Respiratory Physiology Flashcards
What is pulmonary ventilation measured in
Litres/ minute
What is minute ventilation (VE)
The volume of air brought into and out of the lungs per minute
How do you calculate minute ventilation
Volume of air moved per breath x number of breaths per minute
What is spirometry
A method used to monitor the amount of and/ or speed of movement of air that can be inhaled and exhaled
What tidal volume
Volume of air moved per breath
What is the conducting zone
The anatomic dead space where air does not reach the alveoli so no gas exchange occurs here
What is the average volume of air in the conducting zone
150-200ml or about 30% of tidal volume
What is alveolar ventilation
The amount of air reaching the alveoli
What makes up the conducting zone
Trachea, primary bronchus, bronchus, bronchi, bronchioles
What makes up the respiratory zone
Respiratory bronchioles, alveolar ducts and alveolar sacs
Why does total minute ventilation not equate to alveolar ventilation
As not all the air we breath in reaches the alveoli, some remains in the conducting zone
How is alveolar ventilation calculated per breath
Tidal volume- conducting zone volume
How is alveolar ventilation calculated per minute
Minute ventilation- minute dead space ventilation
What happens to alveolar ventilation during shallow breathing
Decreases as air enters and leave conducting zone without reaching respiratory zone
What is inspiratory reserve volume (IRV)
The volume of air brought into the lung after normal inspiration
How is IRV measured
1) inhale normally
2) inhale as deeply as possible
3) difference in volume= IRV
What is the expiratory reserve volume (ERV)
The volume of air brought out of the lung after normal expiration
How is ERV measured
1) Exhale normally
2) exhale as much as possible
3) difference= ERV
What is forced vital capacity
Maximum air expired after maximum inspiration
What is the residual lung volume
The volume of air in the lungs after max expiration
Why is residual lung volume important
Key for continuous gas exchange as if this did not exist the alveoli would collapse
What are the dynamic lung volumes
Dynamic ventilation and airflow velocity
What is dynamic ventilation
Ventilation constrained by time
What does dynamic ventilation depend on
Maximum lung volume (FVC), airflow velocity
What is airflow velocity
The speed of moving a volume of air
What does airflow velocity depend on
Resistance of respiratory passage and compliance if the chest and lung tissue
What is airflow directly proportional too
Pressure gradient
What is airflow inversely proportional to
Airway resistance
What are obstructive pulmonary disorders
A disorder that obstructs airways so resistance is increased and airflow limited
What are restrictive pulmonary disorders
Disorders that restrict the compliance of the chest wall, limiting airflow
What is FEV1
Forced expiratory volume in one second after max inhale
What is maximum voluntary ventilation
The amount of air that can be moved in and out of the lungs in one minute (a measure of dynamic lung volume)
How is maximum voluntary ventilation measured
1) breathe as quickly and deeply as possible for 15 seconds
2) extrapolated to one minute
Why does pulmonary minute ventilation increase during exercise
Increase in tidal volume and breath frequency
Does tidal volume limit FVC in healthy individuals and why
No as tidal volume is only around 50-60% of FVC so other factors must be limiting
How does ventilation increase during exercise
Diaphragm descends more and lung volume increases more due to more frequent and forceful contractions,
larger pressure gradient, airways dilate so decreased airway resistance so faster airflow
Why does gas exchange increase during exericse
Increased cardiac output to lungs, muscles use more oxygen and produce more CO2 during exercise so lower PO2 and higher PCO2 so higher pressure gradient
What is the transit time
The length of time a RBC remains within a pulmonary capillary
Why is a shorter transit time during exercise not a limiting factor of exercise capacity
As there is still enough time for gases to equilibrate between the alveoli and blood
What is the feedforward mechanism that causes ventilation to increase during exercise
Neural outflow from the brain in anticipation of exercise
Describe how neural outflow from the brain in anticipation of exercise causes an increase in ventilation
Exercise initiation stimulates respiratory neurons in the medulla to initiate an increase in ventilation abruptly
What are the feedback mechanisms that cause an increase in ventilation during exercise
Chemoreceptors detect partial pressure of gases and pH in blood, sensory input from sensory receptors (proprioceptors) in joints, tendons and muscles and stretch receptors in the airways
What mechanism causes the initial rapid increase of ventilation at the start of exercise
Feedforward mechanism via central command
What causes the continued increase in ventilation as exercise continues
Combined feedforward and feedback mechanisms
