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CPR Exam 2 > L1 - PHYS - Respiratory Cycle & Mechanics > Flashcards

L1 - PHYS - Respiratory Cycle & Mechanics Flashcards

1
Q

What is the journey of oxygen?

A

Air (atmosphere) –> Lung and Blood –> Tissues –> Mitochondria

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2
Q

What is Boyle’s Law?

A

Pressure of gas is inversely proportional to its volume. P1V1=P2V2

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3
Q

How does air passively move into the lungs?

A

When the lung volume increases, pressure decreases, so air enters.
When lung volume decreases, pressure increases so air exits.

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4
Q

What is PB typically?

A

760 mm Hg

HOWEVER, we normalize it to 0 cm H2O

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5
Q

What happens when inspiratory muscles contract?

A

thoracic volume increases

chest wall wants to expand and lungs want to collapse - have interplay

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6
Q

Are lungs and muscles/ribs directly connected?

A

No lungs and muscles/ribs are NOT directly connected.

This comes into play during inspiration events (contraction of muscles)

Because of the coupling of lungs and chest wall, lungs expand as thorax expands.

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7
Q

What are the Pleural of the Lungs?

A

The visceral and parietal pleura.
Intrapleural Space
Between the visceral and parietal pleura there is a fluid (parietal fluid) - 5-35 um thick

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8
Q

What is Intrapleural Pressure?

A

It is less than atmospheric pressure (negative)

Can think of it as intrathoracic pressure - the pressure everywhere in the thorax EXCEPT the lumens of blood vessels, lymphatics, or airways.

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9
Q

What is the unit for respiratory pressures?

A

cm H2O (NOT mm Hg as in cardio phys)

1 cm H2O is about 1m Hg due to density differences

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10
Q

What is intrapleural pressure (Ppl) at rest?

A

near -5 cm H2O

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11
Q

What is Ppl (intrapleural pressure) during inspiration?

A

As volume increases, pressure decreases, so Ppl goes to -8 cm H2O

It becomes more negative

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12
Q

What does Alveolar Pressure (PA) do during inspiration?

A

PA decreases as thoracic cavity increases in size.

From 0.5 cm H2O to -1 cm H2O

At rest PB=PA = 0 cm H2O
At end of inspiration PA is -1 due to increase in alveolar size which causes air to enter lungs (pressure difference!)

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13
Q

What is Transpulmonary Pressure?

A

The difference between Pleural Pressure and Alveolar Pressure.

Ptp = Palv - Ppl

5cm H2O at rest

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14
Q

What would happen if Ptp = 0?

A

Lung collapse

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15
Q

What does the respiratory cycle graph look like for volume changes?

A

Positive bell curve ranging 0 to +0.5 liters

Increasing during inspiration, decreasing during expiration.

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16
Q

What does the respiratory cycle graph look like for Alveolar Pressure changes?

A

Looks like an oscillation curve

Decreases then increases during inspiration (0 to -1 cm H2O and then back)
Increases during during expiration (0 to +1) and then decreases back to 0.

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17
Q

What does the respiratory cycle curve look like for the Intrapleural Pressure changes?

A

a negative bell curve / looks like a U/V

During inspiration it goes more negative from -5 cm H2O to -8 cm H2O
During expiration it increases from -8 back to -5 cm H2O

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18
Q

What does the Air Flow graph look like during the respiratory cycle?

A

Looks like an oscillation curve

During inspiration it decreases from 0 to -1 then increases back to 0 L/sec.
During Expiration it increases from 0 to +1 and then back to 0 L/sec.

*the convention that inspiration air flow is negative is now important and lost in history

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19
Q

What are the values of the respiratory cycle at rest?

A

Volume = 0 L
PaO = 0 cm H2O
Ppl = -5 cm H2O
Air Flow = 0 L/sec

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20
Q

What are the values of the respiratory cycle Mid-Inspiration?

A

Volume - Increasing
Pa - Decreasing
Ppl - Decreasing
Air - flowing INTO the lungs

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21
Q

What are the values of the respiratory cycle at the End of Inspiration?

A 
Volume - reached PEAK increase
Tidal Volume, Vt = 500 ml
Pa - returned to zero
Ppl - decreased to -8 cm H2O
Air Flow - ceased (at zero)
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22
Q

What are the values of the respiratory cycle Mid-Expiration?

A

Volume - Decreasing
Pa - Rises
Ppl - begins to Rise
Air - exits the lungs (goes into positive)

23
Q

What are the values of the respiratory cycle at the End of Expiration?

A

Volume - returned to resting (zero)
Pa - decreases to Zero
Ppl - returns to resting (-5 cm H2O)
Air - exited lungs (zero)

*LO, learn to draw graphs

24
Q

What is Ptp during the Respiratory Cycle?

A 
Ptp values:
Rest : +5 cm H20
Mid-Inspiration: +5.5 cm H2O
End Inspiration/Start Expiration: +8 cm H2O
Mid-Expiration: +7.5 cm H2O
Rest: +5 cm H2O
25
Q

Define Minute Ventilation (VE)

What is the equation?

A

Volume of air inhaled every minute

VE = VT x frequency

26
Q

Define tidal volume (VT)

A

volume of air inhaled and exhaled in single breath

27
Q

What is the normal minute ventilation value?

A

7,000 ml/min or 7 L/min

14 breaths per minute (RR)
VT= 500 ml/breath
14x500 = 7,000

28
Q

What is Dead Space of the lungs?

A

Regions of the lung that receive air, but not blood so NO GAS EXCHANGE

29
Q

What are the three types of Dead Spaces?

A
  1. Anatomic Dead Space
  2. Physiologic Dead Space
  3. Alveolar Dead Space
30
Q

What is Anatomic Dead Space?

A

Space in respiratory system other than alveoli

150 lb person = 150 ml of VDS

31
Q

What is Physiological Dead Space?

A

Basically alveolar dead space

In healthy persons, physiological dead space is nearly ZERO

32
Q

What is Alveolar Dead Space?

A

Alveoli that receive air, but not blood

33
Q

What is the equation for Physiological Dead Space?

A

Physiological dead space = VT x [(PaCO2 - PECO2)/ PaCO2]

34
Q

When does Anatomical Dead Space enter the lungs?

A

At the end of Inspiration.

Inspired air that fills conducting airways where gas exchange does not occur.

35
Q

Is there air left in the lungs at the end of expiration?

A

Yes, Alveolar air from previous breath is left in the conducting airways.

36
Q

What is the equation for Minute Alveolar Ventilation?

A

Calculated by subtracting dead space volume from tidal volume.

Valv = VT - VDS
500ml - 150 ml = 350 ml

Minute alveolar ventilation is now alveolar ventilation x frequency
(Vdot)alv = VALV x f

37
Q

When is it harder to stretch the lungs?

A

During inhalation at LOW lung volumes.
When the lungs are at LOW VOLUMES, They must work HARD to get a little increase in volume

Also at high lung volumes when nearing TLC

38
Q

When is it easier to stretch the lungs?

A

Inhalation at Normal Lung Volumes (quiet breathing)

Once there is a little air in the lungs, a little pressure change will produce a large volume change.

39
Q

What happens during inhalation at high lung volumes?

A

As lungs expand toward TLC, it again becomes difficult to stretch.

Small pressure changes produce small changes in volume.

40
Q

What does the Pressure/Volume Inspiration graph look like?

A

S shaped curve

41
Q

What does the Pressure/Volume graph look like during Expiration?

A

Increases then levels off

42
Q

What happens when you inflate the lungs with saline rather than air?

Why?

A

Lungs almost inflate and deflate the same way

The difference is SURFACTANT
It reduces tension in the smallest alveoli more than the larger alveoli

LaPlace’s Law

Contributes to hysteresis - the difference between inspiration and expiration.

43
Q

What is compliance?

A

The measure of stretch ability of the lungs

Higher compliance = easier to stretch/open

Calculate = take the slope os the tangent to the pressure/volume curve

Change in volume / change in pressure

44
Q

When is compliance highest?

A

During normal breathing range, normal VT

Reduces workload

45
Q

When is compliance lowest?

A

At either extreme - when lung volume is too small or too large
Harder work

46
Q

What is elasticity?

A

Recoil ability

opposite of compliance

47
Q

Explain a baby’s first breath in terms of compliance

A

Prior to first breath, lung volume is very low, so compliance is low and effort/work is high.

No wonder they cry!

48
Q

What does fibrosis do to compliance?

A

Lowers compliance, so need more change in pressure required for change in volume.

Occurs during disease, obesity, etc

Usually breath at shallower volume and more frequently

49
Q

What does age do to compliance?

A

Compliance increases with age as elasticity decrease with age due to loss of elastin and increased collagen

50
Q

What does emphysema do to compliance?

A

Compliance increases as it destroys alveolar septal tissue that normally opposes expansion

51
Q

What is FRC? (Functional Residual Capacity)

A

When elastic recoil of lungs and that of chest wall balance each other

52
Q

What is minimal volume?

A

What the lungs would shrink to

They want to be smaller

53
Q

What is Interdependence?

A

The structural stability of the small airways and alveoli depends on all the connecting airways/alveoli

CPR Exam 2 (5 decks)

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