1. Ventilation: lung volumes and capacities Flashcards
Define inspiration
Muscles contract and do work
Define Expiration
Passive in quiet breathing in health
Define breathlessness
Usually more work being done by the respiratory muscles
What is the eqn for minute volume?
Tidal volume x Resp frequency
How is dilution used to measure lung volumes?
Vital capacity of helium mixture is inhaled
After inhalation and mixing with the residual volume, the helium concentration is diluted
Helium not taken by blood or lost from alveoli
Dilution of the helium enables the residual volume to be obtained
What is meant by lung compliance?
The increase in lung volume per unit increase in distending pressure measured statically
What is meant by lung elastance?
The reciprocal of lung compliance
What is the role of elastic recoil?
When muscles relax the energy stored in the elastic recoil is used to drive the air out
What is meant by airway resistance?
The pressure required to drive unit air flow through conducting airways
Look at the repsiratory cycle
zxx
What is dyspnoea?
Common respiratory complaint is breathlessness
What causes the breathlessness sense?
Increased work of breathing
What are the pulmonary causes of increased work of breathing?
Stiff lungs - compliance
Narrowed airways - increased AWR
Increased ventilation- minute volume
