Laminar flow: air moves at uniform speed and direction - horizontal (more effective in hip than knee arthroplasty), vertical, exponential (less entrainment)
Q5How is theatre air quality monitored?▸
Colony forming units (CFU)/m3 measured by slit sampler (draws 30 L/min for 2 days)
Sample every 3 months
<20 CFU/m3 in the theatre periphery; <10 CFU/m3 in the centre
Q6What does the literature show for laminar flow?▸
Charnley 1972: deep infection reduced from 9% to 1.5%
Lidwell 1982: clean air 1.7%; clean air + perioperative antibiotic 0.4%; unclean air 3.4%
Q7How should theatre doors be designed?▸
Air cutting doors
Door direction in to out
Q8Compare betadine and chlorhexidine skin preparation.▸
Betadine: inactivated by organic material, skin sensitivity, avoid in pregnancy/breastfeeding; fast onset, bactericidal and works against spores
Chlorhexidine: less sensitivity, longer duration of action, non-toxic in pregnancy/breastfeeding; not effective against viruses and spores
Cochrane 2013 suggests use of chlorhexidine
Q9What is diathermy (electrosurgery)?▸
An operative instrument using high frequency alternating current (500 kHz) to produce a localised heating effect
Used to cut and coagulate tissue
Q10What pad preparation is required before diathermy?▸
Use a pad of 70 cm2
Ensure the skin is clean
Apply conduction gel under the pad
Q11Where should the diathermy pad be placed?▸
Same side as the operative site
Away from bony prominences
Away from metal implants
Q12How does mono-polar diathermy work?▸
Current flows from the generator to the instrument, then through the patient to a second (return) electrode - the diathermy plate
Instrument surface area is much smaller than the plate, so heat is produced at the tip with minimal heat at the plate (low current concentration -> negligible heating effect)
Plate surface area over 70 cm2 (at vascularised muscle mass)
Higher power/voltage required
Q13How does bi-polar diathermy work and what are its advantages?▸
Two electrodes are combined within the instrument, e.g. forceps
The circuit is completed when the two tips/electrodes are in contact - creating localised heat
No patient plate electrode required
Lower power/wattage required
Safer in patients with pacemakers
Q14Compare cutting, coagulation and blend diathermy modes and state the cautions.▸
Coagulation: non-continuous current, high voltage - less local heat so tissue architecture is not changed; cells die and coagulate
Blend: 50%
Local caution: burn, channelling/funnelling effect in narrow pedicle
Systemic caution: current leakage, pacemaker; environment: explosion
Q15What is plaster of Paris made of and what does it become when water is added?▸
POP = anhydrated calcium sulphate + cotton fibre
+H2O -> becomes the crystalline form of gypsum
Q16What type of reaction occurs when plaster of Paris sets?▸
An exothermic reaction - one of the different types of exothermic reaction
POP sets by crystallisation
Q17What question does the source pose about plaster of Paris?▸
How long does it need to set?
The speaker notes record the question but not its answer - details must come from the source image
Q18What is fibreglass (dynacast) made of and what are its pros and cons?▸
Synthetic polymer reinforced by glass fibres with polyurethane resin
Pros: light, strong, short drying time, radiolucent
Cons: expensive, difficult to mould, irritation, sharp turns
Fact check
HEPA filters remove particles larger than 0.5 microns with 99.97% efficiency — incorrect particle size threshold — HEPA filters are defined as removing at least 99.97% of particles of 0.3 microns, the most penetrating particle size — source