[Risk adjusted assessment of quality of perinatal centers - results of perinatal/neonatal quality surveillance in Saxonia]. / Risikoadjustierte Qualitätsbeurteilung in Perinatalzentren ausgehend von der Perinatal- und Neonatalerhebung in Sachsen.

BACKGROUND: The weak point of the country-wide perinatal/neonatal quality surveillance as a tool for evaluation of achievements of a distinct clinic, is the ignorance of interhospital differences in the case-mix of patients. Therefore, that approach can not result in a reliable bench marking. OBJECTIVE: To adjust the results of quality assessment of different hospitals according to their risk profile of patients by multivariate analysis. METHOD: The perinatal/neonatal data base of 12.783 newborns of the saxonian quality surveillance from 1998 to 2000 was analyzed. 4 relevant quality indicators of newborn outcome -- a) severe intraventricular hemorrhage in preterm infants < 1500 g, b) death in hospital of preterm infants < 1500 g, c) death in newborns with birth weight > 2500 g and d) hypoxic-ischemic encephalopathy -- were targeted to find out specific risk predictors by considering 26 risk factors. A logistic regression model was used to develop the risk predictors. RESULTS: Risk predictors for the 4 quality indicators could be described by 3 - 9 out of 26 analyzed risk factors. The AUC (ROC)-values for these quality indicators were 82, 89, 89 and 89 %, what signifies their reliability. Using the new specific predictors for calculation the risk adjusted incidence rates of quality indicator yielded in some remarkable changes. The apparent differences in the outcome criteria of analyzed hospitals were found to be much less pronounced. CONCLUSION: The application of the proposed method for risk adjustment of quality indicators makes it possible to perform a more objective comparison of neonatal outcome criteria between different hospitals or regions.

[Determination of respiratory system compliance from resonance frequency--animal experiment]. / Bestimmung der Compliance des respiratorischen Systems aus der Resonanzfrequenz--tierexperimentelle Studie.

10 anaesthetized and tracheotomized rabbits were used to test the possibility for calculation of total respiratory system compliance from resonance frequency (CR). Reference values were obtained by inflation method compliance (CI). A new servocontrolled infant ventilator was used with an integrated negative ventilator resistance mode for resistive unloading of combined resistances of lung, endotracheal tube and ventilator. This evoked oscillation at resonant frequency. By analogy with electrical circuit theory compliance was calculated as follows: CR = 1/(4 pi 2 x square root I.RF2). Pairs of CI and CR values were obtained from each animal during spontaneous breathing, after pancuronium relaxation and after surfactant depletion by lavage. There was found a significant linear correlation between CR and CI values (CR = 1.1 x CI-0.74; r = 0.97).

High frequency oscillatory ventilation near resonant frequency of the respiratory system in rabbits with normal and surfactant depleted lungs.

It has been suggested that high frequency oscillatory ventilation (HFV) might improve gas exchange and reduce the risk of pressure-related side-effects compared to conventional mechanical ventilation (CMV). Whereas most studies have used arbitrarily set frequencies for HFV, we evaluated the effects of HFV near resonant frequency (fr). Anaesthetised and tracheotomized adult rabbits (n = 10; 3.8-5.1 kg body weight) were ventilated by alternating periods of CMV and HFV near fr. Negative ventilator resistance was used for complete resistive unloading of the respiratory system before each HFV period. This enabled a continuous swinging at resonance thus allowing measurement of fr and selection of exactly that frequency for the HFV run. Intra-animal CMV-HFV comparisons (n = 4) were performed on each animal: with healthy lungs at a mean airway pressure (MAP) of 0.5 kPa and after saline lung lavage at MAPs of less than 1.5 kPa; 1.5-1.8 kPa; greater than 1.8 kPa. Surfactant removal caused total respiratory system compliance (Ctot) to decrease from 44 +/- 5 to 22 +/- 3 ml/kPa. Corresponding fr was 244 +/- 48 and 360 +/- 30 min-1, respectively. HFV produced effective pulmonary gas exchange but did not improve arterial oxygenation in comparison with CMV at matched MAPs both before and after surfactant depletion. Volume amplitudes of oscillation necessary to achieve normocapnia were slightly above the natural plus equipment (2 ml) dead space. Maximum intra-alveolar pressure (Pmax) was calculated for the HFV runs from MAP, Ctot, and the volume amplitude of oscillation. Pmax during CMV was nearly twice that during HFV at equivalent PaCO2 and equivalent MAPs throughout the experiments.

A method of calculating total respiratory system compliance from resonant frequency: validity in a rabbit model.

Ten anesthetized, tracheotomized, adult rabbits were used to test the validity of a method for calculation of total respiratory system compliance from resonant frequency (Cr). Reference values were obtained during constant flow inflation of the relaxed respiratory system by dividing the volume gain by the related difference in pressure at the airway opening (inflation method compliance, Ci). The animals were connected to a new type of servo-controlled infant ventilator. Besides volume-controlled mechanical ventilation at constant inspiratory flow rate and intermittent mandatory ventilation, there is a negative ventilator resistance mode integrated in this device for resistive unloading (Schulze A, Schaller P, Gehrhardt B, Mädler H-J, Gmyrek D: Pediatr Res 28:79-82, 1990). To measure resonant frequency (fr), the respiratory system was totally unloaded for a short period by a negative ventilator resistance exceeding the combined resistances of the endotracheal tube and airways. This evoked a continuous oscillation at fr. By analogy with electrical circuit theory, Cr was calculated according to C = 1/(4 pi 2.I.fr2) where C is compliance and I is inertance. The inertance of the endotracheal tube is given and that of the bronchial tree was ignored assuming a much greater total cross-sectional area and therefore much lower inertance when compared with the endotracheal tube. Three pairs of Ci - Cr values were obtained from each animal: 1) during intact respiratory muscle activity; 2) after pancuronium relaxation, and 3) after surfactant depletion by saline washout.(ABSTRACT TRUNCATED AT 250 WORDS)

An infant ventilator technique for resistive unloading during spontaneous breathing. Results in a rabbit model of airway obstruction.

The combined system of ventilator circuit, endotracheal tube, and lung commonly imposes a resistive load on spontaneous breathing efforts. It is possible to compensate for this positive resistance by a device generating a "negative ventilator resistance" (NVR), i.e. delivering a positive pressure during inspiration and a negative pressure during expiration in constant proportion to the instantaneous flow of the spontaneous breathing. The concept of NVR implies that there must not be any phase lag between flow and pressure signals. In eight anesthetized, intubated, spontaneously breathing rabbits (mean body wt 3570 g, range 2900-4600 g), challenged either by aerosolized histamine or an extrapulmonary resistive load, lung mechanical data were calculated from esophageal pressure and flow signals. Each animal served as its own control with and without NVR. In a total of 39 experiments, NVR was applied in amounts between 1 and 15 kPa.s/L. During both types of additional resistive load, NVR immediately reduced the resistive work of breathing. There was a strong linear correlation between the amount of NVR applied and the decrease in total resistance, where the total resistance equals the resistive load on the animal's respiratory muscles (sum of the resistances of all components of the combined respirator-lung system): r = 0.93, p less than 0.001. The relationship between NVR and the drop in resistive work per mL of tidal volume was similar: r = 0.85, p less than 0.001. Throughout the experiments, NVR operated in perfect synchronization with the animal's spontaneous breathing activity.

Titration of continuous positive airway pressure by the pattern of breathing: analysis of flow-volume-time relationships by a noninvasive computerized system.

Infants can defend or even dynamically elevate their functional residual capacity with additional respiratory muscle work by retarding early expiratory airflow (V) with postinspiration inspiratory muscle activity and/or laryngeal narrowing, or by starting inspiration before expiration to the relaxation volume has been completed. In order to study the effect of continuous positive airway pressure (CPAP) on both phenomena in 23 infants (birthweight 1,746 +/- 417 g), we elevated the airway pressure stepwise in 0.2 kPa increments. A computerized bedside flow-volume (V/V) analysis was used for evaluation. In 16 "responders" early expiration braking decreased and "premature inspiratory interruption" was postponed at an "appropriate CPAP level." The linear segment (relaxation line) of the V/V-loop was lengthened until expiratory time reached a maximum. Elevation of CPAP beyond this level again produced a rapid, shallow pattern, often combined with flow acceleration late in expiration (recruitment of expiratory muscles). In the remaining seven infants (non-responders) these latter signs of excessive airway pressure already occurred at the lowest CPAP levels applied during the "titration trials." Respiratory rate without CPAP was different between responders (84 +/- 17/min) and non-responders (46 +/- 17/min). This approach for determining the appropriate CPAP level might reduce the risk of respiratory muscle fatigue.

[Neuropsychiatric disorders in very-low-birthweight newborn infants (VLBW-infants)--before and after the introduction of modern perinatal medicine. 3. Discussion of trends in quality of survival (CNS morbidity) and conclusions]. / Neuropsychiatrische Störungen bei Neugeborenen mit sehr niedrigem Geburtsgewicht (VLBW-infants)--vor und nach Einführung der modernen Perinatalmedizin. 3. Mitteilung: Diskussion zu Trends der Uberlebensqualität (ZNS-Morbidität) und Schlussfolgerungen.

The reduction of both the severe CNS-disturbances (major CNS-handicaps) as a whole and the infantile cerebral palsies (ICP), epilepsies, and mental retardations (oligophrenias) especially, can be attributed to the comprehensively improved pre-, intra- and postnatal care since the 60/70-ies. The best indicator is the decreasing ICP, because 60% of this disturbance is caused perinatally. It is closely associated with cerebral hemorrhages. In several centers, in Sweden and in West-Australia, an isolated recrudescence of ICP was noted. This fact is probably caused by a very active management of respirator therapy in some perinatological centers. However, today there is an effective therapy of several potential causes of perinatal cerebral lesions, i.e. hypoglycemia, hypothermia, asphyxia, RDS, and hyperbilirubinemia. The therapy of these diseases is simultaneously a prevention of the possible consecutive cerebral lesion as well. In the past, only two causes for CNS-disturbances have scarcely been influenced: cerebral hemorrhage, and nosocomial infections. Conclusions for the strategy of the further perinatal care can be deduced from these analyses: prevention of the extremely preterm deliveries, improvement of the perinatal care, prevention of cerebral hemorrhages and nosocomial infections, and responsible ethical decision about the application of the respirator therapy in the individual case.

[Neuropsychiatric disorders in newborn infants with very low birth weight (VLBW infants)--before and following introduction of modern perinatal medicine. 2. Infantile cerebral palsy, epilepsy and mental handicap (oligophrenia)]. / Neuropsychiatrische Störungen bei Neugeborenen mit sehr niedrigem Geburtsgewicht (VLBW-infants)--vor und nach Einführung der modernen Perinatalmedizin. 2. Mitteilung: Infantile Cerebralparesen (ICP), Epilepsie und geistige Behinderungen (Oligophrenien).

Simultaneously with the introduction of modern perinatal intensive therapy the infantile cerebral palsies (ICP) of VLBW infants dropped on the average from 23 to 5.9 per cent. In Swedish and West-Australian ICP studies a considerable decrease in the ICP incidence was found in the 60's, but there was again a slight increase in the 70's. A decrease in the epilepsies was found on an average from 9 to 1.6 per cent, whereby in 10 of 16 actual studies mostly performed at early follow-up age no epilepsies were reported. A decrease in the mental retardations (oligophrenias) was found on an average from 22 to 10.6 per cent. There was especially noteworthy a reduction of the severe mental retardations from 8 to 10 per cent to an average of 2.3 per cent.

[Neuropsychiatric disorders in newborn infants with very low birth weight (VLBW infants)--before and following introduction of modern perinatal medicine. 1. Overview of the problem, criteria for quality of survival, major CNS disorders (major handicap)]. / Neuropsychiatrische Störungen bei Neugeborenen mit sehr niedrigem Geburtsgewicht (VLBW-infants)--vor und nach Einführung der modernen Perinatalmedizin. 1. Mitteilung: Ubersicht zum Problem, Kriterien der Uberlebensqualität, schwere ZNS-Störungen ("major handicap").

The survival quality of very low birthweight infants (VLBW infants) is highly actual just even in the time of modern perinatal medicine. Through the development and permanent improvement of the perinatal intensive therapy the survival chances of VLBW infants could be improved significantly in the last 25 years. In the 70's survival rates of 60-84 per cent were achieved in VLBW infants, in the leading centers even rates of 86 and 90.5 percent, respectively. In the 70's an enormous improvement in the survival rates from 20-45 per cent was achieved in tiny premature infants (birth weight 1,000 gm and less), too. However, the efforts of gynecologists and neonatologists to reduce the mortality of low birth-weight infants are again and again blamed for possibly obtaining successes with an increase in CNS morbidity. The parallel analysis of some brain damage groups in VLBW infants seems suitable to gain a clear statement if modern perinatal medicine contributes to reduce the frequency of early infantile cerebral damages and their consecutive handicaps altogether. In an extensive review of literature it is tried to prove this for the major CNS handicaps altogether and separately for the infantile cerebral palsies, epilepsies and mental retardations (oligophrenias). Simultaneously with an average increase from 29.7 to 69.5 per cent of the healthy surviving children, there was a reduction of major CNS handicaps on the average from 36 to 12 per cent.

High frequency oscillatory and conventional mechanical ventilation in experimental surfactant deficiency: a study using a new infant ventilator technique.

The performance of a new infant ventilator system had to be evaluated. Technically it is characterized by flow (V)- and pressure (P)-transducers mounted immediately near the endotracheal tube. A microcomputer works as a function generator and governs servo-controllers for V and P thus offering a multiplicity of different modes both of the conventional (CMV) and high frequency oscillatory (HFO) type. The additional dead space imposed by the system is identical with its internal compressible volume of 2 ml. Serial pulmonary lavages were performed in 17 adult rabbits while on CMV. PaO2 per unit of mean airway pressure (MAP) decreased thereby from 95.9 +/- 29.3 to 9.0 +/- 6.7 (kPa/kPa). The animals were then alternately ventilated by HFO (5, 10, or 20 Hz) and CMV, at matched MAP's. No significant difference in PaO2 between the two methods was revealed in intra-animal comparisons except a slight superiority of CMV at MAP's above 1.7 kPa (P less than 0.05). There was no clear linear relationship between PaO2 and MAP both at CMV and HFO. A strong increase in PaO2 often occurred beyond a MAP threshold. In 37 postlavage HFO runs at 5 Hz in 13 animals volume amplitudes of 3.19 +/- 0.5 ml/kg of bodyweight resulted in PaCO2 levels of 6.29 +/- 1.87 kPa. Except in one experiment (10 Hz) volume amplitudes below the natural dead space produced arterial hypercapnia.

Pathogenetic significance of venous hyperoxaemia in retinopathy of prematurity.

Ten underweight newborns with severe retinopathy of prematurity (ROP) and 18 newborns with slight changes in the sense of ROP were compared with 66 healthy infants. The distribution of 13 possibly pathogenetically effective features in these 3 groups of patients was studied by means of variance analysis. The greatest significance resulted for multiple blood transfusions and exchange transfusions. From this it was concluded that the toxic oxygen effect on the immature retina was probably more dependent on the venous PO2 (determined by Hb concentration, O2-affinity, arterial PO2, and blood flow) than on the isolated arterial PO2.

[Clinical and computed tomographic observations on newborn infants with generalized brain edema due to perinatal asphyxia]. / Klinische und computertomographische Verlaufsbeobachtungen bei Neugeborenen mit generalisiertem Hirnödem infolge perinataler Asphyxie.

We observed a sudden respiratory arrest in four term newborn infants after a clinically symptom-free period. There were no cardiac, pulmonary or metabolic changes responsible for these events. Signs of cerebral dysfunction existed (muscular hypotonia, jitterness, seizures). Cranial computerized tomographic scans were performed during the period of respirator treatment within the first week of life. The density of the brain structures was significantly decreased in all cases, three of the patients showed a complete compression of the lateral ventricles. These findings indicated severe brain swelling as a consequence of cerebral hypoxia. There was a history of umbilical cord occlusion in two cases. In the remaining patients we must assume an undetected hypoxic-ischemic episode prior to the onset of labor. We used hyperventilation, corticosteroids, phenobarbital, diuretics and fluid restriction for therapy. Later on the babies received special physiotherapy. Control CT-scans were performed during the fourth or fifth week of life. The findings were normal in one patient. Signs of mild focal brain atrophy developed in two babies. A more severe cortical atrophic lesion of both temporal lobes was found in one patient. He suffered from a slight cerebral palsy. No neurodevelopmental handicaps could be found in all the other patients on long term follow-up. The EEG examination was performed between the fifth and seventh month of life. No pathologic changes were observed. We conclude that severe generalized brain edema in the newborn is not necessarily followed by extensive brain damage. We think it important to develop more sensitive methods for detecting a hypoxic ischemic crisis preceding the birth.