Clinical features of ILD
 Symptoms :
Shortness of breath with exertion
Non-productive cough
Decreased exercise tolerance
Fatigue
Loss of appetite
Weight loss
 Physical examination :
Bibasilar fine inspiratory crackles
Clubbing – common in Idiopathic pulmonary fibrosis (IPF)
Central cyanosis
Complications
Respiratory failure
• Type I respiratory failure occurs because of damage to lung tissue. This lung
damage prevents adequate oxygenation of the blood (hypoxemia);
however, the remaining normal lung is still sufficient to excrete the carbon
dioxide being produced by tissue metabolism.
• Type II respiratory failure is also known as ‘ventilatory failure’. It occurs
when alveolar ventilation is insufficient to excrete the carbon dioxide being
produced. Inadequate ventilation is due to reduced ventilatory effort, or
inability to overcome increased resistance to ventilation – it affects the
lung as a whole, and thus carbon dioxide accumulates. This is ultimately
fatal unless treated.
Complications of ild
• Respiratory failure
• Impairment in gas exchange
• In ILD patients, the gas exchange between the alveoli and capillaries can be impaired if the
prognosis is poor or left untreated. Alteration of ventilation-perfusion ratio (V/Q) and the
diffusion capacity causes an increase in alveolar-arterial oxygen gradient.
• The alterations cause an increase in respiratory rate (RR) as a compensatory mechanism, with
higher than normal minute ventilation, with hypercapnia developing only in the late disease
stages.
• The lung compliance is reduced in ILD patients due to increased lung elastic recoil related to the
extracellular matrix deposition. The reduction in lung compliance causes an increase in
respiratory rate due to the overloading of respiratory muscles that stimulates peripheral
mechanoreceptors. This breathing pattern aims to minimize the work of breathing; however, in
the late stages of the disease and when exercise intensity increases, tidal volume accounts for a
greater proportion of the diminished vital capacity and physiological dead space increases leading
to increased respiratory drive and possible development of hypercapnia.
Complications
Pulmonary hypertension and cor pulmonale
• As you can see in the diagram on the right. Epithelial injury with subsequent production
of different mediators is the hallmark of fibrosis induction. These mediators induce
fibroblast activation with extracellular matrix (ECM) deposition, which leads to fibrosis.
Some of these mediators (e.g., TGF-β) also activate endothelial cells and, as a result of a
shift in favor of increased angiostatic (PEDF mediator) and reduced angiogenic factors
(VEGF). This results in the apoptosis of epithelial cells. Apoptotic epithelial cells produce
less vasodilators, but more vasoconstrictors, which eventually leads to vasoconstriction
of smooth muscle cells.
• At the same time, apoptosis of endothelial cell will lead to endothelial cell proliferation,
which is important for remodeling of mesenchymal cells in the PA wall. Pulmonary artery
remodeling with fibrosis and lesion formation causes thickening and narrowing of the
pulmonary arterial wall. All these events leads to pulmonary hypertension.
• Pulmonary hypertension causes increased cardiac workload. Right ventricular
hypertrophy develops and lead to cor pulmonale.
• This is the diagram summarizes the complications of interstitial lung
disease and the mechanisms involved in it. Interstitial lung disease
will cause vascular obliteration and pulmonary vasocontriction due to
the thickening of interstitium and scarring which leads to increased
physiologic dead space.
• On the other hand, pulmonary vasoconstriction, vascular obliteration
and reduced lung volume causes increase in pulmonary vascular
resistance leading to pulmonary hypertension. Pulmonary
hypertension will eventually cause right ventricular failure causing
reduced cardiac output.
• Due to impaired tissue oxygenation, lactic acidosis develops and
mixed venous hypoxemia will lead to hypoxemia and increased work
of breathing. All these will eventually lead to respiratory failure and
patient presents with dyspnea, fatigue, poor prognosis and reduced
exercise tolerance.