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Phase 1 Medicine (JA) > Respiratory physiology > Flashcards

Respiratory physiology Flashcards

1
Q

What is Pa02 in arterial blood?

A

90 - 110 mmHg

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2
Q

How much lower is the Pa02 in arterial blood in a supine position?

A

~6 mmHg

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3
Q

Define hypoxia.

A

When the oxygen supplies cant meet the oxygen demand of a tissue

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4
Q

Name the 4 types of hypoxia, and give a brief description. (Which 1 can be corrected with supplemental 02)

A

1) Hypoxaemic hypoxia - low Pa02 (can be corrected with supplemental 02
2) Anaemia hypoxia - Low Hb
3) Stagnant hypoxia - Low perfusion of 02 into tissues
4) Histotoxic hypoxia - Cells cannot use the 02 following perfusion

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5
Q

What is blood Pco2?

A

34 - 36 mmHg

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6
Q

What is hyper/hypocapnia?

A

pCo2 falling outside of the 34-36 mmHg range

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7
Q

What is V’a/Q’>

A

The ventilation perfusion ratio. V’a is the ventilation of the alveoli, and Q is the perfusion of the blood.

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8
Q

What is type 1 respiratory failure?

A

Poor perfusion but good ventilation. Caused by hypoxaemia hypoxia. Due to good ventilation (Va) but poor blood perfusion (Q). Va/Q mismatch. Low oxygenation of blood (<60mmHg; <90% O2 sat). Caused by shunt or pulmonary embolism.

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9
Q

What is type 2 respiratory failure?

A

Poor ventilation but good perfusion. <60 mmHg Pa02; <90% O2 sat. Leads to hypercapnia since CO2 cannot ventilate (50 mmHg). Caused by increased airway resistance (COPD), decreased gas exchange surface (chronic bronchitis) or deformity (kyphoscoliosis) or damage (flail chest).

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10
Q

What is Dalton’s law?

A

In a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases

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11
Q

What is Henry’s law?

A

At a constant temperature, the amount of gas that dissolved into a liquid is directly proportional to the partial pressure of that gas

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12
Q

What do conchae (or turbinates) do?

A

Found within the nose to increase surface area (160 cm2). They are sausage shaped shelves of bone which warms, humidifies and filters inspired air. Turbinate precipitation.

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13
Q

What is Stridor?

A

The sound made on both inspiration and expiration when the upper airways are blocked. Narrowing leads to whistle effect

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14
Q

What is Wheeze?

A

The sound made predominantly on expiration when the lower airways (bronchioles) are blocked. Can cause prolonged expiration

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15
Q

How many lobes do the left and right lung contain?

A

Right contains 3 (Superior, middle, inferior) and left contains 2 (Superior and inferior)

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16
Q

What muscles are required for inspiration?

A

1) External intercostals
2) Diaphragm
3) Sternocleidomastoid
4) Scalenes
5) Serratus anterior

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17
Q

What muscles are required for expiration?

A

1) Internal intercostals
2) Obliques
3) Rectus abdominus

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18
Q

What is relationship between alveolar radius and alveolar surface tension?

A

Alveolar surface tension is inversely proportional to alveolar radius.

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19
Q

Describe the mechanics of lung inflation.

A

1) contraction of the inspiration muscles
2) Rib cage moves upwards and outwards (bucket handle effect)
3) Increased thoracic volume
4) decreased intrathoracic pressure

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20
Q

Describe paradoxical breathing and which injury demonstrates this.

A

Flail chest is when two or more ribs are broken in two or more places. The chest fragment moves in the opposite direction to the motion of breathing.

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21
Q

What is the normal intrapleural pressure?

A

P=-5

22
Q

What is a pneumothorax?

A

Air fills the intrapleural space making it atmospheric. The elastic recoil of the lungs causes them to collapse and for the chest wall to expand.

23
Q

Name two causes of a pneumothorax.

A

Traumatic (blunt, penetrating) & spontaneous (Ruptured bullae)

24
Q

What are the treatments for a tension pneumothorax?

A

The aim is to reestablish the subatmospheric intrathroacic pressure.

1) ACUTE - Needle decompression at the 2nd intercostal
2) LONG TERM - Tube thoracostomy (chest drain, 5th intercostal)

25
Q

Name a treatment for a persistent spontaneous pneumothorax.

A

Pleuridosis - the seal and stick method.

26
Q

What is the total lung volume for males, females and pregnant females?

A

5.8L, 4.2L & 4.0L, respectively

27
Q

Draw the spirometry diagram for a healthy male and include and define all the terms.

A

Total lung capacity (5.8L)

1) Inspiratory reserve volume (forcible inspiration; 3L)
2) Tidal volume (normal breathing; 0.5L)
3) Expiratory reserve volume (Forcible expiration; 1.1L)
4) Residual volume (Air left in lungs after forcible expiration (1.2L)
5) Inspiratory capacity (IRV + TV; 3.5L)
6) Vital capacity (IRV+TV+ERV; 4.6L)
7) Functional residual capacity (ERV+RV; 2.3L)

28
Q

What is the FEV1/FVC? What percent is considered normal?

A

It is the ratio determined by forced spirometry. FEV1 is the volume of air exhaled forcibly in 1 second. FVC is the total volume of air inspired and expired (the peak of the curve). 4L/5L = 80% (normal).

29
Q

What are the 2 types of pulmonary disorder and how to the FEV1/FVC ratio change?

A

1) Obstructive (Emphasema, asthma, chronic bronchitis). FEV1 decreases, <80% FEV1/FVC.
2) Restrictive (TB, Pulmonary fibrosis). FVC decreases, >80% FEV1/FVC.

30
Q

What is the equation for transpulmonary compliance and elasticity?

A

Change in volume/Change in pressure. Elasticity is the opposite of compliance.

31
Q

What is the normal compliance for the lungs? (give units)

A

200 ml/cm H20

32
Q

What 3 things affect transpulmonary compliance?

A

1) Elasticity of lungs
2) Elasticity of chest wall
3) Surface tension

33
Q

Describe a condition of reduced and increased compliance of the lungs.

A

1) Pulmonary fibrosis - stiff lungs, difficult to inflate. reduced compliance
2) Emphysema - elastase enzymes break down elastin. reduced elasticity = increased compliance.

34
Q

Describe emphysema/COPD in terms of compliance and Va/Q?

A

Increased compliance due to reduced elasticity. Va/Q = 0 (type 2 respiratory failure). Leads to Pa < 60 mmHg, hypercapnia (>50 mmHg).

Do not give too much 02, patients may rely on hypoxic response to stimulate breathing. Maintain sats around 90%

35
Q

What is lung hysteresis?

A

The difference between the inspiration compliance and expiration compliance

36
Q

Which equation is the principle driver of breathing?

A

Co2 + H20 <> HCO3 + H+ (carbonic anhydrase)

37
Q

Name the 3 parts required for breathing.

A

1) Central control region
2) Sensors (Chemoreceptors)
3) Effectors (muscles of breathing)

38
Q

Describe neurological control of inspiration and expiration (draw diagram).

A

Expiration - Pneumotaxic area of Pons inhibits inspiration centre of the medulla. Stretch receptors send info along CNX (vagus). Expiration muscles contract.

Inspiration - Apneustic area of pons stimulates the inspiratory centre of medulla. receives info from CNX an CNIX. Inspiration muscles contract.

39
Q

Name two areas of sensory chemoreceptors and where they can be found.

A

1) Central chemoreceptors - ventral surface of the medulla

2) Peripheral chemoreceptors - aortic and carotid bodies (plus stretch receptors)

40
Q

What are the peripheral chemoreceptors sensitive to, and at what range?

A

Decreased Pa02, and 30-60 mmHg

41
Q

What is the pH in the CSF?

A

7.32 (pH change is greatest in the CSF)

42
Q

Where are central chemoreceptors found, and what do they measure?

A

ventral surface of medulla. Increased Co2 in the blood, leads to increased Co2 in CSF, which turns into more H+ and decreases pH. Leads to stimulation for inspiration.

43
Q

Which lung zone represents pulmonary dead space?

A

Zone 1

44
Q

describe the uneven distribution of blood in the lungs.

A

Blood flow reduces towards the apex of the lungs.
Zone 1 - Alveolar pressure (PA) > Arterial pressure (Pa)
Leads to squashed capillaries. Va > Q => 1.
Zone 2 - Smaller alveoli. Blood flow better. Va = Q = 1 better. Pa>PA>Pv
Zone 3 - Smallest alveoli. Best blood flow to the lungs. Best Q > VA = < 1. Describes most lung blood flow.

45
Q

What is hypoxic pulmonary restriction? Give an example as to when this might occur

A

Vasoconstriction of intrapulmonary blood vessels when PAO2 is low. Will shunt blood to better oxygenated areas of the lung. HAPE = High altitude pulmonary oedema

46
Q

Describe the plasma solubility of oxygen and Co2.

A

O2 - Poor plasma solubility, 97% carried by Hb (20 ml/100 ml blood)
CO2 - Greater plasma solubility (but only 2.7 ml/100 ml blood) 7% dissolved, 23% carried by Hb, 70% carried as HCO3-.

47
Q

Draw the Hb/O2 saturation curve, and show where resting pO2 and resting PaO2/Alveolar PA02 sits.

A

Sigmoid curve. Pa02 and PA02 between 90-110 mmHg creates 98% Hb saturation. Resting tissue has p02 of 40 mmHg creating 75% Hb Saturation.

48
Q

In terms of O2/Hb saturation, describe the Bohr effect and Haldane effect.

A

Bohr - Shift right curve. Increased CO2, increased H+, increased temperature weakens affinity of Hb for 02. Leads to increased 02 dissociation. Increased o2 tissue offload.

Haldane - Shift left curve. Decreased Co2, decreased H+, decreased 2,3 BPG, decreased temp increases affinity of Hb for O2. Leads to decreased O2 dissociation. Decreased tissue offload.

49
Q

How many times more affinity for CO does Hb have compared with O2?

A

~250 x.

50
Q

Describe the mechanical features of maternal respiratory function.

A

1) Diaphragm elevation
2) Increased thoracic volume
3) Decreased chest compliance
4) Same lung compliance
5) Increased tidal volume

51
Q

How is a maternal:fetal CO2 gradient created?

A

Decreased sensitivity of CO2 chemoreceptors

52
Q

Describe maternal and fetal Hb O2 saturation.

A

Fetal Hb has a greater affinity for o2 than maternal. Fetal Hb saturation follows the double Haldane effect, where as maternal Hb follows the double bohr effect.

Phase 1 Medicine (JA) (8 decks)

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