A SIMPLE INEXPENSIVE SYSTEM FOR THE REMOVAL OF EXCESS

ANAESTHETIC VAPOURS

D. W. S. BEST, B.A., M.D., C.R.C.P.(C)

THE PAST FEW YEARS have seen the development of numerous devices for the removal of waste anaesthetic vapours from the operating room. Since the cost of equipment requires increasingly careful budgeting, the device we have been using may have some special merit. It is made up of pieces of apparatus already at hand, Its final form resulted from an interplay of ideas of members of the staff of the Department of Anaesthesia, St. Joseph's Hospital, Hamilton.

Our interest in this subject was stimulated in I967, when one of our nurses complained of incapacitating headaches whenever Methoxyflurane was used. We also have a personal interest in allergic problems. Our first efforts to remove the excess gas discharge involved enclosing the expiratory outlet valve in some form of container and applying suction. Experimentation eventually demonstrated that excess gases could be removed at any point beyond the end of the corrugated expiratory tubing. One can attach a length of tubing to the tip of the rebreath- ing bag and lead the gases away to the wall outlet of the room ventilation system. Alternatively, one can apply gentle suction to the tip of the rebreathing bag - but this system is hard to stabilize and requires close monitoring to avoid overfilling or emptying the bag.

THE BASIC UNIT

An Abbott "Venopack" (#4622-13) is modified as follows ( Figure 1 ). (1) The tubing is cut away along with the shoulder of the drip chamber.

This forms the Collecting Chamber. It measures some 50 mm in length by 15 mm in diameter.

(2) The cap is perforated, off-centre 3 or 4 mm, with a circular aperture 7 mm in diameter and replaced.

(3) The air filter sleeve is removed, discarding the filter, and is inserted into the 7-mm aperture in the cap to form a small chimney. This chimney acts as a muffler when suction is applied to the air nipple. It also helps to control the suc- tion effects within the Mixing Chamber.

(4) The ball valve within the air inlet is removed.

APPLICATIONS

(1) Adult ( Ohio "Unitror' anaesthetic machine - #216-6282-810) (a) Circle System (Figures 2 and 3). The "bag-tubing adapter" (#216-3531- 730) is removed from the open circuit side and placed between the end of the expiratory corrugated tubing and the head of the machine. Occasionally it is necessary to adjust for non-fitting metal parts, This is easily done with the neck

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Canad. Anaesth. Soc. J., vol. 18, no. 3, May 1971

334 CANADIAN ANAESTHETISTS' SOCIETY JOURNAL

FmURE 1. Parts derived from "Abbott Venopack".

insert of an adult rebreathing bag. The rubber neck insert from a paediatric breathing bag is inserted into the side arm of the bag tubing adapter (a neat fit). The Collecting Chamber of the device is next placed in the side arm, where it fits neatly inside the rubber collar. Suction is applied to the air nipple. (b) The MagiU Circuit (Figure 4). The Collecting Chamber is fitted with a small collar made from a cut down garden hose washer to make a gas-tight fit within one ann of a regular Y-connector (#309-1046-800). The Collecting Cham- ber, when fully inserted, extends down to the area of the expiratory spill valve. Suction is applied to the air nipple.

(2) Paediatric The open (nipple) end of the paediatric breathing bag is fitted within the Collecting Chamber, and suction applied to the air nipple ( Figure 5).

(3) Assisted Ventilation To product a "sigh", one blocks the chimney and squeezes the bag. With mechanical ventilators one occludes the chimney, but one must also seal off the usual exhaust valve of the ventilator, or, as illustrated (Figure 6), one can remove the cap of the mixing chamber, and insert the end of a regular adult corrugated tubing. This fits neatly and produces a "mixing chamber" of up to 500 ml. With adequate suction, no gases escape into the room.

COMMENT

The essential minimal features of this device are an expiratory port of 3-ram diameter, and free access of applied suction to room air. At flows of anaesthetic gases of 7 litres per minute, with the chimney opposite the suction tip, and a suction of 20 mm Hg vacuum, expiratory positive pressures of up to 6 mm Hg can

.••••Cap with Chimney 27mm

Mixing Expiratory~ Chamber

Port, 3mm Suction Nozz le

E E Collection O Chamber

15mm (M3

15mm (E) l I

Neck Insert from Poediatric Bag

I 22 mm (M)

22mm(F.

Bog Side Arm

~mm~- 22ram

Bag-Tubing Adaptor

FICURE 2. Assembly of the unit for use indicating method of inserting into the circle system by use of a T-Bag adaptor.

336 CANADL~N ANaESTHETXSTS' SOCIETY IOUBNAL

FIGURE 3. The apparatus employed with a circle system.

FIGURE 4. Method of use in the Magill system.

develop. However, if the chimney is rotated nearer to the expiratory port, and the suction adjusted as required, one can generate suction within the breathing systems. One can thus actually obtain zero expiratory pressure, or even a nega- tive pressure within the system and empty the bag.

We feel that the presence of the pop-off valve is a safety device. This is seen in the Magill Circuit arrangement of the device. We do not use this device with

BEST: REMOVAL OF ANAESTHETIC VAPOURS 337

Fmvva~ 5. Paediatric use with a modified Ayre's x-system.

FICURE 6. Application when using a mechanical ventilator.

the mechanical ventilators which we have. Our usual techniques do not require a venting mechanism (except for Nitrous Oxide). Further, sealing off the ventilator head is awkward. As has been emphasized by others, this system should not be used with explosive anaesthetic mixtures.

Some 10 per cent of the general population, including nurses and doctors, have allergic tendencies. The principle of minimizing contacts with allergens

338 CANADIAN ANAESTHETISTS' SOCIETY JOURNAL

or haptens might well encourage the regular use of such as this inexpensive device.

SUMMARY

An inexpensive, simple and adaptable deviee is described as still another method to reduce the pollution of operating areas with waste anaesthetic vapours.

ACKNOWLE~EMENTS

(1) My co-workers, especially Dr. W. Bota, Dr. H. P. Andry, and Dr. J. Far- rell for contributing key ideas.

(2) Our resident, Dr. R. Limjuco, for surveying the literature for me. (3) Mr. Vincent Marehesano, Medical Photography Dept., St. Joseph's Hos-

pital, Hamilton, for photographic work. (4) The operating room nurses at St. Joseph's Hospital, Hamilton, for con-

tinuing encouragement.

REFERENCES

1. MCINTYRE, J. W. R. & RUSSELL, J. C. Removal and Recovery of Halothane and Meth- oxyflurane from Waste Anaesthetic Vapours. Canad. Anaesth. Soc. J. 14. No. 4 (1967).

2. BELFAGE, S.; AHLGREN, J.; & AXELSON, S. Halothane Hepatitis in an Anaesthetist. Lancet 3 (1966).

8. DAvis, D.A. "The Operating Room: an Unhealthy Environment." Modern Anaesthesia. Vol. 2. F.A. Davis, Co. Philadelphia (1968).

4. BRUCE, D. L.; EIDE, K. A.; LINDE, H. W.; & ECKENHOFF, S.E. Causes of Death Among Anaesthesiologists - a 20 year Survey. Anaesthesiology. 29:565 (1968).

5. LINDE, H. W. & BRUCE, D.C. Occupational Exposure of Anaesthetists to Halothane, Nitrous Oxide, and Radiation. Anesthesiology. 80:363 (1969).

6 KLATSKIN, G. & KIMBERC, D.V. Recurrent Hepatitis in Anaesthetists due to Halothane. New England J. Med. 280:515 (1969).

7. MARRESE, R.A. A Safe Method of Discharging Anaesthetic Gases, Anesthesiology. 81: 371 (1969).

8. SCI-INELLE, N. & NELSON, D. A New Device for Collecting and Disposing of Exhause Gases from the Anaesthetic Machine. Anesth. & Analg. 48:744 (1969).

9. YEAXEL, A. E. A Device for Eliminating Overflow Anaesthetic Gases from Anaesthetic Locations. Anesthesiology. 32:280 (1970).

10. CAMERON, H. Polution Control in the Operating Room - a Simple Device for the Removal of Expired Anaesthetic Gases. Canad. Anaesth. Soc. J. 17:535 (1970).

11. PRICE, M. & McKEEvER, R. Anaesthetic Anti-Pollution Device. Canad. Anaesth. Soc. J. 17:540 (1970).

12. COTNAM, H.B. (Memo A-172) Re: Halothane Anaesthesia. Memorandum to all Ontario Coroners. 10 Dec. 1970.

13. LATTEY, M. Halothane Sensitization - A Case Report. Canad. Anaesth. Soc. J. 17: 648 (1970).