12. Interstitial Lung Disease

Question 1

what are the major categories of Interstitial Lung disease?

Answer 1

• Idiopathic Pulm Fibrosis
• due to Occupational/Environmental inhalants
• Drug-related
• Sarcoidosis
• Circulatory
• Assoc’d with connective tissue disorders
• Radation-based

Question 2

symptoms of ILD?

Answer 2

dyspnea, cough

Question 3

physical findings with ILD?

Answer 3

fine crackles, clubbing, findings related to underlying disease process

Question 4

Effects of ILD on lung function: compliance?

Answer 4

decreased due to inflammation and/or deposition of collagen. altered pressure/volume relationship in lungs in ILD

Question 5

Effects of ILD on lung function: diffusion?

Answer 5

impaired. due to incr thickness of the interface. thickened by interstitial inflammation, and/or deposition of collagen.

Question 6

Effects of ILD on lung function: V/Q?

Answer 6

mismatch. ILD impacts the lungs unequally/heterogeneous.

Question 7

what happens to the lung areas that are less compliant than others?

Answer 7

receive less ventilation than normal areas (remember compliance = dV/dP, so if you apply the same pressure to a less compliant area, it will receive less volume/less ventilation)

Question 8

most patients with ILD have a restrictive or obstructive pattern?

Answer 8

restrictive

Question 9

Lung volume in ILD: incr or decr?

Answer 9

decr.

Question 10

flow rates in ILD?

Answer 10

decr, but increased relative to lung volume. flow rates vary as a function of elastic recoil. since elastic recoil is increased, flow rate is increased.

Question 11

ILD: DLCO?

Answer 11

lower due to diffusion impairment

Question 12

what is idiopathic pulmonary fibrosis?

Answer 12

fibrosing disease of unknown etiology, generally seen in elderly.

Question 13

what is the pathologic finding in IPF?

Answer 13

UIP: usual interstitial pneumonia.

Question 14

what is the sequence of events in IPF?

Answer 14

stimulus (known or unknown) –> alveolitis (accumul of inflam cells in interstitium)–> derangement of alveolar-capillary units (interstitial edema) –> loss of alveolar-capillary units for gas exchange (ie fibrosis)

Question 15

does IPF require inflammation

Answer 15

no, can occur independently of inflammation.

Question 16

what is the established therapy for IPF?

Answer 16

there is none: used to be anti-inflammatories, but those barely worked. (note this is only IPF, not all ILD)

Question 17

what is the mean survival time for IPF?

Answer 17

3yrs from dx

Question 18

what are the occupational/environmental inhalants that contribute to ILD?

Answer 18

• dusts (silica/asbestos)
• moldy hay (Farmer’s Lung)
• gases/fumes/vapors/aerosols

Question 19

what drugs may cause ILD?

Answer 19

cancer drugs (methotrexate)
antibiotics

Question 20

what is sarcoidosis?

Answer 20

multi-system disorder characterized by granulomatous inflammation. thorax is most common site of involvement.

Question 21

why are patients with ILD dyspneic?

Answer 21

• inc work of breathing (lower compliance, more dead space)

- stimulation of vagal fibers

Question 22

why do patients with ILD have cough?

Answer 22

Interstitial inflammation may stimulate vagal fibers

Question 23

why is there decr compliance in ILD?

Answer 23

deposition of collagen –> decr compliance

Question 24

what are the lung volumes in ILD: TLC, FRC, RV, VC

Answer 24

Everything is reduced!

• TLC reduced: stuff lungs. Makes it harder to inflate, resp muscles have to work harder
• FRC detd by recoil v. chest wall.
• Decr RV: because of incr recoil, minimizes air trapping
• Decr VC

Question 25

why is there an incr FEV1/FVC ratio in ILD?

Answer 25

increased recoil. subranormal flow rates for volume

Question 26

in ILD, what is the change to patency of small airways?

Answer 26

due to fibrosis, tends to keep more airways patent at smaller volumes/pressures. contrast with emphysema which has collapse.

Question 27

what is the pattern for C02 removal with ILD?

Answer 27

pts tend to be hypocapnic. | Increase in ventilation offsets the increase in physiological dead space

Question 28

what PFT patterns might make you think of ILD?

Answer 28

low diffusing capacity, high ratio

Question 29

why would an ILD patient take quick shallow breaths?

Answer 29

to minimize discomfort.

Question 30

Structure/function relationship summary

Answer 30

``` Decreased compliance Restriction of the lung Decreased diffusing capacity Hypoxia that worsens with exercise Increased VD/VT ```

Question 31

what does IPF look like on radiology?

Answer 31

honeycombing

Question 32

ILD: if not inflammation, what is the problem?

Answer 32

possibly a genetic predisposition to profibrotic cytokines/growth factors that cause fibrosis.

Question 33

what is erythema nodosum, and in what condition do we see it?

Answer 33

sarcoidosis

Question 34

what is adenolathy? when do we see it?

Answer 34

lymph node swelling. see in sarcoidosis

Question 35

Drug induced ILD: what are the most common drugs involved?

Answer 35

``` Large number of agents Most common: Cancer chemotherapy (bleomycin, carmustine) Amiodarone (anti-arrythmic) Nitrofurantoin (abx) ```

Question 36

How does Bleomycin factor into ILD?

Answer 36

``` Occasional cause of ILD Important model of lung injury Role of TGF-β, TNF-α Mechanism: oxidant injury Occurrence modified by: Oxygen Radiation ```