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Heart rate variability can be entrained by repetitive thermal stimulation in the preterm neonate
Abstracts / Early Human Development 45 (1996) 133-165
143
rate and blocked the effect of rolipram in lungs from sheep aged 0 - 1 4 days confirming that the cyclic nucleotide-mediated component of L L absorption at this age was mediated by c A M P which was produced as a result of [3-adrenergic stimulation. In lungs from sheep aged 6 - 1 2 weeks, sotalol did not reduce the resting LL absorption rate, and rolipram given after sotalol significantly increased absorption rate. This confirmed that the cyclic nucleotide-mediated component of LL absorption in juvenile postnatal lungs was mediated by c A M P from sources other than j3adrenergic stimulation. Age 0-14 6-12 0-14 6-12
days weeks days weeks
Control
Sotalol (100 ixM)
Rolipram (10 ttM)
1.99 1.21 3.39 -1.27
Not done Not done -2.18 _+ 0.37 (4)* -1.29 _+ 0.24 (4)
3.18 3.45 -1.94 -2.02
± 0.16 (4) _+ 0.41 (4) +_ 0.82 (4) _+ 0.14 (4)
+ ± + ±
0.51 (4)* 0.33 (4)* 0.52 (4) 0.64 (4)*
Values are mean Jv -+ S.E.M. in m l - h ~ (kg body wt.)-~; number of experiments in parentheses; *P < 0.05, comparison of paired regression lines by t-test; negative values denote liquid absorption from the lung lumen. This work was supported by the Medical Research Council and the Wellcome Trust. Rolipram was a gift from Schering A G (Germany).
Reference [1] Ramsden, C.A., Markiewicz, M., Walters, D3/., Gabella, G., Parker, K.A.. Barker, RM. and Neil, H.L. (1992): J. Physiol., 448, 579-597. 12] Stephens, R.H., Benjamin, A.R. and Walters, D.V. (1993): J. Physiol., 459, 333R [3] Stephens, R.H., Benjamin, A.R. and Waiters, D.V. (1993): J. Physiol., 467, 341E [41 Stephens, R.H.. Benjamin, A.R. and Walters, D.V. (1995): J. Physiol., in press.
Heart rate variability can be entrained by repetitive thermal stimulation in the preterm neonate EA. Mannix a, K. Costeloe a, D. Inwald a, M.K.S. Hathorn b "Academic Department of Child Health, The Medical College of St. Bartholomew's Hospital and The London Hospital Medical College, London, ~'Department of Physiology, Queen Mary and Westfield College, London, UK. The beat-to-beat change in heart rate, governed by the opposing actions of the parasympathetic and sympathetic nervous systems - - the heart rate variability (HRV), has long been recognised. Spectral analysis of instantaneous heart rates produces three dominant bands of power. A high frequency band (0.4-0.7 Hz) due to the effects of breathing - - respiratory sinus arrhythmia (RSA), and two low frequency bands (0.03-0.17 Hz) due to thermoregulator and baroreceptor activity.
144
Abstracts / Early Human Development 45 (1996) 133-165
We have previously shown that heart rate variability in the term infant can be entrained by a repetitive thermal stimulus over a frequency range of 0.05-0.15 Hz [1 ]. It has been argued that this phenomenon can be used as an index of autonomic nervous system maturity. This study examines entrainment of heart rate variability in preterm babies. Heart rate and breathing were recorded during quiet sleep, before and during periodic thermal stimulation. Data are presented from 20 sequentially studied appropriately grown preterm babies with a mean gestational age of 31 weeks (29-36). Studies were performed within the first 2 weeks of life, after a feed in a controlled environmental temperature of 26-28°C. These babies were studied with a periodic thermal stimulus at 0.05, 0.10 and 0.15 Hz and spectral analysis was performed on 120-s sections of stable data. Power was measured over several frequency bands: (i) the range of breathing frequencies (RSA) [2]; (ii) the frequency of stimulation; (iii) the low frequency region (0.03-0,17 Hz). During thermal stimulation, there is a local peak of power at the frequency of stimulation for all frequencies, and there is a highly significant increase in power at the frequency of stimulation in comparison to the total increase in low frequency power (P < 0.001). These results support the evidence that preterm babies have functional vasomotor control [3] but we would suggest that they show entrainment to a repetitive thermal stimulus over as wide a range as the appropriately grown term babies and over a wider range of frequencies than has been previously reported [3]. This work was supported by the Joint Research Board, St. Bartholomew's Hospital and the Wellcome Trust.
References [1] C(~steloc. K. ct al. (1994): Early Hum. Dev., 39, 141. [2] Hathorn, M.K.S. (1989): Early Hum. Dev.. 20, 81-99. [3] Lindqvist. A. et al. (1982): Early Hum. Dev., 8, 37-47.
The significance of PEEP C.J. Morley, J.S. Ahluwalia Department of Paediatrics, University of Cambridge, Cambridge, UK, This study investigated the influence of age, peak pressure and F~o 2 on the effect of different levels of PEEP on blood gases and blood pressure.
Methods: After obtaining parental consent, infants ventilated for RDS were studied at
143
rate and blocked the effect of rolipram in lungs from sheep aged 0 - 1 4 days confirming that the cyclic nucleotide-mediated component of L L absorption at this age was mediated by c A M P which was produced as a result of [3-adrenergic stimulation. In lungs from sheep aged 6 - 1 2 weeks, sotalol did not reduce the resting LL absorption rate, and rolipram given after sotalol significantly increased absorption rate. This confirmed that the cyclic nucleotide-mediated component of LL absorption in juvenile postnatal lungs was mediated by c A M P from sources other than j3adrenergic stimulation. Age 0-14 6-12 0-14 6-12
days weeks days weeks
Control
Sotalol (100 ixM)
Rolipram (10 ttM)
1.99 1.21 3.39 -1.27
Not done Not done -2.18 _+ 0.37 (4)* -1.29 _+ 0.24 (4)
3.18 3.45 -1.94 -2.02
± 0.16 (4) _+ 0.41 (4) +_ 0.82 (4) _+ 0.14 (4)
+ ± + ±
0.51 (4)* 0.33 (4)* 0.52 (4) 0.64 (4)*
Values are mean Jv -+ S.E.M. in m l - h ~ (kg body wt.)-~; number of experiments in parentheses; *P < 0.05, comparison of paired regression lines by t-test; negative values denote liquid absorption from the lung lumen. This work was supported by the Medical Research Council and the Wellcome Trust. Rolipram was a gift from Schering A G (Germany).
Reference [1] Ramsden, C.A., Markiewicz, M., Walters, D3/., Gabella, G., Parker, K.A.. Barker, RM. and Neil, H.L. (1992): J. Physiol., 448, 579-597. 12] Stephens, R.H., Benjamin, A.R. and Walters, D.V. (1993): J. Physiol., 459, 333R [3] Stephens, R.H., Benjamin, A.R. and Waiters, D.V. (1993): J. Physiol., 467, 341E [41 Stephens, R.H.. Benjamin, A.R. and Walters, D.V. (1995): J. Physiol., in press.
Heart rate variability can be entrained by repetitive thermal stimulation in the preterm neonate EA. Mannix a, K. Costeloe a, D. Inwald a, M.K.S. Hathorn b "Academic Department of Child Health, The Medical College of St. Bartholomew's Hospital and The London Hospital Medical College, London, ~'Department of Physiology, Queen Mary and Westfield College, London, UK. The beat-to-beat change in heart rate, governed by the opposing actions of the parasympathetic and sympathetic nervous systems - - the heart rate variability (HRV), has long been recognised. Spectral analysis of instantaneous heart rates produces three dominant bands of power. A high frequency band (0.4-0.7 Hz) due to the effects of breathing - - respiratory sinus arrhythmia (RSA), and two low frequency bands (0.03-0.17 Hz) due to thermoregulator and baroreceptor activity.
144
Abstracts / Early Human Development 45 (1996) 133-165
We have previously shown that heart rate variability in the term infant can be entrained by a repetitive thermal stimulus over a frequency range of 0.05-0.15 Hz [1 ]. It has been argued that this phenomenon can be used as an index of autonomic nervous system maturity. This study examines entrainment of heart rate variability in preterm babies. Heart rate and breathing were recorded during quiet sleep, before and during periodic thermal stimulation. Data are presented from 20 sequentially studied appropriately grown preterm babies with a mean gestational age of 31 weeks (29-36). Studies were performed within the first 2 weeks of life, after a feed in a controlled environmental temperature of 26-28°C. These babies were studied with a periodic thermal stimulus at 0.05, 0.10 and 0.15 Hz and spectral analysis was performed on 120-s sections of stable data. Power was measured over several frequency bands: (i) the range of breathing frequencies (RSA) [2]; (ii) the frequency of stimulation; (iii) the low frequency region (0.03-0,17 Hz). During thermal stimulation, there is a local peak of power at the frequency of stimulation for all frequencies, and there is a highly significant increase in power at the frequency of stimulation in comparison to the total increase in low frequency power (P < 0.001). These results support the evidence that preterm babies have functional vasomotor control [3] but we would suggest that they show entrainment to a repetitive thermal stimulus over as wide a range as the appropriately grown term babies and over a wider range of frequencies than has been previously reported [3]. This work was supported by the Joint Research Board, St. Bartholomew's Hospital and the Wellcome Trust.
References [1] C(~steloc. K. ct al. (1994): Early Hum. Dev., 39, 141. [2] Hathorn, M.K.S. (1989): Early Hum. Dev.. 20, 81-99. [3] Lindqvist. A. et al. (1982): Early Hum. Dev., 8, 37-47.
The significance of PEEP C.J. Morley, J.S. Ahluwalia Department of Paediatrics, University of Cambridge, Cambridge, UK, This study investigated the influence of age, peak pressure and F~o 2 on the effect of different levels of PEEP on blood gases and blood pressure.
Methods: After obtaining parental consent, infants ventilated for RDS were studied at