Theatre design and ventilation

THEATRE DESIGN AND VENTILATION

DR.LOKESH SHAROFFOrthopaedic surgeon, Mumbai, India

CONCEPT

• It was first introduced by SIR JOHN CHARNLEY

ZONES IN THEATRE

OUTER ZONE – rest of the hospital outside the theatre complexCLEAN ZONE – theatre complex outside the operating areaASEPTIC ZONE – Operating areaDISPOSAL ZONE – Separate exit for contaminated / used linen and instruments

REQUIREMENTS

AIR DELIVERY SYSTEM

AIR FILTERATION SYSTEM

TEMPERATURE CONTROL

HUMIDITY CONTROL

TEMPERATURE CONTROL

- Ideal working temperature is 19-20 * C – to minimize perspiration

- But causes pt. hypothermia

- PT. body temp. should be 24-26 * C TO AVOID HYPOTHERMIA

HUMIDITY CONTROL

- Should be around 40-60%

- Fastest death of organisms occur at 50% humidity

AIRBORNE PARTICLES

- Measured as BCP/MM3 – Bacteria carrying particles OR CFU/MM3 – Colony forming units

- Each person emits 10k cfu/min at rest and 50k cfu/min with activity

- This is reduced in SCRUBS to 140-830 cfu/min with fask mask and caps.

AIRBORNE PARTICLES

- CONVENTIONAL AC (well maintained)- gives 50-500 cfu/mm3

- All particles are not viable – viable : non viable ratio is 1:1000

- Smallest particle in theatre seen in bright light is 12 microns

- Smallest particle that can carry bacteria is 4-5 microns

AIR FILTERS- 4 LEVELS- ROUGHING FILTERS

removes Large particles and also protects sensitive final filters

- PREFILTERSshould be 95% efficient

- FINAL FILTERSshould be 95% efficient with a particle size of 3 microns

- HEPA FILTERSshould be 99.97% efficient with a particle size of 0.3 microns

HEPA FILTERS

- Each hepa filter has a manometer attached to it to measure the amount of resistance to filteration for clogging purposes.

TYPES OF VENTILATION

High velocity air flow - high speed jets towards operating table - high speed air at periphery

Laminar air flow - horizontal - vertical

CONVENTIONAL WALL DIFFUSER

- Produces plenum- No control of air over operating area- Upto 500 bcp/mm3 – not acceptable for operation theatres

HIGH VELOCITY AIR JET

- Jets increase air turbulence- Flow at 0.6 m/s- Jets may not point at right place and may dessicate the wound

Vertical laminar flow

- Room within a room principle- Air is passed through hepa filters from ceiling downwards- Flow at 0.3 m/s- entrainment can happen by moving personnel

Horizontal laminar flow

- Forms part of a wall - Easy to install - Movement across it will cause uncontrollable turbulence- adequate clean zone is not possible

PERIPHERAL LAMINAR

CONVENTIONAL LAMINAR

Vertical laminar with canopy and side panels

- Canopy – to overcome peripheral entrainment- side panels – extend down to floor to within 20cms from floor- very successful – 10 bcp/m3

Without side panels

- Peripheral entrainment air 0.6 m/s- Higher energy consumption- movement causes deflection of contaminants

EXPONENTIAL AIR FLOW

- Trumpet shaped air flow- Downward and radially outward flow of air - fliteration down to 1 micron- Trays can be positioned even upto ½ m outside the actual canopy

STANDARDS IN AIR FLOW

- Direction of air flow shall be under positive control - max. viable organisms should be not more than 1 cfu/mm3- ULTRA CLEAN ZONE – is less than 10 cfu/mm3

AIR CHANGES

- ATLEAST 20-40 AIR CHANGES PER HOUR

- Pressure gradient should be 1.3-2.5mm h2O(more pressure causes rapid drying of the wound)

AIR QUALITY CONTROL

- Done by CASTELLA SLIT SAMPLER

WATER SUPPLY IN OT

- Tanks and pipes – regular inspection for leakages- Bore well water should be avoided as far as possible- tanks and containers should have covers/lids to protect from dust - water sterilised by ultraviolet radiation

ANTIBIOTIC PROPHYLAXIS

- CHOICE OF AGENT Active against comon pathogens Take into account drug allergy and sensitivity cefazolin/cefotaxim preferred-long duration clinda/vanco in penicillin allergy pts. Modification for pre-existing cultures if already on abx – then continue same

ANTIBIOTIC PROPHYLAXIS

- TIMING Within 15-60 mins prior to incision Vanco should be given 2 hrs before

- Infusion should complete before incision

ANTIBIOTIC PROPHYLAXIS

- DURATION Further dose efficacy is doubtful Max 24 hrs if only prophylatic intra-op – repeat if length of sx more than half life of drug repeat dose if blood loss >1500ml not to continue abx till drain removal

ANTIBIOTIC PROPHYLAXIS

- RISKS- PENICILLIN ALLERGY- ANAPHYLAXIS- ABX ASSOCIATED DIARRHOEA- CLOSTRIDIUM DIFFICLE INFECTION- ABX RESISTANCE- MULTI-RESISTANCE CARRIAGE – SCREENING SHOULD BE DONE IN HIGH RISK CASES

THANK YOU

*Pictures taken from journal of orthopedics today