Respiration - Lecture 6 Flashcards
What does the chest wall include?
the rib cage, diaphragm and the abdominal wall
What happens to the visceral pleura when the lungs fill the chest?
it comes in contact with the parietal pleura
How do the lung and chest operate together?
in series with one another
Are the lungs directly attached to the chest wall?
no
How are the visceral and parietal pleura coupled together?
by a thin layer of liquid that fills 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
At rest, what sign is the pleural pressure?
negative
Why is the pleural pressure negative at rest?
because of the opposing forced acting on the lung and the chest wall
What happens if a hole is punctured through the chest wall?
the lungs collapse and the chest springs outwards (pneumothorax)
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
How are pressures measured for the respiratory system?
manometers or pressure transducers
What does “negative pressure” indicate?
a pressure below atmospheric pressure
What does “positive pressure” indicate?
a pressure above atmospheric pressure
What is the recoil pressure defined as?
the pressure difference between the inside and outside of the structure
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
Prs = Pl + Pw
How can we calculate Pbs?
Pbs = Ppl - Pw
How can we calculate the Palv?
Palv = Pl + Ppl
What is the compliance of the lungs?
a parameter that refers to the ease with which each of these structures can be distended
What is the procedure for measuring the respiratory system compliance?
determine the static pressure-volume relationship while lung volume is decreased step by step from TLC
How is compliance expressed?
as the volume change in the lungs for a unitary change in pressure
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?
the pressure required to maintain the lungs at a given inflation volume against their tendency to recoil elasticity
What is the formula for compliance of the lungs?
Cl = V / (Palv - Ppl)
How is the elastic recoil of the lungs produced?
by the elasticity of the lung tissue
How do a large part of the recoil forces arise from?
the properties of the liquid film lining the inside of the lungs
What is the formula for elastic recoil?
El = (Palv - Ppl) / V
How is the elastic recoil of the lungs produced?
by the elasticity of the lung tissue
How do some recoil forces arise from other than the elasticity of the lung tissue?
from the liquid film lining the inside of the lungs
Why does the liquid film lining the inside of the lungs generate substantial force?
because the surface area of the film is very large
What also has elastic properties that cause it to recoil either inward or outward, depending on its volume?
the tissues of the thorax
What is the compliance of the thoracic defined as?
a change in thoracic volume and a change in pressure across the chest wall
What is the formula for the compliance of the chest wall?
Cw = V/ Ppl
What is the sign of the pressure reported when measuring the compliance of the lungs?
positive
When does the chest wall tend to collapse?
only after reaching a volume after 60% vital capacity
What is the sign of the pressure in the chest wall?
sometimes positive sometimes negative
What is the Prs at FRC?
zero
Why is the Prs zero at FRC?
because the system is at rest
What causes the stable condition of the Prs at FRC?
the inward recoil of the lungs (Pl is about +5 cmH2O) which is balanced by the outward recoil of the chest wall (Pcw is about -5 cmH2O)
At FRC, how are the lungs and chest?
the lungs are above their resting volume and the chest is below its resting volume
Why does air enter the pleural space during pneumothorax?
because Ppl is less than atmospheric pressure
What happens to the lungs during pneumothorax?
they collapse to their resting position below RV
What happens to the chest wall during pneumothorax?
it expands towards its resting position at 60% total lung capacity
Why is pneumothorax a life-threatening emergency?
because the lungs are uncoupled from the chest wall
