scholarly journals Postnatal maturation of laryngeal chemoreflexes in the preterm lamb

2007 ◽  
Vol 102 (4) ◽  
pp. 1429-1438 ◽  
Author(s):  
Marie St-Hilaire ◽  
Nathalie Samson ◽  
Elise Nsegbe ◽  
Charles Duvareille ◽  
François Moreau-Bussière ◽  
...  
Keyword(s):  
Heart Rate ◽  
Lower Airway ◽  
Distilled Water ◽  
Active Sleep ◽  
Sleep State ◽  
Quiet Sleep ◽  
General Belief ◽  
Postnatal Maturation ◽  
Laryngeal Mucosa ◽  
Life Threatening

Laryngeal chemoreflexes (LCR) are triggered by the contact of liquids with the laryngeal mucosa. In the mature organism, LCR trigger lower airway protective responses (coughing, effective swallowing, and arousal) to prevent aspiration. General belief holds that LCR are responsible for apnea and bradycardia in the newborn mammal, including humans. Our laboratory has recently shown that LCR in full-term lambs are consistently analogous to the mature LCR reported in adult mammals, without significant apneas and bradycardias (St-Hilaire M, Nsegbe E, Gagnon-Gervais K, Samson N, Moreau-Bussiere F, Fortier PH, and Praud J-P. J Appl Physiol 98: 2197–2203, 2005). The aim of the present study was to assess LCR in nonsedated, newborn preterm lambs born at 132 days of gestation (term = 147 days). The preterm lambs were instrumented for recording glottal adductor electromyogram, electroencephalogram, eye movements, heart rate, respiration, and oximetry. A chronic supraglottal catheter was used for injecting 0.5 ml of saline, distilled water, and HCl (pH 2) during quiet sleep, active sleep, and wakefulness on postnatal days 7 (D7) and 14 (D14). Laryngeal stimulation by water or HCl on D7 induced significant apneas, bradycardia, and desaturation, which, at times, appeared potentially life-threatening. No significant apneas, bradycardias, or desaturation were observed on D14. No consistent effects of sleep state could be shown in the present study. In conclusion, laryngeal stimulation by liquids triggers potentially dangerous LCR in preterm lambs on D7, but not on D14. It is proposed that maturation of the LCR between D7 and D14 is partly involved in the disappearance of apneas/bradycardias of prematurity with postnatal age.

Laryngeal chemoreflexes induced by acid, water, and saline in nonsedated newborn lambs during quiet sleep

2005 ◽  
Vol 98 (6) ◽  
pp. 2197-2203 ◽  
Author(s):  
Marie St-Hilaire ◽  
Élise Nsegbe ◽  
Karine Gagnon-Gervais ◽  
Nathalie Samson ◽  
François Moreau-Bussière ◽  
...  
Keyword(s):  
Heart Rate ◽  
Random Order ◽  
Systemic Arterial Pressure ◽  
Full Term ◽  
Lower Airway ◽  
Distilled Water ◽  
Acid Solutions ◽  
Quiet Sleep ◽  
Laryngeal Mucosa ◽  
Life Threatening

Laryngeal chemoreflexes (LCR) are triggered by the contact of assorted liquids with the laryngeal mucosa. In the neonatal period, the immature LCR consist primarily of apnea and bradycardia, which at times can be life threatening. The aim of this study was to assess LCR induction in nonsedated, newborn full-term lambs by several acid solutions, compared with distilled water and saline. Twelve lambs were instrumented for recording of glottal adductor and diaphragm EMG, EEG, eye movements, heart rate, systemic arterial pressure, and respiratory movements. LCR were induced during quiet sleep by the injection (0.5 ml) of saline, distilled water or two acid solutions (HCl and citric acid, pH 2, diluted in either water or saline). A chronic supraglottal catheter was used to inject the solutions in a random order. Distilled water and acid solutions did not induce any significant decrease in heart rate or respiratory rate. However, significant lower airway protective responses (swallowing, cough, and arousal) were observed after distilled water and especially acid solution administration. In conclusion, LCR in full-term lambs, particularly with acid solutions, are merely characterized by lower airway protective responses resembling mature LCR reported in adult mammals.

Linear and nonlinear properties of heart rate control in infants at risk

1997 ◽  
Vol 273 (2) ◽  
pp. R540-R547
Author(s):  
A. Patzak ◽  
B. Schluter ◽  
W. Orlow ◽  
R. Mrowka ◽  
D. Gerhardt ◽  
...  
Keyword(s):  
At Risk ◽  
Heart Rate ◽  
Chaotic Behavior ◽  
Total Power ◽  
Largest Lyapunov Exponent ◽  
Active Sleep ◽  
Sleep State ◽  
Quiet Sleep ◽  
Spectral Parameters ◽  
Nonlinear Properties

The aim of this study was to test whether the heart rate (HR) control in infants at risk differs in comparison with healthy infants. Twelve former preterm infants suffering from bronchopulmonary dysplasia and 18 control infants, matched for their postconceptional age, were examined polygraphically during quiet and active sleep. HR, low-frequency (LF) power, high-frequency (HF) power, total power, and the ratio of LF to HF power (LF/HF) of the instantaneous HR spectra were calculated for linear analysis. The largest Lyapunov exponent (LLE) of the R-R interval time series was calculated to determine a nonlinear property of HR. Infants at risk had significantly lower LF power (median: 0.51 x 10(-3) vs. 1.16 x 10(-3) Hz2) and lower LF/HF (median: 1.05 vs. 1.94) during quiet sleep. LLE was positive, revealing low-dimensional chaotic behavior of HR control, and did not differ between both groups (median: quiet sleep, 0.05 bit/s vs. 0.06 bit/s; active sleep, 0.16 bit/s vs. 0.15 bit/s). Sleep state-related changes in spectral parameters and LLE were similar in both groups. In infants at risk, the lower LF/HF during quiet sleep can be interpreted in terms of changes in the rhythmic components of the sympathovagal balance of the autonomic system, which is an expression of linear properties of HR control. Conversely, the lack of differences in LLE between both groups indicates similar nonlinear properties of the control system.

Periodic Apnea in the Full-Term Infant: Individual Consistency, Sex Differences, and State Specificity

PEDIATRICS ◽  
1982 ◽  
Vol 70 (1) ◽  
pp. 79-86
Author(s):  
Stephen P. Waite ◽  
Evelyn B. Thoman
Keyword(s):  
Periodic Breathing ◽  
Term Infant ◽  
Full Term ◽  
Respiratory Pattern ◽  
Active Sleep ◽  
Sleep State ◽  
Quiet Sleep ◽  
Term Infants ◽  
The Mean ◽  
Individual Consistency

The occurrence of periodic apnea (apnea during periodic breathing) was studied in 27 normal, full-term infants during the first five weeks of life. The rate and mean length of apnea were analyzed both with respect to sleep state and with respect to respiratory pattern, ie, periodic vs nonperiodic breathing. The rate of apnea was found to vary according to sleep state and the pattern of breathing. The highest apnea rates were non-periodic apneas in active sleep. Periodic apnea rates were relatively low in both active and quiet sleep; however, this type of apnea was consistently observed from weeks 2 through 5. The proportion of apneas that are periodic is much higher in quiet sleep than in active sleep. Rates of periodic and nonperiodic apnea were more consistently correlated in active sleep than in quiet sleep. The mean length of periodic apnea was found to be significantly greater than the mean length of nonperiodic apnea in both sleep states, a difference that reflected a greater positive skew in the distribution of the nonperiodic apnea lengths. This variation in length between periodic and nonperiodic apnea explains, in part, the increased mean length in quiet sleep compared with active sleep. There were significant individual differences over weeks in both forms of apnea in active sleep and in quiet sleep. Female infants were observed to have higher rates of nonperiodic apnea than male infants in active sleep, although no significant differences in the distribution of lengths were obtained.

Development of autonomic heart rate control in the kitten during sleep

1980 ◽  
Vol 238 (6) ◽  
pp. H829-H835
Author(s):  
J. R. Egbert ◽  
P. G. Katona
Keyword(s):  
Heart Rate ◽  
Rate Control ◽  
Intrinsic Rate ◽  
Blocking Agent ◽  
Heart Rate Change ◽  
Heart Rate Control ◽  
Active Sleep ◽  
Quiet Sleep ◽  
Human Infants ◽  
Sympathetic Control

Development of cardiac rate control was studied in 34 kittens aged 4 days to 6 wk during quiet and active sleep, using atropine and propranolol to quantitatively assess the degree of tonic parasympathetic and sympathetic control, with the analysis based on the Rosenblueth and Simeone model. The order of blocking agent administration did not significantly affect the results if a correction was made for the baroreceptor-mediated heart rate change after the blockade of a single autonomic branch. During the first 4 wk, the heart rate in quiet sleep was lower than in active sleep due to a significantly higher parasympathetic tone. The heart rate decreased with age in both sleep states: the decrease in quiet sleep was accompanied by a transition from sympathetic to parasympathetic dominance. The intrinsic rate of the pharmacologically denervated heart was maximum at about 2 wk and decreased steadily thereafter. The observed changes may help explain some features of the development in heart rate previously reported for sleeping human infants.

Ventilatory responses of newborn calves to progressive hypoxia in quiet and active sleep

1980 ◽  
Vol 48 (5) ◽  
pp. 892-895 ◽  
Author(s):  
H. E. Jeffery ◽  
D. J. Read
Keyword(s):  
Ventilatory Response ◽  
Active Sleep ◽  
Sleep State ◽  
Quiet Sleep ◽  
Ventilatory Responses ◽  
Progressive Hypoxia ◽  
Newborn Calves ◽  
End Tidal ◽  
Arterial O2 Saturation ◽  
And Behavior

Isocapnic progressive hypoxia was produced by rebreathing 8-10% oxygen in replicate tests during quiet and active sleep, in five full-term calves aged 1-8 days. Airflow through a tightly fitting mask was digitized at 50-ms intervals to calculate breath-by-breath ventilation and rate. Using a cuvette oximeter, arterial O2 saturation (SaO2) was recorded continuously. A mass-spectrometer record of end-tidal PO2 and PCO2 confirmed the mask seal and the constancy of PCO2. Sleep state was characterized by EEG, EOG, neck EMG, and behavior. In quiet sleep the ratio of ventilation to its normoxic control (VR) increased linearly as SaO2 fell; reflex arousal occurred at SaO2 84.9 ± 4.3% (SD) with VR 1.4 ± 0.39 (SD). In contrast, during active sleep, hypoxemia progressed without any ventilatory response to a very low SaO2; a reflex arousal occurred at SaO2 59.2 ±11.0%, often with a ventilatory response developing abruptly just prior to arousal. The slope of the VR/SaO2 regression lines for the overlapping range of SaO2 differed significantly with state in each animal (P < 0.001); the pooled VR values at SaO2 75% were 1.73± 0.15 (SD) and 0.91 ± 0.18 for quiet and active sleep respectively. The depression of the ventilatory response to hypoxia in active sleep differs from previous reports on adult dogs. The basis for this difference needs to be evaluated in relation to species and age, in particular in relation to both the mechanics of breathing and to chemoreceptor reflexes.

Age-dependent vulnerability to carotid chemodenervation in piglets

1996 ◽  
Vol 80 (1) ◽  
pp. 323-331 ◽  
Author(s):  
A. Cote ◽  
H. Porras ◽  
B. Meehan
Keyword(s):  
Continuous Monitoring ◽  
Fiber Optic ◽  
The Other ◽  
Active Sleep ◽  
Severe Hypoxemia ◽  
Quiet Sleep ◽  
Carotid Bodies ◽  
Age Dependent ◽  
Life Threatening ◽  
Arterial O2 Saturation

We sought to determine the age of greatest vulnerability in piglets to the loss of carotid chemoreceptor function. We studied four groups of carotid body-denervated (CBD) piglets whose carotid bodies were surgically removed at 4-5, 9-10, 12-15, and 21-22 days and who are herein referred to, respectively, as the CBD5, CBD10, CBD15, and CBD20 groups. Four intact groups, at corresponding ages, underwent a sham surgical procedure. After a postsurgery recovery of at least 7 days, we studied all animals to detect the presence of apnea and the consequences of it, if any. Two days before the experiments, we implanted in all animals a fiber-optic arterial catheter for continuous monitoring of arterial O2 saturation, and electroencephalographic electrodes for the recording of sleep states. During quiet sleep in the CBD15 group, we found numerous prolonged central apneic events accompanied by a profound desaturation, tachycardia, a rise in blood pressure, and, eventually, a flattening of the electroencephalogram. No prolonged apneic events occurred, however, in the other CBD groups nor in the intact animals. During active sleep, no prolonged apneic events occurred at all. We thus conclude that, in piglets, the absence of normally functioning carotid chemoreceptors at approximately 2 wk of age can lead to life-threatening apneic events with severe hypoxemia, events that are state specific.

scholarly journals Cerebral Circulation in Sleep: Vasodilatory Response to Cerebral Hypotension

1998 ◽  
Vol 18 (6) ◽  
pp. 639-645 ◽  
Author(s):  
Daniel A. Grant ◽  
Carlo Franzini ◽  
Jennene Wild ◽  
Adrian M. Walker
Keyword(s):  
Cerebral Circulation ◽  
Perfusion Pressure ◽  
Superior Sagittal Sinus ◽  
Active Sleep ◽  
Sleep State ◽  
Quiet Sleep ◽  
Flow Probe ◽  
Sagittal Sinus ◽  
Cerebral Vasodilation ◽  
Cerebral Vascular Resistance

Little is known of the factors that regulate CBF in sleep. We therefore studied 10 lambs to assess the vasodilatory processes that underlie cerebral autoregulation during sleep. Lambs, instrumented to measure CBF (flow probe on the superior sagittal sinus), sleep state, and cerebral perfusion pressure (CPP), were rapidly made hypotensive by inflating a cuff around the brachiocephalic artery to reduce CPP to 30 mm Hg in each state. During control periods, cerebral vascular resistance (CVR in mm Hg/mL/min) was lower in active sleep (2.8±0.3, mean±SD, P ≤ 0.001) than in wakefulness (3.9±0.6) and quiet sleep (4.3±0.6). The CVR decreased promptly in each state as CPP was lowered. The time (seconds) required for maximal cerebral vasodilation to occur was longer in active sleep (35±11) than in quiet sleep (20±6, P ≤ 0.001) and wakefulness (27±11, P ≤ 0.05). The CVR decreased less in active sleep (0.6±0.3, P ≤ 0.001) than in quiet sleep (1.5±0.3), although the changes in CPP induced with brachiocephalic occlusion were equal in each state. In conclusion, our studies provide the first evidence that the vasoactive mechanisms that underlie autoregulation of the cerebral circulation function during sleep. Moreover, our data reveal that the speed and the magnitude of the vasodilatory reserves available for autoregulation are significantly less in active sleep than in quiet sleep.

Influence of sleep and myometrial activity on systemic and uteroplacental hemodynamics in pregnant ewes

1995 ◽  
Vol 268 (4) ◽  
pp. H1734-H1739
Author(s):  
J. E. Fewell
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Uterine Artery ◽  
Systemic Arterial Pressure ◽  
Uterine Horn ◽  
Artery Blood Flow ◽  
Active Sleep ◽  
Quiet Sleep ◽  
Quiet Wakefulness ◽  
Uteroplacental Blood Flow

Little is known about the influence of sleep on systemic and uteroplacental hemodynamics during pregnancy. Experiments were therefore carried out on six chronically instrumented pregnant ewes (125–133 days of gestation) to investigate the influence of sleep on systemic and uteroplacental hemodynamics. Because nonlabor myometrial activity influences uteroplacental hemodynamics, we made measurements during quiet wakefulness, quiet sleep, and active sleep in the presence and absence of myometrial activity. Cardiac output, heart rate, and systemic arterial pressure were decreased in active sleep compared with quiet wakefulness; these variables were not significantly altered by myometrial activity. The interaction between sleep and myometrial activity was such that the lowest values of uteroplacental blood flow, as estimated from middle uterine artery blood flow to the pregnant uterine horn and, hence, uteroplacental oxygen delivery occurred during active sleep in the presence of myometrial activity (i.e., decreased approximately 19% compared with quiet wakefulness and the absence of myometrial activity). Further investigation is required to determine the possible fetal consequences of a reduced uteroplacental perfusion in the presence of myometrial activity during sleep.

Nonlinear dynamics of heart rate variability in cocaine-exposed neonates during sleep

2001 ◽  
Vol 280 (6) ◽  
pp. H2920-H2928 ◽  
Author(s):  
Smita Garde ◽  
Michael G. Regalado ◽  
Vicki L. Schechtman ◽  
Michael C. K. Khoo
Keyword(s):  
Nonlinear Dynamics ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Correlation Dimension ◽  
Spectral Power ◽  
Approximate Entropy ◽  
Parametric Model ◽  
Linear Component ◽  
Active Sleep ◽  
Quiet Sleep

The aim of this study was to determine the effects of prenatal cocaine exposure (PCE) on the dynamics of heart rate variability in full-term neonates during sleep. R-R interval (RRI) time series from 9 infants with PCE and 12 controls during periods of stable quiet sleep and active sleep were analyzed using autoregressive modeling and nonlinear dynamics. There were no differences between the two groups in spectral power distribution, approximate entropy, correlation dimension, and nonlinear predictability. However, application of surrogate data analysis to these measures revealed a significant degree of nonlinear RRI dynamics in all subjects. A parametric model, consisting of a nonlinear delayed-feedback system with stochastic noise as the perturbing input, was employed to estimate the relative contributions of linear and nonlinear deterministic dynamics in the data. Both infant groups showed similar proportional contributions in linear, nonlinear, and stochastic dynamics. However, approximate entropy, correlation dimension, and nonlinear prediction error were all decreased in active versus quiet sleep; in addition, the parametric model revealed a doubling of the linear component and a halving of the nonlinear contribution to overall heart rate variability. Spectral analysis indicated a shift in relative power toward lower frequencies. We conclude that 1) RRI dynamics in infants with PCE and normal controls are similar; and 2) in both groups, sympathetic dominance during active sleep produces primarily periodic low-frequency oscillations in RRI, whereas in quiet sleep vagal modulation leads to RRI fluctuations that are broadband and dynamically more complex.

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