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ANAESTHETIC EQUIPMENT FOR A DEVELOPING COUNTRY
British Journal of Anaesthesia 1991; 67: 360-363
CORRESPONDENCE ANAESTHETIC EQUIPMENT FOR A DEVELOPING COUNTRY Sir,—Pedcrscn and Nyrop describe their solution to the problem of anaesthetic delivery in underdeveloped countries [1]. Unfortunately, the design aims did not specifically address patient safety, and the machine appears to be based on the assumption that nitrous oxide must be made available. Nitrous oxide is not an essential component of modern anaesthesia and should probably be avoided in countries where the cylinder supply and delivery apparatus are unreliable [2] and where continuous measurement of FI O J is impractical. Simple drawover air techniques are extremely safe and will provide satisfactory conditions of anaesthesia for all surgery. If it is accepted that such techniques should be used in the peripheral district hospitals, then it is imperative also to promote their use in the central training establishment. If nitrous oxide is unnecessary, the "machine" component of Pederscn and Nyrop's figure 1 becomes redundant. The oxygen concentrator can be connected directly to the drawover system so that figure 3 resembles the Tri- Service Anaesthetic Apparatus layout [3], a system with considerable saving and additional patient safety. A previously-published account of the Malawi Anaesthetic machine [4] is not referred to, yet this describes several serious clinical problems which should surely have been identified and corrected by extensive clinical trials. Finally, the Manley ventilator recommended [1, 4], must be one of the most unsuitable machines available, as it is extremely extravagant with anaesthetic gases. A simple electricallydriven ventilator would seem to be a more appropriate option. S. Q. M. TIGHE
Gospon
unreliable cylinder supply was one of the reasons for initiating this project. The machine will, indeed, operate without nitrous oxide. The local staff preferred to use a Boyle anaesthetic machine and we decided, therefore, to design a machine to combine a drawover and a continuous flow technique. Several district hospitals have used the vaporizer alone, connected directly to the oxygen concentrator, and I have included a drawover technique in training anaesthetic staff. I do not agree that a simple drawover technique will provide satisfactory conditions of anaesthesia for all surgery, but it will provide satisfactory conditions for most surgery performed. Since the introduction of the Malawi anaesthetic equipment, the use of nitrous oxide has decreased both at District and Central level. In his article, Fenton described his experiences using his modifications [1]. Problems arise, however, using a drawover vaporizer in the presence of positive pressure, especially if the screws are tightened at the overpressure valve [2]. Also, the importance of draining the oxygen concentrator of water has been emphasized by Carter [3]. The equipment was tested in Denmark by extensive clinical trials before delivery, and none of the problems described by Dr Fenton was identified. One reason for this could be that unmodified equipment was used. We bypassed the air outlet because we use air, not oxygen, to power the ventilator; the oxygen concentration decreases significantly if oxygen is used. The same costs arise using either 2 or 25 litre min"1 of air/oxygen, and the oxygen concentrator uses 400 W h"1 independent of flow rate. J. PEDERSEN
Copenhagen REFERENCES 1. Fenton PM. The Malawi anaesthetic machine. Experience with a new type of anaesthetic apparatus for developing countries. Anaesthesia 1989; 44: 498-503. 2. Pedersen J, Nyrop M. The Malawi Model. Anaesthesia 1990; 45:415-^116. 3. Carter MI. Oxygen concentrators and water. Anaesthesia 1990; 45: 68.
REFERENCES 1. Pedersen J, Nyrop M. Anaesthetic equipment for a developing country. British Journal of Anaesthesia 1991; 66: 264-270. 2. Ezi-Ashi TI, Papworth DP, Nunn JF. Inhalational anaesthesia in developing countries. Part I. The problems and the proposed solution. Anaesthesia 1983; 38: 729-735. 3. Houghton IT. The Tri-Service anaesthetic apparatus. SPINAL NEEDLES Anaesthesia 1981; 36: 1094-1109. 4. Fenton PM. The Malawi anaesthetic machine. Experience Sir,—We read with interest the letter by Carrie and Collins with a new type of anaesthetic apparatus for developing [1]. We agree that wider bore pencil-point spinal needles may countries. Anaesthesia 1989; 44: 498-503. resolve both the technical difficulties of the 29-gauge and the greater incidence of post-dural puncture headache (PDPH) seen with bevelled 25- and 26-gauge types. To our mind, the Sir,—I am sorry that Commander Tighe received the technical difficulties of the 29-gauge needle are lack of feel in impression that our project did not specifically address patient needle placement (although this may be overcome with safety, and that nitrous oxide must be available. The experience) and the long delay for CSF to appear at the hub, equipment was designed specifically to address patient safety: usually more than 30 s when the patient is in the lateral mortality rate at the hospitals has decreased approximately position. There is also the risk of needle displacement at 20% since the new equipment was introduced (Information injection, which may account for the high failure rate [2, 3]. from Ministry of Health, Malawi). I agree that nitrous oxide is These are distinct disadvantages in both obstetric emergency not an essential component of modern anaesthesia and the anaesthesia and busy day-case surgical lists.
CORRESPONDENCE ANAESTHETIC EQUIPMENT FOR A DEVELOPING COUNTRY Sir,—Pedcrscn and Nyrop describe their solution to the problem of anaesthetic delivery in underdeveloped countries [1]. Unfortunately, the design aims did not specifically address patient safety, and the machine appears to be based on the assumption that nitrous oxide must be made available. Nitrous oxide is not an essential component of modern anaesthesia and should probably be avoided in countries where the cylinder supply and delivery apparatus are unreliable [2] and where continuous measurement of FI O J is impractical. Simple drawover air techniques are extremely safe and will provide satisfactory conditions of anaesthesia for all surgery. If it is accepted that such techniques should be used in the peripheral district hospitals, then it is imperative also to promote their use in the central training establishment. If nitrous oxide is unnecessary, the "machine" component of Pederscn and Nyrop's figure 1 becomes redundant. The oxygen concentrator can be connected directly to the drawover system so that figure 3 resembles the Tri- Service Anaesthetic Apparatus layout [3], a system with considerable saving and additional patient safety. A previously-published account of the Malawi Anaesthetic machine [4] is not referred to, yet this describes several serious clinical problems which should surely have been identified and corrected by extensive clinical trials. Finally, the Manley ventilator recommended [1, 4], must be one of the most unsuitable machines available, as it is extremely extravagant with anaesthetic gases. A simple electricallydriven ventilator would seem to be a more appropriate option. S. Q. M. TIGHE
Gospon
unreliable cylinder supply was one of the reasons for initiating this project. The machine will, indeed, operate without nitrous oxide. The local staff preferred to use a Boyle anaesthetic machine and we decided, therefore, to design a machine to combine a drawover and a continuous flow technique. Several district hospitals have used the vaporizer alone, connected directly to the oxygen concentrator, and I have included a drawover technique in training anaesthetic staff. I do not agree that a simple drawover technique will provide satisfactory conditions of anaesthesia for all surgery, but it will provide satisfactory conditions for most surgery performed. Since the introduction of the Malawi anaesthetic equipment, the use of nitrous oxide has decreased both at District and Central level. In his article, Fenton described his experiences using his modifications [1]. Problems arise, however, using a drawover vaporizer in the presence of positive pressure, especially if the screws are tightened at the overpressure valve [2]. Also, the importance of draining the oxygen concentrator of water has been emphasized by Carter [3]. The equipment was tested in Denmark by extensive clinical trials before delivery, and none of the problems described by Dr Fenton was identified. One reason for this could be that unmodified equipment was used. We bypassed the air outlet because we use air, not oxygen, to power the ventilator; the oxygen concentration decreases significantly if oxygen is used. The same costs arise using either 2 or 25 litre min"1 of air/oxygen, and the oxygen concentrator uses 400 W h"1 independent of flow rate. J. PEDERSEN
Copenhagen REFERENCES 1. Fenton PM. The Malawi anaesthetic machine. Experience with a new type of anaesthetic apparatus for developing countries. Anaesthesia 1989; 44: 498-503. 2. Pedersen J, Nyrop M. The Malawi Model. Anaesthesia 1990; 45:415-^116. 3. Carter MI. Oxygen concentrators and water. Anaesthesia 1990; 45: 68.
REFERENCES 1. Pedersen J, Nyrop M. Anaesthetic equipment for a developing country. British Journal of Anaesthesia 1991; 66: 264-270. 2. Ezi-Ashi TI, Papworth DP, Nunn JF. Inhalational anaesthesia in developing countries. Part I. The problems and the proposed solution. Anaesthesia 1983; 38: 729-735. 3. Houghton IT. The Tri-Service anaesthetic apparatus. SPINAL NEEDLES Anaesthesia 1981; 36: 1094-1109. 4. Fenton PM. The Malawi anaesthetic machine. Experience Sir,—We read with interest the letter by Carrie and Collins with a new type of anaesthetic apparatus for developing [1]. We agree that wider bore pencil-point spinal needles may countries. Anaesthesia 1989; 44: 498-503. resolve both the technical difficulties of the 29-gauge and the greater incidence of post-dural puncture headache (PDPH) seen with bevelled 25- and 26-gauge types. To our mind, the Sir,—I am sorry that Commander Tighe received the technical difficulties of the 29-gauge needle are lack of feel in impression that our project did not specifically address patient needle placement (although this may be overcome with safety, and that nitrous oxide must be available. The experience) and the long delay for CSF to appear at the hub, equipment was designed specifically to address patient safety: usually more than 30 s when the patient is in the lateral mortality rate at the hospitals has decreased approximately position. There is also the risk of needle displacement at 20% since the new equipment was introduced (Information injection, which may account for the high failure rate [2, 3]. from Ministry of Health, Malawi). I agree that nitrous oxide is These are distinct disadvantages in both obstetric emergency not an essential component of modern anaesthesia and the anaesthesia and busy day-case surgical lists.