Investigation of hot flashes by ambulatory monitoring GEORGE W. MOLNAR Veterans Administration
Medical
Center, Little
MOLNAR, GEORGE W. Investigation of hot flashes by ambulatory monitoring. Am. J. Physiol. 237(5): R306-R310, 1979 or Am. J. Physiol.: Regulatory Integrative Comp. Physiol. 6(3): R306-R310, 1979.-The unpredictability of hot flashes makes their investigation difficult. A method for continuous monitoring of subjective arousals and their objective correlates is here described and illustrated with results from one subject. Temperatures of special interest with respect to hot flashes-toe, cheek, vagina, and air- were recorded on a portable magnetic tape during routine living at home. The subject signaled the “on” and “off” of each perceived flash with a hand switch and also entered information in a notebook. She signaled 63 flashes on 5 days, during which the cheek and toe temperatures showed transient increments. Some of the flashes were labeled uncertain in the notebook. The subject also had 23 episodes of these temperature increments that she did not identify by signals as flashes. In these episodes, therefore, the mechanism of consciousness was not activated. Perceptions that coincided with transient temperature increments thus ranged as follows: subconscious, uncertain, definite but bearable, mildly distressful, and strongly distressful. Hence ambulatory monitoring can provide objective evidence of transient activation of the hypothalamic heat loss mechanism, whether perceived or not. body temperature;
menopause;
thermoregulation
Rock, Arkansas
72206
uous recording was possible with a 120-min tape and one set of mercury cells. Readout was accomplished by means of a playback unit and an ECG polygraph. A calibrator established fixed points on the readout chart to which the calibration scale was positioned. This scale was prepared for each harness and tape recorder unit by immersion of the thermistors in a vacuum bottle provided with a standard mercury thermometer. A thermistor sensor was applied with adhesive tape to the prominence of a cheek and another one to the inside of a big toe. To prevent slippage by tugging, the wire was looped around the base of the toe and taped to the dorsum of the foot. For the internal temperature, a third sensor was taped to a tampon and inserted into the vagina.’ Again to prevent slippage, a loop of the wire was taped to the abdomen. The fourth sensor, which was surrounded by an open guard, was pinned to a lapel for air temperature. A hand switch interrupted the air temperature circuit to produce a downward spike on the readout chart as a signal of clock time and of the onset and cessation of each flash. The subject also carried a small notebook for entries of the occurrence of flashes and information about her feelings and activities. RESULTS
EPISODIC
ABERRATIONS
OF THERMOREGULATION human being are hot flashes, which are experienced
in the most
commonly by menopausal women. Their basic physiology has been scarcely investigated, in part because they occur unpredictably. Much time can be wasted in a laboratory waiting for one to happen. There is a need for an ambulatory device that can record useful correlates of hot flashes as they occur naturally during ordinary living. An objective manifestation of a hot flash is the sudden transient peripheral vasodilatation evidenced as transient rapid warming of the digits and cheeks (5). These episodes can be registered by continuous recording of temperatures on a portable device available commercially (Medilog 4-24, Ambulatory Monitoring, Ardsley, NY). MATERIALS
AND
METHODS
Figure 1 is a photograph of the components of the monitoring ensemble: harness of four thermistors (one on a tampon) and a hand switch, tape recorder, carrying case with waist belt, and notebook. The recorder unit contained four amplifiers, four mercury cells, a motor, and an ordinary cassette of magnetic tape. A 24-h contin-
Figure 2 shows the readout on a slow chart of the first recording obtained. The downward spikes from the air temperature curve signal the occurrence of 11 flashes on this day. The subject was the same person as in the previous study (5). She tape-recorded 63 flashes on 5 days (lo-16 flashes/day). These flashes occurred in association with various activities and during sleep at night (11 times, each of which awakened her). Except during sleep at night, flashes did not always occur with repetition of particular activities such as meals or walking. As examples on a faster readout chart, Fig. 3 shows the occurrence of 6 flashes in 3.75 h, from 1920 to 2305 h on another day. They were flashes 3-8 of the 11 flashes for the day. Flashes 3,4, and 8 were rated as weak, flash 6 as mild. The other two were not rated. FZash 5 occurred while the subject was eating ice cream, flash 6 while she was watching television, and flash 7 while she was performing yoga exercises. FZash 6 occurred after she had gone to bed but before going to sleep. ’ The tampon used by the subject and shown in Fig. 1 &as a sticktype tampon (heavy duty). In a high vaginal vault, two of these tampons or an o.b. (super plus) may be necessary to keep it from sliding to the orifice and thereby reducing the temperature of the sensor.
R306
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
AMBIJLATORY
MONITORING
OF
HOT
R307
FLASHES
Figure 4 documents a “psychogenic” flash, i.e., one occurring in association with a “psychological” situation as opposed to a “psychophysiological” one such as sudden noise stimulating a startle reflex. In this instance the
FIG.
corder,
1. Components of the monitoring carrymg case, and notebook.
ensemble.
hxnrss,
tape
re-
subject was sitting at her loom weaving. She discovered a mistake that required unraveling. During the resulting frustration and annoyance, she began to flash. As Fig. 4 further shows, the psychogenic flash was followed by four temperature increments of cheek and toe over a period of about 2 h without concurrent signals of flashing. There were no entries in the notebook of associated activities, except eating supper during which the third unsignaled increment started. There were 23 instances of these unsignaled increments that mimicked the 63 increments accompanied by signals of flashing. Thus, of the total of 86 transient cheek and toe temperature increments, roughly 75% were accompanied by signals of flashing and 25% were not accompanied by signals. The subjective intensity of the flash experience was noted by the subject on 20 occasions. The categories were strong, mild, weak, and uncertain. The last denoted uncertainty as to occurrence, not as to category. Figure 5 shows an example of an uncertain flash. The associated
3s” 34O 33O 32O
36' 34O 32'
4o"
Air
35" 30 25' 2o"i
FIG
h. Other
T? : . '
II 1 14
I 16
I 18
2. Example of readout of a tape recording on a slow chart. spikes slgnaled hot flashes. Spike on vaginal temperature
1 I 20 22 CLOCK TIME First downward curve occurred
spike from with change
I 24 air temperature of tampon.
I 02 curve
I 04 signaled
clock
1 06 time
of 1130
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
R308
G. W.
8 I,, llllllllllllllrrlllrrrl Minutes
“‘!
lilllliillll
MOLNAR
11111111111111111111 m
Vagina
38"
-
F
-
37”
t
35O
Cheek
r
32”
Toe
3o” 28’ 26” 24O
35O
Air
3o”
I:.”
I ‘rl;r” /19:
--p 15
- 20:
4 00
8
w
--Ii-r..
-
8
22:oo
I 23~05
22:30
CLOCK TIME FIG.
watching
3. A sequence within 3.75 h of 6 flashes, television, and flash 7 while performing
nos. 3-8, of 11 flashes yoga exercises.
in 1 day.
temperature increments were obviously certain and definite: for the cheek, from 32.1 to 326°C; for the toe, from 30.4 to 33.4OC. The bar graphs of Fig. 6 relate intensities to mean vaginal and mean maximal cheek temperatures. They suggest that intensities increased with internal and cheek temperatures, but only the difference between uncertain and strong was statistically significant. The interval between the “on” and “off” signals for 55 flashes (the subject failed to signal off for 8 flashes) averaged 3.2 (1.1-6.1) min. The error was mostly in the sensing of the off moment. The subject was usually uncertain of the end point of her feeling of hotness. Figure 7 shows that the longest flash (6.1 min), which was rated strong, was actually a multiple flash of three components in overlapping succession. The next flash (also strong) about 0.5 h later had only one component and lasted 2.8 min. The relation of flashing to internal temperature (36.1.
FZash
5 occurred
while
subject
was eating
ice cream,
flash
6 while
385°C) was random. The mean, median, and mode were about the same: 37.3.37.4”C. The relation of flashing to toe temperature (20.236.2”C) and to cheek temperature (29.0.34.4”C) at the start of the flash was also random. The increment in temperature, however, was inversely related to the temperature at the start of the flash: for the toe, r = -0.892, P c 0.001; for the cheek, r = -0.842, P < 0.001. DISCUSSION
Continuous ambulatory monitoring with a magnetic tape recorder provides capability for both objectivity and the study of all flashes of a day. In the previous report (5) the author had temperature measurements from 2 flashes/laboratory session, in this report, from an average of 13 flashes/24-h “session.” In addition, the continuous recording disclosed the occurrence of transient cheek and
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
AMBULATORY
38” 37
h
MONITORING
OF
HOT
R309
FLASHES
I
-
Vagina Cheek
Air
FIG.
flashes
4. Example of a psychogenic by signals from subject.
flash
followed
shortly
thereafter
by four
cycles
of cheek
and
toe temperature
increments
not identified
as
Uncertain
37
r
Minutes Vagina
Weak Mild Strong
6 12
I ,
16
-
36 Cheek 32 0 1
37 Vaginal
38
Uncertain Weak
34 0
37.5 Temperature
Mild
12.2
r r I
mln
13.0
min
Strong
8
min
32 0 32
30 0 E D Air
FIG. 5. Example of an uncertain hot flash. Subject signaled a short flash even though she doubted its occurrence (entered in notebook). Transient increments of cheek and toe temperatures confirm the flash.
32.5 Maximal
33 Cheek
33.5
.54
Temperature
FIG. 6. Relation of flash intensities to mean temperatures. Differences between temperatures of categories strong and uncertain are the only significant ones. Digits at ends of bars of upper graph indicate no. of flashes, of lower graph, mean duration of flashes.
toe temperature increments that did not lead to the arousal of the subject and her signaling of a flash episode. This finding from ambulatory monitoring, namely, that flashes occur more often than is registered by the mechanism of consciousness (attentive awareness and cognition), may be a very important discovery. The value of continuous recording was once reinforced when the investigator doubted whether the subject was
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
G. W.
R310 I
*I
, . *
* _______.___.._..----.____..-
.
_
Minutes
35"
r
”
cheek
34O \ \
33O 32O ~~
Air 30" 25' [[ 1
I
I
e n
20:15
19:35 CLOCK TIME
FIG. 7. Example of a flash with 3 overlapping components starting at arrows, perceived duration of composite 6.1 min. Flash at right has one component, perceived duration 2.8 min. Both rated strong. Intervening cycle unsignaled, perhaps because of perplexity, a common experience.
really flashing. Her flush was faint and her forehead was slightly damp to the touch, but her foot and hand felt cold to the touch. However, the readout later confirmed the signal of flashing. As shown in Fig. 3, flash 4, the subject’s toe at that time warmed 1.5” from 22.9 to 24.4”C. A hot flash can be considered to be the nearly simultaneous explosive activation of 1) the hypothalamic heat loss center (vasodilatation and sweating) and 2) the cerebral consciousness mechanism. Sometimes the latter in turn activates 3) behavioral heat loss reactions (e.g., fanning, removal of clothing). The factor causing the explosive deviation from normal thermoregulation is not known at this time. Lauritzen (3) has considered whether the factor could be thyrotropin-releasing hormone, since its injection can evo.ke a flashlike response within 0.5 min. Whatever the agent may be, the summation of multiple flashes (Fig. 7) suggests that it can be released in multiple bursts. The excessive heat loss persists for only a few minutes and no resultant significant fall in internal temperature ensues. (Persistent excessive heat loss of course brings on hypothermia (2).) In this study the activation of the consciousness mechanism took place only 75% as often as the activation of the hypothalamic center did. Nonactivation was not re-
MOLNAR
lated to the concurrent core temperature (35.9-37.6”C). Moreover, some of the time that consciousness was triggered the feeling of hotness was uncertain or weak. The uncertainty and intensity of hotness, however, were seemingly proportional to internal and cheek temperatures (Fig. 6). On the other hand there was never an instance of signaling that a hot flash was on without a concurrent rise in cheek and toe temperatures, i.e., concurrent activation of the hypothalamic center. The inverse correlation of the increment of cheek and toe temperature to temperature at the start of the flash results from the fact that, with cumulative equal increments in rate of blood flow, the rise in temperature becomes less and less (1). The increment of blood flow for a flash is probably the same when the temperature increases by 1.6” above 34OC as when it increases by 3.2” above 3O”c, although the latter gives a much -more . .. . strrkmg response curve. Although hot flashes occur with the greatest frequency among menopausal women, and hence are considered to be the consequence of ovarian involution, the problem is more complicated. As the author noted previously (5), the subject experienced hot flashes at the age of 18 after suffering a bad sunburn. Her menstrual history was normal and uneventful from 12 to 55 yr of age. McKinlay and Jefferys (4) have reported the occurrence of hot flashes among 28 premenopausal women with normal menses; some had as many as 8 flashes/day for 1 yr preceding the study. Men can also experience hot flashes. The author has studied the charts of two recently hospitalized patients. One of them, 53 yr old and under treatment for angina, “noted, for the past ten years, episodes of flashing, i.e., feeling very warm all over, and the onset of profuse sweating, unassociated with activity” or meals. Laboratory tests ruled out hypoglycemia, carcinoid syndrome, and pheochromocytoma. The other patient, 39 yr old and under treatment for essential hypertension, complained of flushing and hotness. His blood glucose level was normal. Ambulatory temperature monitoring of men, as well as women, might well reveal the occurrence of hot flashes that now pass ,unnoticed. It could &O capture, for the record, the occurrence of rare events such as repetitive b ursts of discharges by the hypothalamic heat loss center that summate in perception as one hot flash episode of extended duration . Received
12 September
1978; accepted
in final
form
22 May
1979.
REFERENCES M. C. FunctionaL Lower Extremities. Chicago,
Anatomy of the CircuZation to the IL: Year Book, 1971. 2. JOHNSON, R. H., AND D. M. PARK. Intermittent hypothermia: independence of central and reflex thermoregulatory mechanisms. J. Neural. Neurosurg. Psychiatry 36: 411-416, 1973. 3. LAURITZEN, C. The hypothalamic anterior pituitary system in the 1. CONRAD,
age period. Front. Horm. Res. 3: 20-31, 1975. S. M., AND M. JEFFERYS. The menopausal syndrome. Br. J. Prev. Sot. Med. 28: 108-115, 1974. 5. MOLNAR, G. W. Body temperature during menopausal hot flashes. J. Appl. Physiol. 38: 499403, 1975.
climacteric 4. MCKINLAY,
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
Medical
Center, Little
MOLNAR, GEORGE W. Investigation of hot flashes by ambulatory monitoring. Am. J. Physiol. 237(5): R306-R310, 1979 or Am. J. Physiol.: Regulatory Integrative Comp. Physiol. 6(3): R306-R310, 1979.-The unpredictability of hot flashes makes their investigation difficult. A method for continuous monitoring of subjective arousals and their objective correlates is here described and illustrated with results from one subject. Temperatures of special interest with respect to hot flashes-toe, cheek, vagina, and air- were recorded on a portable magnetic tape during routine living at home. The subject signaled the “on” and “off” of each perceived flash with a hand switch and also entered information in a notebook. She signaled 63 flashes on 5 days, during which the cheek and toe temperatures showed transient increments. Some of the flashes were labeled uncertain in the notebook. The subject also had 23 episodes of these temperature increments that she did not identify by signals as flashes. In these episodes, therefore, the mechanism of consciousness was not activated. Perceptions that coincided with transient temperature increments thus ranged as follows: subconscious, uncertain, definite but bearable, mildly distressful, and strongly distressful. Hence ambulatory monitoring can provide objective evidence of transient activation of the hypothalamic heat loss mechanism, whether perceived or not. body temperature;
menopause;
thermoregulation
Rock, Arkansas
72206
uous recording was possible with a 120-min tape and one set of mercury cells. Readout was accomplished by means of a playback unit and an ECG polygraph. A calibrator established fixed points on the readout chart to which the calibration scale was positioned. This scale was prepared for each harness and tape recorder unit by immersion of the thermistors in a vacuum bottle provided with a standard mercury thermometer. A thermistor sensor was applied with adhesive tape to the prominence of a cheek and another one to the inside of a big toe. To prevent slippage by tugging, the wire was looped around the base of the toe and taped to the dorsum of the foot. For the internal temperature, a third sensor was taped to a tampon and inserted into the vagina.’ Again to prevent slippage, a loop of the wire was taped to the abdomen. The fourth sensor, which was surrounded by an open guard, was pinned to a lapel for air temperature. A hand switch interrupted the air temperature circuit to produce a downward spike on the readout chart as a signal of clock time and of the onset and cessation of each flash. The subject also carried a small notebook for entries of the occurrence of flashes and information about her feelings and activities. RESULTS
EPISODIC
ABERRATIONS
OF THERMOREGULATION human being are hot flashes, which are experienced
in the most
commonly by menopausal women. Their basic physiology has been scarcely investigated, in part because they occur unpredictably. Much time can be wasted in a laboratory waiting for one to happen. There is a need for an ambulatory device that can record useful correlates of hot flashes as they occur naturally during ordinary living. An objective manifestation of a hot flash is the sudden transient peripheral vasodilatation evidenced as transient rapid warming of the digits and cheeks (5). These episodes can be registered by continuous recording of temperatures on a portable device available commercially (Medilog 4-24, Ambulatory Monitoring, Ardsley, NY). MATERIALS
AND
METHODS
Figure 1 is a photograph of the components of the monitoring ensemble: harness of four thermistors (one on a tampon) and a hand switch, tape recorder, carrying case with waist belt, and notebook. The recorder unit contained four amplifiers, four mercury cells, a motor, and an ordinary cassette of magnetic tape. A 24-h contin-
Figure 2 shows the readout on a slow chart of the first recording obtained. The downward spikes from the air temperature curve signal the occurrence of 11 flashes on this day. The subject was the same person as in the previous study (5). She tape-recorded 63 flashes on 5 days (lo-16 flashes/day). These flashes occurred in association with various activities and during sleep at night (11 times, each of which awakened her). Except during sleep at night, flashes did not always occur with repetition of particular activities such as meals or walking. As examples on a faster readout chart, Fig. 3 shows the occurrence of 6 flashes in 3.75 h, from 1920 to 2305 h on another day. They were flashes 3-8 of the 11 flashes for the day. Flashes 3,4, and 8 were rated as weak, flash 6 as mild. The other two were not rated. FZash 5 occurred while the subject was eating ice cream, flash 6 while she was watching television, and flash 7 while she was performing yoga exercises. FZash 6 occurred after she had gone to bed but before going to sleep. ’ The tampon used by the subject and shown in Fig. 1 &as a sticktype tampon (heavy duty). In a high vaginal vault, two of these tampons or an o.b. (super plus) may be necessary to keep it from sliding to the orifice and thereby reducing the temperature of the sensor.
R306
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
AMBIJLATORY
MONITORING
OF
HOT
R307
FLASHES
Figure 4 documents a “psychogenic” flash, i.e., one occurring in association with a “psychological” situation as opposed to a “psychophysiological” one such as sudden noise stimulating a startle reflex. In this instance the
FIG.
corder,
1. Components of the monitoring carrymg case, and notebook.
ensemble.
hxnrss,
tape
re-
subject was sitting at her loom weaving. She discovered a mistake that required unraveling. During the resulting frustration and annoyance, she began to flash. As Fig. 4 further shows, the psychogenic flash was followed by four temperature increments of cheek and toe over a period of about 2 h without concurrent signals of flashing. There were no entries in the notebook of associated activities, except eating supper during which the third unsignaled increment started. There were 23 instances of these unsignaled increments that mimicked the 63 increments accompanied by signals of flashing. Thus, of the total of 86 transient cheek and toe temperature increments, roughly 75% were accompanied by signals of flashing and 25% were not accompanied by signals. The subjective intensity of the flash experience was noted by the subject on 20 occasions. The categories were strong, mild, weak, and uncertain. The last denoted uncertainty as to occurrence, not as to category. Figure 5 shows an example of an uncertain flash. The associated
3s” 34O 33O 32O
36' 34O 32'
4o"
Air
35" 30 25' 2o"i
FIG
h. Other
T? : . '
II 1 14
I 16
I 18
2. Example of readout of a tape recording on a slow chart. spikes slgnaled hot flashes. Spike on vaginal temperature
1 I 20 22 CLOCK TIME First downward curve occurred
spike from with change
I 24 air temperature of tampon.
I 02 curve
I 04 signaled
clock
1 06 time
of 1130
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
R308
G. W.
8 I,, llllllllllllllrrlllrrrl Minutes
“‘!
lilllliillll
MOLNAR
11111111111111111111 m
Vagina
38"
-
F
-
37”
t
35O
Cheek
r
32”
Toe
3o” 28’ 26” 24O
35O
Air
3o”
I:.”
I ‘rl;r” /19:
--p 15
- 20:
4 00
8
w
--Ii-r..
-
8
22:oo
I 23~05
22:30
CLOCK TIME FIG.
watching
3. A sequence within 3.75 h of 6 flashes, television, and flash 7 while performing
nos. 3-8, of 11 flashes yoga exercises.
in 1 day.
temperature increments were obviously certain and definite: for the cheek, from 32.1 to 326°C; for the toe, from 30.4 to 33.4OC. The bar graphs of Fig. 6 relate intensities to mean vaginal and mean maximal cheek temperatures. They suggest that intensities increased with internal and cheek temperatures, but only the difference between uncertain and strong was statistically significant. The interval between the “on” and “off” signals for 55 flashes (the subject failed to signal off for 8 flashes) averaged 3.2 (1.1-6.1) min. The error was mostly in the sensing of the off moment. The subject was usually uncertain of the end point of her feeling of hotness. Figure 7 shows that the longest flash (6.1 min), which was rated strong, was actually a multiple flash of three components in overlapping succession. The next flash (also strong) about 0.5 h later had only one component and lasted 2.8 min. The relation of flashing to internal temperature (36.1.
FZash
5 occurred
while
subject
was eating
ice cream,
flash
6 while
385°C) was random. The mean, median, and mode were about the same: 37.3.37.4”C. The relation of flashing to toe temperature (20.236.2”C) and to cheek temperature (29.0.34.4”C) at the start of the flash was also random. The increment in temperature, however, was inversely related to the temperature at the start of the flash: for the toe, r = -0.892, P c 0.001; for the cheek, r = -0.842, P < 0.001. DISCUSSION
Continuous ambulatory monitoring with a magnetic tape recorder provides capability for both objectivity and the study of all flashes of a day. In the previous report (5) the author had temperature measurements from 2 flashes/laboratory session, in this report, from an average of 13 flashes/24-h “session.” In addition, the continuous recording disclosed the occurrence of transient cheek and
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
AMBULATORY
38” 37
h
MONITORING
OF
HOT
R309
FLASHES
I
-
Vagina Cheek
Air
FIG.
flashes
4. Example of a psychogenic by signals from subject.
flash
followed
shortly
thereafter
by four
cycles
of cheek
and
toe temperature
increments
not identified
as
Uncertain
37
r
Minutes Vagina
Weak Mild Strong
6 12
I ,
16
-
36 Cheek 32 0 1
37 Vaginal
38
Uncertain Weak
34 0
37.5 Temperature
Mild
12.2
r r I
mln
13.0
min
Strong
8
min
32 0 32
30 0 E D Air
FIG. 5. Example of an uncertain hot flash. Subject signaled a short flash even though she doubted its occurrence (entered in notebook). Transient increments of cheek and toe temperatures confirm the flash.
32.5 Maximal
33 Cheek
33.5
.54
Temperature
FIG. 6. Relation of flash intensities to mean temperatures. Differences between temperatures of categories strong and uncertain are the only significant ones. Digits at ends of bars of upper graph indicate no. of flashes, of lower graph, mean duration of flashes.
toe temperature increments that did not lead to the arousal of the subject and her signaling of a flash episode. This finding from ambulatory monitoring, namely, that flashes occur more often than is registered by the mechanism of consciousness (attentive awareness and cognition), may be a very important discovery. The value of continuous recording was once reinforced when the investigator doubted whether the subject was
Downloaded from www.physiology.org/journal/ajpregu by ${individualUser.givenNames} ${individualUser.surname} (128.059.222.107) on January 13, 2019.
G. W.
R310 I
*I
, . *
* _______.___.._..----.____..-
.
_
Minutes
35"
r
”
cheek
34O \ \
33O 32O ~~
Air 30" 25' [[ 1
I
I
e n
20:15
19:35 CLOCK TIME
FIG. 7. Example of a flash with 3 overlapping components starting at arrows, perceived duration of composite 6.1 min. Flash at right has one component, perceived duration 2.8 min. Both rated strong. Intervening cycle unsignaled, perhaps because of perplexity, a common experience.
really flashing. Her flush was faint and her forehead was slightly damp to the touch, but her foot and hand felt cold to the touch. However, the readout later confirmed the signal of flashing. As shown in Fig. 3, flash 4, the subject’s toe at that time warmed 1.5” from 22.9 to 24.4”C. A hot flash can be considered to be the nearly simultaneous explosive activation of 1) the hypothalamic heat loss center (vasodilatation and sweating) and 2) the cerebral consciousness mechanism. Sometimes the latter in turn activates 3) behavioral heat loss reactions (e.g., fanning, removal of clothing). The factor causing the explosive deviation from normal thermoregulation is not known at this time. Lauritzen (3) has considered whether the factor could be thyrotropin-releasing hormone, since its injection can evo.ke a flashlike response within 0.5 min. Whatever the agent may be, the summation of multiple flashes (Fig. 7) suggests that it can be released in multiple bursts. The excessive heat loss persists for only a few minutes and no resultant significant fall in internal temperature ensues. (Persistent excessive heat loss of course brings on hypothermia (2).) In this study the activation of the consciousness mechanism took place only 75% as often as the activation of the hypothalamic center did. Nonactivation was not re-
MOLNAR
lated to the concurrent core temperature (35.9-37.6”C). Moreover, some of the time that consciousness was triggered the feeling of hotness was uncertain or weak. The uncertainty and intensity of hotness, however, were seemingly proportional to internal and cheek temperatures (Fig. 6). On the other hand there was never an instance of signaling that a hot flash was on without a concurrent rise in cheek and toe temperatures, i.e., concurrent activation of the hypothalamic center. The inverse correlation of the increment of cheek and toe temperature to temperature at the start of the flash results from the fact that, with cumulative equal increments in rate of blood flow, the rise in temperature becomes less and less (1). The increment of blood flow for a flash is probably the same when the temperature increases by 1.6” above 34OC as when it increases by 3.2” above 3O”c, although the latter gives a much -more . .. . strrkmg response curve. Although hot flashes occur with the greatest frequency among menopausal women, and hence are considered to be the consequence of ovarian involution, the problem is more complicated. As the author noted previously (5), the subject experienced hot flashes at the age of 18 after suffering a bad sunburn. Her menstrual history was normal and uneventful from 12 to 55 yr of age. McKinlay and Jefferys (4) have reported the occurrence of hot flashes among 28 premenopausal women with normal menses; some had as many as 8 flashes/day for 1 yr preceding the study. Men can also experience hot flashes. The author has studied the charts of two recently hospitalized patients. One of them, 53 yr old and under treatment for angina, “noted, for the past ten years, episodes of flashing, i.e., feeling very warm all over, and the onset of profuse sweating, unassociated with activity” or meals. Laboratory tests ruled out hypoglycemia, carcinoid syndrome, and pheochromocytoma. The other patient, 39 yr old and under treatment for essential hypertension, complained of flushing and hotness. His blood glucose level was normal. Ambulatory temperature monitoring of men, as well as women, might well reveal the occurrence of hot flashes that now pass ,unnoticed. It could &O capture, for the record, the occurrence of rare events such as repetitive b ursts of discharges by the hypothalamic heat loss center that summate in perception as one hot flash episode of extended duration . Received
12 September
1978; accepted
in final
form
22 May
1979.
REFERENCES M. C. FunctionaL Lower Extremities. Chicago,
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