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7 out of 11

Decreased maximum mid-expiratory flow rate indicates obstruction in: (DNB Dec 2012)

A Small airways
B Trachea

C Large airways
D Trachea & Bronchi both

Ans. A

Small airways

FEF25 – 75% (MMEFR)- Average expiratory flow rate during middle 50% of the FVC. Also called maximal mid expiratory flow rate. It is regarded as a more sensitive measure of small airway narrowing than FEV1. In spirometry. It is effort independent.

With obstructive disease only in the small airways, the only abnormality noted on routine testing of pulmonary function may be a depression in FEF 25-75% and an abnormal terminal portion of forced expiratory flow volume curve. FEV1 /FVC may be normal.

Important Point about FEV 25% - 75%

1). Values between 80 – 120% of predicted values are normal.

2). Mild obstructive (small airway) diseases have decrease FEF25 – 75% with normal FEV1/FVC.

Extra Edge:

Other investigations is respiratory diseases

1). Radionuclide scans Q Ventilation/perfusion (V/Q) scans are used to diagnose pulmonary Q embolism.

2). Computed tomography

High resolution CT (HRCT) is used to diagnose

a. Interstitial lung disease

b. Bronchiectasis.

c. Emphysema

Spiral CT pulmonary angiography is used in the diagnosis of PE. It is the investigation of choice for screening of PE. (PNQ)

Note: Previously investigation of choice for screening of PE was V/Q scan.

Pulmonary angiography is also used for confirming diagnosing of PE and pulmonary hypertension Q.

3). Fiberoptic bronchoscopy.

Diagnostic indications:

a. Suspected lung carcinoma

b. Pneumonia in the immunosuppressed

c. Slowly resolving pneumonia

d. Interstitial lung disease

Therapeutic indications:

Aspiration of mucus plugs causing lobar collapse ii. Removal of foreign bodies.

4). Bronchoalveolar lavage (BAL) is performed at the time of bronchoscopy by instilling and aspirating a known volume of warmed, buffered 0.9% saline into the distal airway.

Diagnostic indications:

a. Suspected malignancy

b. Pneumonia in immunosuppressed (especially HIV)

c. Suspected TB (if sputum negative)

d. Interstitial lung diseases (eg sarcoidosis, extrinsic allergic alveolitis, histiocytosis)

Therapeutic indications: alveolar proteinosis.


1). Hypoxia (give supplemental O2)

2). Transient CXR shadow

3). Transient fever

4). Infection (rare).

Respiratory Flashcard List

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