Physiology Flashcards
What happens during inspiration?
Diaphragm contracts and flattens
External intercostals contact and increase ant-post diameter
Ribs moved up and out
Increased in lung size reduces intra-alveolar pressure
Air enters down pressure gradient
How do the lungs adhere to the thoracic wall?
Intrapleural fluid cohesiveness
Negative intracellular pressure
Why do the lungs and chest wall recoil?
Due to elasticity
What is the role of surfactant?
Reduces alveolar surface tension to prevent collapse
What cells produce surfactant?
Type ii alveoli
What causes respiratory distress of the newborn?
Preterm births result in babies with lack of surfactant so high surface tension
What is the theory behind alveolar interdependence?
If an alveoli starts to collapse…
- Stretches surrounding alveoli
- They recoil -> Expansive
- Re-opens closed alveoli
What is the tidal volume?
Volume entering/leaving lungs in a single breath (~500ml)
What is the inspiratory reserve volume?
Extra air that can be expired over resting TV (~3000ml)
What is the inspiratory capacity?
Max volume of air inspired at the end of quiet expiration (~3500ml)
IC = IRV + TV
What is the expiratory reserve volume?
Extra air that can be expired after quiet expiration (~1000ml)
What is the residual volume?
Minimum lung volume after max expiration (~1200ml)
What is the functional residual capacity?
Volume of air in lungs after normal quiet expiration (~2200ml)
FRC = ERV + RV
What is the vital capacity?
Max volume of air that can be exhaled following max inspiration (~4500ml)
What is the total lung capacity?
TLC = VC + RV
If pulmonary compliance decreases, what effects will be noted?
Increased inflation work
Shortness of breath
Restrictive pattern
What can cause decreased Po compliance?
Po fibrosis/oedema
Lung collapse
Pneumonia
No surfactant
What occurs in emphysema?
Increased compliance
Elastic recoil lost
Increased exhalatory work
Which is greater and why, alveolar or pulmonary ventilation?
Pulmonary
Anatomical dead space
Is it better to increase tidal volume or RR to increase ventilation?
TV
What factors affect gas exchange in alveoli?
Partial pressure gradient of gasses
Diffusion coefficient for gasses
SA
Membrane thickness
What would a big gradient between PAO2 and PaO2 suggest?
Right-left shunt in the heart