Lung functions in Emphysema reveal all of the following, Except? (LQ)
|A||Decreased vital capacity|
|B||Increased diffusion capacity for carbon monoxide (DLCO)|
|C||Increased Total Lung capacity|
|D||Decreased FEV1 / FVC ratio|
Increased diffusion capacity for carbon monoxide (DLCO)
Definition: It is defined histologically Q as enlarged air spaces distal to terminal bronchioles, with destruction of the alveolar walls.
Pathology– Permanent and destructive enlargement of airspaces distal to the terminal bronchioles without obvious fibrosis and with loss of normal architecture. 3 types
1). Centriacinar – Central or proximal part of respiratory unit – acinus upper lobe involvement. Commonly seen in male smokers (MCQ).
2). Panacinar – Uniform destruction of acinus. Lower zone involvement. It is associated with α1 – AT deficiency (MCQ).
3). Paraseptal – Involvement of distal acinus. It is found near the pleura and often causes pneumothorax.
Compensatory emphysema – Normal lung tissue undergoes hyperinflation as a compensatory mechanism in response to the damage occurring in part of the same lung or opposite lung.
Alveolar septa are preserved. In emphysema ↓VC, ↓DLCO, ↑TLC, ↓FEV1, ↓FVC.
Pink puffers (Emphysema) and blue bloaters (Chronic bronchitis) (Two Ends of a spectrum)
1). Pink puffers have increase alveolar ventilation, a near normal PaO2 and a normal or low PaCO2).
2). They are breathless but are not cyanosed.
3). They may progress to type 1 respiratory failure.
For chronic bronchitis.
1). They are cyanosed Q,
2). Blue bloaters have reduced alveolar ventilation, with a low PaO2 and a high PaCO2. (Type II respiratory failure)
3). Their respiratory centres are relatively insensitive to CO2.
4). They rely on hypoxic drive to maintain respiratory effort so supplemental oxygen should be given with care so always give low flow oxygen.
Important Points: Both Chronic bronchitis and emphysema patient may go on to develop cor pulmonale Q.
There are two types of emphysema that cause clinically significant airflow obstruction:
Acini are uniformly involved from level of respiratory bronchiole to terminal blind alveoli
Central or proximal parts of acini formed by respiratory bronchioles are affected whereas distal alveoli are spared
Lesions are more common in lower zone and bases
Lesions are more severe and common in upper lobes
Occurs in association with α1 antitrypsin deficiency
Occurs predominantly in smokers is the commonest pattern.