in which part of the lung would there be Low PaO₂ and higher PaCO₂
lung base
in which part of the lung would there be higher PaO₂ and low PaCO₂
apex
which area of the lung has a low V/Q?
base
give some examples of V/Q mismatch
Pulmonary embolism
= high V/Q (dead space)
Pneumonia,
pulmonary oedema
= low V/Q (shunt effect)
what is the main driver of respiration in healthy individuals?
chemo receptors in medulla respond to ↑ CO₂ (via pH in CSF)
what is the main driver of respiration in individuals with Copd?
chronic hypercapnia
chemoreceptors become desensitised
Hypoxic drive predominates
what is the hypoxic drive?
A mechanism where the body regulates breathing based on low oxygen levels in the blood, rather than high carbon dioxide levels
when is an obstructive pattern seen?
asthma,
COPD,
bronchiectasis
what is the obstructive pattern?
↓ FEV1
↓ FEV1/FVC ratio (<0.7)
↑ TLC, ↑ RV (due to air trapping)
when is an restrictive pattern seen?
- interstitial lung disease (ILD),
- severe kyphoscoliosis,
- neuromuscular disorders,
- obesity
what is the restrictive picture?
- ↓ TLC
- Normal or ↑ FEV1/FVC ratio
what is DLCO?
Diffusing Capacity for Carbon Monoxide
Give 4 examples of reduced TLCO:
- Interstitial lung disease
- Emphysema (alveolar destruction)
- Pulmonary embolism (reduced perfusion)
- Anaemia (reduced haemoglobin)
Give 3 examples of increased TLCO:
- Asthma (increased pulmonary blood volume)
- Polycythaemia (increased Hb)
- Pulmonary haemorrhage
how does the body adapt to altitude?
initially respiratory alkalosis,
then renal bicarb exretion -> right shift of curve -> increased RBc production
how does one distinguish between asthma and emphysema using DLCO?
Asthma = raised
Patient has normal / high range FEV1/FVC + low TLCO .. what type of picture is this?
- restrictive
what happens to PaCO2 at altitude?
Drops due to hypoventiallation
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lung physiology18
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obstructive airway disease16
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respiratory infections37
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Interstitial and Granulomatous Lung Diseases21
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Pulmonary Vascular and Vasculitic Lung Disease11
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Pleural and Chest Wall Disorders16
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chest wall disease17
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Sleep and Neuromuscular Respiratory Disorders13
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respiratory neoplasms15
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critical illness13
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fibrotic lung disease8
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lung cancer16
