Pulmonary Mechanics: Compliance

Question 1

when does positive pressure inflate the lungs?

Answer 1

when pressure is applied externally as in the case of a respirator

Question 2

what is eupnea?

Answer 2

normal quiet breathing

Question 3

how does air leave the lungs?

Answer 3

it is either forced out by muscular contraction or it is passively expelled by the elasticity of the lungs and rib cage

Question 4

what exerts the force to inspire during normal breathing?

Answer 4

contraction of the diaphragm increases the volume of the intrapleural space which decreases the pressure and causes the lung to inflate

Question 5

what kind of pump is the lung?

Answer 5

a negative pressure pump

Question 6

what is the difference of pressure between the atmosphere and intrapleural space during relaxation?

Answer 6

pulmonary is less by 5 cm H2O

Question 7

when is a pulmonary pressure negative? is it actually negative?

Answer 7

when it is less than atmospheric pressure

it is not actually negative but the negative number is the difference from atmospheric pressure

Question 8

why does the lung collapse in the event of a puncture wound to the thoracic cavity? what is this called?

Answer 8

because the pressure inside the cavity equilibrates with the atmosphere and puts positive pressure outside the lung. called a pneumothorax

Question 9

what is the only respiratory muscle that must contract to breathe?

Answer 9

the diaphragm

Question 10

how far down can the diaphragm move in inspiration?

Answer 10

up to 10 cm

Question 11

what is hyperpnea?

Answer 11

active breathing

Question 12

what muscles are involved with inspiration during hyperpnea?

Answer 12

external intercostals

Question 13

what are the role of the sternocleidomastoid and scalene muscles during inspiration?

Answer 13

to reduce resistance to airflow during strenuous exercise

Question 14

at what point is expiration aided?

Answer 14

when ventilation exceeds 40 L/min

Question 15

which muscles aid in expiration?

Answer 15

internal intercostals , rectus abdominus, external obliques, internal obliques and the transversus abdominus

Question 16

what is tachypnea?

Answer 16

more rapid breathing than normal

Question 17

what is the ventilation during eupnea and hyperpnea?

Answer 17

7.5 L/min in eupnea

<120 L/min in hyperpnea

Question 18

what leads to respiratory acidemia and respiratory alkalosis?

Answer 18

acidemia- hypoventilation

alkalosis- hyperventilation

Question 19

what are the three important pressures when talking about respiration?

Answer 19

atmospheric pressure, intrapleural pressure and alveolar pressure

Question 20

how does alveolar pressure vary along the breathing cycle?

Answer 20

it is less than atmospheric pressure during inspiration and greater during expiration

Question 21

how thick is the intrapleural space and how much liquid does it hold?

Answer 21

it is 10 microns thick and holds a few mL of volume

Question 22

how is intrapleural pressure estimated?

Answer 22

by swallowing a balloon into the intrathoracic esophagus. the pressure on the balloon represents the intrapleural pressure

Question 23

when is the external pressure on the chest wall greater than the atmospheric pressure?

Answer 23

when there is a weight placed on the chest

Question 24

what are the transmural pressures involved in breathing?

Answer 24

chest wall pressure (P intrapleural-P atm)
lung pressure (P alveoli- P intrapleural)
total transmural pressure (P alveoli- P atm)

Question 25

what do the transmural pressures do?

Answer 25

set the degree of inflation of the first term in the equation

Question 26

what are outwardly directed transmural pressures regarded as?

Answer 26

positive

Question 27

what is the total transmural pressure pressure at rest?

Answer 27

0

Question 28

what is the lung pressure and chest wall pressure at rest?

Answer 28

lung- positive | chest wall- negative

Question 29

why is the lung pressure always positive/

Answer 29

to maintain inflation

Question 30

what is static compliance of the lung?

Answer 30

determines what particular volume the lung and chest wall will assume for a given transmural pressure

Question 31

what two things must be measured to determine lung compliance in a patient? how is this done?

Answer 31

volume- a spirometer is used during the inhale to determine lung volume pressure- at a certain lung volume, the respiratory muscles are relaxed and the pressure is measured with a esophageal balloon

Question 32

how is lung volume maintained in the relaxed state when measuring pressure to determine compliance?

Answer 32

a weight is placed on the spirometer to prevent the air from escaping the lungs when the glottis is open

Question 33

what is the compliance near the resting position of the lung?

Answer 33

about 0.1 L/cm H2O

Question 34

what pressure must be used to calculate lung compliance?

Answer 34

alveolar pressure

Question 35

how do the compliances of the lungs add up? what implication does this have when describing the compliance of both lungs?

Answer 35

1/Ct=1/C1 + 1/C2 | the compliance of both lungs is 1/2 of an individual lung

Question 36

how is compliance calculated?

Answer 36

as a change in volume over a change pressure (need to take multiple data points)

Question 37

how do the elastic forces of the lung and the chest differ?

Answer 37

the lung only has elastic force inwards but the chest has elastic force directed in both directions

Question 38

when the lungs and chest are in the relaxed position, what are the elasticity forces?

Answer 38

the elastic recoil of the lung equals the elastic recoil of the chest wall

Question 39

how does the compliance of the lungs change with volume?

Answer 39

it is lower at larger lung volumes

Question 40

what is the lung volume when Pt equals zero?

Answer 40

the functional residual capacity

Question 41

what force acts on the lungs to return the volume to functional residual capacity after forced expiration?

Answer 41

recoil of the chest wall only (lungs have no contribution)

Question 42

what happens to intrapleural pressure when the muscles are relaxed and a weight is placed onto the spirometer?

Answer 42

it becomes positive

Question 43

what happens to intrapleural pressure with a weighted spirometer when more air is inspired?

Answer 43

it becomes more positive

Question 44

give an example of disease with increased lung compliance and one where it decreases?

Answer 44

increased-emphysema | decreased-pneumoconiosies (fibrosis)

Question 45

what changes when compliance of the lung changes?

Answer 45

total lung capacity and functional residual capacity

Question 46

why does compliance increase in emphysema?

Answer 46

neutrophils that are attracted to the lung secret proteases. the inhibitors for these proteases are inactivated by cigarette smoke

Question 47

what is the effect of surfactant on lung surface tension and compliance?

Answer 47

it lowers surface tension and increases compliance

Question 48

how does a the compliance of a saline filled lung compare to an air filled lung?

Answer 48

there is an increase in compliance

Question 49

what forces are eliminated when filling the lung with saline?

Answer 49

eliminates recoil pressure due to surface tension and only leaves the component due to elastic fibers

Question 50

how does the compliance of a lung without surfactant compare to one with surfactant?

Answer 50

no surfactant reduces compliance

Question 51

what is respiratory distress syndrome?

Answer 51

lung immaturity in newborns causing collapse due to a deficiency in pulmonary surfactan

Question 52

if there are two bubbles of varying sizes with the same surface tension, which will have a larger internal pressure?

Answer 52

the smaller bubble

Question 53

what happens when there are two alveoli of different sizes next to each other without surfactant? with surfactant?

Answer 53

without- the smaller alveolus empties into the larter | with-the larger alveolus has pressure equal to the smaller

Question 54

why does surface tension increase with radius when involving surfactant?

Answer 54

becuase the larger area dilutes the surfactant