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Medical Physiology > Respiratory Physiology I > Flashcards

Respiratory Physiology I Flashcards

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USMLE® Step 1 flashcards
1
Q

What is the Difference in PO2 and PCO2 in the mixed venous blood going into the lung? Saturation?

A

PO2 - 40 mmHg
PCO2 46 mmHg

75 %

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2
Q

What is the Difference in PO2 and PCO2 in the arterialized blood going away from the lung? Saturation?

A

PO2 - 100 mmHg
PCO2 - 46 mmHg

97.4%

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3
Q

What are the major controls for ventilation?

A
  • Central Chemoreceptors for pH and CO2
  • Peripheral O2, CO2, and pH
  • Higher brain centers
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4
Q

Where are peripheral chemoreceptors located?

A
  • Carotid body off of arterial carotid
  • Aortic bodies
  • Subclavian artery
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5
Q

What is normal Total Ventilation? Alveolar Ventilation?

A

Qt: 6 L/min

QA: 4.2 L/min

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6
Q

How physiological dead space calculated?

A

VDCO2 = TV(PACO2 - PECO2) / PACP2

TV - Tidal Volume
PACO2 - Alveolar Partial pressure CO2
PECO2 - Expired Partial pressure CO2

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7
Q

How is the effective driving force between the alveolus, capillary, and interstitium calculated?

What is the effective driving force from the pulmonary capillary to the intrapleural space?

A

dPeff = TMP - σ Δπ

σ - Reflection Coefficient

π - Oncotic Pressure

8 mmHg

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8
Q

Describe the balance of fluid needed in the intrapleural space. What are the results of imbalance?

A

Too little fluid —> Rubbing and pain

Too much fluid —> layers come apart (Pleural effusion) —> Intersitial edema —> Alveolar flooding

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9
Q

What is normal Tidal volume? Normal anatomic dead space? How does anatomical dead space relate to weight?

A

TV = 500 ml

ADS = 150 ml

Or

1 ml / Lb

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10
Q

What is FRC?

A

Functional reverse capacity

FRC = ERV (Expiratory reserve volume) + RV (Residual Volume)

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11
Q

What is vital capacity?

A

VC = IC (Inspiratory capacitance0 + ERV (Expiratory Reserve Volume)

“Everything - RV”

“Everything that you can breath in or out”

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12
Q

How is helium dilution used to measure FRC and RV? How is FRC calculated? RV?

A
  • Helium spirometer used and valve is closed.
  • At end of tidal expiration/ beginning of FRC equilibrium, valves is removed.

Initial He = Final He

He lungs + He Spiro = He in combined

0 + 0.10*3000ml = 0.5(FRC + 3000)

FRC = 3000

RV = FRC - ERV (ERV calculated by standard spirometry)

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13
Q

How is FRC measured by Plethysmography?

A
  • Person put into airtight box
  • Measure airway Pressure and Box pressure
  • At end of inspiration , Person breathes in and volume of lung and pressure changes
  • Use Boyles law to calculate FRC or initial volume

PV = P’ (V + dV)

dV calculated by Change in pressure
Where dP (Measured) = k*dV
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14
Q

Differentiate Use for He dilution vs Body Plethysmography.

A

He dilution —> Communicating Gas Volume; Lung gas that can mix with the breathing mixture

Plethysmography —> Total Gas Volume; Gas that is or is not in communication with alveoli

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15
Q

How is alveolar pressure calculated?

A

Palm = Prec + Pe

Or

Alveolar = Recoil + External (Intrapleural or intrathroacic)

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16
Q

What is Body Surface pressure?

A

Pressure acting on the body outside of atmospheric.

Ex. Swimming in water, car on chest

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17
Q

How is trans-lung Pressure calculated?

A

Ptl = Palv - Ppl = Prec

Or

 = Palv - Pth
18
Q

What is transwall pressure?

A

Ppl - Pbs

19
Q

How is compliance calculated?

A
  • dV/dP (transmural pressure)
20
Q

What happens tp 2/3 of the work used in inspiration?

A

Elastic - Recovered by the lungs via expiration

21
Q

How is 1/3 of work in inspiration lost?

A

4/5 —> Resistance

1/5 —> Overcoming tissue viscosity

22
Q

What does the chest wall elastic force do? When is Chest force = 0?

A

Tends to expand lung for most lung volumes

Approximately 70% TLC

23
Q

What are the primary characteristics of RDS?

A
  • Low surfactant
  • increased surface tension
  • Muscular fatigue to reopen Alveoli
24
Q

Differentiate Valsalva and muller maneuvers. Associated dangers?

A

Valvalva —> Forced Expration against closed glottis
- Lg (-) Pressure causes large transmural pressure —> Hemorrhage

Muller- Forced Inspiration against closed glottis

Large (+) pressure

  • > Lung rupture
  • > Aortic +BP, - HR
  • > Vena Cava -VR
25
Q

How does Valsalva affect BP + HR, and what are the phases associated?

A

Phase I (Start of Valsalva)

  • Sharp spike in MBP
  • Baroreceptor mediated - HR

Phase II:

  • Decrease in MBP
  • -BP —> +HR

Phase III (End maneuver)

  • Normalized Pth
  • Precipitous BP drop and Reflex +HR

Phase IV:

  • Venous Return to normal -> + SV and CO
  • BP overshoot
  • Baroreceptor reflex -HR
26
Q

Where is resistance greatest in the respiratory system?

A

Upper airway

27
Q

How is total vascular resistance calculated in the respiratory system?

A

Extra-alveolar resistance

transmural pressure) + Alveolar (Capillary compression

28
Q

Where is Total vascular resistance minimal?

A

FRC

29
Q

What causes less vascular resistance at the base of the lungs?

A

Increased Transmural pressure

30
Q

When does the the difference in downstream/upstream pressure not equal flow?

A

When the vessel is collapsible

31
Q

What is the EPP?

A

Equal Pressure Point: The point along the airway where intrapleural pressure = Pressure inside the airway

32
Q

What is significant about the EPP?

A

Past the EPP, vessels are collapsible and flow is determined by Prec / Rx or Recoil pressure / REsistance. Normally, it is calculated by Palv - Ppl / rx

33
Q

Differentiate Obstructive vs restrictive airway disease.

A

Obstructive - Abnormal Increase in R

Restrictive - Abnormal decrease in C
Ex. More difficult to expand, greater recoil force

34
Q

What is characteristic of Emphysema?

A
  • Obstructive airway disease
  • Alveolar tissue loss
  • Air space increase
  • Lungs more compliant
  • Low recoil - more difficult to expire
35
Q

What are example of restrictive airway disease?

A

Interstitial fibrosis:

  • Alveolar tissue stiffer
  • less compliant

Allergic Alveolitis
- Alveoli wall thickens

Pleural effusion

  • Intrapleural fluid buildup
  • Pleural fibrosis and rigidity
36
Q

What are common causes of restrictive lung disease?

A

PAINT

Pleural

Interstitial

Alveolar

Neuromuscular

Thoracic/extra thoracic pressure

37
Q

What is the main feature of restrictive lung disease on the TV vs Pressure graph?

A

Lower slope of the line going from start of inspiration to start of expiration.

38
Q

What is the main feature of obstructive lung disease on the TV vs pressure graph?

A

Same slope of line, but greatly increased area and curves between points

39
Q

What is FEV1?

A

The volume expired after one second

40
Q

What is the partial pressure of O2 in dry air? Humidified air in the trachea?

A

Dry Air - 160 mmHg

Humidified Air - 150 mmHg

41
Q

What are the pressure of O2, CO2, and H2O in arterial blood crossing by the alveoli?

A

PO2 - 100 mmHg
PCO2 - 40 mmHg
PH2O - 47 mmHg

Medical Physiology (43 decks)

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