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46 terms

COMD 462 Anatomy & Physiology for Speech, Language, Hearing Ch. 3

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Pressure
force per unit area (cmH2O)
Gas pressure
The sum of the forces of collision divided by the area of the container's walls. Molecules move and collide into one another and the walls of the container they are in.
Pressure differential
change in pressure across containers.
Pressures Within the Respiratory System
Alveolar pressure
Pleural pressure
Abdominal pressure
Alveolar pressure
pressure within the lungs.
Pleural pressure
pressure within the pleural space.
Abdominal pressure
pressure within the abdominal cavity.
Boyle's Law
volume is inversely proportional to pressure:
Increase pressure by compressing the gas into a smaller volume.
Decrease pressure by increasing container volume.
Airflow
Volume change over time.
Volume (L), Changes (sec) = Airflow = l/s
Gas flows from regions of high pressure to regions of low pressure.
Airflow is proportional to pressure differential.
Increase in pressure = increase in airflow.
spirometer
measures volume and capacity within the lungs.
All volumes are measured....
directly.
Except residual volume which is computed.
All capacities are a ....
combination of 2 or more volumes.
Types of Volumes
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Tidal volume
volume of air exchanged during rest breathing.
Inspiratory reserve volume
maximum volume of air which can be inspired after a tidal inspiration.
Expiratory reserve volume
maximum volume of air which can be expired after a tidal expiration.
Residual volume
amount of air left in the lungs after a maximum expiration.
Types of Capacities
Total Lung Capacity
Inspiratory Capacity
Vital Capacity
Functional Residual Capacity:
Total Lung Capacity
total amount of air which can be held in the lungs (all volumes added together).
Inspiratory Capacity
maximum volume of air which can be inspired after a tidal expiration (tidal volume + inspiratory reserve volume).
Vital Capacity
maximum amount of air which can be inspired after a maximal expiration (tidal volume + inspiratory reserve volume + expiratory reserve volume OR total lung capacity - residual volume).
Often express lung volume in terms of %VC
Functional Residual Capacity
amount of air in lungs after a tidal expiration (expiratory reserve volume + residual volume).
End Expiratory Level
Lung volume measured at the rest point of respiration - at the end of a tidal volume expiration (at the top of FRC).
Different from REL. REL is the actual physiologic point; EEL is the measurement of that point (differs slightly).
Alveolar pressure = atmospheric pressure
Represents equilibrium
Two ways the lungs are expanded or contracted:
Recoil of the lung-thorax unit (passive)
Muscle force (active)
Inspiration
always caused by active muscle forces.
Expiration
Is passive during rest breathing.
Is a mix of active and passive forces during speech.
elastic recoil force
Recoil of the Lung-Thorax Unit
The lungs and the thorax are elastic (they resist being deformed from rest).
They are always trying to get back to "rest"
That force is called elastic recoil force
Vital capacity of lung/thorax if they could be separated (decoupled)
The lungs deflate to their rest position - fully deflated (0% VC).
The rib cage moves to its rest position - partially inflated (55% VC).
Vital capacity of lung/thorax unit at rest
the rest position (at REL) is 35-40% VC.
recoil pressure
When moved from rest (35% VC), the lung-thorax unit exerts a force to return to rest.
The force used to return to rest generates recoil pressures
The recoil pressures are pressures within the lung and are a source of power for the speech system.
Recoil forces are proportional to the amount of distortion.
If we move far beyond the rest position, or say 55-60% VC (building up for yelling, perhaps) it would snap beyond rest (recoil to a smaller size) before it returns to rest.
Active Pressures
Generated by the inspiratory and expiratory muscles.
Net Pressure
Muscular pressures are superimposed on the relaxation (recoil) pressures.
Simultaneous passive and active forces.
Net force indicates the resulting change in LV.
Pressure Generation for Speech
Main task of respiratory system: to maintain a constant pressure for speech production.
During speech:
Decrease in lung volume.
Subglottal pressure stays constant ~ below the glottis
Flow stays constant ~ Vocal folds need to be vibrating for sounds ~ need constant pressure to do that.
Relaxation pressures (such as recoil) change.
Pressures for Speech
Balance forces (active and passive) to maintain constant subglottal pressure across lung volume.
Relaxation pressure continually changing due to changes in lung volume.
Use muscular forces to balance and add to relaxation pressures.
Muscular Forces used during speech
Inspiration:
Actively initiated by contraction of the diaphragm and the external intercostals.
Expiration:
Rest breathing: passive forces cause expiration (return to rest position).
Speech: inspiratory and/or expiratory muscles are likely to be used to control and cause expiration.
Used to think inspiratory and expiratory muscles turned on and off through the respiratory cycle.
Now know inspiratory and expiratory muscle forces are active throughout speech breathing.
More efficient way to handle muscle activation.
Inspiratory muscles
Cause inspiration.
Provide a checking action when lung volume is high to slow the descent of the rib cage.
Work against the recoil pressures.
Allows us to extend the length of our utterance. It allows us to slow down the expiration...so we can use that air for speaking. They are stopping the recoil action from happening.
Expiratory muscles:
Abdominal muscles are active throughout breathing to support the respiratory system.
Provide maximal advantage for movement of the rib cage, so expiration of the rib cage does not cause expansion of the abdomen (which would reduce the force of rib cage expiration).
Abdominal muscles contract at rest to held place the diaphragm at its physiologic rest length.
The length at which the diaphragm can contract most quickly and most strongly.
Maximum advantage with minimum effort.

Diaphragm at physiologic rest length is concave

Contract during expiration to generate pressure for speech.
The response depends on the degree to which the thorax is compressed.
Even though the applied muscular forces are identical, you will not be able to compress the thorax as much at low lung volumes.
Additionally, muscular forces have differential effects at various lung volumes.
Without inspiratory muscles, what can a person not do?
Breathe in, checking action (slow down the descent of the rib cage), initiate speech.
Without expiratory muscles, what can a person not do?
control the exhalation
Efficiency of Respiratory System
Mid lung volume range used for speech at comfortable intensity level.
35-60% VC.
Initiate speech at about 45-60% VC.
Terminate at or slightly below EEL (35% VC).
Women and children usually slightly below EEL.
Men usually at EEL.
Maximum efficiency with minimum effort.
Why Is Mid Lung Volume Range Most Efficient?
Mechanism takes advantage of relaxation pressures - positive recoil pressures.
Little checking action required.
Expiratory passive force working in same direction as active force.
Lung-thorax unit wants to compress to move toward rest.
Efficiency of Respiratory System -- Below EEL:
Recoil pressure are negative (lung-thorax unit wants to expand to rest position).
Must use more muscular force to overcome the negative recoil forces.
Efficiency of Respiratory System --At high LV:
More recoil pressure than needed for comfortable intensity speech.
Must use more inspiratory muscular force to slow the compression of the lung-thorax unit.
Efficiency of Respiratory System -- High intensity speech (loud):
Higher subglottal pressure required.
Inhale to a higher lung volume before speaking.
Provides greater recoil pressures.
Less muscular pressure required to obtain the higher subglottal pressure required.
Respiratory Kinematics
Tracks the movements of the rib cage and abdomen during speech.
Motion-motion diagram:
Motion of the rib cage on Y axis.
Motion of the abdomen on X axis.
Motion is calibrated for the sizes of individual's system.
Relative Volume Contribution
During speech, lung volume decreases.
Both rib cage and abdominal systems are responsible for that decrease.
Relative volume contribution:
Change in LV which can be attributed to the rib cage, as opposed to the abdomen.