Biophysics Flashcards
Whilst using electrosurgery during a hysterectomy, the surgeon sees carbon on the tip of the electrode during the operation. What temperature has been reached?
200°C
Optimum intra-abdominal pressure should be achieved to insert the primary trocar safely at laparoscopy. What is the optimum pressure range?
20–25 mmHg
What is the normal axis of the heart?
–30 to +90 degrees
In cases of right ventricular hypertrophy the axis shifts to the right and there is left shift with left ventricular hypertrophy.
In a Dexa bone mineral density scan, the results are reported in two ways: the T score and the Z score. Which statement correctly describes the T score and the Z score?
T score which compares the individual to a young adult where normal is greater than –1
Z score which compares the individual to another individual of the same age and gender
A T score between +1 and –1 indicates a normal bone (since it is compared to a younger population it is likely to be a negative cut-off). A patient with a score between –1 and –2.5 is osteopenic. A score of less than –2.5 is osteoporotic. A Z score of less than -1 is suggestive of factors other than aging, such as thyroid problems, malnutrition, medications etc., contributing to the osteoporosis.
You wish to achieve a cutting and simultaneous coagulation effect from the diathermy machine. How is this best achieved?
Use monopolar diathermy with blended waveform
In monopolar diathermy which feature prevents electrocution occurring?
High frequency
With regard to ultrasound with colour Doppler, how can the blue coloured flow pattern be described?
Flow away from the colour box
Which laser can be used in gynaecological surgery, is invisible without an aim beam and cannot be transmitted down a fibre optic cable?
Carbon dioxide
The CO2 laser generates an invisible light and requires an aiming beam, usually helium–neon. It cannot be transmitted down a fibre optic cable and is absorbed by water. It is used in cervical treatment but is limited by the fact that it does not work in the presence of blood.
At the end of surgery you notice an area of burn near the attached diathermy plate. The diathermy plate seems to be partially detached. Which of the following would be the most likely aetiology?
Current density was concentrated in a smaller area than usual
What would be the frequency of the electric current used in electrosurgery?
500 Hz
You have been asked to review an early pregnancy ultrasound scan that shows a mean gestational sac of less than 25 mm and a crown rump length less than 6 mm with no visible fetal heart. What is the likely diagnosis?
Pregnancy of uncertain viability
This woman should be reassessed in 7 to 10 days time to assess viability, according to RCOG criteria.
If the gestational sac is larger than 25 mm with no fetal pole, it is suggestive of silent miscarriage.
In the case of hypocalcaemia, what electrocardiography (ECG) changes typically occur?
Long QT interval
What drugs cause long QT?
haloperidol, erythromycin and terfenadine.
With regard to the jugular venous pressure (JVP) waveform, what can cause an elevated JVP reading with a normal waveform?
Right-sided heart failure
A 53-year-old woman presents with chronic renal failure and a potassium concentration of 5.8 mmol/l.
An electrocardiogram (ECG) has been requested. What ECG feature can occur with this potassium concentration?
Tall T waves, wide QRS complex
