Christian Poets

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.

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.

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.

Patterns of oxygenation during periodic breathing in preterm infants.

The characteristics of the arterial oxygen saturation (SaO2) signal during episodes of hypoxaemia (SaO2 less than or equal to 80% for greater than or equal to 4 s) associated with periodic and non-periodic apnoeic pauses were studied in 16 preterm infants with cyanotic episodes (patients). and 15 asymptomatic preterm infants (controls), matched on birthweight and gestational age. The patients showed a significantly higher percentage of apnoeic pauses followed by a hypoxaemic episode (25 vs. 6%, P less than 0.01), and a two-fold increase in the slope of the desaturation curve (8.4 vs. 4.3% per s, P less than 0.005) in periodic compared with non-periodic breathing. All other characteristic of oxygenation (baseline SaO2 before episodes of hypoxaemia, delay between onset of apnoeic pause and onset of desaturation, lowest SaO2 during episodes of hypoxaemia) were similar for periodic and non-periodic breathing patterns. Similar, but not significant, differences between isolated and periodic apnoeic pauses were also present in the controls. An analysis of episodes of bradycardia (less than or equal to 100 beats per minute (bpm] showed that out of 121 episodes in the patients 118 were accompanied by a fall in SaO2 to less than or equal to 80%, and in the remaining three SaO2 fell to 82%, 85% and 86%, respectively. Thus all episodes of bradycardia (less than or equal to 100 bpm) were associated with a fall in SaO2 detected by beat-to-beat pulse oximetry. Examination of hypoxaemic episodes and their relationship with bradycardia and with apnoeic pauses, periodic and non-periodic, may help the further understanding of the control of arterial oxygenation in preterm infants with cyanotic episodes.

International Child Care Practices Study: infant sleeping environment

BACKGROUNDnThe International Child Care Practices Study (ICCPS) has collected descriptive data from 21 centres in 17 countries. In this report, data are presented on the infant sleeping environment with the main focus being sudden infant death syndrome (SIDS) risk factors (bedsharing and infant using a pillow) and protective factors (infant sharing a room with adult) that are not yet well established in the literature.nnnMETHODSnUsing a standardised protocol, parents of infants were surveyed at birth by interview and at 3 months of age mainly by postal questionnaire. Centres were grouped according to geographic location. Also indicated was the level of SIDS awareness in the community, i.e. whether any campaigns or messages to reduce the risks of SIDS were available at the time of the survey.nnnRESULTSnBirth interview data were available for 5488 individual families and 4656 (85%) returned questionnaires at 3 months. Rates of bedsharing varied considerably (2-88%) and it appeared to be more common in the samples with a lower awareness of SIDS, but not necessarily a high SIDS rate. Countries with higher rates of bedsharing appeared to have a greater proportion of infants bedsharing for a longer duration (>5 h). Rates of room sharing varied (58-100%) with some of the lowest rates noted in centres with a higher awareness of SIDS. Rates of pillow use ranged from 4% to 95%.nnnCONCLUSIONSnIt is likely that methods of bedsharing differ cross-culturally, and although further details were sought on different bedsharing practices, it was not possible to build up a composite picture of typical bedsharing practices in these different communities. These data highlight interesting patterns in child care in these diverse populations. Although these results should not be used to imply that any particular child care practice either increases or decreases the risk of SIDS, these findings should help to inject caution into the process of developing SIDS prevention campaigns for non-Western cultures.

Home monitoring of transcutaneous oxygen tension in the early detection of hypoxaemia in infants and young children

Twenty three patients (age range 0.5-40 months) with recurrent cyanotic episodes underwent physiological recordings, including transcutaneous oxygen tension (TcPO2) from a monitor modified for use at home (Kontron 821S). Of 69 episodes in which the arterial oxygen saturation (SaO2, Nellcor N200) was less than or equal to 80% for greater than or equal to 20 seconds and/or central cyanosis was present, the TcPO2 monitor alarmed (less than or equal to 20 mmHg or 2.67 kPa) in every episode. The pulse oximeter identified hypoxaemia in 62 out of 69 episodes, failing in seven episodes due to signal loss from movement artefact. In only seven of 69 episodes was there an accompanying apnoeic pause (greater than or equal to 20 seconds), and heart rate fell to less than or equal to 80 beats/minute in only five of 28 episodes in which an electrocardiogram was recorded. In 32 episodes in which SaO2 fell to less than or equal to 60%, the TcPO2 monitor alarmed after a median time interval of 16 seconds (maximum time interval 30 seconds). The TcPO2 monitor was then used in an uncontrolled trial at home in 350 patients at increased risk of sudden death and/or hypoxaemia. Indications for monitoring included apparent life threatening events or cyanotic episodes (n = 163), prematurity and prematurity related disorders (n = 86), and sudden unexpected death in one or more siblings (n = 122). The TcPO2 monitor detected cyanotic episodes at home in 81 patients, 52 of whom received vigorous stimulation and/or mouth to mouth resuscitation. Twenty one of these 52 patients had further hypoxaemic episodes documented in hospital with pulse oximetry. In 30 patients, the TcPo2 monitor also identified the gradual development of hypoxaemia, as confirmed by pulse oximetry. Twenty of these needed additional inspired oxygen and six subsequently needed ventilatory support in hospital. This TcPo2 monitor is a reliable detector of both sudden and gradual onset hypoxaemia and is able to be used by parents in the home.

Reduced haemoglobin levels in infants presenting with apparent life-threatening events--a retrospective investigation.

Anaemia has been shown to be associated with an increased apnoeic pause frequency and with cyanotic breath‐holding spells. In this study, the relationship between anaemia and apparent life‐threatening events was retrospectively investigated in 72 term infants referred for assessment and home monitoring following an apparent life‐threatening event. For 41 infants (25 male, 16 female; 38 Caucasian, three Asian) a venous red blood cell count was available. Their median age at the time of the apparent life‐threatening event was 2.0 (0.6‐6.7) months. The Hb levels in these 41 infants were plotted against normal data from the literature. Thirty‐four infants had Hb levels below the mean, whilst six infants had values above the corresponding normal mean; the one remaining infant had a Hb value identical to the normal mean. Significantly more infants than expected had Hb levels below the mean (p < 0.001, binomial test). Anaemia may have played a role in the pathophysiology leading to life‐threatening events in some of the infants investigated in this study.

Small airway patency in infants with apparent life-threatening events

Abstract A reduction in specific airway conductance has been reported in infants with a history of an apparent life-threatening event (ALTE). It is unclear, however, whether this reflects upper or lower airway narrowing. We performed a controlled study to determine small airway patency in infants with ALTE. Lung function tests were performed in 26 infants with a history of ALTE and 27 healthy controls. Partial expiratory flow-volume curves were obtained during quiet sleep using the rapid chest compression technique; thoracic gas volume (TGV) and expiratory airway resistance (RAW) were measured by whole body plethysmography. Compliance of the respiratory system (Crs) was measured using the single breath occlusion technique. The median maximal flow at functional residual capacity (V˙maxFRC) was 85u2009ml/s (range 10–198u2009ml/s) in patients and 123 (range 47–316u2009ml/s) in controls (Pu2009=u20090.003). V˙maxFRC corrected for TGV was 0.5 s−1 (range 0.06–1.3 s−1) and 0.9 s−1 (range 0.4–1.8 s−1), respectively (Pu2009=u20090.001). TGV, RAW and Crs were not significantly different between patients and controls.nConclusion Reduced small airway patency may play a role in the pathogenesis of ALTE.

Mechanisms for hypoxaemic episodes in infancy and early childhood

As a result of studying a number of different clinical conditions in which hypoxaemic episodes occur, several different mechanisms have been identified. This paper outlines our studies on infants who present with obstructive sleep apnoea, persistent apnoeic and cyanotic episodes of prematurity, cyanotic breath holding and apparent life-threatening events. In order to study patients during such hypoxaemic events, it has been necessary to develop equipment which can be attached for long periods of time without discomfort. In hospital we perform multichannel physiological recordings of oxygen saturation (in the beatto-beat mode from a Nellcor N-200 pulse oximeter), the light plethysmograph signals from this oximeter (for validation of the saturation measurement), breathing movements, nasal airflow, electrocardiogram (ECG), transcutaneous (Tc) PO2 and PC02, electroencephalogram (EEG) and occasionally other signals such as expiratory muscle electromyogram. Such recordings can continue for between two and three weeks maximum, but require the patient to be restricted to a bed and remain in hospital. To study the mechanisms for hypoxaemic events occurring in infants at home, we have developed ambulatory recorders based on the monitoring of TcP02 (1). This event recorder consists of a battery operated computer which is approximately the same size as the Tc oxygen monitor. It records continuously onto a credit-card sized memory card (128 kb). The signals recorded include TcP02, ECG, breathing movements, oxygen saturation and the light plethysmograph signals from the pulse oximeter (Nellcor N200, beat-to-beat mode). In the event of a decrease in TcP02 below the alarm limit (usually 20 mmHg), the data from the TcP02 monitor and the other signals are saved for I0 min before and 5 min after the event. Parents can also press a marker which appears on the recording. The event recorder and the TcP02 monitor are battery-powered and can be taken out of the home with the baby. The pulse oximeter cannot be taken out of the home and its incorporation into the event recorder is a current development which will allow improved portability. Clinical nurse specialists have developed education and support programmes to effectively teach parents how to use the home TcP02 monitor and event recorder. All parents are instructed in the essentials ofcardiopulmonary resuscitation. As a result of using hospital and home-based event recording systems, we will now describe four different clinical situations in which recurrent hypoxaemic episodes occur in infants and young children. Sleep-related upper airway obstruction

Prolonged episodes of hypoxaemia in preterm infants undetectable by cardiorespiratory monitors

OBJECTIVEnTo 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.nnnMETHODSnLong-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).nnnRESULTSnDuring 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.nnnCONCLUSIONSnThese 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.