Breathing patterns before death in fetal lambs J.
E.
PATRICK,
M.D.,
F.R.C.S.(C.)*
K.
J.
DALTON,
B.Sc.,
M.B.,
G.
S.
DAWES,
Headington,
F.R.S.,
Oxford,
B.S.**
D.M.
England
Continuous observations in 1 Gfetal lambs over many days before death in utero from hypoxia, asphyxia, infection, and other causes have shown that death is preceded by variable changes in breathing movements. There was always a prolonged period of apnea succeeded by continuous abnormal breathing in six lambs and by gasping or brief episodes of abnormal breathing in the remainder. These abnormal patterns are described as a warning of what may be encountered in the human fetus.
THE HUMAN FETUS in utero, movements of the chest wall are normally present 55 to 95 per cent of the time.’ Gross diminution of fetal breathing movements, apnea, and apnea with gasping have been observed before fetal death in 12 instances. It has also been shown that in the antenatal period diminution of fetal breathing movements with the appearance of gasping may be used as a predictive indicator of the subsequent development of fetal distress in labor.‘, * However, clinical experience is still limited to less than 2,000 patients, and we cannot yet be sure that the appearance of apnea and gasping is the only sinister manifestation of impending fetal death. During the course of continuous recordings of fetal breathing movements in chronically catheterized lambs in utero.3 we sometimes observed respiratory and cardiovascular behavior before death similar to that subsequently seen in man, i.e., prolonged apnea
followed by an episode of gasping and subsequent cardiac arrest. However, during the past three years, on several occasions, other grossly abnormal patterns of fetal breathing movements have appeared in lambs for a day or two before death. These will be described, briefly, as a possible warning if they should be detected in the human fetus in utero.
IN
From the Nuffield Institute University of Oxford. Supported
by the Medical
for
Medical
Research
Methods Observations were made on 16 cross-bred fetal lambs which died, before the onset of labor, from infection (7), hemorrhage (2), toxemia (1) or hypoxia of uncertain cause (6). These lambs were at 108 to 139 days’ gestational age at the time of death. They were part of a group of 40 lambs which were otherwise studied until death or the onset of labor. All the lambs which died had been catheterized for 1 to 21 days previously (mean, 7 days). Continuous records were made of carotid arterial blood pressure, tracheal pressure, amniotic pressure, and heart rate by methods previously described.3
Research,
Council
of Great
Results
Britain. Received
for publication
Accepted
October
Reprint Institute
Oxford,
July
25,
In the normal fetal lamb in utero, during the last third of gestation, episodes of rapid irregular breathing movements occur at 1 to 3 Hz and are of variable amplitude, commonly 2 to 20 mm. Hg. The episodes may last from a few minutes to as long as 40 minutes and are associated with rapid eye movement sleep. There is a diurnal variation in these breathing movements,4 but, on an average over the 24 hours, they are present about 40 per cent of the time. It is exceptional, and probably indicative of a serious
1975.
2, 1975.
requests: Professor G. S. Daules, Nuffield for Medical Research, Headly Way, Headington, OX? 9DS, England.
*Supported by a Fellouahip from the Medical Research Couwil oj Cnnada. Prvserlt arldrm: Drpartw,rt of Ob.strtrics and Gywcology, U~~iwrsity of Westenr Otrtnrio,
I.ondon,
Ontario,
**,]unior Council
Research Fellow of Great Britain.
Canada. of the Medical
Research
73
74 Patrick, Dalton, and Dawes
Table I. Observations on fetal lambs with normal (mean + standard error)
or abnormal
patterns
of breathing
movements
Group
No. Gestational age range (days) Carotid
pattm-n
Duration, range (min.) Frequencyimin. Amplitude (mm. Hg) Duration of each breath (sec.) *Normal
I
2
3
50 95 - 147
6 113 - 124
8 106 - 137
2 123 - 131
values
Pao, (mm. Hg) Pace* (mm. Hg) PH Packed cell volume (%) Breathing
Normal*
values from 70 other experiments
23 45 7.35 33
zk 2 k 2
0.5 0.6 0.005 0.9
-
-
14 ” 0.0 59 t 1.2 7.04 t 0.4 31 t 1.5
Continuous 75 20.8 6.5 0.8
2 k k
1,800 2.5 1.2 0.3
13 1+ 2.0 64 t 4.3 7.10 t 0.005 39 2 3.6
Gasping 10 - 988 1.2 ? 0.2 2.8 ? 0.3 0.5 t 0.1
12 + 0.3 44 i 0.7 7.37 k 0.01 39 -?I 0.5
Episodic breathing/ gasping ,540 - 2,178 13 - 140 7 -- 30 0.2 -- l.Tr
on 50 fetal lambs in the same laboratory.
departure from normality, if these breathing movements are absent for an hour at a time. In addition, there are, from time to time, less frequent (1 to 4 per minute) deeper breathing movements, originally described as “gasps or sighs’13 but preferably termed “augmented breaths” unrelated to sleep state and normally present
E.
PATRICK,
M.D.,
F.R.C.S.(C.)*
K.
J.
DALTON,
B.Sc.,
M.B.,
G.
S.
DAWES,
Headington,
F.R.S.,
Oxford,
B.S.**
D.M.
England
Continuous observations in 1 Gfetal lambs over many days before death in utero from hypoxia, asphyxia, infection, and other causes have shown that death is preceded by variable changes in breathing movements. There was always a prolonged period of apnea succeeded by continuous abnormal breathing in six lambs and by gasping or brief episodes of abnormal breathing in the remainder. These abnormal patterns are described as a warning of what may be encountered in the human fetus.
THE HUMAN FETUS in utero, movements of the chest wall are normally present 55 to 95 per cent of the time.’ Gross diminution of fetal breathing movements, apnea, and apnea with gasping have been observed before fetal death in 12 instances. It has also been shown that in the antenatal period diminution of fetal breathing movements with the appearance of gasping may be used as a predictive indicator of the subsequent development of fetal distress in labor.‘, * However, clinical experience is still limited to less than 2,000 patients, and we cannot yet be sure that the appearance of apnea and gasping is the only sinister manifestation of impending fetal death. During the course of continuous recordings of fetal breathing movements in chronically catheterized lambs in utero.3 we sometimes observed respiratory and cardiovascular behavior before death similar to that subsequently seen in man, i.e., prolonged apnea
followed by an episode of gasping and subsequent cardiac arrest. However, during the past three years, on several occasions, other grossly abnormal patterns of fetal breathing movements have appeared in lambs for a day or two before death. These will be described, briefly, as a possible warning if they should be detected in the human fetus in utero.
IN
From the Nuffield Institute University of Oxford. Supported
by the Medical
for
Medical
Research
Methods Observations were made on 16 cross-bred fetal lambs which died, before the onset of labor, from infection (7), hemorrhage (2), toxemia (1) or hypoxia of uncertain cause (6). These lambs were at 108 to 139 days’ gestational age at the time of death. They were part of a group of 40 lambs which were otherwise studied until death or the onset of labor. All the lambs which died had been catheterized for 1 to 21 days previously (mean, 7 days). Continuous records were made of carotid arterial blood pressure, tracheal pressure, amniotic pressure, and heart rate by methods previously described.3
Research,
Council
of Great
Results
Britain. Received
for publication
Accepted
October
Reprint Institute
Oxford,
July
25,
In the normal fetal lamb in utero, during the last third of gestation, episodes of rapid irregular breathing movements occur at 1 to 3 Hz and are of variable amplitude, commonly 2 to 20 mm. Hg. The episodes may last from a few minutes to as long as 40 minutes and are associated with rapid eye movement sleep. There is a diurnal variation in these breathing movements,4 but, on an average over the 24 hours, they are present about 40 per cent of the time. It is exceptional, and probably indicative of a serious
1975.
2, 1975.
requests: Professor G. S. Daules, Nuffield for Medical Research, Headly Way, Headington, OX? 9DS, England.
*Supported by a Fellouahip from the Medical Research Couwil oj Cnnada. Prvserlt arldrm: Drpartw,rt of Ob.strtrics and Gywcology, U~~iwrsity of Westenr Otrtnrio,
I.ondon,
Ontario,
**,]unior Council
Research Fellow of Great Britain.
Canada. of the Medical
Research
73
74 Patrick, Dalton, and Dawes
Table I. Observations on fetal lambs with normal (mean + standard error)
or abnormal
patterns
of breathing
movements
Group
No. Gestational age range (days) Carotid
pattm-n
Duration, range (min.) Frequencyimin. Amplitude (mm. Hg) Duration of each breath (sec.) *Normal
I
2
3
50 95 - 147
6 113 - 124
8 106 - 137
2 123 - 131
values
Pao, (mm. Hg) Pace* (mm. Hg) PH Packed cell volume (%) Breathing
Normal*
values from 70 other experiments
23 45 7.35 33
zk 2 k 2
0.5 0.6 0.005 0.9
-
-
14 ” 0.0 59 t 1.2 7.04 t 0.4 31 t 1.5
Continuous 75 20.8 6.5 0.8
2 k k
1,800 2.5 1.2 0.3
13 1+ 2.0 64 t 4.3 7.10 t 0.005 39 2 3.6
Gasping 10 - 988 1.2 ? 0.2 2.8 ? 0.3 0.5 t 0.1
12 + 0.3 44 i 0.7 7.37 k 0.01 39 -?I 0.5
Episodic breathing/ gasping ,540 - 2,178 13 - 140 7 -- 30 0.2 -- l.Tr
on 50 fetal lambs in the same laboratory.
departure from normality, if these breathing movements are absent for an hour at a time. In addition, there are, from time to time, less frequent (1 to 4 per minute) deeper breathing movements, originally described as “gasps or sighs’13 but preferably termed “augmented breaths” unrelated to sleep state and normally present
