Ventilation Flashcards
What makes up the respiratory membrane?
2 cell layers: alveoli and pulmonary capillaries
What sets the basic drive of ventilation?
Respiratory neurons in the brain stem
How do the respiratory neurons in the brain stem exert their control?
Descending neural traffic to spinal cord to activate muscles of respiration
Where can central chemoreceptors be found?
Brain stem
Where can peripheral chemoreceptors be found?
Aorta and carotid body
Golgi tendon organs are an example of what kind of receptors?
Mechanoreceptors
What specific respiratory centers are located in the brain stem?
Dorsal and ventral medullary group, pneumotaxic and apneustic centers
What can influence the respiratory centers in the brain stem?
Higher brain centers (voluntary control), peripheral mechanoreceptors, peripheral and central chemoreceptors
How do the respiratory centers in the brain stem affect ventilation?
Affect rate of depth of ventilation
Which is considered an active process: inspiration or expiration?
Inspiration
Which is considered a passive process: inspiration or expiration?
Expiration (under resting conditions…can be forceful sometimes which would be active)
Which group of muscles increases thoracic cage volume?
Inspiratory
Which group of muscles decreases thoracic cage volume?
Expiratory
What are the inspiratory muscles?
Diaphragm, external intercostals, SCM, anterior and posterior superior serratus, scalenes, levator costarum
What are the expiratory muscles?
Abdominals, internal intercostals, posterior inferior serratus, transversus thoracis, pyramidal
What is the function of the diaphragm?
Drops the floor of the thoracic cage during inspiration
Does the diaphragm lift the rib cage?
No (the rest of the inspiratory muscles do)
Which expiratory muscle plays an extra role in causing low back pain?
Transversus abdominis
Which is associated with recoil of the lungs: inspiration or expiration?
Expiration
What is the normal range of pleural pressure between the parietal and visceral pleura?
-5 and -7.5 (NEGATIVE!)
What is the purpose of having a NEGATIVE pleural pressure?
Keeps lung inflated against chest wall
What is the term for the difference between alveolar and pleural pressures?
Transpulmonary presssure
What does the transpulmonary pressure measure?
Recoil tendency of the lung
When does transpulmonary pressure peak?
At the end of inspiration
Alveolar pressure is subatmospheric during which: inspiration or expiration?
Inspiration (-1)
Alveolar pressure is supra-atmospheric during which:inspiration or expiration?
Expiration (+1)
Which is easier to inflate: saline-filled or air-filled lung?
Saline-filled
Why is it easier to inflate a saline-filled lung?
Surface tension forces have therefore been eliminated
What is pulmonary hysteresis?
The difference between the pleural pressure and lung volume at the onset of inspiration (pleural pressure changes at a faster rate)
Average breaths per minute?
12
Average total cycle length for breathing?
5 seconds
What is compliance?
Change of volume over the change in pressure
When is compliance greatly reduced?
At high or low lung volumes
What effect does the thoracic cage have on lung compliance?
Reduces it by about 50% around functional residual capacity (FRC) at the end of a normal expiration
What accounts for the majority of the work of breathing?
Compliance (elastic) work
What makes up the tissue resistance work?
Viscosity of chest wall and lung
How much total body energy is required for ventilation?
3-5%
What is the term for normal breathing and what are the average rates?
Eupnea
12-17 B/min, 500-600 ml/B
What is the term for when increased pulmonary ventilation matches increased metabolic demand (example = exercise)?
Hyperpnea
What is the term for when increased pulmonary ventilation is GREATER than metabolic demand?
Hyperventilation
What are CO2 levels like during hyperventilation?
Decreased (less than 40 mmHg)
What is the term for when decreased pulmonary ventilation is LESS than metabolic demand?
Hypoventilation
What are CO2 levels like during hypoventilation?
Increased (greater than 40mmHg)
What is the term for increased frequency of respiratory rate?
Tachypnea
What is the term for absence of breathing?
Apnea (example = sleep apnea)
What is dyspnea?
Difficult or labored breathing
What is orthopnea?
Dyspnea when recumbent, relieved when upright
In what clinical conditions can orthopnea occur?
Congestive heart failure, asthma, lung failure
What is the reason for the suction of the lungs against the chest wall that overcomes the natural tendency for the lungs to collapse?
Negative pleural pressure
Which has a greater impact on the lungs: surface tension forces or elastic fibers?
Surface tension forces (responsible for 2/3 of the collapse tendency of the lung)
What happens when the pleural space communicates with the atmosphere (example = Dr. Freedman stabbing you in the chest with a spear)?
Pleural pressure then equals atmospheric pressure and lung will collapse
What are the possible causes for lung collapse?
Puncture of parietal pleura
Erosion of visceral pleura
If major airway is blocked, air trapped distal to block will be absorbed by blood and that segment of lung will collapse
What is pleural fluid?
Few milliliters of a thin layer of mucoid fluid made of transudate (interstitial fluid and protein)
Excess pleural fluid is removed by lymphatics in what locations?
Mediastinum, superior surface of diaphragm, lateral surfaces of parietal pleura
How does the removal of excess pleural fluid affect pleural pressure?
Helps make it negative
What is pleural effusion?
Collection of large amounts of free fluid in pleural space (edema of pleural cavity)
What are possible causes of pleural edema?
Blockage of lymphatic drainage
Cardiac failure —> increased capillary filtration pressure
Reduced plasma colloid osmotic pressure
Infection/inflammation of pleural surfaces which breaks down capillary membranes
What effect does surfactant have on surface tension?
Reduces it
How does surfactant reduce surface tension?
By forming a mononuclear layer between aqueous fluid lining alveoli and air preventing a water-air interface
What produces surfactant?
Alveolar type II epithelial cells
What makes up surfactant?
Complex mix-phospholipids, proteins, ions, dipalmitoyl lecithin, surfactant apoproteins, calcium ions
What is the concept of interdependence when it comes to the size of one alveolus?
Determined by surrounding alveoli
What is the role of surfactant?
Prevents small alveoli from having increased collapsing potential
What is the relationship between alveolar size, concentration of surfactant, surface tension forces, and the radii of vessels?
All decrease as a unit thanks to surfactant (Law of LaPlace)
What is normally responsible for the majority of the collapse tendency of the lung?
Surface tension forces
