Ventilation Flashcards
(36 cards)
What is Ventilation?
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.
Muscles that increase the size of the chest
muscles of inhalation
Muscles that decrease the size of the chest
muscles of exhalation
What happens to the internal organs of ones body when the muscles of ventilation contract upon inhalation?
The thorax and lungs expand, the diaphragm contracts and flattens, it pushes down on the viscera and displaces the abdomen outward.
What is Work of Breathing?
The amount of work that must be performed to overcome the elastic and resistive properties of the lungs. Normally occurs during inhalation.
What 3 factors influence WOB?
Lung Compliance, Airway resistance, Respiratory Muscle function
What is lung compliance?
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)
What is airway resistance?
decreased diameter of the conducting airways can lead to an increase in airway resistance and increase in WOB.
What is respiratory muscle function?
What may decrease it?
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
What is the function of the diaphragm?
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.
What is Minute ventilation?
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
What is Tidal Volume (Vt)?
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.
What is Inspiratory reserve volume? (IRV).
the maximum amount of air that can be inhaled over and above the normal tidal volume
What is Expiratory reserve volume? (ERV)
the max amount of air that can be exhaled beyond the normal tidal volume
What is Residual (remaining) reserve volume? (RV)
the amount of air left in the lungs after a complete exhalation
What is inspiratory capacity? (IC)
the sum of the tidal volume and the inspiratory reserve
- the max amount of air that can be inhaled
What is Functional residual capacity (FRC)?
- aka Expiratory Capacity
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…?
What is in equilibrium with Functional residual capacity?
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.
Why is the functional residual capacity important?
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.
What is Vital Capacity?
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.
What regulates ventilation?
Chemoreceptors and Mechanoreceptors (as part of the CNS).
- the CNS ensures that the muscles of ventilation function in a coordinated function.
Central (“C”) chemoreceptors
- where are they located?
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.
Peripheral (pao2) chemoreceptors
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.
Irritant receptors
in between airway epithelial cells. Stimulate bronchoconstriction and hyperpnea (deeper and faster breathing) in response to inhaled irritants.
- ex: when I swallow something spicy