Assessment of functional residual capacity using nitrogen washout and plethysmographic techniques in infants with and without bronchopulmonary dysplasia.

OBJECTIVE: In normal infants, functional residual capacity using plethysmography (FRCpleth) exceeds FRC(N2) (using nitrogen washout) and the within-subject difference FRC(pleth-N2) indicates the part of pulmonary gas volume not ventilated during tidal breathing. We postulated that infants with bronchopulmonary dysplasia (BPD) have an elevated FRC(pleth-N2). DESIGN: In a prospective study, FRC(pleth-N2) in healthy newborns (controls n = 17) was compared to that in neonates recovering from the respiratory distress syndrome without BPD (noBPD, studied at discharge, n = 13) and with BPD (BPD1 n = 14, studied at 36 post-conceptional weeks; BPD2 n = 16, at discharge). MEASUREMENTS AND RESULTS: Paired measurements, FRCpleth and FRC(N2), were performed using a plethysmograph (Jaeger, Germany) and an open-circuit nitrogen washout technique (SensorMedics 2600, USA). In comparison to the controls (5.2 ml/kg), FRC(pleth-N2)/kg in noBPD (12.7 ml/kg, p < 0.001), in BPD1 (24.9 ml/kg, p < 0.001) and in BPD2 (13.5 ml/kg, p < 0.001) was significantly higher. Compared with that of the controls FRCpleth was significantly increased in BPD1 (p < 0.001) and FRC(N2) was decreased in noBPD and both BPD groups. CONCLUSION: The FRC(pleth-N2) is a reliable indicator for pulmonary inhomogeneities in infants with respiratory diseases.

Load-dependence of fatigue related changes in tremor around 10 Hz.

OBJECTIVES: The aim of the study was to investigate the effects of different loads on tremor around 10 Hz during fatiguing contractions. METHODS: Eighteen healthy volunteers performed sustained isometric knee extensions at 30%, 50% and 70% maximum voluntary contraction (MVC). During the fatiguing contractions, mechanical recordings were made with a high-resolution force sensor. Tremor-power was calculated for the 6-20 Hz frequency window as a function of time normalized to endurance time. RESULTS: Initial tremor power was different between the high and low load tasks. Changes of tremor with contraction time differed between the three tasks, in that tremor of the 30% MVC contraction showed the least decrease throughout the sustained contraction, whilst that of the 50% and 70% MVC showed progressively higher decreases. At failure, all 3 contractions merged to the same tremor level. CONCLUSION: Load-dependent, fatigue-related 6-20 Hz tremor changes during sustained submaximum voluntary contractions seem mainly the consequence of recruitment of new units and fatigue-related properties of the high threshold motor units of muscles.

Right-sided pulmonary aplasia: longitudinal lung function studies in two cases and comparison to results from term healthy neonates.

Agenesis of the right lung was diagnosed prenatally in two neonates born at 36 and 37 weeks, respectively. Computed tomographic scans and magnetic resonance imaging indicated that both cases had a Type 2 pulmonary agenesis, which was confirmed later by bronchoscopy. Both patients were clinically stable during the neonatal period. Serial pulmonary function tests revealed a decrease in specific respiratory system compliance (sCrs) in both neonates and a marked discrepancy between functional residual capacity measured by the nitrogen washout technique (FRCN2) and by plethysmography (FRCpleth) on follow-up. Early decrease of respiratory system compliance (Crs) and increase of respiratory system resistance (Rrs) in one infant preceded the onset of tracheal stenosis, which remained asymptomatic until the age of 8 weeks, when the infant developed acute respiratory failure requiring intubation and mechanical ventilation with high airway pressures. Aortopexy, implantation of a tissue expander into the right hemithorax, and laser ablation of fibrotic tissue at the site of tracheal stenosis were performed to achieve successful extubation. The second infant remained asymptomatic. Values for lung mechanics and volumes for both infants with pulmonary aplasia were as follows: Crs, 3.43 and 10.60 mL x kP(-1) x kg(-1); sCrs, 0.23 and 1.28 kpa(-1); Rrs, 11.1 and 7.4 kpa x s x L(-1); FRCN2, 14.9 and 10.2 mL x kg(-1); FRCpleth, 28.2 and 25.8 mL x kg(-1); FRCN2: FRCpleth ratio, 0.56 and 0.54 for patients 1 and 2, respectively. These values differed considerably from results of a control group of nine term healthy neonates (Crs, 10.0+/-1.8 mL x kPa(-1) x kg(-1); sCrs, 0.43+/-0.08 kpa(-1); Rrs, 5.10+/-0.55 kpa x s x L(-1); FRCN2, 24.0+/-2.5 mL x kg(-1); FRCpleth, 31.1+/-6.0 mL x kg(-1); FRCN2:FRCpleth ratio, 0.78+/-0.10). In conclusion, serial assessment of lung mechanics and pulmonary gas volumes detects airway obstruction early in neonates with unilateral lung agenesis. Bronchoscopy is recommended. Along with conventional surgical procedures, an expandable implant may improve management or prevent respiratory failure in selected cases.

[Results of SaluCartilage implantation for stage IV chondral defects in the knee joint area]. / Ergebnisse der SaluCartilage-Implantation bei viertgradigen Knorpelschäden im Bereich des Kniegelenks.

AIM OF STUDY: This prospective report presents SaluCartilage hydrogel implants, an alternative therapy option in the treatment of chondral defects. METHODS: For the prospective study between October 2002 and July 2003, 18 patients suffering from stage IV chondral defects received 49 hydrogel implants and were subsequently examined by means of clinical, radiological, and magnetic resonance imaging assessment. The knee function was classified using the McDermott score. RESULTS: The average McDermott score was improved to 75 points (p<0.05) after 3 months postoperatively and to 80 points (p<0.05) 6 months postoperatively, but after 12 months it decreased to 69 points. After 3 and 6 months, the MRI showed in all patients that there was fluid around the hydrogel implants without dislocation. After 12 months postoperatively the hydrogel implants had been destroyed in two patients. CONCLUSION: The short-term results showed subjective and objective improvement of the medical conditions probably because of the placeholder function. This alternative should be critically discussed because of the inadequate connection to the bone with risk of dislocation.

Explaining synchrony in feed-forward networks: are McCulloch-Pitts neurons good enough?

In any scientific theory, the conceptual framework already determines the nature and possible scope of the results. Oversimplification prevents an adequate description of the system, whereas too detailed a description obscures the fundamental principles behind the observed phenomena in addition to misspending time and resources. In theoretical neuroscience, this is an important issue because the description level varies widely from detailed biophysical descriptions to abstract computational models. We discuss the question of the appropriate modeling level in the context of a recent report on synchrony in iteratively constructed feed-forward networks of rat cortex pyramidal neuron somata (Reyes, 2003).

Beckwith-Wiedemann syndrome: difficulties with prenatal diagnosis.

Beckwith-Wiedemann syndrome (BWS), though a well-delineated clinical and morphological entity, can be difficult to diagnose by prenatal ultrasound examination when incomplete forms occur. We present a case with sonographic results including hydronephrosis, cardiomegalia, hepatomegalia, macroglossia, and prominent forehead. No abdominal wall defect was detected. Karyotype was normal. In spite of intensive prenatal diagnostics, BWS could not be diagnosed definitely until birth.

[Polysomnography in infancy--necessary or expensive luxury? Therapeutic and interventional consequences]. / Polysomnographie im Säuglingsalter--notwendig oder teurer Luxus? Therapeutische und interventionelle Konsequenzen.

An increasing amount of polysomnographic studies are performed in early infancy. Complete pediatric sleep laboratory systems are commercially available and provide fast and exhaustive results if operated by trained personnel. Experience in evaluation is necessary, because a broad range of possible diagnostic findings exists, and artifacts are common. Based on longitudinal studies in 31 healthy infants, we present reference values for several polysomnographic parameters. Aberrant results must be interpreted in the context of patient's history, clinical state, and additional laboratory findings. In presence of a clearly defmed indication for polysomnographic testing, clear therapeutic and interventional strategies can be derived. Possible consequences include the stimulation of the respiratory drive by drugs with subsequent polysomnographic control of therapeutic effect, a transfusion, the prescription of a home monitor, and the recommendation of further diagnostics or of control polysomnographies. In conclusion, infant polysomnography is an important diagnostic tool in pediatrics.

Pulmonary agenesis in a newborn: implantation of tissue expander to prevent a mediastinal shift.

Unilateral pulmonary agenesis is a rare congenital anomaly whose aetiology is not completely known. Vitamin A deficiency, viral agents, or genetic factors are discussed. The incidence was estimated at 1 in 10,000-15,000 autopsies by several authors. Associated malformations, mainly affecting the cardiovascular, gastrointestinal, and musculoskeletal system influence the prognosis of patients as does the location of the missing lung. We report the implantation of a tissue-expander in a three-months-old infant suffering from a right-sided lung agenesis associated with sinus-venosus defect. Other malformations were excluded by sonographic methods. Mediastinal shift with dextropositio cordis in compensatory emphysema of the left lung and frequent infections were the cardinal symptoms. These led to cardiopulmonary decompensation twice. The implantation of the tissue-expander was performed following an aortopexy, which was only temporarily successful. This method allows the filler to be adapted with age to the pleural volume by instillation of sterile saline solution via a microport. Whether or not thorax deformities and scoliosis will be prevented cannot be predicted exactly at this time.