Week 9 - CXR Interpretation Flashcards
Spirometry (Measures)
Measure the volume of air that the patient can forcible expel from their lungs after a max inspiration / How quickly the air can be expelled
- Measurements include FEV1 and FVC
What is spirometry used for?
Aid diagnosis, detect/quantify the degree of airway obstruction or restriction, monitor effects of treatment.
FEV1
- Forced expiratory volume in 1 second
- After a full inspiration, the volume of air expired in the 1st second of forced expiration.
- values between 80-120% of avg. are considered normal
FVC
- Forced vital capacity
- After a max inspiration, the max volume of air that can be forcibly expired in one breath.
- Critical in the diagnosis of obstructive + restrictive diseases.
Ratio of FEV1/FVC
Normal = ~ 80% Abnormal = <70%
Normal reading spirometry
FEV1/FVC > 70% (avg = 80)
FVC > 80% of predicted
FEV1 > 80% of predicted
Obstructive meaning spirometry
- Pt’s cannot EXHALE the air in their lungs quickly as something is obstructing their airways
- FVC often preserved or reduced but to a lesser degree.
- Pre/post bronchodilators used to assess degree of reversibility.
Obstructive reading spirometry
- Decreased FEV1/FVC ratio (<70%)
- Decreased FEV1 (<80% predicted)
- FVC normal or decreased but to a lesser degree
Obstructive gold classification (FEV1)
Mild - >/= 80%
Moderate = 50-79%
Severe = 30-49%
Very Severe = < 30% predicted
Obstructive airways could be due to:
- Bronchospasm (tightening of the muscles that line the airways (bronchi) in your lungs. When these muscles tighten, your airways narrow)
- Inflammation
- Secretion/mucus
- Loss of elasticity in bronchial walls (floppy airways)
Restrictive reading spirometry
- Something restricting the INSPIRATION of air into the lungs, so lung volumes are reduced.
- Look mainly for a decrease in FVC
- Increased or normal FEV1/FVC ratio
- Decreased FVC (<80% predicted)
- Decreased FEV1 (proportional to decreased FVC or normal)
Restriction in airways due to:
- Lung issues: Pulmonary fibrosis
- Chest wall issues: scoliosis, obesity
- Weak muscles/damaged nerves: MND, SCI (lacking ability to fully inspire)
Mixed reading spirometry
- Issue is with both intake of air into lung (restrictive) & exhaling of air out of lungs (obstruction)
- Decreased FEV1/FVC (<70% - obstruction)
- Decreased FVC (<80% predicted - restriction)
- Decreased FEV1 (<80% predicted - shows severity of obstruction)
Chest x-ray (CXR)
A 2 dimensional representation of a 3 dimensional object- height/width maintained, depth lost
Black on XR
(Translucent/translucency) Air/gas
Gray on XR
(Opaque/opacity) Fat, soft tissues, + water
White on XR
(Opaque/opacity) Bone and metal
The denser the tissue- the whiter it is
Patient & film details
- Labels: Name, MRN, date, time
- Orientation
- Projection
Projection (PA)
- Postero-anterior
- Rays passing from back to front, usually standing, scapula removed from view.
Projection (AP)
- Antero-posterior
- Rays passing from front to back, pt can be supine, scapula seen in XR
- less ideal
- Shows magnification of the heart/widening of the mediastinum (especially supine)
Film quality
Exposure, inspiratory effect, pt position.
- You should just see the intervertebral(IV) disc spaces behind the heart (but can see them easily behind the trachea)
Film quality (over-exposure)
- Film is darker (more translucent)
- Can see IV disc spaces behind the heart easily
- Easy to miss problems
Film quality (under-exposed)
- Film is whiter (more opaque)
- Can’t see IV disc spaces behind the heart/trachea
- May over-diagnose
Film quality (inspiratory effect)
- Taken at end of full inspiration
- Good inspiration: Count 6 ant. ribs or 9-10 post. ribs, cutting the diaphragm mid-clavicular line.
