Mechanics of Breathing Flashcards
Muscles of Inspiration
diaphragm, external intercostals and accesory muscles
Accessory muscles of inspiration
sternocleidomastoid, anterior scalene, middle scalene, posterior scalenes
muscles of expiration
internal intercostals, abdominal muscles
Diaphragm
Most important muscles of inspiration; innervated by the phrenic nerves (2) which stem from C3 to C5
Movement of diaphragm
normal breath about 1cm, forced insp 10 cm, if paralyzed it will move opposite of mormal
Pressure of the abdomen
Abdomen is always positive, more positive during inspiration
External intercostals
when contracted they pull the ribs up and out increasing the A-P diameter of thorax
Expiratory muscles
most important are abodominals
Internal intercostals
pull the ribs down and in
What does the sternocleidomastoid do
elevate sternum
What do Posterior scalenes do
elevate and fix upper ribs
Compliance
change in volume per change in pressure
Normal compliance of the lung
0.2 l/cwp
Hysteresis
lung volume at a given pressure is greater on deflation than on inflation
What decreases compliance
anything that lowers volume; alveolar edema, fibrosis, low volumes
