Lecture 3: radiology & PFTs Flashcards
T/F
The PA and lateral are most common but AP done when a portable x-ray is required for patient on bed rest.
T
Heart can appear enlarged and its outline softer with the [which view] projection because the heart is further away from the x-ray plate.
AP
First step of analyzing chest radiography: identify details. Which are they
Patient’s name, ID #, age, date and time of film, patient’s position, view of film (PA, AP or lat)
Orient the film properly on the screen
Note presence of various lines and leads, i.e. chest tubes, ET tube, NG tube, EKG leads, central lines, pacemaker wires, etc.
Chest radiography: Step2 is ?
What info are we looking for?
- Evaluation of the radio-opaque bony structures
Normal film exposure - should see intervertebral spaces superimposed on the shadow of the treachea.
Thorax centered - sternoclavicular joints equal distance from the spines of thoracic vertebrae.
Ribs uniformly dense.
T/F
Over-exposed - ↑ Whiteness
F
Chest radiography:
Step is 3 ?
What info are we looking for?
- Evaluation of lung volumes:
Anterior end of ~5-7 ribs should be visible above the diaphragm in the mid-clavicular line.
x-rays:
If more ribs are apparent, what does it mean? If less are apparent?
If more ribs apparent above the hemi-diaphragm, inspiratory volume large or patient hyperinflated.
If fewer ribs apparent above the hemidiaphragm, inspiratory volume small or patient has restricted lung volumes.
Chest radiography:
Step 4?
What are we looking at?
- Evaluation of mediastinal structures:
Tracheal shadow should be in midline: vertical radio-lucent (black) shadow located over the cervical spinous processes that extends inferiorly below the clavicles.
Carina overlies the 4th thoracic vertebrae
Chest radiography:
Step 5?
What are we looking at?
- Evaluation of the heart and great vessels:
Heart shadow slightly to the (L) of center and in contact with the diaphragm.
Aortic knob (L) of midline.
Cardiothoracic ratio (CTR): ratio of heart width to chest width . if greater than 1:2 (50%) is considered abnormal.
Cardiophrenic angle: intersection of vertical curvature of the heart shadow and horizontal curvature of the hemidiaphragm.
example of something that make the cardiophrenic angle / costophrenic angle disapear?
Fluid, ex: pleural effusion
Chest radiography:
Step 6?
What are we looking at?
- Evaluation of the hemi-diaphragms:
(R) hemidiaphragm higher than the (L) - because liver is beneath it.
Can have gas bubbles beneath (L) hemidiaphragm because of stomach or splenic flexure.
Costophrenic angle: intersection between the lateral chest wall and diaphragm - should be sharply defined on both sides.
Chest radiography:
Step 7?
What are we looking at?
- Evaluation of lung fields and boundaries:
Lung boundaries: are normally in contact with the chest wall and diaphragm.
Pleura only visible when an abnormality is present i.e. pleural thickening, fluid or air in the pleural spaces.
Lung fields not completely radiolucent (black) but have faint vascular markings extending in a branch-like manner from the hilum out to lung periphery
What is The silhouette sign (5)
- is the profile of soft tissues superimposed on the lung fields.
- when absent is indicative of airspace disease or fluid-occupying lesions.
- density of atelectatic or pneumonic lungs is same densitiy as soft tissues.
- consolidation or collapse density similar to that of heart or muscle –
- image of the collapsed lung will become confluent with the heart or diaphragm and respective borders will be obliterated.
Résumé:
- when consolidation or atelectasis affects any portion of lung adjacent to the cardiac or diaphragmatic border, that border can no longer be visualized radiologically.
How can you identify a pneumothorax on x-ray?
Pneumothorax: vasculatue is in the lungs and collapse with the lungs if collapse
Spirometry: 3 caracteristics
Assesses mechanical state of the lungs
Flow or volume-displacement devices
Volume-time spirogram; FEV1 and FVC
Spirometry: procedure?
Subject inspires maximally and then exhales as hard and as completely as he/she can.
The volume exhaled in the first second is called the forced expiratory volume or FEV1 and the total exhaled volume is called the forced vital capacity or FVC
The FVC is slightly less than the slow vital capacity; normally the FEV1 is about 80% of the slow FVC.
Reason for reduction in FEV1 (4)
Reductions in FEV1 Reduction in TLC Obstruction of the airways Loss of lung recoil Significant weakness of the respiratory muscles
Obstruction vs restriction: what are the increase/decrease in
FEV1/FVC & FVC?
Obstruction: FEV1/FVC low; FVC normal or low
Restriction: FEV1/FVC normal; FVC low
T/F
Spirometry measures FVC or slow vital capacity (SVC), the total lung capacity (TLC), functional residual capacity (FRC) but not the residual volume (RV).
F
Spirometry measures FVC or slow vital capacity (SVC) but not total lung capacity (TLC), functional residual capacity (FRC) and residual volume (RV).
What complete the spirometry?
How to measure the lung volumes
Total body plethysmography
Helium dilution and nitrogen washout are methods used to measure FRC
TLC and RV are calculated once FRC is measured and vital capacity (VC) obtained with spirometry.
What other technique to measure FRC ?
Helium dilution
Restricitve lung disease: effect on
TLC, RV, fev1/fvc, VC, FRC, FEV1
TLC: low RV: N/low FEV/FVC ratio: N/high FEV1: N/low FVC: low VC, FRC: low
Obstructive lung disease: effect on
TLC, RV, fev1/fvc, FEV1
TLC: high RV: high FEV/FVC ratio: low FEV1: low FVC: N/low
What measure DLCO
Measures the ability of a gas to transfer from alveolar gas into the pulmonary capillary blood = gas exchange.
What factor determine dlco (4)?
Major factors determining DLco:
The gas exchange surface area (lung-blood interface)
Thickness of alveolar wall
Difference between the partial pressure of the gas in the alveolus and the red cell
Blood flow to the alveoli that receive ventilation
what is a normal dlco?
Normal DLco =
25 ml/min/mm Hg
Normal = ± 20% predicted i.e. 80-120% pred
how dlco is measured?
CO high affinity, attah to Hb pass readaly trhough the basal mbn, person breathing and exhale completely, ihnhale completely to total lung cap, hold, exhale rapidly, first 700ml (dead space) discarded, the next 500ml collected, as analyzed for CO & helium
what condition reduce diffusion capacity? (7)
Anemia
Increased interstitial/ intra-alveolar fluid
Congestive heart failure
Renal failure
Mismatching of alveoli and capillaries
COPD
Pulmonary vascular disease
Thickening of the alveolar capillary membrane
Fibrosing alveolitis
Reduced area of alveolar capillary membrane
Emphysema
Pretest smoking (COHg)
Breath-hold time too short
