Respiration lecture 6 Flashcards
What does the chest wall include?
the rib cage, diaphragm and abdominal wall
Explain how information travels from the brain to allow breathing
The brain sends a signal to the respiratory muscles, the muscles move the rib cage. The rib cage pulls the parietal pleura, which pulls the visceral pleura. Finally, the visceral pleura pulls on the lungs to make them expand.
Are the lungs directly attached to the chest wall?
No
How are the visceral and parietal pleura coupled together?
It’s a continuous membrane attached to the chest wall and the lungs to move together. In between, there is a small amount of liquid in the intrapleural space
What is the function of the liquid inside the intrapleural space?
it allows the lungs to slide against the internal wall of the chest during breathing and to follow the change in thoracic configuration
What is pleural pressure?
the pressure that can be measured in the liquid-filled space between lung and chest
What happens if a hole is punctured through the chest wall?
Air is going to enter the pleural space. The ribs are going to expand to their resting volume and the lungs will collapse to their resting volume
What do we measure to evaluate the elastic properties of the respiratory system?
changes in the recoil pressure of each separate structure for a given change in lung volume
Measures the tendency of the lungs to return to their original shape after inflation. (opposite of compliance)
How are pressures measured for the respiratory system?
manometers or pressure transducers
How are volumes measured for the respiratory system?
Spinometry
What does “negative pressure” indicate?
pressure below the atmospheric pressure
What does “positive pressure” indicate?
Pressure above the atmospheric pressure
What is the recoil pressure defined as?
the pressure difference between the inside and outside of the structure, driving those structure to return to their resting positions
What is the trans-chest-wall pressure?
the difference between the pleural pressure and the pressure at the body surface
How can we measure pleural pressure?
using a flexible balloon introduced into the esophagus
Why does esophageal pressure provide a close approximation of pleural pressure?
because the esophagus is located between the two pleural spaces
What is the formula for trans-chest-wall pressure?
Pw = pleural pressure - body surface
How is the transpulmonary pressure measured?
Pl = Palv - Ppl
How is the transrespiratory system pressure measured?
Prs=Palv-Pbs
How can we calculate Pbs?
That is the pressure around the body (=0 in lab)
How can we calculate the Palv?
You ask the patient to hold their breath at maximum lung capacity and close their mouths. The pressure inside their mouth will be equal to their alveolar pressure
What is the compliance of the lungs? (Definition)
the ease with which the structure can be distended
What is the procedure for measuring the respiratory system compliance?
Determine the static pressure-volume relationship while the lung volume is decreased step by step from the TLC
How is compliance expressed?
C=ΔV / ΔP
When is compliance of the lungs altered?
in diseases such as emphysema and fibrosis
The pressure required to maintain a given volume of gas inside the lungs ___ as the volume increases
increases
What is the pressure difference between the alveoli and the pleural space?
it gives transpulmonary pressure
What is the formula for compliance in the context of the lungs?
CL = ΔV/ (Δ Palv - Δ Ppl)
How is the elastic recoil of the lungs produced?
The elastic recoil of the lungs is produced by the inherent elasticity of lung tissue and the surface tension within the alveoli. The lungs naturally retract inward after being stretched during inhalation.
Where do a large part of the recoil forces arise from?
from the surface tension at the air-liquid interface within the alveoli and the elasticity of the lung tissue
Why does the liquid film lining the inside of the lungs generate substantial force?
surface tension pulls the alveoli inward, contributing to the lungs’ elastic recoil and creating a tendency for the alveoli to collapse
(counteracted by surfactant to maintain alveolar stability.)
What also has elastic properties that cause it to recoil either inward or outward, depending on its volume?
The chest wall also has elastic properties and they depend on the pressure
What is the compliance of the chest wall defined as?
the change of the thoracic volume and a change in pressure across the chest wall
What is the formula for the compliance of the chest wall?
Cw = ΔV/ΔPpl
What is the sign of the pressure reported when measuring the compliance of the lungs?
The pressure in the lungs is always positive (wants to collapse) no matter the % of the vital capacity (volume of air in the lungs)
see the curve on slide 14
What is the sign of the pressure in the chest wall?
When exhaling, the pressure in the lungs is negative (it wants to expand) because the lungs are below their resting volume
When inhaling, the pressure in the lungs is positive (it wants to collapse) because the lungs are above their resting volume
see the curve on slide 19
What is the Prs at FRC?
zero
Why is the Prs zero at FRC?
There is no airflow because the lungs are at rest between breaths. With no airflow, the pressure at the airway opening (Pao) and the pressure in the alveoli (Palv) are equal.
What causes the stable condition of the Prs at FRC?
Outward recoil of the chest wall: The chest wall naturally recoils outward due to its structural elasticity, creating a negative pressure in the pleural space.
Inward recoil of the lungs: The elastic tissue of the lungs pulls inward, attempting to collapse the lungs, creating an equal but opposite pressrue to the chest wall.
Why does air enter the pleural space during pneumothorax?
because the pleural pressure is less than the atmospheric pressure. The gradient is into the pleural space
What happens to the lungs during pneumothorax?
they collapse
What happens to the chest wall during pneumothorax?
it expands
Why is pneumothorax a life-threatening emergency?
because you can’t breath anymore… that’s not very compatible with life
