Clinical assessment of resp disease Flashcards
What is ultrasonography?
Uses a probed to produce high frequency sound waves that are reflected from the boundaries of internal organs and tissues, before detection by a transducer array to produce a 2d image
What are the two types of Probe used in ultrasound?
3.5MHz probe: lower res but increased depth of view - used for deep organs and diaphragm; curved array produces a fan of ultrasound beams to get round the ribs
7-12 MHz probe: smaller with flat surface (linear array), that produces higher res images with a limited depth of view
Describe normal lung appearance on US:
Visceral and parietal pleura visible on US - echogenic line represents both pleura, and will naturally have some bumps and move slowly/smoothly back and forwards underneath chest wall; artefacts will be present below echogenic lung
What are B line artefacts (comet tails)?
They represent interlobular septa - run perpendicular to the lung surface (interlobular septa are the boundaries between secondary pulmonary lobules)
What is M-mode ultrasound?
1D display of motion of echo-producing interfaces displayed against time
What should a normal M-mode US of lungs look like?
Should be the sea shore sign; lung pleura should look striated and lung sandy while chest wall should be comprised of straight lines
What are the functions of Lung ultrasound?
- Detect pleural effusion and guide drainage
- Differentiate sub-pulmonary from sub-phrenic fluid
- Assess tumour invasion of chest wall/pleura
- Guide pleural/lung biopsy
- Pneumothorax identification - white line of pleura will disappear
- Assessment of respiratory muscle function
What is seen during a pleural effusion?
Only a trace of black should exist between lung edge and chest wall, but in a larger pleural effusion, several cm of fluid can accumulate (volume in ml = 200 * distance on US) - if very large, compression makes the lung look solid and not like lung tissue
What is the sniff test?
Sniffing stimulates phrenic nerve to cause rapid caudal movement of the diaphragm (if damaged then will cause paradoxical cranial movement)
What is the respiratory quotient?
CO2 prod/O2 consumption
Usually 1
What is the average O2 requirement at rest?
Roughly 3.5ml/min/kg
How much more oxygen is required when standing, walking and running?
Standing: x1.5
Walking: x2
Running: >7
What is the response of muscles to exercise?
Stored energy (ATP, PCr) used to generate muscular contraction; inorganic phosphates, ADP and creatine drive oxidative phosphorylation while Krebs/glycolysis increases; oxygen consumption at muscle increases, and initially CO2 production rises slowly (as buffered), but then rises to match O2
What id the circulatory response to exercise?
Q increases linearly with intensity until plateaus as maximum reached, alongside HR and oxygen consumption - exercise limited by cardiac output; when HR too fast, filling time in diastole reduced, which reduces SV after a peak
What is the lungs response to exercise?
TV increases with ventilation up to a peak where plateaus, and breathing frequency increases - will breathe at half vital capacity in exercise (increase further not as efficient); VQ matching at rest not ideal, but in exercise increases
What is Incremental aerobic metabolism?
Oxygen flow matches demand; total body RQ rises towards 1 as glucose becomes predominant fuel source; ventilation increases to match CO2 production
What is the Bohr effect?
as pH increases, Bohr shift of ODC to right so at given PO2 Hb has less affinity to oxygen so offloads more to acidotic muscles.
What is Acidosis?
Lactate converted to protons, and is buffered by bicarbonate to increase CO2, increased ventilation allows pH to remain relatively stable; when [H+] exceeds HCO3- cannot buffer and begin hyperventilation
Describe a cardiopulmonary exercise test:
Patient on a bike has continuous ECG and gas exchange monitoring and the power is slowly increased to put cardiopulmonary strain on the patient - can be used to detect heart/lung conditions/restrictions on exercise etc.
Describe how to do spirometry:
Wearing a noseclip, patient inhales to TLC, then exhales as hard and fast as possible for six seconds into vitalograph
In spirometry, what do FVC, FEV1 and FET stand for?
FVC: Forced Vital capacity
FEV1: Forced expiratory volume in 1 second
FET: Forced expiratory time
How would spirometry from someone with obstructive lung disease be different?
Much slower exhalation rate, FEV lower and FEV1:FVC ratio 25% (volume reduced because airways narrowed)
How would a spirograph from someone with Restrictive lung disease be different?
Similar rate but lower FVC
(airways ok, but volume affected)
Describe what Spirographs from normal, restricted and obstructed people would look like:
