Sudden Infant Death Syndrome Siblings Research Articles

Night sleep heart rate patterns recorded by cardioneumography at home in normal and at-risk for SIDS infants

It has been reported that infants at higher than normal epidemiological risk for the sudden infant death syndrome (SIDS) have abnormal cardiac autonomic activity. A prospective work was performed using cardiopneumographic recordings (CPG) in order to evaluate heart rate (HR) and heart rate variability (HRV) patterns in sleeping normal control infants (C) and in infants at-risk for SIDS in their normal environment at home. One hundred appropriate-for-gestational age full-term infants were studied: 28 C, 48 SIDS siblings (SS), and 24 near-miss for SIDS (NM) within the first 2 weeks following the first detected apparent life-threatening event. The three groups of infants were comparable with respect to gestational and conceptional ages, birthweights, sex distribution and socio-economic backgrounds. CPG were done over two successive nights. Records were visually analysed for sleep states (quiet: QS, and combined active + indeterminate sleep: AIS) and wakefulness (W) coding. Periods of W were not analysed. An automatic programme allowed us to study HR minute-by-minute, and to assess whether HR and HRV patterns were specific to a certain part of the night, records were divided into three periods (2200—0040 h, 0041—0320 h, and 0321—0600 h). In C and SS groups, the HR was significantly lower in the 2nd night-period than in the 1st and 3rd periods in both QS and AIS (P < 0.05). In the NM group this difference was only observed during AIS (P < 0.05). During the three night-periods the HR was significantly elevated in AIS as compared to QS (at least (P < 0.05) in all infant groups except the NM group during the 2nd night-period. During QS the HR was significantly higher in NM than in C and SS groups (P < 0.02). During AIS the HR did not differ between infant groups. HRV was significantly lower in the NM group during QS in the three night-periods (P < 0.05). There was no difference in the HR and HRV patterns between C and SS groups with respect to sleep states and night period. We concluded that following the first detected apparent life-threatening event differences in the HR and HRV patterns can be demonstrated when sleeping NM infants are compared with both C and SS infants especially during QS in different night periods studied by CPG at home.

Hypercarbic ventilatory responses of infants at risk for SIDS.

We examined the hypercarbic ventilatory responses (HVR) of 143 infants at risk for sudden infant death syndrome (SIDS) and 34 normal control infants. Sixty-five of the at-risk infants had experienced apparent life-threatening events (ALTE), and 78 were siblings of SIDS victims. Twenty-three (35%) of the ALTE infants experienced subsequent apnea; one died of SIDS. Seven (9%) of the SIDS siblings experienced subsequent apnea; two ultimately died of SIDS. In the HVR studies, we measured tidal volume (VT), minute ventilation (VE), frequency of breathing (f), and end-tidal PCO2 (PETCO2) at rest and while breathing 2% and 4% CO2. Mean HVR vales for the ALTE, sibling, and control groups were all similar. The mean HVR values for those at-risk infants who experienced subsequent apnea were not different from those who did not experience subsequent apnea. However, those infants experiencing subsequent apnea had higher mean VT/kg values (P less than 0.01) and lower mean PETCO2 values (P less than 0.001) than those who did not. The SIDS siblings had significantly lower resting VT/kg values than either the near-miss infants or normal controls (P less than 0.01). We did not find depressed HVR values in infants at risk for SIDS. On the contrary, those infants who experienced subsequent apnea had evidence suggesting relative hyperventilation. SIDS siblings had evidence suggesting relative hypoventilation. These findings are interesting and thought-provoking. However, HVR studies do not appear to be sensitive, specific, or appropriate for the general screening of infants at risk for SIDS.

Pression transcutanee d'oxygene et apnees au cours des stades de sommeil chez des nourrissons normaux et a risque de MSIN

The relationship between chronic hypoxemia and sudden infant death syndrome (SIDS) has been reported by several authors. In order to study the influence of the apnea-time during a sleep state on transcutaneous oxygen tension (tcPO2), we have studied polygraphically 30 full-term infants (10 controls, 10 SIDS siblings and 10 near-miss for SIDS), aged from 5 to 13 weeks. No significant difference was observed either for apnea-time or tcPO2 between infant-groups studied in different sleep states. We could not find any correlation between apnea-time and tcPO2 in all groups of infants studied during different states of sleep. It is therefore concluded that in normal and at risk for SIDS infants, tcPO2 levels during sleep states cannot be explained only by the apnea-time.

Effect of sleep position on transcutaneous oxygen tension in SIDS siblings

To assess the influence of sleep position in sudden infant death syndrome siblings (SIDSS), we have studied 60 healthy SIDSS between the 1st and 3 + 4th month of life polygraphically. Infants were grouped according to postnatal age (1st, 2nd and 3 + 4th month) and sleep position (supine and prone). Transcutaneous oxygen tension (tCPO 2) was continuously recorded and studied in each sleep state (active (AS) and quiet sleep (QS)) during the 1st and 2nd sleep cycle. No statistical difference could be found in tCPO 2 levels as regards different sleep positions, postnatal ages (except for AS during the 2nd sleep cycle in prone and supine positions: 3 + 4th month > 2nd month, P < 0.05), sleep states (except for the 1st month in supine: QS > AS, P<0.05; and 3+4th month in prone: AS > QS, P < 0.05) or sleep cycles, tCPO 2 variability was found to be significantly higher in AS as compared to QS (P < 0.05). These results suggest that sleep position does not influence tCPO 2 levels in SIDSS.

Respiratory pauses and periodic breathing assessed by cardio-pneumography in normal infants and in SIDS siblings.

450 cardio-pneumograms (CPG) were performed on two successive nights in 68 controls and 235 SIDS siblings. The number of respiratory pauses greater than or equal to 5 sec and greater than or equal to 10 sec (NP) and the time of periodic breathing (PB) were calculated per 100 minutes of recording. Recordings were arranged into five age groups corresponding to the 1st, 2nd, 3rd, 4th and 5th-6th month of life. No significant differences in NP and PB were found when controls and SIDS siblings were compared separately within each age group, neither as a function of gestational age (less than 40 weeks GA vs greater than or equal to 40 weeks GA), nor as a function of the results of the 1st vs the 2nd night of recording. Nor was any significant difference in NP and PB found when comparing control vs sibling babies within each age group for the 1st or for the 2nd night of recording. In SIDS siblings, there was a significant decrease in the three variables studied between the 1st and the 2nd month of life. No significant decrease was found in controls. We conclude that SIDS siblings are not different from controls of the same age when respiratory variables are studied by CPG recordings.

Comparison of development and family background of “near-miss SIDS” and “siblings of SIDS” infants in an Infant Apnea Program

Comparison of development and family background of “near-miss SIDS” and “siblings of SIDS” infants in an Infant Apnea Program

Are polygraphic and cardiopneumographic respiratory patterns useful tools for predicting the risk for sudden infant death syndrome? A 10-year study.

Between 1974 and 1984 we have studied 204 control infants (C) comparing them with 650 SIDS siblings (SS) and 146 near-miss for SIDS (NM). These 1,000 full-term infants were recorded by day polysomnography (DPSG; n = 417), night polysomnography (NPSG; n = 257) and cardiopneumography (CPG; n = 2,600). Records were visually analyzed. In DPSG and NPSG, total amount of central, mixed and obstructive apnea as well as the percentage of periodic breathing was studied in each sleep state (active sleep, AS; quiet sleep, QS; indeterminate sleep, IS, and total sleep, TS) and over the total recording time (TRT). In CPG, only the total amount of central apnea and percentage of periodic breathing over TRT were studied. Infants were grouped according to postnatal age: less than 5, greater than or equal to 5 to less than or equal to 13, and greater than 13 to less than or equal to 26 weeks. In each age group results were compared as follows: C vs. SS, C vs. NM, and SS vs. NM for each parameter studied. Before 5 weeks and after 13 weeks there was no significant difference between C and SS, C and NM, and SS and NM in DPSG and NPSG for all categories of central, mixed and obstructive apnea as well as the percentage of periodic breathing in different sleep states and over TRT. Similar results were obtained in CPG for all categories of central apnea and percentage of periodic breathing over TRT.(ABSTRACT TRUNCATED AT 250 WORDS)

ASSESSMENT OF RESPIRATORY CONTROL IN INFANTS

The hypothesis that the primary defect in infants dying of the Sudden Infant Death Syndrome (SIDS) lies in the control of ventilation has provoked much interest. We have used the measurement of occlusion pressure as an index of the neuromechanical output of the respiratory system to investigate the response of infants to hyperoxic hypercapnia All measurements were made on unsedated infants during quiet sleep as defined by EEG and EOG recordings. Infants breathed through a facemask and pneumotachograph with a shutter attachment. Progressive hypercapnia was achieved by using a rebreathing bag with an initial pCO2 at 38 mmHg. The shutter was activated every 20-30 seconds and airway pressure was recorded from the facemask, until either the infant aroused or the pCO2 reached 65 mmHg. Pressure was measured 100 msec following the onset of inspiratory effort (P0.1). The slope of P0.1 against pCO2 was plotted for each subject. Seventeen infants below the age of 20 weeks (4 ‘near-misses’ for SIDS, 5 siblings of SIDS, 8 normal infants) were studied. The slope of P0.1 against pCO2 in the normal infants ranged from 0.08 to 0.47 cmH2O.mmHg−1 and the P0.1 at 55 mmHg ranged from 4.05 to 15.5 cmH2O. The values from the other groups of infants, who might be thought to be at increased risk for SIDS, all lay within these normal ranges. In conclusion, no significant differences were found between the three study groups under these defined circumstances.

Ventilatory pattern following diphtheria-tetanus-pertussis immunization in infants at risk for sudden infant death syndrome.

To evaluate the effects of diphtheria-tetanus-pertussis (DTP) immunization on the ventilatory pattern during sleep in infants at increased risk for sudden infant death syndrome (SIDS), we performed overnight pneumograms (recordings of ventilatory pattern and electrocardiogram) on 30 control infants, 46 infants with unexplained apnea, and 33 subsequent siblings of SIDS victims the night before and the night following a DTP immunization. Pneumograms were quantitated for total sleep time, longest apnea (in seconds), total duration of apneas longer than 6 s (in minutes), and total periodic breathing (in minutes). Following the DTP immunization there was no significant change in any criterion quantitated on pneumograms from any group except for a decrease in periodic breathing in the unexplained apnea group. We conclude that DTP immunization does not increase abnormalities of the ventilatory pattern as recorded by the pneumogram technique in infants at increased risk for SIDS.

Thiamine deficiency--a neglected problem of infants and mothers--possible relationships to sudden infant death syndrome.

An unexpectedly high incidence of biochemical thiamine deficiency (erythrocyte transketolase) was found in groups of mothers and infants, selected for apparent health from a westernized Caucasian community in Australia. Deficiency was common in mothers at term but not their infants, and in apparently healthy older infants but not their mothers. These findings can be explained by preferential delivery of thiamine to the fetus, at the expense of the pregnant mother; after delivery the mother recovers, and the infant becomes depleted. The incidence of thiamine deficiency was high in 'near-miss' sudden infant death syndrome (SIDS) infants and their mothers, and in siblings of SIDS. The thiamine deficient infants had a high familial incidence of SIDS deaths. These 'high risk families' might reflect poor nutrition or genetic defects of thiamine uptake and metabolism. Since apparently thriving infants with thiamine deficiency can sometimes die unexpectedly, thiamine status deserves more attention in clinical practice and research.

Brainstem auditory evoked responses in infants at risk of Sudden Infant Death

Brainstem auditory evoked responses (BAERs) were recorded from 63 near-miss Sudden Infant Death Syndrome (NMSIDS) infants, 26 siblings of SIDS (SSIBS) infants and 67 control infants between 0 and 30 weeks post-term. The majority of BAERs recorded from the NMSIDS and SSIBS infants had normal form and interpeak intervals (V-I and V-IIn) within normal limits for their age. However, 15% of these infants had interpeak intervals outside the normal range, suggesting abnormal neural function in these cases. The distributions of interpeak intervals for all NMSIDS and SSIBS infants were skewed towards longer times compared to control infants. The distributions of V-IIn intervals for both groups of at risk infants were significantly different to that of control infants. While the observations confirm that the recording of BAERs is not suitable for identifying infants at risk of SIDS, they suggest, however, that maturation of neural processing in the brainstem of these infants may be delayed.

1828 PNEUMOGRAMS IN SIDS SIBLINGS

We studied 12 hour pneumograms (PPG) in 17 siblings of SIDS. Mean postnatal age of study is 8.61 ± 16.9 weeks at a mean post-conceptual age of 47.88 ± 17.38 weeks. The following criteria were used in the interpretation. A6/D% ( 0.5%). These pneumograms were done earlier than the group who had normal PPG. It is possible to speculate that some of those with normal PPG might have had an abnormal PPG earlier. Ventilatory response to CO2 is abnormal in 2/3 of the normal PPG group and is valuable in assessing ventilatory control in these infants. We recommend a 12 hour nocturnal pneumogram on all SIDS siblings during the first week of life and a ventilatory response to CO2 test if the PPG is normal.

545 COMPARISON OF DEVELOPMENTAL OUTCOME AND FAMILY BACKGROUND OF “NEAR-MISS SIDS” AND SIBLINGS OF SIDS INFANTS

Developmental outcome and family background of 10 infants who were referred to the infant Apnea Program, D.M.C. because a sibling died of Sudden infant Death Syndrome (SIDS) were compared to 10 infants who entered the program with “near miss episodes” of SIDS (NME). No differences were found in the following infant variables: gestational age, race, birth weight, referral source, or delays in mental and/or motor development. There were no differences in maternal marital or economic status as measured by Medicaid eligibility. However, there was a difference between the two groups in the number of families identified as having serious social problems (p<.05 on a Fisher Exact Test). Eight of the families of the siblings of SIDS as compared to two of the families of the infants with NME had been identified as having one or more of the following social problems: substance abuse in the mother and/or father, referrals made by outside agencies to child protective services for abuse or neglect, placement of the patient and/or siblings into foster care because of abuse or neglect, referral of the mother to a social agency because of a parenting disorder. Thus while the two groups do not differ on most measures, the families of the siblings of SIDS have more serious social problems than families of NME infants. Although it is possible that the prior sudden death of an infant led to social disruption, it is also possible that an adverse home environment is a contributing factor in SIDS. The role of social pathology in SIDS thus requires further evaluation.

Home monitoring for infants at risk of the sudden infant death syndrome.

This study evaluates the effectiveness and social implications of home monitoring of 31 infants at risk of sudden infant death syndrome (SIDS). Thirteen siblings of children dying of SIDS, nine near miss SIDS infants and nine preterm infants with apnoea persisting beyond 40 weeks post conceptual age were monitored from a mean age of 15 days to a mean of 10 months. Chest movement detection monitors were used in 27 and thoracic impedance monitors in four. Genuine apnoeic episodes were reported by 21 families, and 13 infants required resuscitation. Apnoeic episodes occurred in all nine preterm infants but in only five (38%) of the siblings of SIDS (P less than 0.05). Troublesome false alarms were a major problem occurring with 61% of the infants and were more common with the preterm infants than the siblings of SIDS. All but two couples stated that the monitor decreased anxiety and improved their quality of life. Most parents accepted that the social restrictions imposed by the monitor were part of the caring process but four couples were highly resentful of the changes imposed on their lifestyle. The monitors used were far from ideal with malfunction occurring in 17, necessitating replacement in six, repair in six and cessation of monitoring in three. The parents became ingenious in modifying the monitors to their own individual requirements. Although none of these 31 'at risk' infants died the study sample was far too small to conclude whether home monitoring prevented any cases of SIDS.

THE RESPONSE TO CO2 IN INFANTS AT RISK FOR SIDS

Higher incidence of abnormal ventilatory response was found in two of three groups of infants tested with a computerized CO2 waveform analyzer that measures breath by breath responses. Forty nine infants (BW 1980±1010g, GA 33±5wks) with risk factors (prolonged apnea, BPD), 11 near miss (BW 3090±760g, GA 39±2wks), and 6 siblings of SIDS (BW 3310±1090g, GA 39±4wks) comprised the three groups. Age at evaluation was 44±10wks postconceptual age for risk infants, 54±14 wks for the near miss group, and 49±18 wks for siblings.The risk group slope was significantly greated that the sibling group slope (P<0.05). The difference between risk and near miss slopes did not reach statistical significance. Nine risk infants (18%), 6 near miss (54%), and 3 siblings (50%) were identified to have abnormal slopes, below 20 mm/kg/min/mmHg BTPS (P<0.05). Near miss and sibling infants demonstrated more blunted responses to CO2 that a group identified to be at risk.

VENTILATORY RESPONSE TESTING IN PREMATURE INFANTS

We studied the reproducibility of ventilatory response to CO2 in a group of premature infants with real or potential disturbances in the control of ventilation. (Ten infants BW 2.0±0.8 kg, GA 35±4 wks) comprised the test population, 6 with idiopathic apnea, 3 siblings of SIDS, and 1 near miss. The group was examined at 42±6 wks postconceptual age with a computerized waveform analyzer providing ventilatory response data to inhaled CO2. A second test was done 30 minutes after completion of the first. Significant correlation was found between the slopes, but significant differences were observed between their means(P<0.01) Baseline Ve was significantly lower in the repeat test with six infants starting at a lower level. Seven infants aroused at a lower PCO2 in the second test but the PCO2's at arousal were not different. It appears that the infants in this study became more sensitive to CO2 in the second test, as suggested by a steeper slope, lower baseline ventilation, and earlier arousal. We postulate that the CO2 challenge of the first test affected the second,and an interval greater than 30 min. may be necessary to duplicate results.

PROSPECTIVE ANALYSIS OF HEART RATE AND BREATHING PATTERNS IN INFANTS SUCCUMBING TO SIDS AND IN CONTROLS

In studies of babies at high risk for SIDS (near-SIDS and siblings), we have identified among some who died excess periodic breathing (PB) excess variability (var) of respiratory frequency (f) and increased oscillation of heart rate (HR), at 4-7 cycles per min., (low frequency peak-LFP). The present study was planned to test the hypothesis that in an unselected prospectively studied population, these same variables might discriminate SIDS from controls. From 6914 term infants, we selected 24 hour pneumograms performed at 6 weeks on 11 SIDS and 101 random controls. One SIDS had one near-SIDS spell. Casettes were coded for blind analysis. From data recorded between 12MN and 6AM we transcribed ECG and respiratory signals onto hard copy for visual inspection and we transferred these signals during all 5 min epochs of quiet breathing (Q) onto FM tape for spectral analysis. We inspected hard copies for PB and apnea ⩾10s. Spectral analysis identified f and var, HR and var and power at f (resp. sinus arrhythmia) and at the LFP. We rank ordered results to test hypothesis 1) that PB and 2) that abnormal spectral var were markers for SIDS. We performed cluster analysis on each data set The code was then broken; neither hypothesis was correct. These results neither support nor negate the apnea hypothesis of SIDS.

Prospective assessment of recurrence risk in sudden infant death syndrome siblings

Knowledge of the likelihood of a repetition of sudden infant death syndrome within a sibship, particularly in the next sibling, is important to parents. Methodologic considerations with respect to the studies of recurrence risk already published indicate that the rates reported are overestimates. This suspicion is confirmed by our study based on 826,162 infants surviving the first week of life on file in the Medical Birth Registry of Norway. A total of 1062 (1.3 per 1,000) infants died of SIDS; five deaths occurred as the second case in a family. The recurrence risk for the nextborn sibling was 5.6 per 1000, and for all subsequent siblings 4.8 per 1000, which would seem encouragingly low from a counseling point of view.

Home monitoring for central apnoea.

Between July 1978 and December 1981, 64 infants thought to be at increased risk from sudden infant death syndrome (SIDS) were monitored at home for central apnoea. Twenty four of the infants had had a 'near miss' episode at age, median (range), 6 (1 to 33) weeks, and of these infants 22 had had 335 alarms for apnoea by age 6 months. Stimulation by shaking was carried out on 38 occasions and bag and mask resuscitation on one. The remaining 40 infants were siblings of SIDS victims and of these, 35 were monitored from age 1 week (usually after discharge home). Thirty four of the SIDS siblings had had 573 alarms for apnoea by age 6 months: stimulation by shaking was carried out on 32 occasions and bag and mask resuscitation on one. The duration of home monitoring was, median (range), 34 (8 to 87) weeks for 'near miss' infants and 45 (12 to 70) weeks for SIDS siblings. All infants survived. As part of an over all support system monitors were accepted and greatly appreciated by most parents, especially those with previous experience of SIDS. Home monitoring was practicable but the commitment in time and expertise was great and objective benefits to the infant remain unproved.

Prospective assessment of recurrence risk in sudden infant death syndrome siblings: Irgens LM, Skjaerven R, Peterson DR. JPediatr 1984; 104: 349–351

Prospective assessment of recurrence risk in sudden infant death syndrome siblings: Irgens LM, Skjaerven R, Peterson DR. JPediatr 1984; 104: 349–351