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Unit 4 Physiology > Pulmonary Mechanics: Compliance > Flashcards

Pulmonary Mechanics: Compliance Flashcards

1
Q

when does positive pressure inflate the lungs?

A

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

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2
Q

what is eupnea?

A

normal quiet breathing

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3
Q

how does air leave the lungs?

A

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

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4
Q

what exerts the force to inspire during normal breathing?

A

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

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5
Q

what kind of pump is the lung?

A

a negative pressure pump

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6
Q

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

A

pulmonary is less by 5 cm H2O

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7
Q

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

A

when it is less than atmospheric pressure

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

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8
Q

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

A

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

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9
Q

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

A

the diaphragm

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10
Q

how far down can the diaphragm move in inspiration?

A

up to 10 cm

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11
Q

what is hyperpnea?

A

active breathing

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12
Q

what muscles are involved with inspiration during hyperpnea?

A

external intercostals

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13
Q

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

A

to reduce resistance to airflow during strenuous exercise

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14
Q

at what point is expiration aided?

A

when ventilation exceeds 40 L/min

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15
Q

which muscles aid in expiration?

A

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

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16
Q

what is tachypnea?

A

more rapid breathing than normal

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17
Q

what is the ventilation during eupnea and hyperpnea?

A

7.5 L/min in eupnea

<120 L/min in hyperpnea

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18
Q

what leads to respiratory acidemia and respiratory alkalosis?

A

acidemia- hypoventilation

alkalosis- hyperventilation

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19
Q

what are the three important pressures when talking about respiration?

A

atmospheric pressure, intrapleural pressure and alveolar pressure

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20
Q

how does alveolar pressure vary along the breathing cycle?

A

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

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21
Q

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

A

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

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22
Q

how is intrapleural pressure estimated?

A

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

23
Q

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

A

when there is a weight placed on the chest

24
Q

what are the transmural pressures involved in breathing?

A 
chest wall pressure (P intrapleural-P atm)
lung pressure (P alveoli- P intrapleural)
total transmural pressure (P alveoli- P atm)
25
Q

what do the transmural pressures do?

A

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

26
Q

what are outwardly directed transmural pressures regarded as?

A

positive

27
Q

what is the total transmural pressure pressure at rest?

A

0

28
Q

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

A

lung- positive

chest wall- negative

29
Q

why is the lung pressure always positive/

A

to maintain inflation

30
Q

what is static compliance of the lung?

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

about 0.1 L/cm H2O

34
Q

what pressure must be used to calculate lung compliance?

A

alveolar pressure

35
Q

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

A

1/Ct=1/C1 + 1/C2

the compliance of both lungs is 1/2 of an individual lung

36
Q

how is compliance calculated?

A

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

37
Q

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

A

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

38
Q

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

A

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

39
Q

how does the compliance of the lungs change with volume?

A

it is lower at larger lung volumes

40
Q

what is the lung volume when Pt equals zero?

A

the functional residual capacity

41
Q

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

A

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

42
Q

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

A

it becomes positive

43
Q

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

A

it becomes more positive

44
Q

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

A

increased-emphysema

decreased-pneumoconiosies (fibrosis)

45
Q

what changes when compliance of the lung changes?

A

total lung capacity and functional residual capacity

46
Q

why does compliance increase in emphysema?

A

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

47
Q

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

A

it lowers surface tension and increases compliance

48
Q

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

A

there is an increase in compliance

49
Q

what forces are eliminated when filling the lung with saline?

A

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

50
Q

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

A

no surfactant reduces compliance

51
Q

what is respiratory distress syndrome?

A

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

52
Q

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

A

the smaller bubble

53
Q

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

A

without- the smaller alveolus empties into the larter

with-the larger alveolus has pressure equal to the smaller

54
Q

why does surface tension increase with radius when involving surfactant?

A

becuase the larger area dilutes the surfactant

Unit 4 Physiology (31 decks)

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