Respiration In Infants Research Articles

Comparisons of new nonlinear modeling techniques with applications to infant respiration

This paper concerns the application of new nonlinear time-series modeling methods to recordings of infant respiratory patterns. The techniques used combine the concept of minimum description length modeling with radial basis models. Our first application of the methods produced results that were not entirely satisfactory, particularly with respect to accurately modeling long term quantitative and qualitative features of respiration patterns. This paper describes a number of modifications of the original methods and makes a comparison of the improvements the various modifications gave. The modifications made were increasing the class of basis function, broadening the range of possible embedding strategies, improving the optimization of the likelihood of the model parameters and calculating a closer approximation to description length. The criteria used in the comparisons were description length, root-mean-square prediction error, model size, free-run behavior and amplitude size and variation. We use surrogate data analysis to confirm the hypothesis that the recorded data are consistent with the nonlinear models we construct, and not consistent with simpler models. We also investigate the free-run dynamics of the model systems to see if the models exhibit features consistent with physiological characteristics observed independently in the respiratory recording. This involved modeling breathing patterns prior to a sigh and onset of a phenomenon called “periodic breathing”; and comparing the period of “cyclic amplitude modulation” of the free-run dynamics of the models and the period of the subsequent periodic breathing observed in respiration recording. The periods were consistent in six out of seven recordings.

Maternal proximity and infant CO2 environment during bedsharing and possible implications for SIDS research.

Sudden infant death syndrome (SIDS) is the leading cause of human infant mortality after the neonatal period in Western countries. Recently, child care practices have been shown to be important in determining infant vulnerability to SIDS. However, very little is known about the impact of parent-infant cosleeping on infant sleep physiology and behavior and SIDS risk. This reflects the failure of Western societal research paradigms to appreciate the human infant's evolutionary history of cosleeping, the recency of the emergence of solitary infant sleeping as a practice and the fact that parent-infant cosleeping is still the preferred sleeping arrangement for the majority of contemporary societies. Incorporating current hypotheses on the mechanisms of SIDS, we have hypothesized that the comparatively sensory-rich cosleeping environment might be protective against SIDS in some contexts. As a first step to characterize cosleeping environments, this investigation is aimed at assessing, in routinely bedsharing mothers and infants, their relative sleeping positions and the potential for sleeping in close face-to face proximity and for infant exposure to increased environmental CO2 produced by maternal respiration. The latter is important in that breathing elevated levels of CO2 can have diverse effects, ranging from respiratory stimulation at low levels to suffocation at very high levels. Two related laboratory studies were performed. In the first, all-night videotapes of 12 healthy, routinely bedsharing mother-infant pairs were analyzed for sleeping positions and time spent in face-to-face orientation and distances separating their faces. Infants were 11-15 wk old. Mothers predominantly positioned themselves on their sides facing their infants, with the infants placed either supine or on their sides. Mothers and infants slept oriented face-to-face for 64 +/- 27% (S.D.) of non-movement time, with distance less than 20 cm commonly separating their faces. In the second study, concentrations of CO2 in air were measured in six young women at distances of up to 21 cm from their nares. Peak expiratory CO2 concentrations remained above 1.0% at distances up to 9 cm and above 0.5% at 18 cm. Both baseline and peak CO2 levels were further increased at all distances when measured within a partial air pocket created to simulate a bedding environment sometimes seen during bedsharing. We conclude that during bedsharing there is potential for 1) a high degree of face-to-face orientation and close proximity and consequently 2) increased environmental CO2, as a result of maternal respiration, to non-lethal levels that might stimulate infant respiration. The close proximity would also maximize the sensory impact of the mother on the infant through other modalities. We also suggest that bedsharing may minimize prone infant positioning, a known risk factor for SIDS.

New techniques for neonatal respiratory support

Considerable progress has been made in the management of respiratory distress in newborns since the introduction of positive pressure ventilation over 20 years ago. More recently, the introduction of surfactant and the increased use of steroids predelivery have led to a major increase iri survival in preterms with hyaline membrane disease. Conventional ventilation refers to the positive pressure respiratory support that is practised in newborn units. A wide variety of mechanical ventilators are currently in use in the UK and ventilator management policies vary widely between units with no consensus view as to the best approach. Trauma from ventilation is an important factor in the aetiology of the airway and lung damage seen in bronchopulmonary dysplasia (BPD). Asynchrony between the ventilator and the infant's respiration and the use of large tidal volumes to accomplish adequate ventilation are the major components of this trauma? In a study limiting tidal volume by constraints applied to the chest wall in an animal model the use of high airway pressures did not produce as much damage as when tidal volume was not limited) Therefore, changes in lung volume may be more important than changes in airway pressure in the production of lung injury. For this reason, the term volutrauma is preferred to barotrauma. In animals with healthy lungs 13 large tidal volume ventilation can damage the pulmonary capillary endothelium, alveolar and airway epithelium and basement membranes allowing fluid, protein and blood to leak into the airways, alveoli and lung interstitium. 1 This sequence is well described in the evolution of respiratory distress syndrome to chronic lung disease in newborns. Despite the excellent achievements in neonatal respiratory care, a number of infants continue to respond

Attractor dynamics in early infant sucking and respiration

Attractor dynamics in early infant sucking and respiration

The safety of a nitric oxide inhalation system using a conventional infant respirator.

Attention is becoming increasingly focused on inhalation of nitric oxide (NO) as a selective pulmonary vasodilator. Its metabolite nitrogen dioxide (NO2), however, is a toxic molecule. The purpose of the present study was to evaluate the safety of a NO inhalation system using a conventional infant respirator from the viewpoint of NO2 production. The NO inhalation system consisted of a standard neonatal ventilator, a neonatal circuit and a test lung. The NO concentration was increased from 0 up to 19 ppm. At each level of NO, the oxygen (O2) concentration was changed from 21 to 100%. The NO and NO2 concentrations were measured with a chemiluminescence analyzer using a molybdenum converter. The NO2 concentration was increased when either the O2 or the NO concentration was increased. The maximum concentration of NO2 was 0.10 +/- 0.02 ppm when the concentrations of NO and O2 were 19 ppm and 100% respectively. The NO inhalation system, using a conventional infant respirator, can be used safely when monitoring NO and NO2 concentrations.

Air-flow sensor and humidity sensor application to neonatal infant respiration monitoring

A study is conducted on a newly designed neonatal infant respiration-monitoring system for detecting the respiratory situation of premature infants. Two kinds of tiny high-quality sensors, a humidity sensor and an air-flow sensor, and an MCS-51 (Intel) single-chip processor are used, which enable both the humidity values to be sensed and displayed quantitatively and the breathing rate monitored with user-settable alarms.

Pitfalls in respiratory monitoring of premature infants during kangaroo care.

The reliability of respiratory monitoring, using either chest or back electrodes, was studied in 13 preterm infants during kangaroo care (infant-parent skin to skin contact). In three out of four infants with chest electrodes both infant and parental respiration were clearly visible on pneumograms. In these infants apnoeic pauses were not registered because parental respiration was recorded as infant breathing. Bradycardia and oxygen saturation were, however, properly registered. In infants with electrodes placed on the back infant respiration was less superimposed by parental breathing. However, even in some of these infants parental respiration was visible in the pneumograms. It is concluded that during kangaroo care the electrodes should be placed on the back and monitoring should always include heart rate and oxygen saturation.

The breathing bear: Effects on respiration in premature infants

The sleep states and the regularity of quiet sleep (QS) respiration were investigated in premature infants who were provided a “breathing” teddy bear. The bear (BrBr) is a source of optional rhythmic stimulation that reflects the breathing rate of the individual infant it is with. At 33 weeks CA, 19 premature infants were given a BrBr and 17 were given a nonbreathing bear (N-BrBr). At 35 weeks CA, and again at 45 weeks CA, a 1–2-h interfeed motility recording was obtained. These analog signals were scored for active sleep, QS, and wakefulness; and each 10-s epoch of QS was judged for regularity of respiration using a four-point rating scale. At 35 weeks, the BrBr babies showed slower and more regular respiration during QS. At 45 weeks, the BrBr babies showed more QS and less active sleep. At both ages, only the BrBr babies showed a correlation between respiration regularity and the amount of QS. The findings suggest facilitation of neurobehavioral development as well as entrainment from optional stimulation, which reflects one of the infant's own biological rhythms.

Ultradian and diurnal cyclicity in the sleep states of newborn infants during the first two postnatal days

Objective: The purpose of this study was to investigate both ultradian and diurnal cyclicity in the sleep states of newborn fullterm infants during the first 2 postnatal days. Methods: The sleep of 31 healthy newborn infants was recorded continuously throughout the first 2 postnatal days, starting immediately after birth, using an automated Motility Monitoring System (MMS). The MMS consists of a pressure sensitive mattress pad connected to an amplifier and a small 24-h analog recorder. A single channel of analog signals produced by the infant's respiration and body movements was recorded and then scored in 30-s epochs for Active Sleep, Quiet Sleep, Active-Quiet Transition, Sleep-Wake Transition, and Wake. Data Analyses: The 48 h of recording were divided into successive 12-h periods from 07:00 h to 19:00 h (day) and 19:00 h to 07:00 h (night), and all measures were derived for each day and night period. Both cross-sectional and repeated measures analyses were used because all babies were not represented in all day/night periods. Results: Day/night differences in state variables: On both days, there was greater Wakefulness, shorter Quiet Sleep Bout Lengths, shorter Mean Sleep Periods and shorter Longest Sleep Periods during the daytime. On day 1 only, there was less Quiet Sleep, shorter Quiet Sleep Bout Lengths and more Sleep-Wake Transition during the daytime. On day 2, repeated measures analyses revealed two additional day/night differences: less Quiet Sleep and more Sleep-Wake Transition during the daytime. Day/night differences in Quiet Sleep cyclicity: 28 sleep periods met the criteria for analysis of Quiet Sleep cyclicity, and only six of these occurred during the daytime. Seventeen of 28 analyzable sleep periods showed significant Quiet Sleep cyclicity. Only two of these occurred during the daytime. Conclusions: Contrary to the prevailing view of developing sleep rhythms, the results of this study suggest that newborn infants exhibit both ultradian ad diurnal cyclicity in their sleep patterns from the earliest postnatal period.

Interactions between thermoregulation and the control of respiration in infants: possible relationship to sudden infant death.

In summary, there is evidence that developmental changes in respiratory control and in thermoregulation have effects upon each other. Theoretically, such effects could give rise to failure of the respiratory system and there is some circumstantial evidence to support the concept that on occasions such interactions may be of importance in sudden unexpected death in infancy. Future research in this area should focus on the nature of the interactions between thermoregulation and respiration, and on the effects of infection and infection-related mediators on those interactions.

Minute ventilation during mask halothane anaesthesia in infants and children.

The pattern of respiration in infants during anaesthesia is not well documented. In this study, minute ventilation (MV) during elective mask halothane anaesthesia (HA) was measured during spontaneous ventilation in infants (Group I) and children (Group II). Airflow was measured with pneumotachography (#0 Fleisch in Group I and #1 Fleisch in Group II). Analogue signals of pressure and flow were recorded on magnetic tape for off-line playback. The flow signal was mathematically integrated to volume. The surgical procedure was divided into three stages: A, B and C representing HA, surgical stimulation and emergence respectively. The pattern of respiration during spontaneous ventilation was described as tidal volume (VTx), respiratory frequency (fx), mean inspiratory flow (VT/TIx), inspiratory duty cycle (TI/TTotx) where the subscript x denoted the stage. Seven infants (2.7 +/- 0.5 mo, 5.8 +/- 0.5 kg) and five children (3.1 +/- 1.1 yr, 15.8 +/- 1.7 kg) were studied. There was no difference in MV between Groups I and II. Halothane anaesthesia in both groups was characterized by rapid shallow breathing: VTA was lower in Group I (2.90 +/- 0.8 ml.kg-1) than in Group II (3.74 +/- 0.40 ml.kg-1) (P < 0.05). Tidal volume was lower during anaesthesia than emergence in both groups (P < 0.05). There was no difference in VT/TIx between groups. The VT/TIA was lower than VT/TIC in Group I (P < 0.05) but not in Group II. There was no intra or intergroup difference in TI/TTot between stages. We suggest that during HA infants have a greater reduction in VT than children, which may predispose infants to hypercarbia during HA.

Learning in premature infants.

This study examined instrumental learning in premature infants by using a teddy bear that «breathed» quietly at a rate that reflected the infant's respiration rate. At 33 weeks conceptional age (CA), 45 infants were provided either a Breathing Bear (BrBr) or a Nonbreathing Bear (N-BrBr). The baby was monitored by time-lapse video for 3-day periods at the beginning and end of a 2-week intervention period. The BrBr babies decreased their latency to contact the bear over time, whereas the N-BrBr babies showed the opposite pattern. For the BrBr babies, decreased contact latencies were correlated with increased total contact and increased contact frequencies. Thus, by 35 weeks CA, premature infants learned to find and make contact with a reinforcing source of stimulation

Alterations in cerebrovascular reactivity after positive pressure ventilation.

Pressure ventilation of the newborn can adversely affect the cardiovascular system. Increasing airway pressure increases cerebral venous pressure, thus stressing brain vasculature. To test the hypothesis that cerebral venous distension caused by mechanical ventilation alters cerebral microvascular responses, we studied cerebrovascular responses before, during, and after positive pressure ventilation. Anesthetized newborn pigs were ventilated with a standard time-cycled, pressure-limited infant respirator. Pial arterioles were measured in response to hypercapnia, topical isoproterenol, and topical norepinephrine during control [mean airway pressure (Paw) = 0.9 +/- 0.05 kPa (4.8 +/- 0.3 cm H2O)] conditions, during 40-60 min of increased Paw [2.5 +/- 0.2 kPa (13.9 +/- 1.3 cm H2O)], and when the Paw was lowered again. Pial arteriolar dilation in response to hypercapnia was not changed by increasing Paw. Similarly, responses to isoproterenol and norepinephrine were unaltered during raised Paw. However, a significant decrease in responses to topical isoproterenol and norepinephrine was observed after increased Paw. These experiments show that specific prostanoid-independent cerebrovascular responses are altered subsequent to pressure ventilation, whereas prostanoid-dependent dilation to hypercapnia was not affected. These changes suggest that the newborn cerebral vasculature is affected by positive pressure ventilation, further raising the possibility that ventilation-induced alterations in microvascular responses could make the brain more vulnerable to added stresses after pressure ventilation.

Salbutamol improves respiration in infants with bronchiolitis

Salbutamol improves respiration in infants with bronchiolitis

Positive-pressure ventilation alters blood-to-brain and blood-to-CSF transport in neonatal pigs

These experiments examine the transfer of sucrose, urea, sodium, and albumin from blood to brain in new-born pigs exposed to an increase in ventilation pressure. We also studied the movement of urea and sodium from blood to cerebrospinal fluid (CSF). By use of a standard time-cycled pressure-limited infant respirator, mean airway pressure (Paw) was increased from approximately 3 to 17 cmH2O. Urea and albumin transfer into the brain were unchanged with increased Paw. Sodium transport decreased significantly in all brain regions, while sucrose transfer was increased in the cerebrum [transfer constant (Kin) = 3.5 +/- 0.04 vs. 9.9 +/- 1.0 cm3.g-1.s-1.10(6)] at the increased Paw. Transport of urea nd sodium from blood to CSF decreased to half of control values with increased Paw. Thus, in newborn pigs, increasing Paw selectively alters blood-to-brain transport. In addition, movement of tracers from blood to CSF was severely restricted, possibly by a decrease in CSF production. It appears likely that the increased cerebral venous pressure causes the observed changes in tracer transport. Such altered blood-to-brain transport could adversely affect neuronal function.

Varying tracheal cross‐sectional area during respiration in infants and children with suspected upper airway obstruction by computed cinetomography scanning

An ultrafast cinetomography computed tomographic scanner (cine-CT) was used to evaluate infants and children (n = 15) with suspected obstruction of the larynx or trachea. One scan sequence provided a single image at each of eight cross-sectional levels (volume-mode study). Each study, lasting 224 ms, covered the distance between the supraglottic area and the carina. Each patient also underwent a "dynamic" study at a specific level of interest determined from the volume-mode study. Forty images within 2.3 s covered at least one respiratory cycle. The images were displayed as a closed-loop movie and dynamic changes in laryngeal and tracheal caliber with respiration were monitored and quantitated. Tracheal boundaries were outlined either by a trackball-guided cursor (freehand) or semi-automated computer edge detection, and cross-sectional areas and diameters were determined. Reproducibility was tested among three investigators' freehand drawings and two automated computer drawings, at the same and at varying image intensities. The coefficient of variation for the computer-assisted records (0.2%) was smaller than for the best freehand drawing (1.5%). Tracheal diameters were reproducible, but with greater intra-individual investigator variability. Four normal tracheas had close to published measurements with conventional CT scanners. Cine-CT gives objective tracheal dimensions and their variation during respiration; it provides good anatomical detail above the carina, and also of the extra- and intra-thoracic vessels if injected with contrast medium.

Effects of rocking on infant respiration

The feasibility and effectiveness of low energy synchronous transcatheter cardioversion of atrial flutter and fibrillation were examined in dogs with talc-induced pericarditis, A conventional electrode catheter was positioned transvenously in the right atrial appendage. Atrial flutter/ fibrillation was induced by using the train pulse method, and the tachyarrhythmia-inducing threshold was determined. The minimal effective cardioversion energy levels were compared in three different cardioversion methods: method A = delivery of shock between the proximal electrode (cathode) and the backplate (anode), method B = delivery between the proximal electrode (cathode) and the distal electrode (anode) and method C = conventional external cardioversion.In both methods A and B, all 149 cardioversion attempts were successful with shocks of ≤5 J. Shocks of ≤1 J resulted in successful cardioversion in 57 (70%) of 81 attempts, 50 (74%) of 68 attempts and 5 (12%) of 41 attempts with methods A, B and C, respectively. The mean minimal effective cardioversion energy levels were not significantly different between methods A and B (0.62 ± 0.67 versus 0.58 ± 0.71 J). Transcatheter cardioversion decreased the defibrillation threshold 3- to 75-fold (men 6-to 7-fold) from that of transthoracic cardioversion. The defibrillation threshold was not influenced by the inducibility of atrial flutter/fibrillation. There were no complications of heart block, ventricular fibrillation or pathologic evidence of severe shock-induced atrial injury.Thus, low energy synchronous transcatheter cardioversion of atrial flutter/fibrillation is considered feasible and effective. This technique may also be useful in managing the atrial flutter/fibrillation that can occur during electrophysiologic studies.

Interaction between nonnutritive sucking and respiration in preterm infants.

The effect of nonnutritive sucking bursts (NNSBs) on respiratory frequency was sequentially evaluated in 12 healthy preterm infants. Studies were performed during active sleep in infants between 32 and 37 weeks postconceptional age. The duration of NNSBs was classified as follows: (a) less than 3 s, (b) between 3 and 6 s, and (c) greater than 6 s. NNSBs of each duration were found at all ages, although NNSBs greater than 6 s were the least frequently observed. Respiratory rate increased significantly during NNSBs of less than 3 s, and also in those of 3-6 s duration. There was no significant effect on respiratory frequency of sucking bursts longer than 6 s. Our results document an early interaction between these two motor rhythms, which is influenced by the length of the NNSB. Moreover, they indicate that the decrease in respiratory frequency reported in a similar group of preterm infants during feeding should not be interpreted as an effect of sucking per se.

1485 MATURATION OF RESPIRATORY PATTERNS IN VERY LOW BIRTH WEIGHT (VLBW) INFANTS: INFLUENCE OF POSTCONCEPTIONAL AGE (PCA)

Periodic breathing (PB) and prolonged sleep apnea (>15 sec) (PSA) often are present in VLBW infants, may be secondary to CNS immaturity and can result in serious complications. Early reports show th incidence of PB peaks during the second and third week of life; our observations indicate a different pattern in VLBW infants. Ten VLBW infants (BW=1130±0.21 gms, GA=29.9±1.4 wks) were studied weekly from birth. A total of 70 pneumograms (each > 300 min. sleep) were analyzed for % PB, PSA, and bradycardia (B) (<80 BPM). All infants were off mechanical aminophyllin (A) for a mean of 5.9±2.2 wks, but only 4 were on A in the first wk of life. No attempt was made to control A administration since the study was not designed to dictate clinical care. Percent PB, PSA, and B were assessed in relation to postnatal age (PNA), and PCA. Significant PB (>5%) increases with PNA, but does not occur prior to 33 wks PCA. In contrast to PB, B and PSA episodes decrease with PNA and PCA. Increased PB occurs in VLBW infants despite A and was present only after 32 wks PCA. This finding, requiring further evaluation, may be important to understanding maturation of respiration in VLBW infants.

1841 DEGREE OF PERIODIC BREATHING PER GESTATIONAL AGE: IS THERE A CORRELATION?

Periodic breathing is a common pattern of respiration in premature infants. Home cardiorespiratory monitoring of premature infants with periodic breathing has been advocated to detect and prevent associated episodes of prolonged apnea. Since periodic breathing is thought to be related to maturity of the respiratory control center one might expect that percent of periodic breathing would decrease with increasing gestational age. The purpose of this study was to define the mean percent of periodic breathing per gestational age in premature infants. Pneumograms from 153 premature infants were reviewed. Infants were studied for suspected clincal apnea and/or bradycardia. All infants were studied prior to starting theophylline. Percent periodicity of breathing was obtained from the tracings by calculating the time of periodic breathing/sleep time. Periodic breathing was defined as three or more apneic pauses of greater than 3 seconds but less than 10 seconds within periods of normal respiration of 20 seconds or less. The above data indicate that there is no correlation with gestational age, specifically there is no trend of decreasing periodicity with increasing gestational age. We conclude that gestational age in preterm infants is not predictive of the percentage of periodic breathing.