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Medical Physiology > Respratory Physiology II > Flashcards

Respratory Physiology II Flashcards

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USMLE® Step 1 flashcards
1
Q

How is alveolar ventilation calculated?

A

PaCO2 = CO2 / Alveolar ventilation

= K X Vco2/Qa

K = .863 ml/min

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2
Q

Differentiate Hypo/hyperventilation

A

Hypo -> If ratio is high, PA CO2 rises

Hyper -> If ratio is low, PaCO2 is low

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3
Q

What is normal alveolar ventilation?

A

4.3 L/min

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4
Q

What is the alveolar gas equation?

A

PaO2 = (Patm - 47) X FIO2 - PACO2[FIO2 + (1-FIO2)/R]

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5
Q

How is PAO2 calculated at seal level on room air?

A

PAO2 = 150 - (1.2 X PACO2)

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6
Q

How is transmural pressure and compliance different for alveoli at different parts of lung?

A

Lower down:

  • Higher pressure
  • Less transmural pressure
  • Higher compliance
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7
Q

What is the time constant?

A

A measure of the rate of change of filling and emptying of the lungs

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8
Q

What is the total amount of O2 carried in the blood?

A

20 ml O2/dL

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9
Q

How much O2 does a human need delivered per minute?

A

300 ml O2/dl/min

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10
Q

What four main factors determine diffusion of O2 across the membranes?

A
  1. Area
  2. Thickness
  3. dP
  4. Diffusion coefficient
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11
Q

How is Lung Diffusion capacity calculated?

A

DL = ml O2/min f/ Alv to blood / PAO2 - PaO2

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12
Q

How does reduced ventilation affect changes in blood content and pressure for O2 vs CO2?

A

O2 concentration changes very little with decreased ventilation and decreased pressure

CO2 concentration changes much more with changes in CO2 Pressure and decreased ventilation

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13
Q

What is Hypoxemia?

A

Low PaO2

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14
Q

What are factors which cause Hypoxia and/or hypoxemia?

A

Low FIO2 —> Fire

Low pATM

Low QA —> Airway resistance

Low V/Q

Low DL

R-L Shunt —> Bypasses alveoli

Hematological Hypoxia —> Anemia/ CO poisoning

Ischemic Hypoxia —> Low Systemic blood flow to area

Histotoxic Hypoxia —> Cyanide poisoning

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15
Q

How does V/Q differ from base to top of lung?

A

Top: Lower Perfusion than ventilation; High V/Q

Bottom: Higher perfusion and higher ventilation, but Vis lower than Q; Low V/Q

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16
Q

What occurs from a change in CO2?

A

Increase: Hypercapnea —> Respiratory Acidosis

Decrease: Hypocapnia —> Respiratory Alkalosis

17
Q

How does a pulmonary embolism affect V/Q?

A

Blocked vessel —> Less perfusion and Hypoxemia —> Lower V/Q

18
Q

How does hyperventilation affect V/Q?

A

Increased Ventilation —> Hyperoxemia + Hypocapnia —> Increased V/Q

19
Q

What is Hypoxia vasoconstriction?

A

When alveoli have low perfusion, Veins will constrict and shunt blood to other alveoli

20
Q

What makes up the physiological shunt?

A

Anatomical shunt + Intrapulmonary shunts

Intrapulomonary shunts —> Zero gas exchange; Low V/Q, etc

21
Q

How is acceptable A-a gradient calculated?

A

Age/4 + 4

22
Q

What do the peripheral chemoreceptors sense?

A
  • O2
  • CO2
  • pH
23
Q

What do central chemoreceptors sense in the blood?

A
  • CO2

- pH

24
Q

What is the pre-botzinger complex?

A

Possible pacemaker region in VRG.

25
Q

Describe the Pontine Respiratory group.

A

Pneumotaxic Center:

  • Some Neurons active in Inspiration and Expiration
  • Role in switching off/limiting inspiration
  • Damage —> Apneusis (Prolonged inspiratory spasms)
  • Fine tunes breathing
26
Q

What s the primary role of the DRG?

A
  • Inspiratory center of breathing
  • Basic rhythm is generated
  • Contains NTS (CN IX and X)
27
Q

What are the three major types of receptors in the lungs?

A

SAR (Slow adapting): Apex

RAR (Rapidly adapting): Apex; Chemical/irritant reflex

C Fiber (J-receptors): Base

28
Q

What is the Hering Breuer Inflation reflex?

A
  • Impulses to inspiratory muscles are decreased
  • Reduces inspiration duration; TV; prevents overdistention

*Overinflation —> SAR activation —> DRG Inhibitory pulses via Vagus

29
Q

What is the Hering-Breuer Deflation reflex?

A
  • Less stretch receptor activity causes reflex which promotes increases TV and RR
  • Pneumothorax —> RAR activation
  • Triggger for Sighs; Infant FRC regulation
30
Q

How does ventilation change as PaCO2 increases?

A
  • As PaCO2 increases, higher value of PaCO2 will cause a greater increase in Ventilation
  • The same change of PaCO2 at higher values will cause much greater increase in ventilation
31
Q

What is the body’s responses to atmospheric hypoxemia?

A
  • Peripheral chemireceptors increase ventilation
  • Polycythemia: Increase O2 carrying capacity
  • P50 shift to right: Better unloading
  • Increased capillary density

Medical Physiology (43 decks)

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