Effect of prenatal cocaine on respiration, heart rate, and sudden infant death syndrome.

We studied 114 neonates by pneumocardiogram recordings in order to examine the effects of cocaine with and without opiate exposure on neonatal respiration, heart rate, apparent life threatening events (ALTE), and sudden infant death syndrome (SIDS). In full-term infants exposed to cocaine without opiates we found increased longest apnea duration and more episodes of bradycardia, but decreased periodic breathing and average heart rate than in control full-term infants. Term infants prenatally exposed to cocaine with opiates also had less periodic breathing. Preterm infants exposed to cocaine with and without opiates had decreased apnea density and periodic breathing compared with preterm controls. Discriminant analysis to determine whether perinatal asphyxia or exposure to other drugs could predict cardiorespiratory abnormalities showed no consistent relationship. In 72 of 114 infants available for follow-up, no ALTE occurred but two were lost to SIDS. Our data support the hypothesis that prenatal cocaine exposure may perturb, albeit subtly, the maturation of respiratory control, resulting in disruption of postnatal respiration.     

Altered autonomic function and reduced arousability in apparent life-threatening event infants with obstructive sleep apnea

The aim of this study was to examine cardiorespiratory control in infants presenting with an apparent life-threatening event (ALTE). We performed six to eight 45 degrees head-up tilts in 10 ALTE infants (age, 14 +/- 3 weeks) and 12 age-matched control subjects during slow wave sleep and rapid eye movement sleep (REM). All infants underwent full overnight polygraphic sleep recordings with noninvasive measurement of beat-to-beat blood pressure. All control infants had normal sleep breathing. In contrast, 5 of the 10 ALTE infants had more than two obstructive apneas per hour of sleep, with short hypoxic episodes (obstructive sleep apnea [OSA]). In slow wave sleep, in response to the tilt, the ALTE infants with OSA showed a reduced heart rate response, and three of the five showed a marked postural hypotension. The ALTE infants with OSA also had altered heart rate and blood pressure variability and an increased arousal threshold in REM (p = 0.0002). By contrast, those ALTE infants with normal sleep breathing had cardiovascular and arousal responses similar to those of the control infants. We conclude that a number of ALTE infants with OSA have abnormal cardiovascular autonomic control that, combined with their decreased arousability in REM, may provide an explanation for the ALTE episodes.     

Prospective pneumogram recordings in preterm infants with and without clinical apnea and bradycardia

Recordings of breathing movements and heart rate (pneumograms) were obtained prospectively in 89 preterm infants at 0-28 days of age to determine if those who develop apnea and/or bradycardia with cyanosis (Group 1) differ from those who do not (Group 2). The 148 pneumograms were blindly analyzed for periodic breathing, bradycardia, longest apnea, and quiet time. Pneumograms were compared between groups at weekly intervals during the first 4 weeks. Significant differences were found among infants who had pneumograms recorded during the 1st week of life. Although mean gestational age and mean postconceptional age at recording were similar, birthweight and weight at recording were significantly lower in Group 1 infants. Total time spent in periodic breathing and the longest episode of periodic breathing were significantly greater in Group 1 infants. Logistic regression analysis revealed significant independent relationships between birthweight and periodic breathing at less than or equal to 7 days of age and the occurrence of symptomatic apnea and/or bradycardia. It is concluded that preterm infants who develop apnea and/or bradycardia with cyanosis have a lower mean birthweight and mean weight at recording at less than or equal to 7 days of age than similar asymptomatic preterm infants. Periodic breathing at less than or equal to 7 days of age is associated with the occurrence of clinical symptoms of apnea and/or bradycardia. Normal pneumogram values for groups of 6-21 asymptomatic preterm infants are provided for the first 4 weeks of life.     

From apnea of infancy to obstructive sleep apnea syndrome in the young child.

Obstructive sleep apnea syndrome (OSAS) and heavy snoring during sleep, without sleep apnea, has been well described in children and adults. We report a case series of 25 full-term infants, prospectively obtained from a database of nearly 700 "apparent life-threatening event" (ALTE) cases, who presented between 3 weeks and 4 1/2 months of age an ALTE and who progressively developed more florid symptomatology and polygraphic findings. All of them were classified as OSAS patients by five years of age. These index cases are compared with two other ALTE infant groups followed in parallel during the first year of life but whose symptoms were short-lived. The index cases presented more frequently a positive family history of OSAS and an early report of snoring or noisy breathing during sleep. Usage of an esophageal balloon to monitor esophageal pressure (Pes) and usage of nasal continuous positive airway pressure (CPAP) as a test may help in the early recognition of these infants, who appear to make more effort to breathe during sleep, based on the indirect evidence of Pes measurements. It is suggested that anatomic features, including a small posterior airway space leading to an abnormal degree of upper airway resistance, may be the cause of the symptoms presented by these infants. Considering the parental anxiety generated by persistence of symptoms after the first year of life in ALTE infants, recognition of this subgroup is important.     

Apnea and periodic breathing in normal full-term infants during the first twelve months

The pediatric pneumogram is a frequently used tool in the diagnosis and management of apnea during infancy. We analyzed 287 pneumographic recordings from 123 full-term infants (63 males) obtained during the first 12 months of life to establish normative values for apnea, periodic breathing, and bradycardia. The results of the analysis were compared by sex and age. The number of infants who exhibited periodic breathing decreased significantly over time (78% at 0-2 weeks vs 29% at 39-52 weeks; P less than 0.05). However, for those infants who did breathe periodically, the percent of sleep time spent in this breathing pattern did not change with age. No apnea greater than or equal to 15 seconds was recorded in any infant, and apnea density (total apnea greater than or equal to 10 seconds in minutes/100 minutes sleep time) did not change with age or sex. Using our definitions, no bradycardia was identified. Normal full-term infants occasionally have apnea of 10, 11, or 12 seconds, and, until 6 months of age, the majority will have a small amount of periodic breathing (less than 1% of sleep time) during sleep at home.     

Periodic breathing in preterm infants: influence of bronchopulmonary dysplasia and theophylline

Periodic breathing (PB) has been studied extensively in both normal term infants and term infants presumed to be at high risk for sudden infant death syndrome (SIDS); however, little is known about the incidence and significance of PB in preterm infants. Twenty-four hour impedance pneumograms were obtained from 108 preterm infants prior to their discharge from the nursery and four PB parameters (%PB, No. of episodes of PB/100 min, mean duration of PB episode length, and duration of the longest episode of PB) were quantified in each recording. Control infants who were asymptomatic for apnea had the highest PB parameter values (%PB, 12.0; No. episodes/100 min, 8.6; mean duration, 1.2 min; and longest episode, 7.3 min); infants with bronchopulmonary dysplasia (BPD) showed dramatic decreases in all PB parameters, with a median %PB of 1/16 of the control population. Theophylline use was associated with a significant decrease in PB parameter values only in infants without BPD. Central apneas greater than 15 s did not vary significantly as a function of BPD, theophylline, or postconceptional age. We conclude that the clinical status of preterm infants significantly influences PB parameter values and must be taken into account in the interpretation of pneumograms, for decision-making about home cardiorespiratory monitoring, and in assigning risk for SIDS.     

Toxigenic Escherichia coli associated with sudden infant death syndrome

The role of Escherichia coli as a cause of sudden infant death syndrome was investigated prospectively. Strains of E. coli producing the heat labile enterotoxin (LT) or the Vero-cell cytotoxin (VT) were isolated from the intestinal contents of 21/46 infants who died from sudden infant death syndrome (SIDS). None were found in the contemporaneously sampled faeces of 24 normal live infants in the same area. Live infants were used as controls in the absence of dead infants who had not died of SIDS. This high incidence of toxigenic E. coli among the SIDS infants versus the low incidence in controls, together with the general rarity of finding such toxigenic E. coli in the community of a temperate developed country, made us conclude that there may be a causal relationship between toxigenic E. coli and SIDS. The O and H serotypes of the toxigenic E. coli associated with SIDS infants tended not to be those normally considered to be toxigenic. The toxigenicity appeared to be relatively labile. It is suggested that SIDS may be associated with the infant either acquiring these unusual types of E. coli or more likely that its normal resident E. coli acquire the plasmids to produce these toxins.     

Characterization of successful and failed autoresuscitation in human infants,including those dying of SIDS

Our purpose was to identify and further characterize physiologic mechanisms relevant to autoresuscitation from hypoxic apnea in infants dying suddenly and unexpectedly. We studied cardiorespiratory recordings of 24 infants (age range, 0.8-21 months) who died suddenly while being monitored at home. These recordings were analyzed for features indicated by studies in animal models to be characteristic of hypoxic gasping, and of recovery from bradycardia and apnea associated with gasping (e.g., autoresuscitation). Findings in 5 infants diagnosed as having sudden infant death syndrome were compared with 6 non-SIDS infants whose deaths resulted from other conditions. Additionally, we studied 15 healthy infants during sleep, using home monitor and other respiratory recording techniques, in order to obtain comparison data. We found in recordings from 23 of 24 subjects that hypoxic gasps with characteristic features occurred immediately preceding death. A unique pattern of complex, closely spaced gasps ("double" or "triple" gasps) was present in many subjects. Evidence of partially successful autoresuscitation closely following one or more gasps occurred in 11 subjects, while another 4 had evidence of complete autoresuscitation with return of normal heart rate and resolution of apnea on one or more occasions. Significant differences between SIDS infants and those dying from other causes included increased occurrence of complex gasps and decreased occurrence of partial or complete autoresuscitation in the SIDS infants. The non-SIDS cases were different from the SIDS cases in that only one had "double" gasps (n = 7), while none had "triple" gasps, as compared with 4 out of 5 SIDS cases with these patterns (P < 0.05, chi-square). Also, in contrast with the SIDS cases, more of the cases with specific postmortem diagnoses had evidence of partial (5 out of 6 cases) or complete (1 out of 6 cases) autoresuscitation (P < 0.05, chi-square). We conclude that partial or complete autoresuscitation by gasping is not uncommon in moribund infants during the first year of life. Failure of autoresuscitation mechanisms other than failure to initiate gasping may be characteristic of infants dying of SIDS. Some SIDS infants appear to be different from infants dying with other diagnoses with respect to efficacy and characteristics of hypoxic gasping.     

Comparison of 2-channel and 4-channel pneumograms.

To determine whether the addition of air flow and O2 saturation (SaO2) channels improves sensitivity of the pneumogram in identifying cardiorespiratory pattern abnormalities, 2- and 4-channel pneumograms (PG-2 and PG-4) were simultaneously recorded in 91 consecutive infants. Forty-one infants (45%) had cardiorespiratory symptoms, and 50 were asymptomatic. Pneumograms were considered abnormal for any of the following: apnea greater than or equal to 20 seconds, heart rate less than 80 bpm for greater than 5 seconds in preterm and less than 60 bpm in full-term infants (bradycardia), shorter apnea with bradycardia or desaturation, periodic breathing greater than 7% of total sleep time in preterm and greater than 4% in full-term infants, or SaO2 less than 85% for greater than 5 seconds. Both recordings were normal in 72% of infants and abnormal in 24%. In only 4% were the PG-4 abnormal when the PG-2 were normal, in all instances due to minimum SaO2 levels of 77-84% for 5-19 seconds associated with central apnea of intermediate duration (three infants) or with mixed apnea. The difference in frequency of abnormal results between the PG-2 and PG-4 recordings was not statistically significant (X2). In conclusion, although PG-4 do increase the scope of physiological information obtained in infants with cardiorespiratory events, this short-term study does not establish whether this increase results in any long-term benefits. Further, at least in this number and these types of at-risk infants, PG-4 do not improve the sensitivity of cardiorespiratory recordings for detecting abnormalities.     

Regulation of ventilation before and after sleep in patients with obstructive sleep apnoea

The objective was to examine whether abnormal breathing during sleep may affect regulation of ventilation after awakening in patients with obstructive sleep apnoea (OSAS). In 19 patients with OSA and 12 normal subjects we examined ventilatory responses to hypoxia (HVR) and to hypercapnia (HCVR) before and after sleep (BS and AS), and compared the changes in ventilatory responses with respiratory events during sleep. In the OSA group, the values of resting ventilation were significantly smaller in AS than those in BS and end-tidal partial pressure of CO2 in arterial blood (Pco2) (PETCO2) rose significantly from BS to AS. The slopes of the HVR or HCVR did not differ between BS and AS. However, both the response lines shifted downward and minute ventilation (VE)80 (VE at arterial oxygen saturation (Sao2) of 80%) in HVR and VE60 (VE at PETCO2 of 60 mmHg) in HCVR decreased significantly from BS to AS. The percentage changes of VE80 and VE60 were significantly correlated with mean Sao2, total sleep time below Sao2 of 90% and lowest Sao2 during sleep. However, in normal subjects we observed no circadian variation in their ventilatory responses. These data support the hypothesis that repeated episodes of nocturnal hypoxia and hypercapnia may modify the regulation of ventilation after awakening in patients with OSA.     

Transplacentally acquired caffeine and the occurrence of apnea, bradycardia, and periodic breathing in preterm infants: preliminary communication

Cord blood caffeine concentrations were measured by high-pressure liquid chromatography in 79 preterm infants. Eleven infants (14%) had detectable caffeine concentrations ranging from 1.1 to 3.7 micrograms/mL (means +/- SD = 2.5 +/- 0.8), and 68 infants had no measurable caffeine. Seven infants with detectable caffeine (group 1) had impedance pneumograms recorded before 2 weeks of age. Each infant in group 1 was matched with two infants without detectable caffeine by birthweight, gestational age, and chronologic age at pneumogram recording to yield a control group (group 2) of 14 infants. Comparison of the groups using quantitative measures of apnea, bradycardia, and periodic breathing obtained from pneumogram analysis and the incidence of monitor alarms on bedside nursing records showed no significant differences. Thus, caffeine was present infrequently and at low concentrations at birth in 79 preterm infants. The amount of apnea, bradycardia, and periodic breathing experienced before 2 weeks of age in 7 preterm infants with detectable cord blood caffeine was not different from that in 14 similar infants without caffeine. Future studies are planned to examine the relationship between postnatal changes in transplacentally acquired methylxanthine concentrations and quantitative measures of apnea, bradycardia, and periodic breathing in a larger number of preterm infants without cardiorespiratory disease.     

Pathogenesis of apparent life-threatening events in infants with esophageal atresia

Many infants with a repaired esophageal atresia (EA) undergo fundoplication, aortopexy, or glossopexy because the mechanisms most responsible for airway obstruction and/or apparent life-threatening event (AO/ALTE) syndrome are considered to be gastroesophageal reflux (GER), tracheal compression (TC), or obstructive apnea, respectively. In the present study, we investigated whether these mechanisms are independent or interrelated. We developed a database of 120 consecutive patients with EA treated by the senior author between 1967-2002. We studied the clinical manifestations of patients with a cervical esophagostomy and/or blind lower esophageal stump, which ruled out TC and/or proximal esophageal GER as a mechanism for AO/ALTE. Of 25 neonates who underwent section/ligation of lower tracheo-esophageal fistula and/or feeding gastrostomy, 10 critically ill neonates died. Of 15 survivors, 9 infants had a feeding gastrostomy without an esophagostomy. Of these, 6 infants presented one or more episodes of AO, and 8 presented ALTE with or without AO. Subsequently, 5 of the 9 infants underwent an esophagostomy. Eventually, 11 infants had a feeding gastrostomy with an esophagostomy. Of the latter, 5 infants presented one or more episodes of AO, and 6 presented ALTE without AO. In conclusion, oral feeding, proximal esophageal GER, and TC are not essential for AO/ALTE syndrome to occur. They are probably factors which offer evidence of an underlying problem with control of upper airway patency.     

Sleep apnea and hypoxemia in recently weaned premature infants with and without bronchopulmonary dysplasia

Infants with bronchopulmonary dysplasia (BPD) experience significant hypoxemia. Apnea indices and oxygen saturation levels of ten infants with BPD were compared to ten healthy premature infants who were evaluated to rule out apnea or bradycardia prior to discharge from the hospital. Infants with BPD who had been recently (less than 7 days) weaned from supplemental oxygen were evaluated on and off supplemental oxygen. Premature controls had never received oxygen nor ventilation assistance. Infants with BPD were born significantly more prematurely (28.1 +/- 1.0 vs. 33.0 +/- 3.9 weeks; P = 0.0012) while chronologic ages at the time of evaluation, adjusted for prematurity, were equal (37.1 +/- 3.1 vs. 38.0 +/- 2.7 weeks). Comparisons of apnea densities (expressed as percent of sleep time) between BPD and non-BPD prematures revealed the following: neither the average obstructive apnea (0.15 +/- 0.36 vs. 0.14 +/- 0.31) nor periodic breathing densities (6.0 +/- 8.56 vs. 10.2 +/- 5.84) were different. Infants with BPD experienced significantly more central apnea (0.62 +/- 0.34 vs. 0.16 +/- 0.11; P = 0.003) than did non-BPD prematures. Average oxygen saturation levels were significantly less among BPD vs. non-BPD prematures (90.0 +/- 10.18% vs. 95.7 +/- 4.33%; P = 0.033). When supplemented with oxygen, BPD prematures had significantly higher saturation (X = 94.5%) than when breathing room air (X = 90.0%). Both central apnea and periodic breathing densities declined significantly with this improvement in saturation (0.64 vs. 0.04% and 6.0 vs. 1.4%, respectively). These data suggest that saturation status may indicate central respiratory stability in chronic lung disease.     

Effect of hypercapnia on ventilatory response to intravenous nicotine administration in anesthetized dogs

We studied the effects of hypercapnia on the ventilatory response to nicotine in thirty anesthetized mongrel dogs. Ventilatory (VE) and occlusion pressure (P0.2) changes were assessed before and after intravenous injection of nicotine at concentrations of 1, 4, 16 and 64 micrograms/kg in four different groups of five dogs each. An end-tidal CO2 (PETCO2) was set at 40 mm Hg or 60 mm Hg by inspiration of 7% CO2 in oxygen through a non-rebreathing valve. With PETCO2 maintained at 40 mm Hg, P0.2 had increased 1 min after nicotine injection from 1 to 16 micrograms/kg in a dose-dependent manner, and a subsequent decrease in P0.2 below the initial value was observed at around 4 min. Injection of 64 micrograms/kg of nicotine produced a marked increase in P0.2 and subsequent apnea. With PETCO2 at 60 mm Hg, the time course of P0.2 was qualitatively similar to that observed with PETCO2 at 40 mm Hg, except that the change in P0.2 was larger in the former case than in the latter, for a given nicotine dose. The ratio of the difference in maximal P0.2 observed with PETCO2 of 40 mm Hg and that at 60 mm Hg to the difference between PETCO2 values (delta PO2/delta PETCO2) increased with nicotine dose from 1 to 4 micrograms/kg and, with a further increase in nicotine dose, the maximal delta P0.2/delta PETCO2 plateaued, while delta P0.2/delta PETCO2 obtained from the minimal PO2 values decreased in a nicotine dose-dependent fashion. These results suggest that hypercapnia enhances both stimulative and subsequent depressive ventilatory responses to nicotine.     

经鼻持续性气道正压对阻塞性睡眠呼吸暂停综合征患者呼吸中枢驱动性的影响

为了解经鼻持续性气道正压（ｎＣＰＡＰ）通气治疗对阻塞性睡眠呼吸暂停综合征（ＯＳＡＳ）患者呼吸中枢驱动性的影响，研究了２０例无二氧化碳（ＣＯ＿２）储留的ＯＳＡＳ患者（Ｏ组）及２０例单纯鼾症患者（Ｓ组）夜间睡眠前后呼吸方式及口腔阻断压（Ｐ＿（０．１））的改变，并观察了ｎＣＰＡＰ治疗对ＯＳＡＳ，患者呼吸方式及Ｐ＿（０．１）的影响。结果显示：Ｏ组患者睡前的Ｐ＿（０．１）、呼吸频率、有效吸气阻抗明显高于Ｓ组，潮气量则显著低于Ｓ组。ｎＣＰＡＰ治疗组患者经一夜睡眠后的Ｐ＿（０．１）、每分通气量、潮气量、呼吸频率等较睡前显著增高。经ｎＣＰＡＰ治疗后Ｏ组的呼吸紊乱指数较治疗前明显降低，夜间最低氧饱和度明显提高，Ｐ＿（０．１）较睡前则无明显升高。提示ＯＳＡＳ患者睡前的呼吸中枢驱动性高于单纯鼾症患者，其呼吸形式为浅快呼吸；经过一夜睡眠后，其呼吸中枢驱动水平较睡前明显增高，呼吸形式更为浅快；ｎＣＰＡＰ治疗可以有效地解除睡眠呼吸暂停及其继发的低氧血症，从而逆转睡眠前后呼吸方式和呼吸中枢驱动性的改变。     

Incomplete arousal processes in infants who were victims of sudden death

Infants who became victims of sudden infant death syndrome (SIDS) aroused less from sleep than control infants. This study was conducted to determine the characteristics of arousal from sleep of infants who eventually died of SIDS. Sixteen infants were monitored some days or weeks before they died of SIDS. Their polygraphic sleep recordings were compared with those of matched control infants. Arousals were scored as subcortical activation (incomplete arousals) or cortical arousal (complete arousals). Cortical arousals were significantly less frequent in the victims who would succumb to SIDS in the future than in the control infants during both REM and non-REM sleep (p = 0.039). The frequency (p = 0.017) and duration (p = 0.005) of subcortical activation were significantly greater in the infants who died of SIDS than in the control infants during REM sleep. Compared with the control infants, the infants who later died of SIDS had more frequent subcortical activation in the first part of the night, between 9:00 P.M. and 12:00 A.M. (p = 0.038), and fewer cortical arousals during the latter part of the night, between 3:00 and 6:00 A.M. (p = 0.011). The present data are suggestive of incomplete arousal processes in infants who eventually died at a time they were presumed to have been asleep.     

Respiratory pauses during sleep in near-miss sudden infant death syndrome

To study transient ventilatory changes in infants with the near-miss sudden infant death syndrome (SIDS), we examined the distribution, frequency, and mean duration of all respiratory pauses defined as expiratory time (Te) greater than 2 s in 12 infants with near-miss SIDS and 10 age-matched normal infants during REM and quiet sleep at 1, 2, 3, and 4 months of age. Using the barometric method, we monitored ventilation and respiratory timing while these infants breathed (1) ambient gas concentrations and (2) 2% CO2. We found that infants with near-miss SIDS did not have more frequent or prolonged respiratory pauses than did normal infants at any age in either REM or quiet sleep breathing ambient gas. With 2% CO2, respiratory pauses decreased in number or were eliminated and their mean duration was shorter in both groups. If these infants have hypoxemia during sleep, these data do not support the hypothesis that hypoxemia is secondary to prolonged and more frequent respiratory pauses.     

Role of hypoxic drive in regulation of postapneic ventilation during sleep in patients with obstructive sleep apnea

To elucidate the role of chemoresponsiveness in determining postapneic ventilation in sleep-disordered periodic breathing, we measured ventilatory response associated with apnea-induced arterial oxygen desaturation during sleep and compared it with the awake hypoxic ventilatory response (HVR) in 12 male patients with obstructive sleep apnea (OSA). Awake HVR was measured at a slight hypocapnic level (end-tidal PCO2 = 37 +/- 1 mm Hg, mean +/- SEM), and separately at a PCO2 of 45 mm Hg. During non-REM sleep both the ventilatory rate (VE) and the average respiratory frequency (f) in the ventilatory phase between apneic episodes were inversely correlated with the nadir of arterial oxygen saturation (nSaO2) produced by the preceding apneic phase in all patients (VE versus nSaO2; r = -0.74 +/- 0.03, mean +/- SEM; f versus nSaO2, r = -0.56 +/- 0.04). The average tidal volume (VT) also was correlated with nSaO2 in 10 of the patients (r = -0.56 +/- 0.05). During REM sleep VE was correlated with nSaO2 in 11 patients (r = -0.75 +/- 0.03, p less than 0.02). The response of VE to nSaO2 (delta VE/delta nSaO2) varied widely among the patients (non-REM, 0.52 to 2.16; REM, 0.29 to 1.44 L/min/%) and was significantly lower during REM than non-REM sleep (p less than 0.01). The value of delta VE/delta nSaO2 during both non-REM and REM sleep was correlated with awake HVR at an end-tidal PCO2 of 45 mm Hg (non-REM, r = 0.83, p less than 0.02; REM, r = 0.76, p less than 0.05) but not with that at the hypocapnic level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Obstructive apnea,associated patterns of movement,heart rate,and oxygenation in infants at low and increased risk for SIDS

Repetitive polysomnograms were recorded between 40 weeks post-conceptional age and 6 months in a total of 49 infants, 19 healthy preterm infants, 14 normal term infants, and 16 subsequent siblings of infants who died of sudden infant death syndrome (SIDS). These nighttime recordings lasted 2–4 hours, except at 3 months when an overnight 12–hour recording was perfomed. Obstructive apneas (OA) > 3 seconds were divided into 3 categories: 1) clear obstructive, 2) mixed and 3) unclear because of movement artifacts. More than half belonged in category 3 and were excluded from further analysis unless accompanied by a transient episode of bradycardia (TEB), defined as heart rate ≤100 beats per minute. Each OA with TEB was also examined for changes in transcutaneous oxygen tension (Ptc_O2). Most pauses were brief (median, 4 seconds), the longest (27 seconds) seen only once in the youngest premature infant. The majority of OA were accompanied by heart rate accelerations. The number of clear obstructive and mixed apneas was similar. The scores were combined to calculate a density (number per 100 minutes of recording). OA were not common: Their density decreased from 2 in 100 minutes at 40 weeks in the preterm to once every 300 minutes (5 hours) in the 6-month-old term infant. Ten percent of the OA were accompanied by TEB. Of these, 10% were accompanied by a Ptc₀₂ decrease of >10 mm Hg. OA with TEB followed a nonmonotonic curve, the highest percentage of infants showing this pattern at the age of highest risk for SIDS. Minor differences among study groups were confined to less movements with OA in subsequent siblings and an earlier peak incidence of OA with TEB in prematures, compared to normal term infants. OA were seen in all study groups, were self-limited, and apparently were devoid of pathological consequences. © 1993 Wiley-Liss, Inc.     

Apnea and periodic breathing in healthy full-term infants, 12-18 months of age.

Many children older than 12 months of age are now on home monitors. Home pneumograms performed on normal infants have established standards, and have been used to evaluate infants during their first year. However, no standards have been described for infants older than 12 months. We, therefore, recorded the standard pneumogram on 88 full-term healthy infants who were 12-18 months of age. We analyzed the recordings for average respiratory and heart rates, apnea (greater than or equal to 6 seconds) density, longest apnea, periodic breathing, and bradycardia for 12 hours. We compared the values in males vs. females and in infants 12-14.9 months vs. 15.0-18.0 months of age. Since there was no difference in any parameter measured in any group, we combined the values to determine the normal values for this population.