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
Way to measure ventilation =
Helium dilution method using a spirometer
Way to measure diffusion =
TLCO/DLCO
TLCO
Transfer factor of lung for carbon monoxide
DLCO
Diffusion capactiy of carbon monoxide
How long does patient hold breath for during a TLCO test?
10 seconds
Way to measure perfusion =
CT pulmonary angiogram
ECG
Ex of what would reduce perfusion
Pulmonary embolism
Arteriovenous malformations
Intracardiac shunts
Normal O2 sat
95-100
O2 for COPD
88-92
What does a shift of the Hb-O2 dissociation curve to the right mean?
Lower affinity for O2
Conditions that shift dissociation curve to right:
High H+ Low pH High CO2 High BCG High temp
What does a shift of the Hb-O2 dissociation curve to the left mean
Higher affinity for O2
Conditions that shift dissociation curve to the left
Low H+ High pH Low CO2 Low BCG Low temp
Systems that regulate acid-base balance:
Chemical
Respiratory
Renal
Chemical buffers:
HCO3-
PO4-
Proteins
Respiratory buffers
HCO3-
Renal buffers
HCO3-
PO4-
NH3-
Acidaemia =
pH <7.35
Alkalaemia
pH >7.45
Type 1 respiratory failure =
Low pa(O2), low/normal p(CO2)
Types 2 respiratory failure =
Low p(O2) High p(CO2)
In restrictive lung disease air is doing what normally?
Flowing
Ex of obstructive lung disease =
Asthma
COPD
Bronchiectasis
Ex of respiratory disease =
Pulmonary fibrosis
Obesity
Chest wall deformities
Neuromuscular disorders
What happens to lungs in fibrosis?
Small lungs with reduced compliance
