VII. SUMMARY.

Regions.iczation of specialized perinatal care is a fully viable and progres—
sing concept, The development of level III care facilities bas resulted in a
significant reduction in perinatal morbidity and mortality. Early diagnosis and
delivery of the HRPW at a level ITi facility guarantees the highest probability
of a successful outcome for both mother and infant. The technology of early,
precrisis diagnosis of risk in a pregnant woman and/or her fetus at leyel I care
is an area in which major advances are needed. Any advance in early diagnosis
should have a major beneficisi impact on morbidity and mortality because s:fe,
unhurried transpurt to a level III facility would be enabled. As soon as high
risk is detected in the mother, fetus, or neonate, then rapid air transport
technology assumes a role of major importance. The medical transport team is
the most important component of the transport service. The training of these
transport personnel should inciude not only the pertinent aspects of Obstetrics,
Gynecology, Neonatology, and Anesthesiology, but also the related aspects of
Aviation Medicine, Physiology, and Safety. These aviation aspects of training
are currently not covered as extensively as they should be. The technology of
preflight stabilization and preparation of the HRPW and HRN at the referral
hospital is another area in which methodological and/or equipment improvements
could shorten transport time and enhance the outcome. Another sajor component
of the transport system is the pilot and his aircraft. Besides appropriate
aviation aspects, the pilot's training should include relevant medical, phys-
iological, and equipment aspects of perinatal air transport. With respect to
the aircraft, there is universal agreement that exclusive use of large, muiti-
engine, fixed-wing, all-weather types would prevent many of the otherwise adverse
potentials of the airborne environment. Rapid door-to-door transport is the
helicopter's only major virtue. A third major component of the transport system
is the equipment and technology of the airborne environment. Because maternal
transport has developed more recently than neonatal transport, in-flight equip-
ment and methods for life support and monitoring functions are not yet as
developed as those of the ueonate. With the exception of Doppler sensing of
heart action, fetal monitoring during transport is nonexistent. Recent develop-
ments in the technology of transport isolettes have been a major factor in improv-
ing neonatal survivability. Although many significant advances have been made in
the neonatal life support and monitoring systems, many more are possible and
highly desirable. An improved linkage between the neonate's body temperature
and servocontrel of the isolette's thermal system would be highly desirable.
In-flight noninvasive monitoring of neonatal arterial pH and Paco)» along with-
the already available tcPag,, could provide a formidable defense “sainst exacer~
bation of hypoxemia and/or acidosis.

16


environment and its life-supporting functione. This capability has to be maintained
during transport of the HRN. ideal specifications for transport isolettes have
been detailed elsewhere (35,63,69}. The most important specifications provide for
an NTE, humidified oxygenation and veatilation of the patient, visualization and
accessibility of the patient, and monitorin, of both the neonate's vital functions
and the systems which supply life support. All isolette functions are seif-
contained, and either self~powered (2-h battery pack), or capable of converted

use cf surface or air vehicle power sources. Size, weight, and maximum portability
are also important consi.erations. The newest generation of isolettes contain
several that are considered quite adequate by our conferees.

C. Indications for Neonatal Transport. Several publications (10,13,31,33,54,
55,62,67,69) contain detailed indications for emergency transport of the HRN. RDS,
which causes respiratory failure, accounts for about 40 to 50 percent of all HRN
transpects (10,13,20,62}. RDS is primarily associated with premature birth and/
or low birth weight (2). Other important causes of respiratory failure are aspira-
tion syndrome, pneumonia, apnea, birth asphyxia, pneumothorax, and pneumomediastinum.
All forms of respiratory failure account for a total of about 75 percent of all HRN
transports (33). Other important indications for transport include congenital
disease and abnormalities, sepsis, CNS abnormalities, hemorrhage, and blood dys-
erasias (10,13,64,67). The presence of one or more of these conditions usually
defines the HRN. In the presence of any of these conditions, mortality risk is
increased proportionally by the degree of prematurity and/er low birth weight (8,
38,62).

The CD center for a neonatal air transport service is usually located in
the intensive care section of a Pediatrics Department. The neonatal transport
team consists primarily of Pediatrics and Pediatric Anesthesiology personnel.
Activation and rapid dispatch of the team is quite similar to that of the maternal
transport team. One major difference is the integral inclusion of the transport
isolette, After arriving at the referral hospital and assuming responsibility for
the patient, the transport team transfers the HRN to the transpert isolette and
Starts preparation for transport. The most important facet of this preparation
is stabilization of the HRN within the self-contained environment of the isolette
(33).

D. Pretransport Stabilization of the HRN. If necessary, the transport team
must be prepared to spend several hours co achieve sufficient stabilization of
the HRN for transport (33). Because respiratory distress is usually present,
tracheal intubation is often accomplished, and assisted ventilation with a humid-
ified oxygen mixture is instituted. If severe RDS is present, assisted ventila-
tion may be in the form of continuous positive airway pressure (CPAP) after the
procedure of Gregory (32). Respiratory stabilization is judged mainly on the
external color of the HRN, and on measured values of Paopg, Pacg,, and arte-ial
pH. When available, a tePags monitor is positioned at this time for subsequent
use during transport. Catheterization of the umbilical artery is also necessary
in most cases. Although the umbilical vein may be used, the artery is usually
preferred because, besides providing medication access to the bloodstream, it
also provides access to HR and BP monitoring, and arterial blood sampling for
acid/base and blood gas+assessments. The team routinely carries its own equip-
ment and medications for emergency treatment of hypovolemia, hypoglycemia,

10


10.

14,

References

Alistair, G. S and M. B. Philip: Oxygen Plus Pressure Plus Time: The
Etiology of Bronchopulmonary Dysplasia, J. Pediatr., 55:44-50, 1975.

Avery, M. E. and B. D. Fletcher: The Lung and Its Disorders in the Newborn
Infant, Third Edition, W. B. Saunders Co., Philadeiphia, Pennsylvania, 1°74.

Avery, M. E. and J. Mead: Surface Properties in Relation te Atelectasis and
Hyaline Membrane Disease, Am. J. Dis. Child., 97:517, 1959.

Beutow, K. C. and S. W. Klein: Effect of Maintenance of “Normal Skin
Temperature and Survival of Infants of Low Birthweight, J. Pediatr.,
34:163, 1964.

Bowes, W. A.: Discussion: Physiologic Factors in Air Transport. In
Maternal Air Transport Conference, S$. N. Graven (Ed.), Mead Johnson Co.,
1979, p. 63.

Brimhall, D. C.: Management Issues of Neonatal Air Transport. In
Newborn Air Transport Conference, S. XN. Graven (Ed.), Mead Johnson Co.,
1978, pp. 7-9.

Brown, F. B: The Management of High-Risk Obstetric Transfer Patients,
Obstet. Gynecol., 51:674-676, 1977.

Chance, W., J. J. O’Brien, and P. R. Sawyer: Transportation of Sick
Neonates, 1972: An Unsatisfactory Aspect of Medical Care, Can. Med.
Assoc. J., 109:847-851, 1973.

Claybaugh, G., W. Clewell, F. Dusty, M. Flux, S. N. Graven, A. Hachel, and
G. Merenstein: Maternal Air Transport Guidelines, Mead Johnson Co.,
(in Press).

Cunningham, M. D.: Aspiration Pneumonitis and Newborn Air Transport. In
Newborn Air Transport Conference, S. N. Graven (Ed.}, Mead Johnson Co.,
1978, pp. 64-66.

Cunningham, M. D.: Discussion: Physiologic Factors in Air Transport. In
Maternal Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co.,
1979, p. 59.

Cunningham, M. D.: Newborn Air Transport by Helicopter. In Newborn Air
Transport Conference, S. N. Graven (Eé.), Mead Johnson Co., 1978, pp. 4-6.

Cunningham, M. D. and F. R. Smith: Stabilization and Transport oi Severely
Til infants, Pediatr. Clin. North Am., 20:359-366, 1973.

Douek, E. L., H. Bannister, H. C. Rodson, P. Ashcraft, and K. N. Humphries:
Effects of Incubator Noise on the Cochlea of the Newborn cet, 2:1110-
1133, 1976.



EVALUATION OF CARDIOPULMONARY FACTORS CRITICAL
TO SUCCESSFUL EMERGENCY PERINATAL AIR TRANSPORT

I. INTRODUCTION.

The perinatal period generally encompasses the last trimester of pregnancy
through the first 28 days of neonatal life. The primary foci of perinatal con-
cern are the high-risk pregnant woman (HRPW) and the high-risk neonate (HRN).

Perinatal maternal mortality per 100,000 live births has decreased from
582.1 in 1935 to 47.0 in 1955, and 12.3 in 1976 (53). Neonatal mortality (less
than 28 days of age) per 1,000 live births has decreased from 20.5 in 1950 to
18.7 in 1960, and 10.9 in 1976 (53). These decreased mortality rates have been
mainly ascribed to the emergence and development of specialized perinatal care
facilities (level III care) (10,13,28,33,64,67). Most major urban medical centers
now contain expertly staffed and fully equipped level III perinatal facilities.

The medical personnel and equipment of most rural clinics and hospitals
(level I care) are adequate for obstetrical delivery of a normal full-term fetus
from a norma] woman. If antenatal risk is first detected at a level III
facility, then level III care is immediately available with the best chance
for an optimum outcome. However, if antenatal risk is first discovered at a
level I facility, then rapid, safe transport is the logical link to optimum
care in a level II or III facility. If neonatal risk is first detected after
birth in a level I facility, then rapid transport to a level II or III facii~
ity is similarly indicated. A substantial percentage of HRN's will continue
to be born at level I facilities because HRN's are not always detectable before
birth (8,45,61,63).

II. REGIONALIZATION OF PERINATAL CARE.

To accomplish the most efficient utilization of leveis II and III perinatal
facilities within any given geographic area, the concept of regionalization of
services has been applied. The functional hub of any regional system is its
communications and dispatch (CD) center. The CD center integrates all functions
of the regional system. It is staffed 24 h a day, 365 days a year. It keeps
daily records of all available bed space in intensive care units of ail levels
II and III facilities within the region. It assigns each request to an appro-
priate level II cr III facility. Jt dispatches medical transport teams to the
referral hospitals to provide the needed degree of intensive care en route to
the assigned receiving facility. It coordinates ail ground and air transport.
The goal of regionalized care is to provide each HRPW and HRN with the level of
care consistent with their respective medical conditions.

The concept of regionalized perinatal care has been endorsed by the American
Medical Association, the American College of Obstetricians and Gynecolegists,

conde

eT.


APPENDIX

List of Conferees

Carl L. Bose, M.D.

Medical Director, Neonatal Transport System
Assistant Professor

Department of Pediatrics

University of Utah Medical Center

Salt Lake City, Utah

Watson A. Bowes, Jr., M.D.

Professor

Department of Obstetrics and Gynecology
University of Colorado Health Sciences Center
Denver, Colorado

Frederick B. Brown, M.D.

LTC, MC

Chief, Obstetrics and Gynecology Service
Fort Carson Army Hospital

Fort Carson, Colorado

William Clewell. M.D.

Director, “Fligat For Life" Service
Department of Obstetrics and Gynecology
University of Colorado Health Sciences Center
Denver, Colorado

M. Douglas Cunningham, M.D.

Chief, Division of Neonatology

Associate Professor

Department of Pediatrics

University of Kentucky Cullege cf Medicine
Lexington, Kentucky

Jane Deacon, R.N.

Head Nurse of Transport
Newborn Emergency Service
The Children's Hospital
Denver, Colorado

Lawrence J. Fenton, M.D.

Associate Professor

Director Neonatai-Fiology Service

Department of Pediatrics

University of Scuth Dakota School of Medicine
Sioux Falls, South Dakota

7

it eget


47.

48.

49,

50.

51.

52.

53.

54.

57.

58.

59.

60.

61.

62.

Leonard, A. S. and R. H. Rich: Air Transport and Respiratory Problems in
Patients with Diaphragmatic Hernia and Tracheoesophageal Fistula. In Newborn
Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1978, pp.
67-71.

Liebman, J., R. Lucas, A. Moss, E. Cotton, A. Rosenthan, and H. Ruttenberg:
Airline Travel for Children With Chronic Pulmonary Disease, J. Pediatr.,
57:408-410, 1976.

Maternal Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979.

Mazzi, E, R. Gutherlet, and J. A. Phillips: Maryland State Intensive Care
Neonatal Program (MSICNP), Part 2: Role of the Maryland State Police Aviation

Division, Maryland State Med. J., 26:48-50, 1977.

Merenstein, G. B., G. Pettett, J. Woodall, and J. M. Hill: An Analysis of
Air Transport Results in the Sick Newborn. TI. Antenatal and Neonatal
Referrals, Am. J. Obstet. Gynecol., 126:520-525, 1977.

Merenstein, G. B., and L. G. Way: Neonatal Air Transport and Congenital
Heart Disease. In Newborn Air Transport Conference, S. N. Graven (Ed.),
Mead Johnson Co., 1978, pp. 72-73.

National Center for Health Statistics. Facts of e and Peath, U.S. Depart-
ment of Health, Education, and Welfare, Publication No. (PHS) 79-1222,
November, 1978, pp. 8-9,

National Highway Traffic Safety Administration, and the American Medicai
Association Commission on Emergency Medical Services. Ambulance
Guidelines, U.S. Department of Transportation, 1981.

Newborn Air Transport Conference, S. N. Graven (Ed.}, Mead Johnson Co., 1978.

Oetgen, W. J. and R. D. Landes: Aeromedical Evaluation of High Risk Infants:
Experience in a Military Medical Center, Mil. Med., 143:712-713, 1978.

Oxer, H. F.: Aeromedical Evacuation of the Seriously Ill, Br. Med. J.,
3:692-694, 1975.

Pang, L. M. and R
Anesthesiology, 4

. B. Meliins: Neonatal Cardiorespiratory Physiology,
3:171-196, 1975.

Peachin, M. L.: Air Transport of Mothers: Air Vehicles. In Maternal Air
Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979, pp. 88-95.

mai Air
>» Pp. 75-79.

Perkins, R. P.: Air Transport of Mothers: Equipment. In M
Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 19

Pettett, G.: Outcomes of Maternal Air Transport. In Maternal Air Transport
Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979, pp. 29-32.

Pettett, G., G. B. Merenstein, F. C. Battaglia, L. J. Butterfield, and
R. Efird: An Analysis of Air Transport Results in the Sick Newborn Infant.
Part I. The Transport Team, J. Pediatr., 55:774-782, 1975.



Linda S. Krell, M.D.

Medical Director

Newborn Emergency Service

The Children's Hospital

Assistant Professor

Department of Perinatology

University of Colorado Health Sciences Center
Denver, Colorado

Gerald B. Merenstein, M.D.

COL, MC

Chief, Department of Pediatrics
Fitzsimons Army Medical Center
Aurora, Colorado

Associate Clinical Professor
Department of Pediatrics

University of Colorado Medical Center
Denver, Colorado

Steven Missall, M.D.

Co-Director

Intensive Care Nursery

Washoe Medical Center

Assistant Professor

Department of Pediatrics

University of Nevada School of Medical Sciences
Reno, Nevada

Donald E. Pickering, M.D.

Professor

Department of Pediatrics

University of Nevada School of Medical Sciences
Reno, Nevada

Robert Roth, M.D.

Newborn Services Office
Mount Zion Hospital

1600 Divisadero

San Francisco, California

Jeanne Thornton, R.N.

Head Nurse of Transport
Department of Pediatrics
University of Utah Medical Center
Salt Lake City, Utah

Dianne Wcodall, M.D.
Newborn Emergency Service
The Children's Hospital
Denver, Colorado

Michael L. Wyman, M.D.
Department of Pediatrics
Skemp-Grandview Clinic
LaCrosse, Wisconsin
ig



of any pulmonary condition which impedes gas exchange at the alveolar/capillary
level (e.g., RDS, aspiration syndrome, etc.) will decrease the ability of the
lung to sufficiently increase oxygen uptake and C02 excretion to keep up with
the increased metabolic demand. The additional metabolic demand of increased
respiratory efforts can cause a further decrease in Pag,, an increase in Pacgg,
and a decrease in pH. The rapidly decompensating hypoxemia, hypercapnia, and
acidosis can increase pulmorary vascular resistance, which can further compro-
mise pulmonary gas exchange by reducing pulmonary capillary blood flow, and
reopening the vascular shunts of fetal circulation. If unchecked, these decom-
pensations, aiong with concomitant hypoglycemia, can cause a rapid deterioration
of circulatory adequacy culminating in ine death of the infant. This complex
chain of events cce2 occur within a epan of several min (23,31,47,74}.

The NTE of the isolette environment usually lies between 36.5° and
37.5°C (35,65), According to criteria suggested by one of our conferees (74),
the HRN is probably in an optim thermal environment when: his abdominal skin
temperature is 35.5° to 36.5°C, his rectal temperature is about Q. 5°c higher
than that of abdominal skin, his extremity skin temperature is 3° to 4°C lower
than that of abdominal skin, and his isolette temperature is 1° to 3°C higher
than that of abdominal skin. During transport, neonatal temperature is contin-
uously monitored via skin or rectal thermal electrodes. Some of the new-
generation isolettes use a monitored intraisolette air temperature to servo-
control the isolette's thermal system (35,63). Substantial research has been
done on the possibility of using the neonate’s temperature to servocontrol the
isolette's thermal system (68).

The intraisolette oxygenation of the HRN is also a factor in main-
taining a suitable NTE. The oxygen mixture flowing past the URN must be humid-
ified to impede evaporative water losses, and warmed sufficiently to avoid
subjecting the infant to positive or negative theraal gradients (63). Our con-
ferees generally agree that maintaining the isolette NIE, after its initial sta-
bilization within a surrounding stable thermal environment, poses very few
problems. Difficulty is possible during transfer of the isolette from the
hospital to the ambulance, and from the ambulance to the aircraft in very cold
or very hot weather. During air transport, changes in thermal balance are also
probable whenever the isolette hood is opened to medically service the HRN (44).
New-generation isolettes have improved thermal protection during hood access
(35,63). Our conferees agree that proper thermal control is a major factor in
successful transport of the HRN.

4. Humidity. If dry ges surrounded the HRN during «ir transport, sub~
stantial gradients for potential loss of heat and water could exist. The rate
of such losses are potentiated by the high surface-to-mass ratio of the neonate
(47). Further, respiratory therapy with unhumid’fic3 oxygen mixtures could
aggravate any existing pulmonary condition, cause stressful discomfort, and
interfere with adequate oxygenation (57). The HRN is therefore preventively
respired with warmed and humidified oxygen mixtures. Several means of humidi-
fication were reported by our conferees. These inciuded flowing the oxygen mix-
ture over or through water, over water-soaked surgicai sponges, through nebulized
water mists, and by placing water-soaked towels within the ienlette. Each con-
feree felt that his/her particular methed provided adecuate humidification. All
the conferees agree that warming and humidification ef both the intraisclette
environment and the inspired oxygen mixtures were desirable as preventive measures.

14



from sea level to 6,000 ft altitude will cause an enciored gas volume to expand
about 25 percent (47). The expansion of such gases in the inner ear or sinuses
can be quite painful. If gas is trapped in the gastrointestinal tract of the
HRPW, its expansion can be both painful and circulatorily detrimental to the
mother and fetus (9,16). In the specific instances of paralytic ileus or bowel
obstruction in the HRPW, transport in unpressurized aircraft is contraindicated
(9,16).

2. Hypoxia. Proper oxygenation of the HRPW and fetus starts with the
provision of an adequate maternal inspired oxygen partial pressure (PI9, ). Since
the exact relationship between Py, , maternal arteria! Po. (@agy), and Petal oxy-
genation is nct well understood, 9 has been recomended 29) that a Pig. of 135 mm
mercury (torr) be supplied to the HRPW during air transport, If eviden€e of
maternal pulmonary disease or fetal distress is present, a maternal Pz,, of more
than 240 torr should be provided (9). To provide the required Prone 28 appro-
priate fraction of inspired oxygen Ip. ) is obtained by monitored2blending of
regulated flows from tanks of compressed JQQ percent oxygen and air, The Fig
required for a given Prog is a function of ambient cabin pressure, and is readily
calculated (36).

Proper oxygenation. of the HRPW during flight could be titrated if
continuous monitoring of the maternal and fetal Pagg's were possible. To prevent
hypoxemia in the fetus, the maternal Pagg should be maintained well above the
critical minimum of 60 torr (11). In-flight monitoring of fetal Pago is con-
sidered te be practically impossible. The maternal Pa, could possifiy be mon-
itored by a transcutaneous (tc) Pag, sensor (43,44). According to our conferees,
several commercial versions of the tcPag, sensor have been used for neonatal Pag
monitoring in the intensive care nursery (ICN), and during transport. To date,
this type of instrument has not been used for maternal Page monitoring during
transport.

If the maternal hemoglobin concentration is both adequate and stabie,
oxygenation could he titrated by monitoring maternel oxyhemoglobin saturation
/ab02) with a te ear oximeter. The possible use of an ear oximeter for maternal
monitoring has been suggested by one of our conferees (11). Its use is most
probably impeded by its purchase price, its size, poor portability, and its poor
tolerance to environmental extremes and rough handling. Currently, the maternzl
oxygenation status during air transport is estimated by the attending physician
or RN based on the patient's skin color, symptoms, and vital signs. Because the
fetus may have more intrinsic protection against hyperoxygenation than against
hypo-oxygenation (43), conferee consensus favored the use of maternal Flog value,
which was slightly greater than one deemed to be fully adequate.

Besides an adequate Py, , oxygenation ec” the HRPW and fetus also
depends on pulmonary adequacy. In the presence of maternal pulmonary cisease,
acid/base imbalances car easily result from a highly variable maternal response
to altitude hypoxia (11). In the presence of altitude hypoxia, maternal hyper-
ventilation <esulting in a respiratory alkalosis could advers:ly affect the hypox-
emic tolerance of the fetus (11). The use of an adequate Pigg and/or a pressur-
ized aircraft are logical preventive measures (11).


by any given perinatal transport service, shared usage has evolved in many cases
(19). For instance, the perinatal transport service located in Baltimore,
Maryland, utilizes the Bell 206B Jet Ranger helicopters of the State Police
(50), and that of Columbus, Ohio, utilizes a UH-TH "Huey" helicopter of the
Ohio Army National Guard (39). Both helicopters have speeds of 140 miles per
hour (mph); the "Huey" has a range of 275 miles, and the Jet Ranger a range

of 400 miles.

When a perinatal region is obsiged to extend its coverate out to a 400~ to
500-mile radius, fixed-wing aircraft participate as transport vehicles. Peri-
natal regions based at Denver, Colorado; Reno, Nevada; Salt Lake City, Utah; and
Tucson, Arizona, are exampies of extended radial coverage, Although perinatal
transport experts agree that a multiengine, pressurized aircraft is the best
type for perinatal air transport, operational costs often dictate the use of
single-engine and/or unpressurized aircraft. Transport in single-engine air-
craft costs about one-third that of larger, pressurized aircraft (26). Relatively
small engine aircraft such as the Piper Lance, Cherokee 6, or Cessna 210 have
served as transport vehicles (59). These aircraft have speeds of about 200 mph.
Larger twin-engine aircraft such as Piper's Navaho and Chieftain, Cessna's 402 and
421 (pressurized), and Beechcraft's King Air Prop-Jet have speeds of 240 to 330
mph, and flight ranges in excess of 1,000 miles (59). When cost is no object, and
great distances must be covered in minimum times, then aircraft such as the 500
mph Lear or Aero Commander Jets (59), or the Mitsubishi MU-23 Prop-Jet (6) have
been used.

When critical care of the patient is required during air transport, then
adequate cabin space becomes an important consideration. Cabin space in single-
engine aircraft can barely accommodate one patient and one medical attendant
with little or no room left for monitoring or life-support equipment (17).
Minimum space requirements for optimum cabin configurations have been proposed
(40). These minima are cabin width of 50 inches, height of 51 inches, and a
volume of 220 cubic feet (40). Most of the twin-engine aircraft used in peri-
natal transport meet or exceed these requirements (42). The remainder of this
report will focus its attention mainly on air transport in fixed-wing aircraft.

IV. IMPORTANT CHARACTERISTICS OF A SUCCESSFUL PERINATAL ATR TRANSPORT SYSTEM.

Although emergency perinatal transport is conceptually young, several
excellent empirically based transport manuals have been written (9,21,54,66,69).
All of these contain major sections on air transport. In addition, two excelient
succeesive conferences on Newborn Air Transport and Maternal Air Transport have
recently appeared in print (49,55). Many of the participants in these tw con-
ferences (49,55) also participated as updating information sources for tais
report.

Transfer of an HRPW or HRN to a level Ii or Lil facility is indicated when
the patient's needs have exceeded local expertise or facilities (39). The
decision to transfer the patient should be made when the recognized hazards of
the journey do not outweigh the possible advantages te be gained after arrival
(69). Transport should be by the fastest and safest means (33).



the American Academy of Pediatrics, and the American Academy of Family Physicians
(29). Perinatal care has also been regionalized in the major military medical
centers and integrated with the aeromedical evacuation system of the United States
Air Force (56). Substantial decreases in mortality rates have already heen
ascribed to regionalization of perinatal care (10,13,33,61).

An important component of regionalized care is its integrated system of
transportation. Transport is accomplished by surface and airborne vehicles.
About 80 percent of all transports involve surface vehicles such as ambulances
and vans, and about 20 percent involve air transport by helicopters or fixed-wing
aircraft. This report is primarily focused on perinatal air transport, and on
potential effects of the airborne environment on cardiopulmonary functions in
the HRPW and HRN. Source materials include recent scientific publications, and
firstnand oral information and publications from 23 physicians and registered
nurses (RN's) having 174 cumulative years of "hands on't experience in perinatal
air transport. The oral information was obtained by individual telephone con-
ferences. All telephone conferees are listed in Appendix I.

The main purpose of this study is to integrate all of the updated information
into a comprehensive status report for possible use in formulating appropriate
guidelines for the aviation medicine community in the area of perinatal emergency
air transport.

TIL. PERATIONAL RADIT OF TRANSPORT MODES.

The geographic hub of any perinatal region usually consists of one or more
level III perinatal facilities. The CD center usually operates out of one of
the level IIL facilities. Vehicular transport modes depend on local conditions
such as terrain, pepuiation density, weather patterns, and availability of sur-
face or air carriers (33). Within a radius of about 50 miles from the geographic
hub, specially equipped and manned ambulances and vans constitute the main mode
of transport. Because of its small area, high population density, and high con-
centration of level Til centers, any metropolitan perinatal transport service
(e.g., New York City or Chicago) operates quite efficiently with the main use of
surface vehicles (33). In the more densely populated eastern half of the United
States, level III facilities very often overlap within radii of 50 to 100 miles.
Because transport time is very often a critical survival factor, the 50-miie
radius is the approximate cutoff distance for surface transport in densely pop~
ulated urban areas. The $0-mile radius is generality equated to a one-way travel
time of about 1 h.

When a perinatal care region is obliged to extend its coverage to a radius
of about 150 miles, then surface transport is usually too slow for emergency
conditions. When available, the helicopter has been used frequently in the 50+ to
150-mile radius. There are several major patient-related disadvantages to heli-
copter use (12,40,57). These will be covered later by way of contrasting the
advantages of fixed-wing aircraft. The main advantages of helicopter use are:
their excellent emergency response time, theiz I-h distance coverage of about three
to four times that of a surface vehicle, and their "door-to-door" capability, often
obviating the need for surface transport between the airport and the hospital.
Because operational costs are a majcz impediment to exclusive use of helicopters



5. Motion. During flight, aircraft motions may occasionally be accen-
tuated in rate and amplitude by weather and turbulence. Although motion sickness
may produce nausea, BP changes, sweating, pallor, and vomiting in adults, little
is known about such effects in the neonate (42,69). One of our conferees has
reported that a substantial number of infants who were stable throughout a flight,
developed bradycardia, apnea, and vasomotor changes at the tine of aircraft
descent and approach for landing (42), Another cuonferee has reported that HRN's
dislike motion of a jostiing type. In this regard, the conferee has observed sub-
stantial apnea responses to jostling, especially during surface vehicle transport
between the hospital and the aircraft.

Since en route care of the HRN depends on full functional alertness
of the medical transport personnel, motion sickness in a team member could have
an adverse effect on airborne neonatal care. Antiemetics are preventively useful
if taken 30 to 60 min prior to takeoff. However, the side effect of drowsiness may
affect rapidity and sharpness of judgment (42). Since the nausea of motion sick-
ness during flight may be synergized with altitude hypoxia, breathing of supplemental
oxygen may be useful (42).

6. Noise and Vibration. Noise and vibration may reach considerable levels
during air transport. Noise levels in fixed-wing aircraft have been measured in the
75 to 105 dB range (70). Noise levels of the same order have been recorded inside
isolettes during air transport (70). Some new-generation isolettes have success—
fully incorporated noise suppression technology (63). Single short-duration
exposures of these encountered noise levels are not considered to be hazardous
(33). Although no definitive studies have been done, possible adverse effects of
noise and vibration on the transported HRN should not be ruled out (42). Segal
(69) and Roy (67) have reported that neonatal disturbance by noice and vibration
may be associated with regurgitation, and that suppression of the gag reflex by
vibration may cause aspiration. If the HRN is being transported without tracheal
intubation, a lateral decubitus position may provide the best safeguard against
aspiration of regurgitated material (67,69).

A substantial portion of HRN's are transported for indications of CNS
pathology (17). Although confirming studies are lacking, vibration during air
transport is suspected as a causal and/or aggravating factor relevant to intra-
cranial hemorrhage (17). This suspicion is based on the greater incidence of
intracranial hemorrhage in neonates transported postnatally as compared te those
who were transported "in utero" (17).

The major impact of noise and vibration is on in-flight monitoring.
Most monitoring is currently accomplished electronically with digital readout
capability (54). Doppler sensing has mainly replaced auscultative functions in
flight. With respect to visual monitoring, one conferee has reported that blurred
vision may result if the resonant vibration frequency of the eyeball (40 cycles
per s) is present (42). The technology of monitoring during air transport has
made considerable progress in recent times (33,63). Most conferees agree that
the use of large, multiengine, all-weather aircraft should minimize the levels
ané effects of noise and vibration (6).

15


before or during transport, Pediatric personnel may also participate as team
members. immediately upon arrival at the referring hospital, the maternal trans-
port team assumes responsibility for the patient, assesses and stabilizes her
condition as much as time permits.

Perinatologists (including conferees) generally agree that transport of
the fetus “in utero" with the subsequent delivery and intensive care for both
mother and premature neonate in a level I2I facility is a far better risk than
delivery in a level I facility with subsequent transport to a level ITI faciiity
(38,45,61,67). Therefore, with the two exceptions of toxemia and substantial
blood loss (16,27), pretransport stabilization of the HRPW is secondary to
speedy preparation for transport.

Patients at medium, high, and ultrahigh transfer risk are candidates
for air transport. If transport time is a critical factor, then air transport
is highly probable. .n the cases of high or ultrahigh transfer risk, the trans-
port team comes prepared to transport the HRPW under constant medical surveil-
lance, deliver her at the referral hospital cr en route, and provide neonatal
resuscitation and iatensive care (15}. Because of the many inherent disadvan-
tages (12,40,57), helicopter transport is considered unacceptable for any HRPW
having a possibility of en route delivery.

Perinatologists agree that early detection of risk in the mother or
fetus, prior to the rupture of membranes or onset of labor, provides the best
chance for stable, safe, unhurried transport to a level III facility (10,38,
45,61,67,71). Early detection of an HRPW is more probable if she has an
alerting medical history of disease and/or previous complicated pregnancies
(29). However, most emergency transports of HRPW's involve first pregnancies
with no prior alerting medical history (28).

B. The Airborne Environment-Cardiopulmonary Factors. Appropric:te in-flight
care for the HRPW inseparably involves the simultaneous welfare of the fetus.
If reasonable preflight stabilization of the HRPW has been achieved, then appro-
priate in-flight monitoring and support of cardiopulmonary functions will greatly
foster a successful transport (16).

During flight, environmental components with adverse cardiopulmonary
potential include hypobarism, hypoxia, low environmental temperature, low humid-
ity, motion, noise, and vibration. Many transport aircraft are cepable of con-
trolling some, but not all, of these environmental factors.

1. Hypobarism. To prevent all adverse effects directly ascribed to
hypobarism (9,16,23,54), perinatologists (including conferees) universally agre
that ail perinatal air transport should ideally be accomplished in pressurized
aircraft. Transport costs often preclude the ideal solution (26). When the
condition of the HRPW is considered to be excellent and stable, a maximum cabin
altitude of up to 6,000 ft has been recommended as tolerable for transport (9,27).
If altitudes in excess of 6,000 ft are anticipated, then a pressurized aircraft
is strongly advocated (9).

Reduction of ambient pressure surrounding any enclosed gas-filled
volume will cause that volume to expand. For instance, the pressure change


16.

7.

18.

19.

20.

al.

22.

23.

24.

25.

26.

27.

28.

29.

Dusty, F. and W. A. Bowes, Jr: Indications for Air Transport. In Maternal
Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979, pp.
37-41.

Dusty, F. and W. A. Bowes, Jr.: Physiologic Factors in Air Transport. In
Maternal Air Transport Conference, S. N. Graven (Zd.), Mead Johnson Co.,
1979, pp. 49-52.

Egel, R. T. and G. B. Merenstein: Newborn Air Transport: Proolems of the
Central Nervous System. In Newborn Air Transport Conference, S. N. Graven
{Ed.), Mead Johnsen Co., 1978, pp. 81-85.

Farreil, P. M. and M. E. Avery: Hyaline Membrane Disease, Am, Rev. Respir.
Dis., 111:657-688, 1975.

Felix, W. R.: M:.tropoliten Aeromedical Service: State of the Art, J. Trauma,
16:873, 1976.

Fenton, L. J.: Transport of the Newborn with Idiopathic Respiratory Distress
Syndrome. In Newborn Air Transpert Conference, S. N. Graven (Ed.}), Mead
Johnson Co., 1978, pp. 57-60.

Ferrara, A. and A. Harin: Emergency Transfer of the High-Risk Neonate,
C. V. Mosby Co., St. Louis, 1980.

Flux, Me: Discussion: Physiologic Factors in Air Transpert. In Maternal
Air Transport Conference, S. N. Graven (Ed.}, Mead Johnson Co., 1979, pp.
59-60.

Flux, M. and M. T. Lategola: Physiologic Factors in Air Transport cf Sick
Infants. In Maternal Air Transport Conference, S. N. Graven (Ed.), Mead
Johnson Co., 1979, pp. 53-57.

Frank, L. and D. Massaro: The Lung and Oxygen Toxicity, Arch, Intern. Med.,
139:347-350, 1979.

Gabbe, S. G., R. I. Lowensohn, J. H. Mestman, R. K. Freeman, and U. Goebelsmann:
Lecithin/Sphingomyelin Ratio in Pregnancies Complicated by Diabetes Mellitus,
Am, J. Obstet. Gynecol., 128:757-761, 1977.

Giles, H. R.: Discussion: Equipment Needs and Requirements. In Maternal Air
Transport Conference, $. N. Graven (Ed.), Mead Johnson Co., 1979, p. 84.

Giles, H. R.: Discussion: Organization of Air Transport Services. In
Maternal Air Transpert Conference, S. N. Graven (Ed.}, Mead Johnson Co., 1979,
p- 109.

Giles, H. R.: Outcomes of Maternal Transport. In Maternal Air Transport
Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979, pp. 9-13.

Giles, HE. R., J. Isamen, W. J. Moore, and C. D. Christian: The Arizona High-
Risk Maternal Transport System: An Initial View, Am. J. Obstet. Gynecol.,
128:400-407, 1977.




central nervous system (CNS) hemorrhage, prewature lapor end delivery, and
fetal distress due to uteroplacental insufficiency (16). Magresium sulfate

is usually administered to prevent seizures. The administration of an anti-
hypertensive agent may be considered if diastolic pressures exceed 110 torr.
Depression of monitored vital signs and urinary output (from an indwelling
Foley catheter) calls for cessation of these medications ($,16). Medical trans-
port personnel maintain monitoring vigilance against potential side effects of
any medication used during transport,

3. Environmental Temperature. Most transport aircraft (except heli-
copters) possess adequate heating systems, The main temperature problem is
not only the generation of sufficient heat, but its constant control to pro~
duce 2 neutral thermal environment (NTE) for both the HRPW and fetus. Signif-
icant amounts of heat can be lost by radiation to cold window and airframe
surfaces (9). Because both overheating and underheating can be stressful to
a medically compromised HRPW, care must be exercised to avoid such thermal
stresses during air transport, as well as during surface transport linkage
between the hospital and aircraft in very hot or very cold weather (45). Dur-
ing air transport, a minimum cabin temperature of 75° Fahrenheit (F) is recom-
mended (23,54,74). Even though delivery during air transport is uncommon (28,
37), the capability for higher cabin temperatures during such a delivery should
be present in order to protect the neonate from cold stresses (9,60). Our con-
ferees generally agree that the thermal environment of the HRPW during air
transport has been successfully controlled.

4. Humidity. Ambient air becomes drier as a function of increasing
altitude. At substantial flight altitudes, relative humidities may approximate
desert values of 10 to 12 percent. Inspiration of dry air by a healthy adult
for 2 *o 3 hours is ordinarily innocuous. However, if pulmonary disease is
present in an HRPW, then respiratory therapy with unhumidified oxygen mixtures
could aggravate the pulmonary condition, cause stressful pulmonary discomfort
in an already compromised patient, and interfere with her required oxygenation.
Medical, tank-stored air and 100 percent oxygen each contain less than 10 per-
cent humidity. Our conferees recommended humidification of all oxygen therapy
of the HRPW during transport (9). To avoid undesirable thermal stress, the
inspired oxygen mixtures should be warmed as well as humidified prior to inspi-
ration. Our conferecs agree that warming and humidification of inspired oxygen
mixtures are generally desirable as preventive measures.

5. Motion. Motion sickress is a common problem in the HRPW during
transport, and nausea and vomiting often occur during labor (9). The use of
antiemetics, which have minor labor-inducing properties, should be avoided
during transport (9). Usually motion sickness is minimized if the patient's
head is facing forward in the aircraft (9). Apart from secondary effects of
motion zickness, there are no data on the relationship of motion to specific
problems for mother or fetus (9).

6. Noise and Vibration. Noise and vibration are inseparable from the
flight environment. Both impede maternal monitoring and communication (54).
Measured noise leveis are in the 90 to 110 decibel (dB) range in helicopters, 80
to 105 d3 in single-engine, fixed-wing aircraft, and 75 to 90 dB in nuitiengine,


Proper in-flight respiratory management of the HRPW is also important
when maternal diabetes and pulmonary dysfunctior coexist. Pretranspert assessment
of arterial blood gases and acid/base baiance are highly desirable (11). If the
patient is acidotic, has an elevated arteriel partial pressure of carvon dioxide
(Paco>), and is being infused with bicarbonate, then in-flight oxygen therapy
must be titrated with extra care. The Py, must be high enough to provide suf-
ficient oxygenation for both mother and fetus, but low enough to prevent a life~
threatening maternal CO9 narcosis (22,48). if available, in-flight monitcring
of Pagg, Pesog, and arterial hydrogen ion activity (pH) could allow titrated con-
trol of Pro » assisted ventilation, and acid/base status. Portable tePago mon-
itors are Cémmercialiy available and have been used on adults in hospitais but
mot, as yet, during transport (34). The measurement of erterial pH is routinely
available in hospitals, but not duving transport. Because of general contraindi-
cations to arterial catheterization of the HRPW, useful arterial pH information
could be deduced from venous pH measurements made at a venous infusion site. To
our knowledg , the translation of pH electrode technology to the trensport eaviron-
ment has not occurred. Currently, several commercial sources of portable tePags
monitors are attempting te produce a similar instrument for monitoring the
tcPacgs- If transport monitoring of arterial pH should remain a practical impos-
sibility, then the direction of pE changes might be usefully inferred from
tePaco, monitoring. Technological advances could piay 2 major positive role
in this area.

The maintenance of cardiovascuiar runctions are also important to
the oxygenation of the HRPW and fetus. If substantial matertcl icsses of blood
volume have occurred, they should be replaced prior to transport in order to
prevent hypotension and/or hypoperfusion effects in both mother and fetus (16).
Low blood volume can cause shock, fetal asphyxia, and premature labor and delivery
(16). Maintenance of blood volume may be accomplished curing transport by care-
fully monitored supplemental intravenous i fusions (16). Catheterizatiens, intu-
bations, or other delicate procedures should be done prier to transport co avoid
the many complications of doing them in the flight environment (16). To aid
circulatory stability, the HRPW is usually transported in a lateral recumbent
position (5,16).

During transport, maternal blood pressure (BP) is usually monitored
by means of systolic radial puise detection during BP cuff deflation. Heart rate
{HR} is monitored by radial pulse counts. The s iitored control of BP in the
HBRPW is especially important because adverse eff .cts can result from either
hypotension or hypertension (9,16). Because rupture of membranes and premature
jabor account for about 75 percent of HRPW air transports (15,16). labor is oftex
arrested during transport by ‘atravenous infu: m of tocolytic agents (16).
Unfortunately, most tocolytic agents are capable of preducing hypotension (16).
Therefore, frequent monitoring of maternal BP end HR, and fetai HR (using a
Doppler sensor) are necessary to detect incipient signs o! maternai hypotension
and/or fetal distress (16). The appearance of such signs call fer cessation of
tocolytic iniusicn (9,16). Tocolytic agents are usually contraindicated in the
third trimester, if significant uteroplacental hemorrhage is present (16).

Hypertensive complications of pregnancy accvunt for about 15 percent
of HRPW transports (16). The development of eclampsia may produce seizures,



Mainly because of prohibitive acquisition and operational costs, most peri-
natal air transport is accomplished by contracting air ambulance services.
Specifications for optimum types of aircraft as well as included equipment have
been detailed in several publications (9,21,49,54,55,66,69}. Duties and respon~
sibilities of the pilot as an integral member of the transport team have been
detailed elsewhere (41).

The most important component of a successful perinatal transport system is
the medical transport team. The team is dispatched from the CD center to the
referral hospital, assumes responsibility for the patient, stabilizes and pre-
pares the patient for transport, and provides critical care and monitoring
en route to the receiving facility. Typically, a transport team can be airborne
within 50 to 70 min after the referral call is received at the CD center (16,42).
Collectively, this team must possess the skills and knowledge to manage a wide
variety of perinatal emergency conditions (41). Team members may be appro-
priately trained physicians, RN's, respiratory therapists (RT's), or emergency
medicei technicians (EMT's). One member of the team should be a physician or
RN (54). The nature of the emergency governs the composition of the team. In
between transports, al] team personnel are usually full-time staff members of
level III perinatal intensive care maternity or nursery facilities. An integral
part of their duties at such facilities is to be on standby availability for
transport duty (49,55).

The CD center coordinates all aspects of the air transport system. Its
mair. functions have been described earlier. Perinatal air transport has played
a successful role in the reduction of HRPW and HRN morbidity and mortality as
reflected in published reports (10,13,28,33,38,61,67), and in the experience of
our telephone conferees.

V. EMERGENCY MATERNAL AIR TRANSPORT.

A. Indications For Maternal Transport. Several publications (15,28,29,31,
54,69) contain detailed indications for emergency transport of the HRPW. The
three major indication categories (15) are obstetrical, medical, and surgical
complications. The obstetrical complications of premature rupture of membranes
or premature labor at less than 34 weeks of gestation, or with an estimated
fetal weight of less than 2,000 gm account for about 75 percent of all maternal
transports. Severe eclampsia or uther hypertensive complication, multiple
gestation, poorly controlled diabetes meliitus, intrauterine growth retardation,
third trimester bleeding, Rh isoimmunization, and abnormal premature cervical
dilation are all factors which increase the probability of premature delivery.
Medical complications include the presence of any acute or chronic severe
disease in the HRPW. Surgical complications include those related to accidental
trauma as well as abdominal and thoracic emergencies at less than 34 weeks
gestation, or with an estimated fetal weight of less than 2,000 gm. The pres-
ence of one or more of these conditions usually defines the HRPW.

A maternal eir transport service may operate its own CD center based in
the intensive care section of an Obstetrics and Gynecology Department, or share
a CD center with a nearby Pediatrics Department. The maternal transport team con~
sists primarily of Obstetrics and Gynecology personnel. If birth is anticipated


Harlan R. Giles, M.D.

Associate Professor

Department of Obstetrics and Gynecology
Texas Tech. University Health Sciences Center
Lubbock, Texas

Thomas Gilmore, M.D.

Associate Professor

Department of Obstetrics and Gynecology
University of South Dakota School of Medicine
Sioux Falis, South Dakota

Stanley N. Graven, M.D.

Professor

Department of Child Health
University of Missouri Me“icat Center
Columbia, Missouri

Alvin Hackel, M.D.

Associate Professor

Chief, Pediatric Anesthesia

Clinical Anesthesia/Pediatrics
Stanford University School of Medicine
Stanford, California

Thomas R. Harris, M.D.

Director, Newborn Intensive Care Unit
Associate Professor

Department of Pediatrics

University of Utah Medical Center
Salt Lake City, Utah

Jay Hill, M.D.

COL, MC

Chief, Obstetric Service
Fitzsimons Army Medical Center
Denver, Colorado

Peter R. Honeyfield, M.D.

Co-Director, Newborn Intensive Care Unit
Director, Newborn Emergency Service

The Children's Hospital

Assistant Professor

Department of Pediatrics

vuasersity of Colorado Medical Center
Denver, Colorado

Neil K. Kochenour, M.D.

Head, Division of Maternal Fetal Medicine
Assistant Professor

Department of Obstetrics and Gynecology
University of Utah Medical Center

Salt Lake City, Utah

18


63. Pickering, D. E.: State-of-the-Art Design Solution for Continuing Intensive
Care of Distressed Infants During Land and Air Transport. In Newborn Air
Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1978, pp. 27-44.

64. Ramamurthy, R. S., M. Reveri, S. P. Pyati, and M. Reale: Transport of High
Risk Neonates. Part I: Clinical and Metabolic Observations, Ill. Med. J.,
156:518-521, 1976.

65. Ramamurthy, R. S., T. F Yeh, and R. S. Pildes: Transport of High Risk
Neonates. Part II: Short Term Intensive Care and Stabilization of the
Sick Infant, Ill. Med. J., 150:601-604, 1976.

66. Roberts, D. and T. Porter: High-Risk Infant Transport Manual of the Alaska
Newborn Project, Department of Health and Social Services, Alaska, 1978.

67. Roy, R. D. N.: Neonatal Transport, Med. J. Aust., 2:862-864, 1977.

68. Scopes, J. W.: A New Look at Thermoregulation in the Newborn, Proc. R.
Soc. Med., 70:207~-208, 1977.

69. Segal, S., C. Carrier, B. H. Doray, K. E. Scott, L. Stern, and P. R. Swyer:
Transport of High-Risk Newborn Infants (A Manual), Canadian Pediatric Society,
1972.

70. Shenai, J. P.: Sound Levels for Neonates in Transit, J. Pediatr., 90:
811-812, 1977.

71. Staub, G. F. and J. P. Paulissen: Development and Implementation of a Pian
for Perinatal Health in Illinois, Ill. Med. J., 150:522-525, 1976.

72. Volman, H. B. and J. F. Pearson: What the Fetus Feels, Br. Med. J.,
1:233-234, 1980.

73. Wyman, M. L.: Management of Respiratory Emergencies During Air Transport.
In Newborn Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co.,
1978, pp. 61-63.

74. Wyman, M. L.: Thermal Environment During Transport. In Newborn Air
Transport Conference, S. N. Graven (Ed.), 1978, pp. 38-41.

US. GOVERNMENT PRINTING OFFICE: 1982 369-688/726 173

24



List of Abbreviations

HRPW High-risk pregnant woman

HRN High-risk neonate

cD Communications and dispatch

RN Registered nurse

mph Miles per hour

RT Respiratory Therapist

EMT Emergency Medical Technician

Ploy Partial pressure of inspired oxygen

Pag, Partial pressure of arterial oxygen

Figg Fraction of inspired oxygen

te Transcutaneous

ICN Intensive care nursery

HbO2 Oxyhemoglobin saturation

Pacos Partial pressure of arterial carbon dioxide
pH Negative log of hydrogen ion activity

NTE Neutral thermal environment

RDS Respiratory disease syndrome

L/S Lecithin/sphingomyelin ratio

BP Blood pressure

bpm Beats per minute

RR Heart rate

CPAP Continuous positive airway pressure

MAP Mean arterial pressure

dB Decibel

CNS Centrai nervous system

torr Millimeters of mercury

F Fahrenheit ct nn |
c Celsius , Accession Por

ALT

1 By.
Distriduticn/ .
Availability Codes
~ ‘Avail anc/or -_
Special



acid/base derangements, cardiogenic shock, and electrolyte derangements. If
blood gas analyses indicate metabolic or respiratory acidosis, appropriate
infusion of bicarbonate is instituted to reverse the acidotic pH, and assisted
ventilation adjusted to decrease Pacog> and increase Pago: Prolonged hypo-
thermic acidosis may result in noenat&l kernicterus, despite a low total level
of bilirubin (23,74). Hypovolemic hypotension, which is usually intensified
by bicarbonate infusion, may be corrected by whole blood infusion (if available)
or by volume-titrated infusions of aibumin or physiologic saline (31) Hypogly-
cemia (blood giucose < 20 mg percent) is usually treated with a titrated infu-
sion of dextrose in water (31). Electrolyte decreases are similarly titrated.
Since the predicted average blood volume of the neonate is about 85 ml/kg (31),
infusion volume must be carefully titrated to avoid undesirable effects of
hypervolemia. Methods and criteria for titrated correction of hypovolemia,
hypoglycemia, as well as acid/base and electrolyte derangements, have been
detailed elsewhere (31,33,42,55,69).

If unpressurized flight is anticipated, an orogastric tube is emplaced,
the stomach is aspirated, and the tube is left in Place to vent any gas dis-
tension that may be caused by subsequent altitude expansion (42,54,69). If a
pneumothorax is present and causing respiratory distress, its necessary reduc-
tion is usually accomplished via a thoracostomy tube attached to a Heimlich
valve (42,54,69). The thoracostomy tube is left in place to counteract any
altitude expansion of gas.

Pretransport temperature stabilization of the HRN within the isolette
environment is very important. Because biologic temperature controls may not
be fully developed in the premature HRN, the distressed infant is quite vulner-
able to both hypothermia and hyperthermia (74). Our conferees agree that
stabilization and subsequent transport control of an NIE is a critical survival
factor. Recommended initial isolette temperature settings (relative humidity

of 50 percent) for neonates of various birth weights and ages have been detailed
elsewhere (66,69).

The achievement of sufficient stabilization for transport is usually
reflected by stabilized values of monitored vital signs. Because of the motion,
noise, and vibration of the airborne environment, conversion of ail monitors to
an electronic digital readout mode is highly desirable. Most new-generation
isolettes have incorperated this mode of monitoring.

E. The Airborne Environment ~ Cardiopulmonary Factors. Once stabilization
of the HRN is achieved, the isolette and contained HRN are transported to the
airport for the initiation of air transport. Once airborne, the transport's
success depends mainly on maintaining the stabilization of the HRN by appro-
priate in-flight monitoring and support of cardiopulmonary functions (33,63).

During air t.ansport of the HRN, environmental components with adverse
cardiopulmonary potential are the same as those encountered during air transport
of the HRPW. For two adjunct reasons, the HRN during transport is potentially
more vulnerable than the HRPW to environmental displacement of cardiopulmonary
functions. Because the HRN has a much smaller total mass, and a much larger
surface-to-mass ratio than the HRPW, the HRN will react more sensitively and

1

samt


arterial pH, Pacg,, and Pag, are usually available at the referring hospital dur-
ing preflight stabilization, they are not available during flight. If available,
in-flight monitoring of Pacog and arterial pH, as well as Pap,, could enhance the
titration control of Pio » assisted ventilation, and blood acId/base status. A
reduced, but still perfeétly adequate PI,,, could heip decrease the possible intra-
pulmonic risk of oxygen toxicity (1, 23,285, In the case of assisted ventilation,

a reduced but still perfectly adequate CPAP, could decrease the in-flight risk of
pneumothorax (20,42). The use of portable tcPagg monitors during HRN transport is
currently increasing. The measurement of arterial blood pH using a pH electrode
sensor is available in most hospitals. To cur knowledge, the transfer of pH
electrode technology to the flight environment has not occurred. The usually
present umbilical artery catheter could provide access to the blood for pH measure-
ment. Commercial sources of tcPag, monitors are currently attempting to produce

a similar instrument for monitoring tcPacg,. Since blood pH monitoring in che HRN
may remain a practical impossibility, the 3irection of pH changes could be usefully
inferred from tePagg, monitoring. The survival importance of initially correcting
acidosis and preventing its exacerbation during transport is reflected in mortality
statistics. Two studies reported that the mortality of transported neonates who
arrived with an arterial pH of < 7.2 was significantly higher than that of the
neonates with an arterial pH of > 7.2 (33,64). Obviously, technological advances
could play a major positive role in this area.

Another important oxygenation factor is the in-flight maintenance of
cardiovascular functions in the HRN. Both arterial BP and HR are usually moni-
tored via transducers at the entrance site of the umbilical artery catheter. The
HR should approximate 120 to 160 beats per minute (bpm), and mean arterial pres-
sure (MAP) should approximate 40 to 50 torr (31). Simultaneous bradycardia (< 100
bpm) and hypotension (MAP < 30 torr) could indicate hypovolemia and/or hypoglycemia
(31). Ostensibly, both should have been corrected during the preflight stabiliza-
tion period. During transport, hypotension could resuit from decreased venous
return caused by a pneumothorax (31). In this regard, specific caution is exer-
cised against the use of excessive pressure during CPAP ventilation of the neonate
with congenital heari disease (10,52,73). Since hypoperfusior. can produce rapid
hypoxemic Jeterioration of the HRN, rapid counteractions to bradycardia and hypo-
tension are indicated. Technically, monitoring HR and BP in the HRN during trans—
port has posed few if any problems to our conferees.

3. Environmental Temperature. The maintenance of an NTE for the HRN
during transport is also a critical survival factor. Several studies have
reported that the mortality rate of transported neonates who arrived with rectal
temperatures of < 35.5° Celsius (C) was significantly greater than that of
the neonates with arrival rectal temperatures of > 35.5°C (33,64). Most trans-
port aircraft have adequate heating systems. The heating capabilities and temp-
erature control systems of several new-generation isolettes are considered to be
generally excelient (33,63). Instability of the internal biological temperature
controls (4,23,69}, and the high surface-to-mags ratio (47) are the two main
reasons for the HRN's hypothermic and hyperthermic vulnerability. Uncorrected
hypothermia or hyperthermia can entrain a rapid chain of adverse effects. Inad-
vertent cooling or overheating of the HRN usually causes a significant increase
in metabolic oxygen consumption. As increased metabolism lowers Pag., raises
Pacog> and lowers pH, it preduces an increased ventilatory drive. The presence

13



ACKNOWLEDGMENT

The authors acknowledge the major contributions of all medical
personnel who participated in this study by providing oral and
published information. The authors would also like to acknowledge
the excellent work of Mrs. Donna Fitzgerald in preparation of the

manuscript.

ii



30.

31.

32.

33.

34.

35.

37.

38.

39.

40.

41.

42.

43.

44,

45.

46.

Gluck, L., M. V. Kulovich, R. C. Borer, Jr., P. H. Brenner, G. G. Anderson,
aud W. N. Spellacy: Diagnosis of the Respiratory Disease Syndrome by Amnio-—

centesis, Am. J. Obstet. Gynecol., 109:440- 445, 197i.

Gregory, G. A.: Resuscitation of the Newborn, Anesthesiology, 43:255-239, 1975.

Gregory, G. A., J. A. Kitterman, R. H. Phibbs, W. H. Tooley, and W. K.
Hamilton: Treatment of the Idiopathic Respiratory Distress Syndrome with
Continuous Positive Airway Pressure, N. Engl. J. Med., 284:1333-1340, 1971.

Hackel, A.: A Medical Transport System for the Neonate, Anesthesiology, 43:
258-267, 1975.

Hackel, A.: Discussion: Physiologic Factors in Air Transport. In Maternal
Air Transport Conference, S. N. Graven (Ed.), Mead Johnson Co., 1979, p. 59.

Hackel, A.: Infant Environment and Monitors. In Newborn Air Transport
Conference, S. N. Graven (Ed.), Mead Johnson Co., 1978, pp. 45-51.

Hacke? A.: Ventilation. In Newborn Air Transport Conference, S. N. Graven
(Ed.}, Mead Johnson Co., 1978, pp. 52-54,

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Harris, T. R.: Outcomes of Maternal Air Transport. In Maternal Air Transport
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Honeyfield, P. R
Conference, S. N

: Staffing for Newborn Transport. In Newborn Air Transport
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Technica! Report Oocumentation Page

1." Report No.

2. Government Accession No. 5. Reciprent's Corelog No.
FAA-AM-82-% _

= £
4. Tithe ond Subnile

Evaluation of Cardiopulmonary Factors Critical to

Successful Emergency Perinatal A‘r Transport.

yo

5. Repart Care
March 1982

[6 Performing Orgenization Code

|B. Performing Organizotion Report No.

Author's)

M. T. Lategola and M. Flux

| 9 Performing Orgonization Nome and Address

FAA Civil Aeromedical Institute
P.O. Box 25082

Oklahoma City, Oklahoma 73125

10. Work Unit No. (TRAITS)

TT. Contract or Grant No.

13. Type of Report and Period Covered

. Sponsoring Agency Nome ond Address:
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, SW.
Washington, D.C. 20591

. Supplementary Notes

OAM Report

Té Sponsoring Agency Code

Work was done under approved Task AM-A-81-PHY-127.

16. Abstract

-Regionalization of specialized perinatal care is a fully viable and progressing
concept. The two major components of regionalized care are the level III care
facility and the air transport service. In descending importance, the medical
transport team, the pilot and aircraft, and related technology and equipment are
the three most importaut components of the transport service. Although signifi-
cant reductions in perinatal morbidity and mortality have already resulted from
development of regional care, additional progress is possible and desirable.
Areas of possible improvement are: earlier precrisis diagnosis of maternal and/
or fetal risk at level I care; supplementary training of medical transport person-
nel in perinatal aspects of Aviation Medicine, Physiology, and Safety; technclogy
of preflight stabilization of the pregnant mother or the neonate; adjunct iaedical

ment and methods.

training of transport pilots; exclusive use of multiengine, fixed-wing, all-
weather aircraft; and technology of in-flight life support and monitoring equip-

17, Key Words

High risk pregnant woman, High risk
neonate, Emergency air transport, Cardio-|
pulmonary factors, Medical transport team,
Fixed-wing aircraft, Helicopters, Region-|
alized perinatal care.

18. Distribution Statenent
Document is available to the public
through the National Technical
Information Service, Springfield,
Virginia 22161.

19. Security Classif. (of this report)

Unclassified Unclassif

D. Security Clossif. (of tts poged

21. No. of Poges

24

22. Price

ied

Form DOT F 1700.7 (8-72)
i

Reproduction of completed page cuthorized



fixed-wing aircraft (70). All medicai transport persornel consider auscultative
monitoring in the flight environment to be practically useless. Moppler equip-
ment is used routinely to monitor fetal heart activity. A commercially avail-
able BP apparatus, which substitutes Doppler blood flow sensing for Korotkov
sound detection and provides a visual digital readout, could be quite useful in
the flight environment. Thie method is capable of measuring BP even during cir-
culatory shock with low blood flow.

Medical transport personnel have reported that noise and vibration
during transport play an important role in producing headache, visual and audi-~
tory fatigue, air sickness, irritability and anxiety in the HRPW (9,42). Noise
levels encountered in air transport (especially in helicopters) are considered
to be auditorily in a potentially hazardous range (76). Although repeated expo-
sures could be auditorily harmful (14), single exposures are considered harmless
(33). Definitive studies on specific noise and vibration effects in the HRPW
and fetus have not been done. The conferees agree chat the desirability of min-
imizing noise and vibration favors the transport use of mitiengine, fixed-wing
aircraft.

Vi. EMERGENCY NEONATAL AIR TRANSPORT.

A. Preferability of "In Utero" Transport. As mentioned previously, “in

utero” fetal transport with subsequent delivery and neonatal intensive care in

a level 11I facility is preferable to delivery in a level I facility with sub-
sequent neonatal transport to the level III facility (33,38,45,61,67). Early
detection of risk in the HRPW or fetus, and early, unhurried transport to a

level III facility is highly desirable. Early detection of risk may depend on

an alerting medical history of disease and/or previous complicated pregnancy

(29). When a maternal medical history indicates the possibility of a premature
delivery, one component of potential fetai risk can be assessed. This component,
which is the most prevalent risk in the premature neonate, is respiratory disease
syndrome (RDS) (2,18,20). This risk is primarily related to insufficient produc-
tion of surface-active (surfactent) material needed to keep alveoli open to air
exchange (3). Surfactant, produced in the lung, begins to reach alveolar surfaces
around 26 to 28 weeks of gestation (31). A lecithin/sphingomyelin ratio (L/S)

of > 2.0 in sampled amiotic fluid usually indicates sufficient maturity of the
surfactant-producing system (25,30) When premature birth is considered to be
highly probable, a concomitant L/S ratio of < 1.5 (indicating pulmonary immaturity)
should signal the need for that premature birth to occur at a level III facility.

In the presence of an otherwise normal pregnancy, early detection of
fetai risk, per se, is very difficult at best (15). Fetal HR (Doppler monitored)
and fetal activity are two important assessable functions during the third tri-
mester (72). Because HRN's are not always detectable before birth, a substantial
percentage of them will continue to be born at level I facilities and require
subsequent transport to level III facilities (8,45,61,63,67).

B. The Transport “solette Incubator. When transported "in utero," the
fetus is provided with an ideal environment in its "biological" incubator. When
premature birth has removed the HRN from the maternal incubator, an isolette
incubator has to provide and monitor adequate substitutes for the intrauterine



rapidly to environmental changes. Further, the HRN does not have the capability
to orally communicate to medical transport personnel any adverse symptoms as
soon as they occur.

1. Hypobarism. Neonatologists (including conferees) universally agree
that all adverse hypobaric effects of air transport (9,16,23) could be prevented
by exclusive use of pressurized aircraft. If the HRN'’s preflight condition is
considered to be excellent and stable, a maximum cabin altitude of 6,000 ft is
considered tolerable for transport (9,49). If higher altitudes are anticipated,
the use of pressurized aircraft is strongly recommended (9). in the presence of
any entity such as pneumothorax, pneumomediastinum, aspiration syndrome, dia-
phragmatic hernia, ileus, bowel obstruction, esephageal atresia, and tracheo~
esophageal fistula, the use of a pressurized aircraft is strongly advocated (42,
47,54,69). Hypobaric expansion of a gas pocket associated with any of these
entities is still possible in unpressurized flight despite preflight tube vent-
ing of the gas pocket (10). Substantial expansion of any such gas pocket during
transport may mechanically compromise respiration and/or circulation, and pos-
sibly cause tissue rupture with subsequent sepsis (10,42).

2. Hypoxia. Oxygenation of the HRN during transport is considered a
critical survival factor. Proper oxygenation of the HRN depends on many factors.
One of these is the provfsion of an adequate Ptp,. Because prolonged ventilation
of a neonate with high Fy, ‘s entails a possible’risk of retrolentil fibroplasia
(23,31,35,54,69), depress¢én of surfactant synthesis (24), and bronchopulmonary
dysplasia (1,23), oxygen is used as conservatively as conditions permit. Ideally,
a minimum Pag, of 50 to 80 torr is desirable (31). Many of our conferees are cur-
rently using tcPag, monitors during transport to titrate the adequacy of the Pigg:
The tcPagg monitor is usually "calibrated" by pretransport arterial blood gas
measurements of Pag,. Because Py, is a function of ambient pressure, the use
of a tcPap monitor to regulate che blended value of Fy, during unpressurized
flight can be very important. In the case of severe Roe? in which both a positive
pressure for ventilation (e.g., CPAP) and a > 0.7 Fig, may be needed, the tePago
can be useful in titrating the Fig, to minimize the risk of pulmonary oxygen
toxicity (24). During air transpoft, about 45 percent of all HRN'’s require some
form of assisted positive pressure ventilation (36). Although conferee use of
the tcPag.. monitor is increasing, they reported that this technology is not
trouble ffee. Maintenance of the Clark electrode sensor requires some degree
of experience. However, most conferees agree that the monitoring importance of
the Pagy exceeds the trouble of technological problems. For many practical
reasons, ear oximetry monitoring of arterial oxygen saturation in the neonate
is not feasible at this time (46).

Another important oxygenation factor is the maintenance of acid/base
balance in the HRN. In a respiratorily distressed HRN, a resulting acidosis is
highly probable. Initial measurements of arterial pH, Pago, and Pao. are impor-
tant because, in the uncompensated presence of an acidotic pH and an elevated Pacoo>
intrapulmonic oxygen loading is impeded by an acidotic shift in the HbO2 curve
(64). For any desired Pap., a higher P would be required to load the oxygen
into acidotic blood than ifito blood with 2 normal or alkalotic pH (58). Further,
in the same uncompensated acidotic condition, an oxygenated “pink” infant could
incur rapid deterioration via C02 narcosis (20,23). Although measurements of

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