CXR Interpretation and Spirometry

Question 1

What is spirometry?

Answer 1

An objective and reproducible measurement of lung function. It measures the volume of air that the patient can forcibly expel from their lungs after a maximal inspiration, and how quickly the air can be expelled. It is used to aid diagnosis, detect and quantify the degree of airway obstruction/restriction, assess reversibility of airway obstruction post bronchodilator, and monitor effects of treatment

Question 2

What is FEV1?

Answer 2

Forced expiratory volume in 1 second. After a full inspiration, the volume of air expired in the first second of forced expiration

Question 3

What is FVC?

Answer 3

Forced vital capacity. After a full inspiration, the maximum volume of air that can be forcibly expired in one breath

Question 4

How do you interpret spirometry results?

Answer 4

1. Look at the FEV1/FVC ratio (it should be approx 80%, abnormal is less than 70%)
2. Look at the FVC and work out the % of predicted normal (i.e. FVC measured/FVC predicted)
3. Look at FEV1 and work out the % of predicted normal (i.e. FEV1 measured/FEV1 predicted)

Question 5

What do NORMAL spirometry patterns look like?

Answer 5

FEV1/FVC > 70% (0.7) – average is approx 80%
FVC > 80% of predicted
FEV1 > 80% of predicted

Question 6

What do OBSTRUCTED spirometry patterns look like?

Answer 6

Reduced FEV1/FVC ratio (<70%)
Decreased FEV1 (<80% of predicted)
FVC normal or reduced but to a lesser degree. The % of predicted FEV1 indicates whether the obstruction is mild, moderate, severe or very severe (gold classification)

Question 7

Define the gold classification of obstructions

Answer 7

Mild: FEV1 > 80% predicted
Moderate: 50%<FEV1<80% predicted
Severe: 30%<FEV1<50%
Very severe: FEV1 <30% predicted

Question 8

What do RESTRICTED spirometry patterns look like?

Answer 8

Increased or normal FEV1/FVC ratio
Decreased FVC (<80% of predicted)
Decreased FEV1 (proportional to decreased FVC) or normal

Question 9

What do MIXED spirometry patterns look like?

Answer 9

Reduced FEV1/FVC (<70% shows obstruction)
Reduced FVC (<80% of predicted shows restriction)
Reduced FEV1 (<80% of predicted shows severity of the obstruction)

Question 10

What is a chest X-ray?

Answer 10

A CXR is a 2D representation of a 3D object – height and width are maintained but depth is lost

Question 11

How do we interpret a CXR?

Answer 11

1. Pt & film details: labels (name, date, MRN), orientation, projection (PA/AP)
2. Film quality: exposure, inspiratory effort, pt position
3. Extrathoracic/thoracic: soft tissues, thoracic cage (bones)
4. Intrathoracic: mediastinum (trachea, hila, heart), diaphragms (shape, angles, position), lung fields (boundaries, markings, fissures, zones)
5. Lines & attachments: drips, drains, tubes, foreign bodies

Question 12

Where are the zones of the lungs?

Answer 12

Upper zone: above 2nd anterior rib
Middle zone: btw 2nd and 4th anterior ribs
Lower zone: below 4th anterior rib

Question 13

Abnormal CXRs: consolidation

Answer 13

Consolidation is fluid filled alveoli, often associated with pneumonia. Signs: patchy opacity, air bronchograms, silhouette sign

Question 14

Abnormal CXRs: air bronchogram

Answer 14

A tubular outline of an airway (darker) made visible by filling of surrounding alveoli by fluid (opaque)

Question 15

Abnormal CXRs: silhouette sign

Answer 15

Loss of the clear outline of a border of thoracic structure (e.g. heart, diaphragm). This is because the lung appears opaque where air has been replaced – can help localise which lobe is affected

Question 16

Abnormal CXRs: collapse (atelectasis)

Answer 16

The loss of aeration to the alveoli. Signs on CXR by increased opacity in collapsed area, loss of lung volume with shift structures towards the area of collapse (if the collapse is large enough), can also get silhouette sign

Question 17

Abnormal CXRs: pleural effusion

Answer 17

Is fluid in the pleural space. Signs include increased opacity, blunting of the costophrenic angle, and a meniscus/fluid line

Question 18

Abnormal CXRs: pneumothorax

Answer 18

Is air in the pleural cavity. Signs include visible pleural margin/edge, lack of lung markings & increased translucency, shift of structures away in large PTx, collapsed (deflated) lung can appear more opaque

Question 19

Abnormal CXRs: tension pneumothorax

Answer 19

Occurs when the opening that allows air to enter the pleural space functions as a one-way valve, allowing more air to enter but none to escape - medical emergency!!

Question 20

Abnormal CXRs: emphysea

Answer 20

Is a condition in which the alveoli are damaged and enlarged, with destruction of the pulmonary capillary bed. Signs include increased transluceny, decreased lung markings, hyperinflation (low flat diaphragms, horizontal ribs, elongated heart)

Question 21

Abnormal CXRs: pulmonary oedema

Answer 21

Is fluid in the extra-vascular spaces of the lungs. Signs include bilateral patchy opacity (+/- air bronchograms), enlarged hila regions with ‘bat wings’ pattern, ‘cotton wool’, ‘fluffy’, and increased heart sizes