Chapter 37 - Pulmonary Ventilation Flashcards
Guyton, 5th Edition
Four major functions of respiration
- Pulmonary Ventilation
- Diffusion of O2 and CO2 between the alveoli and the blood
- Transport of O2 and CO2 in the blood and body fluids to and from the body’s tissue cells.
- Regulation of ventilation and other facets of respiration.
What are the 2 ways that the lung can expand and contract.
- Downward and upward movement of the diaphragm to lengthen or shorten the chest cavity.
- Elevation and depression of the ribs to increase and decrease the anteroposterior diameter of the chest cavity.
What happens to during inspiration of a normal quite breathing?
Contraction of the diaphragm pulls the the lower surfaces of the lungs downwards.
What happens during expiration of a normal quite breathing?
The diaphragm simply relaxes and the elastic recoil of the lungs, chest wall and abdominal structures compresses the lungs and expels the air.
What changes during heavy breathing?
The elastic forces are not powerful enough to cause the necessary rapid expiration, so that extra force is achieved by contraction of the abdominal muscles, which pushes the abdominal contents upward against the bottom of the diaphragm, thereby compressing the lungs.
What are the most important muscles that raise the rib cage?
External intercostas, (1) sternocleidomastoid muscles, which lift upward on the sternum, (2) anterior serrati, whch lift many of the ribs; and the (3) scaleni, which lift the first two ribs.
What are the muscles that pull the rib cage downward during expiration?
- Abdominal recti
2. Internal intercostals
What happens when there is no force to keep the lung inflated?
Collapses like a balloon and expels all its air through the trachea.
What is the Pleural pressure
The pressure of the fluid in the thin space between the lung pleura and the chest wall pleura; normally a slight suction, which means a slightly negative pressure.
What is the normal pleural pressure at the beginning of inspiration?
About -5 centimeters of water, which is the amount of suction required to hold the lungs open to their resting levels.
What is the normal pleural pressure at the during of inspiration?
Expansion of the chest cage pulls outwards on the lungs with greater force and creates more negative pressure to about -7.5 centimeters of water.
What is alveolar pressure?
Pressure of the air inside the lung alveoli.
How do you cause inward flow of air into the alveoli during inspiration?
The pressure in the alveoli must fall to a value slightly below atmospheric pressure (about -1 centimeters of water).
What is the Transpulmonary Presure?
The difference between the alveolar pressure and the pleural pressure.
What is lung compliance?
The extent to which the lungs will expand for each unit increase in trans-pulmonary pressure (if enough time is allowed to reach equilibrium).
What is recoil pressure?
The elastic force in the lungs that tend to collapse the lungs at each instant of respiration.
What is the total compliance of both lungs together in the normal adult human being?
200 milliliters of air per centimeter of water trans-pulmonary pressure.
What are the components of the compliance diagram of the lungs?
Two curves:
- Inspiratory compliance curve
- Expiratory compliance curve
What are components of the elastic forces of the lungs?
- Elastic forces of the lung tissue
- Elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lungs air spaces.
What are the elastic components of the lung tissue?
Elastin and collagen fibers interwoven among the lung parenchyma.
What is a surfactant?
A surface active agent in water, which means that it greatly reduces the surface tension of water.
What secretes surfactants in the alveoli?
Type II alveolar epthelial cells. Constitutes about 10% of the surface area of the alveoli.
What are the molecular components of the surfactant?
Dipalmitoylphosphatidylcholine (the one responsible for reducing the surface tension), surfactant apoproteins, and calcium ions.
Surface tension of pure water, normal fluid lining the alveoli w/o surfactant; and normal fluid lining the alveoli w/ surfactant.
72 dynes/cm; 50 dynes/cm; 5-30 dynes/cm.
What is the formula to calculate the Pressure inside the alveolus?
2 x Surface Tension
__________________
Radius
= Surface tension of the alveoli is inversely affected by the radius of the alveolus, which means that the smaller the alveolus, the greater the alveolar pressure caused by the surface tension.
What is the radius of the average-sized alveolus and its pressure with and w/o surfactant?
About 100 micrometers. Lined with normal surfactant, about 4 centimeters of water pressure (3mmHg). Without, about 18 centimeters of water pressure; about 4.5 times greater.
What causes Respiratiory distress syndrome of the newborn?
The smaller raidus of the alveoli and the small or absence of secretion of surfactants.
The work of inspiration can be divided into three factions:
- Compliance or Elastic work
- Tissue resistance work
- Airway resistance work
What is Compliance or Elastic work
The work required to expand the lungs against the lung and chest elastic forces