Respiratory Muscles-Scharf

Question 2

How is lung volume affected by muscle length?

Answer 2

Increased lung volume with shorter inspiratory muscles. At TLC, no more tension can be created.

Question 3

What type of muscles are there in the respiratory system?

Answer 3

Oxidative (fatigue resistant) Type I - slow oxidative (SO) Type IIa - Fast oxidative (FOG) Glycolytic (fatigue susceptible) Type IIb - slow glycolytic (SG)

Question 4

What are breakdown of the muscles in the diaphragm?

Answer 4

50% Type I, 25% Type Iia and 25% Type IIb

Question 5

What are the inspiratory muscles?

Answer 5

60% diaphragm, external intercostals, parasternals. Accessory: scalene, Sternocleidomastoids. Upper airway: Genioglossus alae nasae Abductors of larynx.

Question 6

What are the expiratory muscles?

Answer 6

Abdominals, internal intercostals, Triangularis sternae

Question 7

What happens to the thoracic muscles in isovolumic or expulsive contraction?

Answer 7

Equal movement in opposite directions at 45 degree angles.

Question 8

What happens to the thoracic muscles in quadriplegia below C5?

Answer 8

Diaphragm can move but ribcage and abdominals cannot. Pressure moves the ribs in and the abdomen out.

Question 9

What happens to the thoracic muscles in diaphragmic paralysis?

Answer 9

Ribs move out and move the diaphragm up which moves the abdomen in.

Question 10

What is Hoover’s Sign?

Answer 10

During emphysema, extreme hyperinflation causes the diaphragm to flatten and the lower ribcage moves in because of a reduced zone of apposition. Ribs move in an expiratory direction during inspiration

Question 11

What is the proportion of the diaphragmic cycle in inspiration?

Answer 11

Duty cycle, should be 1/3

Question 12

What is the tension-time index of the diaphragm?

Answer 12

Predicts fatigue: TTI = Diaphragmic pressure/Max diaphragmic pressure x Inspiratory time/total time. If over .15 respiratory failure is imminent.

Question 13

In which diseases does respiratory muscle fatigue often cause respiratory failure?

Answer 13

COPD
Shock (the main cause of death!)
Certain electrolyte abnormalities (hypophosphatemia)
?Sepsis
?hypercapnia

Question 14

What is the treatment for respiratory failure.

Answer 14

Rest the muscle

Fix electrolyte abnormalities
?Beta agonists/catecholamines
?methylxanthines (theophyllin)
Decrease ventilatory drive to decrease force production (fix hypoxia, hypercapnia)
Correct low cardiac output state
?Anti-oxidants
Training (long-term)

Question 15

What are the types of muscle fatigue?

Answer 15

“Peripheral” - at the level of the muscle
Transmission: failure of excitation-contraction coupling (high frequency fatigue)
Contractile: failure of excitation-contractile coupling or contractile proteins (Low frequency fatigue)
Central: decrease in motoneuron output to muscles: may be due to feedback from development of lactic acidosis. A protective mechanism (put off peripheral fatigue)

Question 16

How can the diaphragm’s maximum strength and tension/force be changed?

Answer 16

Decreased by being a couch potato (curve moves down), increased by endurance training. Proportion load/max load decreases and endurance will increase with increasing max strength.

Question 17

What are the forms of assessment of muscle force?

Answer 17

Two balloons swallowed by patient: one in esophagus and one in the abdomen/stomach. Diaphragmic pressure measured by abdominal pressure - Pleural pressure.

Otherwise, MIP can be measured from sum of all inspiratory muscles or MEP sum of all expiratory muscles.