Oxygen saturation during the first 24 hours of life.

AIM: To determine normative data for arterial oxygen saturation, measured by pulse oximetry (SpO2), in healthy full term infants throughout their first 24 hours of life. METHODS: Long term recordings of SpO2, pulse waveform, and breathing movements were made on 90 infants. Recordings were analysed for baseline SpO(2), episodes of desaturation (SpO2 /= four seconds, and periodic apnoea (>/= three apnoeic pauses, each separated by /= 20 seconds) were identified in six recordings. Four desaturations fell to

Effect of exposure to 15% oxygen on breathing patterns and oxygen saturation in infants: interventional study.

OBJECTIVE: To assess the response of healthy infants to airway hypoxia (15% oxygen in nitrogen). DESIGN: Interventional study. SETTINGS: Infants' homes and paediatric ward. SUBJECTS: 34 healthy infants (20 boys) born at term; mean age at study 3.1 months. 13 of the infants had siblings whose deaths had been ascribed to the sudden infant death syndrome. INTERVENTION: Respiratory variables were measured in room air (pre-challenge), while infants were exposed to 15% oxygen (challenge), and after infants were returned to room air (post-challenge). MAIN OUTCOME MEASURES: Baseline oxygen saturation as measured by pulse oximetry, frequency of isolated and periodic apnoea, and frequency of desaturation (oxygen saturation < or = 80% for > or = 4 s). Exposure to 15% oxygen was terminated if oxygen saturation fell to < or = 80% for > or = 1 min. RESULTS: Mean duration of exposure to 15% oxygen was 6.3 (SD 2.9) hours. Baseline oxygen saturation fell from a median of 97.6% (range 94.0% to 100%) in room air to 92.8% (84.7% to 100%) in 15% oxygen. There was no correlation between baseline oxygen saturation in room air and the extent of the fall in baseline oxygen saturation on exposure to 15% oxygen. During exposure to 15% oxygen there was a reduction in the proportion of time spent in regular breathing pattern and a 3.5-fold increase in the proportion of time spent in periodic apnoea (P < 0.001). There was an increase in the frequency of desaturation from 0 episodes per hour (range 0 to 0.2) to 0.4 episodes per hour (0 to 35) (P < 0.001). In 4 infants exposure to hypoxic conditions was ended early because of prolonged and severe falls in oxygen saturation. CONCLUSIONS: A proportion of infants had episodes of prolonged (< or = 80% for > or = 1 min) or recurrent shorter (< or = 80% for > or = 4 s) desaturation, or both, when exposed to airway hypoxia. The quality and quantity of this response was unpredictable. These findings may explain why some infants with airway hypoxia caused by respiratory infection develop more severe hypoxaemia than others. Exposure to airway hypoxia similar to that experienced during air travel or on holiday at high altitude may be harmful to some infants.

Detection of movement artifact in recorded pulse oximeter saturation.

UNLABELLED: Movement artifact (MA) must be detected when analysing recordings of pulse oximeter saturation (SpO2). Visual analysis of individual pulse waveforms is the safest, but also the most tedious, method for this purpose. We wanted to test the reliability of a computer algorithm (Edentec Motion Annotation System), based on a comparison between pulse and heart rate, for MA detection. Ten 12-h recordings of SpO2, pulse waveforms and heart rate from ten preterm infants were analysed for the presence of MA on the pulse waveform signal. These data were used to determine the sensitivity and specificity of the computer algorithm, and of the oximeter itself, in detecting MA. Recordings were divided into segments of 2.5 s duration to compare the movement identification methods. Of the segments 31% +/- 6% (mean +/- SD) contained MA. The computer algorithm identified 95% +/- 3% of these segments, the pulse oximeter only 18% +/- 11%. Specificity was 85% +/- 4% and 99% +/- 0%, respectively. SpO2 was < or =80% in 3% +/- 1% of segments. 88% +/- 7% of the pulse waveform signal showed MA during this time, leaving a significant potential for erroneous identification of hypoxaemia. Recordings of SpO2 do not allow a reliable identification of MA. CONCLUSION: Without additional information about movement artifact, a significant proportion of recording time of pulse oximeter signal may be regarded as demonstrating hypoxaemia which, in fact, simply reflects poor measurement conditions. The computer algorithm used in this study identified periods of movement artifact reliably.

Home monitoring of infants at increased risk of sudden death.

Home apnoea and cardiorespiratory monitors are commonly used in the UK, the rest of Europe and USA in infants at increased risk of 'sudden infant death'. The efficacy of apnoea and cardiorespiratory monitors remains unknown. The use of transcutaneous oxygen monitoring is presented as an alternative method of home monitoring. Recommendations are proposed regarding nursing practice and the future of home monitoring in infants at increased risk of sudden death.

Arterial oxygen saturation in healthy term neonates.

UNLABELLED: Our objective was to determine arterial oxygen saturation as measured by pulse oximetry (SpO2) in healthy term neonates during their first 4 weeks of life. Overnight recordings of SpO2 (Nellcor N200), photoplethysmographic (pulse) waveforms from the oximeter and breathing movements were performed in 60 term infants. They were studied initially during their 1st week of life (median age 4 days, range 1-7) and then again during their 2nd-4th week (median age 17 days, range 8-27). Median baseline SpO2, measured during regular breathing, was 97.6% (range 92-100) during week 1 versus 98.0% (86.6-100) during week 2-4 (P > 0.05). Episodes of desaturation, defined as a fall in SpO2 to < or = 80% for > or = 4 s, were found in 35% of recordings obtained in week 1 compared to 60% of those obtained in week 2-4 (P < 0.01). Their frequency increased from a median of (0-41) per 12 h of recording at the initial recording to 1 (0-165) at follow up (P < 0.01). Analysis of the data by week of life showed a peak in desaturation frequency in the 2nd week of life. The infants with extreme values at follow-up (e.g. a baseline SpO2 of 86.6%, 5th percentile 91.9%, or a desaturation frequency of 165 per 12 h of recording, 95th percentile 32) had had values well within the normal range during their initial recording (a baseline SpO2 of 94.4%, or a desaturation frequency of 4). Most of the desaturations in the infants with extreme values were associated with periodic apnoea. These results demonstrate only relatively minor developmental changes in oxygenation in term neonates during the first 4 weeks of life. The clinical significance of outlying values, i.e. a low baseline SpO2 or a high number of episodic desaturations, remains to be determined. CONCLUSION: These healthy term neonates had values for baseline oxygen saturation and desaturation frequency that were not substantially different from those observed in older infants.

Prolonged episodes of hypoxemia in preterm infants undetectable by cardiorespiratory monitors.

OBJECTIVE: To determine whether episodes of prolonged hypoxemia occur without prolonged apneic pauses (> or = 20 seconds) and without bradycardia (pulse rate, < or = 100 beats per minute) in apparently well preterm infants. METHODS: Long-term recordings of arterial oxygen saturation as measured by pulse oximetry (SpO2), photoplethysmographic (pulse) waveforms from the oximeter, and breathing movements were performed in 96 preterm infants (median gestational age at birth, 34 weeks; range, 28 to 36 weeks) who were breathing room air. Recordings started at a median age of 4 days (range, 1 to 60 days). RESULTS: During a median duration of recording of 25 hours, 88 episodes in which SpO2 fell to 80% or less and remained there for 20 seconds or longer were identified in 15 infants. The median duration of these prolonged desaturations was 27 seconds (range, 20 to 81 seconds). In 73 episodes (83%), SpO2 continued to fall to 60% or less. Twenty-three desaturations were associated with prolonged apneic pauses and 54 with bradycardia; 19 of these were associated with both apnea and bradycardia. Thirty desaturations (34%; 10 infants) occurred without bradycardia and without prolonged apnea. CONCLUSIONS: These results indicate that a proportion of apparently well preterm infants exhibit episodes of severe prolonged hypoxemia unaccompanied by prolonged apneic pauses or bradycardia. Such episodes, therefore, would be difficult to detect if only breathing movements and heart rate are monitored. Indications for the use of oxygenation monitors in preterm infants should be reconsidered.

Arterial oxygen saturation in preterm neonates without respiratory failure.

To obtain normal data on arterial oxygen saturation as measured by pulse oximetry (SpO2; Nellcor N200), we obtained 12-hour tape recordings of SpO2, photoplethysmographic waveforms, instantaneous pulse rate, and observations of breathing movements on 55 preterm neonates (25 girls) who had been admitted to one of four special care baby units but had no signs of respiratory distress and were breathing room air at 24 hours of age. Their median gestational age at birth was 35 weeks (range, 30 to 36), and their median age at the time of study 1 day (range, 1 to 7). Median baseline SpO2, measured only during regular breathing, was 99.4% (range, 90.7 to 100; 5th percentile, 95.5). Ten recordings (18%) contained a total of 83 episodes of desaturation (defined as a fall in SpO2 to < or = 80% for > or = 4 seconds). The 95th percentile for desaturation frequency was eight per recording. One infant had 55 episodes of desaturation and thus accounted for two thirds of all episodes observed. Only one of the episodes of desaturation in this infant, and none of those in the other nine infants, had been noted clinically, nor had the abnormally low baseline SpO2 (90.7%) in one infant. Baseline SpO2 in these nondistressed preterm neonates was higher than might be expected, given the SpO2 levels currently recommended for preterm infants with respiratory failure. A minority of infants, however, had a low baseline SpO2 or a high frequency of episodes of desaturation, the potential effects of which remain to be determined.

Oxygen saturation and breathing patterns in children.

OBJECTIVE: To obtain information on breathing patterns and oxygenation in children. DESIGN: Overnight tape recordings of arterial oxygen saturation (SaO2; Nellcor N200 in beat-to-beat mode), photoplethysmographic waveforms, and breathing movements in 70 healthy children (mean age 8.0 years, range 2 through 16). Analysis of recordings for pauses in breathing movements of > or = 4 seconds (apneic pauses), for episodes in which SaO2 fell to < or = 90% (desaturations) and, only during the state of regular breathing, for baseline SaO2, heart rate, and respiratory rate. RESULTS: Both baseline heart rate and respiratory rate decreased with increasing age (r = -.7 and -.3, respectively, P < .01). Baseline SaO2 was similar to that previously observed in infants (median 99.5%, range 95.8 to 100, 5th centile 96.6%). Every recording showed apneic pauses, with a frequency that did not vary consistently with age (median 7.7/h, range 0.6 to 25.5). One hundred nineteen apneic pauses in 43 recordings lasted for 15 to 19.9 seconds, and 23 lasted for > or = 20 seconds (longest 28.8 seconds). The number of episodic falls in SaO2 to < or = 90% decreased with age (r = -.3, P < .01); such episodes were found in 47% of children aged 2 through 6 years, but in only 13% of those aged 12 through 16 years. The 95th centile for desaturation frequency in the total group was 0.6/h. In six episodes in four patients, SaO2 fell to < or = 80%. CONCLUSIONS: Apneic pauses, some of which can last for more than 20 seconds, are a normal phenomenon in healthy children and adolescents, but only a small minority of apneic pauses affect blood gas homeostasis. Information concerning oxygenation may be more relevant to our understanding of the maturation of respiratory control than the recording of breathing signals alone.

The relationship between bradycardia, apnea, and hypoxemia in preterm infants.

The pathogenesis of bradycardias in preterm infants is poorly understood. Because their pathogenesis may involve both apnea and hypoxemia, we set out to analyze the proportion of bradycardias that were associated with an apneic pause and/or a fall in arterial oxygen saturation (SaO2), and the temporal sequence of the three phenomena, in overnight tape recordings of SaO2 (Nellcor N100 in beat-to-beat mode), breathing movements, nasal airflow, and ECG in 80 preterm infants at the time of discharge from hospital. A bradycardia was defined as a fall in heart rate of > or = 33% from baseline for > or = 4 s, an apneic pause as a cessation of breathing movements and/or airflow for > or = 4 s, and a desaturation as a fall in SaO2 to < or = 80%. A total of 193 bradycardias were found in 46 (58%) of the recordings (median, three per recording; range 1-18). There was a close relationship between bradycardias, apneic pauses, and desaturations: 83% of bradycardias were associated with apneic pauses and 86% with desaturations. Where all three phenomena occurred in combination, the time from the onset of apnea to the onset of the fall in SaO2 was shorter (median interval, 0.8 s; range -4.9-+ 11.5 s) than that from the onset of apnea to the onset of bradycardia (median, 4.8 s; range -4.0-+ 14.0 s). Hence, most bradycardias (86%) commenced after the onset of the fall in SaO2. We conclude that bradycardia, apnea, and hypoxemia are closely linked phenomena in preterm infants.

Oxygen saturation and breathing patterns in preterm infants with cyanotic episodes.

The pathophysiology of cyanotic/apnoeic episodes in preterm infants was investigated using overnight tape recordings of beat-to-beat arterial oxygen saturation (SaO2), plethysmographic waveforms from the oximeter, breathing movements and nasal airflow. Recordings were made in 16 preterm infants with recurrent cyanotic episodes of unknown cause that had received stimulation or resuscitation, and 15 preterm controls, matched for birth weight, post-conceptional and postnatal age. The recordings were analysed for baseline SaO2, the number of hypoxaemic episodes (SaO2 < or = 80% for > or = 4 s) and the breathing patterns associated with each episode. There was a significant difference in the total number of hypoxaemic episodes between patients and controls (520 versus 100; p < 0.01), but no difference was found for mean baseline SaO2 (98.6 versus 99.0%; p > 0.05). The mean duration of each hypoxaemic episode in the patients was 9.5 s compared with 5.8 s in the controls (p < 0.01). Although most hypoxaemic episodes (62 and 76%) were associated with pauses in breathing movements, a proportion (8 and 18%, respectively) occurred despite continuous airflow and breathing movements in both patients (6 of 16) and preterm controls (2 of 15). The rate of decrease in SaO2 was significantly more rapid during these latter hypoxaemic episodes than during episodes associated with isolated apnoeic pauses (8.5 versus 3.2% per second, p = 0.02). Preterm infants with cyanotic episodes have increased numbers of clinically unapparent hypoxaemic episodes, some of which have continued ventilation and rapid desaturation. The pathogenesis of these episodes warrants further investigation.

Sleep related upper airway obstruction and hypoxaemia in sickle cell disease.

A cohort of 53 patients (age range 1.9-16.5 years) with sickle cell disease (49 homozygous SS and four S beta zero-thalassaemia) was studied for evidence of sleep related upper airway obstruction (UAO). This involved (i) a clinical assessment based on a history of snoring, a score of tonsillar size, and (for 50 patients) overnight multichannel respiratory recordings, and (ii) a blinded analysis of arterial oxygen saturation (SaO2) from the above recordings, and comparison with results from 50 healthy age matched controls of both white (n = 25) and Afro-Caribbean race. There was no difference in the baseline SaO2 values of the white and Afro-Caribbean controls. Eighteen patients with sickle cell disease (36%) were found to have sleep related UAO. The blinded analysis showed that eight patients (16%) had episodic hypoxaemia (SaO2 less than or equal to 80%, a value not observed in controls) and/or low baseline SaO2 values (less than 95.8%, the lowest value seen in the controls). Postoperative assessment was undertaken in 15 patients who underwent adenotonsillectomy. All demonstrated an improvement in symptoms and a reduction or abolition of episodic hypoxaemia. Of the 47 patients assessed when free of UAO (not demonstrated on screening, n = 32, or resolved following surgery, n = 15), seven continued to show baseline hypoxaemia. Sleep related UAO and baseline hypoxaemia are common complications of sickle cell disease in children.

Hypoxaemia in infants with respiratory tract infections.

Nineteen infants who were graduates from special care baby units underwent two overnight tape recordings of oxygen saturation (SaO2) and breathing movements; one during an upper (n = 12) or lower (n = 7) respiratory tract infection and the other when free of infection. Baseline SaO2 was lower during infection (median 99.6 vs 100%, p less than 0.01), with four patients having values (84.3-95.5%) below the normal lower limit for full-term infants (97%). The median number of apnoeic pauses was also lower during respiratory tract infection (4.7 vs 15.7/h, p less than 0.02). The median number of episodic desaturations (SaO2 less than or equal to 80%) did not change significantly (1.3 vs 1.9/h, p greater than 0.05), with the exception of one patient who had extremely increased values during infection for both apnoeic pauses (63/h) and desaturations (112/h). No infant, however, was considered clinically hypoxaemic. Clinically unsuspected hypoxaemia may thus occur during respiratory tract infection in a proportion of infants graduating from special care baby units. Such hypoxaemia may have potentially deleterious effects.

Arterial oxygen saturation in preterm infants at discharge from the hospital and six weeks later.

To obtain normal data on arterial oxygen saturation (SaO2) in preterm infants and to study early developmental changes in SaO2, we obtained overnight tape recordings of SaO2 and breathing movements in 160 preterm infants at their discharge from three special care baby units (mean gestational age at birth 33 weeks; at time of study, 37 weeks). One hundred ten infants (69%) underwent a second recording 6 weeks later. Median baseline SaO2 during regular breathing was 99.5% (range 88.7% to 100%) at discharge, and 100% (range 95.3% to 100%) at follow-up (p less than 0.001). The number of episodes of desaturation, defined as a fall in SaO2 to less than or equal to 80% for at least 4 seconds, corrected to the mean duration of recording (12.2 hours), decreased from a median of 3 (0 to 355) to 0 (0 to 17) (p less than 0.001). The median duration of each episode of desaturation remained unchanged (5.2 (4.0 to 22.7) vs 5.5 (4.2 to 24.0) seconds). At discharge, a small minority of infants had a clinically unrecognized low baseline SaO2 (lowest, 88.7%; 5th percentile, 95.7%) or a high number of desaturation episodes (the highest was six times the 95th percentile value). At follow-up, all outlying values had normalized. Follow-up recordings made between 42 and 47 weeks of gestational age (n = 53) were compared with similar recordings from 67 term infants at the same gestational age. The preterm infants had a significantly higher baseline SaO2 and no more desaturation than the infants born at term. Knowledge of normal ranges of oxygenation and their changes with age may be of value in identifying clinically undetected hypoxemia in preterm infants at discharge from the hospital. The potential influence of such hypoxemia on clinical outcome remains to be determined.

Breathing patterns and heart rates at ages 6 weeks and 2 years.

Forty-two randomly selected, full-term, healthy infants underwent 24-hour electrocardiographic recordings and breathing movements at about ages 6 weeks (median age, 43 days; range, 34 to 61 days) and 2 years (median age, 26 months; range, 21 to 35 months). The number and duration of apneic pauses of 3.6 seconds or longer were analyzed. Periodic apnea was defined as a sequence of three or more apneic pauses, each separated by fewer than 20 breaths. All other apneic pauses were defined as isolated. Median heart rates and respiratory rates, which were measured during regular breathing, decreased from 137/min and 35/min to 98/min and 21/min, respectively. The total duration of periodic apnea remained unchanged (median, 0.06 min/h vs 0.05 min/h). Although the median frequency of all isolated apneic pauses decreased from 3.6/h to 2.5/h, the number of those that were longer than 6 seconds increased from 0.37/h to 0.80/h, leading to an increase in the proportion of these pauses, among all isolated apneic pauses, from 10% at age 6 weeks to 32% at age 2 years. Only one apneic pause in one infant at age 6 weeks, but eight pauses in six children at age 2 years, were longer than 15 seconds. A knowledge of such normal variability in the duration of apneic pauses in older infants and young children is essential for the interpretation of pneumograms and alarms while monitoring breathing movements.

Sleep related upper airway obstruction in a cohort with Down's syndrome.

The prevalence of sleep related upper airway obstruction (UAO) was studied in a cohort of 34 children with Down's syndrome from a geographically defined area. Thirty two (94%) of the children, ranging in age between 0.1 and 4.9 years (median 1.4), underwent full clinical assessment for UAO including parental questionnaires and overnight tape recordings of chest wall movements and arterial oxygen saturation (SaO2). Compared with controls, children with Down's syndrome had (a) an increased incidence of stridor and chest wall recession during sleep, (b) an increased frequency of a pattern on inspiration indicating increased upper airway resistance, (c) a reduced baseline oxygen saturation (having excluded recordings on four children with potential for right to left intracardiac shunting), and (d) an increased number of episodes with SaO2 less than or equal to 90% despite continued chest wall movements. At their initial assessment seven children (22%) had evidence of UAO. The 18 youngest children (less than or equal to 1.7 years) underwent repeated recordings and clinical assessment until they had all reached 2 years of age. A further three were found to have developed UAO. Sleep related UAO is a common problem in children with Down's syndrome, occurring in 10 of 32 (31%) of this population based sample.

Arterial oxygen saturation and breathing movements during the first year of life.

Sixteen healthy term infants underwent 12 hour tape recordings of arterial oxygen saturation (SaO2)(Nellcor N100 in beat to beat mode) and breathing movements at around 6 weeks, 3 and 6 months of age. Six of these infants had an additional recording at around their first birthday. Recordings were analysed throughout for pauses in breathing movements of greater than or equal to 4 s (apnoeic pauses), episodes in which SaO2 fell to 80% (desaturations), and (only during regular breathing) baseline SaO2. In the 16 infants studied at 6 weeks, 3 and 6 months, the median frequency of both apnoeic pauses (5.6, 5.7, and 6.1/h, respectively) and desaturations (0.7, 0.4 and 0.5/h, respectively) showed little change. The majority of desaturations followed an apnoeic pause (median 73.2, 86.2 and 93.8% of desaturations). The median proportion of apnoeic pauses followed by a desaturation did not change significantly (9.0, 7.5 and 9.1%), despite an increase in the proportion of apnoeic pauses of greater than or equal to 8 s in duration from 2.0% at 6 weeks to 5.3% at 3 months (P less than 0.01). Baseline SaO2 was 97.3% or higher in all recordings. Median baseline SaO2 increased from 99.6 to 99.9% between 6 weeks and 3 months (P less than 0.02) and remained unchanged thereafter. In the subgroup of infants studied also at one year of age, again no significant differences were found with increasing age in the frequency of either apnoeic pauses or desaturations. The data show that in healthy subjects no major changes occur between 6 weeks and 1 year of life in apnoeic pause frequency or arterial oxygenation.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen saturation and breathing patterns in infancy. 1: Full term infants in the second month of life.

Overnight 12 hour tape recordings were made of arterial oxygen saturation (SaO2, pulse oximeter in the beat to beat mode) and abdominal wall breathing movement on 67 healthy, full term infants between the ages of 29 and 54 (median 39) days. The median baseline SaO2 during regular breathing was 99.8% (range 97.0-100%). Fifty four infants (81%) had shortlived episodes during which SaO2 fell to 80% or less (desaturation); the median rate was 0.9 desaturations/hour, and the median duration of each desaturation was 1.2 seconds. The 97th centile value for the duration of all episodes in which SaO2 fell to less than or equal to 80% was 4.0 seconds. The frequency of desaturations was significantly higher, and their duration significantly longer, when the breathing pattern was non-regular rather than regular. The percentage of apnoeic pauses (greater than or equal to 4 seconds in duration) followed by a desaturation was higher during non-regular than regular breathing; it was particularly high during periodic breathing. A knowledge of normal variability of baseline measurements of oxygenation and of the relationship between oxygenation and breathing patterns in infants is essential to the use of pulse oximetry in clinical practice.

Oxygen saturation and breathing patterns in infancy. 2: Preterm infants at discharge from special care.

Overnight 12 hour tape recordings of arterial oxygen saturation (SaO2, pulse oximeter in the beat to beat mode), breathing movements, and airflow were made on 66 preterm infants (median gestational age 34 weeks, range 25-36) who had reached term (37 weeks) and were ready for discharge from the special care baby unit. No infant was given additional inspired oxygen during the study. The median baseline SaO2 was 99.4% (range 88.9-100%). Eight infants had baseline SaO2 values below 97%, the lowest value observed in a study on full term infants. All but one infant had short-lived falls in SaO2 to less than or equal to 80% (desaturations), which were more frequent (5.4 compared with 0.9/hour) and longer (mean duration 1.5 compared with 1.2 seconds) than in full term infants. There was no evidence that gestational age at birth influenced the frequency or duration of desaturations among the preterm infants. The frequency of relatively prolonged episodes of desaturation (SaO2 less than or equal to 80% for greater than or equal to 4 seconds), however, decreased significantly with increasing gestational age (0.5, 0.4, 0.2, and 0.1 episodes/hour in infants at less than or equal to 32, 33-34, 35, and 36 weeks' gestational age, respectively). Analysis of the respiratory patterns associated with such episodes showed that 5% occurred despite both continued breathing movements and continuous airflow. Five infants had outlying recordings: three had baseline SaO2 values of less than 95% (88.9, 92.7, and 93.8%), and two had many prolonged desaturations (14 and 92/hour; median for total group 0.2, 95th centile 2.3). None of these five infants had been considered clinically to have dis order of oxygenation. Although these data are insufficient to provide information about outcome, we conclude that reference data on arterial oxygenation in preterm infants are important to enable the identification of otherwise unrecognized hypoxaemia.

Investigation of cyanotic/apneic episodes and sleep-related upper airway obstruction by long-term non-invasive bedside recordings.

Over a 4 year period, investigations were performed on 226 infants and children suffering cyanotic episodes and 160 suspected to be the victims of sleep-related upper airway obstruction. These investigations have been considerably aided by long-term tape recordings of multiple cardiorespiratory and neurophysiological variables from non-invasive sensors. In addition to identifying the underlying mechanisms responsible for cyanotic episodes, recordings have identified the presence or absence of airway obstruction, documented its severity by its effects on oxygenation and on sleep-state organization, and evaluated objectively the effects of treatment. The recording system, which is transportable, has been especially developed for use outside of the specialized sleep laboratory and was used on patients in hospital wards and at home.

Cardiorespiratory patterns in infants presenting with apparent life-threatening episodes.

A total of 305 infants presenting with apparent life-threatening events (ALE) were referred by their paediatricians and underwent 24-hour tape recordings of electrocardiogram and abdominal breathing movements (from a pressure capsule transducer). Seventy-seven of these infants, all full-term (greater than or equal to 37 weeks of gestation), were randomly selected, followed up for clinical outcome, and their recordings subjected to a detailed analysis of heart and respiratory rates and breathing patterns. Recordings on 157 age-matched, full-term controls were similarly analysed for comparison purposes. One of the 77 patients suffering from ALE had a pre-existing neurodevelopmental problem, and 4 more cases showed this at follow-up, including 1 case whose ALE was subsequently diagnosed as originating from non-accidental injury. Compared with controls and as a group, the patients suffering from ALE showed higher numbers of apnoeic pauses (p less than 0.001), larger quantities of periodic breathing (p less than 0.01) and lower respiratory rates during regular breathing (p less than 0.01).