change
160ml in air to 100ml in alveoli due to water and dead space and bc lungs aren’t empty
How much air participates in gas exchange each breath
350ml (75%) due to dead space
Hypoventilation
Not enough air getting into lungs, eg rapid but shallow breathing
Hyperventilation
Too much air, eg slow but deep breathing
Surfactant
Reduces surface tension on alveolar surface membrane due to air water interaction and attraction between water molecules. Therefore reduces tendency for lungs to collapse and increases lung compliance. More effective in smaller alveoli
When does surfactant production happen and by what hormones is it stimulated
At 25 weeks until 36 weeks, stimulated by thyroid hormone and cortisol which reduce at end of pregnancy.
IRDS
Infant respiratory distress due to lack of surfactant
Compliance
Change in volume relative to change in pressure. Represents stretchability of lungs
Emphysema
Loss of elastic tissue so expiration takes more effort
Fibrosis
Inert fibrous tissue means effort of inspiration increases
Location of lung affecting pressure volume
Alveoli at apex are stretched so need more pressure for less volume increase and vice versa
Obstructive lung disease
Increased airway resistance eg asthma and COPD (chronic bronchitis is inflam, emphysema is destruction of alveoli and loss of elasticity). Slower exhalation so fev/FRC is reduced, tho FRC may also reduced and FVC is reduced but less than FEV is
Restrictive lung disease
Loss of lung compliance eg fibrosis, IRDS, oedema, pnuemothorax. Ratio can be constant as rate of airflow and total volume both decrease. Ratio can also increase as a large proportion of volume can be exhaled in first second
Spirometry types
Static is just exhalation volume, dynamic is time to exhale
FEV1/FVC
Forced expiratory volume in 1 second divided by total exhalation
FEF25-75
Forced expiratory flow, average over fvc, correlates with FEV1 but with more striking changes
