Numerous questions to the Committee on Technology are individually and quickly answered each quarter by knowledgeable committee members. Many of those responses would be of value to the general readership, but are not suitable for the Dear SIRS column. Therefore, we have created this simple column to address the needs of our readership.
I have a question about how to ventilate a patient via emergency cricothyrotomy in the OR setting in the absence of a common gas outlet (CGO) on the anesthesia machine. I refer to our Datex-Ohmeda GE Healthcare, Inc. Avance anesthesia machine, which does not have the auxiliary (A)CGO option. However, even if it did, the user manual clearly states, "Do not use the ACGO to drive external ventilators or for jet ventilation." Do you have recommendations for management of ventilation via cricothyrotomy when using the Avance GE machine? Thank you ahead of time for your help with this concern.
Thank you very much for your question to the APSF. The common gas outlets in various machines can be complicated by the presence of check valves and/or pressure relief valves of differing magnitudes. One question back to you now is whether or not you are attempting manual ventilation via the cricothyrotomy device with the manual ventilation bag/circuit, or whether you are trying to jet ventilate through it. This may be dependent upon the type of device used for the cricothyrotomy. Can you specify the situation you are referring to?
Thank you for responding to our question. We currently are not necessarily trying to do either of the options you ask about, but rather are trying to ascertain the most appropriate way to provide emergency ventilation through a cricothyroid puncture with the new Avance machines. It has been a longstanding safety practice within our department to have available in each anesthesia machine an emergency "kit" for cricothyroid puncture/ "jet" ventilation. This "kit" consists of a 14 gauge intravenous catheter with a luer connection to a length of oxygen tubing, with a 15 mm. metal connector at the other end that would fit into our older machines' common gas outlet. Staff had been instructed that, should emergency cricothyroid puncture become necessary, oxygenation should be performed by "jet" ventilation by intermittently pressing the oxygen flush valve.
Since the Avance machines lack a common gas outlet, what is the best means of providing emergency ventilation and/or oxygenation? Are other devices necessary aside from the "kit" I described? Can/should our "kit" be hooked up to the breathing circuit, with the pop-off valve closed while the oxygen flush valve is depressed? The bottom line is what device/procedure is recommended to provide emergency oxygenation and/or ventilation, should cricothyroid puncture become necessary, using the Avance machines?
Thank you for your interest and help.
This subject was one of great interest to me in years past, as the anatomy of the common gas outlet changed with each new Ohmeda machine, in particular. I have a personal, original drawing reproduced here in Figure 1, which represents the relative positions of check valves and low pressure relief valves in the Ohmeda MODULUS I, MODULUS I Selectatec, MODULUS II, MODULUS II Plus, MODULUS CD, and EXCEL. The question was always, "Which one could provide effective pressure for jet ventilation?" The relief valves were either 2.9 or 5.5 psig in those models. According to Rosenblatt and Benumof1, 50 psig is suggested for effective jet ventilation with a 14G catheter or smaller. If the check valve was proximal to the relief valve, then jet vent would not be possible. However, if the relief valve was shielded from the 50 psig wall inlet source by the distal check valve, then it would be possible. The Dräger Medical, Inc. NARKOMED had a higher relief valve setting of 18 psig under the vaporizer dial, without any check valve, which might then allow some degree of jet ventilation.
It is my understanding that the Avance would not support jet ventilation, with or without the auxilliary common gas outlet, because of a similar 5.5 psig low pressure relief valve that is distal to a vaporizer manifold back-check valve.
If you have the auxiliary oxygen flowmeter on your Avance, it is my understanding that the supply to that flowmeter is down-regulated from the cylinder and/or pipeline source, to a value of 35 psig, and is always pressurized without the need to turn on the system switch. Your biomedical technician can check that outlet pressure very easily with a gauge while occluding the outlet port.
Whether or not the maximum flow from that flowmeter is adequate at 35 psig to oxygenate or ventilate is the greater question, and depends upon the restrictor size and details described in the Rosenblatt/Benumof reference. The typical wall source of oxygen in the operating room is 50 psig and could be used with a flowmeter to provide adequate pressure and flow, or it could be accessed through an anesthesia machine “power outlet” with a commercial jet ventilator, if the outlet was available. I would also direct your attention to the Spring 2007 issue of our Q&A column, which describes ancillary sources of jet ventilation capabilities when the machine is not available or does not have such capability: http://www.apsf.org/resource_center/newsletter/2007/spring/15_qanda.htm
Although technical means and various devices exist to provide adequate pressure and flow, a direct connection of high pressure to the bronchial tree, without adequate egress or with excessive entrainment of room air could have significant risks, as described in the reference (35psig is approximately 2.3ATM whereby a clinical inflation pressure of 35 cm H2O is approximately 0.035 ATM). Finally, the reference also describes the different capabilities of ventilation and oxygenation through various cricothyrotomy devices.
The information provided is 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.