Mechanics of breathing Flashcards
Breathing definition
The bodily function that leads to ventilation of the lungs. Also known as (external) respiration
Ventilation definition
The process of moving gases in (inspiration) & out (expiration) of the lungs
Mechanics of breathing definition
Describes the structural & physiological bases of ventilation
What are examples of obstructive conditions
Asthma, chronic obstructive pulmonary disease (COPD), lung cancer
What are examples of restrictive conditions- intrinsic and extrinsic
- Intrinsic, e.g., pulmonary fibrosis- idiopathic disease (don’t know what causes it)
- Extrinsic – pneumothorax, disorders of the thoracic skeleton
When inspiring is the pressure constant (atm) large or smaller than the pressure variable (alveoli)?
Pressure constant is larger than the pressure variable.
When expiring is the pressure constant (atm) large or smaller than the pressure variable (alveoli)?
Pressure variable is larger than the pressure constant.
What inspiratory muscles are used for quiet breathing?
Diaphragm, external intercostals stabilise rib cage
What inspiratory muscles are used for increasing effort?
Diaphragm, external intercostals lift & expand rib cage, accessory muscles, neck muscles, shoulder girdle muscles
What expiratory muscles are used for quiet breathing?
Elastic recoil of tissues
What expiratory muscles are used for increasing effort?
Internal intercostals and abdominal wall muscles
How are respiratory muscles innervated?
Diaphragm- phrenic nerves (C3, C4, C5)- nerves supply the muscle
Intercostals- segmental thoracic nerves
Why are the pleura important?
The pleura are important in transmitting thoracic cage expansion into lung volume expansion.
What does thoracic cage expansion do?
Thoracic cage expansion exerts an increasing negative pressure on the intrapleural space.
Is pressure in the pleura less than the pressure change in the alveolus?
Yes
Why is change in pressure outside always 0?
End inspiration and end of expiration no movement in gas so equilibrium between the pressure in alveoli and atm P.
When individual breathes in- what happens to the intrapleural P? Does the chest expand? What happens to alveolar P?
First reduction of intrapleural P as chest expands and alveolar P becomes negative
When individual breathes out- what happens to the intrapleural P? Does the chest expand? What happens to alveolar P?
When individual breathes out, relax muscles that enable to breathe in, V in chest goes down, intrapleural rise and becomes less negative, increases alveolar pressure, reverses P gradient so gas moves out until the alveolar goes up and then comes down. Equilibrates with atm P.
How does the respiratory cycle work in terms of pleural P?
R cycle initiated by changes in pleural P, pleura P goes down and then returns back to 0. When you breathe out you raise intrapleural P, alveolar P goes and as breathing slows down eq back to 0.
How can volume of air be measured?
The volume of air moving in and out of the lungs during ventilation can be measured using a spirometer.
Tidal volume
The volume of air moved in or out of the lungs during normal breathing
Inspiratory reserve volume
After a normal expiration, take as deep a breath in as possible
Expiratory reserve volume
After a normal inspiration, breath out as deeply as possible
Residual Volume
Even after a maximal expiration, air remains in the lungs.