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Pollution with nitrous oxide using laryngeal mask or face mask
M Jenstrup1, K O Fruergaard, C R Mortensen
1Department of Anaesthesia and Intensive Care, Copenhagen University Hospital, Rigshospitalet, Denmark.
Acta Anaesthesiologica Scandinavica
|July 17, 1999
Summary
Nitrous oxide (N2O) leakage was lower with laryngeal mask airway (LMA) ventilation compared to face mask ventilation. However, both methods resulted in N2O levels considered excessively high for operating theatre personnel safety.
Area of Science:
- Anesthesiology
- Occupational Health
- Environmental Health
Background:
- Environmental pollution from anesthetic gases like nitrous oxide (N2O) poses potential health risks to operating theatre staff.
- Assessing N2O leakage during controlled ventilation is crucial for understanding and mitigating occupational exposure.
Purpose of the Study:
- To quantify and compare the incidence and magnitude of N2O leakage during controlled ventilation using a face mask versus a laryngeal mask airway (LMA).
- To evaluate the environmental N2O concentrations in the breathing zone of anesthesiologists during these procedures.
Main Methods:
- A semi-closed gas delivery system with active scavenging was employed in 34 patients undergoing elective cystoscopy.
- Nitrous oxide concentrations were measured using a gas monitor at 30 cm above the patient's mouth at 8-second intervals.
Main Results:
- Face mask ventilation resulted in a median N2O concentration of 157 p.p.m., significantly higher than the 60 p.p.m. with LMA (P=0.04).
- Concentrations above 100 p.p.m. occurred during 51% of the time with a face mask, compared to 24% with an LMA.
Conclusions:
- Laryngeal mask airway (LMA) ventilation demonstrated reduced environmental pollution with N2O compared to face mask ventilation.
- Both ventilation methods were associated with N2O peak concentrations exceeding occupational safety limits set by Danish authorities.