K. J. WISHA W ET AL.
238
ACKNOWLEDGEMENTS We wish to sincerely thank Messrs Rob Wilkins, Murray Hinder, and Peter Caval of the Biomedical Engineering Department at Westmead Hospital who were involved in the project from its inception and built an initial mockup as well as the eventual production models. Without their invaluable technical advice the project would never have progressed beyond the idea stage. We also wish to acknowledge the support of Hewlett Packard, who donated to the CareFlight organisation a Vectra 2000 personal computer complete with graphics package on which the initial design was formulated. Our thanks also to Dr. Tom Voss for advice and Mrs. Marie Guthrie who edited this manuscript.
REFERENCES 1. Waddell G, Scott PDR, Lees NW, Ledingham I
MeA. Effects of ambulance transport in critically ill patients. Br Med J 1975; 1:386-9. 2. Hothersall AP et al. Mobile intensive care 11 Secondary transport. In: Recent Advances in Intensive Therapy; Ledingham I MeA, ed. Churchill Livingstone, Edinburgh 1977; 239-50.
3. Gentleman D. Jennett B. Hazards of interhospital transfer of comatose head injured patients. Lancet 1981; 11:853-5. 4.
Marsh RHK, Ledingham I MeA. Equipment for mobile intensive care. Br J Hosp Med 1981 ; 24:377-82.
5. Bacon RJ, Palmer SC, Grimes AP, Wishaw KJ, Nielsen MS. A mobile intensive care unit. Intens Ther Clin Monitor 1988; 9:256-7. 6. Aitkenhead AR, Willis MI, Barnes WHo An economical mobile intensive care unit. Br Med J 1980; 1219-21.
Park GR, Johnson S, Ferguson A, Grant D. A mobile intensive care unit based on a standard ambulance trolley bed. Br J Anaesth 1982; 54: 1081-5. 8. Noy-Man Y, Papa MZ, Margaliot SZ. Portable air mobile life support unit. Aviat Space Environ Med 7.
1985; 598-600. 9. Dawson ADG, Babington PCB. An intensive care
trolley - An economical and versatile alternative to the mobile Intensive Care Unit. Anaesth Intens Care 1987; 15:229-33 10. Siker D, Hoffman G, Gostisha M. Blood pressures on the road. Presented at AirMed 88 Conference, Boston Mass, Sept 19-23 1988; Abstract in AeroMed J 1988; 5(3):64. 11. Lambrew CT. Mobile intensive care I - Primary
transport. In: Recent Advances in Intensive Therapy. Ledingham I MeA, ed. Churchill Livingstone, Edinburgh 1977; 231-8. 12. Waddell G. Movement of critically ill patients within hospital. Br Med J 1975; 2:417-9.
A Scavenging System for Use in Paediatric Anaesthesia I. M. STEVEN*
Department of Anaesthesia, Adelaide Children's Hospital, Adelaide, South Australia Key Words: EQUIPMENT: scavenging system, Ayres' T-Piece
Since the reports in the early 1970s of the problems associated with prolonged exposure to anaesthetic gases,I-4 scavenging is now a recommended requirementS to avoid the hazards to staff employed in the operating theatre. In adult systems scavenging has not *F.F.A.R.A.C.S., Senior Visiting Anaesthetist. Address for Reprints: Dr. I. M. Steven, Department of Anaesthesia. Adelaide Children's Hospital, North Adelaide, S.A. S006. Accepted for publication January 31,1990
been a major problem as an interface, a 'hood', can be fitted over the escape valve and the gases passively delivered to a 'dump' which is then actively exhausted, The T-piece system used in paediatric anaesthesia has no valve and the release of gases is via the open tail of the breathing bag. Most scavenging systems for the T-piece system are attached to the tail of the bag,6-8 the exception to this being the scavenging dish Anaesthesia and lntensi,'e Care, Vol. 18, No. 2. May, 1990
239
SCAVENGING SYSTEM IN PAEDIATRIC ANAESTHESIA
system described by Hatch et aU Attachments to the tail of the breathing bag have the great disadvantage that they may obstruct the tail of the bag by twisting, resulting in greatly increased pressures in the lungs and serious damage. They may also be cumbersome and make manual ventilation difficult. With the scavenging dish it is necessary to hold the bag precisely over the scavenging dish in order to be efficient and this may not be convenient or comfortable. Consideration was given to installing an escape valve proximal to the breathing bag and this would then have a hood and be scavenged as with the adult system - the tail of the breathing bag would then be closed. In this modification aT-piece has been placed proximal to the breathing bag and a tube leads from the limb of the 'T' to a control valve plugged into an interface mounted on the front of the anaesthetic machine. The interface is led to a dump. Or. J. Inkster at The Hospital for Sick Children, Newcastle-uponTyne, was using a similar system when I visited him. DESCRIPTION
The system has aT-piece connector with standard 15 mm tapers (A, Figure 1) which can be easily incorporated between the expiratory limb and the breathing bag of the
Jackson Rees modification of the Ayres' T -piece system. The gases are exhausted from the system via the side arm of the T -piece (a, Figure 1) and the tail of the bag is closed with some form of clamp (C, Figure 1) which is easily applied and removed, e.g. a paper or gate clip. The side arm of the T -piece (a) is of adequate diameter so that there is minimal resistance to the escape of gases at an 8 litre/ minute gas flow (Figure 2). A lightweight but not easily obstructed tube carries the gases from the T-piece limb (a) to a scavenge valve (B, Figure 1). This valve has a standard scavenge 19 mm taper which fits into a corresponding taper on the interface (0, Figure 1) which is mounted on the front panel of the anaesthetic machine. The valve may be readily interchanged with a tube which is carrying exhaust gases from the hood over the exhaust valve of the circle absorber system. The scavenge valve has a control with four settings (off, 1,2,3) with which to vary the rate of escape of the exhaust gases. This variation allows the system to be used with both spontaneous and manually controlled ventilation. With mechanical ventilation the system is removed and the ventilator is scavenged. The valve is constructed with a safety feature so that when in the 'off position it is not fully closed but will only allow a pressure of 30 cm of water with an 8 litre/ minute gas flow (Figure 2). In position 3 there 30
...
~ o .
Cl):O::
INTERFACE
[lr-TO
~UMP
D
~ (/l
(/l
Cl)
...
c E 20 ......
.-
-
a.. co ~
238
ACKNOWLEDGEMENTS We wish to sincerely thank Messrs Rob Wilkins, Murray Hinder, and Peter Caval of the Biomedical Engineering Department at Westmead Hospital who were involved in the project from its inception and built an initial mockup as well as the eventual production models. Without their invaluable technical advice the project would never have progressed beyond the idea stage. We also wish to acknowledge the support of Hewlett Packard, who donated to the CareFlight organisation a Vectra 2000 personal computer complete with graphics package on which the initial design was formulated. Our thanks also to Dr. Tom Voss for advice and Mrs. Marie Guthrie who edited this manuscript.
REFERENCES 1. Waddell G, Scott PDR, Lees NW, Ledingham I
MeA. Effects of ambulance transport in critically ill patients. Br Med J 1975; 1:386-9. 2. Hothersall AP et al. Mobile intensive care 11 Secondary transport. In: Recent Advances in Intensive Therapy; Ledingham I MeA, ed. Churchill Livingstone, Edinburgh 1977; 239-50.
3. Gentleman D. Jennett B. Hazards of interhospital transfer of comatose head injured patients. Lancet 1981; 11:853-5. 4.
Marsh RHK, Ledingham I MeA. Equipment for mobile intensive care. Br J Hosp Med 1981 ; 24:377-82.
5. Bacon RJ, Palmer SC, Grimes AP, Wishaw KJ, Nielsen MS. A mobile intensive care unit. Intens Ther Clin Monitor 1988; 9:256-7. 6. Aitkenhead AR, Willis MI, Barnes WHo An economical mobile intensive care unit. Br Med J 1980; 1219-21.
Park GR, Johnson S, Ferguson A, Grant D. A mobile intensive care unit based on a standard ambulance trolley bed. Br J Anaesth 1982; 54: 1081-5. 8. Noy-Man Y, Papa MZ, Margaliot SZ. Portable air mobile life support unit. Aviat Space Environ Med 7.
1985; 598-600. 9. Dawson ADG, Babington PCB. An intensive care
trolley - An economical and versatile alternative to the mobile Intensive Care Unit. Anaesth Intens Care 1987; 15:229-33 10. Siker D, Hoffman G, Gostisha M. Blood pressures on the road. Presented at AirMed 88 Conference, Boston Mass, Sept 19-23 1988; Abstract in AeroMed J 1988; 5(3):64. 11. Lambrew CT. Mobile intensive care I - Primary
transport. In: Recent Advances in Intensive Therapy. Ledingham I MeA, ed. Churchill Livingstone, Edinburgh 1977; 231-8. 12. Waddell G. Movement of critically ill patients within hospital. Br Med J 1975; 2:417-9.
A Scavenging System for Use in Paediatric Anaesthesia I. M. STEVEN*
Department of Anaesthesia, Adelaide Children's Hospital, Adelaide, South Australia Key Words: EQUIPMENT: scavenging system, Ayres' T-Piece
Since the reports in the early 1970s of the problems associated with prolonged exposure to anaesthetic gases,I-4 scavenging is now a recommended requirementS to avoid the hazards to staff employed in the operating theatre. In adult systems scavenging has not *F.F.A.R.A.C.S., Senior Visiting Anaesthetist. Address for Reprints: Dr. I. M. Steven, Department of Anaesthesia. Adelaide Children's Hospital, North Adelaide, S.A. S006. Accepted for publication January 31,1990
been a major problem as an interface, a 'hood', can be fitted over the escape valve and the gases passively delivered to a 'dump' which is then actively exhausted, The T-piece system used in paediatric anaesthesia has no valve and the release of gases is via the open tail of the breathing bag. Most scavenging systems for the T-piece system are attached to the tail of the bag,6-8 the exception to this being the scavenging dish Anaesthesia and lntensi,'e Care, Vol. 18, No. 2. May, 1990
239
SCAVENGING SYSTEM IN PAEDIATRIC ANAESTHESIA
system described by Hatch et aU Attachments to the tail of the breathing bag have the great disadvantage that they may obstruct the tail of the bag by twisting, resulting in greatly increased pressures in the lungs and serious damage. They may also be cumbersome and make manual ventilation difficult. With the scavenging dish it is necessary to hold the bag precisely over the scavenging dish in order to be efficient and this may not be convenient or comfortable. Consideration was given to installing an escape valve proximal to the breathing bag and this would then have a hood and be scavenged as with the adult system - the tail of the breathing bag would then be closed. In this modification aT-piece has been placed proximal to the breathing bag and a tube leads from the limb of the 'T' to a control valve plugged into an interface mounted on the front of the anaesthetic machine. The interface is led to a dump. Or. J. Inkster at The Hospital for Sick Children, Newcastle-uponTyne, was using a similar system when I visited him. DESCRIPTION
The system has aT-piece connector with standard 15 mm tapers (A, Figure 1) which can be easily incorporated between the expiratory limb and the breathing bag of the
Jackson Rees modification of the Ayres' T -piece system. The gases are exhausted from the system via the side arm of the T -piece (a, Figure 1) and the tail of the bag is closed with some form of clamp (C, Figure 1) which is easily applied and removed, e.g. a paper or gate clip. The side arm of the T -piece (a) is of adequate diameter so that there is minimal resistance to the escape of gases at an 8 litre/ minute gas flow (Figure 2). A lightweight but not easily obstructed tube carries the gases from the T-piece limb (a) to a scavenge valve (B, Figure 1). This valve has a standard scavenge 19 mm taper which fits into a corresponding taper on the interface (0, Figure 1) which is mounted on the front panel of the anaesthetic machine. The valve may be readily interchanged with a tube which is carrying exhaust gases from the hood over the exhaust valve of the circle absorber system. The scavenge valve has a control with four settings (off, 1,2,3) with which to vary the rate of escape of the exhaust gases. This variation allows the system to be used with both spontaneous and manually controlled ventilation. With mechanical ventilation the system is removed and the ventilator is scavenged. The valve is constructed with a safety feature so that when in the 'off position it is not fully closed but will only allow a pressure of 30 cm of water with an 8 litre/ minute gas flow (Figure 2). In position 3 there 30
...
~ o .
Cl):O::
INTERFACE
[lr-TO
~UMP
D
~ (/l
(/l
Cl)
...
c E 20 ......
.-
-
a.. co ~
