Physiology of Respiration

Chapter 3

Respiratory Function

Changes as we Age

Exercise

Suffer setbacks in health

Passive Expiration

Let the forces and tissues restore to a resting position

Active Expiration

Use muscular effort to push just a little farther

ExpirationEliminating waste products of respiration

As you breathe in 10 times quietly

Contract your diaphragm actively

Simply relax the muscles and you expire/exhale

Elasticity

Gravity

ExpirationLungs are highly elastic, porous tissue

Sponge like

In adult bodies- lungs do not completely fill up the thoracic cavity

When stretched- they are stretched beyond their resting position

Result of stretching is increased capacity and reserve

ExpirationAdult lungs are never completely compressed, there is always a reserve of air within them

Lungs expand- muscles are expanding the rib cage and then they relax, lungs return to their original shape and size

Abdominal muscles stretch when you inhale and then they relax and return to their original length- they push the abdominal viscera back in and force the diaphragm up

ExpirationGravity

Acts on the ribs to pull them back after they have been expanded – accessory muscles

Works in favor of maximizing your overall capacity

Pulls abdominal viscera down, leaving more room for the lungs

Body position plays a significant role in efficiency of respiration

Measuring Respiration

Respiratory Flow- rate of flow of air on/out

Volume- measured in liters, mililiters, cubic cm

Capacity

Lung VolumeIndividual breathes into the wet spirometer

Causes a volume of water to be displaced

Amount of water displaced gives an accurate estimate of the air that was required to displace it

Results are charged on a “recording drum”

Respiration for Life

Four stages for gas exchange

Ventilation- air comes into the respiratory pathway

Distribution- air is distributed to the 300 million alveoli

Perfusion- oxygen poor blood migrates through to the 6 billion capillaries

Diffusion- actual gas exchange across the alveolar-capillary membrane

TurbulenceLungs expand

Air courses through the bronchi

Some slight turbulence at the bifurcation of the bronchi but the air generally flows unimpeded.

A small irregularity such as mucus or muscle spasm can greatly increase resistance to airflow

Respiratory CycleQuiet respiration

12-18 cycles of respiration per minute

One cycle is ½ liter of air

We process approximately 6-8 liters of air every minute (think of a 2 liter bottle)

Developmental Process of RespirationAlveoli will increase from about 25 million at

birth to more than 300 million by 8 years of age.

Conducting airways will grow steadily in diameter and length

Adults breath cycles 12-18 per minute

Newborns average 40-70 cycles per minute

5 year old- 25 cycles per minute

Chart on p. 138

Volume and Capacities

VolumeEstimate the amount of air each compartment can hold

Tidal Volume

Inspiratory Reserve Volume

Expiratory Reserve Volume

Residual Volume

Dead Air

Volume and Capacities

CapacitiesVital Capacity

Functional Residual Capacity

Inspiratory Capacity

Total Lung Capacity

Tidal VolumeVolume of air we breath in during a respiratory cycle

Varies as a function of physical exertion, body size, and age

Quiet Tidal Volume has an average forAdult males 600 cc

Adult females 450 cc

¼ of a 2-liter soda bottle every 5 seconds

Fill up three 2-liter bottles in one minute

Inspiratory Reserve VolumeVolume that can be inhaled after a tidal inspiration

Volume of air that is in reserve for use beyond the volume you would breath in tidally

Sit quietly

Breathe in and out until you become aware of your breath

Tag each breath mentally with “in”/ “out”

Stop breathing at the end of one of your inspirations

Instead of breathing out- breathe in as deeply as you can

Amount you inspired after you stopped is the IRV- average volume is 2.475 liters

Expiratory Reserve Volume

Amount of air that can be expired following passive, tidal expiration.

Breathe in and out normally until you are aware of your breath

Stop breathing right after you exhaled

Then expire as completely as you can

ERV- average is 1.0 liter

Also referred to as resting lung volume- volume present in the resting lungs after a passive exhalation

Residual VolumeVolume remaining in the lungs after a maximum exhalation

No matter how forcefully you exhale, there is a volume of air that cannot be eliminated- approximately 1.1 liters

Does not exist in the newborn

Dead Space AirAir in conducting passageways

Air that cannot undergo gas exchange

Adult has approximately 1/10 of a Liter

Associated with Residual Volume (RV) because it is air that cannot be expelled

Vital CapacityCapacity available for speech

Combination of the Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV) and Tidal Volume (TV)

Represents the total volume of air that can be inspired after a maximal expiration

Approximately 4 liters in an average adult

Functional Residual Capacity

Volume of air remaining in the body after a passive exhalation

Expiratory Reserve Volume (ERV) + Residual Volume (RV)

Approximately 2.1 Liter

Total Lung Capacity

Sum of all of the volumes

Totals Approximately 5.1 Liters

Different from the Vital Capacity because it includes Residual Volume (RV) which serves as a buffer in respiration in providing constant oxygenation when needed

Inspiratory Capacity

Maximum inspiratory volume possible after tidal expiration

Capacity of the lungs for inspiration (Tidal volume + Inspiratory reserve volume)

Approximately 3 liters for adults

Effects of AgeP. 142 and 143 Figure 3-6

As age increases, Vital Capacity decreases by about .1 liter per year in adulthood

Vital Capacity steadily increases with body growth up to about age 20, holds steady through about 25 and then begins a steady decline

Females have a smaller vital capacity throughout the life span

Effects of AgeResidual Capacity increases with age

Why?

Individuals retain their functional Total Lung Capacity (that doesn’t decrease)- however, they have a reduction in function

As we age, compliance of the lungs decrease which results in reduced ability to inflate the lungs

Lung volume is constant but there is growth in the volume that is unavailable for direct gas exchange – residual volume- dead space air!

Respiration and Pressure

Diaphragm contracts- air flows in

Increased volume

Negative pressure

Diaphragm stops contracting- air flows out of the lungs

Decreased volume

Positive pressure

Pressures of the Respiratory

SystemAlveolar pressure

Intrapleural pressure

Subglottal pressure

Intraoral pressure

Atmospheric pressure

All are measured relative to atmospheric pressure is treated as a constant “0” against which to compare respiratory pressures

Alveolar PressurePressure that is present within the individual alveolus

Inhalation: Air flows into the Alveoli and the volume increases. When volume increases, pressure decreases- negative alveolar pressure

Exhalation: Air flows out of the Alveoli and the volume decreases. When volume decreases, pressure increases- positive alveolar pressure.

Alveolar PressureSurfactant- Surface active solution- is released in the alveoli when the lungs are expanding

Reduces surface tension which reduces the pressure of the alveoli

Keeps the walls of the alveoli from collapsing

Keeps fluid from the capillaries from being drawn into the lungs

Promotes airflow

Facilitates effort-free respiration

Intrapleural pressure

Measure the pressure in the space between the parietal and visceral pleurae

ALWAYS negative throughout respiration

Lungs, inner thorax, and diaphragm are wrapped in this continuous sheet of pleural lining

Its important to maintain this negative pressure within the intrapleural space to keep from the lungs collapsing

Alveolar and Intrapleural

PressureDiaphragm contracts- air flows in- alveolar pressure drops- intrapleural pressure becomes more negative as the diaphragm attempts to pull the diaphragmatic pleurae away from the visceral pleurae. (the volume-space between the two pleural linings increase)

Diaphragm relaxes- air flows out, alveolar pressure increases, intrapleural pressure becomes less negative

Why does Intrapleural pressure

remain negative?Lungs are in a state of continual expansion because the thorax is larger than the lungs

Lungs are never completely deflated because of the residual volume

Subglottal Pressure

The pressure measured beneath the level of the vocal folds

Directly related to what is happening in the lungs as long as the vocal folds are open

Air flows into the lungs- subglottal pressure will be negative

Air flows out of the lungs- subglottal pressure will be positive

Subglottal pressure

What happens when the vocal folds are closed?

Blocks air flow

Immediate increase in the subglottal air pressure as the lungs continue expiration

When the pressure exceeds 3-5 cm H2O, the vocal folds will be blown open and voicing will begin. This is a critical pressure as it is a minimal requirement of respiration for speech

Intraoral PressureRespiratory pressure measured above the vocal folds within the oral cavity

When vocal folds are open- intraoral, subglottal and alveolar pressure are the same

Closing the vocal folds causes the intraoral pressure to drop as the subglottal pressure increases

Muscles vs. Gravity

InspirationUse of muscular action to exert force and overcome gravity

Stretch tissue and distend the abdomen

ExhalationUses elasticity and gravity to save energy

Muscles relax and return to original state due to elasticity and gravity

Respiration for Speech

Must maintain a steady flow of air at a relatively steady pressure

Vocal folds require a minimum subglottal pressure of 3-5 cm H2O

Conversational speech- 35-60% of our vital capacity

Loud speech uses lung volumes up towards 80% of vital capacity

Respiration for Speech

How do we maintain the continuous flow of air upon expiration to use it for speech?

The muscles of inspiration must intervene

They “check the outflow of air”

They impede the outflow of air to maintain a constant subglottal pressure

This gives us control of phonation

Respiration for Speech

Abdominal muscles remain in a state of graded tonic contraction during exhalation

Respiratory cycle for speech is markedly different

Long drawn out expiration to produce long utterances

Short inspiration to maintain the smooth flow

10% of the respiratory cycle on inspiration

90% of the cycle on exhalation

Does not change the amount of air we breathe in/out just alter how long we spend in each stage

Respiration for Speech

We use a “checking action” when we exhale during speech

Restrains the flow of air out of your inflated lungs by using the inspiratory muscles that got it there in the first place

Creates respiratory control for speech

Maintain constant flow of air through the vocal tract

Helps to maintain the constant subglottal pressure to maintain phonation

Effects of Posture on Speech

Supine positionGravity is pulling the abdominal viscera toward the spine

Does not support inhalation or exhalation

Muscles of inhalation must elevate both abdomen and rib cage against gravity

Sitting postureGravity is pulling the abdominal viscera down

Pulling the rib cage down

Supports efficient inhalation and exhalation

Pressures of Speech

Two levels of pressure simultaneouslyConstant supply of subglottal pressure required to drive the vocal folds

3-5 cm H2O vocal folds move

7-10 cm H2O conversational speech

Micro-control of that constant pressureAdding stress , intensity and pitch changes

Increase subglottal pressure by 2 cm H2O to add stress

Pressure of Speech

Speaking on expiratory reserveWhen we get down to the Resting Lung Volume and we have more to say

Instead of using the muscles of inspiration to keep the air from flowing out

We have to enlist the muscles of expiration to push beyond the RLV

We continue talking beyond the point where we would normally take another breath

The deeper our inhalation or the farther we go below RLV, the greater the force we have to overcome