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Comparative evaluation of three end-tidal CO2 monitors used during air medical transport
ORIGINAL CONTRIBUTION
Comparative Evaluation of Three End-Tidal 602 Monitors Used During Air
Medical Transport • Catherine Peterson, RRT; Randy Budd, RRT; Kendra Balazs, RN, BSN, CCRN Introduction AN OUTLYING FACILITY REQUESTS THE
transport of a 28-year-old male patient involved in a serious motor vehicle accident. The patient has been diagnosed with head injuries. He is intubated, mechanically ventilated, and arterial blood gases (ABG) have been drawn. The question arises: During transport, how can the flight respiratory therapist and flight nurse evaluate effective mechanical ventilation? Presently, the flight respiratory therapist uses exhaled tidal volume, chest excursion, breath sounds, oxygen saturation, and clinical assessment of the patient to determine effective mechanical ventilation. Samaritan AirEvac's Flight Respiratory Therapy Department investigated using end-tidal carbon dioxide (ETCO2) monitors, a process also known as capnography, as another method of evaluating mechanical ventilation during transport. The purpose of this investigation was to The authors above worlC at Samaritan
AirEvac in Phoenix, Ariz. Catherine Peterson is the supervisor of the flight respiratory therapists, Randy Budd is a flight respiratory therapist, and Kendra Balazs is the director of Medical Flight Services.
compare ETCO2 monitors to determine which model would be most suitable for the stresses of flight. Methods Several manufacturers were invited to participate in the capnograph evaluation process. Three companies, Ohmeda (Louisville, Colo.), Biochem International Inc. (Waukensha, Wis.), and Novametrix Medical Inc. (Wallingford, Conn.), loaned their capnographs for the study. The length of the loan for each monitor ranged from 1 to 2 months. With the varying length of monitor loans, the entire study lasted approximately 6 months. The specific monitors used were the Ohmeda 4700, the Biochem 9090, and the Novametrix 1260. All flight respiratory therapists were instructed on the use of each capnograph, and the monitors were used according to the manufacturers' procedures on ETCO2 monitoring. A questionnaire (Table 1) was developed to evaluate the various ETCO2 monitors. The criteria to determine the capnograph function in-flight included warm-up time, weight, size, battery life, and readability of the digital readout and graphical waveform. Performance options for each criteria were devel-
The Journal of Air Medical Transport ° February 1992
oped by the investigators based on their past experience in the use of electronic monitoring equipment during air transport. Air medical personnel were instructed to choose the performance option that best described their experience with each capnograph they tested. The ETCO2 monitors were taken on transports in Cessna Conquest 441 pressurized fixed-wing aircraft. When no patients were on the aircraft, the monitors were used on air medical personnel to evaluate the capnograph's function. During patient transport, the monitors were used on ventilated patients, although the capnograph information was used only for the purpose of the study and not to treat the patients. The questionnaires were completed by the flight respiratory therapist, the flight nurse, or both, and the results were then compiled by the investigators.
Results The ETCO2 monitors were loaned to AirEvac for a limited time, resulting in only 43 questionnaires being completed. The questionnaires were reviewed and the results tabulated for each criteria category. The 43 questionnaires were separated 7
The two critical criteria, monitor readout during normal flight vibration and turbulence, are shown in categories 6 and 7. The Ohmeda and the Novametrix graphical waveform and digital readout functioned continuously over 89% of the time. Category 8, accuracy of the respiratory rate, was evaluated b y com-paring the actual patient respiratory rate to the m o n i t o r readout; the Novametrix was accurate over 80% of the time. C a t e g o r y 9 evaluated the time needed for the monitor to stabilize before a reading could be obtained; all three monitors obtained a reading in less than 5 minutes 100% of the time. Category 10 evaluated the ability to adjust the line of sight and readability of the numerical values of the monitors during different times of the day and night. The responses for c a t e g o r y 10 showed the O h m e d a and Novametrix performed desirably over 90% of the time.
Figure 1 ETC02 Monitor C o m p a r i s o n 100
80
60
40
20
3
10hmeda Category 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
4
5
~
7
8
9
10
Novametrix
Bars based on percentage of "yes" answers. Most Desirable Option
Warm-up time Weight Size Battery life Placement in aircraft Monitor readout during flight vibration Monitor readout during turbulence Respiratory rate accurate Stabilization time Line of sight
a c c o r d i n g to the t h r e e d i f f e r e n t manufacturers (Figure 1). The percentages on the bar graph r e p r e s e n t the n u m b e r of d e s i r e d r e s p o n s e s selected by the evaluators. Since t h e m o s t d e s i r a b l e options determine the practicality of each capnograph in air transport, only the m o s t d e s i r a b l e o p t i o n s were reported on the bar graph. For example, the category of warm-up time had these options for the evaluator to choose from: (1) greater than 20 minutes, (2) 15 to 20 minutes, and ( 3 ) l e s s than 15 minutes. The most desirable option 6f less than 15 minutes appears on the bar graph. The results of the survey are as follows: In c a t e g o r y 1, m o n i t o r warm-up time, the Ohmeda and the Biochem warmed up in less than 15 8
6
Legend Biochem
Less than 15 minutes Very light Small Over 1 hour Easy to secure Readout continuous
Discussion
Readout continuous 100% match
Less than 5 minutes Easy to read
minutes 100% of the time. In categories 2 and 3, weight and size of the monitors were evaluated. The options given to the evaluator were subjective; for example, the terms "very light" and "small" were used. The overall responses indicated that the monitors were too large and too heavy. In category 4, battery life, none of the three monitors had a battery life over 1 hour. Category 5 identified the flight ,personnels' ability to easily place and secure the monitor in the aircraft, The monitors were secured inside the patient platform box located in the fixed-wing aircraft. The e v a l u a t o r s i n d i c a t e d that t h e Ohmeda and the Biochem were easy to secure over 88% of the time.
D u e to the annual n u m b e r of a n e s t h e t i c or v e n t i l a t o r - r e l a t e d d e a t h s and incidents of c e r e b r a l damage related to hypoxia, many personnel in hospital areas such as anesthesia, neonatal intensive care, and adult critical care now routinely use ETC02 monitors in the care and treatment of the mechanically ventilated patient. 1;2 End-tidal CO2 monitoring is currently used to verify endotracheal tube (ETT) placement, determine appropriate mechanical ventilator management, monitor ventilator circuit integrity, and d e t e r m i n e the effectiveness of c a r d i o p u l m o n a r y r e s u s c i t a t i o n (CPR)3,4 A l t h o u g h ETCO2 monitor use in the hospital setting has been well-documented, little literature on ETCOe monitor use in the air medical transport environment was found. 2-4 End-tidal CO2 m o n i t o r i n g is a non-invasive method of monitoring concentration in expired respiratory gases during each respiratorycycle. Capnography can provide instantaneous information on metabolism,
The Journal of Air Medical Transport ° February 1992
cause ETT displacement and disruption of the ventilator circuit. Lack of arterial blood gas (ABG) analysis ETCO2 Monitor Evaluation Survey during transport makes it difficult to e v a l u a t e t h e e f f e c t i v e n e s s of Please complete this evaluation form by circling the comment that best mechanical ventilation. The capnoreflects the performance and operation of each project question (1 being the graph could be used as an adjunct in least efficient and 3 being the most efficient). Your answers to these quest h e c o n t i n u o u s a s s e s s m e n t of tions will help us evaluate the capnographs. Thank you for your participation. mechanically ventilated patients during transport. 1 2 3 The electronic equipment used in the air medical environment must Warm-up time Greater than 15-20 Less than be able to function in a variety of 20 minutes minutes 15 minutes adverse conditions, such as continuous vibration, varying levels of outWeight Very heavy Moderate Very light weight side illumination (making it difficult to read t h e s c r e e n s ) , altitude changes, and constant movement in Size Very large Large to Small moderate and out of the aircraft. Because of these adverse conditions, it is important to verify that the piece of equipBattery life Has none Under 1 hour Over 1 hour ment can be used appropriately in the aircraft. Placement in No place to Hard to Easy to aircraft secure secure secure Some of the criteria were more critical to the function of the monitors in transport than others. For Monitor reading Would not Worked Readout with flight work at all intermittently continues example, monitor r e a d o u t during vibration (artifact) flight vibration and turbulence, ability to adjust the line of sight of the If turbulence Would not Worked Readout screen during different lighting situoccurs work at all intermittently continues ations, and the accuracy of the respiratory rate were considered vital to Was RR accurate? Off by more Off by less 100% match using the monitor in the aircraft. than 6 BPM than 6 BPM Warm-up time and stabilization time before a reading could be taken are Stabilization time Over 10 5 to 10 Less than 5 not as critical; however, they would before reading minutes minutes minutes impact the time available for using obtained the monitor during transport. Battery life would be a critical criLine of sight Hard to read Easy to read terion if the aircraft had no invertor or the capnograph was used during long ambulance transports to and Brand Name Weight_ Size from the airport. If the capnograph is used only during flight in a plane with an invertor, then a long battery Recommended Calibrations life may not be critical. ETCO2 monitors that are light, Evaluator's Name small, and easy to place would be attractive, but these characteristics are not essential to their use in the ventilation, and ventilator circuit The air medical transport envi- aircraft. However, equipment that is integrity. The monitor provides a r o n m e n t l e n d s itself to potential small and easy to place is more readgraphical waveform ~{nd a digital complications in the transport of the ily used when space in the aircraft is readout. The graphical waveform is ventilated patient. T h e aircraft's limited. Although this study did not invesa continuous readout of the patient's high noise levels can make it diffirespiratory cycle, whereas the digi- cult to a d e q u a t e l y a s s e s s b r e a t h tigate the use of ETCO2 monitors in tal readout provides the numerical s o u n d s . T h e m o v e m e n t of t h e rotor-wing aircraft, the results could value of the ETCO2. patient in and out of the aircraft can be applied to rotor-wing use. The Table 1
The Journal of Air Medical Transport • February 1992
9
limitations for rotor-wing aircraft would probably be the large size and weight of the monitors. Capnographs may be useful for patients on ventilators during long distance transport in large rotorwing aircraft. Some limitations of this study are the low numbers of completed questionnaires per capnograph and the subjective criteria determined by the investigators.
established during flight. Light weight, small size and extended battery life appear to be the criteria most lacking in these three capnographs reviewed in this study. This study demonstrates the compatibility of three capnographs with the aircraft environment. Manufacturers will hopefully continue to develop ETCO2 monitors to meet the space and weight needs of flight personnel in the difficult conditions of the air medical enviroment. •
Summary
The purpose of this investigation on ETCO2 monitoring was to determine if the monitors would function effectively in the aircraft. When compared in a cumulative manner, little difference between the three monitors was noted. The ETCO2 monitor appears to function in the fixed-wing aircraft when transporting critically ill, mechanically ventilated patients. Although this study does not address the accuracy of the ETCO2 monitor during changes in altitude, a base-line reading can be
References 1. Weingarten M: Anesthetic and ventilator mishaps: Prevention and detection. Crit Care Med 1986; 14:1084-86. 2. Guggenberger H, Lenz G, Federle R: Early detection of inadvertent oesophageal intubation: Pulse oximetry vs. capnography. Acta Anaesthesiol Scand 1989; 33:112-5. 3. Lillie PE, Roberts JG: Carbon dioxide monitoring. Anaesth Intens Care 1988; 16:4144. 4. Garnett AR, Ornato JP, Gonzales ER, et al: End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. JAMA 1987; 257:512-15.
Upcoming Feature Schedule - March HAl Convention Issue
Weather-reporting systems; 1991 transport summary - April Advances in C l i n i c a l
Care
Airframe/Biomedical interface; medical crew salaries/duties Mid-Year
- May Conference
Issue
Air transport economics; transport charge survey - June Operator
-
Negotiations
Choosing an aircraft operator
T h e National E M S Pilots Association
L_Z__ 10
proud to offer the pamphlet, I.Z Preparing • Landing Zone. This pamphlet has become the standard for providing Information and guidance to user agencies for conducting safe operations around helicopters and establishing safe landing sites. The pamphlet addresses such Issues as: Selecting an onscene I.Z, wind direction and touchdown area, personnel safety and night landing, ground guide, assisting the crew, and general helicopter safety rules. Designed as a teaching aid, the pamphlet Is Ideal for conducting classes for user agencies. Space is provided on the back cover for individual hospital Iogos, dispatch phone numbers, etc. For pricing and orders contact: The NaUonal EMS Pilots Association P.O. Box 8272 Rapid City, South Dakota 57709 (605) 341-0273 Is
The Journal of Air Medical Transport • February 1992
Comparative Evaluation of Three End-Tidal 602 Monitors Used During Air
Medical Transport • Catherine Peterson, RRT; Randy Budd, RRT; Kendra Balazs, RN, BSN, CCRN Introduction AN OUTLYING FACILITY REQUESTS THE
transport of a 28-year-old male patient involved in a serious motor vehicle accident. The patient has been diagnosed with head injuries. He is intubated, mechanically ventilated, and arterial blood gases (ABG) have been drawn. The question arises: During transport, how can the flight respiratory therapist and flight nurse evaluate effective mechanical ventilation? Presently, the flight respiratory therapist uses exhaled tidal volume, chest excursion, breath sounds, oxygen saturation, and clinical assessment of the patient to determine effective mechanical ventilation. Samaritan AirEvac's Flight Respiratory Therapy Department investigated using end-tidal carbon dioxide (ETCO2) monitors, a process also known as capnography, as another method of evaluating mechanical ventilation during transport. The purpose of this investigation was to The authors above worlC at Samaritan
AirEvac in Phoenix, Ariz. Catherine Peterson is the supervisor of the flight respiratory therapists, Randy Budd is a flight respiratory therapist, and Kendra Balazs is the director of Medical Flight Services.
compare ETCO2 monitors to determine which model would be most suitable for the stresses of flight. Methods Several manufacturers were invited to participate in the capnograph evaluation process. Three companies, Ohmeda (Louisville, Colo.), Biochem International Inc. (Waukensha, Wis.), and Novametrix Medical Inc. (Wallingford, Conn.), loaned their capnographs for the study. The length of the loan for each monitor ranged from 1 to 2 months. With the varying length of monitor loans, the entire study lasted approximately 6 months. The specific monitors used were the Ohmeda 4700, the Biochem 9090, and the Novametrix 1260. All flight respiratory therapists were instructed on the use of each capnograph, and the monitors were used according to the manufacturers' procedures on ETCO2 monitoring. A questionnaire (Table 1) was developed to evaluate the various ETCO2 monitors. The criteria to determine the capnograph function in-flight included warm-up time, weight, size, battery life, and readability of the digital readout and graphical waveform. Performance options for each criteria were devel-
The Journal of Air Medical Transport ° February 1992
oped by the investigators based on their past experience in the use of electronic monitoring equipment during air transport. Air medical personnel were instructed to choose the performance option that best described their experience with each capnograph they tested. The ETCO2 monitors were taken on transports in Cessna Conquest 441 pressurized fixed-wing aircraft. When no patients were on the aircraft, the monitors were used on air medical personnel to evaluate the capnograph's function. During patient transport, the monitors were used on ventilated patients, although the capnograph information was used only for the purpose of the study and not to treat the patients. The questionnaires were completed by the flight respiratory therapist, the flight nurse, or both, and the results were then compiled by the investigators.
Results The ETCO2 monitors were loaned to AirEvac for a limited time, resulting in only 43 questionnaires being completed. The questionnaires were reviewed and the results tabulated for each criteria category. The 43 questionnaires were separated 7
The two critical criteria, monitor readout during normal flight vibration and turbulence, are shown in categories 6 and 7. The Ohmeda and the Novametrix graphical waveform and digital readout functioned continuously over 89% of the time. Category 8, accuracy of the respiratory rate, was evaluated b y com-paring the actual patient respiratory rate to the m o n i t o r readout; the Novametrix was accurate over 80% of the time. C a t e g o r y 9 evaluated the time needed for the monitor to stabilize before a reading could be obtained; all three monitors obtained a reading in less than 5 minutes 100% of the time. Category 10 evaluated the ability to adjust the line of sight and readability of the numerical values of the monitors during different times of the day and night. The responses for c a t e g o r y 10 showed the O h m e d a and Novametrix performed desirably over 90% of the time.
Figure 1 ETC02 Monitor C o m p a r i s o n 100
80
60
40
20
3
10hmeda Category 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
4
5
~
7
8
9
10
Novametrix
Bars based on percentage of "yes" answers. Most Desirable Option
Warm-up time Weight Size Battery life Placement in aircraft Monitor readout during flight vibration Monitor readout during turbulence Respiratory rate accurate Stabilization time Line of sight
a c c o r d i n g to the t h r e e d i f f e r e n t manufacturers (Figure 1). The percentages on the bar graph r e p r e s e n t the n u m b e r of d e s i r e d r e s p o n s e s selected by the evaluators. Since t h e m o s t d e s i r a b l e options determine the practicality of each capnograph in air transport, only the m o s t d e s i r a b l e o p t i o n s were reported on the bar graph. For example, the category of warm-up time had these options for the evaluator to choose from: (1) greater than 20 minutes, (2) 15 to 20 minutes, and ( 3 ) l e s s than 15 minutes. The most desirable option 6f less than 15 minutes appears on the bar graph. The results of the survey are as follows: In c a t e g o r y 1, m o n i t o r warm-up time, the Ohmeda and the Biochem warmed up in less than 15 8
6
Legend Biochem
Less than 15 minutes Very light Small Over 1 hour Easy to secure Readout continuous
Discussion
Readout continuous 100% match
Less than 5 minutes Easy to read
minutes 100% of the time. In categories 2 and 3, weight and size of the monitors were evaluated. The options given to the evaluator were subjective; for example, the terms "very light" and "small" were used. The overall responses indicated that the monitors were too large and too heavy. In category 4, battery life, none of the three monitors had a battery life over 1 hour. Category 5 identified the flight ,personnels' ability to easily place and secure the monitor in the aircraft, The monitors were secured inside the patient platform box located in the fixed-wing aircraft. The e v a l u a t o r s i n d i c a t e d that t h e Ohmeda and the Biochem were easy to secure over 88% of the time.
D u e to the annual n u m b e r of a n e s t h e t i c or v e n t i l a t o r - r e l a t e d d e a t h s and incidents of c e r e b r a l damage related to hypoxia, many personnel in hospital areas such as anesthesia, neonatal intensive care, and adult critical care now routinely use ETC02 monitors in the care and treatment of the mechanically ventilated patient. 1;2 End-tidal CO2 monitoring is currently used to verify endotracheal tube (ETT) placement, determine appropriate mechanical ventilator management, monitor ventilator circuit integrity, and d e t e r m i n e the effectiveness of c a r d i o p u l m o n a r y r e s u s c i t a t i o n (CPR)3,4 A l t h o u g h ETCO2 monitor use in the hospital setting has been well-documented, little literature on ETCOe monitor use in the air medical transport environment was found. 2-4 End-tidal CO2 m o n i t o r i n g is a non-invasive method of monitoring concentration in expired respiratory gases during each respiratorycycle. Capnography can provide instantaneous information on metabolism,
The Journal of Air Medical Transport ° February 1992
cause ETT displacement and disruption of the ventilator circuit. Lack of arterial blood gas (ABG) analysis ETCO2 Monitor Evaluation Survey during transport makes it difficult to e v a l u a t e t h e e f f e c t i v e n e s s of Please complete this evaluation form by circling the comment that best mechanical ventilation. The capnoreflects the performance and operation of each project question (1 being the graph could be used as an adjunct in least efficient and 3 being the most efficient). Your answers to these quest h e c o n t i n u o u s a s s e s s m e n t of tions will help us evaluate the capnographs. Thank you for your participation. mechanically ventilated patients during transport. 1 2 3 The electronic equipment used in the air medical environment must Warm-up time Greater than 15-20 Less than be able to function in a variety of 20 minutes minutes 15 minutes adverse conditions, such as continuous vibration, varying levels of outWeight Very heavy Moderate Very light weight side illumination (making it difficult to read t h e s c r e e n s ) , altitude changes, and constant movement in Size Very large Large to Small moderate and out of the aircraft. Because of these adverse conditions, it is important to verify that the piece of equipBattery life Has none Under 1 hour Over 1 hour ment can be used appropriately in the aircraft. Placement in No place to Hard to Easy to aircraft secure secure secure Some of the criteria were more critical to the function of the monitors in transport than others. For Monitor reading Would not Worked Readout with flight work at all intermittently continues example, monitor r e a d o u t during vibration (artifact) flight vibration and turbulence, ability to adjust the line of sight of the If turbulence Would not Worked Readout screen during different lighting situoccurs work at all intermittently continues ations, and the accuracy of the respiratory rate were considered vital to Was RR accurate? Off by more Off by less 100% match using the monitor in the aircraft. than 6 BPM than 6 BPM Warm-up time and stabilization time before a reading could be taken are Stabilization time Over 10 5 to 10 Less than 5 not as critical; however, they would before reading minutes minutes minutes impact the time available for using obtained the monitor during transport. Battery life would be a critical criLine of sight Hard to read Easy to read terion if the aircraft had no invertor or the capnograph was used during long ambulance transports to and Brand Name Weight_ Size from the airport. If the capnograph is used only during flight in a plane with an invertor, then a long battery Recommended Calibrations life may not be critical. ETCO2 monitors that are light, Evaluator's Name small, and easy to place would be attractive, but these characteristics are not essential to their use in the ventilation, and ventilator circuit The air medical transport envi- aircraft. However, equipment that is integrity. The monitor provides a r o n m e n t l e n d s itself to potential small and easy to place is more readgraphical waveform ~{nd a digital complications in the transport of the ily used when space in the aircraft is readout. The graphical waveform is ventilated patient. T h e aircraft's limited. Although this study did not invesa continuous readout of the patient's high noise levels can make it diffirespiratory cycle, whereas the digi- cult to a d e q u a t e l y a s s e s s b r e a t h tigate the use of ETCO2 monitors in tal readout provides the numerical s o u n d s . T h e m o v e m e n t of t h e rotor-wing aircraft, the results could value of the ETCO2. patient in and out of the aircraft can be applied to rotor-wing use. The Table 1
The Journal of Air Medical Transport • February 1992
9
limitations for rotor-wing aircraft would probably be the large size and weight of the monitors. Capnographs may be useful for patients on ventilators during long distance transport in large rotorwing aircraft. Some limitations of this study are the low numbers of completed questionnaires per capnograph and the subjective criteria determined by the investigators.
established during flight. Light weight, small size and extended battery life appear to be the criteria most lacking in these three capnographs reviewed in this study. This study demonstrates the compatibility of three capnographs with the aircraft environment. Manufacturers will hopefully continue to develop ETCO2 monitors to meet the space and weight needs of flight personnel in the difficult conditions of the air medical enviroment. •
Summary
The purpose of this investigation on ETCO2 monitoring was to determine if the monitors would function effectively in the aircraft. When compared in a cumulative manner, little difference between the three monitors was noted. The ETCO2 monitor appears to function in the fixed-wing aircraft when transporting critically ill, mechanically ventilated patients. Although this study does not address the accuracy of the ETCO2 monitor during changes in altitude, a base-line reading can be
References 1. Weingarten M: Anesthetic and ventilator mishaps: Prevention and detection. Crit Care Med 1986; 14:1084-86. 2. Guggenberger H, Lenz G, Federle R: Early detection of inadvertent oesophageal intubation: Pulse oximetry vs. capnography. Acta Anaesthesiol Scand 1989; 33:112-5. 3. Lillie PE, Roberts JG: Carbon dioxide monitoring. Anaesth Intens Care 1988; 16:4144. 4. Garnett AR, Ornato JP, Gonzales ER, et al: End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. JAMA 1987; 257:512-15.
Upcoming Feature Schedule - March HAl Convention Issue
Weather-reporting systems; 1991 transport summary - April Advances in C l i n i c a l
Care
Airframe/Biomedical interface; medical crew salaries/duties Mid-Year
- May Conference
Issue
Air transport economics; transport charge survey - June Operator
-
Negotiations
Choosing an aircraft operator
T h e National E M S Pilots Association
L_Z__ 10
proud to offer the pamphlet, I.Z Preparing • Landing Zone. This pamphlet has become the standard for providing Information and guidance to user agencies for conducting safe operations around helicopters and establishing safe landing sites. The pamphlet addresses such Issues as: Selecting an onscene I.Z, wind direction and touchdown area, personnel safety and night landing, ground guide, assisting the crew, and general helicopter safety rules. Designed as a teaching aid, the pamphlet Is Ideal for conducting classes for user agencies. Space is provided on the back cover for individual hospital Iogos, dispatch phone numbers, etc. For pricing and orders contact: The NaUonal EMS Pilots Association P.O. Box 8272 Rapid City, South Dakota 57709 (605) 341-0273 Is
The Journal of Air Medical Transport • February 1992