Week 7 - Respiration during Exercise Flashcards
What is the primary purpose of the respiratory system?
to maintain arterial blood-gas homeostasis
How does the respiratory system maintain arterial blood-gas homeostasis? (4-step process)
- Pulmonary ventilation
- Alveolar gas exchange
- Gas transport
- Systemic gas exchange
Oxygen rich air breathed in from the atmosphere whilst CO2 rich air is expired (pulmonary ventilation).
Oxygen the moves into the blood from the alveoli (alveolar gas exchange).
Blood containing 02 is then transported around the body (gas transport) where oxygen moves into systemic cells, such as muscles (systemic gas exchange).
How can we separate the structural organization of the respiratory system?
The upper and the lower respiratory tract separated by the epiglottis.
What does the upper respiratory tract include?
Nose, nasal cavity and the pharynx
What does the lower respiratory tract include?
airways - larynx, trachea, bronchus, bronchioles, terminal bronchioles
How is the functional organization of the respiratory system divided?
Conduction zone and respiratory zone
What is the role of the Conduction zone?
conducts air in and out the lungs - includes nose to the terminal bronchioles
Where do we define the end of the conducting zone?
16th airway generation which is the terminal bronchioles
What is the difference between the conduction zone and the respiratory zone of the respiratory system functional organization?
The respiratory zone contains alveoli which is where gas exchange takes place.
What is the role of the respiratory zone?
its where the transport and diffusion of gases along the pulmonary (lung) capillary takes place with 02 moving into arterial blood and C02 moving out.
Match the key term to the description.
Key terms: parietal pleura, visceral pleura, pleural cavity.
a) outside of the pleural cavity
b) deepest layer which covers the lungs directly
c) area that contains small amounts of fluid which prevents friction when the lungs move and expand
a) visceral pleura
b) pleural cavity
c) parietal pleura
Intrapleural pressure < atmospheric pressure, what does this prevent?
the alveoli from collapsing
What are the lungs enclosed within?
membranes called pleura
How many airway generations are there?
23
Where does gas exchange occur?
in the respiratory zone (Z17-23)
In terms of airways, where does the conducting zone start and extend to?
starts at the main bronchi (Z1) and extends to the terminal bronchioles (Z16)
- large conductors
- resistance higher
How many alveoli does the human lung contain?
300-500 million - each 1/3mm in diameter
Where does pulmonary gas exchange take place across?
the pulmonary capillary
- very thin and vast surface area which makes it ideal for gas exchange/diffusion
How does oxygen and carbon dioxide move between air (alveoli) and blood?
by simple diffusion (from high to low partial pressure)
- Oxygen moves from alveoli to pulmonary artery
- Carbon dioxide moves from venous blood to alveolus (to then expire).
Explain the two types of alveolar cell (pneumocytes).
Type 1 cells cover 95% of the internal surface of the alveolus and are critical for gas exchange.
Type II cells release surfactant - a molecule that lowers the surface tension (like soap) and prevents the alveoli collapsing.
What is the volume of gas passing through a sheet dependent upon?
- Surface area (A)
- Thickness (T)
- Diffusion coefficient (D)
- Pressure gradient (alveolar to arterial)
What is Fick’s law of diffusion?
Rate of diffusion is proportional to SA/thickness x diffusion coefficient x pressure gradient
What are the 5 layers of the pulmonary capillary that gas has to diffuse across (from alveolus) in order to enter the erythrocyte?
- Surfactant
- Alveolar epithelium
- Interstitium
- Capillary endothelium
- Plasma
What are the mechanisms of breathing concerned with?
the movement of air into and out of the lungs by changes in pressure (contraction force), flow (contraction velocity), and volume (contraction length)
What happens during inspiration?
Volume of thoracic cavity increases as the respiratory muscles contract.
What are the 3 dimensions that the thoracic cavity increases during inspiration?
1) Vertical changes: diaphragm contracts and flattens which increase vertical diameter of thoracic cavity
2) Lateral changes: bucket handle of the ribs –> ribs are elevated and thoracic cavity widens.
3) Anterior-posterior changes: pump handle motion –> inferior portion of sternum moves anteriorly and thoracic cavity expands
At rest, what is diaphragm contraction responsible for?
the majority of pulmonary ventilation
During exercise, what happens to pulmonary ventilation? What is the diaphragm assisted by?
It increases 10-20-fold above resting levels. It’s assisted by the external intercostal muscles, scalenes, sternocleidomastoid and other muscles to increase pulmonary ventilation.
How does expiration differ at rest and during exercise?
At rest, expiration is passive. Whereas during exercise, expiration becomes active by contraction of the rectus abdominis, internal intercostal muscles and extreme oblique.
How many respiratory muscles are there?
> 60
What is a gold standard way of measuring diaphragm fatigue?
Bilaterial phrenic nerve stimulation - non-volitional measure
Ohm’s law - applied to respiratory system
Airflow is dependent upon a pressure gradient and airway
resistance.
Flow = change in pressure/resistance
(Current = voltage/resistance, applied to breathing)
Poiseuille’s law
o Resistance is dependent upon length and radius of a tube
o Radius is raised to the fourth power, thus the major
determinant of airway resistance
How does mechanics of breathing differ during exercise for a person with asthma?
- % of tidal volume that is flow limited is much greater at much lower intensities
- they increase their end expiratory lung volume to prevent flow limitation
What is dead space volume? What is the volume of dead space in healthy individuals?
The volume of air not participating in gas exchange (per breath) + 150ml and this doesn’t change during exercise.
How would you work out dead space ventilation?
Dead space (0.15L/150ml) X breathing frequency
Tidal volume
volume of air per breath
Minute ventilation
volume of air breathed per minute (tidal volume x breathing frequency)
Breathing frequency
number of breaths per minute
Forced vital capacity (FVC)
the maximum volume air that can be forcefully expired after a maximum inspiration
How can we diagnose pulmonary diseases such as COPD?
Spirometry can be used to diagnose COPD.
FEV1/FVC <0.7 is indicative of COPD and airway obstruction.
FEV1 - forced expiratory volume in one second
FVC - forced vital capacity
What is COPD characterized by?
- Increased airway resistance
- Reduced FVC (forced vital capacity)
- Higher residual volume
- Increase end-expiratory lung volume (EELV) during exercise
- Increased work of breathing
- Breathing discomfort
What is resistance mainly determined by?
airway diameter
What is alveolar volume?
tidal volume - dead space volume
What is alveolar ventilation?
(tidal volume - dead space volume) x breathing frequency
The amount of air breathed every minute that takes part in gaseous exchange.
Is it more efficient to increase tidal volume or breathing frequency?
tidal volume - this is because we get dead space per breath so increasing breathing frequency increases dead space ventilation
Total lung capacity
volume of air in the lungs upon maximum inspiration
(vital capacity plus residual volume)
What volumes make up total lung capacity?
tidal volume
inspiratory reserve volume
expiratory reserve volume
residual volume
Difference between volume and capacity?
Volume - one segment
Capacity - two or more segment
