Restrictive Lung Disease

Question 1

describe intrinsic lung disease

Answer 1

disease of the lung itself;

interstitial - restricts normal lung function (impaired gas exchange), the interstitial lung diseases (ILDs) vary in degrees of inflammation and/or fibrotic scar tissue

alveolar - inflammation (ILDs) (oedema, haemorrhage (vasculitides), infection)

Question 2

describe diagnosing ILDs

Answer 2

occupational, hobbies, smoking, drugs
blood tests 
CT patterns of disease
MDTs 
lung biopsy

Question 3

describe different interstitial lung diseases

Answer 3

refer to PP

Question 4

describe features of restrictive lung disease

Answer 4

restrictive pattern on pulmonary function test (normal shape, normal peak flow, reduced volume);
decreased forced vital capacity
FEV1/FVC>70
decreased DLCO (>80% predicted)

Question 5

describe pathophysiology of intrinsic lung disease

Answer 5

disease of alveolar structures (walls/lumen)
impaired alveolar gas exchange - alveolar barrier to oxygen exchange, alveolar-arteriolar barrier (A-a gradient)
carbon dioxide exchange unimpaired - alveolar ventilation normal, carbon dioxide very soluble and blown off 
decreased PaO2 (decreased sats), normal PaCO2

Question 6

describe the diffusion capacity of carbon monoxide (DLCO)

Answer 6

measures gas diffusion across alveolar-arteriolar barrier
CO diffusion across alveolar-capillary barrier - aka single breath diffusing capacity
DLCO - total lung transfer for CO (or diffusing capacity) - corrected for alveolar volume (KCO)
decreased DLCO - anaemia, emphysema, ILDs, pulmonary oedema, PE
to monitor treatment response in ILD - more sensitive than FVC

Question 7

describe extrinsic lung disease

Answer 7

thoracic/extra-thoracic - obesity, kyphosis, ascites, diaphragmatic palsy
neuro-muscular disorders - motor neuron disease or myasthenia gravis
pleural disease - diffuse pleural thickening, mesothelioma, large pleural effusions

Question 8

describe pathophysiology of restrictive hypoventilation

Answer 8

hypoventilation means impaired alveolar ventilation which means a rise in PaCO2 and reduced PaO2
obesity/kyphoscoliosis reduces chest wall compliance
neuromuscular conditions reduced power of msucles involved in respiration
refer to PP

Question 9

describe clinical presentation of restrictive lung disease

Answer 9

progressive shortness of breath +/- dry cough
full detailed history including drugs, smoking and occupational (asbestos) and hobbies history
pre-existing neuromuscular disorder?
CO2 retaining symptoms - headache, confusion and lethargy

clinical examination;
finger clubbing
obese - kyphosis, scoliosis
fibrotic crepitations
clinical signs of pleural effusions or ascites
cyanosis
CO2 retention - flushed skin, bounding pulse, rapid breathing, premature heart beats, muscle twitches, flapping tremor

Question 10

describe investigations of restrictive lung disease

Answer 10

PFTs - restrictive pattern;
decreased FVC with FEV1/FVC >70
decreased DLCO (<80% predicted)

arterial oxygen desaturation (decreased PaO2, decreased sats) at rest or exercise

arterial blood gases;
Type 1 resp failure - PaO2<8kPa
Type II resp failure - hypoxia with hypercapnia, pCO2>6kPa
increase in bicarbonate –> chronic hypercapnia

CXR

CT

pleural ultrasound - decreased diaphragmatic excursion, large effusions

abdominal ultrasound - ascites

bloods - connective tissue screen, vasculitis scree (ANCAs with MPO/PR3 Abs), eosinophilia, secondary polycythaemia from chronic hypoxaemia

Question 11

describe treatment of restrictive lung disease

Answer 11

lifestyle;
weight loss - diet and exercise
pulmonary rehabilitation programmes

removal of trigger factors - dust drug (methotrexate, amidarone, nitrofurantoin), anitgen

medical therapy;
drugs to influence disease process -
anti-inflammatory/immunosuppressive drugs (steroids and/or azathioprine)
antifibrotic drugs (pirfenidone or nintedanib)
treat neuromuscular disease (pyridostigmine in MG)

procedures - intercostal drainage or ascitic drainage

surgery;
corrective spinal surgery (scoliosis)
decortication for chronic empyema 
diaphragmatic plication (diaphragmatic paralysis)
lung transplant (pulmonary fibrosis)

supportive;
CPAP - obstructive sleep apnoea syndrome with obesity hypoventilation
non-invasive ventilation (NIV) - ventilatory support (neuromuscular weakness, kyphoscoliosis)
oxygen - correct significant hypoxaemia, !caution, oxygen sensitvity in CO2 retainers!