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Respiratory Block > Shunts and Hypoxic Mechanisms > Flashcards

Shunts and Hypoxic Mechanisms Flashcards

1
Q

What is a physiologic shunt?

A

When 2% of the blood is diverted and bypasses the pulmonary capillaries.

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2
Q

Describe the way a physiological shunt happens via the heart?

A

The capillaries that go in the heart wall ( thebesian veins) can dump right into the left ventricle (and would mix with the oxygenated blood and go out with aorta)

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3
Q

How does the physiological shunt happen via the lungs?

A

The bronchial arteries can anastomose right into the pulmonary veins which carry oxygenated blood.

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4
Q

What are some pathologic shunts that can happen?

A

Atrial septal defect, Ventricular septal defect

Ductus Arteriosus

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5
Q

What is a ductus arteriosus?

A

Ductus arteriosus is when there is a connection between the aorta and pulmonary artery that didn’t go away from birth. (Aorta to eat pulmonary artery).

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6
Q

What is the right to left shunt?

A

Blood flows from the right heart to the left heart.

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7
Q

What is left to right shunt?

A

When the blood on the left flows to the right.

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8
Q

What happens in left to right shunt regarding blood? Describe the process:

A

When the right to left shunt happens, there is mixing of oxygen poor blood with oxygen rich blood on the left. It can basically cause there to be low arterial oxygen that is in the aorta and goes to the body.

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9
Q

How is hypoxia detected and then what is the compensation?

A

Central chemoreceptors in the brain detect CO2 levels and cause there to be hyperventilation to compensate.

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10
Q

What is the shunt fraction?

A

The amount of shunted blood over the total blood flow

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11
Q

What is the formula for shunt fraction equation?

A

Ca02 = CvO2 + CCo2

O2 content of cardiac output=
O2 content of cardiac shunt + O2 content of pulmonary capillary

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12
Q

What is anoxia?

A

no oxygen

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13
Q

What is hypoxemia?

A

low arterial blood PO2.

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14
Q

What is hypoxia?

A

Not enough oxygen for tissues

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15
Q

What is the cause of hematologic hypoxia?

A

Low Hb binding/carrying capacity.

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16
Q

What is the cause of ischemic hypoxia?

A

Impeded arterial flow. Decreased blood flow but O2 saturation is normal.

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17
Q

Histotoxic hypoxia is when

A

Tissues cannot process O2 Ex: Cyanide binds to complex 4 of Cytochrome C Oxidase

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18
Q

What can be the hypoxemia?

A

With the normal A-a gradient, it can be due to high altitude and hypoventilation.

With an increased A-a gradient: V/Q mismatching, diffusion limitation, right to left shunt.

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19
Q

What is the cause of hypoxia?

A

Low cardiac output, anemia, CO poisoning.

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20
Q

How can fires cause hypoxemia?

A

It can reduce the fraction of inspired oxygen because more carbon dioxide and other chemicals and less in the air (FI02 decreases)

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21
Q

How can high altitude can cause hypoxemia how?

A

Has the same fraction of O2 particles they are just more spread out which cause less partial pressure of O2.

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22
Q

What will happen to the blood cell in the hypoxic conditions:

A

Both of these will require the blood cell to travel farther in the lung capillary to collect adequate O2 (100mmhg).

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23
Q

How is shunting and zone of the lung related?

A

Shunting does not occur in the top of the lung as there is ventilation but no perfusion. Shunting occurs on the bottom of the lung as there is perfusion but no ventilation.

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24
Q

What are the two causes of pathological anatomic right to left shunts?

A

Pathological anatomical left to right shunt can be caused by tetralogy of fallot and foramen ovale.

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25
Q

What can cause a physiological shunt due to anatomy?

A

Thebessian veins that bypass that bypasses the lung and drain into the left heart (not including coronary sinus).

Bronchial/pleural vein anastomoses.

26
Q

Will 100% O2 support help for physiological anatomical shunts?

A

No

27
Q

When can 100% O2 saturation help?

A

When there is V/Q mismatch with low 02 ventilation but adequate perfusion.

28
Q

What is the alveolar-arterial gradient?

A

The difference between the amount of oxygen in the blood determines how well oxygen is getting into the blood stream.

29
Q

What is the normal Alveolar- Arterial gradient?

A

5- 15%

(100 X (A-a/PAO2)

(Age/4 +4)

30
Q

If the gradient is larger than it should be, that means that blood is —– and more——

A

Blood is less oxygenated than it should be and is there is more shunting.

31
Q

What is the formula for the PA02?

A

PAO2= (Patm- 47) times FIO2 -PaCO2 [FIO2 + (1-FIO2)/R]

or 150 mmhg - 1.2 (PaCO2)

32
Q

How to measure shunt?

A

You first take arterial blood gas and get results, and then you get use alveolar gas equation.
then check normal for age range.

33
Q

How is breathing controlled?

A

Breathing is controlled by feedback/signals received from multiple areas known as central pattern generator.

34
Q

What are components of the central pattern generator?

A

They are chemoreceptors, mechanoreceptors, respiratory groups located in the brainstem, and emotional brain centers.

35
Q

Where and what are chemoreceptors?

A

They are the central and peripheral chemoreceptors that basically that provide feedback to influence the ventilation rate.

36
Q

What are the types of mechanoreceptors and what do they do?

A

The types of mechanoreceptors are slowly adapting, quickly adapting, and J receptors. They send information about irritation, position, pressure/tension ,and stretch to to brain stem about inspiratory and expiratory muscles.

37
Q

What do respiratory groups located in the brainstem do?

A

They receive information from the receptors and then send information about inspiration and expiration to inspiratory muscles.

38
Q

What is the function of the emotional brain centers?

A

They change the neural signal to the brainstem that can alter respiratory groups in the brainstem .

39
Q

Breathing can be modified further by affecting respiratory motor neurons (phrenic/spinal nerves) in which ways?:

A

Voluntary control: we can choose to hold our breath.

Skeletal muscle receptors: physical activity can modify signals (swinging arms/running may change breathing pattern)

40
Q

Chemo Receptors are located where?

What are chemo receptors sensitive to?

A

Location in brain parenchyma bathed in CSF.

Sensitive to arterial PaCO2 and pH.

41
Q

How is PaCO2 sensed by central chemo receptors?

A

The chemoreceptors basically sense the acute changes in PaCO2 as the H+ and HCO3 cannot cross the BBB. The changes in partial pressures of oxygen triggers respiratory drive changes aimed at maintaining normal partial pressures.

The increase in CO2 levels in blood decreases CSF pH, increasing signal activity to brainstem, increasing ventilation.

42
Q

How so central chemoreceptors work?

A

They are glomus cells which are sensitive to PaCO2, PaO2, and pH.

They sense the change in the O2, causing there to be increased afferent signal to the brainstem, causing increased breathing.

43
Q

Where are the carotid bodies located?

A

They are located on aortic body (aortic to vagus nerve)

44
Q

What are the pumps involved in glomus cells?

A

The K+ pump is inhibited and L type calcium pumps open causing depolarization.

45
Q

What are some things mechanoreceptors help sense?

A

They help sense what is happening in lungs in general. Also sense pneumothorax, pollution, pulmonary embolism, pulmonary edema.

46
Q

What are the names of the two main Hering-Beur Reflexes?

A

Inflation Reflex and Deflation Reflex

47
Q

What is the inflation reflex?

A

The inflation reflex is when too much inflation is sensed by SAR which signals DRG, which uses alpha pathway to decrease inspiration. (important in infants)

48
Q

What is the deflation reflex?

A

Deflation reflex is when when rapid deflation (pneumothorax) is sensed by RAR of epithelium which send more signals to DRG to increase inspiration.

49
Q

What is criteria for H-B reflex for adults?

A

If TV> 800 ml

50
Q

What is the dorsal respiratory group function?

A

It is the inspiratory center. It controls Eupneic breathing by sending signals to diaphragm and external intercostals.

51
Q

What does DRG receive signals from?

A

Nucleus Tractus Solitarus: helps to determine characteristic of inhalation (Hering-Breur reflex and chemoreceptors)

Pre-Botzinger Complex: located in VRG.

52
Q

Ventral Respiratory Group

A

It is the expiratory center that sends signals to abdominal muscles and internal intercostals for forced expiration.

53
Q

Where are mechanoreceptors located?

A

They are located in the airway smooth muscle and respond to lung inflation–> termination of inspiration (Hering-Breuer Inspiratory -Inhibitory reflex)

54
Q

What are the irritant receptors?

A

They respond to noxious gasses; particulates via CN X –> coughing, broncho-constriction

55
Q

Juxtacapillary (J) receptors do what and where are they located?

A

Located in alveoli, near capillaries.

Respond to capillary engorgement –> increase respiratory rate.

56
Q

What does VRG?

A

Expiratory center, located in ventral medulla.

Inactive during basic, quiet breathing.

Provides high respiratory drive when ventilation needs to increase.

57
Q

Pneumotaxic Center?

A

located in upper pons, limits inspiration by inhibiting DRG.

58
Q

Apneustic center does what?

A

Located in lower pons and prolongs DRG inspiratory signal.

59
Q

What is an X-Ray?

A

a composite shadow gram that is a flat image of 2D space.

60
Q

Normal X-ray are taken from which direction?

A

From posterior to anterior

61
Q

What are the 5 densities of plain radiographs?

A 
Bone: +500 HF units 
Soft-tissue: +50 HF units 
Water: 0 HF 
Fat (dark gray): -50 HF units 
Air (Black): 1000 HF units.
62
Q

CT, Ultrasound, PET care used to diagnose what respectively?

A

CT: Interstitial lung disease/ Pulmonary fibrosis, mediastinal mass (with contrast)

Ultrasound: DVT in extremities

PET: lung mass or V/Q scan for pulmonary embolism

Respiratory Block (12 decks)

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