Ventilation

Question 1

What is Ventilation?

Answer 1

The process of air moving into and out of the lungs

Due to the difference between intrapulmonary pressure (pressure inside the lungs) and atmospheric pressure.

When the pressure falls below atmospheric pressure, air enters the lungs, and inhalation occurs. At the end of inhalation the muscles of ventilation relax, the thorax contracts and the lungs are compressed, and intrapulmonary pressure rises. When the pressure rises above atmospheric pressure air exits the lungs and exhalation occurs.

Question 2

Muscles that increase the size of the chest

Answer 2

muscles of inhalation

Question 3

Muscles that decrease the size of the chest

Answer 3

muscles of exhalation

Question 4

What happens to the internal organs of ones body when the muscles of ventilation contract upon inhalation?

Answer 4

The thorax and lungs expand, the diaphragm contracts and flattens, it pushes down on the viscera and displaces the abdomen outward.

Question 5

What is Work of Breathing?

Answer 5

The amount of work that must be performed to overcome the elastic and resistive properties of the lungs. Normally occurs during inhalation.

Question 6

What 3 factors influence WOB?

Answer 6

Lung Compliance, Airway resistance, Respiratory Muscle function

Question 7

What is lung compliance?

Answer 7

measure of the distensibility of tissue // considers the relationship between tissue stretch and force of pressure required to make that stretch occur
→ less compliant lungs need more pressure to inflate than lungs with normal compliance
→ decreased lung compliance can increase WOB (clients will often take small shallow breaths to decrease WOB)

Question 8

What is airway resistance?

Answer 8

decreased diameter of the conducting airways can lead to an increase in airway resistance and increase in WOB.

Question 9

What is respiratory muscle function?

What may decrease it?

Answer 9

when WOB is increased, these muscles are usually able to rise to the challenge to work harder to maintain or increase ventilation

Decreased with :

• prolonged WOB (overuse - exhaustion)
• underuse
• drugs
• age extremes
• poor nutrition
• spinal cord/Brian injury
• multiple sclerosis or any spinal deformity

Question 10

What is the function of the diaphragm?

Answer 10

the main muscle of inhalation. It is a dome-shaped fibromuscular septum that separates the thoracic and abdominal cavities. During normal breathing it does 80% of the WOB. on inhalation it contracts and flattens, pushes down on the viscera and displaces the abdomen outward. Action is governed by the medulla through impulses through the phrenic nerve.

Question 11

What is Minute ventilation?

Answer 11

The volume of gas inhaled or exhaled from a person’s lungs per minute.
= tidal volume x respiratory rate
Normal minute ventilation is between 5-8L per minute (Lpm)
Minute ventilation can double with light exercise as both tidal volume and breathing rate increase, and can exceed 40 Lpm with heavy exercise

Question 12

What is Tidal Volume (Vt)?

Answer 12

the amount of air inhaled and exhaled with each breath

the amount of air that moves in and out of the lungs during normal breathing

• the size of each breath → can be auscultated by listening to the pts chest (decreased or quiet sounds usually mean tidal volume is decreased)
  Increased RR can decrease tidal volume.

Question 13

What is Inspiratory reserve volume? (IRV).

Answer 13

the maximum amount of air that can be inhaled over and above the normal tidal volume

Question 14

What is Expiratory reserve volume? (ERV)

Answer 14

the max amount of air that can be exhaled beyond the normal tidal volume

Question 15

What is Residual (remaining) reserve volume? (RV)

Answer 15

the amount of air left in the lungs after a complete exhalation

Question 16

What is inspiratory capacity? (IC)

Answer 16

the sum of the tidal volume and the inspiratory reserve

• the max amount of air that can be inhaled

Question 17

What is Functional residual capacity (FRC)?

- aka Expiratory Capacity

Answer 17

The sum of the expiratory reserve volume and the residual reserve volume
- the sum of how much air is exhaled beyond a normal breath + the amount of air left in the lungs after exhalation

–> the amount of air left in the lungs after a normal exhalation.

The larger the FRC, the less WOB.
- when you have a larger amount of o2 available after you exhale, you don’t have to work as hard to get o2 in

When small airways are not opened on inspiration, the associated alveoli are not ventilated, and less of the alveolar-capillary membrane is involved in GE.
Decreased FRC = decreased arterial oxygenation
- less FRC means less o2 for the alveoli…?

Question 18

What is in equilibrium with Functional residual capacity?

Answer 18

The opposing elastic recoil forces of the lungs and chest wall are in equilibrium, and there is no exertion by the diaphragm or other respiratory muscles.

Question 19

Why is the functional residual capacity important?

Answer 19

It keeps the small airways open and prevents the complete emptying of the lungs during each respiratory cycle.
If there is no FRC, the alveolar PO2 and PCO2 will vary widely during breathing and will interfere with the diffusion of the respiratory gases.

Question 20

What is Vital Capacity?

Answer 20

the sum of the inspiratory reserve volume, the tidal volume, and expiratory reserve volume.

( is the maximum amount of air that can be expelled from the lungs after being completely filled. )

• 3-5 L
• vital capacity decreases with lung disease, age

–> think about breathing in as much as you can, past the IRV, + the size of your normal breath (TV) + breathing out that air as much as you can, past the ERV.

Question 21

What regulates ventilation?

Answer 21

Chemoreceptors and Mechanoreceptors (as part of the CNS).

- the CNS ensures that the muscles of ventilation function in a coordinated function.

Question 22

Central (“C”) chemoreceptors

- where are they located?

Answer 22

respond to changes in hydrogen ion concentration. Ventilation increases when ion concentration rises and decreases vice versa.
- chemoreceptors respond to ANY change in PaCO2.

When chemoreceptors are triggered, they stimulate the respiratory centre in the medulla and pons.

Question 23

Peripheral (pao2) chemoreceptors

Answer 23

increase ventilation in response to changes in PaO2 and H ion concentration. An increase in either results in an increase in ventilation.
→ when o2 levels in arterial blood fall, these receptors increase ventilation to try to bring more o2 in the lungs. They are not triggered unless pAO2<60MM hg. (hypoxemia)

located in the carotid bodies and aortic arch.

Question 24

Irritant receptors

Answer 24

in between airway epithelial cells. Stimulate bronchoconstriction and hyperpnea (deeper and faster breathing) in response to inhaled irritants.

• ex: when I swallow something spicy

Question 25

Stretch receptors

Answer 25

In the airways. stimulated by changes in lung volume. They inhibit inhalation and are thought to protect the lung from overinflation.

Question 26

the movement of oxygen from the outside environment to the cells within tissues, and the removal of carbon dioxide in the opposite direction.

Answer 26

Respiration

Question 27

External respiration

Answer 27

gas exchange that takes place at the lung level through the alveolar capillary membrane.

Question 28

Internal respiration

Answer 28

the diffusion of gases in and out of the cells at the tissue level.

Question 29

What are the role of chemoreceptors in ventilation?

Answer 29

They provide feedback that influences ventilation, which is an important factor in oxygen supply.

Question 30

What are both central and peripheral chemoreceptors sensitive to?

Answer 30

Paco2 levels in the blood
- when PaCO2 levels are too high, they signal to increase ventilation. When Paco2 levels are too low, they signal to decrease ventilation..?

Question 31

Chemoreceptors sense changes when ventilation is decreased and PaCO2 rises (hypercapnia) - what do they do?

Answer 31

They send messages to the controllers in the brainstem to increase ventilation by increasing RR and/or tidal volume.
- they respond to any change in Paco2.

Question 32

What is hypercapnia?

Answer 32

build up up CO2 in the blood

Question 33

What are Peripheral chemoreceptors specifically able to do that central chemoreceptors cannot?

Answer 33

They are sensitive to PaO2 levels. When o2 in arterial blood falls, they facilitate an increase in ventilation to try and bring more o2 in.

Question 34

Peripheral chemoreceptors are not triggered to facilitate increased ventilation unless …

Answer 34

The PaO2 falls below 60mm Hg. (hypoxemia)

Question 35

What causes a decrease in the driving pressure for CO2?

Answer 35

Decreased ventilation. Less CO2 is exhaled, co2 levels increase in the alveoli. So the movement of CO2 from the pulmonary capillary to the alveoli will decrease, allowing CO2 levels in the arterial blood (Paco2) to rise.

Question 36

What is the primary chemical trigger for regulation of ventilation?

Answer 36

Paco2
- When paco2 levels get too high, peripheral and central chemoreceptors are triggered to increase ventilation to try to bring in more o2 to have more of a balance.