A Wearable Daily Respiration Monitoring System Using PDMS-graphene Compound Tensile Sensor for Adult

A wearable respiration monitoring system based on Respiratory induction plethysmography (RIP) using a new Polydimethylsiloxane-graphene (PDMS-graphene) compound tensile sensor is proposed. The manufacture procedure of this novel resistance-based tensile sensor is presented together with a wireless acquisition system. The proposed sensor shows a high sensitivity during stretching and a promising cyclic stability for continuous 3,600 cycles. Statistical analysis confirms a high correlation of respiratory rate monitoring between the proposed system and a medical-level instrument. This proposed system based on RIP, using a new PDMS-graphene compound tensile sensor can acquire respiratory signal unobtrusively with high accuracy and satisfactory user experience, and thus has great potential in home monitoring scenarios.

Anatomically Realistic Neonatal Heart Model for Use in Neonatal Patient Simulators

Neonatal patient simulators (NPS) are artificial patient surrogates used in the context of medical simulation training. Neonatologists and nursing staff practice clinical interventions such as chest compressions to ensure patient survival in the case of bradycardia or cardiac arrest. The simulators used currently are of low physical fidelity and therefore cannot provide qualitative insight into the procedure of chest compressions. The embedding of an anatomically realistic heart model in future simulators enables the detection of cardiac output generated during chest compressions; this can provide clinicians with an output parameter, which can deepen the understanding of the effect of the compressions in relation to the amount of blood flow generated. Before this monitoring can be achieved, an anatomically realistic heart model must be created containing: two atria, two ventricles, four heart valves, pulmonary veins and arteries, and systemic veins and arteries. This protocol describes the procedure for creating such a functional artificial neonatal heart model by utilizing a combination of magnetic resonance imaging (MRI), 3D printing, and casting in the form of cold injection molding. Using this method with flexible 3D printed inner molds in the injection molding process, an anatomically realistic heart model can be obtained.

Changes in autonomic regulation due to Kangaroo care remain unaffected by using a swaddling device

Aim

To investigate the effects of a swaddling device known as the Hugsy (Hugsy, Eindhoven, the Netherlands) towards improving autonomic regulation. This device can be used both in the incubator and during Kangaroo care to absorb parental scent and warmth. After Kangaroo care, these stimuli can continue to be experienced by infants, while in the incubator. Additionally, a pre‐recorded heartbeat sound can be played.

Method

Autonomic regulation was compared in preterm infants before, during and after Kangaroo care with and without the use of a swaddling device in a within‐subject study carried out in a level III neonatal intensive care unit. Descriptive statistics and effect sizes were calculated corresponding to changes in heart rate, respiratory rate, oxygen saturation, temperature and heart rate variability on intervention versus control days.

Results

In this study of 20 infants with a median (interquartile range) gestational age of 28.4 (27–29.9) weeks, Kangaroo care was associated with a decrease in heart rate, respiratory rate and heart rate variability on both intervention and control days. There were no differences between intervention and control days.

Conclusion

The use of an alternative swaddling device aimed at facilitating Kangaroo care did not enhance autonomic regulation, as measured by vital signs and heart rate variability.

Unlike Kangaroo care, mechanically simulated Kangaroo care does not change heart rate variability in preterm neonates

BACKGROUND

While numerous positive effects of Kangaroo care (KC) have been reported, the duration that parents can spend kangarooing is often limited.

AIM

To investigate whether a mattress that aims to mimic breathing motion and the sounds of heartbeats (BabyBe GMBH, Stuttgart, Germany) can simulate aspects of KC in preterm infants as measured by features of heart rate variability (HRV).

METHODS

A within-subject study design was employed in which every routine KC session was followed by a BabyBe (BB) session, with a washout period of at least 2 h in between. Nurses annotated the start and end times of KC and BB sessions. Data from the pre-KC, KC, post-KC, pre-BB, BB and post-BB were retrieved from the patient monitor via a data warehouse. Five time-domain features of HRV were used to compare both types of intervention. Two of these features, the percentage of decelerations (pDec) and the standard deviation of decelerations (SDDec), were developed in a previous study to capture the contribution of transient heart rate decelerations to HRV, a measure of regulatory instability.

RESULTS

A total of 182 KC and 180 BabyBe sessions were analyzed in 20 preterm infants. Overall, HRV decreased during KC and after KC. Two of the five features showed a decrease during KC, and all features decreased in the post-KC period (p ≤ 0.01). The BB mattress as employed in this study did not affect HRV.

CONCLUSION

Unlike KC, a mattress that attempts to mimic breathing motion and heartbeat sounds does not affect HRV of preterm infants.

Viewpoints of Parents and Nurses on How to Design Products to Enhance Parent-Infant Bonding at Neonatal Intensive Care Units: A Qualitative Study Based on Existing Designs

AIM

To investigate how product design can be used to improve parent-infant bonding in a neonatal intensive care unit.

BACKGROUND

Impaired parent-infant bonding is an inevitable consequence of premature birth, which negatively influences development. Products, systems, or services that support the bonding process might counter these negative influences.

METHOD

The first step was to trace existing products by performing a literature search in PubMed, the university library, and Google. The identified existing designs were then used in semistructured interviews with nurses and parents to get insights into their desires and recommendations for product design to enhance bonding. Interviews contained open questions and a multiple-choice questionnaire based on the literature search.

RESULTS

In total, 17 existing design types were used in interviews with 11 parents and 23 nurses. All nurses explicitly stated that practicality was the first criterion designs aimed at enhancing bonding definitely had to meet. All parents indicated that they would like to use a design to enhance bonding if that would contribute to their child's health and development. For both parents and nurses, the most valuable way to enhance bonding seemed to be products to improve Kangaroo care; however, their specific desires varied substantially. Therefore, seven recurring themes were defined, resulting in nine general recommendations and six opportunities intended to enhance parent-infant bonding.

CONCLUSION

This study provides design recommendations and opportunities based on parents' and nurses' expert opinions. Designing to enhance bonding is considered valuable; however, designs should match the stakeholders' desires and conditions.

An innovative design for cardiopulmonary resuscitation manikins based on a human-like thorax and embedded flow sensors

Cardiopulmonary resuscitation manikins are used for training personnel in performing cardiopulmonary resuscitation. State-of-the-art cardiopulmonary resuscitation manikins are still anatomically and physiologically low-fidelity designs. The aim of this research was to design a manikin that offers high anatomical and physiological fidelity and has a cardiac and respiratory system along with integrated flow sensors to monitor cardiac output and air displacement in response to cardiopulmonary resuscitation. This manikin was designed in accordance with anatomical dimensions using a polyoxymethylene rib cage connected to a vertebral column from an anatomical female model. The respiratory system was composed of silicon-coated memory foam mimicking lungs, a polyvinylchloride bronchus and a latex trachea. The cardiovascular system was composed of two sets of latex tubing representing the pulmonary and aortic arteries which were connected to latex balloons mimicking the ventricles and lumped abdominal volumes, respectively. These balloons were filled with Life/form simulation blood and placed inside polyether foam. The respiratory and cardiovascular systems were equipped with flow sensors to gather data in response to chest compressions. Three non-medical professionals performed chest compressions on this manikin yielding data corresponding to force-displacement while the flow sensors provided feedback. The force-displacement tests on this manikin show a desirable nonlinear behaviour mimicking chest compressions during cardiopulmonary resuscitation in humans. In addition, the flow sensors provide valuable data on the internal effects of cardiopulmonary resuscitation. In conclusion, scientifically designed and anatomically high-fidelity designs of cardiopulmonary resuscitation manikins that embed flow sensors can improve physiological fidelity and provide useful feedback data.

Features of Heart Rate Variability Capture Regulatory Changes During Kangaroo Care in Preterm Infants

OBJECTIVE

To determine whether heart rate variability (HRV) can serve as a surrogate measure to track regulatory changes during kangaroo care, a period of parental coregulation distinct from regulation within the incubator.

STUDY DESIGN

Nurses annotated the starting and ending times of kangaroo care for 3 months. The pre-kangaroo care, during-kangaroo care, and post-kangaroo care data were retrieved in infants with at least 10 accurately annotated kangaroo care sessions. Eight HRV features (5 in the time domain and 3 in the frequency domain) were used to visually and statistically compare the pre-kangaroo care and during-kangaroo care periods. Two of these features, capturing the percentage of heart rate decelerations and the extent of heart rate decelerations, were newly developed for preterm infants.

RESULTS

A total of 191 kangaroo care sessions were investigated in 11 preterm infants. Despite clinically irrelevant changes in vital signs, 6 of the 8 HRV features (SD of normal-to-normal intervals, root mean square of the SD, percentage of consecutive normal-to-normal intervals that differ by >50 ms, SD of heart rate decelerations, high-frequency power, and low-frequency/high-frequency ratio) showed a visible and statistically significant difference (P <.01) between stable periods of kangaroo care and pre-kangaroo care. HRV was reduced during kangaroo care owing to a decrease in the extent of transient heart rate decelerations.

CONCLUSION

HRV-based features may be clinically useful for capturing the dynamic changes in autonomic regulation in response to kangaroo care and other changes in environment and state.

A Review of Wearable Sensor Systems for Monitoring Body Movements of Neonates

Characteristics of physical movements are indicative of infants' neuro-motor development and brain dysfunction. For instance, infant seizure, a clinical signal of brain dysfunction, could be identified and predicted by monitoring its physical movements. With the advance of wearable sensor technology, including the miniaturization of sensors, and the increasing broad application of micro- and nanotechnology, and smart fabrics in wearable sensor systems, it is now possible to collect, store, and process multimodal signal data of infant movements in a more efficient, more comfortable, and non-intrusive way. This review aims to depict the state-of-the-art of wearable sensor systems for infant movement monitoring. We also discuss its clinical significance and the aspect of system design.

Maternal allopurinol administration during suspected fetal hypoxia: a novel neuroprotective intervention? A multicentre randomised placebo controlled trial

OBJECTIVE

To determine whether maternal allopurinol treatment during suspected fetal hypoxia would reduce the release of biomarkers associated with neonatal brain damage.

DESIGN

A randomised double-blind placebo controlled multicentre trial.

PATIENTS

We studied women in labour at term with clinical indices of fetal hypoxia, prompting immediate delivery.

SETTING

Delivery rooms of 11 Dutch hospitals.

INTERVENTION

When immediate delivery was foreseen based on suspected fetal hypoxia, women were allocated to receive allopurinol 500 mg intravenous (ALLO) or placebo intravenous (CONT).

MAIN OUTCOME MEASURES

Primary endpoint was the difference in cord S100ß, a tissue-specific biomarker for brain damage.

RESULTS

222 women were randomised to receive allopurinol (ALLO, n=111) or placebo (CONT, n=111). Cord S100ß was not significantly different between the two groups: 44.5 pg/mL (IQR 20.2-71.4) in the ALLO group versus 54.9 pg/mL (IQR 26.8-94.7) in the CONT group (difference in median -7.69 (95% CI -24.9 to 9.52)). Post hoc subgroup analysis showed a potential treatment effect of allopurinol on the proportion of infants with a cord S100ß value above the 75th percentile in girls (ALLO n=5 (12%) vs CONT n=10 (31%); risk ratio (RR) 0.37 (95% CI 0.14 to 0.99)) but not in boys (ALLO n=18 (32%) vs CONT n=15 (25%); RR 1.4 (95% CI 0.84 to 2.3)). Also, cord neuroketal levels were significantly lower in girls treated with allopurinol as compared with placebo treated girls: 18.0 pg/mL (95% CI 12.1 to 26.9) in the ALLO group versus 32.2 pg/mL (95% CI 22.7 to 45.7) in the CONT group (geometric mean difference -16.4 (95% CI -24.6 to -1.64)).

CONCLUSIONS

Maternal treatment with allopurinol during fetal hypoxia did not significantly lower neuronal damage markers in cord blood. Post hoc analysis revealed a potential beneficial treatment effect in girls.

TRIAL REGISTRATION NUMBER

NCT00189007, Dutch Trial Register NTR1383.

Non-contact heart rate monitoring utilizing camera photoplethysmography in the neonatal intensive care unit - a pilot study

BACKGROUND

Presently the heart rate is monitored in the Neonatal Intensive Care Unit with contact sensors: electrocardiogram or pulse oximetry. These techniques can cause injuries and infections, particularly in very premature infants with fragile skin. Camera based plethysmography was recently demonstrated in adults as a contactless method to determine heart rate.

AIM

To investigate the feasibility of this technique for NICU patients and identify challenging conditions.

STUDY DESIGN AND PARTICIPANTS

Video recordings using only ambient light were made of 19 infants at two NICUs in California and The Netherlands. Heart rate can be derived from these recordings because each cardiovascular pulse wave induces minute pulsatile skin color changes, invisible to the eye but measurable with a camera.

RESULTS

In all infants the heart beat induced photoplethysmographic signal was strong enough to be measured. Low ambient light level and infant motion prevented successful measurement from time to time.

CONCLUSIONS

Contactless heart rate monitoring by means of a camera using ambient light was demonstrated for the first time in the NICU population and appears feasible. Better hardware and improved algorithms are required to increase robustness.

Efficacy of feed forward and feedback signaling for inflations and chest compression pressure during cardiopulmonary resuscitation in a newborn mannequin

BACKGROUND

The objective of the study was to evaluate a device that supports professionals during neonatal cardiopulmonary resuscitation (CPR). The device features a box that generates an audio-prompted rate guidance (feed forward) for inflations and compressions, and a transparent foil that is placed over the chest with marks for inter nipple line and sternum with LED's incorporated in the foil indicating the exerted force (feedback).

METHODS

Ten pairs (nurse/doctor) performed CPR on a newborn resuscitation mannequin. All pairs initially performed two sessions. Thereafter two sessions were performed in similar way, after randomization in 5 pairs that used the device and 5 pairs that performed CPR without the device (controls). A rhythm score was calculated based on the number of CPR cycles that were performed correctly.

RESULTS

The rhythm score with the device improved from 85 ± 14 to 99 ± 2% (P < 0.05). In the control group no differences were observed. The recorded pressures with the device increased from 3.1 ± 1.6 to 4.9 ± 0.8 arbitrary units (P < 0.05). The second performance of the teams showed significant better results for the group with the CPR device compared to the controls.

CONCLUSION

Feed forward and feedback signaling leads to a more constant rhythm and chest compression pressure during CPR.

Multi-channel amplitude-integrated EEG characteristics in preterm infants with a normal neurodevelopment at two years of corrected age

AIM

To analyze quantitatively multi-channel amplitude-integrated EEG (aEEG) characteristics and assess regional differences.

METHODS

We investigated 40 preterm infants (postmenstrual age, PMA: range 27-37 weeks) with normal follow-up at 24 months of age, at a median postnatal age of 8 days using 4-h EEG recordings according to the international 10-20 system reduced montage. Nine (3 transverse and 6 longitudinal) channels were selected and converted to aEEG registrations. For each aEEG registration, lower margin amplitude (LMA), upper margin amplitude (UMA) and bandwidth (UMA-LMA) were calculated.

RESULTS

In all channels PMA and LMA showed strong positive correlations. Below 32 weeks of PMA, LMA was ≤5μV. Linear regression analysis showed a maximum LMA difference between channels of approximately 2 and 1μV at 27 and 37 weeks of PMA, respectively. The lowest are LMA values in the occipital channel and the highest values are in centro-occipital channels. In the frontal, centro-temporal and centro-occipital channels, UMA and bandwidth changed with PMA. No differences in LMA, UMA and bandwidth were found between hemispheres. Skewness of LMA values strongly correlated with PMA, positive skewness indicating an immature brain (PMA≤32 weeks) and negative skewness a maturing (PMA>32 weeks) brain.

CONCLUSIONS

We detected symmetric increase of aEEG characteristics, indicating symmetric brain maturation of the left and right hemispheres. Our findings demonstrate the clinical potential of computer-assisted analyses of aEEG recordings in detecting maturational features which are not readily identified visually. This may provide an objective and reproducible method for assessing brain maturation and long-term prognosis.

Maturational changes in automated EEG spectral power analysis in preterm infants

Our study aimed at automated power spectral analysis of the EEG in preterm infants to identify changes of spectral measures with maturation. Weekly (10-20 montage) 4-h EEG recordings were performed in 18 preterm infants with GA <32 wk and normal neurological follow-up at 2 y, resulting in 79 recordings studied from 27(+4) to 36(+3) wk of postmenstrual age (PMA, GA + postnatal age). Automated spectral analysis was performed on 4-h EEG recordings. The frequency spectrum was divided in delta 1 (0.5-1 Hz), delta 2 (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) band. Absolute and relative power of each frequency band and spectral edge frequency were calculated. Maturational changes in spectral measures were observed most clearly in the centrotemporal channels. With advancing PMA, absolute powers of delta 1 to 2 and theta decreased. With advancing PMA, relative power of delta 1 decreased and relative powers of alpha and beta increased, respectively. In conclusion, with maturation, spectral analysis of the EEG showed a significant shift from the lower to the higher frequencies. Computer analysis of EEG will allow an objective and reproducible analysis for long-term prognosis and/or stratification of clinical treatment.

Rhythm of Life Aid (ROLA): an integrated sensor system for supporting medical staff during cardiopulmonary resuscitation (CPR) of newborn infants

During the stress of cardiopulmonary resuscitation (CPR), it is difficult to maintain the right rhythm and correct ratio of insufflations to chest compressions and to exert the compressions at a constant pressure. In this paper, we propose and demonstrate an integrated sensor system-the "Rhythm of Life Aid" (ROLA) to support medical staff during CPR of newborn infants. The design concept is based on interactive audio and visual feedback with consideration of functionalities and user friendliness. A prototype ROLA device is built, consisting of a transparent foil integrated with pressure sensor and electroluminescent foil actuators for indication of the exerted chest compression pressure, as well as an audio box to generate distinctive sounds as audio guidance for insufflations and compressions. To evaluate the performance of the ROLA device, a sensory mannequin and a dedicated software interface are implemented to give immediate feedback and record data for further processing. Tests of the ROLA prototype on the sensory mannequin by ten pairs of a doctor and a nurse at Máxima Medical Centre in Veldhoven, The Netherlands show that the use of ROLA device achieves a more constant rhythm and pressure of chest compressions during CPR of newborn infants.

Antenatal allopurinol for reduction of birth asphyxia induced brain damage (ALLO-Trial); a randomized double blind placebo controlled multicenter study

BACKGROUND

Hypoxic-ischaemic encephalopathy is associated with development of cerebral palsy and cognitive disability later in life and is therefore one of the fundamental problems in perinatal medicine. The xanthine-oxidase inhibitor allopurinol reduces the formation of free radicals, thereby limiting the amount of hypoxia-reperfusion damage. In case of suspected intra-uterine hypoxia, both animal and human studies suggest that maternal administration of allopurinol immediately prior to delivery reduces hypoxic-ischaemic encephalopathy.

METHODS/DESIGN

The proposed trial is a randomized double blind placebo controlled multicenter study in pregnant women at term in whom the foetus is suspected of intra-uterine hypoxia.Allopurinol 500 mg IV or placebo will be administered antenatally to the pregnant woman when foetal hypoxia is suspected. Foetal distress is being diagnosed by the clinician as an abnormal or non-reassuring foetal heart rate trace, preferably accompanied by either significant ST-wave abnormalities (as detected by the STAN-monitor) or an abnormal foetal blood scalp sampling (pH < 7.20).Primary outcome measures are the amount of S100B (a marker for brain tissue damage) and the severity of oxidative stress (measured by isoprostane, neuroprostane, non protein bound iron and hypoxanthine), both measured in umbilical cord blood. Secondary outcome measures are neonatal mortality, serious composite neonatal morbidity and long-term neurological outcome. Furthermore pharmacokinetics and pharmacodynamics will be investigated.We expect an inclusion of 220 patients (110 per group) to be feasible in an inclusion period of two years. Given a suspected mean value of S100B of 1.05 ug/L (SD 0.37 ug/L) in the placebo group this trial has a power of 90% (alpha 0.05) to detect a mean value of S100B of 0.89 ug/L (SD 0.37 ug/L) in the 'allopurinol-treated' group (z-test2-sided). Analysis will be by intention to treat and it allows for one interim analysis.

DISCUSSION

In this trial we aim to answer the question whether antenatal allopurinol administration reduces hypoxic-ischaemic encephalopathy in neonates exposed to foetal hypoxia.

TRIAL REGISTRATION NUMBER

Clinical Trials, protocol registration system: NCT00189007.

Furosemide in preterm infants treated with indomethacin for patent ductus arteriosus

OBJECTIVE

To evaluate the effect of furosemide on renal function and water balance in preterm infants treated with indomethacin (3 x 0.2 mg/kg at 12-h intervals) for symptomatic patent ductus arteriosus.

PATIENTS AND METHODS

We performed a retrospective multi-centre double cohort study in preterm infants <32 weeks of gestational age. Thirty-two infants treated with furosemide (1 mg/kg i.v.) before each indomethacin dose (furosemide group) were matched with 32 infants with indomethacin treatment alone (control-group). Renal effects (urine output, weight gain, serum creatinine, sodium concentration) were registered.

RESULTS

The study groups were comparable for gestational age, birth weight and day of therapy. Pretreatment differences were observed for urine output, weight and serum sodium. However, no differences were noticed in day-to-day urine output change or weight gain between the groups. A significant increase in serum creatinine concentration (50% vs. control, 18%; p < 0.05) and a concomitant significant decrease in serum sodium (-9 vs. control, -3 mmoL/L; p < 0.05) in the furosemide group was observed 72-96 h after starting therapy.

CONCLUSION

Furosemide before each indomethacin dose resulted in a significant increase in serum creatinine and hyponatremia, without increasing urine output.

Feasibility of noninvasive continuous finger arterial blood pressure measurements in very young children, aged 0-4 years

Our goal was to study the feasibility of continuous noninvasive finger blood pressure (BP) monitoring in very young children, aged 0-4 y. To achieve this, we designed a set of small-sized finger cuffs based on the assessment of finger circumference. Finger arterial BP measured by a volume clamp device (Finapres technology) was compared with simultaneously measured intra-arterial BP in 15 very young children (median age, 5 mo; range, 0-48), admitted to the intensive care unit for vital monitoring. The finger cuff-derived BP waveforms showed good resemblance with the invasive arterial waveforms (mean root-mean-square error, 3 mm Hg). The correlation coefficient between both methods was 0.79 +/- 0.19 systolic and 0.74 +/- 0.24 diastolic. The correlation coefficient of beat-to-beat changes between both methods was 0.82 +/- 0.18 and 0.75 +/- 0.21, respectively. Three measurements were related to measurement errors (loose cuff application; wrong set-point). Excluding these erroneous measurements resulted in clinically acceptable measurement bias (-3.8 mm Hg) and 95% limits of agreement (-10.4 to + 2.8 mm Hg) of mean BP values. We conclude that continuous finger BP measurement is feasible in very young children. However, cuff application is critical, and the current set-point algorithm needs to be revised in very young children.

Early neonatal dexamethasone treatment for prevention of bronchopulmonary dysplasia. Randomised trial and meta-analysis evaluating the duration of dexamethasone therapy

The aim of the aborted trial was to determine whether the short early dexamethasone (DX) given after the birth improves the early outcome. We also reviewed the evidence (meta-analysis) to determine whether the duration of early DX treatment influences the early outcome, particularly in terms of bronchopulmonary dysplasia (BPD). The participants of the randomised multicentre, double-blinded placebo-controlled trial had a birth weight 500-999 g, gestation < or = 31.0 weeks, and respiratory failure by the age of 4 h. The infants received either four doses of DX (0.25 mg/kg at 12 h intervals) or placebo. The meta-analysis was performed to determine the beneficial and adverse effects of early short (<96 h duration) versus early prolonged (>96 h) DX treatment. The trial was discontinued after 109 infants had been enrolled. There was a non-significant improvement in the outcome (survival without BPD, severe intracranial haemorrhage or periventricular leukomalacia; RR 1.27; 95% CI 0.87-1.85). The risks for gastrointestinal perforation and hyperglycaemia tended to increase. A total of 15 trials were included in the meta-analysis: 10 involved prolonged (i.e. >96 h; 1594 infants) and five short interventions (1069 infants). Early prolonged DX decreased the RR for BPD to 0.72 (95% CI 0.61-0.87), whereas early short DX course did not significantly decrease the risk (RR 0.82; 95% CI 0.64-1.05). Gastrointestinal haemorrhages and perforations were significantly increased only in the early prolonged DX group.

CONCLUSION

The dosage and duration of early corticosteroid given to small premature infants influences the risk of the side-effects and the early outcome.

Baroreceptor reflex sensitivity in human neonates: the effect of postmenstrual age

We performed a cross-sectional study in human infants to determine if indices of R-R interval variability, systolic blood pressure (SBP) variability, and baroreceptor reflex sensitivity change with postmenstrual age (PMA: gestational age+postnatal age). The electrocardiogram, arterial SBP and respiration were recorded in clinically stable infants (PMA, 28-42 weeks) in the quiet sleep state in the first days after birth. (Cross-)spectral analyses of R-R interval series and SBP series were performed to calculate the power of low-frequency (LF, indicating baroreceptor reflex activity, 0.04-0.15 Hz) and high-frequency (HF, indicating parasympathetic activity, individualized between the p-10 and p-90 values of respiratory frequency) fluctuations, and transfer function phase and gain. The mean R-R interval, and LF and HF spectral powers of R-R interval series increased with PMA. The mean SBP increased with PMA, but not the LF and HF spectral powers of SBP series. In the LF range, cross-spectral analysis showed high coherence values (>0.5) with a consistent negative phase shift between R-R interval and SBP, indicating a approximately 3 s lag in R-R interval changes in relation to SBP. Baroreceptor reflex sensitivity, calculated from LF transfer gain, increased significantly with PMA, from 5 (preterm) to 15 ms mmHg-1 (term). Baroreceptor reflex sensitivity correlated significantly with the (LF and) HF spectral powers of R-R interval series, but not with the LF and HF spectral powers of SBP series. The principal conclusions are that baroreceptor reflex sensitivity and spectral power in R-R interval series increase in parallel with PMA, suggesting a progressive vagal maturation with PMA.

Activation of the Inflammatory Reaction within Minutes after Birth in Ventilated Preterm Lambs with Neonatal Respiratory Distress Syndrome

To study the activation of the inflammatory reaction within minutes after birth, we measured parameters of inflammation before and immediately after birth. To assess whether respiratory distress syndrome (RDS) or birth itself initiates activation, we compared preterm ventilated lambs with term nonventilated lambs. Preterm lambs were delivered by cesarean section at 132 days gestational age (term 145 days) and were ventilated by conventional ventilation (n = 9). Before clamping the cord, 5, 10 and 15 min after birth, blood was sampled from umbilical catheters. Term lambs (n = 9) were born spontaneously after 140-145 days gestational age. Immediately after birth, a venous umbilical catheter was inserted. Blood was sampled before the first breath and 5, 10, 15 and 20 min after birth while the lamb was breathing spontaneously. Blood was analyzed for AP50 (complement activation), number of polymorphonuclear leukocytes (PMNs) and beta-glucuronidase (released from activated PMNs). In preterm lambs, we found a decreased number of PMNs and increased levels of beta-glucuronidase already at 5 min after birth. In the term lambs, we found only a short-term mild decrease in PMNs and short-term increase in beta-glucuronidase. We conclude that systemic activation of the inflammatory reaction can be found in ventilated preterm lambs with RDS within 5 min after birth. This very early activation is mild, transient and less pronounced in term-born spontaneously breathing lambs compared with preterm, ventilated lambs with RDS.

SP-A-enriched surfactant for treatment of rat lung transplants with SP-A deficiency after storage and reperfusion

BACKGROUND

The function of pulmonary surfactant is affected by lung transplantation, contributing to impaired lung transplant function. A decreased amount of surfactant protein-A (SP-A) after reperfusion is believed to contribute to the impaired surfactant function. Surfactant treatment has been shown to improve lung transplant function, but the effect is variable. We investigated whether SP-A enrichment of surfactant improved the efficacy of surfactant treatment in lung transplantation.

METHODS

Left and right lungs of Lewis rats, inflated with 50% O2, were stored for 20 hr at 8 degrees C. Surfactant in bronchoalveolar lavage fluid from right lungs was investigated after storage (n=6). Left lungs were transplanted into syngeneic recipients and treated with SP-A-deficient surfactant (n=6) or SP-A-enriched surfactant (n=6) just before reperfusion. Air was instilled into untreated lung transplants (n=6). Sham operated (n=4) and normal (n=8) animals served as controls. Lung function was measured during 1 hr of reperfusion; surfactant components in bronchoalveolar lavage fluid were measured after reperfusion.

RESULTS

After storage the amount of SP-A decreased by 27%, whereas surfactant phospholipids changed minimally. After reperfusion a further decrease of SP-A was paralleled by profound changes in surfactant phospholipids. Lung transplant function, however, remained relatively good. After instillation of SP-A-enriched surfactant, PO2 values were reached that approximated sham control PO2 values, whereas after SP-A-deficient surfactant treatment, the PO2 values did not improve.

CONCLUSION

Enrichment of surfactant with SP-A for treatment of lung transplants improves the efficacy of surfactant treatment.

Early activation of inflammation and clotting in the preterm lamb with neonatal RDS: comparison of conventional ventilation and high frequency oscillatory ventilation

In neonatal respiratory distress syndrome activation of inflammation and clotting is demonstrated. High frequency oscillatory ventilation (HFOV) is considered to be less damaging to the human preterm lung, resulting in less activation of inflammation and clotting compared with conventional ventilation (CV). To assess the sequence of events of activation of inflammation and clotting and to compare the impact of HFOV to CV, we ventilated preterm lambs delivered by cesarean section at 132 d gestational age (term 145 d) for 8 h by CV (n = 10) or HFOV (n = 11). Fifteen minutes after birth and at 2-h intervals thereafter blood samples, from umbilical catheters, were analyzed for AP50 (complement activation), number of polymorphonuclear leukocytes, beta-glucuronidase, platelet function, activated partial thromboplastin time, thrombin time and thrombin inhibition, and bronchoalveolar lavage fluid was analyzed for elastase, thrombin and protein. We found complement activation, low number of polymorphonuclear leukocytes and high levels of beta-glucuronidase already at 15 min after birth. Within 2 to 4 h after birth platelet function deteriorated, activated partial thromboplastin time prolonged, and thrombin inhibition decreased. Activation of inflammation and clotting in the lungs was demonstrated by increased levels of elastase and thrombin in bronchoalveolar lavage fluid. In the HFOV group, AP50 remained significantly higher than in the CV group, reflecting less complement activation, and platelet function analysis remained significantly lower, reflecting better platelet function. We conclude that systemic activation of inflammation can be found in the ventilated preterm lamb with respiratory distress syndrome within 15 min after birth. Afterward, or due to activation of inflammation, clotting is activated. HFOV possibly attenuates activation of inflammation.

Increased tissue-type plasminogen activator antigen release is not accompanied by increased systemic fibrinolytic activity in severe neonatal respiratory distress syndrome

Intravascular and intraalveolar fibrin depositions in preterm infants with severe respiratory distress syndrome (RDS) have been attributed to activation of clotting. We questioned whether in the face of activated clotting, fibrinolysis is sufficient in these infants. We found, in infants with severe RDS within 6 to 12 h of birth, increased median thrombin-antithrombin III complex formation (11.1 versus 1.3 ng/mL in the group with mild-to-moderate RDS, p < 0.001), indicating activation of clotting. Simultaneously, we found increased tissue-type plasminogen activator antigen (t-PA) release in plasma of these infants represented by increased median t-PA plasma concentrations (8.3 versus 2.5 ng/mL in the group with mild-to-moderate RDS, p < 0.01). This increased t-PA release was not accompanied with more plasminogen and antiplasmin consumption and with more fibrin and fibrinogen degradation than in the infants with mild-to-moderate RDS because plasma plasminogen and antiplasmin activity and total fibrin and fibrinogen degradation product concentrations were similar in both groups. We have found that activated clotting and t-PA plasma concentrations are positively correlated with arterial-to-alveolar oxygen tension ratio and ventilator efficiency index values. Plasminogen and antiplasmin activity, and total fibrin and fibrinogen degradation product concentrations were not correlated with these continuous measures of RDS severity. In neonatal RDS, clotting activity contributes to disease severity. Insufficient fibrinolysis likely facilitates the deleterious effects of activated clotting.

A comparison of the hemodynamic and respiratory effects of surfactant instillation during interrupted ventilation versus noninterrupted ventilation in rabbits with severe respiratory failure

The purpose of this study was to evaluate whether avoiding interruption of ventilation during surfactant instillation improves the effects on lung function and surfactant distribution and whether it prevents the adverse effects on blood pressure and cerebral blood flow. The study was performed using rabbits with severe respiratory failure induced by lung lavages. These rabbits were randomized to 99mTc-Nanocoll labeled surfactant instillation through a side lumen of the endotracheal tube without interrupting ventilation or instillation during a short interruption of ventilation. After surfactant instillation with interruption of ventilation, PaO2 rose from 8.7+/-1.3 to 24.9+/-6.4 kPa (mean+/-SEM). Without interruption, PaO2 rose from 8.4+/-0.8 to 32.4+/-4.3 kPa. PaCO2 decreased with interruption from 4.69+/-0.51 to 3.61+/-0.26 kPa and without interruption from 5.06+/-0.41 to 4.13+/-0.23 kPa. Dynamic and static compliance indices were not statistically different after both procedures. Surfactant distribution tended to be less nonuniform after instillation without interrupting ventilation. In contrast, avoidance of interruption of ventilation resulted in less uniform lobar distribution and less peripheral deposition of surfactant. By instillation with interruption, blood pressure increased quickly (28+/-6.6%), followed by a 22+/-5.3% decrease. Blood pressure increased quickly (16+/-4.2%), followed by a 40+/-10% decrease by surfactant instillation without interruption. Cerebral blood flow, measured by an ultrasonic transit time flow probe on the carotid artery, increased quickly (45+/-14%), followed by a 64+/-11% decrease with interruption, whereas it increased 15+/-4.9% (p = 0.06 versus with interruption) and decreased 61+/-13% without interruption of ventilation. Therefore, avoiding interruption of ventilation during surfactant instillation tends to prevent the potential adverse effects of a rapid rise in cerebral blood flow, and furthermore, tends to improve uniformity of surfactant distribution, whereas having no detrimental effect on respiratory function.

Surfactant nebulization versus instillation during high frequency ventilation in surfactant-deficient rabbits

Surfactant nebulization improves lung function at low alveolar doses of surfactant. However, efficiency of nebulization is low, and lung deposition seems to depend on lung aeration. High frequency ventilation (HFV) has been shown to improve lung aeration. We hypothesize that the combination of HFV and surfactant nebulization may benefit lung deposition of surfactant and consequently, lung function. The aim of this study was to compare the effect of surfactant nebulization versus instillation during HFV on lung function, surfactant distribution, and cerebral blood flow. Therefore, severe respiratory failure was induced by lung lavages in 18 rabbits. HFV was applied: frequency = 8 Hz, mean airway pressure = 12 cm H2O, amplitude = 100%, fraction of inspired O2 = 1.0. Technetium-99m-labeled surfactant (Alveofact, 100 mg/kg of BW) was nebulized or instilled (n = 6 each). Six other rabbits did not receive surfactant (control, HFV only). We found that after instillation partial arterial O2 tension increased from 7.0 kPa (95% confidence interval, 6.3-8.0 kPa) to 34 kPa (16-51 kPa), and during nebulization from 7.0 kPa (6.0-9.0 kPa) to 46 kPa (27-58 kPa). Partial arterial CO2 tension decreased after instillation from 6.1 kPa (5.3-7.1 kPa) to 4.8 kPa (3.9-5.6 kPa), and during nebulization, after an initial rise, it decreased from 6.3 kPa (5.3-7.4 kPa) to 4.9 kPa (4.4-5.6 kPa). Both treatments resulted in nonuniform distribution. Surfactant deposition after nebulization was 9.8%. Instillation resulted in a drop of mean arterial blood pressure of 17% (8-31%), and an even more pronounced drop in cerebral blood flow of 39% (18-57%). Nebulization did not affect blood pressure. Cerebral blood flow decreased with a maximum of 27% (10-37%). We conclude that surfactant nebulization during HFV improves lung function in rabbits with severe respiratory failure, without improving distribution, but with less effects on blood pressure and cerebral blood flow, when compared with surfactant instillation.

Reduction in adverse effects of mechanical ventilation in rabbits with acute respiratory failure by treatment with extracorporeal CO2 removal and a large fluid volume of diluted surfactant

The long-term outcome of infants with severe respiratory distress syndrome can be improved by optimizing surfactant therapy and minimizing the risk for pulmonary barovolutrauma and oxygen toxicity. The authors hypothesized that this may be achieved with low frequency ventilation and extracorporeal CO2 removal (LFV-ECCO2R), in combination with intratracheal instillation of a large fluid volume with diluted surfactant. Lung lavaged rabbits were initially ventilated with continuous positive pressure ventilation. The rabbits were randomized to treatment with LFV-ECCO2R and surfactant (experimental group), or surfactant only (control group). In the experimental group, the rabbits were treated with a large volume (16 ml/kg) of diluted surfactant (6.25 mg/ml) at a dose of 100 mg/kg body weight. After surfactant therapy, the FiO2 100% was gradually decreased. During 4 hours, the extracorporeal bloodflow was adjusted to maintain the PaCO2 between 4.0-6.0 kPa. Thereafter, the rabbits were allowed to breathe spontaneously with 2.5 cm H2O continuous positive airway pressure ventilation (CPAP) and 40% oxygen. In the control group, the rabbits received the same surfactant therapy. During the study period, the rabbits remained ventilated with an inspiratory oxygen concentration (FiO2) of 100% for 4 hours. The ventilator flow was adjusted to maintain the PaCO2 between 4.0 and 6.0 kPa. Thereafter, positive-end expiratory pressure was decreased to 2.5 cm H2O and FiO2 was gradually decreased to 40%. In the experimental group, FiO2 was decreased to 40% in a stepwise fashion whereby the PaO2 could be maintained easily within the normal range. Extracorporeal flow rates during perfusion ranged from 20-35 ml/kg/min and were sufficient to keep the PaCO2 and pH within normal limits. After 4 hours, the rabbits could breathe spontaneously with CPAP and 40% oxygen, while normal blood gas values were maintained. All rabbits survived the experiment. In the control group, all rabbits experienced severe hypoxemia, despite FiO2 of 100% oxygen and, during the course of weaning, all rabbits died because of hypoxia. In conclusion, the present study demonstrated that barovolutrauma due to mechanical ventilation, and oxygen toxicity due to high FiO2, can be minimized in an animal model of acute respiratory failure by the combination of LFV-ECCO2R and surfactant therapy.

Effects of early surfactant treatment persisting for one week after lung transplantation in rats

We investigated whether pulmonary surfactant in rat lung transplants recovered during the first week post-transplantation, along with symptoms of the reimplantation response, and whether this recovery was affected by early surfactant treatment. The severity of pulmonary injury was varied by transplanting left lungs with 6-h and 20-h ischemia (n = 12 and 19, respectively). Half of the transplants were treated by instillation of surfactant before reperfusion. Lungs from sham operated, and normal rats (n = 4 and 5, respectively) served as controls. The pulmonary injury severely impaired lung transplant function; 10 of the worst affected animals died. After 1 wk, symptoms of reimplantation response and properties of pulmonary surfactant were assessed. If untreated, the reimplantation response had almost resolved in the 6-h but not in the 20-h ischemia group; pulmonary surfactant, however, continued to be deficient in both ischemia groups (low amounts of surfactant phospholipids and surfactant protein A [SP-A]). Surfactant treatment improved the recovery from injury in the 20-h ischemia group resulting in normal lung function and amounts of surfactant phospholipids. Amounts of SP-A were not improved by surfactant treatment. In conclusion, early surfactant treatment enhances recovery from transplantation injury and is persistently beneficial for pulmonary surfactant in lung transplants.

Number and activation of circulating polymorphonuclear leukocytes and platelets are associated with neonatal respiratory distress syndrome severity

OBJECTIVE

To determine whether number and activation of circulating polymorphonuclear leukocytes (PMNs) and platelets are associated with disease severity in neonatal respiratory distress syndrome (RDS).

DESIGN

Prospective study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

Preterm infants with severe (n = 18) or mild to moderate (n = 18) RDS who were consecutively admitted.

INTERVENTIONS

PMN and platelet counts and plasma concentrations of elastase-alpha1-proteinase inhibitor (E-alpha1-PI) and thromboxane B2 (TxB2) were recorded each day during the first 5 days of life. E-alpha1-PI-to-PMN and TxB2-to-platelet ratios were calculated to correct for the influence of the PMN and platelet count on elastase and thromboxane release.

RESULTS

From day 2, the severe RDS group had lower median PMN counts (1.5 vs 4.5 x 10/L), lower mean platelet counts (136 vs 230 x 10/L), and more elastase and thromboxane release, indicated by higher median E-alpha1-PI-to-PMN (39.2 vs 13.0 ng/10 PMNs on day 2) and TxB2-to-platelet (2.61 vs 0.52 pg/10 platelets on day 3) ratios than the mild-to-moderate group. Lower PMN and platelet counts and higher elastase and thromboxane release were correlated with birth asphyxia (lower 5-minute Apgar scores and umbilical arterial PH values), higher respiratory requirements (fraction of inspired oxygen and peak inspiratory pressure), and decreased values for continuous measures of RDS severity (ventilatory efficiency index and PaO2-to-alveolar oxygen tension ratio).

CONCLUSION

Decreased PMN and platelet counts and increased elastase and thromboxane release are correlated with increased RDS severity. Birth asphyxia (hypoxia and acidosis) and tissue injury caused by high-pressure ventilation and hyperoxia may promote this activation process.

Disease severity is correlated with plasma clotting and fibrinolytic and kinin-kallikrein activity in neonatal respiratory distress syndrome

This study was undertaken to determine whether simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein is associated with disease severity in preterm infants with neonatal respiratory distress syndrome (RDS), during the first 5 d of life. In the infants with severe RDS, we found activation of clotting, fibrinolysis, and kinin-kallikrein within 6-12 h of birth, indicated by increased thrombin-antithrombin III complex formation [22.5 ng/ml versus 1.4 ng/ml (median values) in the mild/moderate RDS infants, p < 0.001], increased tissue-type plasminogen activator plasma concentrations [5.1 ng/ml versus 2.6 ng/ml (median values) in the mild/moderate RDS infants, p < 0.01], and increased plasma kallikrein activity [198% versus 189% of maximal activated human plasma (median values) in the mild/ moderate infants, p < 0.01], respectively. Thrombin generation, tissue-type plasminogen activator release, and kallikrein activity did not change significantly in the severe RDS group throughout the study. In these infants, kallikrein activity was accompanied by lower values of plasma kallikrein inhibitory activity. Activation of clotting, fibrinolysis, and kinin-kallikrein was accompanied with a transient decrease of the neutrophil count and a steady decrease of the platelet count in the severe RDS group. The studied parameters of clotting and fibrinolytic and kinin-kallikrein activation were significantly correlated with continuous measures of RDS severity. We, therefore, suggest that this activation process likely contributes to respiratory insufficiency in neonatal RDS.

Leakage of protein into lungs of preterm ventilated rabbits is correlated with activation of clotting, complement, and polymorphonuclear leukocytes in plasma

We investigated whether leakage of protein in lungs of preterm ventilated rabbits of 28- and 29-d gestational age is correlated with activation of clotting, complement, and polymorphonuclear leukocytes (PMN) in plasma. We found signs of systemic activation of clotting, complement and PMN in ventilated 28-d gestational age rabbits, as indicated, respectively, by increased median plasma fibrin monomer concentrations (83 versus 40% of normal adult rabbit plasma in nonventilated 28-d gestational age rabbits, p < 0.01), decreased median plasma CH50 activity (112 versus 122 U/L in nonventilated 28-d gestational age rabbits, p < 0.05), and increased median plasma beta-glucuronidase concentrations (159 versus 97% of maximal activated adult rabbit plasma in nonventilated 28-d gestational age rabbits p < 0.05). We did not find signs of systemic activation in the ventilated 29-d gestational age group. Higher median total protein concentrations in alveolar wash of the ventilated 28-d gestational age rabbits (2.7 versus 1.3 mg/mL in the nonventilated rabbits. p < 0.01) indicated protein leakage into the lungs, and this protein leakage was more pronounced in the lungs of ventilated 28-d gestational age rabbits than in those of ventilated 29-d gestational age rabbits (2.1 mg/mL, p < 0.01). The total protein concentration in the alveolar wash of all 28-d gestational age rabbits was correlated with the concentration of fibrin monomers (p = 0.51, p = 0.035) and beta-glucuronidase (p = 0.61, p = 0.011), and the CH50 activity (p = -0.73, p = 0.002) in plasma. We conclude that leakage of protein in lungs of preterm ventilated rabbits of 28-d gestational age is correlated with activation of clotting, complement, and PMN in plasma. This activation process may contribute to lung injury by intravascular and intraalveolar deposition of fibrin and formation of proteinaceous edema.

Surfactant nebulization does not alter airflow obstruction and bronchial responsiveness to histamine in asthmatic children

To test the hypothesis that surfactant nebulization improves pulmonary function and reduces bronchial responsiveness to histamine, we studied 12 children with asthma. We measured before and after inhalation of 100 mg nebulized natural-derived bovine surfactant (Alveofact (registered)) and after nebulization of 0.9% NaCl the change in peak expiratory flow, vital VC, FEV1, and forced expiratory flows at 50 and 75% of the flow-volume curve. In addition, we performed a histamine inhalation challenge. We did not find any significant changes in these parameters after nebulization of surfactant. These findings indicate that the inhalation of nebulized surfactant does not alter airflow obstruction and does not alter bronchial responsiveness to histamine in asthmatic children with airflow obstruction.

Risk of otitis externa after swimming in recreational fresh water lakes containing Pseudomonas aeruginosa

OBJECTIVE

To determine whether an outbreak of otitis externa was due to bathing in recreational fresh water lakes and to establish whether the outbreak was caused by Pseudomonas aeruginosa in the water.

DESIGN

Matched case-control study.

SETTING

The Achterhoek area, the Netherlands.

SUBJECTS

98 cases with otitis externa and 149 controls matched for age, sex, and place of residence.

MAIN OUTCOME MEASURES

Odds ratios for type of swimming water and frequency of swimming; presence of P aeruginosa in ear swabs and fresh water lakes.

RESULTS

Otitis externa was strongly associated with swimming in recreational fresh water lakes in the previous two weeks (odds ratio 15.5 (95% confidence interval) 4.9 to 49.2) compared with non-swimming). The risk increased with the number of days of swimming, and subjects with recurrent ear disease had a greatly increased risk. The lakes met the Dutch bathing water standards and those set by the European Commission for faecal pollution in the summer of 1994, but P aeruginosa was isolated from all of them, as well as from the ear swabs of 78 (83%) of the cases and 3 (4%) of the controls.

CONCLUSIONS

Even when current bathing water standards are met, swimming can be associated with a substantial risk of otitis externa because of exposure to P aeruginosa. People with recurrent ear disease should take special care when swimming in waters containing P aeruginosa.

Distribution of a second dose of exogenous surfactant in rabbits with severe respiratory failure

Newborn infants with respiratory distress who fail to respond to surfactant treatment receive a second dose of surfactant. The effect of this strategy on the distribution of surfactant to the lung is unknown. We therefore investigated the distribution of the first (100 mg/kg body weight) and second dose (50 mg/kg body weight) of surfactant (Alveofact) in lung-lavaged rabbits (n = 6). We used 141Ce- and 103Rn-labeled microspheres that were mixed with the first and second dose of surfactant, respectively. Arterial PO2 increased from 5.7 +/- 1.1 to 10.6 +/- 2.0 kPa (p < 0.05) (mean +/- SD) after the first and from 20.1 +/- 3.8 to 30.1 +/- 2.5 kPa (p < 0.05) after the second dose. Thereafter the rabbits were killed, and the lungs were cut into 200 pieces. The radioactivity of Ce and Rn microspheres was measured and distribution histograms were obtained. Histograms of the first, second, and the total dose of surfactant showed similar nonuniform distribution. Correlation coefficients of the Ce and Rn radioactivity in the different lung lobes widely ranged per lung lobe per rabbit. In addition, the percentage of the number of lung pieces that received an amount of surfactant that was less than the calculated endogenous surfactant pool decreased from 12.5 +/- 3.2% to 8.5 +/- 3.0% (p < 0.05) after the first and second dose, respectively. This indicates that the second dose was directed both to areas that initially received surfactant and to areas that were still surfactant-deficient. The surfactant-deficient areas were aerated after this second dose, resulting in a further rise in PO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Atypical cellulitis due to group B streptococcus

In a minority of late-onset Group B streptococcal (GBS) cases in neonates, facial or buccal cellulitis has been described. We report a case of sepsis with GBS, in which an atypical cellulitis in the inguinal area was seen as presenting symptom.

Activation of the plasma clotting, fibrinolytic, and kinin-kallikrein system in preterm infants with severe idiopathic respiratory distress syndrome

We studied the activation pattern of clotting, fibrinolysis, and kinin-kallikrein during the first 5 d of life in 10 preterm infants with signs of severe idiopathic respiratory distress syndrome (IRDS) after birth (IRDS group) and in 12 healthy preterm infants (reference group). We found systemic activation of clotting, fibrinolysis, and kinin-kallikrein in the IRDS infants within 12 to 24 h of birth, represented by increased median thrombin-antithrombin III complex formation (90 ng/mL versus 10 ng/mL in the reference group, p < 0.05), increased mean tissue-type plasminogen activator plasma concentrations (11.8 ng/mL versus 3.5 ng/mL in the reference group, p < 0.05), and increased mean plasma kallikrein activity (182.6% versus 162.0% of maximal activated human plasma in the reference group, p < 0.05), respectively. Clotting activation was accompanied by a significant decrease of the platelet count. Clotting and fibrinolytic activity decreased in the IRDS group during the first 2 to 3 d of life. Kinin-kallikrein activation was accompanied by decreased plasma kallikrein inhibitor activity values and did not change throughout the study period. Plasma factor XII activity was not significantly increased in the IRDS infants during the first 2 d of life but did significantly increase thereafter. The cause of simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein in our IRDS infants has not yet been clarified. However, this activation process may contribute to lung injury such as that described in the adult respiratory distress syndrome.

The function of surfactant is impaired during the reimplantation response in rat lung transplants

In this study we investigated the surfactant function in rat lung transplants at the peak of the reimplantation response in experimental groups with increasing warm ischemic times of the lung transplant. The left and right lungs in five groups of rats were assessed 24 hours after left lung transplantation: rats receiving transplants with lung graft ischemic times of 60 (n = 4), 90 (n = 5), and 120 (n = 5) minutes, donor rats with 120 minutes lung ischemia (n = 5) and normal (nonoperated) rats (n = 6). The reimplantation response was assessed by the ventilation score on chest roentgenograms, measurement of the static lung compliance, and the (serum) protein concentration in the bronchoalveolar lavage fluid. Surfactant in the bronchoalveolar lavage fluid was assessed by measuring the amount and the composition of surfactant phospholipids and the in vitro surfactant function in a pulsating bubble surfactometer. We found that longer ischemic times caused a more severe reimplantation response in the left lung grafts. Although the ventilation scores were equally low in the 60-, 90-, and 120-minute ischemia groups, the lung compliances decreased and the (serum) protein concentrations increased stepwise in correlation with longer ischemic times. The amount of surfactant phospholipids during the reimplantation response was not changed, but the percentage phosphatidyl choline decreased progressively in parallel with the severity of the reimplantation response. Finally, the in vitro function of surfactant from the lung transplants decreased in parallel with the prolongation of the ischemic time, whereas the function of surfactant from donor lungs with 120 minutes of ischemia and from native right lungs was not changed. We conclude that the surfactant function is impaired during the reimplantation response as a result of a high concentration of inhibiting serum proteins and a low percentage of phosphatidyl choline.

Large volume instillation of surfactant during extracorporeal life support improves lung function in lung lavaged rabbits

The sometimes limited effect of surfactant therapy in neonates might be explained in part by an non homogeneous distribution of the surfactant after endotracheal instillation. This distribution can be improved significantly by increasing the fluid volume. The aim of this study was to evaluate the effect of two methods for gas exchange during a large volume instillation of surfactant on the outcome of this treatment in lung lavaged rabbits. In the control group (n = 6) gas exchange was maintained with continuous positive pressure ventilation (CV), whereas in the other group gas exchange was established with extracorporeal life support (ECLS) (n = 6) and intermittent sighs. Five hours after surfactant administration, an identical weaning procedure was started in both groups. The authors found significantly higher PaO2 values in the ECLS group than in the control group in the normocarbia state. All animals in the ECLS group could be weaned to room air maintaining normal blood gases, whereas all the animals in the control group died in the course of weaning. The ventilator efficiency index was significantly higher during the weaning period in the ECLS group, indicating better lung function, than in the control group. The authors conclude that a large volume instillation of surfactant is feasible by applying ECLS and intermittent sighs. Additional studies are needed to elucidate if this combined treatment will be an improvement over current surfactant therapy.

Fatal ureaplasmal pneumonia and sepsis in a newborn infant

Ureaplasma urealyticum was isolated in pure culture from blood tracheal aspirate and lung tissue in a newborn infant, who died of a severe pneumonia within 48 h after birth. The clinical course was characterized by persistent pulmonary hypertension of the newborn (PPHN). Post-mortem examination revealed extensive hyaline membrane formation combined with signs of inflammation in both lungs. The clinical and histopathological picture resembled that of early onset group B haemolytic streptococcal pneumonia/sepsis.

Distribution of endotracheally instilled surfactant protein SP-C in lung-lavaged rabbits

In lung-lavaged surfactant-deficient rabbits (n = 6) requiring artificial ventilation, porcine surfactant was instilled endotracheally. This resulted in improvement of lung function so that the animals could be weaned off artificial ventilation. The animals were killed 4 1/2 h after surfactant administration and the porcine surfactant protein was localized in the lung with a MAb. We found surfactant protein in all lobes of the lung but the distribution was not homogeneous. Surfactant protein C was found in less than 15% of the alveolar spaces and in less than 1% of the bronchi.

Dose response of thyrotropin-releasing hormone on pulmonary maturation in corticosteroid-treated preterm rabbits

The dose-response effect of thyrotropin-releasing hormone in enhancing pulmonary maturation was investigated with six dosing regimens. Pregnant does received thyrotropin-releasing hormone (5, 10, or 50 micrograms/kg every 12 hours for four doses or one dose of 20 micrograms/kg) in conjunction with betamethasone beginning on day 25 of gestation, with betamethasone alone or saline solution used as comparison treatment groups. Half of the newborn rabbits received supplemental surfactant therapy after delivery on day 27, and all were ventilated on a ventilator plethysmography system for 30 minutes. There were no differences among the four thyrotropin-releasing hormone doses in surfactant pool sizes, compliances, or proteins leak into or out of the air spaces. The groups that received multiple doses of thyrotropin-releasing hormone had significantly higher perinatal loss rates than the single-dose group. The lungs of the group treated with thyrotropin-releasing hormone plus steroid and the rabbits treated only with steroid were more compliant than the controls without surfactant therapy, and showed significant improvements in protein leak. The addition of thyrotropin-releasing hormone to betamethasone improved several of the protein leak measurements compared with use of betamethasone alone. These results question the necessity of multiple doses of thyrotropin-releasing hormone to induce pulmonary maturation, especially when the higher perinatal mortality and the theoretical long-term effects of fetal hyperthyroidism on thyroid axis function are considered.

Surfactant treatments alter endogenous surfactant metabolism in rabbit lungs

The effect of exogenous surfactant on endogenous surfactant metabolism was evaluated using a single-lobe treatment strategy to compare effects of treated with untreated lung within the same rabbit. Natural rabbit surfactant, Survanta, or 0.45% NaCl was injected into the left main stem bronchus by use of a Swan-Ganz catheter. Radio-labeled palmitic acid was then given by intravascular injection at two times after surfactant treatment, and the ratios of label incorporation and secretion in the left lower lobe to label incorporation and secretion in the right lung were compared. The treatment procedure resulted in a reasonably uniform surfactant distribution and did not disrupt lobar pulmonary blood flow. Natural rabbit surfactant increased incorporation of palmitate into saturated phosphatidylcholine (Sat PC) approximately 2-fold (P less than 0.01), and secretion of labeled Sat PC increased approximately 2.5-fold in the surfactant-treated left lower lobe relative to the right lung (P less than 0.01). Although Survanta did not alter incorporation, it did increase secretion but not to the same extent as rabbit surfactant (P less than 0.01). Alteration of endogenous surfactant Sat PC metabolism in vivo by surfactant treatments was different from that which would have been predicted by previous in vitro studies.

Surfactant replacement therapy in surfactant-deficient rabbits: early effects on lung function and biochemical aspects

Lung-surfactant-deficient rabbits (n = 6) requiring artificial ventilation were subjected to a weaning-off regimen following surfactant replacement therapy. Surfactant-deficient rabbits (n = 6) that did not receive surfactant but underwent the same procedure served as controls. All surfactant-treated rabbits survived (i.e., reestablished spontaneous air breathing) whereas all the control animals died. In the surfactant-treated animals lung function improved in such a way that during the weaning period PaCO2 did not increase and the level of PaO2 remained significantly higher than in the control animals. The static lung compliance and the stability and expansion indices in vitro were significantly higher in the surfactant-treated rabbits. The lamellar body fraction of the lungs of surfactant-treated animals contained a significantly higher amount of surfactant phospholipids than those of the control animals. It is concluded that the animal model used in this study is an excellent tool for testing early effects of different surfactant preparations.

Transcutaneous respiratory electromyographic monitoring

The integrated diaphragm electromyogram (EMG) signal reflects function from the inspiratory centers to the neuromuscular junction. The feasibility and potential value of transcutaneous diaphragm electromyography (tcEMG) was confirmed in a group of infants using two prototype respiratory EMG monitors. Infants were monitored continuously for periods ranging from hours to days. One hundred were monitored for clinical reasons, looking for disordered respiratory behavior, while 47 were studied for technical/experimental reasons. Reliable measurements of diaphragm EMG activity were obtained, provided fully shielded electrode cables were used. Measurements in 28 ventilated infants and one adult confirmed that, unlike impedance and other non-electrophysiologic measures, tcEMG monitoring is not contaminated by ventilator-induced respiratory movements. The potential value of tcEMG monitoring in ventilated subjects is exemplified by illustrations of: diaphragmatic inactivity from phrenic nerve injury, inadequate central drive, and neuromuscular block; augmented expiratory muscle activity; and progressive increase in inspiratory diaphragmatic activity in the presence of a tension pneumothorax. TcEMG monitoring should prove a worthwhile addition to the available noninvasive respiratory monitoring techniques.

Transcutaneous PO2 and PCO2 during surfactant therapy in newborn infants with idiopathic respiratory distress syndrome

We conclude that surfactant treatment in newborn infants with IRDS results in decrease in TcPO2 and an increase in TcPO2 within minutes. The surfactant treatment procedure used in this study was not associated with hypoxemia. During surfactant treatment monitoring of TcPO2 and TcPCO2 is absolutely necessary.