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Phase 1 Flashcards > Lung physiology > Flashcards

Lung physiology Flashcards

1
Q

What does the respiratory pump do?

A

Generates a negative intra-alveolar pressure- moves 5 litres/ minute.

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2
Q

What is transpulmonary pressure? Rib movements?

A

Difference in pressure between the inside the outside of the lung (alveolar- intrapleural pressure.)
Pump and water handle.

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3
Q

Most important inspiratory muscle during normal quiet breathing? Impulses stimulating contraction via phrenic nerve arising from where?

A

Diaphragm.

C3, 4 and 5

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4
Q

External intercostal muscles activated by what? As thorax expands, transpulmonary pressure does what?

A

Motor neurones in the intercostal nerves. Becomes more positive.

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5
Q

Expiration at rest is what kind of process? Forced expiration from what?

A

Passive- relies only on relaxation of external intercostal muscles, diaphragm and elastic recoil of lungs.
Internal intercostal and abdominal muscles contract- diaphragm further up into thorax decreasing thoracic volume.

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6
Q

Which airway provides the greatest resistance?

A

Trachea- smaller surface area than all bronchioles.

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7
Q

What is dead space? Occurs where?

A

Volume of air not contributing to ventilation- around 175ml in total. Between the alveoli and capillaries.

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8
Q

What 7 layers must O2 diffuse from alveoli into pulmonary capillaries and CO2 in opposite direction?

A

Alveolar epithelium– tissue interstitial– capillary endothelium– plasma layer– red cell membrane– red cell cytoplasm–haemoglobin binding.

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9
Q

To be most efficient, what must be available to each alveolus? Mismatching known as what?

A

Correct proportion of ventilation and perfusion.

Ventilation- perfusion inequality.

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10
Q

What is the main effect of this inequality? What other factor affects this?

A

Partial pressure of oxygen is decreased in systemic-arterial blood.
Gravitational effects- to increase filling of blood vessels at bottom of the lung.

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11
Q

Two extremes of this inequality?

A

1) Ventilated alveoli but no blood supply due to e.g. blood clot= dead space.
2) Shunt= blood flow but no blood supply due to collapsed alveoli.

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12
Q

What is hypoxic pulmonary constriction?

A

Mucous plug blocks small airways– decrease in alveolar PO2 and in area around– vasoconstriction– diverts blood away from poorly ventilated area.

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13
Q

Second response used to improve ventilation- perfusion mismatch? Due to what?

A

Local bronchoconstriction.
Local decrease in blood flow– less systemic CO2 and decrease in partial pressure of CO2– airflow to areas of lung with better perfusion.

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14
Q

Nomenclature: little ‘a’ means what? Big ‘A’ means what? 7 key terms and meanings?

A

Arterial. Alveolar. PaCO2: arterial CO2. PACO2: Alveolar CO2. PaO2: arterial O2. PAO2: Alveolar O2. PIO2: Pressure of inspired O2. V̇A: Alveolar ventilation. V̇CO2: CO2 production.

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15
Q

What shape is an oxygen dissociation curve? What does the plateau provide?

A

Sigmoid shaped. An excellent safety factor- even significant limitation of lung function– almost normal oxygen saturation of haemoglobin.

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16
Q

Shift to right means what affinity for oxygen? Occurs when? CO has what effect on curve?

A

Low affinity. During increase in temperature and a decrease in pH.
Shifted to the left- decreases unloading of O2 into tissues.

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17
Q

How is arterial CO2 (PaCO2) calculated?

A

By dividing partial pressure of CO2 by alveolar ventilation= kVCO2/V̇A.

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18
Q

% of CO2 carried by haemoglobin? Forms what? % dissolved in plasma? % as bicarbonate?

A

23%. Carbaminohaemoglobin.
10%.
60-65%

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19
Q

What is the bicarbonate buffer reaction?

A

CO2 combines with H2O using carbonic anhydrase to form carbonic acid- this dissociates into HCO3 and H+ rapidly without enzyme assistance.

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20
Q

HCO3- moves out of RBCs for what? H+ binds to what? Released when? CO2 goes where?

A

Chloride ions via a transporter. Deoxyhaemoglobin- when passing through lungs, combines with HCO3 which forms CO2 and H2O using carbonic anhydrase.
CO2 is expired.

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21
Q

The pH of bodily fluids is regulated by what 3 main buffering systems?

A

Intracellular and extracellular buffers, the lungs eliminating CO2 and renal HCO3- reabsorption and H+ elimination.

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22
Q

What happens when someone hyperventilates? Known as what?

A

CO2 cannot be expired due to inadequate ventilation– partial pressure increases– more H+= respiratory acidosis.

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23
Q

What happens during respiratory alkalosis?

A

Hyperventilation decrease arterial partial CO2 pressure and H+ concentration.

24
Q

What equation is also used to calculate pH? If PaCO2 rises, then what needs to rise to allow this? What is 0.03?

A

Henderson-Hasselbach equation.
HCO3-.
The blood CO2 solubility co-efficient.

25
Q

What is the alveolar gas equation (alveolar oxygen)? What is ‘R’?

A

PiO2- PaCO2/ R

Respiratory quotient- ratio between amount of CO2 produced in metabolism and oxygen used.

26
Q

What is the Law of Laplace?

A

Relationship between pressure, surface tension and radius of alveolus: P= 2T/ r.

27
Q

What is lung compliance?

A

The change in lung volume caused by a given change in transpulmonary pressure; greater lung compliance, more readily lungs are expanded.

28
Q

What factors influence lung compliance? What thing helps to overcome cohesive forces between water molecules? Deep breathing does what?

A

Stretchability of lung tissues (thickening reduces it,) surface tension of air-water interfaces of the alveoli (lung expansion needs to overcome surface tension of water layer lining the alveoli.)
Surfactant produced by type II pneumocytes.
Type II pneumocytes are stretched, releasing surfactant.

29
Q

What is the inspiratory reserve volume?

A

The amount of air in excess tidal inspiration that can be inhaled with maximum effort.

30
Q

What is expiratory reserve volume?

A

Amount of air in excess tidal expiration that can be exhaled with maximum effort.

31
Q

What is the residual volume?

A

Amount of air remaining after maximum expiration. Keeps alveoli inflated between breaths- mixes with fresh air on next inspiration.

32
Q

What is vital capacity? Used to assess what?

A

Amount of air that can be exhaled with maximum effort after maximum inspiration (ERV + IRV + TV)
Pulmonary function and strength of thoracic muscles.

33
Q

What is functional residual capacity?

A

Amount of air remaining in lungs after a normal tidal expiration. (ERV + RV)

34
Q

What is inspiration capacity?

A

Maximum amount of air that can be inhaled after a normal tidal expiration. (TV+ IRV)

35
Q

What is tidal volume?

A

Amount of air inhaled or exhaled in one breath- 500ml a breath

36
Q

What is FEV1? % of vital capacity expired in 1 second? What is FEV6?

A

Forced expiratory volume in 1 second. Person takes maximal inspiration and exhales maximally as fast as possible.
80%
Forced expiratory volume in 6 seconds.

37
Q

Flow is greatest at what point? What is FEF25?

A

The start of expiration and it declines linearly with volume.
Flow at point when 25% of total volume to be exhaled has been exhaled.

38
Q

What is FVC?

A

The total amount of air forcibly expired.

39
Q

What is PEF? Measured in what?

A

Peak expiratory flow- volume expired in first 0.1 second of forced expiration.
L/min.

40
Q

Expiratory procedures only measure what and not what? What other ways are used to measure RV and TLC?

A

Vital capacity and not residual volume.

Gas dilution and body box (total body plethysmography.)

41
Q

Gas dilution is one of what 2 things? What is total body plethysmography? Volume measured (TGV) represents what?

A

Closed-circuit helium dilution/ open-circuit nitrogen washout.
Includes gas trapped in bullae.
Lung volume- RV and lung capacity can be calculated.

42
Q

A low FVC is known as what? Normal value?

A

Airway restriction.

80% or greater- above mean minus 1.645 SD.

43
Q

What is an abnormal FEV1/ FVC ratio? Known as what? What can a patient have?

A

<0.7. Airways obstruction.

Both airways restriction and obstruction.

44
Q

What is RAW? At TLC(airways expanded,) what is RAW? During expiration what happens? Opposite of RAW?

A

Airways resistance. Low.
RAW increases as airway diameter reduces.
GAW- conductance.

45
Q

Asthma causes what shape on flow/ volume curve?

A

Scalloped- decrease in peak and other values.

46
Q

How is COPD typified? What is reduced significantly? What is increased? Shape to flow/ volume curve?

A

By airways obstruction, lack of PEF variation, reduced mid expiratory flows and partial/ poor response to treatments.
FEV1 and DLCO
RAW and TLC
Low, scalloped curve.

47
Q

Typical COPD blood gas?

A

Low PaO2, high PaCO2 in type 2 respiratory failure, normal pH, elevated HCO3 if chronic acidosis.

48
Q

Typical asthma blood gas?

A

Normal PaO2, low PaCO2, normal/ high pH and normal HCO3

49
Q

In pulmonary fibrosis, what is reduced? Blood gas?

A

FEV1, FVC, TLC and DLCO

Low PaO2, low PaCO2, normal pH and low HCO3

50
Q

Control of breathing resides in neutrons in what area of the brain? What are the 2 main anatomical components? When do neurons of DRG fire?

A

Medulla oblongata
Dorsal respiratory group (DRG) and ventral respiratory group (VRG)
During inspiration

51
Q

What is located in the pre-Botzinger complex in the upper part of the VRG? Composes of what which together do what?

A

The respiratory rhythm generator (RRG.) Pacemaker cells and a complex neural network- set the basal respiratory rate

52
Q

Expiratory neurons in the VRG are most important when? Motor neurones here cause what to happen during expiration?

A

When large increases in ventilation are needed

Expiratory muscles to contract

53
Q

During quiet breathing, the RRG activates what in the VRG which causes what to happen?

A

Inspiratory neurons that depolarise inspiratory spinal motor neurons– inspiratory muscles contract.

54
Q

Medullary inspiratory neurons receive a rich synaptic input from where?

A

Neurons from various areas in the PONS.

55
Q

Which area in the lower pons is involved in the fine-tuning of the output of inspiratory neurons of the medulla? Can be overridden by what centre?

A

The apneustic centre

The pneumotaxic centre

56
Q

What does the pneumotaxic centre act to do?

A

To smooth the transition between inspiration and expiration and switches off inspiratory neurons to allow expiration.

Phase 1 Flashcards (35 decks)

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