AUTONOMIC
FUNCTION
IN
THE
NEONATE
VIII.
Card ioPuImonary
Observations
Earle L. Lipton, M.D., Alfred Steinschneider, Ph.D., M.D.,
and Julius B. Richmond, M.D.
Department of Pediatrics, State University of New York, Upstate Medical Center, Syracuse, New York
(Submitted March 22; revision accepted for publication October 1, 1963.)
Supported in part by a grant from the United States Public Health Service, MI-I 04605.
ADDRESS: (J.B.R.) 766 Irving Avenue, Syracuse 10, New York.
PEDIATRICS, February 1964
212
D
URING TIlE STUDY of regulatoryproc-esses of the autonomic nervous
sys-tern in newborn infants observations have
been made which relate to
cardio-pulmo-nary interaction. It is the purpose of this
presentation to record briefly observations
of sinus arrhythmia and the cardiac
re-sponses to such physiological processes as
defecation, yawning, and hiccuping in
new-born infants as well as to the passage of a
nasogastric tube for feeding in premature
infants.
The experimental sessions during which
these physiologic processes were noted
gen-eraily focused on the study of individual
differences in autonomic nervous system
regulatory activity, maturational changes,
and sensitivity to sensory 2 These
studies have necessitated the adaptation of
the newer electronic monitoring instruments
for continuous polygraphic recording
with-out causing discomfort to the infant. The
continuity of the recordings over
consider-able periods of time have facilitated the
ob-servations now being reported.
MATERIALS
AND
METHODS
Forty-two babies less than 5 days but
be-yond 24 hours of age were studied during
a total of 131 separate sessions in our
labo-ratory for the study of autonornic function.
Each study session lasted approximately
two hours and began immediately
post-prandial. This laboratory provides a
con-trolled environment which maintains
con-stancy of temperature (78#{176}F.), sound,
light, and humidity (40%).
Heart rate is recorded by means of a
Fels cardiotachometer which gives an
in-stantaneous reading of cardiac rate after
each cardiac cycle. This is accomplished by
sensing the occurrence of successive “R”
waves in the EGG, converting each of these
time intervals to rate (beats per minute)
and recording it on a polygraph. Thus it is
possible to note small and instantaneous
variations in cardiac rate tilat might be
overlooked on visual inspection of the
standard EGG. Furthermore, the technique
allows for measurements of cardiac rate in
infants who are hyperactive and/or crying
vigorously. A more complete description
and approach to data analysis is presented
in previous publications:’
Respiration is recorded by means of a
small thermistor bead placed adjacent to
one of tile nares. Variations in temperature
between inspired and expired air are
de-tected and recorded, providing a graphic
picture of the rate and depth of respiration.
A paper strain gauge attached to the base
of the crib in which the baby lies provides
a record of gross motor movement.
Although the babies were presented with
a variety of sensory stimuli during the
experimental sessions, the observations
ported in this paper were made during
time periods when there was no external
stimulation.
RESULTS
Sinus Arrhythmia
Sinus arrhythmia, periodic variation in
ARTICLES 213
was recognizable in all the infants studied.
Marked differences were noted between
in-fants both in the frequency of sinus
arrhyth-mia as well as its magnitude. In Figure 1
a typical pattern in the newborn period is
illustrated. Generally this arrhythmia has
been considered rare in the neonatal period,
probably because it is so difficult to detect
from conventional EGG recordings at the
relatively high heart rates characteristic of
early infancy. The cardiotachorneter
facili-tates easy detection. Sinus arrhythmia is
currently being studied more thoroughly,
particularly to note consistency within
in-dividuals and the changes occurring during
the first six months of life.
Defecation
The cardio-pulmonary phenomenon
as-sociated with bowel evacuation was
suffi-ciently characteristic in some infants to
en-able the investigators to “diagnose” the
event by observing the ongoing polygraph
record in the adjacent room. In Figure 2a
the record of a newborn infant during
def-ecation illustrates intermittent respiratory
pauses associated with immediate
brady-cardia. The most striking example, depicted
Resprotions
SINUS ARRHYTHMIA
Time
- 80 (-5 s.c -#{149}
22 119
‘I, 4, -ISo
Cardiolochometer
‘1 1’ t
98 99 99 - -60
ECG
ThThThmTkThTh
Fic. 1. Sinus arrhythmia in a 2-day-old baby. There are increment changes of 24 beats per
min-ute within one respiratory cycle. This baby con-tinued to show marked sinus arrhythmia when tested at 2 months and 5 months of age although
at higher heart rate levels.
---..#{176}. 6-1 s. -5
Fic. 2. (a) Cardiac and respiratory changes noted
during defecation in a 2-day-old infant. Vertical
arrows indicate behavioral evidence of straining.
(b) Recording during defecation in a 5-month-old baby, causing dramatic bradycardia-160 to 80 within two beats. The widening of the R-R inter-val in the ECG on the bottom channel can be seen,
but is not as striking as the change shown by the
cardiotachometer.
in Figure 2b, occurred while studying a
5-month-old infant. On several occasions the
heart rate fell from approximately 160 to
80 beats per minute within 2 cardiac cycles.
Hiccup
A hiccup is a sharp involuntary
contrac-tion of the diaphragm causing a beginning
inspiration which is suddenly checked by
closure of the glottis. It occurs frequently
in infants without apparent cause.
Hiccups were noted in 17 of the babies
at some time during the periods of
observa-tion. All but one showed a characteristic
cardiac pattern. Within one cardiac cycle
following the diaphragmatic spasm there
is usually a drop in heart rate. In Figure 3
it may be noted that the cardiac rate
dropped as much as 33 beats per minute
during the course of one hiccup “cycle.”
Infants showed variation in the
van-..\
Mos AcPi,Iy
Fic. 3. Polygraph tracing of hiccups in a 2-day-old infant. Fofloving each hiccup (shown by an elon-gation of the downward phase of
respiration-in-spiratiom-ancl an increase in movement) there is
an immediate drop in heart rate.
ation did not seem to be dependent upon
cardiac rate at the time of the hiccup.
Yawn
Movement
Resprohon
5---.-,
YAWN
Caiotochometer8O
ECG
90
60
A yawn is primarily a deep involuntary
inspiration made with the mouth open. It is
often associated with transient bradycardia,
more gradual than seen with hiccuping.
(
Fig. 4). The lowest rate is usuallyachieved between two to five seconds
foi-lowing the beginning of the yawn. A total
of 59 separate yawns were recorded in 24
babies. In all but two of these occasions,
tile infant manifested some degree of
brady-cardia during the yawn.
Nasogastric lntubation
While recording responses in three very
small premature infants (not included in
the series of 42 babies), observations were
made during intermittent nasogastnic
in-tubation for feedings. These infants ranged
in weight from 740 gm to 1200 gm.
In-stances of very abrupt bradycardia, as seen
in Figure 5 often (but not invariably)
ac-companied the passage or presence of the
tube in the esophagus. In this case the rate
decreased from 170 to 55 beats per minute
in 5 seconds, returning to a rate of 170 in
another 10 seconds.
COMMENT
Since regulation of candio-pulmonary
fullction is critical for survival, it is striking
that there are so few reports concerning
autonomic control processes in early
in-fancy. The literature which is available is
based largely on speculations derived from
Fic. 4. Yawn recorded in a one-day-old infant.
Heart rate decreased from 140 to 102 beats per
minute in 1.5 seconds.
animal experimentation. The availability of
safe and comfortable methods for recording
autonomic nervous system activity should
result in more vork in this field.
It is to be noted that our data are largely
descriptive and provide little explanation
for the pilenomena reported. There is
evi-dence for a wide range of autonomic reflex
activity involving a variety of afferent and
efferent neural pathways. The participation
of vagal efferents in these reflexes is clearly
implied.
It might be hypothesized that tile cardiac
changes often associated with yawning,
def-PASSAGE OF
NASOGASTRIC TUBE
Respirations
ITO 0
::
‘---rrr
ECG Fic. 5. Passage of a nasogastric tube in a 990-gm
premature infant (age 1:3 (lays). The heart rate
decreased from an initial level of 170 beats per
ARTICLES 215
ecation, and intubation are the
conse-quence of arrested respiratory activity and
secondary hypoxia. However, the rapidiy
of tile response and repeated observations
in the laboratory of periods of apnea of 20
or more seconds duration in babies in the
first months of life without any shift in
cardiac rate does not support this
hypothe-sis.
Defecation probably affects cardiac rate
change through complex cardiovascular
pressure and respiratory changes vhicll in
turn influence vagal activity. It is currently
planned to monitor blood pressure
con-tinuously during this activity. It was at first
considered that these changes were simply
associated Witll a Valsalva-like maneuver
during defecation. However, the expiratory
effort in the Vaisalva maneuver in adults is
commonly associated with a tachycardia
whereas the cardiac change noted with
def-ecation is a bradycardia.
Evidence is available to indicate that
diaphragmatic proprioceptive stimulation
exerts an influence upon subsequent
res-5 Such a feedback mechanism could
certainly play a role in the cardiac reflex
slowing noted during a yawn as well as a
hiccup. The more gradual bradycardia
de-veloping during a yawn, in comparison to
a hiccup, could be a reflection of the
differ-ences in the propnioceptive stimulus as well
as pressure changes within the pleural
cav-ity.
Present studies in this laboratory are
de-signed to permit comparisons of infants
with respect to the magnitude and timing
of their cardiac, respiratory, and motor
re-sponses to a variety of standardized stimuli.
It is planned to relate patterns of responses
to external stimuli in individual infants with
the evoked and spontaneous reflex behavior
described in this paper. Through such
re-lated observations it may be possible to
identify individuals with a tendency toward
extreme reflex activity. It seems
appropri-ate to speculate whether maturational
changes in autonomic control mechanisms,
or idiosyncratic reflex activity play a role
in such pathologic conditions as cardiac
arrhytilmias, and unexplained sudden death
in babies.#{176} Recent animal studies support
such speculation.7
SUMMARY
Forty-two babies under 5 days of age
were observed for prolonged periods in a
laboratory with instruments which
mark-edly facilitate detection of cardiac rate and
respiratory changes. Many newborn infants
often manifest remarkable cardiac slowing
associated with such diverse activities as
hiccups, yawning, and defecation. The
nasogastric intubation of premature infants
has, at times, been followed by abrupt
bradycardia. Sinus arrhythmia is a frequent
occurrence. These seemingly diverse
ob-servations have implications for
develop-mental physiology and may be relevant to
some pathologic conditions unique to this
period of life.
REFERENCES
1. Lipton, E. L., Steinschneider, A., and Richmond,
J. B. Autonomic function in the neonate: IV. Individual differences in cardiac reactivity. Psychosom. Med., 23:472, 1961.
2. Lipton, E. L., Steinschneider, A, and Richmond,
J. B. Autonomic function in the neonate. VII.
Maturational changes in cardiac control. In preparation.
3. Lipton, E. L., Steinschneider, A., and Richmond,
J. B. Autonomic function in the neonate. III.
Methodological considerations. Psychosom.
Med., 23:461, 1961.
4. Goldberg, H., Elisberg, E. I. and Katz, L. N. The effects of the Valsalva-like maneuver upon the circulation in normal individuals
and patients with mitral stenosis. Circulation, 5:38, 1952.
5. Oberholzer, B. J. I-I., and Tofani, W. 0. The neural control of respiration, in Field, J.,
Handbook of Physiology, Section I. Neuro-physiology, Vol. II. Washington, D.C.: Amer. Phys. Society, 1960.
6. Allen, R. J., Towsley, H. A., and Wilson, J. L.
Neurogenic stridor in infancy. Amer. J. Dis.
Child., 87:179, 1954.
7. Preston, J. B., McFadden, S., and Moe, C. K.
Atrioventricular transmission in young
