L2. Respiratory physiology Flashcards
Define function of respiration
- to extract oxygen from the air and together with the cardiovascular system transport it to respiring tissues
- To remove carbon dioxide from respiring tissues (and endproduct of aerobic metabolism) and exhaust into atmosphere.
What are the evolutionary drivers for respiratory system development
Increase in the size, diffusion distance, metabolic rate and oxygen demand.
What are the main muscles for Inspiration and Expiration (except accessory respiratory muscles)
Insp: diaphragm (70%)
External intercostal muscles
Exp: internal intercostals, and abdominal muscles
Which is active process: Expiration or inspiration
Inspiration = active using muscles Expiration = passive (at rest through relax of muscles and recoil) However during exercise/talking/forcing it becomes active to increase breathing speed.
What are the pulmonary and pleural pressure changes during the respiratory cycle
Just before inspiration: Ppl = -3, Ppul= 0.
In inspiration: The chest volume increases as the diaphragm contracts downwards. Ppl more negative (-6) and Ppul becomes negative (-2) so atmospheric air goes inside before gaining pressure as air enters the lungs (back to 0)
In expiration: The inflation of the lungs/relax of muscles in the chest leads to decreased volume= Ppl increase back to -3.
Ppul increases above 0 to +2 so air moves back to atmos until there is less air in the lungs and it slowly drifts back to 0
Why does air move from one place to another
They move from a high pressure to a low pressure (relative to atmospheric)
What is the difference between Pneumothorax and Atelectasis
Both are about lung collapse. Atelectasis is an intrinsic problem due to insufficient air in the lung, due to airway obstruction or surfactant deficieny. Pneumothorax is extrinsic problem due to puncturing there is loss of negative pleural pressure as air rushes into the chest and therefore the lung cannot inflate.
What is a spirometer and what does it measure.
An inner cylinder with gas is floating ontop of an outer cylinder of water. Breathing into the tube connected to the inner cylinder makes it bob up and down and this motion is recorded on the recording drum- this is for volumes. If inner cylinder filled with oxygen & co2 removal molecule can also measure O2 consumption
What does the Spirometer measure and not measure
It measures Tidal volume, respiratory frequency, minute ventilation, inspiratory reserve volume, expiratory reserve volume.
Cannot measure capacities directly and cannot measure residual volume.
How is residual volume measured
He in the inner cylinder before breathing in (C1V1) is compared to C2 (V1 + V2) after breathing/equilibration has started where V2 is the Total lung capacity.
V2= V1 (c1-c2)/ c2
Then Total lung capacity - Vital capacity = residual volume.
What are the changes to lung volumes during increased demand (exercise)
Depth and frequency of breathing (TV) increases:
Area above and below TV decreases; IRV and ERV. Because of additional muscles, force.
How do you calculate minute ventilation and what is average values, and range for hyper and hypoventilation
TV x f ( breaths/min) = minute Ventilation (V/min)
(Also known as minute vent= alveolar + dead space vent)
0.5 L x 12 breaths/min= 6L/min
Hyper : >6 L/min, Hypo: <6 L/min
How do you calculate Alveolar ventilation (taking into consideration of dead space in the airways)
Alveolar ventilation = minute ventilation - dead space ventilation (2.2mL/kg)
Calculated by taking off the dead space from the tidal volume x breaths/min.
What is the difference between FEV1 and FVC and what measures this
FEV = the volume of air expired in 1 second whereas FVC is the total volume of air during forced expiration.
Vitalographs measure this
What is the clinical significance of FEV1 and FVC
FEV1/FVC ratio helps to differentiate between obstructive (eg. COPD) diseases and restrictive diseases (eg. pneumonia)
Normally this ratio is 80% with FVC only a little bit more than FEV1.
However for Obstructive diseases the FEV1/FVC ratio is decreased, with FEV1 decreased more than FVC.
In Restrictive diseases, the FEV1/FVC ratio is normal or increased. FVC is decreased more than FEV1 (although both have decreased).
