Clinical assessment of respiratory disease Flashcards
What is an ultrasound?
High frequency sound waves that bounce off internal organs and tissues via transduce array (shown in photo) to produce 2D images.
What are the two common types of ultrasonography?
B-MODE ULTRASOUND: shows the amplitude as the brightness – produces a cross-section slice, video-type ultrasound that can be displayed live on a monitor. M-MODE ULTRASOUND: captures returning echoes in only one line of the B-mode image that displays them over a time axis – produces a moving display of a structure over time. Image on the right shows how a slice of the left ventricle beats over time.
What are the two probes that can be used in thoracic ultrasonography – their uses?
3.5 MHz probe: lower resolution, but increased depth view – used for deep organs and diaphragm; CURVED ARRAY produces a fan of ultrasound beams to get around the ribs. 7-12 MHz probe: smaller with flat surface (LINEAR ARRAY), that produces higher resolution images with a limited depth of view.
How are the pleura represented on an ultrasound?
Visceral and pleura visible on ultrasound – echogenic line represents both pleura, and will naturally have some bumps and move slowly/smoothly back and forwards underneath the chest wall. Artefacts will be present below the echogenic lung.
What is an echogenic line? What is echogenicity?
Echogenic line – line that represents the interface of structures with different ecogenecities. Echogenecity refers to the ability to reflect or transmit US waves.
How would bone appear on an ultrasound?
Bone appears black with a bright hyperechoic rim.
How are bones and the underlying lung shown on an ultrasound?
Placing probe across the ribs will lead to indentations – form black shadows as all sounds reflected. Ultrasound cannot penetrate the ribs, so the lung can only be seen through the intercostal muscles.
What are secondary pulmonary lobules?
The smallest unit of lung tissue that’s enclosed by a connective tissue septa. They are contain multiple primary pulmonary lobules (defined as the lung unit distal to a bronchiole), and are well-defined along the surface of the lungs.
What are A-line artefacts?
A horizontal artefact indicating a normal lung surface.
What are comet tails? Alternative name?
AKA B-line artefacts. They represent interlobular septa – run perpendicular to the lung surface (interlobular septa are the boundaries between secondary pulmonary lobules). They tend to be a good thing e.g. compressed lungs – you would not usually see comet tails. [PHOTO 7].
What does a normal M-mode ultrasound look like?
B-mode produces a 2D image. M-mode is one dimensional. It is used to study an interface across time. Produces a ‘sea shore’ sign in lungs: at the top, there are parallel lines with no movement at all; at the lung edge where there is the echogenic line, you get a striking white line (indicated by arrow) and below it, you have a sandy appearance which represents the movement of the lung. [PHOTO 9].
What is the normal ultrasonographic appearance of the chest wall in the coronal, paracoronal/parasagittal, longitudinal and axial planes?
CORONAL PLANE: not good for seeing lungs – white lines and below indicate sight of the lungs, but there’s also a lot of obstruction from the ribs. PARACRONAL/PARASAGITTAL PLANE (meaning, line is not quite sagittal; not quite coronal): good for seeing entire lung because an area can be selected where there are no ribs. LONGITUDINAL PLANE and AXIAL – I don’t know if you can see the lungs? [PHOTO 10].
How is fluid shown in an ultrasound?
Black – does not echo.
What circumstances is ultrasonography used to study the thorax? (x6)
- Detect pleural effusion and guide drainage. 2. Differentiate sub-pulmonary (fluid at base of lung) from sub-phrenic fluid (fluid between diaphragm, spleen and liver). 3. Assess tumour invasion of chest wall/pleura. 4. Guide pleural/lung biopsy. 5. Pneumothorax identification – white line of pleura will disappear. 6. Assessment of respiratory muscle function.
How does a pleural effusion appear on an ultrasound? Rule of thumb with volume?
Trace of black between the lung edge and chest wall normal, but in larger pleural effusion, several cm of fluid can accumulate between the lung edge and chest wall – if very large, compression makes the lung look solid and not like lung tissue. RULE OF THUMB FOR VOLUME OF PLEURAL FLUID = 200times the distance between lung and pleural edge is volume of pleural fluid in ml.
What is a pleural effusion?
Collection of free fluid in the pleural space – the space between the visceral and parietal pleura.
What are the muscles of inspiration? (x5) Purpose of each muscle?
Sternocleidomatoid (neck), scalenes (neck), external intercostals, portions of the internal intercostals, diaphragm. Scalenes and SCM contract to elevate the ribs and move the sternum anteriorly. Intercostals contract to elevate the ribs.
What are the muscles of expiration? (x5)
Diaphragm relaxes and moves up. Scalenes and SCM relax to move down the ribs and the sternum posteriorly. External intercostals and some portions of the internal intercostals contract – aided by abdominal muscles to move ribs down.
How does phrenic nerve damage appear on an ultrasound?
Can cause diaphragmatic paralysis and elevation – will present on X-ray with high diaphragm on one/both sides, or liver enlargement on the right.
What is the sniff test? A normal and abnormal result?
It is a test of FORCED INSPIRATION (a sniff). Stimulates phrenic nerve to cause rapid CAUDAL (downwards) MOVEMENT of the diaphragm from diaphragm contraction. If abnormal, then will cause PARADOXICAL (contradictory) CRANIAL (means upwards) MOVEMENT.
What is the muscles response to exercise? What happens to blood levels of O2 and CO2?
Stored energy (ATP and creatinine phosphate (PCr)) is used to generate muscular contraction. Inorganic phosphates, ADP and creatinine drive oxidative phosphorylation while Krebs cycle and glycolysis increase. Oxygen consumption at muscles increase, and initially, CO2 production rises slowly. CO2 rises more slowly because it is highly soluble, so some of it is capable of being stored in tissue and so there is a delay between CO2 levels in the blood and value in the tissue. However, it does eventually rise to match O2 – see photo of the volumes of oxygen consumed (yellow) and CO2 produced (white).
How is oxygen deficit and oxygen debt modelled on an PAO2 graph during and after exercise?
Graph showing amount of oxygen used. [PHOTO 12].
How is cardiac output associated with oxygen consumption? Why is this?
Oxygen consumption rises twice as fast as cardiac output i.e. you are delivering twice as much oxygen as before, but you are consuming four times as much oxygen in the tissues. WHY? Oxygen dissociation curve means that more oxygen is unloaded into tissues for consumption during exercise i.e. a higher proportion of the bloods oxygen saturation is extracted compared with resting state. [PHOTO 13].
How is cardiac output increased? (x2)
To increase cardiac output, initially stroke volume increases. When maximum stroke volume is reached, heart rate increases to increase cardiac output (it’s like riding a bike, you increase gears to go faster, and THEN pedal faster). Stroke volume decreases slightly with increased heart rate, because heart less able to fill with smaller intervals of relaxation.
SUMMARY: what happens to levels of O2, CO2 and ventilation during exercise.
O2 increases.
CO2 increases more when you start anaerobically respiring.
Ventilation increases rate of increase even more when you start anaerobically respiring especially when acidosis is reached.
The point that these increases in rate creates a point of inflection is the point that the body switches to anaerobic respiration.
How does volume-time curve differ for patients with obstructive and restrictive lung disease?
Restrictive: there is no problem with rate of exhalation because it isn’t a problem with the upper airways – the problem relates to reduced lung capacity. FEV1/FVC = >85%. Obstructive: rate of exhalation reduced from increased resistance, FEV1/FVC = 25% and FVC is lower even though total lung capacity is higher.
What can be deduced from a spirometry curve? (x3)
FVC (forced vital capacity): maximum volume expired. FEV1 (forced expiratory volume at 1 second): volume expired after one second. FEV1/FVC is a ratio. PEFR (peak expiratory flow rate) is calculated from the trace (L/min) – by drawing a tangent at the origin when rate is highest.
What does the volume-flow loop combine the information of?
The two pulmonary function tests – PEAK FLOW and VOLUME-TIME.
y = flow rate.
x = volume. Goes USUALLY from highest to lowest.
UP the y-axis = expiration; DOWN the y-axis = inspiration. Tidal volume creates the green ‘circle’ and is very small because tidal volume tends only to represent 0.5 litres of air. On maximum inhalation, volume reaches vital capacity (6 litres), and expiration is initially very rapid, and then there is a LINEAR decrease representing slowing rate.
The flow-volume loop for maximum inhalation and expiration is an ENVELOPE. Breathing always stays within the envelope, no matter how hard you try. PEF = peak expiration flow. Note the volumes that are labelled.
What do flow-volume loops look like in mild and severe obstructive diseases?
COPD MILD OBSTRUCTIVE DISEASE: displaced to the left because lungs are LARGER in the COPD. PEF is slightly lower. Coving because mucous secretion and bronchoconstriction in the smaller airways increase resistance, so offer much lower flow rates. SEVERE OBSTRUCTIVE DISEASE: more exaggerated.
What happens to flow-volume loops in restrictive disease?
Lower volumes. The curve is narrower and not really displaced because it’s a filling problem, and not a ‘moving air’ problem. [Respiratory mechanics – PHOTO 7]. How do flow-volume loops vary in variable extrathoracic, intrathoracic and fixed airway obstruction. Variable extrathoracic obstruction: outside the thorax – INSPIRATION is affected. Variable intrathoracic obstruction: inside the thorax – EXPIRATION affected. Fixes airway obstruction.
