Marcelo Garrido | Universidad Diego Portales (original) (raw)

Papers by Marcelo Garrido

Research paper thumbnail of Automated detection of apnea/hypopnea events in healthy children polysomnograms: Preliminary results

2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013

A methodology to detect sleep apnea/hypopnea events in the respiratory signals of polysomnographi... more A methodology to detect sleep apnea/hypopnea events in the respiratory signals of polysomnographic recordings is presented. It applies empirical mode decomposition (EMD), Hilbert-Huang transform (HHT), fuzzy logic and signal preprocessing techniques for feature extraction, expert criteria and context analysis. EMD, HHT and fuzzy logic are used for artifact detection and preliminary detection of respiration signal zones with significant variations in the amplitude of the signal; feature extraction, expert criteria and context analysis are used to characterize and validate the respiratory events. An annotated database of 30 all-night polysomnographic recordings, acquired from 30 healthy ten-year-old children, was divided in a training set of 15 recordings (485 sleep apnea/hypopnea events), a validation set of five recordings (109 sleep apnea/hypopnea events), and a testing set of ten recordings (281 sleep apnea/hypopnea events). The overall detection performance on the testing data set was 89.7% sensitivity and 16.3% false-positive rate. The next step is to include discrimination among apneas, hypopneas and respiratory pauses.

Research paper thumbnail of Sleep Cyclic Alternating Pattern in Otherwise Healthy Overweight School-Age Children

SLEEP, 2014

Sleep Cyclic Alternating Pattern in Overweight Children-Chamorro et al INTRODUCTION Chronic and m... more Sleep Cyclic Alternating Pattern in Overweight Children-Chamorro et al INTRODUCTION Chronic and moderate sleep debt is an increasingly common feature across societies and age groups. 1,2 There is mounting evidence that nighttime sleep patterns relate to body weight in pediatric groups. Epidemiological studies in children consistently show an inverse relation between sleep duration and body mass index (BMI). 3-7 Polysomnographic (PSG) studies show decreased sleep amount, sleep efficiency, and REM sleep in overweight (OW) subjects. 8-11 However, few studies have assessed sleep patterns within the sleep-obesity frame in the absence of apparent sleep alterations. Sleep cyclic alternating pattern (CAP) is a physiologic oscillatory phenomenon occurring during NREM sleep. 12 The relevance of CAP for pediatric sleep is highlighted by age-related changes and alterations in several health conditions. 13-15 Even in the absence of disrupted conventional sleep organization, CAP is sensitive in identifying different patterns of stability within NREM sleep 16,17 but has not been investigated in otherwise healthy OW children. We aimed to fill this gap by comparing CAP patterns in otherwise healthy OW and

Research paper thumbnail of Extracting fuzzy rules from polysomnographic recordings for infant sleep classification

Abstract—A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for he... more Abstract—A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy infants of ages 6 mo and onward. The NFC takes five input patterns previously identi-fied on 20-s epochs from polysomnographic recordings and assigns them to one out of five possible classes: Wakefulness, REM-Sleep, Non-REM Sleep Stage 1, Stage 2, and Stage 3-4. The definite crite-rion for a sleep state or stage to be established is duration of at least 1 min. The data set consisted of a total of 14 continuous recordings of naturally occurring naps (average duration: 143 39 min), corresponding to a total of 6021 epochs. They were divided in a training, a validation and a test set with 7, 2, and 5 recordings, respectively. During supervised training, the system determined the fuzzy concepts associated to the inputs and the rules required for performing the classification, extracting knowledge from the training set, and pruning nonrelevant rules. Results on an inde-pendent test set a...

Research paper thumbnail of Iron-Deficiency Anemia is Associated with Altered Characteristics of Sleep Spindles in NREM Sleep in Infancy

Neurochemical Research, 2007

Objective To determine the effects of iron-deficiency anemia on the development of non-rapid-eye-... more Objective To determine the effects of iron-deficiency anemia on the development of non-rapid-eye-movement (NREM) sleep stages, as indexed by sleep spindles. Study design Patterns of sleep spindles during NREM sleep stages 2 and 3–4 (slow-wave-sleep, SWS) were compared in 26 otherwise healthy 6-month-old Chilean infants with iron-deficiency anemia and 18 non-anemic control infants. From polygraphic recordings, EEG activity was analyzed for sleep spindles to assess their number (density), duration, frequency, and inter-spindle interval. Results Iron-deficient anemic infants differed from the control group by having sleep spindles with reduced density, lower frequency, and longer inter-spindle intervals in NREM sleep stage 2 and SWS. Conclusions These results provide evidence of delayed sleep spindle patterns in iron-deficient anemic infants, suggesting that iron is an essential micronutrient for the normal progression of NREM sleep pattern development in the human.

Research paper thumbnail of 145 SLEEP-WAKE PATTERNS IN OVERWEIGHT PREPUBERTAL CHILDREN

Research paper thumbnail of HUMAN MILK (HM) FED INFANTS SHOW MORE ORGANIZED HEART RATE (HR) PATTERNS THAN FORMULA-FED (FF). 2258

Pediatric Research, 1996

To evaluate the effect of human milk on CNS functional development, we compared HR (RR intervals)... more To evaluate the effect of human milk on CNS functional development, we compared HR (RR intervals) an its spontaneous variability (HRV): high-, mid-, low-frequency bands as a function of sleep-wake states in HM and FF premature infants studied at 4 months. All ...

Research paper thumbnail of Sleep alterations and iron deficiency anemia in infancy

Sleep Medicine, 2010

In memoriam to our colleague and friend John L. Beard who contributed consistently to the science... more In memoriam to our colleague and friend John L. Beard who contributed consistently to the science in the iron/brain field Keywords: Iron deficiency anemia Infancy Sleep REM sleep NREM sleep Childhood a b s t r a c t Iron deficiency anemia (IDA) continues to be the most common single nutrient deficiency in the world. An estimated 20-25% of the world's infants have IDA, with at least as many having iron deficiency without anemia. Infants are at particular risk due to rapid growth and limited dietary sources of iron. We found that infants with IDA showed different motor activity patterning in all sleep-waking states and several differences in sleep states organization. Sleep alterations were still apparent years after correction of anemia with iron treatment in the absence of subsequent IDA. We suggest that altered sleep patterns may represent an underlying mechanism that interferes with optimal brain functioning during sleep and wakefulness in former IDA children.

Research paper thumbnail of 148 Heart rate variability patterns according to sleep-waking states in healthy prepubertal children: Lasting effects of iron deficiency anemia in infancy

Sleep Medicine, 2009

ABSTRACT Introduction: Iron deficiency is the most prevalent nutritional deficiency in the world.... more ABSTRACT Introduction: Iron deficiency is the most prevalent nutritional deficiency in the world. There is a consistent body of evidence on the lasting effects of early iron deficiency on several domains, including sleep-wake patterns. However, their potential effect on autonomic regulation is unknown. Objective: To evaluate heart rate patterns as a function of sleep-waking states in healthy prepubescents with (FIDA) and without (controls) iron deficiency anemia in infancy. Methods: We conducted nighttime polysomnographic recordings in 138 10-y children (FIDA= 88 and controls= 50, 40 and 46% female, respectively). From the electrocardiographic signal, the following patterns were established for each sleep-waking stage (NOREM sleep stages 1, 2 and 3-4 (or SWS), REM sleep and wakefulness): (i) RR interval (heart rate), (ii) heart rate variability (HRV) high-frequency component (HF or vagal predominance), and (iii) HRV low-frequency component (LF or sympathetic predominance); the sympathetic-vagal tone was established by the ratio LF/HF. Results: Compared with controls, the FIDA group presented shorter RR interval in NREM sleep stages 1 and 2 and wakefulness, and higher BF/AF in stage 2 of NOREM sleep (p <.05). When dividing the groups according to sex, FIDA girls had shorter RR interval in all NREM sleep stages relative to controls (p <.05). In turn, FIDA boys differ from controls by shorter RR in wakefulness and higher BF/AF in NREM sleep stage 2 and SWS (p <.05). Conclusions: These results show differences in heart rate and HRV patterns between healthy FIDA and control prepubescents, with higher sympathetic tone during wakefulness and NOREM sleep in the FIDA group. As a whole, they support the existence of long-lasting effects of early iron deficiency anemia on the autonomic regulation during sleep and wakefulness.

Research paper thumbnail of AUDITORY ACTIVITY PATTERNS IN HEALTHY PREMATURE INFANTS AT 4 MONTHS OF POST-TERM CORRECTED AGE. 7

Research paper thumbnail of Sleep and Neurofunctions Throughout Child Development: Lasting Effects of Early Iron Deficiency

Journal of Pediatric Gastroenterology and Nutrition, 2009

In memoriam to our colleague and friend John L. Beard who contributed consistently to the science... more In memoriam to our colleague and friend John L. Beard who contributed consistently to the science in the iron/brain field Keywords: Iron deficiency anemia Infancy Sleep REM sleep NREM sleep Childhood a b s t r a c t Iron deficiency anemia (IDA) continues to be the most common single nutrient deficiency in the world. An estimated 20-25% of the world's infants have IDA, with at least as many having iron deficiency without anemia. Infants are at particular risk due to rapid growth and limited dietary sources of iron. We found that infants with IDA showed different motor activity patterning in all sleep-waking states and several differences in sleep states organization. Sleep alterations were still apparent years after correction of anemia with iron treatment in the absence of subsequent IDA. We suggest that altered sleep patterns may represent an underlying mechanism that interferes with optimal brain functioning during sleep and wakefulness in former IDA children.

Research paper thumbnail of Dual approach for automated sleep spindles detection within EEG background activity in infant polysomnograms

An automated system for sleep spindles detection within EEG background activity, combining two di... more An automated system for sleep spindles detection within EEG background activity, combining two different approaches, is presented. The first approach applies detection criteria on the sigma-band filtered EEG signal, including fuzzy thresholds. The second approach mimics an expert's procedure. A sleep spindle detection is validated if both approaches agree. The method was applied on a testing set, consisting of continuous sleep recordings of two patients, totaling 1132 epochs (pages). A total of 803 sleep spindles events were marked by the experts. Results showed an 87.7% agreement between the detection system and the medical experts.

Research paper thumbnail of Iron Deficiency Anemia in Infancy: Long-Lasting Effects on Auditory and Visual System Functioning

Pediatric Research, 2003

Evoked potentials provide noninvasive measures of nerve transmission and CNS functioning. Auditor... more Evoked potentials provide noninvasive measures of nerve transmission and CNS functioning. Auditory brainstem responses (ABR) and visual evoked potentials (VEP) show dramatic changes in infancy, largely as a result of progressive myelination. Because iron is required for normal myelination, pathway transmission in these sensory systems might be affected by early iron deficiency. We previously reported evidence to that effect: infants with iron-deficiency anemia (IDA) had slower transmission through the auditory brainstem pathway, uncorrected by iron therapy. To determine long-term effects, ABR and/or VEP of healthy Chilean children who were treated for IDA or were nonanemic in infancy were compared at approximately 4 y of age. Absolute latencies for all ABR waves and interpeak latencies (except I-III interval) were significantly longer in former IDA children. Longer latency was also observed ABSTRACT 1

Research paper thumbnail of Spontaneous motor activity in human infants with iron-deficiency anemia

Early Human Development, 2002

This study compared spontaneous motor activity in 6-month-old Chilean infants with or without iro... more This study compared spontaneous motor activity in 6-month-old Chilean infants with or without iron-deficiency anemia (IDA) who were otherwise healthy. Activity was assessed in conjunction with polysomnographic recording during an afternoon nap in 11 infants with IDA and 15 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. Using actigraphs placed on the ankle, the frequency of movement units per minute was determined for each waking/sleep state. The total amount of time infants were in an alert -active state before and after the nap was used to calculate the proportion of movements/minute of waking. There were no differences between anemic and nonanemic infants in total recording time, duration of sleep, or motor activity during sleep. However, infants with IDA showed reduced motor activity during waking at all ages. The magnitude of the differences increased at 12 and 18 months. Thus, IDA was associated with reduced motor activity in infants even after iron treatment. It will be important to confirm these results in a larger sample and to determine the 24-h pattern of motor activity, since reduced motor activity may limit infants' opportunities to explore and learn from the social and physical environment. D

Research paper thumbnail of Twenty-four-hour motor activity in human infants with and without iron deficiency anemia

Early Human Development, 2002

Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The... more Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The aim of this study was to compare 24-h motor activity in the home in healthy 6-month-old infants with and without IDA. Activity was assessed via actigraphs on the leg during 24 continuous hours in 17 Chilean infants with IDA and 18 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. The frequency of movement units per minute was determined for each waking/sleep state during the day and night, and the duration of each state was computed. At 6 months of age, there were no differences between anemic and nonanemic infants in time per state. However, infants with IDA showed an overall increase in motor activity compared to controls. These differences were no longer observed at 12 and 18 months of age. Increased activity during the period of IDA raises the issue of a shared underlying mechanism with restless legs syndrome, a sensorimotor dysfunction where iron deficiency increases the severity of the symptoms and iron supplementation ameliorates them. Due to previous findings of decreased motor activity in the laboratory at 12 months during the waking time surrounding an afternoon nap, we also compared those data to a nap in the home. Infants with IDA were less active in the laboratory than in the home. The home versus laboratory results suggest that contextual factors affect the motor activity of IDA infants to a larger extent than controls. D

Research paper thumbnail of Assessment of autonomic dysfunction in iron-deficient anemic infants by cardio-respiratory demodulation

Abstracf-To assess the Autonomic Nervous System devel-oplllerit in iron-deficient anemic infants ... more Abstracf-To assess the Autonomic Nervous System devel-oplllerit in iron-deficient anemic infants during quiet sleep, wc used thc niodificd complcx dcmodulation analysis which allows for a continuous evaluation of the phase and ampli-tude relationships between the heart rate and ...

Research paper thumbnail of Polysomnographic pattern recognition for automated classification of sleep-waking states in infants

Medical & Biological Engineering & Computing, 2002

A robust, automated pattern recognition system for polysomnography data targeted to the sleep-wak... more A robust, automated pattern recognition system for polysomnography data targeted to the sleep-waking state and stage identification is presented. Five patterns were searched for: slow-delta and theta wave predominance in the background electro-encephalogram (EEG) activity; presence of sleep spindles in the EEG; presence of rapid eye movements in an electro-oculogram; and presence of muscle tone in an electromyogram. The performance of the automated system was measured indirectly by evaluating sleep staging, based on the experts' accepted methodology, to relate the detected patterns in infants over four months of post-term age. The set of sleep-waking classes included wakefulness, REM sleep and non-REM sleep stages I, II, and III-IV. Several noise and artifact rejection methods were implemented, including filters, fuzzy quality indices, windows of variable sizes and detectors of limb movements and wakefulness. Eleven polysomnographic recordings of healthy infants were studied. The ages of the subjects ranged from 6 to 13 months old. Six recordings counting 2665 epochs were included in the training set. Results on a test set (2369 epochs from five recordings) show an overall agreement of 87.7% (kappa 0.840) between the automated system and the human expert. These results show significant improvements compared with previous work.

Research paper thumbnail of DELAYED MATURATION OF AUDITORY BRAINSTEM RESPONSES IN IRONDEFICIENT ANEMIC INFANTS. ??? 104

Research paper thumbnail of Extracting Fuzzy Rules From Polysomnographic Recordings for Infant Sleep Classification

IEEE Transactions on Biomedical Engineering, 2006

A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy inf... more A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy infants of ages 6 mo and onward. The NFC takes five input patterns previously identified on 20-s epochs from polysomnographic recordings and assigns them to one out of five possible classes: Wakefulness, REM-Sleep, Non-REM Sleep Stage 1, Stage 2, and Stage 3-4. The definite criterion for a sleep state or stage to be established is duration of at least 1 min. The data set consisted of a total of 14 continuous recordings of naturally occurring naps (average duration: 143 39 min), corresponding to a total of 6021 epochs. They were divided in a training, a validation and a test set with 7, 2, and 5 recordings, respectively. During supervised training, the system determined the fuzzy concepts associated to the inputs and the rules required for performing the classification, extracting knowledge from the training set, and pruning nonrelevant rules. Results on an independent test set achieved 83 9 0 4% of expert agreement. The fuzzy rules obtained from the training examples without a priori information showed a high level of coincidence with the crisp rules stated by the experts, which are based on internationally accepted criteria. These results show that the NFC can be a valuable tool for implementing an automated sleep-wake classification system. Index Terms-ANFIS, fuzzy rule extraction, knowledge discovery, neural nets and expert systems, rule pruning, sleep classification.

Research paper thumbnail of Automated Sleep-Spindle Detection in Healthy Children Polysomnograms

IEEE Transactions on Biomedical Engineering, 2010

We present a new methodology to detect and characterize sleep spindles (SSs), based on the nonlin... more We present a new methodology to detect and characterize sleep spindles (SSs), based on the nonlinear algorithms, empirical-mode decomposition, and Hilbert-Huang transform, which provide adequate temporal and frequency resolutions in the electroencephalographic analysis. In addition, the application of fuzzy logic allows to emulate expert's procedures. Additionally, we built a database of 56 all-night polysomnographic recordings from children for training and testing, which is among the largest annotated databases published on the subject. The database was split into training (27 recordings), validation (10 recordings), and testing (19 recordings) datasets. The SS events were marked by sleep experts using visual inspection, and these marks were used as golden standard. The overall SS detection performance on the testing dataset of continuous all-night sleep recordings was 88.2% sensitivity, 89.7% specificity, and 11.9% false-positive (FP) rate. Considering only non-REM sleep stage 2, the results showed 92.2% sensitivity, 90.1% specificity, and 8.9% FP rate. In general, our system presents enhanced results when compared with most systems found in the literature, thus improving SS detection precision significantly without the need of hypnogram information.

Research paper thumbnail of Discrete wavelet transform applied to heart rate variability analysis in iron-deficient anemic infants

Abstmct-To assess the autonomic nervous system devel-opment in iron-deficient anemic infants duri... more Abstmct-To assess the autonomic nervous system devel-opment in iron-deficient anemic infants during sleep, we ap-plied the Discrete Wavelet Transform to perform heart rate variability analysis. The method provides suitable frequency resolution in low frequency domain, ...

Research paper thumbnail of Automated detection of apnea/hypopnea events in healthy children polysomnograms: Preliminary results

2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2013

A methodology to detect sleep apnea/hypopnea events in the respiratory signals of polysomnographi... more A methodology to detect sleep apnea/hypopnea events in the respiratory signals of polysomnographic recordings is presented. It applies empirical mode decomposition (EMD), Hilbert-Huang transform (HHT), fuzzy logic and signal preprocessing techniques for feature extraction, expert criteria and context analysis. EMD, HHT and fuzzy logic are used for artifact detection and preliminary detection of respiration signal zones with significant variations in the amplitude of the signal; feature extraction, expert criteria and context analysis are used to characterize and validate the respiratory events. An annotated database of 30 all-night polysomnographic recordings, acquired from 30 healthy ten-year-old children, was divided in a training set of 15 recordings (485 sleep apnea/hypopnea events), a validation set of five recordings (109 sleep apnea/hypopnea events), and a testing set of ten recordings (281 sleep apnea/hypopnea events). The overall detection performance on the testing data set was 89.7% sensitivity and 16.3% false-positive rate. The next step is to include discrimination among apneas, hypopneas and respiratory pauses.

Research paper thumbnail of Sleep Cyclic Alternating Pattern in Otherwise Healthy Overweight School-Age Children

SLEEP, 2014

Sleep Cyclic Alternating Pattern in Overweight Children-Chamorro et al INTRODUCTION Chronic and m... more Sleep Cyclic Alternating Pattern in Overweight Children-Chamorro et al INTRODUCTION Chronic and moderate sleep debt is an increasingly common feature across societies and age groups. 1,2 There is mounting evidence that nighttime sleep patterns relate to body weight in pediatric groups. Epidemiological studies in children consistently show an inverse relation between sleep duration and body mass index (BMI). 3-7 Polysomnographic (PSG) studies show decreased sleep amount, sleep efficiency, and REM sleep in overweight (OW) subjects. 8-11 However, few studies have assessed sleep patterns within the sleep-obesity frame in the absence of apparent sleep alterations. Sleep cyclic alternating pattern (CAP) is a physiologic oscillatory phenomenon occurring during NREM sleep. 12 The relevance of CAP for pediatric sleep is highlighted by age-related changes and alterations in several health conditions. 13-15 Even in the absence of disrupted conventional sleep organization, CAP is sensitive in identifying different patterns of stability within NREM sleep 16,17 but has not been investigated in otherwise healthy OW children. We aimed to fill this gap by comparing CAP patterns in otherwise healthy OW and

Research paper thumbnail of Extracting fuzzy rules from polysomnographic recordings for infant sleep classification

Abstract—A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for he... more Abstract—A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy infants of ages 6 mo and onward. The NFC takes five input patterns previously identi-fied on 20-s epochs from polysomnographic recordings and assigns them to one out of five possible classes: Wakefulness, REM-Sleep, Non-REM Sleep Stage 1, Stage 2, and Stage 3-4. The definite crite-rion for a sleep state or stage to be established is duration of at least 1 min. The data set consisted of a total of 14 continuous recordings of naturally occurring naps (average duration: 143 39 min), corresponding to a total of 6021 epochs. They were divided in a training, a validation and a test set with 7, 2, and 5 recordings, respectively. During supervised training, the system determined the fuzzy concepts associated to the inputs and the rules required for performing the classification, extracting knowledge from the training set, and pruning nonrelevant rules. Results on an inde-pendent test set a...

Research paper thumbnail of Iron-Deficiency Anemia is Associated with Altered Characteristics of Sleep Spindles in NREM Sleep in Infancy

Neurochemical Research, 2007

Objective To determine the effects of iron-deficiency anemia on the development of non-rapid-eye-... more Objective To determine the effects of iron-deficiency anemia on the development of non-rapid-eye-movement (NREM) sleep stages, as indexed by sleep spindles. Study design Patterns of sleep spindles during NREM sleep stages 2 and 3–4 (slow-wave-sleep, SWS) were compared in 26 otherwise healthy 6-month-old Chilean infants with iron-deficiency anemia and 18 non-anemic control infants. From polygraphic recordings, EEG activity was analyzed for sleep spindles to assess their number (density), duration, frequency, and inter-spindle interval. Results Iron-deficient anemic infants differed from the control group by having sleep spindles with reduced density, lower frequency, and longer inter-spindle intervals in NREM sleep stage 2 and SWS. Conclusions These results provide evidence of delayed sleep spindle patterns in iron-deficient anemic infants, suggesting that iron is an essential micronutrient for the normal progression of NREM sleep pattern development in the human.

Research paper thumbnail of 145 SLEEP-WAKE PATTERNS IN OVERWEIGHT PREPUBERTAL CHILDREN

Research paper thumbnail of HUMAN MILK (HM) FED INFANTS SHOW MORE ORGANIZED HEART RATE (HR) PATTERNS THAN FORMULA-FED (FF). 2258

Pediatric Research, 1996

To evaluate the effect of human milk on CNS functional development, we compared HR (RR intervals)... more To evaluate the effect of human milk on CNS functional development, we compared HR (RR intervals) an its spontaneous variability (HRV): high-, mid-, low-frequency bands as a function of sleep-wake states in HM and FF premature infants studied at 4 months. All ...

Research paper thumbnail of Sleep alterations and iron deficiency anemia in infancy

Sleep Medicine, 2010

In memoriam to our colleague and friend John L. Beard who contributed consistently to the science... more In memoriam to our colleague and friend John L. Beard who contributed consistently to the science in the iron/brain field Keywords: Iron deficiency anemia Infancy Sleep REM sleep NREM sleep Childhood a b s t r a c t Iron deficiency anemia (IDA) continues to be the most common single nutrient deficiency in the world. An estimated 20-25% of the world's infants have IDA, with at least as many having iron deficiency without anemia. Infants are at particular risk due to rapid growth and limited dietary sources of iron. We found that infants with IDA showed different motor activity patterning in all sleep-waking states and several differences in sleep states organization. Sleep alterations were still apparent years after correction of anemia with iron treatment in the absence of subsequent IDA. We suggest that altered sleep patterns may represent an underlying mechanism that interferes with optimal brain functioning during sleep and wakefulness in former IDA children.

Research paper thumbnail of 148 Heart rate variability patterns according to sleep-waking states in healthy prepubertal children: Lasting effects of iron deficiency anemia in infancy

Sleep Medicine, 2009

ABSTRACT Introduction: Iron deficiency is the most prevalent nutritional deficiency in the world.... more ABSTRACT Introduction: Iron deficiency is the most prevalent nutritional deficiency in the world. There is a consistent body of evidence on the lasting effects of early iron deficiency on several domains, including sleep-wake patterns. However, their potential effect on autonomic regulation is unknown. Objective: To evaluate heart rate patterns as a function of sleep-waking states in healthy prepubescents with (FIDA) and without (controls) iron deficiency anemia in infancy. Methods: We conducted nighttime polysomnographic recordings in 138 10-y children (FIDA= 88 and controls= 50, 40 and 46% female, respectively). From the electrocardiographic signal, the following patterns were established for each sleep-waking stage (NOREM sleep stages 1, 2 and 3-4 (or SWS), REM sleep and wakefulness): (i) RR interval (heart rate), (ii) heart rate variability (HRV) high-frequency component (HF or vagal predominance), and (iii) HRV low-frequency component (LF or sympathetic predominance); the sympathetic-vagal tone was established by the ratio LF/HF. Results: Compared with controls, the FIDA group presented shorter RR interval in NREM sleep stages 1 and 2 and wakefulness, and higher BF/AF in stage 2 of NOREM sleep (p <.05). When dividing the groups according to sex, FIDA girls had shorter RR interval in all NREM sleep stages relative to controls (p <.05). In turn, FIDA boys differ from controls by shorter RR in wakefulness and higher BF/AF in NREM sleep stage 2 and SWS (p <.05). Conclusions: These results show differences in heart rate and HRV patterns between healthy FIDA and control prepubescents, with higher sympathetic tone during wakefulness and NOREM sleep in the FIDA group. As a whole, they support the existence of long-lasting effects of early iron deficiency anemia on the autonomic regulation during sleep and wakefulness.

Research paper thumbnail of AUDITORY ACTIVITY PATTERNS IN HEALTHY PREMATURE INFANTS AT 4 MONTHS OF POST-TERM CORRECTED AGE. 7

Research paper thumbnail of Sleep and Neurofunctions Throughout Child Development: Lasting Effects of Early Iron Deficiency

Journal of Pediatric Gastroenterology and Nutrition, 2009

In memoriam to our colleague and friend John L. Beard who contributed consistently to the science... more In memoriam to our colleague and friend John L. Beard who contributed consistently to the science in the iron/brain field Keywords: Iron deficiency anemia Infancy Sleep REM sleep NREM sleep Childhood a b s t r a c t Iron deficiency anemia (IDA) continues to be the most common single nutrient deficiency in the world. An estimated 20-25% of the world's infants have IDA, with at least as many having iron deficiency without anemia. Infants are at particular risk due to rapid growth and limited dietary sources of iron. We found that infants with IDA showed different motor activity patterning in all sleep-waking states and several differences in sleep states organization. Sleep alterations were still apparent years after correction of anemia with iron treatment in the absence of subsequent IDA. We suggest that altered sleep patterns may represent an underlying mechanism that interferes with optimal brain functioning during sleep and wakefulness in former IDA children.

Research paper thumbnail of Dual approach for automated sleep spindles detection within EEG background activity in infant polysomnograms

An automated system for sleep spindles detection within EEG background activity, combining two di... more An automated system for sleep spindles detection within EEG background activity, combining two different approaches, is presented. The first approach applies detection criteria on the sigma-band filtered EEG signal, including fuzzy thresholds. The second approach mimics an expert's procedure. A sleep spindle detection is validated if both approaches agree. The method was applied on a testing set, consisting of continuous sleep recordings of two patients, totaling 1132 epochs (pages). A total of 803 sleep spindles events were marked by the experts. Results showed an 87.7% agreement between the detection system and the medical experts.

Research paper thumbnail of Iron Deficiency Anemia in Infancy: Long-Lasting Effects on Auditory and Visual System Functioning

Pediatric Research, 2003

Evoked potentials provide noninvasive measures of nerve transmission and CNS functioning. Auditor... more Evoked potentials provide noninvasive measures of nerve transmission and CNS functioning. Auditory brainstem responses (ABR) and visual evoked potentials (VEP) show dramatic changes in infancy, largely as a result of progressive myelination. Because iron is required for normal myelination, pathway transmission in these sensory systems might be affected by early iron deficiency. We previously reported evidence to that effect: infants with iron-deficiency anemia (IDA) had slower transmission through the auditory brainstem pathway, uncorrected by iron therapy. To determine long-term effects, ABR and/or VEP of healthy Chilean children who were treated for IDA or were nonanemic in infancy were compared at approximately 4 y of age. Absolute latencies for all ABR waves and interpeak latencies (except I-III interval) were significantly longer in former IDA children. Longer latency was also observed ABSTRACT 1

Research paper thumbnail of Spontaneous motor activity in human infants with iron-deficiency anemia

Early Human Development, 2002

This study compared spontaneous motor activity in 6-month-old Chilean infants with or without iro... more This study compared spontaneous motor activity in 6-month-old Chilean infants with or without iron-deficiency anemia (IDA) who were otherwise healthy. Activity was assessed in conjunction with polysomnographic recording during an afternoon nap in 11 infants with IDA and 15 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. Using actigraphs placed on the ankle, the frequency of movement units per minute was determined for each waking/sleep state. The total amount of time infants were in an alert -active state before and after the nap was used to calculate the proportion of movements/minute of waking. There were no differences between anemic and nonanemic infants in total recording time, duration of sleep, or motor activity during sleep. However, infants with IDA showed reduced motor activity during waking at all ages. The magnitude of the differences increased at 12 and 18 months. Thus, IDA was associated with reduced motor activity in infants even after iron treatment. It will be important to confirm these results in a larger sample and to determine the 24-h pattern of motor activity, since reduced motor activity may limit infants' opportunities to explore and learn from the social and physical environment. D

Research paper thumbnail of Twenty-four-hour motor activity in human infants with and without iron deficiency anemia

Early Human Development, 2002

Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The... more Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The aim of this study was to compare 24-h motor activity in the home in healthy 6-month-old infants with and without IDA. Activity was assessed via actigraphs on the leg during 24 continuous hours in 17 Chilean infants with IDA and 18 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. The frequency of movement units per minute was determined for each waking/sleep state during the day and night, and the duration of each state was computed. At 6 months of age, there were no differences between anemic and nonanemic infants in time per state. However, infants with IDA showed an overall increase in motor activity compared to controls. These differences were no longer observed at 12 and 18 months of age. Increased activity during the period of IDA raises the issue of a shared underlying mechanism with restless legs syndrome, a sensorimotor dysfunction where iron deficiency increases the severity of the symptoms and iron supplementation ameliorates them. Due to previous findings of decreased motor activity in the laboratory at 12 months during the waking time surrounding an afternoon nap, we also compared those data to a nap in the home. Infants with IDA were less active in the laboratory than in the home. The home versus laboratory results suggest that contextual factors affect the motor activity of IDA infants to a larger extent than controls. D

Research paper thumbnail of Assessment of autonomic dysfunction in iron-deficient anemic infants by cardio-respiratory demodulation

Abstracf-To assess the Autonomic Nervous System devel-oplllerit in iron-deficient anemic infants ... more Abstracf-To assess the Autonomic Nervous System devel-oplllerit in iron-deficient anemic infants during quiet sleep, wc used thc niodificd complcx dcmodulation analysis which allows for a continuous evaluation of the phase and ampli-tude relationships between the heart rate and ...

Research paper thumbnail of Polysomnographic pattern recognition for automated classification of sleep-waking states in infants

Medical & Biological Engineering & Computing, 2002

A robust, automated pattern recognition system for polysomnography data targeted to the sleep-wak... more A robust, automated pattern recognition system for polysomnography data targeted to the sleep-waking state and stage identification is presented. Five patterns were searched for: slow-delta and theta wave predominance in the background electro-encephalogram (EEG) activity; presence of sleep spindles in the EEG; presence of rapid eye movements in an electro-oculogram; and presence of muscle tone in an electromyogram. The performance of the automated system was measured indirectly by evaluating sleep staging, based on the experts' accepted methodology, to relate the detected patterns in infants over four months of post-term age. The set of sleep-waking classes included wakefulness, REM sleep and non-REM sleep stages I, II, and III-IV. Several noise and artifact rejection methods were implemented, including filters, fuzzy quality indices, windows of variable sizes and detectors of limb movements and wakefulness. Eleven polysomnographic recordings of healthy infants were studied. The ages of the subjects ranged from 6 to 13 months old. Six recordings counting 2665 epochs were included in the training set. Results on a test set (2369 epochs from five recordings) show an overall agreement of 87.7% (kappa 0.840) between the automated system and the human expert. These results show significant improvements compared with previous work.

Research paper thumbnail of DELAYED MATURATION OF AUDITORY BRAINSTEM RESPONSES IN IRONDEFICIENT ANEMIC INFANTS. ??? 104

Research paper thumbnail of Extracting Fuzzy Rules From Polysomnographic Recordings for Infant Sleep Classification

IEEE Transactions on Biomedical Engineering, 2006

A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy inf... more A neuro-fuzzy classifier (NFC) of sleep-wake states and stages has been developed for healthy infants of ages 6 mo and onward. The NFC takes five input patterns previously identified on 20-s epochs from polysomnographic recordings and assigns them to one out of five possible classes: Wakefulness, REM-Sleep, Non-REM Sleep Stage 1, Stage 2, and Stage 3-4. The definite criterion for a sleep state or stage to be established is duration of at least 1 min. The data set consisted of a total of 14 continuous recordings of naturally occurring naps (average duration: 143 39 min), corresponding to a total of 6021 epochs. They were divided in a training, a validation and a test set with 7, 2, and 5 recordings, respectively. During supervised training, the system determined the fuzzy concepts associated to the inputs and the rules required for performing the classification, extracting knowledge from the training set, and pruning nonrelevant rules. Results on an independent test set achieved 83 9 0 4% of expert agreement. The fuzzy rules obtained from the training examples without a priori information showed a high level of coincidence with the crisp rules stated by the experts, which are based on internationally accepted criteria. These results show that the NFC can be a valuable tool for implementing an automated sleep-wake classification system. Index Terms-ANFIS, fuzzy rule extraction, knowledge discovery, neural nets and expert systems, rule pruning, sleep classification.

Research paper thumbnail of Automated Sleep-Spindle Detection in Healthy Children Polysomnograms

IEEE Transactions on Biomedical Engineering, 2010

We present a new methodology to detect and characterize sleep spindles (SSs), based on the nonlin... more We present a new methodology to detect and characterize sleep spindles (SSs), based on the nonlinear algorithms, empirical-mode decomposition, and Hilbert-Huang transform, which provide adequate temporal and frequency resolutions in the electroencephalographic analysis. In addition, the application of fuzzy logic allows to emulate expert's procedures. Additionally, we built a database of 56 all-night polysomnographic recordings from children for training and testing, which is among the largest annotated databases published on the subject. The database was split into training (27 recordings), validation (10 recordings), and testing (19 recordings) datasets. The SS events were marked by sleep experts using visual inspection, and these marks were used as golden standard. The overall SS detection performance on the testing dataset of continuous all-night sleep recordings was 88.2% sensitivity, 89.7% specificity, and 11.9% false-positive (FP) rate. Considering only non-REM sleep stage 2, the results showed 92.2% sensitivity, 90.1% specificity, and 8.9% FP rate. In general, our system presents enhanced results when compared with most systems found in the literature, thus improving SS detection precision significantly without the need of hypnogram information.

Research paper thumbnail of Discrete wavelet transform applied to heart rate variability analysis in iron-deficient anemic infants

Abstmct-To assess the autonomic nervous system devel-opment in iron-deficient anemic infants duri... more Abstmct-To assess the autonomic nervous system devel-opment in iron-deficient anemic infants during sleep, we ap-plied the Discrete Wavelet Transform to perform heart rate variability analysis. The method provides suitable frequency resolution in low frequency domain, ...