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Biomedical subjects

D Gerhardt

Publications and source records attributed to D Gerhardt.

9 recordsLinked to original sources
PubMed1999

Rhythms and complexity of respiration during sleep in pre-term infants.

The aim of this study is to test rhythmic and complex properties of respiratory control in former ventilated, pre-term infants during quiet and active sleep. The children had a higher risk for sudden infant death due to bronchopulmonary dysplasia (BPD). Twelve infants suffering from BPD and 12 control infants, matched regarding their post-conceptional age, were examined polygraphically during quiet (QS) and active sleep (AS). The respiratory rate (RR), the ratio (LF/HF) between the low-frequency power (LF) and the high-frequency power (HF) of the spectra of the thoracic respiratory effort, and the frequency of the dominant peak within LF (LFF) and HF (HFF) were computed. The correlation dimension (D2) of the respiratory signal was calculated to determine the complexity of the respiratory control. The transcutaneous pO2 (tcpO2) and pCO2 and the oxygen saturation (sO2) were analysed. Infants with BPD had significantly higher RR and HFF during QS (median: BPD 48 breaths min-1; control 32 breaths min-1). tcpO2 and sO2 were significantly lower in the BPD group. No differences were found in LF/HF, LFF or D2 between groups, either in QS or in AS. D2 ranged between 1.8 and 3.8, showing significantly higher values during AS. LFF was found to be lower during active sleep (AS 0.04-0.05 Hz; QS about 0.06 Hz). We propose that in infants with BPD the lower lung compliance and the higher resistance, and possibly also the hypoxaemia, contribute to the acceleration of breathing. The behaviour of RR, spectral parameters and D2 indicates a specific, functional setting rather than a regulatory impairment in infants with BPD.

Bronchopulmonary Dysplasia↗
PubMed1998

[Not Available].

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Germany↗
PubMed1997

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

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.

Bronchopulmonary Dysplasia↗
PubMed1996

[The effect of the laryngeal mask airway on the postoperative incidence of vomiting and sore throat in children].

UNLABELLED: 100 ASA I and II children, aged 4 to 14 years, and scheduled for strabismus surgery, were randomly assigned to one of the following groups: group 1 (n = 50): endotracheal tube, group 2 (n = 50): laryngeal mask airway. Apart from airway management, the anaesthesiological procedures were identical in both groups: induction with 2-3 mg/kg propofol, 0.02 mg/kg alfentanil, 0.05 mg/kg vecuronium, and 0.01 mg/kg atropine. After endotracheal intubation or insertion of the laryngeal mask, anaesthesia was continued with 6-15 mg/kg.h propofol and 10-30 micrograms/kg.h alfentanil. All patients were ventilated with N2O/O2 (2:1). No antiemetics were given, gastric contents were not aspirated. Postoperative nausea and vomiting (PONV) were recorded by 24 h, the incidence of sore throats was recorded 8, 12, and 24 h post-operatively. RESULTS: The incidence of PONV was higher in group 1 (vomiting 48% vs 32%), nausea 28% vs 16% n.s.). Group 1 children had a higher incidence of sore throats (20% vs. 12%, n.s.), of a "lump in the throat" (10% vs 4%, n.s.), hoarseness (24% vs 0%, p < 0.001) and dysarthria (10% vs 4%, n.s.). CONCLUSIONS: In children undergoing strabismus surgery, the laryngeal mask airway was superior to the endotracheal tube in terms of PONV and was associated with fewer local complications such as sore throat.

Adolescent↗
PubMed1980

Human upper esophageal sphincter pressure profile.

The pressure profile of the upper esophageal sphincter was characterized in nine normal subjects. Directionally oriented intraluminal pressures were recorded, at 0.5-cm intervals over a 6-cm segment that encompassed the sphincter, by a high-fidelity low-compliance recording system. The peak resting pressure was directed posteriorly, and the lowest pressures were recorded from the lateral orientations. Significant axial asymmetry was observed with peak posterior pressure 0.55 cm more distal than the anterior pressure. Calculations of variability of pressures recorded at each interval showed the peak pressure to be the most reproducible measurement for each subject. Isotonic saline and acid infusions into the esophagus distal to the sphincter resulted in increased sphincteric peak resting pressure (acid greater than saline). There was axial lengthening of the sphincteric pressure zone with infusion of acid and saline, but this observed increase in length was not significant except at the 50 mmHg level. Pressure profiles recorded during 0.5-cm station pull-throughs were virtually identical to those obtained by a rapid continuous pull-through technique.

Adult↗