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MEDSCI 205 > Respiratory system > Flashcards

Respiratory system Flashcards

1
Q

Flow equation equation using SA

A

Flow is proportional to the change in pressure x surface area

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2
Q

Organisation of the respiratory system

A

Nasal cavity
Pharynx/Larynx
Trachea
Bronchi
Bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs

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3
Q

Conduction space =

A

dead space

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4
Q

Respiratory zone

A

gas exchange

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5
Q

How is diffusion distance minimized?

A

By proximity and density of capillaries to the air in the alveolus

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6
Q

Static mechanics of breathing

A

Generate flow by creating a pressure gradient

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7
Q

Inspiration mechanics

A

Chest cavity expands in size
Contracting diaphragm, pulls down and flattens out
External intercostal hinge the ribs up and out

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8
Q

Muscles of inspiration

A

Diaphragm
External intercostal

Accessory muscles:
Scalenes
Sternocleidomastoids
Neck and back muscles
Upper respiratory tract muscles

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9
Q

Expiration mechanics

A

Normally passive (elastic recoil)
Active expiration
Abdominal muscles - force diaphragm up
Internal intercostals - pull ribs in and down
Neck and back muscles

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10
Q

Pleural membranes

A

Double layered sac
Allows the lungs to move
Filled with thin layer of fluid (-20um)
Forms connection between lungs and chest wall

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11
Q

Elastic recoil of lungs

A

Inwards

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12
Q

Elastic recoil of chest wall

A

Outwards

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13
Q

Intrapleural pressure

A

Pressure in the pleural cavity
Sub-atmospheric to keep airways open
Will not expand when greater negative pressure is generated

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14
Q

Intra-alveolar pressure

A

Pressure in the alveolar of the lungs

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15
Q

What happens to intrapulmonary pressure during inspiration?

A

During inspiration, intrapulmonary (alveolar) pressure decreases as the lung volume increases, causing the pressure to drop below atmospheric pressure (approximately -1 mmHg relative to atmospheric pressure), allowing air to flow into the lungs.

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16
Q

What happens to intrapulmonary pressure during expiration?

A

During expiration, intrapulmonary (alveolar) pressure increases as the lung volume decreases, causing the pressure to rise above atmospheric pressure (approximately +1 mmHg relative to atmospheric pressure), pushing air out of the lungs.

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17
Q

What changes occur to intrapleural pressure during inspiration?

A

Intrapleural pressure becomes more negative during inspiration (e.g., from -4 mmHg to -6 mmHg) due to the thoracic cavity expanding more than the lungs do, which helps expand the lungs as the vacuum effect pulls them outward.

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18
Q

What happens to intrapleural pressure during expiration?

A

Intrapleural pressure becomes less negative during expiration (e.g., from -6 mmHg back to -4 mmHg) as the thoracic cavity decreases in volume, allowing the lungs to recoil and air to be expelled.

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19
Q

What is transpulmonary pressure and how does it change during inspiration?

A

Transpulmonary pressure is the difference between alveolar pressure and intrapleural pressure (P_tp = P_alv - P_pl). It increases during inspiration as the alveolar pressure decreases more slowly than the intrapleural pressure, facilitating lung expansion.

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20
Q

How does the diaphragm affect pressures in the lungs during inspiration?

A

During inspiration, the diaphragm contracts and moves downward, increasing thoracic cavity volume, decreasing intrapleural and intrapulmonary pressures, and allowing air to flow into the lungs.

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21
Q

What role does elastic recoil play during expiration?

A

Elastic recoil of the lungs is primarily responsible for increasing intrapulmonary pressure during passive expiration by reducing lung volume, which helps to push air out of the lungs.

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22
Q

Compliance

A

How easily the lung expands = change in V/change in P

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23
Q

What happens to lung volume when the pleura is punctured?

A

When the pleura is punctured, air can enter the pleural space, leading to a pneumothorax. This causes the intrapleural pressure to become less negative or even positive relative to atmospheric pressure, disrupting the vacuum that holds the lung expanded. As a result, the lung on the affected side typically collapses partially or completely, reducing lung volume and compromising respiratory function.

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24
Q

Pressure at function residual capacity

A

Pressure in the airways is equal to barometric pressure

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25
Q

Minute ventilation

A

Volume of air shifted in & out of the lungs per minute

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26
Q

Alveolar ventilation

A

Only the volume of air per minute contact with the respiratory surfaces of the lungs

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27
Q

Breathing mechanics

A

Movement of air into and out of the lungs occurs when a pressure gradient is created

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28
Q

Airway resistance definition

A

Change in transpulmonary pressure needed to produce a unit of flow of gas through the airways of the lung

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29
Q

Factors influencing airway resistance

A

Airflow velocity, the diameter of the airway and lung volume

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30
Q

Total airflow resistance

A

The sum of all resistances

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31
Q

How does airflow resistance arise?

A

Friction between gas molecules, & between gas molecules and airway walls

Airway resistance&raquo_space;» viscous tissue resistance

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32
Q

Poiseuille’s Law

A

Relationship for laminar flow in a cylindrical tube

Rate of flow is due to pressure differences
Resistance is proportional to 1/r^4 viscosity and length

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33
Q

Facts of airway resistance

A

Doubling the length of an airway doubles the airway resistance

Halving the radius increases the resistance sixteen-fold

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34
Q

Total airway resistance trends

A

Intermediate sized airways contribute most of the total resistance

Total cross-sectional area increases towards the periphery, whereas total airflow is constant

Flow is more laminar in small airways

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35
Q

Anatomic deadspace

A

Conducting portion of airways

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36
Q

Physiological deadspace

A

Deadspace in respiratory zone

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37
Q

Saline-filled lungs

A

Lungs inflated with saline have a much larger compliance

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38
Q

Air-filled lungs

A

Show the effects of elastic elements and surface tension

Require larger pressures during inflation (hysteresis)

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39
Q

Law of La Place

A

Transmural pressure is directly proportional to surface tension & inversely proportional to radius

Therefore deflating pressure are greater in smaller sphere

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40
Q

Type 1 cells

A

Gas exchange

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41
Q

Type II pneumocytes

A

Secrete surfactant
Many elastic fibres
Many capillaries

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42
Q

Surfactant

A

In the liquid lining alveoli reduces its surface tension along the flat and curved surfaces, reducing, resistance to inflation

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43
Q

Forces that promote lung collapse

A

Natural elasticity of lungs
Lung surface tension
Pleural pressure (from the weight of the lung)

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44
Q

Forces that favour lung expansion

A

Natural elasticity of the chest wall
Surfactant produced by type 2 pneumocytes
Transpulmonary pressure (the difference between the intrapulmonary and intrapleural pressures)

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45
Q

Flow Volume curves - flow and effort at different lung volumes

A

Flow is effort dependent at high lung volumes
Effort independent at low lung volumes

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46
Q

Work

A

Proportional to change in P x change in V

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47
Q

Inspiration works against…

A
  1. Compliance, or elastic work that required to expand the lung against elastic forces (recoil)
  2. Tissue resistance work, i.e that required to overcome the viscosity of the lung and chest wall structures.
  3. Airway resistance work, ie that required to move air through the airways into the lungs

Work of breathing has 2 components: Elastic and frictional

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48
Q
A

0AECDO - Insp work done overcoming elastic works
ABCEA - Insp. work done overcoming airway + tissue resistance
AECFA - Work done on expiration to overcome airway +tissue resistance

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49
Q

Rapid shallow breathing

A

decreases elastic work but increases frictional (viscous) work

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50
Q

Slow deep breathing

A

decreases frictional work but increases elastic work

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51
Q

Respiratory control is an example of what?

A

Negative feedback system

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52
Q

Control of breathing

A

Influences from higher centres influence cycle of expiration & inspiration

Reflexes from lungs,airways, CV system, muscles & joints, skin, arterial and central chemoreceptors affect this which affects the muscles of breathing

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53
Q

Exercise ventilatory response

A

Increases Vt, Fr, Ve
Whereas PaO2 remains normal unit very high exercise level

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54
Q

Partial pressure definition

A

Measure of the concentration of the individual components in a mixture of gases

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55
Q

Dalton’s Law of Partial Pressure

A

Total pressure of a gas is simply the sum of the individual partial pressures (Pi) of each constituent gas

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56
Q

Air we breathe %

A

Inhale
O2 - 20.71
CO2 - 0.04
H2O - 1.25

Exhaled
O2 - 14.6%
CO2 - 4.0%
H2O - 5.9%

57
Q

O2 cascade pathway

A
  1. Oxygen exchange at alveolar-capillary interface
  2. Oxygen transport
  3. Oxygen exchange at cells
  4. CO2 exchange at cells
  5. CO2 transport
  6. CO2 exchange at alveolar-capillary interface
58
Q

Why does the partial pressure of O2 decrease from inspired air to mixed venous blood?

A

Inspired air mixes with dead space air decreasing pressure and O2 is consumed with CO2 pressure increasing as its produced

59
Q

Why are we interested in alveolar gas composition

A

Inspired air contains virtually no CO2. Therefore, the CO2 contained in the alveoli must come from metabolism

However, VCO2 depends not only on how fast O2 is utilized, but also on the kind of fuel metabolised.

60
Q

Metabolism of carbohydrates

A

Produces 1 molecule of CO2 for every O2 consumed

61
Q

Respiratory exchange ratio

A

VCO2/VO2
In steady state R = Respiratory Quotient (RQ)
RQ is measured at the tissue/blood compartment

62
Q

If Ve is equal to Vi

A

If R is equal to 1 during exercise (i.e carbohydrate)

63
Q

Typical R

A

R is more typically 0.8 i.e. 10 molecules of O2 consumed for 8 molecules of CO2 produced

64
Q

Oxygen uptake

A

Oxygen consumption per kilogram of body weight
Most relevant measure of the cardiorespiratory system

65
Q

Maximal oxygen uptake is the…

A

Maximal aerobic capacity, is the maximum rate of oxygen consumption possible by an individual

66
Q

Fick Principle

A

Oxygen consumption is (arterial oxygen content - venous oxygen content) x cardiac output

67
Q

What does the hatched area represent at rest?

A

Hatched area represents the amount of O2 transported in the blood and used in cellular metabolims

68
Q

Perfect lung

A

PAO2 would totally equilibrate to the oxygen in the pulmonary veins and be equal to the PaO2

69
Q

Initial drop in partial pressure

A

Inspired air & air in the upper airway is due to humidification
Smaller drop in PO2 occurs between alveoli & arterial blood

70
Q

Well ventilated lung

A

PACO2 is approximately PaCO2

71
Q

Rest changes in alveolar gas is…

A

Small since VT/FRC is small

72
Q

Changes during hyper and hypoventilation

A

PACO2 decreases in hyperventilation so does PaCO2

PACO2 increases in hypoventilation so does PaCO2

73
Q

Ventilation/Perfusion inequalities from alveoli to arteries

A

Alveoli, capillary and arteries experiences a further decrease between PAO2 and PaO2

74
Q

Ventilation & Perfusion

A

Ventilation in alveoli is matched to perfusion through pulmonary capillaries

75
Q

Ventilation-perfusion ratio

A

V/Q ration takes in account regional variations in VA and capillary perfusion

76
Q

Blood Flow (perfusion) standing

A

When standing, gravitational effects mean that blood flow decreases from the base to the apex of lungs.

77
Q

Blood flow at apex

A

Low arterial pressure in the pulmonary circulation tends to collapse the smaller vessels. Increase in resistance and decreased blood vessels

78
Q

Blood flow at base

A

At base of lungs, higher pressure distends. Lower resistance and increased blood flow

79
Q

Ventilation standing

A

When standing gravitation effects mean that ventilation decreases from the base to the apex of the lung, but to a much lesser extent than the affect on blood flow

80
Q

Pulmonary hypoxic vasoconstriction

A

Decreased tissue PO2 around under ventilated alveoli constricts their arterioles, diverting blood to better ventilated alveoli.

81
Q

Hypoxemia

A

Abnormally low levels of oxygen (partial pressure, content or % saturation) in arterial blood

Diagnosed by large A-a difference in PO2

82
Q

Forms of O2 carried in the blood

A

As a gas in simple solution in the plasma i.e physically dissolved
- 3mL L-1

As oxy-haemoglobin in erythrocytes (RBCs)
-1.34mL O2 g-1 Hb

Haemoglobin hugely increase O2 carrying capacity of blood

83
Q

Which form contributes to PaO2

A

Physically dissolved O2

Oxygen is chemically bound to haemoglobin (& therefore no longer physically dissolved) so exerts no partial pressure, however, the partial pressure of oxygen determines the oxygen that is bound to Hb (% saturation)

84
Q

Henrys Law

A

The amount dissolved is proportional to the partial pressure of the gas, and its solubility

c =ōP

85
Q

Haemoglobin

A

Respiratory pigments increase the O2-carrying capacity of the blood

Increase the O2-carrying capacity of the blood 65-70x

Molecule made up of 2a &2b globin subunits each with 1 haem at the centre. Haem contains iron atom that combines with O2

Hb carries up to 200mL O2 Lblood-1

86
Q

Oxyhaemoglobin

A

O2 bound due to inc. PO2 and dec PCO2 and is relaxed binding structure

87
Q

Deoxyhaemoglobin

A

2,3-DPG to haemoglobin and is caused by increase PCO2, inc 2,3-DPG and dec PO2. It is a tight binding structure and is increased in blood by hypoxia

88
Q

Oxygen content of blood

A

O2 content is the sum of the O2 combined with Hb plus the O2 that is physically dissolved

89
Q

Increased affinity for HbO2

A

Decreased temp
Decrease PCO2
Decreased 2,3-DPG
Increased pH

90
Q

Decreased affinity for HbO2

A

Increased temp
Increased PCO2
Increased 2,3-DPG
Decreased pH

91
Q

Haldane effect: Lungs

A

Binding of Hb with O2 tends to displace CO2 from the blood

92
Q

Bohr effect: Tissues

A

Increase in CO2 causes O2 to be displaced from Hb

93
Q

CO2 excretion

A

From the blood:
CO2 in the lungs
HCO3- in the kidneys

From the body:
Exhalation
Micturition (urine production)

94
Q

Relationship between CO2 and H2O

A

Converted into H2CO3 by carbonic anhydrase which is highly concentrated within RBCs and into H+ + HCO3-. These reactions are reversible and obey the laws of mass action

95
Q

Transport of CO2 in blood

A

7% dissolved CO2 in simple solution
23% protein-bound as HbCO2
70% chemically-modified as HCO3-

96
Q

Total CO2 stored in the body

A

Blood contains only a small part of total CO2 stored in the body - 5L

Much of it is dissolved in fat or stored in bone which total CO2 stored - 100L

97
Q

O2 stores

A

Minute
1.5L in blood + alveoli + myoglobin

98
Q

Control of breathing by autonomic NS

A

Parasympathetic slows breathing rate
Sympathetic increases breathing rate

99
Q

Chemoreceptors

A

Peripheral - located in carotid and aortic bodies. Primarily detect low arterial O2 levels, but can also respond to increased CO2 and H+.

Central - sense pH changes in CNS caused by alteration in PaCO2

100
Q

What is the chief determinant of respiratory drive under normal conditions

A

PaCO2

101
Q

Physiological stresses with immersion of water

A

Body experiences:
increased pressure or hyperbarism, pressure increases 1 atm for every 10m depth

Effects air-filled cavities of the body (Boyle’s Law)

Reduced gravitational effects. Central shift in blood volume. Increased diuresis, Na+ and K+ excretion

Reduced ambient temperature - hypothermia

102
Q

Immersion up to the neck (Respiratory)

A

Positive pressured by surrounding water on the chest wall
Decrease in FRV
Decrease ERV
Slight decrease in VC
IRV increases
Small decrease in RV
Pressure gradient from top to lung base
Increase in work of breathing (60%)

103
Q

Immersion up to Neck: Cardiovascular & Renal

A

Increased venous return, RA pressure, SV & CO
- Increased abdominal pressure
- Decreased peripheral pooling of blood due to decrease gravitational effects
- Vasoconstriction due to reduced temperature

Increased intra-thoracic blood volume
- ADH suppression
- Increased ANP release

104
Q

Boyles Law

A

P1V1 = P2V2

105
Q

Breath-hold diving (voluntary)

A

Limited by oxygen stores
Full inspiration yields - 1L O2 in lungs
Hypoxia alone does not trigger ventilation
Changes associated with the “dive reflex”
Changes in alveolar gas exchange during ascent and descent

106
Q

Breath-hold diving up to 10m - ascent and descent

A

During descent - compression of abdomen. PAO2 maintained, although VO2 decreases

Transfer of CO2 from the blood into the alveoli is compromised during descent, resulting in significant retention of CO2 in the blood

During ascent, theres expansion of abdomen & reversal of pressure. The transfer of O2 from the alveoli to the blood will then be compromised as PAO2 decreased.

107
Q

Free diving adaptations with training

A

Bradycardia
Vasoconstriction of peripheral vessels
Splenic contraction ^ RBC
Plasma accumulates in pulmonary circulation, reducing VR & preventing collapse of lungs at > 30m

108
Q

Shallow water blackout (Latent hypoxia)

A

Loss of consciousness at shallow depth

Occurs within 5m of surface where expanding lungs literally suck oxygen from the divers blood

Blackout occurs quickly, victims die without any idea of their impending death

109
Q

Pre dive hyperventilation

A

Increases risk of SWB by increases PaCO2 level at the start of the dive

110
Q

Barotrauma

A

Rapid ascent from a dive may cause barotrauma
Most serious is pulmonary barotrauma
If a lung/alveoli is obstructed during ascent, then expansion can cause pneumothorax
Rapid ascent can lead to gas bubbles in the joints

111
Q

Decompression sickness

A

During descent increased partial pressure of inert gases causes greater uptake of dissolved gases by the tissues

Diver needs to ascend slowly to allow gases dissolved in tissues to pass back into the lungs (Arterial gas embolism)

112
Q

Nitrogen narcosis

A

Nitrogen is poorly soluble in water and blood, but much more soluble in lipids, and hence cell membranes, and importantly, neurological tissues.
At depth, N2 acts as an anesthetic

113
Q

Hypobaric exposure

A

Decrease in air around you

114
Q

Changes in PB

A

As altitude increases, barometric pressure (PB) decreases

Fewer molecules of O2 per unit volume of inspired air

A fall in PAO2 is therefore predicted by the alveolar gas equation

115
Q

Compensatory responses to altitude hypoxia - chemoreceptors

A

Ventilation is stimulated by peripheral chemoreceptors sensitive to PaO2

Result of increased volume of alveolar gas is to decrease PACO2, allowing an increase in PAO2

However, the decline in PaCO2 reduces stimulation of central chemoreceptors, counteracting the initial hypoxic response

116
Q

Changes in PO2 along the pulmonary capillary at rest (high altitude)

A

At high altitude, change in PO2 between alveolar and mixed venous is less, therefore reducing the pressure gradient for diffusion.

117
Q

Acute response to very high altitude
Physiological responses

A

Hyperventilation and consequent lowering of PaCO2
Increased heart rate
Increased plasma urinary catecholamines
Increased cardiac output
Effects on cerebral function (loss of consciousness with severe hypoxia)
Alterations to regional blood flow in lungs due to selective hypoxic vasoconstriction.

118
Q

Time course of altitude effects: Initial

A

Hyperventilation & hypocapnia followed by reflex inhibition of ventilation

119
Q

Time course of altitude effects: Acclimatization

A

Achieved through reduced HCO3- reabsorption & conserving H+
Result is compensated respiratory alkalosis

120
Q

High altitude adaptation/acclimatisation

A

Primary disturbance
Decrease PaO2
Environmental hypoxia
Leads to increased pulmonary ventilation
Leads in increased PaO2 and decreased PaCO2
Causes secondary disturbance increasing blood pH
Increased renal excretion of bicarbonate lowering blood pH

121
Q

Hypoxia leads to…

A

Increased pulmonary ventilation leading to increased PaO2, increasing organ oxygen delivery

Increased CO - increased blood flow increasing organ oxygen delivery

Increased blood vessel density - increased blood flow increasing organ oxygen delivery

Increased renal sodium and water excretion - increased RBC increasing organ oxygen delivery

122
Q

How do we increase body’s oxygen level (organ changes)

A

Lungs - increase breathing
Heart - Increased cardiac output
At the organs - Increase blood flow, increase capillary density
Blood - Red blood cells count

123
Q

Increased cerebral blood flow

A

May contribute to headache and AMS

124
Q

What improves arterial blood O2, oxygen delivery, aerobic exercise performance?

A

Increasing:
Erythropoiesis
Muscle capillary density
Haemoglobin
Haemoconcentration

125
Q

High altitude adaptations of blood, muscles, respiratory system

A

Blood: Increased haemoglobin-oxygen affinity and plasma volume

Muscles: Decreased mitochondrial volume density and muscle cross sectional area. Increased muscle capillary density and increase myoglobin concentration and decreased oxygen consumption during exercise

Respiratory : Increased ventilation efficiency and lung size

126
Q

Acute mountain sickness

A

Depends on:
Speed of ascent
Altitude reached
Physical exertion
Individual factors

Can develop into life-threatening high altitude cerebral edema and high altitude pulmonary edema

127
Q

High altitude cerebral edema

A

Excessive increase in brain blood flow

128
Q

Hypoxic exposure - pathology

A

Causes the blood vessels inside the lungs to constrict which leads to pulmonary hypertension

Too much pressure inside the lungs leads to fluid build up, which further exacerbates hypoxemia.

129
Q

Treatment of acute mountain sickness

A

Acetazolamide (Diamox)
Increases diuretic effects, CO2 retention and ventilation

130
Q

Dexamethasone

A

Decreases AMS severity

131
Q

Calcium channel blockers

A

Decreases pulmonary vasoconstriction

132
Q

Chronic mountain syndrome symptoms

A

Deep purplish color of lips and gums
Clubbing of the fingers
Marked cyanosis in nail beds and palms of the hands
Vein dilatation of lower limb

133
Q

Chronic mountain sickness - hypoventilation

A

Hypoventilation decreases SaO2. Leads to chronic hypoxia - induces pulmonary hypertension then right heart then left heart failure

134
Q

Development of acute mountain sickness can lead to

A

Can develop into life-threatening high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE)

135
Q

Cerebral edema

A

High altitude cerebral edema is due to excessive increase in brain blood flow

136
Q

Chronic high-altitude maladaptation

A

Increased red blood cell count - excessive erythrocytosis

Severe hypoxemia

137
Q

Alveolar ventilation equation

A

Alveolar Ventilation=(Tidal Volume−Dead Space Volume)×Respiratory Rate

138
Q

Result of high altitude acclimatization is called?

A

Respiratory alkalosis

MEDSCI 205 (7 decks)

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