Ventilation

Diffusion

HB 95%+- 2 normal Pa02 10-12KPa. 90% 8Kpa.

Restrictive Vs Obstructive

Minute ventilation = TV x RR

Alveolar = TV - dead space x RR

"Exhange of air between lungs and atmosphere"

Compliance: Lung and chest wall, Change in pressure required to change volume.

Ventilatory Capacity: Max spontaneous ventilation that can be maintained without muscle fatigue.

Ventilatory Demand: Minute ventilation red'q to maintain paCO2

Perfusion

Fick's Law: Rate of gas transfer through sheet of tissue ∝ Tissue area and difference in gasPa between the sides, and is I∝ tissue thickness.

CO2 diffuses 20x faster than O2.

Max at lung base, upright

Low ventilation, normal perfusion = Deoxygenated blood

Matched to ventilation

Normal ventilation, low perfusion= ^ dead space (wasted)

Poiseuille's Law: Laminar flow. Resistance ∝ 1/r

Investigation: TLCO/DLCO (diffusing capacity): Transfer factor. Breath in CO during breath hold, measure uptake. Reflects absorption ∝ thickness of alveolar membrane.

Obstructive

Restrictive

Reduced FEV, preserved FVC. <70%** FEV1/FVC**

Gas trapping, expansion, ^RV

COPD, asthma, bronchiectasis

IPL, Abnormality, Neuromuscular

fibrosis of alveoli, small lungs and reduced compliance

FEV1 + FVC reduced, therefore <70% FEV1/FVC = normal or higher

Diffusion is normal

Problem with diffusion-

IPL

interstitial thickening

Normal perfusion

Impaired diffusion

71 years presentation. 2M:1F

Managed: Antifibrotics: Pirfenidone, nintedanib

Support: O2, rehab, breathlessness techniques (fan, opiates), transplant?

Measured: CT Pul angiogram; PE. Echocardiogram: intra-cardiac shunts- AVM