PBL Flashcards
What muscles are involved in quiet inspiration?
Diaphragm - contracts descends and flatterns (75%)
External intercostal muscles - raise the ribs (25%)
what muscles are involved in quiet expiration?
no active muscles - relies on the elastic recoil of the lungs and muscles
forced inspiration requires which muscles?
diaphragm, external intercostals, scalene, SCM
forced expiration requires action from which muscles?
internal intercostals, transverse thoracis,
abdominal muscles
what connective tissue fibres aid in the elastic recoil of the lungs?
collagen and particularly elastin
what happens if the chest wall is punctured?
pressure in the pleural cavity, alveoli and atmosphere are all equalised - this along with the elastic recoil causes the collapse of the lung (removal on negative pressure in the pleural cavity)
What are the 4 types of a pneumothorax?
- Primary spontaneous
- Secondary spontaneous
- Traumatic pneumothorax
- Tension pneumothorax
what are likely signs of a tension pneumothorax?
- displacement of the trachea
- engorged jugular veins - increased pressure in chest obstructs venous return
- flow of air in one way so air only moved into the plural space - it cannot escape
- tachycardia
- dyspnoea
- cyanosis
- hyperresonance on affected side
airways resistance is proportional to what?
length/radius(to the power 4)
the work of breathing depends on what 4 things?
- Tidal volume
- respiratory frequency
- lung compliance
- airways resistance
what four things can lead to increased work of breathing and why?
- decreased compliance = more energy needed to stretch lungs
- increased frequency = need to create a larger pressure gradient to move air faster
- increased tidal volume = stretch lungs further
- increased resistance = greater pressure to overcome resistance
where would you insert as aspiration needle to treat/decompress a tension pneumothorax?
2nd ICS mid-clavicular line
where is a chest drain inserted?
4/5th ICM mid-axillary line
What is the mode of action of lidocaine?
blocks voltage gated sodium channels, causes loss of sensation and eliminates the responsiveness of cells to pain. bind most strongly to open or inactive state receptors and less strongly to resting state - more frequently the channels are activated the greater the degree of block produced
describe the changes in pleural pressure during respiration.
pleural pressure is normally negative to alveolar pressure, during inspiration - expansion of the chest creates a more negative pressure and therefore ‘pulls’ the lungs outward, this lowers the pressure in the alveoli and draws air into the lungs
during expiration - elastic recoil makes the plural pressure less negative compressing the lungs and forcing air out.