Lecture 13 - Overview of respiratory pathology and lung pressures Flashcards
What is respiration?
The exchange of O2 and CO2 between the tissues and the environment
What are the steps of respiration?
1) Ventilation: Process of moving air into and out of the lungs
-supply O2 to and remove CO2 from the alveoli BULK FLOW
2) Gas Exchange: Exchange of O2 and CO2 across alveolar membrane
(air to blood i.e. into body). DIFFUSION
3) Gas transport: Deliver O2 from lungs to tissues and and transport CO2
produced by metabolism to lungs. (Cardiorespiratory) BULK FLOW
4) Gas Exchange: Exchange of O2 and CO2 between the capillaries and
the cells DIFFUSION
5) Cellular respiration: Cells use O2 and produce CO2
METABOLISM
What are the functions of the respiratory system? (8)
Provide oxygen
Eliminate carbon dioxide
Filters, warms and humidifies the air we breathe
Communication
Sense of smell
Regulate the pH of the blood, in association with the
kidneys
Defend against microbes
Temperature regulation
What occurs during restful inspiration?
Diaphragm contraction
What occurs during restful expiration?
lung elastic recoil which pulls thorax and relaxed diaphragm inwards.
No muscle contraction, therefore “passive”
What occurs during deep inspiration?
diaphragm and external intercostal
muscle contraction
What occurs during deep expiration?
lung elastic recoil and internal
intercostal muscle contraction
What occurs during forceful inspiration?
diaphragm and external intercostal
muscle contraction plus contraction of
sternocleidomastoid and pectoralis minor
muscles
What occurs during forceful expiration?
lung elastic recoil and internal intercostal muscle contraction plus abdominal muscle contraction
What does the pleurae do?
The Pleurae form an envelope between the lungs & chest wall - Double membrane area
Attaches lung to chest wall - allow lung to move with chest
From deep to superficial, what are the lung pleura?
Visceral Pleura
Parietal Pleura
What does the parietal pleura do?
lines inside of chest wall &
diaphragm
What does the visceral pleura do?
lines outside of lungs
What is the pleural cavity?
slit-like potential space filled with pleural fluid
What is ventilation?
Ventilation is the exchange of air between the atmosphere and alveoli
What is bulk flow (F) proportional to?
Bulk flow (F) is proportional to pressure difference (DP)
between two points and inversely proportional to the
resistance (R).
What are the P when F=0
Palv = Patm
What is needed to generate flow in ventilation?
a PRESSURE gradient - Create a pressure difference (gradient)
between lung (Palv) and atmosphere (Patm)
How can we create a lung pressure gradient?
changing lung volumes
What is Boyle’s law?
At constant temperature, the volume of a
gas varies inversely with absolute pressure.
What happens to pressure during inspiration?
During inspiration –
volume of lung (container)
is increased – decreased
pressure
What happens to pressure during expiration?
During expiration – volume
of lung (container) is
decreased – increased
pressure
What are the determinants for the changes in lung dimension?
• Difference in the pressure between the inside and outside of the lung - transpulmonary pressure (Ptp or PL )
• Stretchability of the lungs (compliance) – how much the lungs expand for a given change in Ptp
What governs the static property of the lung?
Transmural pressure
What does transmural pressure resist?
Transmural pressure resists the elastic
recoiling of the lung
What is transpulmonary/transmural pressure defined by?
Ptp = Palv-Pip
What is the relation between Ptp and lung size?
Lung requires positive Ptp to increase its volume
Lung assumes smallest size when Ptp is zero
What is required to achieve stable balance between breathes and why?
Positive Ptp
Lung has the tendency to recoil
inwards and chest wall tends toexpand outwards
To keep the lungs open Ptp should be positive – which opposes elastic
recoil
How can we have postive Ptp?
For Ptp to be positive Pip should be negative
How can we have a negative Pip?
When the lung collapses and chest wall expands, there is a very minimal expansion in the fluid-filled intrapleural space.
As the fluid cannot expand like air, even this small increase in the pressure creates subatmospheric (negative) intrapleural pressure (Pip).
