The physiological consequences of lung disease Flashcards
Minute ventilation =
tidal volume x respiratory rate
Alveolar ventilation
(tidal volume - dead space) x respiratory rate
What is dead space?
Volume of air inspired that doesn’t take part in gas exchange
Muscles of inspiration
Diaphragm
External intercostals
Sternocleidomastoid
Pec minor
Expiration is usually a
Passive process
Muscles of expiration are activated with
Increased respiratory drive
Muscles of expiration
Internal intercostals
Rectus abdominis
Transversus abdominis
What is ventilation a balancing act between
Ventilatory capacity
Ventilatory demand
Ventilatory capacity =
Maximum spontaneous ventilation that can be maintained without the development of respiratory muscle fatigue
Ventilatory demand =
spontaneous minute ventilation required to maintain normal pCO2
Name a law of diffusion
Fick’s law of diffusion
Fick’s law of diffusion =
Rate of transfer of a gas through a sheet of tissue is proportional to: 1. Tissue area 2. Difference in gas partial pressure And inversely proportional to: 1. Tissue thickness
Normally, perfusion is matched to
Ventilation
Name a mechanism that matches ventilation to perfusion
Hypoxic pulmonary vasconstriction
What happens when there’s normal ventilation but reduced perfusion =
Alveolar ventilation
What happens when theres reduces ventilation but normal perfusion
Shunting of deoxygenated blood