Dear SIRS refers to the Safety Information Response System. The purpose of this column is to allow expeditious communication of technology-related safety concerns raised by our readers, with input and responses from manufacturers and industry representatives. This process was developed by Drs. Michael Olympio, Chair of the Committee on Technology, and Robert Morell, Editor of this newsletter. Dr. Olympio is overseeing the column and coordinating the readers' inquiries and the responses from industry. Dear SIRS made its debut in the Spring 2004 issue.
The information in this column is provided for safety-related educational purposes only, and does not constitute medical or legal advice. Individual or group responses are only commentary, provided for purposes of education or discussion, and are neither statements of advice nor the opinions of APSF. It is not the intention of APSF to provide specific medical or legal advice or to endorse any specific views or recommendations in response to the inquiries posted. In no event shall APSF be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with the reliance on any such information.
Go With the Flow (of O2)
A free-standing ASC where I work has recently begun using the Datascope AS 3000 gas machines. I am concerned about the gas flow controls.
I am concerned that when one turns on nitrous oxide, both nitrous oxide and oxygen flows increase. When N2O flow is decreased, the O2 flow correspondingly decreases to its original setting.
However, when I perform a pediatric general inhalational induction, I begin with N2O and O2 in a 70-30 admixture. If the N2O is turned on first, the O2 flow rises. When the N2O flow is decreased, so too is the O2 flow. If both gases begin at 0 L/m, decreasing N2O flow will reduce O2 flow to 0 L/m. To illustrate, N2O flow is increased to 7 L/m and O2 flow rises to about 4 L/m. Using sevoflurane, when an adequate level of anesthesia is attained, flows are adjusted to a 50-50 admixture. This results in O2 flow decreasing to near zero, or 200 ml/min. This necessitates resetting the O2 flow to equal that of N2O.
Yesterday, in the pediatric ENT room, this questionable mechanism resulted in no fewer than 8 flow control knob adjustments. I feel it is inherently unsafe that O2 flow can decrease to near zero independent of someone physically turning the flow control knob. Where is the reciprocating gear mechanism that links the flow control knobs in this system? It is as if the gear system is reversed.
Figure 1. Manufacturer's representation of an anesthesia
Again, I feel that oxygen flow should only decrease when one physically turns the O2 flow control knob. I feel this apparatus is minimally safe and maximally impractical. Further, I feel that these gas flow control knob adjustments greatly increase the workload in an already busy setting.
Thank you so much for your time and attention in this matter.