12. Interstitial Lung Disease Flashcards
what are the major categories of Interstitial Lung disease?
- Idiopathic Pulm Fibrosis
- due to Occupational/Environmental inhalants
- Drug-related
- Sarcoidosis
- Circulatory
- Assoc’d with connective tissue disorders
- Radation-based
symptoms of ILD?
dyspnea, cough
physical findings with ILD?
fine crackles, clubbing, findings related to underlying disease process
Effects of ILD on lung function: compliance?
decreased due to inflammation and/or deposition of collagen. altered pressure/volume relationship in lungs in ILD
Effects of ILD on lung function: diffusion?
impaired. due to incr thickness of the interface. thickened by interstitial inflammation, and/or deposition of collagen.
Effects of ILD on lung function: V/Q?
mismatch. ILD impacts the lungs unequally/heterogeneous.
what happens to the lung areas that are less compliant than others?
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)
most patients with ILD have a restrictive or obstructive pattern?
restrictive
Lung volume in ILD: incr or decr?
decr.
flow rates in ILD?
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.
ILD: DLCO?
lower due to diffusion impairment
what is idiopathic pulmonary fibrosis?
fibrosing disease of unknown etiology, generally seen in elderly.
what is the pathologic finding in IPF?
UIP: usual interstitial pneumonia.
what is the sequence of events in IPF?
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)
does IPF require inflammation
no, can occur independently of inflammation.
what is the established therapy for IPF?
there is none: used to be anti-inflammatories, but those barely worked. (note this is only IPF, not all ILD)
what is the mean survival time for IPF?
3yrs from dx
what are the occupational/environmental inhalants that contribute to ILD?
- dusts (silica/asbestos)
- moldy hay (Farmer’s Lung)
- gases/fumes/vapors/aerosols
what drugs may cause ILD?
cancer drugs (methotrexate) antibiotics
what is sarcoidosis?
multi-system disorder characterized by granulomatous inflammation. thorax is most common site of involvement.
why are patients with ILD dyspneic?
- inc work of breathing (lower compliance, more dead space)
- stimulation of vagal fibers
why do patients with ILD have cough?
Interstitial inflammation may stimulate vagal fibers
why is there decr compliance in ILD?
deposition of collagen –> decr compliance
what are the lung volumes in ILD: TLC, FRC, RV, VC
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
why is there an incr FEV1/FVC ratio in ILD?
increased recoil. subranormal flow rates for volume
in ILD, what is the change to patency of small airways?
due to fibrosis, tends to keep more airways patent at smaller volumes/pressures. contrast with emphysema which has collapse.
what is the pattern for C02 removal with ILD?
pts tend to be hypocapnic.
Increase in ventilation offsets the increase in physiological dead space
what PFT patterns might make you think of ILD?
low diffusing capacity, high ratio
why would an ILD patient take quick shallow breaths?
to minimize discomfort.
Structure/function relationship summary
Decreased compliance Restriction of the lung Decreased diffusing capacity Hypoxia that worsens with exercise Increased VD/VT
what does IPF look like on radiology?
honeycombing
ILD: if not inflammation, what is the problem?
possibly a genetic predisposition to profibrotic cytokines/growth factors that cause fibrosis.
what is erythema nodosum, and in what condition do we see it?
sarcoidosis
what is adenolathy? when do we see it?
lymph node swelling. see in sarcoidosis
Drug induced ILD: what are the most common drugs involved?
Large number of agents Most common: Cancer chemotherapy (bleomycin, carmustine) Amiodarone (anti-arrythmic) Nitrofurantoin (abx)
How does Bleomycin factor into ILD?
Occasional cause of ILD Important model of lung injury Role of TGF-β, TNF-α Mechanism: oxidant injury Occurrence modified by: Oxygen Radiation
