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Appropriate suction device in rescue medicine
ORIGINAL CONTRIBUTION suction device
Appropriate Suction Device in Rescue Medicine In rescue medicine, a suction apparatus must function in a variety of environmental conditions. To find an appropriate device for the Swedish Air Force air rescue service the Laerdal suction device 790 000 was selected for further testing according to international standards for aviation safety. Tests showed that vibrations had deleterious effects on the internal construction of the suction device. In addition, an electromagnetic field was generated affecting the navigation, autopilot, and communication systems. We conclude that the suction apparatus and probably other devices as well must be tested for their functioning m adverse environments and their ability to meet international aviation safety regulations. [Dahlgren BE, Nilsson H, Bjom P, Skedevik C: Appropriate suction device in rescue medicine. Ann Emerg Med December 1987;16:1362-1364.]
INTRODUCTION Clearing the mouth, nose, and respiratory tract of secretions or foreign material by suction is a very basic task. In rescue medicine, this often m u s t be carried out at the scene of an accident or during transport. A suction device should function under a variety of environmental conditions, in all types of climates; in wet, m u d d y locations; and in moving vehicles. The Swedish Air Force uses the Boeing Vertol 107 helicopter for air and sea rescue. Field trials and laboratory tests have been performed to provide these helicopters w i t h appropriate medical equipment.Us Selection of a suitable suction device among those available on the Swedish m a r k e t was made in two stages. First, a visual scrutiny of the apparatus and review of the manufacturer's sales literature was made. Parameters such as weight, volume, and reliability were considered. This analysis is s u m m a r i z e d (Table}. The d e c tromechanical suction device (Laerdal 790 000, Laerdal, Stavanger, Norway) was the only i t e m selected for further laboratory testing. The purpose of our study was to see if the Laerdal suction device 790 000 fulfilled the requirements stipulated for aviation equipment safety.*
BE Dahrgren, MD, PhD* H Nilsson, Res Off1 P Bjorn, M Sct C Skedevik, B SclLink6ping, Sweden From the Department of Anaesthesiology, University Hospital, LinkOping University;* and the Aircrew Performance and Function Division, National Defense Research Institution,t LinkOping, Sweden. Received for publication May 12, 1986. Accepted for publication September 26, 1986. Address for reprints: BE Dahlgren, MD, PhD, Department of Anaesthesiology, University Hospital, S-581 85 Link0ping, Sweden.
MATERIALS AND METHODS Temperature Test The performance of the device at different temperatures was tested in a climate chamber at Aircrew Performance and Function division in Link6ping, Sweden. Temperature sensors were placed on the cover and in the interior, which was the core temperature of the apparatus. Function was tested at various temperatures between - 2 0 C and 40 C in steps of 5 C and in simulated sunlight (12,000 w/m2).
Functional Test T h e suction capability was tested by using a standardized mixture* of diagnostic slime and water simulating mucus. The criteria for acceptable suct i o n capacity was to evacuate 500 mL of m u c u s m i x t u r e in 30 seconds through a size 14 catheter. When testing below 0 C the mucus container was kept at: body temperature, 37 C. *The composition of the slime varies between pharmacies and over time. During this study the same composition was used -- 60% slime, 40% tap waten
16:t2 December 1987
Annals of Emergency Medicine
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SUCTION DEVICE Dahlgren et al
TABLE. H o w suction devices were selected for further testing
Running Principle
Example of Advantage
Example of Disadvantage
Example of Hazards
Vacuum created by the vehicle
Simple driving source
Influences the vehicle's braking system. Not applicable in helicopter
Bad braking effect; unreliable driving source
Injector. The driving force of oxygen from a flask
Good suction effect
Injector. The driving force from an aerosol container
Small dimensions
Hazards with pressurized containers. Increased oxygen tension Hazards with pressurized container
Mechanical force driven by hand or foot
Mobile. Good effect/ weight ratio
Electromagnetic driving force from batteries or from electric distribution network
Mobile. Good effect/ weight ratio. Easy to handle
Very oxygen-consuming The driving source has a heavy weight Limited suction effect. Sensitive to cold and freezes very easy A hand or foot is engaged Caretaking of batteries
FIGURE 1. Measured acceleration (Gforce) on a circuit card in the suction d e v i c e w h e n s u b m i t t e d to various vibration frequencdes.
0-
Shock Test During the shock test, the suction a p p a r a t u s was a t t a c h e d f i r m l y to a metal plate that was made to fall repeatedly against a rigid stop, giving 25 G in the X, Y, and Z axes.
Electromagnetic Field Test The device was placed in a shielded room. The influence of induced electromagnetic fields and fields induced by the device could be registered and evaluated w i t h special antennas.
82/1363
Generating electric magnetic field disturbances
Acceleration Gz
Stroke 2 mm, 2 G
Vibration Test A v i b r a t o r was u s e d for t e s t i n g v i b r a t i o n sensitivity. T h e a p p a r a t u s was attached firmly to a m e t a l plate, which vibrated in three perpendicular d i r e c t i o n s - - t h e long axis, X; t h e transverse Y, and the vertical Z. Frequency was swept continuously from 5 to 2,000 Hz w i t h the gravitational force kept at approximately 2 G. The v i b r a t i o n forces were r e g i s t e r e d by sensors attached to different parts of the interior of the apparatus. A t each registered resonance frequency, the apparatus was subjected to an extended v i b r a t i o n test, w i t h a g r a v i t a t i o n a l force of 5 G for 15 m i n u t e s . Functional tests were performed after each test.
Unreliable driving source
8O -
5432Frequency Hz m
I
.
.
.
.
.
.
.
.
10 13,2 20 26,4 40 60 80 100
t
200
'
6()0'
Basic rotor frequency in Boeing Vertol 107
RESULTS Temperature Sensitivity Test T h e L a e r d a l s u c t i o n d e v i c e performed very well in the temperature region above the freezing point, and the functional tests were all acceptable. A t temperatures below freezing, the electrical m o t o r worked, b u t because of clogging by frozen mucus in the catheter, no acceptable tests were registered below - 5 C.
internal circuit card and registered frequencies deleterious to the card and the function of the apparatus. The resonance frequencies were in the region where vibrations from the rotors of helicopter Boeing Vertol 107 are very p r o m i n e n t (basal tone, first and second overtone) (Figure 1). Several internal parts were not fastened firmly enough. Functional tests values were above criteria level after the vibration tests.
Vibration Sensitivity Test A s e n s o r to d e t e c t r e s o n a n c e frequencies was placed on the device's
Annals of Emergency Medicine
Shock Test T h e f u n c t i o n a l tests were accept16:12 December 1987
F I G U R E 2. Registered interference from the electric motor in the suction device at various frequencies. The accepted interference level according to MIL STD 461 is shown.
Field strength level dB uV/m/MHz 7060504030-/
20 t ~
Background noise
/
10 -~
01
.
.
.
.
.
.
100
.
.
150
I
.
Freluency MHz
I
VHF flight communication
able after each shock test in three directions. However, visual inspection confirmed that some of the internal parts needed better support and fixation.
Electromagnetic Field Test Electromagnetic fields did not influence the function of the suction device. T h e electrical m o t o r induced electromagnetic disturbance beyond the acceptable m a x i m u m stipulated by the Swedish Air Force (MIL-STD 461/3). 4 The disturbance occurred in several frequency regions (Figure 2).
DISCUSSION An apparatus can be tested in active clinical use and by laboratory tests. Clinical trials are time consuming, require a sufficient number of cases, and are unlikely to test all possible aspects of function. L a b o r a t o r y s i m u l a t i n g tests lack the clinical aspects, but testing conditions are standardized and comparisons and reproducibility are easier. The tests in this study were of the same type as those required for certification of apparatuses to be used in aircraft of the Swedish Air Force. 4 The test methods had been used earlier in testing compact portable ventilators2, 3
16:12 December 1987
to be used in rescue helicopters. The climate chamber test showed that the s u c t i o n devices had good function above the freezing point. Below freezing, the artificial m u c u s froze in the catheter and inhibited f u n c t i o n . T h i s p r o b l e m c o u l d be avoided if heating facilities were installed, but this would increase volu m e and w e i g h t and r e d u c e portability. In the moderately cold range down to - 5 C, the heat from the rescuer's hand often was enough to reduce the formation of frozen mucus. To avoid functional disturbances, protection of the external tubing is necessary because the plastic becomes very stiff on cooling. Internal tubing should be made of silicon to remain flexible in a broader temperature range. The mixture of diagnostic slime and water had a reasonable resemblance to m u c u s . B e c a u s e t h e v i s c o s i t y of mucus varies, there seemed to be no need for more detailed analysis of the physical characteristics of the artificial mucus. The main criterion was that the same mixture was used and had the same characteristics throughout the study. Both the vibration and shock tests showed that interior parts needed better Support and fastening, although
Annals of Emergency Medicine
the functional tests were acceptable. Had the exposure time to vibration been extended, the apparatus circuit card would have broken. The circuit card is exposed to vibrations as soon as the engines of the vehicle are started. It thus makes no difference whether the apparatus is in use or not. Just being in the vehicle will be enough to jeopardize function. The vibration test also illustrated that when equipment is selected, the environmental characteristics of the vehicle or aircraft m u s t be known. The registered vibration sensitivity in this study was imporant because in the same frequency range this type of aircraft generates strong vibrating forces. This m a y be unimportant in aircraft in w h i c h no vibrations are generated. No sensitivity to electromagnetic fields was noted. The electromagnetic field induced by the suction device, however, could disturb the function of VHF r a d i o c o m m u n i c a t i o n s , navigation, and autopilot systems. CONCLUSION This type of suction device cannot be used on board Boeing Vertol 107 aircraft without modification. The manufacturer modified the device in 1985~ the modified model is called 790 000 E Those who practice rescue medicine s h o u l d be aware of the hazards of using medical devices in the field. REFERENCES 1. Dahlgren BE, Nilsson HG: Reducing the environmental hazards to and by apparatus in rescue medicine. Disaster Medicine (submitted for publication). 2. Dahlgren BE, Engdahi O, Nilsson HG: Portable emergency ventilators. Sensitivity to environment. Acta Anaesthesiol Scand 1981; 25:46-50. 3. Dahlgren BE, Nilsson HG, Peters B, et al: Further studies on portable emergency ventilators. Sensitivity to environment. Acta Anaesthesiol Scand 1985;29:753-757. 4. International aviation safety standards used by the Swedish Air Force: MIL-STD-810 MILSTD-461 not 3 and 462.
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Appropriate Suction Device in Rescue Medicine In rescue medicine, a suction apparatus must function in a variety of environmental conditions. To find an appropriate device for the Swedish Air Force air rescue service the Laerdal suction device 790 000 was selected for further testing according to international standards for aviation safety. Tests showed that vibrations had deleterious effects on the internal construction of the suction device. In addition, an electromagnetic field was generated affecting the navigation, autopilot, and communication systems. We conclude that the suction apparatus and probably other devices as well must be tested for their functioning m adverse environments and their ability to meet international aviation safety regulations. [Dahlgren BE, Nilsson H, Bjom P, Skedevik C: Appropriate suction device in rescue medicine. Ann Emerg Med December 1987;16:1362-1364.]
INTRODUCTION Clearing the mouth, nose, and respiratory tract of secretions or foreign material by suction is a very basic task. In rescue medicine, this often m u s t be carried out at the scene of an accident or during transport. A suction device should function under a variety of environmental conditions, in all types of climates; in wet, m u d d y locations; and in moving vehicles. The Swedish Air Force uses the Boeing Vertol 107 helicopter for air and sea rescue. Field trials and laboratory tests have been performed to provide these helicopters w i t h appropriate medical equipment.Us Selection of a suitable suction device among those available on the Swedish m a r k e t was made in two stages. First, a visual scrutiny of the apparatus and review of the manufacturer's sales literature was made. Parameters such as weight, volume, and reliability were considered. This analysis is s u m m a r i z e d (Table}. The d e c tromechanical suction device (Laerdal 790 000, Laerdal, Stavanger, Norway) was the only i t e m selected for further laboratory testing. The purpose of our study was to see if the Laerdal suction device 790 000 fulfilled the requirements stipulated for aviation equipment safety.*
BE Dahrgren, MD, PhD* H Nilsson, Res Off1 P Bjorn, M Sct C Skedevik, B SclLink6ping, Sweden From the Department of Anaesthesiology, University Hospital, LinkOping University;* and the Aircrew Performance and Function Division, National Defense Research Institution,t LinkOping, Sweden. Received for publication May 12, 1986. Accepted for publication September 26, 1986. Address for reprints: BE Dahlgren, MD, PhD, Department of Anaesthesiology, University Hospital, S-581 85 Link0ping, Sweden.
MATERIALS AND METHODS Temperature Test The performance of the device at different temperatures was tested in a climate chamber at Aircrew Performance and Function division in Link6ping, Sweden. Temperature sensors were placed on the cover and in the interior, which was the core temperature of the apparatus. Function was tested at various temperatures between - 2 0 C and 40 C in steps of 5 C and in simulated sunlight (12,000 w/m2).
Functional Test T h e suction capability was tested by using a standardized mixture* of diagnostic slime and water simulating mucus. The criteria for acceptable suct i o n capacity was to evacuate 500 mL of m u c u s m i x t u r e in 30 seconds through a size 14 catheter. When testing below 0 C the mucus container was kept at: body temperature, 37 C. *The composition of the slime varies between pharmacies and over time. During this study the same composition was used -- 60% slime, 40% tap waten
16:t2 December 1987
Annals of Emergency Medicine
1362/81
SUCTION DEVICE Dahlgren et al
TABLE. H o w suction devices were selected for further testing
Running Principle
Example of Advantage
Example of Disadvantage
Example of Hazards
Vacuum created by the vehicle
Simple driving source
Influences the vehicle's braking system. Not applicable in helicopter
Bad braking effect; unreliable driving source
Injector. The driving force of oxygen from a flask
Good suction effect
Injector. The driving force from an aerosol container
Small dimensions
Hazards with pressurized containers. Increased oxygen tension Hazards with pressurized container
Mechanical force driven by hand or foot
Mobile. Good effect/ weight ratio
Electromagnetic driving force from batteries or from electric distribution network
Mobile. Good effect/ weight ratio. Easy to handle
Very oxygen-consuming The driving source has a heavy weight Limited suction effect. Sensitive to cold and freezes very easy A hand or foot is engaged Caretaking of batteries
FIGURE 1. Measured acceleration (Gforce) on a circuit card in the suction d e v i c e w h e n s u b m i t t e d to various vibration frequencdes.
0-
Shock Test During the shock test, the suction a p p a r a t u s was a t t a c h e d f i r m l y to a metal plate that was made to fall repeatedly against a rigid stop, giving 25 G in the X, Y, and Z axes.
Electromagnetic Field Test The device was placed in a shielded room. The influence of induced electromagnetic fields and fields induced by the device could be registered and evaluated w i t h special antennas.
82/1363
Generating electric magnetic field disturbances
Acceleration Gz
Stroke 2 mm, 2 G
Vibration Test A v i b r a t o r was u s e d for t e s t i n g v i b r a t i o n sensitivity. T h e a p p a r a t u s was attached firmly to a m e t a l plate, which vibrated in three perpendicular d i r e c t i o n s - - t h e long axis, X; t h e transverse Y, and the vertical Z. Frequency was swept continuously from 5 to 2,000 Hz w i t h the gravitational force kept at approximately 2 G. The v i b r a t i o n forces were r e g i s t e r e d by sensors attached to different parts of the interior of the apparatus. A t each registered resonance frequency, the apparatus was subjected to an extended v i b r a t i o n test, w i t h a g r a v i t a t i o n a l force of 5 G for 15 m i n u t e s . Functional tests were performed after each test.
Unreliable driving source
8O -
5432Frequency Hz m
I
.
.
.
.
.
.
.
.
10 13,2 20 26,4 40 60 80 100
t
200
'
6()0'
Basic rotor frequency in Boeing Vertol 107
RESULTS Temperature Sensitivity Test T h e L a e r d a l s u c t i o n d e v i c e performed very well in the temperature region above the freezing point, and the functional tests were all acceptable. A t temperatures below freezing, the electrical m o t o r worked, b u t because of clogging by frozen mucus in the catheter, no acceptable tests were registered below - 5 C.
internal circuit card and registered frequencies deleterious to the card and the function of the apparatus. The resonance frequencies were in the region where vibrations from the rotors of helicopter Boeing Vertol 107 are very p r o m i n e n t (basal tone, first and second overtone) (Figure 1). Several internal parts were not fastened firmly enough. Functional tests values were above criteria level after the vibration tests.
Vibration Sensitivity Test A s e n s o r to d e t e c t r e s o n a n c e frequencies was placed on the device's
Annals of Emergency Medicine
Shock Test T h e f u n c t i o n a l tests were accept16:12 December 1987
F I G U R E 2. Registered interference from the electric motor in the suction device at various frequencies. The accepted interference level according to MIL STD 461 is shown.
Field strength level dB uV/m/MHz 7060504030-/
20 t ~
Background noise
/
10 -~
01
.
.
.
.
.
.
100
.
.
150
I
.
Freluency MHz
I
VHF flight communication
able after each shock test in three directions. However, visual inspection confirmed that some of the internal parts needed better support and fixation.
Electromagnetic Field Test Electromagnetic fields did not influence the function of the suction device. T h e electrical m o t o r induced electromagnetic disturbance beyond the acceptable m a x i m u m stipulated by the Swedish Air Force (MIL-STD 461/3). 4 The disturbance occurred in several frequency regions (Figure 2).
DISCUSSION An apparatus can be tested in active clinical use and by laboratory tests. Clinical trials are time consuming, require a sufficient number of cases, and are unlikely to test all possible aspects of function. L a b o r a t o r y s i m u l a t i n g tests lack the clinical aspects, but testing conditions are standardized and comparisons and reproducibility are easier. The tests in this study were of the same type as those required for certification of apparatuses to be used in aircraft of the Swedish Air Force. 4 The test methods had been used earlier in testing compact portable ventilators2, 3
16:12 December 1987
to be used in rescue helicopters. The climate chamber test showed that the s u c t i o n devices had good function above the freezing point. Below freezing, the artificial m u c u s froze in the catheter and inhibited f u n c t i o n . T h i s p r o b l e m c o u l d be avoided if heating facilities were installed, but this would increase volu m e and w e i g h t and r e d u c e portability. In the moderately cold range down to - 5 C, the heat from the rescuer's hand often was enough to reduce the formation of frozen mucus. To avoid functional disturbances, protection of the external tubing is necessary because the plastic becomes very stiff on cooling. Internal tubing should be made of silicon to remain flexible in a broader temperature range. The mixture of diagnostic slime and water had a reasonable resemblance to m u c u s . B e c a u s e t h e v i s c o s i t y of mucus varies, there seemed to be no need for more detailed analysis of the physical characteristics of the artificial mucus. The main criterion was that the same mixture was used and had the same characteristics throughout the study. Both the vibration and shock tests showed that interior parts needed better Support and fastening, although
Annals of Emergency Medicine
the functional tests were acceptable. Had the exposure time to vibration been extended, the apparatus circuit card would have broken. The circuit card is exposed to vibrations as soon as the engines of the vehicle are started. It thus makes no difference whether the apparatus is in use or not. Just being in the vehicle will be enough to jeopardize function. The vibration test also illustrated that when equipment is selected, the environmental characteristics of the vehicle or aircraft m u s t be known. The registered vibration sensitivity in this study was imporant because in the same frequency range this type of aircraft generates strong vibrating forces. This m a y be unimportant in aircraft in w h i c h no vibrations are generated. No sensitivity to electromagnetic fields was noted. The electromagnetic field induced by the suction device, however, could disturb the function of VHF r a d i o c o m m u n i c a t i o n s , navigation, and autopilot systems. CONCLUSION This type of suction device cannot be used on board Boeing Vertol 107 aircraft without modification. The manufacturer modified the device in 1985~ the modified model is called 790 000 E Those who practice rescue medicine s h o u l d be aware of the hazards of using medical devices in the field. REFERENCES 1. Dahlgren BE, Nilsson HG: Reducing the environmental hazards to and by apparatus in rescue medicine. Disaster Medicine (submitted for publication). 2. Dahlgren BE, Engdahi O, Nilsson HG: Portable emergency ventilators. Sensitivity to environment. Acta Anaesthesiol Scand 1981; 25:46-50. 3. Dahlgren BE, Nilsson HG, Peters B, et al: Further studies on portable emergency ventilators. Sensitivity to environment. Acta Anaesthesiol Scand 1985;29:753-757. 4. International aviation safety standards used by the Swedish Air Force: MIL-STD-810 MILSTD-461 not 3 and 462.
1364/83