Fires And Decontamination

Question 1

What enzymatic process differentiates biological oxidation from combustion?

Answer 1

Biological oxidation uses enzymes to regulate slow, low-temperature reactions (e.g., glucose metabolism), while combustion releases energy rapidly at high temperatures without enzymes.

Question 2

Justify why hypochlorites are recommended for blood spill decontamination despite their limitations.

Answer 2

Hypochlorites have broad-spectrum activity (bacteria, viruses, spores), but must be freshly diluted to avoid corrosion and organic matter inactivation.

Question 3

How does the density of ether vapour influence fire risks in the OR?

Answer 3

Ether vapour sinks and spreads along floors, creating concentrated, explosive pockets that may ignite via unseen sparks.

Question 4

Design a protocol to disinfect a ventilator circuit lacking autoclave access.

Answer 4

Disassemble components, clean with detergent, disinfect in a washer at ≥71°C for 3 minutes, dry thoroughly, and replace every 48 hours.

Question 5

Why are bacterial spores resistant to most disinfectants?

Answer 5

Spores have a keratinized outer layer and metabolic dormancy, requiring prolonged exposure to glutaraldehyde or autoclaving for eradication.

Question 6

Evaluate the risk of reusing single-use endotracheal tubes after disinfection.

Answer 6

Possible if cleaned meticulously and disinfected with 70% alcohol, but thermal methods risk material damage. Not ideal due to potential micro-cracks.

Question 7

What is the stoichiometric mixture of diethyl ether in air, and why is it clinically significant?

Answer 7

3.4% ether in air. Mixtures near this ratio burn explosively, necessitating strict OR ventilation to dilute concentrations.

Question 8

Propose a method to reduce static electricity risks in a low-resource OR.

Answer 8

Use antistatic rubber tubing, ground equipment, avoid synthetic fabrics, and maintain humidity with water containers.

Question 9

Why is formaldehyde rarely used for sterilisation despite its efficacy?

Answer 9

It is irritant, absorbed by materials, and releases hazardous fumes post-sterilisation, posing long-term health risks.

Question 10

Compare the flammability risks of ethyl chloride versus modern volatile agents.

Answer 10

Ethyl chloride explodes in air/O₂ at low concentrations (LL 6.5% in air). Modern agents (e.g., sevoflurane) are non-flammable.

Question 11

Analyze the statement: ‘Alcohol disinfectants require pre-cleaning of equipment.’

Answer 11

True. Organic debris inactivates alcohol; surfaces must be clean for effective microbial reduction.

Question 12

Develop a training module for OR staff on avoiding compression-induced explosions.

Answer 12

Train to avoid lubricants on oxygen valves, inspect cylinders for leaks, and handle gas regulators carefully to prevent adiabatic heating.

Question 13

What makes tuberculosis bacteria resistant to standard chemical disinfectants?

Answer 13

Their waxy, lipid-rich cell walls require prolonged exposure to 2% glutaraldehyde or phenolic solutions.

Question 14

Predict the outcome of using ethylene oxide sterilisation for heat-sensitive equipment.

Answer 14

Effective but requires 2–24 hours, aeration to remove residual gas, and poses toxicity risks if improperly handled.

Question 15

Explain why boiling water cannot sterilize equipment at sea level.

Answer 15

Boiling (100°C) kills microbes but not bacterial spores; autoclaving (≥121°C under pressure) is required for sterilisation.

Question 16

Critique the use of open-mask ether anesthesia in modern practice.

Answer 16

High risk due to flammable vapour spread; closed systems (e.g., LMA) and non-flammable agents are safer alternatives.

Question 17

How does the ‘zone of risk’ concept guide OR layout?

Answer 17

Ignition sources must be kept >25cm from anaesthetic apparatus to avoid sparking explosive gas leaks.

Question 18

Create a decision tree for selecting disinfection vs. sterilisation based on equipment risk category.

Answer 18

High-risk (sterilise), intermediate-risk (disinfect), low-risk (clean/dry). Consider material compatibility and microbial load.

Question 19

Why is Cidex (2% glutaraldehyde) unsuitable for plastic endotracheal tubes?

Answer 19

It may be absorbed by plastic, causing irritation, and requires 30-minute immersion, increasing material degradation risk.

Question 20

Assess the role of heat-moisture exchangers in reducing respiratory circuit contamination.

Answer 20

They trap condensation, reducing microbial growth. Combine with regular circuit changes and drying for optimal safety.

Question 21

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Answer 21

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Question 22

Which three components are necessary for fires or explosions in the operating room?

Answer 22

Combustible substances, oxygen (or nitrous oxide), and an ignition source.

Question 23

What is the primary danger of a ‘cool flame’ produced by ether?

Answer 23

It can act as a powerful ignition source if it encounters an explosive mixture, often remaining undetected until too late.

Question 24

Why is nitrous oxide particularly dangerous in the context of operating room fires?

Answer 24

Nitrous oxide is a strong oxidant that supports combustion as effectively as oxygen, increasing explosion risks.

Question 25

Under what conditions does diethyl ether become explosive in oxygen?

Answer 25

Between 1.5% and 40% v/v concentration, with maximum detonability at approximately 15% in oxygen.

Question 26

Evaluate the risk of using diathermy during anesthesia with ether and oxygen.

Answer 26

Diathermy near ether-oxygen mixtures is extremely dangerous due to explosion risks. Oxygen or diathermy must be switched off.

Question 27

Design a protocol to safely use ether in a resource-limited setting.

Answer 27

Use closed breathing systems (e.g., LMA/intubation), avoid supplemental oxygen near diathermy, ensure ventilation, and store ether in dark, antistatic containers.

Question 28

What distinguishes high-risk medical equipment from intermediate-risk items?

Answer 28

High-risk items enter sterile body areas (e.g., surgical instruments) and require sterilization. Intermediate-risk items contact mucous membranes (e.g., laryngoscopes) and require disinfection.

Question 29

Why is boiling at high altitudes less effective for disinfection?

Answer 29

Boiling temperature decreases with altitude (e.g., 86°C at 4000m), requiring extended boiling times (e.g., 20 minutes) to achieve disinfection.

Question 30

Compare the effectiveness of 70% alcohol vs. 2% glutaraldehyde for disinfecting endotracheal tubes.

Answer 30

70% alcohol is preferred for endotracheal tubes, as glutaraldehyde may be absorbed by plastic and is irritant. Alcohol requires 10-minute immersion.

Question 31

Propose a decontamination strategy for reusable suction catheters.

Answer 31

Clean thoroughly, disinfect with 70% alcohol for 10 minutes, and allow to dry before reuse.

Question 32

What is the minimum autoclave temperature and time required for sterilization?

Answer 32

134°C for 3 minutes or 121°C for 15 minutes under pressurized steam.

Question 33

Why is the azcotropic mixture of halothane and ether considered safer?

Answer 33

It is non-explosive (except at >10% in oxygen) and combines the benefits of both agents while minimizing flammability.

Question 34

How does the Arrhenius law relate to fire risks in the operating room?

Answer 34

Reaction rate doubles with every 10°C temperature increase, accelerating combustion if heat dissipation is inadequate.

Question 35

Justify the use of scavenging systems in ether-based anesthesia.

Answer 35

They remove flammable vapors from the operating room, reducing the risk of explosive mixtures accumulating.

Question 36

Create a checklist for preventing static electricity-induced fires in the OR.

Answer 36

Use antistatic breathing tubes, ensure proper grounding of equipment, maintain humidity, and avoid synthetic materials.

Question 37

What disinfectant is effective against HIV and HBV, and what exposure time is required?

Answer 37

2% glutaraldehyde (Cidex) inactivates these viruses in 1-2 minutes, but soiled items require 30-minute immersion.

Question 38

Why should hypochlorites be avoided for metal instrument disinfection?

Answer 38

They are corrosive to metals and degrade in the presence of organic matter.

Question 39

Analyze the fire risk when using alcohol-soaked drapes near oxygen sources.

Answer 39

Alcohol burns with an invisible flame; soaked drapes can ignite via sparks (e.g., diathermy), especially in oxygen-rich environments.

Question 40

Evaluate the statement: 'Sterilization is unnecessary for respiratory equipment.'

Answer 40

True for most cases, as respiratory infections are not spore-related. Cleaning and disinfection (e.g., 71°C for 3 minutes) suffice.

Question 41

Develop a procedure for decontaminating laryngoscope blades.

Answer 41

Wash after use, then disinfect by soaking in 70% alcohol for 10 minutes or boiling at 100°C for 5 minutes.