Abstract
Purpose: :
To better classify the difference in fire risk, as defined by oxygen concentration greater than 28%, when using nasal cannula versus face mask during open draped ophthalmic surgery.
Methods: :
This was a prospective, non-randomized study. Informed consent was obtained from patients on the day of their planned surgical procedure. Choice of nasal cannula versus face mask was determined by anesthesiology. After anesthesia induction and draping, measurements were made at seven precise locations using a Teledyne AD300 handheld oxygen sensor. Mean oxygen concentrations were calculated for each modality at each of the seven locations. Oxygen leaks were defined as any reading greater than twenty-eight percent (atmospheric O2=20.9%) Statistically significant differences in oxygen concentration between nasal cannula and face mask were determined using the Wilcoxon Test, Wilcoxon Rank Sum, and the Student’s T-Test.
Results: :
Nasal cannula produced no single readings at any periorbital points above our cutoff for significance (O2>28%). With face mask, 36% of readings were at or above 28% O2, and the majority of patients (90%) had at least one reading greater than twenty-eight percent. In addition, 55% of face mask readings at the lateral canthi were elevated with a mean reading of 30%(SD=8.92)at the left lateral canthi and 28%(SD=7.64) at the right lateral canthi. In addition, Wilcoxon rank analysis demonstrated a statistically significant difference in oxygen concentration between face mask and nasal cannula at the canthi (R Lat. Canthus = .0088; L Lat. Canthus = .001). Flow rate did not play a role in the incidence of leakage with face mask, but increasing oxygen flow rates corresponded to increasing oxygen concentrations at the right lateral canthi and above the face mask.
Conclusions: :
The use of face mask does not constitute a manageable risk and its use is no longer appropriate during open draped ophthalmic surgery.
Keywords: oxygen • differentiation