CXR Interpretation and Spirometry Flashcards
What is spirometry?
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
What is FEV1?
Forced expiratory volume in 1 second. After a full inspiration, the volume of air expired in the first second of forced expiration
What is FVC?
Forced vital capacity. After a full inspiration, the maximum volume of air that can be forcibly expired in one breath
How do you interpret spirometry results?
- Look at the FEV1/FVC ratio (it should be approx 80%, abnormal is less than 70%)
- Look at the FVC and work out the % of predicted normal (i.e. FVC measured/FVC predicted)
- Look at FEV1 and work out the % of predicted normal (i.e. FEV1 measured/FEV1 predicted)
What do NORMAL spirometry patterns look like?
FEV1/FVC > 70% (0.7) – average is approx 80%
FVC > 80% of predicted
FEV1 > 80% of predicted
What do OBSTRUCTED spirometry patterns look like?
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)
Define the gold classification of obstructions
Mild: FEV1 > 80% predicted
Moderate: 50%<FEV1<80% predicted
Severe: 30%<FEV1<50%
Very severe: FEV1 <30% predicted
What do RESTRICTED spirometry patterns look like?
Increased or normal FEV1/FVC ratio
Decreased FVC (<80% of predicted)
Decreased FEV1 (proportional to decreased FVC) or normal
What do MIXED spirometry patterns look like?
Reduced FEV1/FVC (<70% shows obstruction)
Reduced FVC (<80% of predicted shows restriction)
Reduced FEV1 (<80% of predicted shows severity of the obstruction)
What is a chest X-ray?
A CXR is a 2D representation of a 3D object – height and width are maintained but depth is lost
How do we interpret a CXR?
- Pt & film details: labels (name, date, MRN), orientation, projection (PA/AP)
- Film quality: exposure, inspiratory effort, pt position
- Extrathoracic/thoracic: soft tissues, thoracic cage (bones)
- Intrathoracic: mediastinum (trachea, hila, heart), diaphragms (shape, angles, position), lung fields (boundaries, markings, fissures, zones)
- Lines & attachments: drips, drains, tubes, foreign bodies
Where are the zones of the lungs?
Upper zone: above 2nd anterior rib
Middle zone: btw 2nd and 4th anterior ribs
Lower zone: below 4th anterior rib
Abnormal CXRs: consolidation
Consolidation is fluid filled alveoli, often associated with pneumonia. Signs: patchy opacity, air bronchograms, silhouette sign
Abnormal CXRs: air bronchogram
A tubular outline of an airway (darker) made visible by filling of surrounding alveoli by fluid (opaque)
Abnormal CXRs: silhouette sign
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
Abnormal CXRs: collapse (atelectasis)
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
Abnormal CXRs: pleural effusion
Is fluid in the pleural space. Signs include increased opacity, blunting of the costophrenic angle, and a meniscus/fluid line
Abnormal CXRs: pneumothorax
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
Abnormal CXRs: tension pneumothorax
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!!
Abnormal CXRs: emphysea
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)
Abnormal CXRs: pulmonary oedema
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
