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HLB > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

1
Q

What are the two types of respiratory failure that can be caused by hypoventilation?

A

Type 1 and Type 2 respiratory failure.

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2
Q

What does hypoventilation mean?

A

Hypoventilation refers to under breathing.

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3
Q

What is the primary cause of hypoventilation?

A

Inadequate alveolar ventilation resulting in low alveolar pO2 (oxygen) levels and high pCO2 (carbon dioxide) levels.

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4
Q

What are some conditions or factors that can impair the respiratory drive and lead to hypoventilation?

A

Some conditions or factors that can impair the respiratory drive and lead to hypoventilation include head injury, drugs that suppress the Respiratory Centre (such as morphine and barbiturates), respiratory muscle weakness, COPD (Chronic Obstructive Pulmonary Disease), neuromuscular disease, and musculoskeletal disease.

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5
Q

What is the impact of low inspired oxygen (FIO2) on alveolar PO2?

A

Low inspired oxygen (FIO2) leads to low alveolar PO2 (partial pressure of oxygen).

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6
Q

How does the partial pressure of inspired oxygen change at higher altitudes?

A

At higher altitudes, the partial pressure of inspired oxygen decreases.

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7
Q

What is one of the main management strategies for addressing low FIO2?

A

Supplemental oxygen is commonly used to address low FIO2.

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8
Q

What are some methods for delivering supplemental oxygen?

A

Supplemental oxygen can be delivered through various methods, including:

Nasal cannula
Venturi mask
Re-breather mask
Continuous positive airway pressure (CPAP)
Non-invasive ventilation (NIV)
Intubation and ventilation

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9
Q

How does oxygen move from the alveolus to the red blood cells in the lungs?

A

Oxygen diffuses from the alveolus across the basement membrane to the pulmonary capillaries and then diffuses into the red blood cells, where it binds to hemoglobin.

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10
Q

What happens to the oxygen levels in the blood flowing to the lungs?

A

The blood flowing to the lungs in the pulmonary artery is deoxygenated and has a high level of carbon dioxide (CO2).

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11
Q

What is the process of oxygen diffusion based on concentration?

A

Oxygen diffuses from an area of high concentration to an area of low concentration. In health, this process occurs quickly.

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12
Q

How does disease or damage to the basement membrane affect oxygen diffusion?

A

Disease or damage to the basement membrane can reduce the amount of oxygen that diffuses across the interstitium, resulting in hypoxemia (low oxygen levels in the blood).

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13
Q

What is the difference between PAO2 and PaO2?

A

PAO2 refers to the partial pressure of oxygen in the alveoli, while PaO2 refers to the partial pressure of oxygen in arterial blood. In diffusion impairment, PAO2 is normal, but PaO2 is reduced.

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14
Q

How can diffusion capacity be measured, and what is it also called?

A

Diffusing capacity, also known as Transfer Factor (TLCO/DLCO), can be measured using a small amount of carbon monoxide (CO).

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15
Q

What is the Alveolar-arterial gradient used for?

A

The Alveolar-arterial gradient is used to determine if there is a problem with the diffusion process.

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16
Q

What are the factors that can affect the diffusion of gases across the membrane?

A

The factors include the surface area of the membrane, thickness of the membrane, diffusion coefficient of the gas, and the partial pressure and gradient of the gas.

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17
Q

How does emphysema and pulmonary fibrosis affect gas diffusion?

A

In emphysema, the surface area for gas exchange is destroyed, resulting in a decrease in TLCO. In pulmonary fibrosis, the interstitial membrane becomes thickened due to scarring, which also reduces TLCO.

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18
Q

What are the management options for diffusion impairment?

A

The management involves treating the underlying condition if possible and providing supplemental oxygen.

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19
Q

What is an anatomical shunt?

A

An anatomical shunt results in the mixing of venous and arterial blood, accounting for approximately 2% of cardiac output. Examples include deoxygenated blood from bronchial circulation entering the pulmonary veins and deoxygenated blood from the coronary circulation entering the left ventricle via Thebesian vein.

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20
Q

What are the two types of cardiac shunts?

A

Cardiac shunts can be congenital (cyanotic heart diseases) or acquired.

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21
Q

What is a pulmonary shunt?

A

A pulmonary shunt refers to the passage of deoxygenated blood from the right side of the heart to the left side without participating in gas exchange in the pulmonary capillaries.

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22
Q

What are some causes of physiological shunts?

A

Physiological shunts can be caused by consolidation (e.g., pneumonia) leading to hypoxic pulmonary vasoconstriction, as well as arteriovenous malformation (AVM). These conditions result in hypoxemia.

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23
Q

Can providing high levels of oxygen correct a physiological shunt?

A

Giving lots of oxygen may not correct a physiological shunt.

24
Q

What does V in V/Q mismatch represent?

A

V stands for ventilation, which refers to the flow of oxygen into the alveoli.

25
Q

What does Q in V/Q mismatch represent?

A

Q stands for perfusion, which represents the flow of blood to alveolar capillaries.

26
Q

What is the normal V/Q ratio?

A

The normal V/Q ratio is approximately 0.8.

27
Q

How is ventilation (V) measured?

A

Ventilation is measured as the volume of gas inhaled and exhaled over a given time period, such as one minute.

28
Q

How is V (ventilation) calculated?

A

V is calculated as the Alveolar Ventilation Rate (AVR) multiplied by the Respiratory Rate (RR).

29
Q

What is AVR (Alveolar Ventilation Rate)?

A

AVR is calculated by subtracting the alveolar dead space from the tidal volume.

30
Q

What does perfusion (Q) represent?

A

Perfusion refers to the total volume of blood reaching the pulmonary capillaries in a given time period, such as one minute.

31
Q

What is the relationship between perfusion and cardiac output (CO)?

A

Perfusion is equal to cardiac output (CO).

32
Q

How does ventilation (per alveolus) vary within the lungs?

A

Ventilation is lowest at the lung apex because the more negative pleural pressure leads to a higher transpulmonary pressure and more distending pressure on the alveoli. Alveoli at functional residual capacity (FRC) have lower compliance at this higher volume, resulting in less airflow during inspiration.

33
Q

What are the regional differences in ventilation and perfusion in the lungs?

A

Ventilation progressively increases moving lower down in the lung, with ventilation being highest in the lung base. In the lung apex, ventilation (V) is greater than perfusion (Q), while in the middle of the lung, V equals Q. In the lung base, ventilation (V) is less than perfusion (Q). Lung apices are relatively overventilated, while lung bases are relatively overperfused. Hypoxic vasoconstriction in healthy lungs helps minimize V/Q mismatch by directing blood away from poorly ventilated areas.

34
Q

What is the concept of physiological dead space?

A

Physiological dead space is the sum of anatomical dead space and alveolar dead space. Anatomical dead space refers to the upper respiratory tract up to the terminal bronchioles, which do not participate in gas exchange but serve functions such as warming, filtering, and humidification of inspired air. Alveolar dead space refers to alveoli that have lost blood supply and do not contribute to gas exchange. In healthy lungs, physiological dead space is equal to anatomical dead space.

35
Q

What is hypoxic pulmonary vasoconstriction?

A

Hypoxic pulmonary vasoconstriction refers to the constriction of pulmonary arteries in response to alveolar hypoxia. It helps redirect blood flow from poorly ventilated areas to well-ventilated areas of the lungs that are rich in oxygen.

36
Q

How does hypoxic pulmonary vasoconstriction differ from blood flow regulation in other parts of the body?

A

In other parts of the body, blood flow typically increases to areas that are hypoxic to deliver more oxygen to the tissues. However, in the lungs, hypoxic pulmonary vasoconstriction redirects blood flow away from hypoxic or poorly ventilated areas.

37
Q

How is arterial blood gas (ABG) measurement performed?

A

A sample of blood is taken from an artery, typically the radial artery due to its accessibility, although the brachial artery or femoral artery can also be used. The blood sample is then analyzed in an ABG analyzer within a few minutes.

38
Q

How is respiratory failure defined?

A

Respiratory failure is defined as hypoxemia with a PaO2 (partial pressure of oxygen) of less than 8.0 kPa (less than 60 mmHg) at sea level (normal atmospheric pressure).

39
Q

What is Type 1 respiratory failure?

A

Type 1 respiratory failure is characterized by hypoxemia with normal levels of CO2 (carbon dioxide). It is indicated by a PaO2 less than 8.0 kPa and a PaCO2 (partial pressure of carbon dioxide) between 4.5-6.5 kPa.

40
Q

What is Type 2 respiratory failure?

A

Type 2 respiratory failure is characterized by hypoxemia with high levels of CO2 (hypercapnea). It is indicated by a PaO2 less than 8.0 kPa and a PaCO2 greater than 6.5 kPa.

41
Q

What is the difference between acute and chronic respiratory failure?

A

Acute respiratory failure refers to a sudden deterioration in respiratory function, often caused by factors such as infection. Chronic respiratory failure, on the other hand, is a gradual and usually permanent change in respiratory function, commonly seen in conditions like COPD (chronic obstructive pulmonary disease).

42
Q

What is acute-on-chronic respiratory failure?

A

Acute-on-chronic respiratory failure refers to a worsening of existing abnormalities in respiratory function. It occurs when there is a sudden deterioration or exacerbation of respiratory symptoms in individuals with pre-existing respiratory conditions, such as an infective exacerbation of COPD.

43
Q

What is the mechanism of respiratory failure?

A

Respiratory failure can occur due to lung failure, leading to gas exchange failure, which results in hypoxemia. Additionally, pump failure can lead to ventilatory failure and hypercapnia.

44
Q

What characterizes Type 1 respiratory failure?

A

Type 1 respiratory failure, known as hypoxemic respiratory failure, is caused by lung diseases that prevent adequate oxygenation of the blood. In this type, the lungs are still able to eliminate carbon dioxide (CO2), resulting in low levels or normal levels of CO2. However, there is a decrease in oxygen (O2) levels, indicated by a PaO2 (partial pressure of oxygen) less than 8 kPa (60 mm Hg) with normal or low PaCO2 (partial pressure of carbon dioxide).

45
Q

What are the five mechanisms of hypoxemia in type 1 respiratory failure?

A

The five mechanisms of hypoxemia (PaO2 < 8.0 kPa) in type 1 respiratory failure are hypoventilation, low inspired oxygen (FIO2), diffusion impairment, shunt, and ventilation/perfusion (VQ) mismatch.

46
Q

What characterizes type 2 respiratory failure?

A

Type 2 respiratory failure is characterized by both hypoxemia (pO2 < 8.0 kPa) and hypercapnia (pCO2 > 6.5 kPa). It occurs due to the failure of ventilation, resulting in alveolar hypoventilation.

47
Q

What is the difference between acute and chronic type 2 respiratory failure?

A

Acute type 2 respiratory failure can develop within minutes to hours, where renal buffering does not have time to act, leading to a decrease in pH and the development of acidosis. Chronic type 2 respiratory failure, on the other hand, can develop over several days to weeks or months. In this case, the kidneys excrete H2CO3 and reabsorb HCO3-, leading to increased levels of HCO3- and a slight decrease in pH as a compensatory mechanism.

48
Q

What is meant by “acute on chronic” respiratory failure?

A

Acute on chronic respiratory failure refers to a worsening of existing respiratory abnormalities. It occurs when there is an acute deterioration or exacerbation of respiratory function in individuals with pre-existing chronic respiratory conditions.

49
Q

What is the equation for the carbon dioxide (CO2) and water (H2O) reaction in the blood?

A

CO2 + H2O ↔ H2CO3 ↔ H+ and HCO3-. This reaction is catalyzed by the enzyme carbonic anhydrase.

50
Q

What role does HCO3- play in acid-base homeostasis?

A

HCO3- (bicarbonate) is an important buffer that helps maintain acid-base balance in the body.

51
Q

How does type 2 respiratory failure lead to respiratory acidosis?

A

Type 2 respiratory failure results in hypercapnia (elevated levels of CO2), which increases the amount of H+ (hydrogen ions) in the blood. This accumulation of H+ leads to acidosis, causing a drop in pH. If left untreated, severe respiratory acidosis can be life-threatening.

52
Q

What are some common causes of type 2 respiratory failure?

A

Some common causes of type 2 respiratory failure include chronic lung diseases such as COPD, severe chronic asthma, bronchiectasis, and cystic fibrosis. Other causes include chest wall deformities, neuromuscular and peripheral nerve disorders, neuro-muscular lung disorders, and disorders of the respiratory center.

53
Q

What are the management strategies for type 1 respiratory failure (hypoxemia)?

A

The management strategies for type 1 respiratory failure include treating the underlying condition, correcting hypoxemia by providing oxygen, and maintaining oxygen saturation between 94-98%. In severe cases, intubation and ventilation may be necessary.

54
Q

What are the management approaches for type 2 respiratory failure (hypoxemia and hypercapnia)?

A

The management approaches for type 2 respiratory failure involve treating the underlying condition, administering controlled oxygen therapy to maintain oxygen saturation between 88-92%, considering non-invasive ventilation (NIV), and, in severe cases, intubation and ventilation.

55
Q

What are the different types of hypoxia?

A

The different types of hypoxia include cytotoxic or histotoxic hypoxia, circulatory or stagnant hypoxia, anemic hypoxia, and hypoxemic or hypoxic hypoxia. Cytotoxic/histotoxic hypoxia is characterized by reduced ability to utilize oxygen, circulatory/stagnant hypoxia involves reduced ability to deliver oxygen (often due to heart failure), anemic hypoxia is caused by reduced oxygen-carrying capacity of the blood (e.g., carbon monoxide poisoning), and hypoxemic/hypoxic hypoxia is characterized by reduced ability to deliver oxygen due to low arterial oxygen levels (PaO2).

HLB (40 decks)

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