Normal Mechanism of Breathing Flashcards
Understand what is 'normal' (17 cards)
What is the normal Resp rate?
Along with the inhalation:exhalation (I:E) ratio?
Normal respiration occurs 12-15x per minute
The normal I:E ratio is 1:2
What are the muscles of inspiration and their function?
Ext intercostals - encourage lateral expansion of ribcage
Scalenes and Sternocleidomastoid pull rib cage up
Diaphragm contracts and flattens (from dome shape)
What are the muscles of expiration and their function?
Int intercostals - pull rib cage down and in
Abdominals (Ext oblique, Rec Abdominal, Int Oblique, TrA) - encourage diaphragm back to dome shape
Summarise the Pump Handle, Bucket Handle and Caliper motion of the rib cage.
Pump Handle: 1st-5th rib, increases the anterior-posterior thoracic volume by elevating the ribs
Bucket Handle: 6th-10th ribs, increases lateral thoracic volume through lateral expansion
Caliper: 11th+12th ribs, increases lateral and transverse volume but with no anterior attachment
Summarise the Pleura (Visceral, Parietal and Intrapleural space)
Visceral pleura surrounds the lung tissue and the Parietal pleura attaches with the thoracic cavity wall. Between the serous membrane there is pleural fluids which lubricates layers and facilitates sliding. The pressure of the pleura is less than that within the lung meaning the lunge tissue ‘sticks’ to the pleura. (Boyle’s law)
Summarise Boyle’s Law?
Pressure exerted by gas is INVERSELY proportional to the volume of container (as long as temperature is maintained).
Summarise what Lung Compliance is?
Change in volume / Change in Pressure
Compliance refers to the lung tissues ability to stretch and expand during breathing (inhalation). Compliance is influenced by two different factors:
-Elasticity of lung tissue (elastase - elastin)
-Surface Tension
What changes to Compliance may we see with both COPD and Pulmonary Fibrosis?
COPD: Increased compliance, meaning increases to pressure will have dramatic increases to volume. Likely able to inhale air in but have difficulty to exhale.
Pulmonary Fibrosis: Decreased compliance, difficult to expand with an increased elastic / recoil. Difficulty with inhalation but able to exhale air.
What happens to Alveolar Pressure during inhalation?
Increases to thoracic cage volume results in an increased alveolar volume which leads to a relative drop in alveolar pressure (Boyle’s law). Air moves in from atmosphere through the lungs to equalise the gradient.
Alveolar pressure then equals the atmospheric pressure and movement of air stops.
Gas exchange then occurs in the alveoli
What happens to Alveolar Pressure during exhalation?
Inspiratory muscles + diaphragm relax, the thoracic cage descends and lungs recoil which in turn results in decreased thoracic volume and increases the alveolar pressure.
Air moves out into the atmosphere to equalise the pressure.
Alveolar pressure equals atmosphere pressure and movement of air stops.
Summarise Poiseuille’s Law in terms of Respiration and what affects air flow?
Poiseuille’s Law helps us understand how easily air moves through these airways.
Air flow is influenced by three factors:
- Length of airway
- Diameter of the airway
- Viscosity of Gas
In healthy lungs, air flows easily.
But in narrowed or inflamed airways, airflow drops sharply — because of the powerful effect of airway radius in Poiseuille’s Law.
Talk through the lobes of the lungs 🫁 (top to bottom)
Right lung has 3 lobes:
Superior, middle (separated by horizontal fissure) and inferior lobe (separated by oblique fissure)
Left lung has 2 lobes:
Superior and inferior lobes (separated by oblique fissure)
On a NEWS chart, what respiration rate would begin scoring as too high?
20 or above.
Name two common conditions which could affect the Pleura?
Pleural Effusion (fluid within pleura)
Pneumothorax (air trapped within pleura)
What pressure changes have to occur to allow normal inspiration?
Negative pressure gradient within the thorax
Where in the brain is the respiratory / inspiratory system?
Breathing can be both an autonomic and voluntary process. Respiratory centre is located in the medulla and pons. Activity of these brain centres (and subsequent resp rate) is regulated by pH of CSF.
What happens when PaCO2 increases to the CSF?
Increases in PaCO2 result in reduced pH levels in the CSF. Central chemoreceptors detect this change in pH (acidosis) and regulate respiration to counter this.
