School of Occupational & Environmental Hygiene Evaluation of a new mask and scavenging system for nitrous oxide used in labour and delivery Emission Control for Humans

School of Occupational & Environmental Hygiene What is the Problem? Second-hand nitrous oxide unhealthy for nurses spontaneous abortions birth defects headaches drowsiness

School of Occupational & Environmental Hygiene What is the source of Nitrous Oxide A Cylinder of mixed N 2 O and O 2 Through the Mom leaks from valve, hose, regulator a possibility

School of Occupational & Environmental Hygiene Present Controls General Ventilation  Supply near ceiling  Exhaust near floor 315 litres/second

School of Occupational & Environmental Hygiene Floor Plan

School of Occupational & Environmental Hygiene Room 6

School of Occupational & Environmental Hygiene The Present Mask

School of Occupational & Environmental Hygiene The Old Scavenger Intermittent Flow Scavenging Positive Pressure in Mask Req’d

School of Occupational & Environmental Hygiene New Control Continuous Scavenging at 15 cfm General Ventilation as before

School of Occupational & Environmental Hygiene New Mask Up Close

School of Occupational & Environmental Hygiene New Mask & Sample Hose

School of Occupational & Environmental Hygiene Experimental Method Measure Parameters  Size of room  Room ventilation air flow  Time of day for all actions  Weight of gas cylinder before and after  With new mask, exhaust air flow before and after  Personal exposure from dosimeter analysis

School of Occupational & Environmental Hygiene Method - continued and observe  Location and mask related actions of patient  location of nurse  concentration of nitrous oxide reported by Miran in room  use of N 2 O in other rooms nearby  concentration of N 2 0 at nursing station.

School of Occupational & Environmental Hygiene Method - Last part Request feedback from nurses  Ease of use  problems with mask or patient Request feedback from Patients

School of Occupational & Environmental Hygiene Results Nurses’ exposures were reduced about 50% Rate of Entonox used varied from 10 to 0.15 grams/minute Patients held mask more than 300 mm from their face There was an apparently random variation in the room* ventilation rate. After the exhaust system was used in the shower flow rate dropped 80%

School of Occupational & Environmental Hygiene Feedback Most patients were willing to use new mask again Some patients wanted a longer exhaust hose Some patients found mask uncomfortable to hold Hose connection point should have been closer to the bed

School of Occupational & Environmental Hygiene More feedback Outer mask made uncomfortable contact with some patient’s faces Hose fell out of mask fitting for some patients. Filter between mask and hose was difficult to install

School of Occupational & Environmental Hygiene Conclusions Continuous scavenging flow of 15 cfm results in significantly lower exposure than intermittent flow scavenging Mask design needs improvement Keeping mask closer to patient’s face would reduce exposures

School of Occupational & Environmental Hygiene More Conclusions Better General Ventilation is needed in Richmond, and is possible. More hospitals should have exposures & control systems checked

School of Occupational & Environmental Hygiene Recommendations – General Vent.

School of Occupational & Environmental Hygiene Change Supply & Exhaust Displacement Supply over Bed Exhaust near head of bed

School of Occupational & Environmental Hygiene Supply Diffusers & Exhaust

School of Occupational & Environmental Hygiene Bed, Exhaust Grilles

School of Occupational & Environmental Hygiene Other Applications Ambulances Emergency ward Other wards?