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Biomedical subjects

M P Samuels

Publications and source records attributed to M P Samuels.

At least 37 records · Page 2Linked to original sources
PubMed1994

Negative extrathoracic pressure ventilation in central hypoventilation syndrome.

Nine patients with central hypoventilation syndrome (CHS) were treated with negative extrathoracic pressure ventilation (VNEP). Treatment with VNEP was started between 20 days and 57 months of age, which was two days to 47 months after diagnosis. The equipment to provide VNEP utilised a new system with a latex neck seal and Perspex chamber allowing easy access to the child. Seven patients are managed with VNEP at home by their parents. They did not have a tracheostomy when VNEP was started at ages of 22, 24, 31, 38, and 75 days, 5 and 57 months. They have continued to be successfully managed with VNEP and without tracheostomy. Short periods of intubation and positive pressure ventilation were required on 10 occasions (median duration 7 days, range 4 to 21 days) in four subjects during respiratory tract infections. Three patients required periods of continuous positive airway pressure (CPAP) via a nasal mask or a nasopharyngeal airway during sleep to overcome upper airway obstruction. In three patients the hypoventilation improved and two of these do not require regular ventilatory support at 1.3 and 3.4 years of age. Six of these seven patients are developing normally. In two patients with long term tracheostomies, VNEP could not be established at an age of 29 and 52 months because of tracheal obstruction after temporary removal of their tracheostomy cannula. VNEP is an effective, non-invasive, treatment in infants with CHS if initiated before tracheostomy. It may improve the children's quality of life during the daytime. If upper airway obstruction is a problem in the first year of life, it may be combined with nasal mask CPAP.

Child Development↗
PubMed1994

Epidemiology and pathophysiology of apnoea of prematurity.

In preterm infants, reliance on the detection of apnoeic pauses and/or bradycardia results in significant amounts of hypoxaemia remaining undetected. In addition, recordings of breathing movements and ECG do not have predictive value for subsequent sudden infant death. In recent years, the ability to continuously monitor and record arterial oxygen saturation (SaO2) has produced important information regarding the mechanisms for respiratory events in the preterm population. Normal data on SaO2 (Nellcor N-200) and breathing movements have been collected in 160 preterm infants. Median baseline SaO2 during regular breathing was 99.5% (range 88.7-100) at the time of discharge from SCBU and 100% (95.3-100) at follow-up 6 weeks later. Episodic desaturations (SaO2 < or = 80% for > or = 4 s) ranged between 0 and 355 episodes per 12-hour recording. In a study of a separate group of 16 preterm infants with recurrent cyanotic episodes of unknown cause, the total number of abnormal hypoxaemic episodes was markedly increased. These hypoxaemic episodes were associated with three breathing pattern: (i) absent breathing movements; (ii) continued breathing movements, but absent airflow, and (iii) continuous airflow and breathing movements. Thus, preterm infants with cyanotic episodes have an increased number of clinically unapparent hypoxaemic episodes, some of which occur with continued breathing and airflow. In another study of 79 patients who had been born preterm and had a history of an apparent life-threatening event, 43 (54%) had abnormal oxygenation on multichannel recordings, including 23% with clinically undetected baseline hypoxaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Apnea↗
PubMed1994

Epileptic seizure-induced hypoxemia in infants with apparent life-threatening events.

OBJECTIVE: To describe the physiologic changes that occur during epileptic seizure (ES)-induced apparent life-threatening events (ALTE) and to provide an explanation for the mechanism whereby the hypoxemia characterizing these events occurred. PATIENTS AND DESIGN: Six infants were retrospectively selected from a group of 17 because they had ALTE documented on physiologic recordings where the first change in signals was in the electroencephalogram (EEG). The 17 infants had clinical features suggestive of partial seizures (but normal standard EEGs) and were from a sample of 172 infants with recurrent ALTE. All 17 infants underwent continuous recordings of breathing, electrocardiogram (ECG), oxygenation, and EEG, but only in 6 was an ES-induced ALTE recorded and the physiologic changes described. RESULTS: Twenty-three ALTE were documented in six infants. Events commenced with an abnormality in the EEG, followed by a decrease in SaO2 after a median interval of 27 seconds (range 2 to 147). Despite resuscitation, the median duration of severe hypoxemia (SaO2 < or = 60%) was 40 seconds (range 8 to 74). In 18 events (five infants) there was a median of four apneic pauses (range 1 to 9) preceding the decrease in SaO2 by a median duration of 24 seconds (range 3 to 48). The longest apneic pause per event lasted a median of 19 seconds (range 8 to 47). Breathing movements continued in five events (four infants), and expiratory airflow in one. Sinus tachycardia was found in 19 of the 23 events (six infants), but there were no cardiac arrhythmias. CONCLUSIONS: ES in infants can manifest as ALTE and be accompanied by potentially life-threatening episodes of severe hypoxemia and apnea, despite a normal EEG between events.

Apnea↗
PubMed1993

Diagnosis and management after life threatening events in infants and young children who received cardiopulmonary resuscitation.

OBJECTIVE: To determine the mechanisms and thereby appropriate management for apparent life threatening events treated with cardiopulmonary resuscitation in infants and young children. DESIGN: Prospective clinical and physiological study. SETTING: Royal Brompton Hospital or in patients' homes, or both. SUBJECTS: 157 Patients referred at median age 2.8 months (range 1 week to 96 months), 111 (71%) had recurrent events, 44 were born preterm, 19 were siblings of infants who had died suddenly and unexpectedly, and 18 were over 12 months old. INTERVENTIONS: Multichannel physiological recordings, including oxygenation, in hospital (n = 150) and at home (n = 61). Additional recordings with electroencephalogram, video, or other respiratory measures were used to confirm diagnoses. Management involved monitoring of oxygen at home, additional inspired oxygen, anticonvulsant treatment, or child protection procedures. MAIN OUTCOME MEASURES: Abnormalities on recordings compared to published normal data and their correlation with clinical events; sudden death. RESULTS: 53 of 150 patients had abnormalities of oxygenation on hospital recordings, 28 of whom had an accompanying clinical event. Home recordings produced physiological data from 34 of 61 patients during subsequent clinical events. Final diagnoses were reached in 77 patients: deliberate suffocation by a parent (18), hypoxaemia induced by epileptic seizure (10), fabricated history and data (Munchausen syndrome by proxy; seven), acute hypoxaemia of probable respiratory origin (40), and changes in peripheral perfusion and skin colour without hypoxaemia (two). Four patients died: three suddenly and unexpectedly (none on home oxygen monitors) and one from pneumonia. CONCLUSIONS: Identification of mechanisms is essential to the appropriate management of infants with apparent life threatening events.

Cardiopulmonary Resuscitation↗
PubMed1993

Continuous negative extrathoracic pressure and cardiac output--a pilot study.

Continuous negative extrathoracic pressure (CNEP) has been recently reintroduced as therapy for respiratory failure. To determine its effects on cardiac output a pilot study was performed in ten patients aged 2 months-3 years (median 4 months). All had chronic respiratory failure (seven with bronchopulmonary dysplasia). Five were breathing spontaneously and five were intubated and undergoing intermittent positive pressure ventilation. Transcutaneous oxygen saturation and PCO2, together with ECG were continuously monitored. Pulmonary artery blood flow velocity was measured non-invasively using pulsed wave Doppler. The 95% confidence intervals for the changes with and without CNEP in spontaneously breathing and ventilated patients showed no statistically significant changes in heart rate, O2 saturation, transcutaneous PCO2 or cardiac output. This study shows that the use of CNEP, administered in a tank respirator, does not lead to large changes in cardiac output.

Blood Flow Velocity↗
PubMed1993

Home event recordings of oxygenation, breathing movements, and heart rate and rhythm in infants with recurrent life-threatening events.

For an evaluation of the usefulness of event recording in identifying mechanisms for apparent life-threatening events, 94 infants (median age, 3.1 months; range, 0.5 to 12 months) with a history of two or more apparent life-threatening events of hitherto unknown cause underwent event recording of transcutaneous oxygen pressure, arterial oxygen saturation, (not recorded in all patients), breathing movements, pulse waveforms, electrocardiogram, and instantaneous heart rate. Recordings were triggered by a fall in transcutaneous oxygen pressure to less than 20 mm Hg. During a median duration of event recording of 1.3 months (0.1 to 10 months), 52 events were recorded in 34 patients; 7 of the events had to be excluded because of uninterpretable signals. The following mechanisms were identified in the remaining 30 patients (45 events): a sudden change in skin perfusion but without hypoxemia (6 in 5 patients), hypoxemia induced by an epileptic seizure (6 in 5 patients), hypoxemia induced by suffocation by a parent (4 in 4 patients), and parental fabrication of events and medical history (7 in 6 patients). In the remaining 22 events in 12 patients, the precise mechanism of events could not be identified. Analysis of these as-yet-unexplained events showed prolonged abnormal hypoxemia (a fall in transcutaneous oxygen pressure to between 4 and 18 mm Hg and a fall in arterial oxygen saturation to 5% to 75%), lasting for 40 to 500 seconds in all. Only five of these events involved prolonged (> 20 seconds) apneic pauses, and only four an episode of bradycardia (heart rate < 80 or 60 beats/min). Thus event recording identified various mechanisms of apparent life-threatening events. In the events that remained unexplained, prolonged apneic pauses or episodes of bradycardia were found in only a minority. The identification of hypoxemia therefore may be more relevant to the early detection of these events than the identification of apnea or bradycardia or both. The relevance of these findings with regard to sudden infant death syndrome remains to be determined.

Apnea↗
PubMed1993

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.

Apnea↗
PubMed1993

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.

Adolescent↗
PubMed1992

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.

Birth Weight↗
PubMed1992

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 less than 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.

Age Factors↗