A&P Exam 1 Physiology Flashcards
Respiratory System
The structures involved in the exchange of gases between blood and the external environment. Includes:
- lungs
- passageways leading to lungs
- chest structures responsible for movement of air into and out of the lungs.
Volume Flow Rate
The rate at which 1 cc of air moves past a point in 1 second. (cc/sec, LPS)
Resistance
In aerodynamics, the opposition offered to the flow of air through a system. The ratio of pressure drop across the length of the system to the volume rate of air flow through it.
- R=P/V=cm H20/LPS
What does a U-tube manometer measure?
Respiratory pressure in cm H20.
Volume
The amount of air in a cavity, measured in cc, mL or L.
Capacity
Functional combinations of volumes, measured in cc, mL, or L.
Tidal Volume (TV)
Volume of air exchanged in one cycle (inhale & exhale) during quiet breathing.
- 0.5 - 0.75 L
Inspiratory Reserve Volume (IRV)
Max. amount of air that can be inhaled after a tidal inspiration.
- 2.5 L
Expiratory Reserve Volume (ERV)
AKA Resting Lung Volume. Max. amount of air that can be exhaled following passive tidal expiration.
- 1.0 L
Residual Volume (RV)
The amount of air remaining in the lungs after maximum expiration, due to the lungs being stretched.
- 1.1 L
“Dead air”
Residual Volume + air remaining in the airway passages.
Vital Capacity (VC)
Maximum amount of air that can be inspired after maximum expiration. This is the capacity available for speech.
- VC = IRV + TV + ERV
- 4.0 L
Functional Residual Capacity (FRC)
Volume of air remaining after passive exhalation
- FRC = ERV + RV
- 2.1 L
Total Lung Capacity (TLC)
Volume of air in lungs and airway after max. inspiration. All of the volumes together.
- TLC = IRV + TV + ERV + RV
- 5.1 L
Inspiratory Capacity (IC)
Maximum amount of air that can be inspired from RLV
- IC = TV + IRV
- 3.0 L
Pressure
Force per unit of area (cm H2O)
Atmospheric Pressure (Patm)
The pressure on the surface of the earth. A constant that we call 0. We compare everything else to this.
Intraoral pressure (Pm)
Pressure in the mouth.
Subglottal pressure (Ps)
Pressure below the vocal folds.
Alveolar pressure (Pal)
Pressure in the lungs.
Intrapleural pressure (Ppl)
Pressure between parietal and visceral pleura. Always negative.
Boyle’s Law
The pressure of a gas is inversely proportional to its volume, with temperature constant.
Newton’s Law
An unbalanced force acting on any body (solid, liquid, gas) will cause acceleration.
- Air will flow from regions of high to low pressure
- The volume of air flow will be proportional to the difference between the two pressure regions
Respiratory pressures at rest
Respiratory pressures at inhalation
Respiratory pressures at exhalation
Alveolar pressure during tidal expiration
+2 cm H20
Alveolar pressure during tidal inspiration
-2 cm H20
Lung-Thorax Unit and Resting Lung Volume (RLV)
When lungs and thorax are connected, lungs are somewhat expanded relative to disconnected state, while thorax is somewhat compressed relative to disconnected state. This represents resting volume (RV).
Volume, air flow, & pressure relationships during respiration:
What happens with intraoral, subglottal and alveolar pressure during speech production?
- When vocal folds are open, Ps = Pm = Pal.
- When vocal folds are closed, the blockage causes an increase in Ps (lungs continue expiration) and a decrease in Pm (near Patm)
- If this increased pressure difference exceeds 3-5 cm H20, the vocal folds will be blown open.
What percentage of our vital capacity do we use during different types of speech?
- Conversational speech: 35-60% VC
- Loud speech: 80% VC
- (TV: about 10% VC)
Passive Forces: Gravity
Will result in potential energy (energy of position) being converted to kinetic energy (energy of motion).
- Pulls ribs back to rest position after inhalation
Passive Forces: Elasticity
Lungs are elastic, and expand when rib cage expands. They more they are stretched, the more recoil there is when the muscles that expand the rib cage relax.
Relaxation pressure curve
Plots alveolar pressure generated by recoil forces vs. % vital capacity.
- At higher VC, greater recoil forces are trying to return the stretched lungs to rest, generating positive pressure
- At 38% VC (RLV), Patm = Palv produced by recoil forces, so no pressure is generated
- At lower VC, the chest wall is attempting to return to rest, generating negative pressure.
How does the relaxation pressure curve relate to sustained phonation?
Palv required is constant.
- A: recoil pressures are > pressure needed, so muscles of inhalation “brake” the thorax to slow air flow
- B: Palv = pressure needed for utterance
- C: recoil pressures are < pressure needed, so muscles of exhalation work to squeeze out extra air and maintain pressure
How does the addition of active muscular effort change the relaxation pressure curve?
- Pi = pressure from muscles of inspiration
- Pr = pressure from relaxation of musclues of inspiration and expiration
- Pe = pressure from muscles of expiration
How does the pressure volume relationship change at different levels of speech (soft, normal, loud)?
- 1: for a soft utterance, more inspiratory muscle effort is required and less expiratory muscle effort is required relative to normal (2)
- 3: for a loud utterance, less inspiratory muscle effort is required and more expiratory muscle effort is required relative to normal (2)
Muscle activity during a sustained utterance
Negative muscular pressure is inspiratory muscle effort; positive muscular pressure is expiratory muscle effort.
How does posture (upright vs. supine) affect speech?
- Sitting/standing upright: gravity acts in expiratory direction on rib cage, inspiratory direction on abdomen
- Supine: gravity pulls abdomen toward spine and further distends the diaphragm into the thoracic cavity
- Neither inspiration nore expiration is assisted
- Use accessory muscles
How does the timing of respiration differ between quiet breathing and speech breathing?
- Quiet:
- 12+ times/minute
- expirations slightly > inspirations
- Speech breathing:
- frequency of breathing decreases
- inspiration more abrupt
- expiration lengthened
How do passive and active forces work to help us during connected speech?
- Rapid changes in demand for muscle effort.
- Pulsatile variations in muscle effort are overlaid on the usual background level of alveolar pressure for steady state utterances.
How do changes in compliance affect the relaxation pressure curve?
- Excessive compliance: lungs stretch too far and don’t recoil as efficiently. Have to force exhale to reach adequate pressure
- Loss of compliance: lungs don’t stretch far enough and elastic recoil is increased, which reduces vital capacity. Have to frequently pause during speech to inhale.
