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Hugh's MD1 Respiratory > Lou's Pathophysiology > Flashcards

Lou's Pathophysiology Flashcards

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1
Q

Does ventilatory capacity limit healthy people during exercise?

A

No, HR does

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1
Q

What are the mechanical changes that occur due to pulmonary oedema?

A

Decrease lung compliance - fluid makes the increases the elastic work of breathing

Decrease lung volume - lungs are harder to expand

Increased airway resistance - due to fluid in the airways

Increased work of breathing (elastic and resistive)

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1
Q

What is the clinical presentation of abestosis?

A

Progressive breathlessness and cough

Crepitations (the type due to opening of alveolar during inspiration)

Clubbing

+/- Cyanosis

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2
Q

Why is systolic BP lower during inspiration

A

Negative interthoracic pressure > expands the compliance of pulmonary vasculature > blood pools there > reduces pulmonary return > SV is lower > BP is lower (the body response by increase HR).

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2
Q

What are some causes of increase pulmonary hydrostatic pressure?

A

Left ventricular failure,

mitral stenosis

fluid overload

pulmonary veno-occlusive disease

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2
Q

What causes pulmonary hypertension?

A
  1. Increase LA pressure - eg mitral stenosis, left heart failure
  2. Increased pulmonary blood flow - eg excess central volume
  3. Increased pulmonary vascular resistance - eg vasocontriction,

vasculature damage (emphysema), obstruction (PE)

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3
Q

What are 5 causes of hypoventilation?

A

Motor centre depression

Neuromuscular disease

Chest wall deformities

Obesity

Sleeping disordered breathing

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3
Q

What is MUD?

A

Medically undiagnosed dyspnoea

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4
Q

Why does obstruction occur during sleep?

A
  1. Muscles relax
  2. Airway is already narrowed (obesity, tonsils)
  3. Tongue falls back (esp if suprine)
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5
Q

What happens to residual volume with gas trapping?

A

It increases

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6
Q

Why is a low V/Q match bad?

A

Hb arrives at alveolar-capillary but isn’t filled with O2 > reduces PaO2 > hypoxaemia

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7
Q

What levels of PaCO2 occur during respiratory failure?

A

>60mmHg

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7
Q

How thick is the A-C membrane?

A

0.5 microns

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8
Q

When does diffusion limitation of CO2 occur?

A

Only if there is very severe diffusion impairment, inadequate ventilation is the primary cause

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8
Q

Generally, conditions that effect the alveolar membrane make the lungs …

A

Stiffer - increasing the elastic work of breathing

Except in Emphysema

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10
Q

How does metabolic acidiosis occurs due to pulmonary oedema?

A

Pulmonary oedema (=low gas exchange) therefore tissue hypoxia - anaerobic resp. - lactic acid - metabolic acidosis.

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11
Q

What physiological differences are present when breathing with an obstruction?

A

Active exhalation

Slower inhalation and exhalation

Reduction in maximum ventilation

Increased work of breathing/use of respiratory muscles

Increased sensation of breathing

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11
Q

What does anxiety do to the respiratory equilibrium?

A

Anxiety > hyperventilation > PaCO2 drop > pH Increases = Respiratory alkalosis

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12
Q

What diseases can disrupt the A-C membrane?

A

Infections - TB, pneumonia

Pneumonitis (inflammation of the alveoli) eg drug induced

Pulmonary fibrosis

Emphysema

Oedema

Lymphangitis

Carcinomatosis

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12
Q

What happens to maximum ventilation in restrictive lung disease?

A

It decreases

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13
Q

What is type I respiratory failure characterized by?

A

Low PaO2

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14
Q

What is type II respiratory failure characterised by?

A

PaCO2 >50mmHg and PaO2 low to normal

due to failure of ventilation

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15
Q

What is the normal lymphatic flow rate in the lung?

A

20ml/hour

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16
Q

What factors determine the compliance of the lungs?

A

Tissue composition

Surfactant

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17
True or false, ventilation rate is higher dependent of PaO2?
False, PaO2 must drop below 60 before there is a response
18
What are the gas exchange changes that occur due to pulmonary oedema?
hypoxaemia due to shunt Low V/Q units Diffusion impairment
18
What makes up the alveolar-capillary membrane?
Layer of surfactant Type I alveolar cell Basement membrane Endothelial cell
19
What is breathlessness?
## Footnote Breathlessness arises when there is a recognition by the subject of an inappropriate relationship between respiratory work and total body work
21
What is a negative consequence of the vasocontrictory compensation of V/Q mismatch?
Increases pulmonary pressure if V/Q mismatch is wide spread
23
Which occurs more readily interstitial or alveolar oedema?
Interstitial as capillary endothelium is more permeable to water cf to alveolar wall (and water enters the interstitium first)
25
Does the pulmonary arterial pressure increase during exercise?
No, due to dilation and recruitment of extra pulmonary vessels
27
What is acute respiratory failure defined as?
The failure of the respiratory system to provide adequent ventilation, oxygenation or metabolic requirements of the patient
28
What is the problem with giving O2 to people with chronic hypercapnoea?
Their resp centre responds to PaO2 so if it is increased too much that can stimulate hypoventilation \> further hypercapnoea
30
What is the normal range of A-a gradients?
15-30
31
What are the consequences of obstructive lung disease?
Recruitment of accessory muscles Increase consumption of O2 by respiratory muscles Possible fatigue of respiratory muscles
33
What is the A-a gradient a measure of?
Alveolar/capillary gas exchange across all A-C units
34
What are the mechanical effects of restrictive lung disease?
Breathlessness Increase elastic work of breathing Reduced lung volume Shorter, faster breaths Reduced maximum volume - Increase use of inspiratory muscle and O2 comsuption by them
35
What are the pulmonary artery pressures during systole and diastole
25/8, mean=15mmHg
36
What occurs during sleep apnoea?
Fall asleep \> Muscle relaxation \> Complete Obstruction \> Fall in PaO2 and increase in PaCO2 \> Brains wakes \> Muscle contract, airway re-opens \> Fall into deep sleep again
37
What is lung compliance?
Change in V / Change in P
37
What is the consequence of chronic sleep disorders?
Physiological change occurs to facilitate sleep \> Re-set the resp centre to be able to tolerate a higher PaCO2 so that sleeping can occur \> chronic hypercapnoea \> PaO2 becomes the driver for ventilation
39
What are the possible causes of high PaCO2
Predominately low ventilation
39
What are some symptoms of sleep apnoea?
Snoring Arousals Choking Excessive daytime sleeping, lTethargy, reduced libido, mood change, poor memory Difficult to treat hypertension and unexplain resp failure
40
What is gas trapping?
The obstruction of exhalation of gas due to a severe obstruction. Air is inhaled but can't be exhaled
41
What is Fick's law?
Determines the rate of diffusion of a gas
42
What is pulsus paradoxus?
When the difference in systolic BP between inspiration and expiration is greater.
43
What is the equation for A-a gradient?
PAO2 = PiO2 - PACO2/RQ followed up PAO2 - PaO2 Where RQ is a constant = 0.8 PiO2 (partial pressure of inspired air) for room temp and sea level = 150 PACO2 is assumed to equal PaCO2 which is measured in arterial blood gas And PaO2 is also measured in arterial blood gases
45
What happens to perfusion if ventilation drops in a local area?
Compensatory drop due to divertion of blood flow in capillaries
46
What are some management strategies for sleep apnoea?
Nasal CPAP (continue positive airway pressure) Manibular advancement splint Surgery Lie on side
48
What percentage of FVC (forced vital capacity) is expelled in a normal FEV1
80%
49
What some possible causes of MUD?
Psychologenic Deconditioned (got fat) New clinical disease Maximal effort
50
What causes wheezing?
Airway obstruction
51
When does diffusion limitation of O2 occur?
In heathly people: Never People with mild diffusion impairment: during exercise People with a severe diffusion impairment: at rest and during exercise
52
What percentage of total O2 usage is required for the WOB at rest?
3%
53
Which has a greater impact on lung mechanic and gas exchange, fluid in the alveoli or interstitial space?
Alveoli!
54
What is the mechanism of asbestosis?
Chronic inflammation \> progressive fibrosis \> disruption and destruction to A-C membrane \> Mechanical and gas exchange defect = Decrease PaO2, Increase A-a gradient, Reduced lung volume, reduced compliance, Increased work of breathing
56
When is breathlessnees a symptom not a sensation?
When it occurs when it shouldn't normally, when it doesn't usually occur for that level of exertion.
57
What does surfactant do?
It lower surface tension in alveoli to prevent them from collapsing, increases the compliance of the lung and keeps the alveoli dry.
58
The respiratory centre sends the majority of its output via which nerve?
Phrenic
60
What are the possible causes of low PaO2?
Low PiO2 Low Ventilation Gas exchange abnormality - V/Q mismatch, shunt, A-C membrane problem
61
What type of lung disease is asbestosis?
Restrictive
62
What is the consequence of high V/Q mismatch?
Physiological dead space with little effect on PaO2
63
Where in the brain is the respiratory centre located?
The pons and medulla
64
How does airway obstruction increase the WOB?
It increases the resistive WOB, ie the work required to overcome the friction of airflow. (As opposed to an increase elastic work of breathing that occurs with restrictive lung disease)
65
What are some causes of increase pulmonary capillary permeability?
Toxins, sepsis, multiple trauma
66
What happens to total lung capacity with gas trapping?
It increases

Hugh's MD1 Respiratory (15 decks)

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