Respiratory Mechanics II And III Flashcards
What are 4 characteristics of respiratory skeletal muscles
1) Most used skeletal muscles
2) Only skeletal muscles necessary for life
3) Under both involuntary and voluntary control
4) Do not work to overcome inertia, and instead elastic (costal cartilages, lung parenchyma) and resistive (airway resistance, tissue viscosity) loads
Amount of force produced by respiratory muscles is determined by what 2 things:
1) Force-length relationship: Length of muscle when its contracted
2) Force-velocity relationship: How fast muscle needs to contract
What are the 2 components of total muscle force?
1) Active muscle contraction
2) Passive stretch of elastic components
Describe 3 characteristics of the length-tension curve of a muscle
1) Maximum active tension is generated at resting length
2) Passive tension increases exponentially beyond resting length
3) Total muscle forces increases in a lengthened position because passive tension compensates for loss of active tension as the length of the muscle increases
Describe this image in regards to active tension
1) Increased overlap
2) Overlap is optimal
3) Reduced overlap
4) Almost no overlap
**Muscles cannot produce as much active tension when in a shortened or lengthened position due to loss of optimal overlap
Describe the force-length relationship in the diaphragm and how it is different from regular skeletal muscle
Diaphragm can generate more active tension than limb skeletal muscle to generate force
Describe how radius curvature impacts the diaphragm
If we increase the radius and the tension stays the same then the pressure will decrease. Therefore a more flattened diaphragm will generate less pressure (force).
**Look at Laplace’s law formula in picture
List 5 important characteristics about the length of the diaphragm
1) Length of diaphragm is most important determinant of contractile force
2) The diaphragm generates more force when more sharply curved
3) If the diaphragm is higher in the thorax it has an increased curvature and length
4) If the diaphragm is lower in the thorax it has a decreased curvature and length
5) The diaphragm can generate active tension over a broad range of lengths
Terminology: Force (skeletal muscles) means what in respiratory muscles
Pressure (force/surface area)
Terminology: Length (skeletal muscles) means what in respiratory muscles
Lung volume (overall change in muscle length)
Terminology: Velocity (skeletal muscles) means what in respiratory muscles
Air flow ( overall volume/overall time)
Describe the volume-pressure (Force-length) relationship of the lungs
1) Increases in lung volume towards total lung capacity results in inspiratory muscles to shorten (agonists) and expiratory muscles to lengthen (antagonists) -> expiratory muscles generate maximum pressure at total lung capacity
2) Decreases in lung volume towards residual volume results in expiratory muscles to shorten (agonists) and inspiratory muscles to lengthen (antagonists) -> inspiratory muscles generate maximum pressure at residual volume
Coughing is produced by
Forceful contraction of expiratory muscles
When teaching a patient how to cough, what is the first step to maximize force (pressure)?
Since expiratory muscles generate max pressure at total lung capacity, we want the patient to take a deep breath in to produce the strongest cough
An [increase/decrease] in velocity = an [increase/decrease] in force (muscle)
Increase in velocity = decrease in force
Describe the maximum pressure (force) if respiratory muscles in terms of velocity
As max pressure of respiratory muscles decreases, the velocity flow increases.
Power =
Force x Velocity
List 3 characteristics of the force-velocity relationship
1) Respiratory muscles have variable inspiratory flow and speed of contraction (eg. sleep vs exercise)
2) To optimize power, there are multiple muscles of inspiration/expiration
3) We increase power and flow by progressive recruitment (increases max velocity without a loss of force)
When do our inspiratory muscles have an advantage?
When taking a deep breath out when at minimum lung capacity
When do our expiratory muscles have an advantage?
When taking a deep breath in when at maximal lung capacity
What are 3 characteristics of the diaphragm
- Separates thoracic and abdominal cavities
2) It is made of a costal and crural muscles that are connected by a central tendon but work together
3) Shape of the dome is determined by constraints imposed by the lungs (superior) and abdominal viscera (inferior)
Name 4 differences between the costal and crural muscles of the diaphragm
Name 3 characteristics of the innervation of the motor supply of the diaphragm
Name 3 characteristics of the innervation of the sensory supply of the diaphragm
What are 2 factors that affect the action of the diaphragm
1) anatomical arrangement (costal vs crural ->costal = more respiratory)
2) resting levels
Describe the difference in elastic between a health and emphysema lung
Describe the diaphragm position in supine
Describe the diaphragm position in standing
Describe the diaphragm position in sitting
Describe the diaphragm position in side lying
Describe the inspiratory muscle mechanics during the initial phase of respiration
1) The costal and crural work together while the sternum, low ribs and vertebrae are fixed
2) The muscle fibers contract and shorten axially while the central tendon is pulled straight down resulting in increased vertical dimension and no change to the curvature of the dome
3)The abdominal viscera is pushed down decreasing the abdomens volume but increasing the intra-abdominal pressure
Describe the inspiratory muscle mechanics during the final phase of respiration
1) Costal and crural muscles actions differ and the central tendon becomes fixed because it cannot go down any further
2) The costal diaphragm caused the lower rib cage to elevate and evert increase pressure applied to lower rib cage causing lateral expansion (apposition)
3)The crural diaphragm pulls on upper rib cage by stretching downwards which could cause upper rib cage deflation
4)The scalenes (primary respiratory muscle) stabilize the rib cage against the downward pull of the crural diaphragm and abdominals during forced inspiration and quiet breathing
Describe the zone of apposition
Lungs can expand depending on inspiration levels (space where diaphragm begins in the rib cage all the way to the lowest rib)
Name 3 characteristics of the scalene muscles
1) Primary respiratory muscle
2) Stabilizes rib cage against downward pull of crural diaphragm and abdominals by pulling up on rip cage during quiet breathing and forced inspiration (shut off during expiration)
3) They are innervated by C3-8 ventral rami
Describe hyperinflation during inspiration in terms of diaphragm function
1) At high lung volumes the diaphragm flattens because of shortened fibers (impact the force-length relationship), decreasing the zone of apposition, and radial (horizontal) diaphragm muscle orientation instead of axial (vertical) muscle orientation
2) This creates an expiratory action through lateral costal indrawing during inspiration (deflation)
What are the muscles of the rib cage
1) Intercostals (parasternal or interosseous)
2) Transversus thoracis
Parasternal intercostals (location, activity, and function)
Location: Intercartilaginous portion of the intercostals going from costal cartilage to lateral border of the sternum
Activity: Active during quite breathing and phasically active during inspiration
Function: Causes 80% of rib cage displacement (increase anteroposterior dimension/pump handle) during quiet breathing and increases contribution in a hyperinflated chest
Interosseous Intercostals
1) Primary role is to stabilize the chest wall (external deficient anteriorly and internal deficient posteriorly), keep distance between ribs constant during chest movement, and assist diaphragm to prevent elastic recoil/lung collapse of lungs during expiration
2) Secondary role is to aid in supratidal breathing in healthy individuals (eg. during exercise)
Transversus Thoracis location, activity and function
What is the function of the abdominals during inspiration and expiration
Inspiration: Contracts at end of expiration to lengthen diaphragm (increasing tension) increasing its mechanical advantage and efficiency. Also allowing diaphragm to descend increasing intra-abdominal pressure to allow lateral costal expansion.
Expiration: Active during all force expiratory maneuvers (eg. cough, sneeze, deep & forceful breathing), Valsalva maneuvers (eg. lifting), and during expiration when it becomes active
Name the inspiratory muscles and their innervations
Name the expiratory muscles and their innervations
