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BMS250 > Pulmonary Circulation and Regulation of Ventilation (Week 4) > Flashcards

Pulmonary Circulation and Regulation of Ventilation (Week 4) Flashcards

1
Q

What is the primary function of the pulmonary circulation?

A

To bring venous blood from the superior and inferior vena cava into contact with alveoli for gas exchange.

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2
Q

What are the secondary functions of pulmonary circulation?

A
  • Serves as a filter
  • Acts as a metabolic organ
  • Functions as a blood reservoir.
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3
Q

What is hypoxic pulmonary vasoconstriction?

A

A phenomenon where low oxygen levels increase pulmonary vascular resistance.

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4
Q

What is the total blood volume of the pulmonary circulation?

A

Approximately 500 mL or 10% of the total circulating blood volume.

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5
Q

What is the hemodynamic feature of the pulmonary circulation compared to systemic circulation?

A

High flow, low-pressure, and low-resistance system.

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6
Q

What is the mean pulmonary arterial pressure?

A

15 mm Hg.

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7
Q

What is the driving pressure in pulmonary circulation?

A

10 mm Hg.

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8
Q

True or False: The pulmonary artery and its branches have thicker walls than the aorta.

A

False.

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9
Q

What does the term ‘capillary recruitment’ refer to?

A

The opening of partially or completely closed capillaries to lower overall resistance.

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10
Q

Fill in the blank: Gas exchange in the lungs is primarily affected by _______.

A

blood flow.

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11
Q

What is the effect of exercise on pulmonary vascular resistance?

A

Decreases pulmonary vascular resistance, minimizing the load on the right heart.

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12
Q

What occurs during acute lung injury (ARDS)?

A

Release of histamine, prostaglandins, and leukotrienes causing vasoconstriction of pulmonary arteries.

ARDS = acute respiratory distress syndrome

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13
Q

What role does the bronchial circulation play?

A

Nourishes the walls of the conducting airways and surrounding tissues.

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14
Q

What are the hemodynamic features of pulmonary arterioles compared to systemic arterioles?

A

Pulmonary arterioles have less ability to constrict.

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15
Q

What is the significance of gravity in pulmonary circulation?

A

Gravity causes lungs to be underperfused at the apex and overperfused at the base.

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16
Q

What are the three lung zones based on blood flow and pressure?

A
  • Zone 1: No blood flow (alveolar dead space)
  • Zone 2: Blood flow depends on arterial and alveolar pressures
  • Zone 3: Blood flow depends on normal arterial–venous pressure difference.
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17
Q

What is the relationship between pulmonary vascular resistance and cardiac output?

A

Pulmonary vascular resistance falls with increased cardiac output.

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18
Q

What is the clinical implication of smoking on pulmonary circulation?

A

Destroys alveolar membranes and decreases pulmonary capillary cross-sectional area.

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19
Q

What substances can cause vasodilation in the pulmonary vasculature?

A
  • Nitric oxide
  • Phosphodiesterase type V inhibitors such as sildenafil.
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20
Q

What is the effect of hypoxia on pulmonary vascular resistance?

A

Hypoxia increases pulmonary vascular resistance.

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21
Q

What happens immediately after birth regarding pulmonary circulation?

A

Pulmonary arterioles dilate, reducing vascular resistance and establishing normal lung perfusion.

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22
Q

What is pulmonary edema?

A

Abnormal accumulation of fluid in the alveoli, impairing gas exchange.

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23
Q

What is the role of pulmonary endothelial cells in thrombi prevention?

A

Release fibrinolytic substances to help dissolve thrombi.

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24
Q

What is the effect of acute lung injury on pulmonary circulation?

A

Causes vasoconstriction of pulmonary arteries and endothelial damage.

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25
Q

What is positive airway pressure ventilation?

A

A method used to maintain open airways in patients requiring respiratory support

Positive airway pressure (PAP) is commonly used in conditions like sleep apnea.

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26
Q

What characterizes Zone 2 of lung blood flow?

A

Arterial pressure exceeds alveolar pressure

Blood flow in this zone is influenced by the difference between arterial and alveolar pressures.

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27
Q

What is true about blood flow in Zone 2?

A

Blood flow is greater at the bottom than at the top of this zone.

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28
Q

What defines Zone 3 of lung blood flow?

A

Both arterial and venous pressures exceed alveolar pressure.

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29
Q

What is the outcome of increased arterial pressure down the lung zones?

A

Vessel transmural pressure becomes greater, capillaries become more distended, and pulmonary vascular resistance falls.

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30
Q

What is the primary function of ventilation?

A

To maintain adequate gas exchange to meet the metabolic demands of the body.

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31
Q

What are the main muscles responsible for inspiration?

A

Diaphragm and external intercostal muscles

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32
Q

What triggers muscle contraction in breathing?

A

Nervous stimulation.

33
Q

Under what conditions does involuntary breathing occur?

A

Without any conscious effort while awake, asleep, or under anesthesia.

34
Q

Which brain structures are involved in the respiratory control center?

A

Pons and Medulla.

35
Q

What do apneustic centers control?

A

The depth of inspiration, particularly for deep breathing.

36
Q

What initiates expiration?

A

Switching off the inspiratory activity.

37
Q

What reflex prevents hyperinflation of the lungs?

A

Hering-Breuer reflex.

38
Q

What are the four primary causes of hypoxemia?

A
  • Hypoventilation
  • Diffusion impairment
  • Shunt
  • Ventilation–perfusion inequality.
39
Q

What occurs during hypoventilation?

A

The volume of fresh gas going to the alveoli per unit time is reduced.

40
Q

What are central causes of hypoventilation?

A
  • Impaired control of breathing
  • Depression of the respiratory center by drugs
  • Diseases of the medulla.
  • Abnormalities of the spinal cord.
  • Anterior horn cell disease.
41
Q

What are peripheral causes of hypoventilation?

A
  • Diseases of the nerves to the respiratory muscles
  • Diseases of the myoneural junction
  • Diseases of the respiratory muscles
  • Thoracic cage abnormalities
  • Upper-airway obstruction
  • Severe parenchymal lung disease.
42
Q

What diagnostic feature is always associated with hypoventilation?

A

CO2 retention.

43
Q

What happens in diffusion impairment?

A

The barrier to diffusion is grossly widened.

44
Q

What is an anatomical shunt?

A

Blood bypasses alveoli through a channel, such as a septal defect.

45
Q

What characterizes ventilation-perfusion inequalities?

A

Mismatched ventilation and blood flow in various lung regions.

46
Q

What underlies exercise-induced hyperpnea?

A

A neurologic response with involvement of medullary generators.

47
Q

What occurs during the metabolic phase of exercise?

A

Increase in alveolar ventilation proportional to carbon dioxide production.

48
Q

What is the effect of sleep on breathing?

A

General depression of breathing.

49
Q

What is a characteristic change in breathing during sleep?

A

Breathing frequency and inspiratory flow rate are reduced.

50
Q

What is the compensatory mechanism that allows the respiratory system to sustain ventilation during anaerobic metabolism?

A

Switching from carbon dioxide production to lactic acid production

51
Q

What results from the withdrawal of the wakefulness stimulus from the brainstem reticular formation?

A

Sleep

52
Q

What general effect does sleep have on breathing?

A

General depression of breathing

53
Q

What happens to breathing frequency and inspiratory flow rate during sleep?

A

They are reduced

54
Q

By what percentage does minute ventilation fall during sleep?

A

10% to 15%

55
Q

What is the small rise in PaCO2 during sleep?

A

About 3 mm Hg

56
Q

In healthy individuals, what is the clinical consequence of the small decrease in ventilation and increase in PaCO2 during sleep?

A

Usually of little clinical consequence

57
Q

What are some diseased conditions that make sleep a vulnerable time for respiratory control?

A
  • Respiratory muscle weakness
  • Altered respiratory mechanics
  • Impaired gas exchange in pulmonary disease
  • Abnormal ventilatory drive
58
Q

What often precedes chronic diurnal hypoventilation and hypercarbia?

A

Nocturnal hypoventilation

59
Q

What are the two types of episodes that occur during sleep in sleep-disordered breathing?

A
  • Apneas
  • Hypopneas
60
Q

Define apnea in the context of sleep-disordered breathing.

A

A drop in the peak respiratory signal of ≥90% from baseline for ≥10 seconds

61
Q

Define hypopnea in the context of sleep-disordered breathing.

A

A drop in the peak respiratory signal of ≥50% from baseline for ≥10 seconds

62
Q

What characterizes obstructive sleep apnea (OSA)?

A
  • Cessation of airflow (>10 sec)
  • Oxygen desaturation (SpO2 >-3%)
  • Arousal from sleep
  • Respiratory center remains active
  • Paradoxical movement of chest and abdomen
63
Q

What causes the collapse of the upper airways in obstructive sleep apnea?

A
  • Backward movement of the tongue
  • Collapse of the pharyngeal walls
  • Greatly enlarged tonsils or adenoids
64
Q

What characterizes central sleep apnea (CSA)?

A
  • Cessation of airflow (>10 sec)
  • Oxygen desaturation (SpO2 >-3%)
  • Arousal from sleep
  • Respiratory center is inactive
  • Absence of paradoxical movement of chest and abdomen
65
Q

What is Cheyne-Stokes respiration?

A

Periodic breathing: hyperpnea alternate with apnea

66
Q

What is the pathogenesis of Cheyne-Stokes respiration linked to?

A
  • Increased LV filling pressure
  • Lung congestion
  • Stimulation of J-receptors
  • Hyperventilation
  • Reduction of PaCO2 below the apnoeic threshold
67
Q

What is congenital central hypoventilation syndrome characterized by?

A

Box-shaped facies with decreases in various facial measurements

68
Q

What neurologic diseases are associated with PHOX2B-determined central sleep apnea?

A
  • Shy–Drager syndrome
  • Stroke
  • Myasthenia gravis
  • Neuromuscular disease
  • Bulbar poliomyelitis
  • Brainstem infarction
  • Encephalitis
69
Q

What defines obesity hypoventilation syndrome?

A

Obesity (BMI ≥30 kg/m²) and hypoventilation with daytime hypercapnia in the absence of other causes for hypoventilation

70
Q

What impact does REM sleep have on desaturation in obesity hypoventilation syndrome?

A

The degree of desaturation is greater in REM sleep

71
Q

What is pulmonary edema?

A

An abnormal accumulation of fluid in the interstitial and alveolar spaces of the lung

72
Q

What are the stages of pulmonary edema?

A
  • Stage 1: Interstitial
  • Stage 2: Alveolar
73
Q

What happens during the transition from interstitial to alveolar edema?

A

The lymphatics become overloaded, leading to fluid spilling over into the alveoli

74
Q

What are the clinical features of alveolar edema?

A
  • Severe dyspnea
  • Orthopnea
  • Coughing up pink, frothy fluid
  • Marked opacification on radiograph
  • Severe hypoxemia
75
Q

What is the definition of pulmonary embolism?

A

Thrombi form in large veins and travel to the lungs where they become lodged in and occlude the pulmonary circulation

76
Q

What are the types of pulmonary emboli?

A
  • Venous thrombi
  • Nonthrombotic emboli (fat, air, amniotic fluid)
77
Q

What is cor pulmonale?

A

Right ventricular failure due to excessively high pulmonary artery pressures

78
Q

What are some causes of cor pulmonale?

A
  • Pulmonary emboli
  • Pulmonary vascular disease (e.g., scleroderma)
  • Parenchymal disease (e.g., COPD, pulmonary fibrosis)

BMS250 (15 decks)

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