Physiological Consequences of Airway Obstruction Flashcards
What happens to breathing when there is airflow obstruction?
- increased sensation of breathing
- increased respiratory muscle effort
- active exhalation
- longer time to inspire
- longer time to exhale
- reduced maximum ventilation
- altered pattern of breathing
- sometimes gas trapping
What two factors influence work of breathing?
Load and Drive
What causes increased load?
stiff lungs, narrow airways, chest wall, diaphragm
What causes increased drive?
higher centres, mechanoreceptors, irritant receptors, chemoreceptors, baroreceptors, temperature
What is increase work of breathing?
Where there is an increased respiratory muscle effort
When is mechanical ventilation required?
if PaO2 is less than 60mmHg and PaCO2 is greater than 50mmHg
What are the consequences of increased work of breathing?
recruitment of accessory muscles of breathing, increased oxygen consumption by respiratory muscles, risk of respiratory muscle fatigue
What are the accessory muscles of breathing?
Sternocleidomastoid and scalenes
What happens to expiration in airflow obstruction?
It becomes active
What happens to inspiratory pressure in airflow obstruction?
Have to generate higher than normal inspiratory pressure
What is pulses paradoxis?
During airflow obstruction there is a need to generate greater intrapleural pressure which influences the systolic BP and brings it down
What happens to FEV1 and FVC in airflow obstruction?
FEV1 is decreased but FVC remains the same
What is the FEV1/FVC ratio which indicates airflow obstruction?
less than 70%
How can you tell if airflow obstruction is reversible?
By seeing if a bronchodilator/steroids improves the FEV1/FVC
What is a flow-volume loop?
A measurement of flow rate vs volume in forced inspiration and expiration - used to determine whether it is a lower airway obstruction or upper airway obstruction
