Retinopathy of Prematurity: Therapeutic Strategies Based on Pathophysiology

Retinopathy of prematurity (ROP) continues to be a major preventable cause of blindness and visual handicaps globally. With improved perinatal care, improved survival of moderately preterm infants, and limited resources for oxygen delivery and monitoring, more mature preterm infants are developing severe ROP in developing countries. The pathophysiology of ROP is characterized by two phases. Phase I ROP is due to vaso-obliteration beginning immediately after birth secondary to a marked decrease in vascular endothelial growth factor (VEGF) and insulin-like growth factor-1 (IGF-1). Phase II begins around 33 weeks' postmenstrual age (PMA). During this phase, VEGF levels increase, especially if there is retinal hypoxia with increasing retinal metabolism and demand for oxygen leading to abnormal vasoproliferation. Since the original description of ROP in 1942 by Terry et al. [Am J Ophthalmol 1942;25:203-204], four epidemics of ROP have been observed. Prevention or early treatment of ROP involves careful titration of oxygen saturation by pulse oximeter (SpO2). Optimal SpO2 target remains elusive. Most of the large trials have focused on either a low SpO2 (85-89%) or a high SpO2 (91-95%) from the first day of birth to 36 weeks' PMA. Although the incidence of severe ROP and bronchopulmonary dysplasia decreased significantly, predischarge mortality was higher in these studies. Use of graded SpO2 during the 2 different phases of ROP (early, low SpO2 during phase I vs. late, high SpO2 during phase II) may be the best approach to prevent this disabling condition. Further trials should focus on this strategy. Other biological agents that are currently being studied include IGF-1 with IGF-binding protein-3 (rhIGF-1 + rhIGFBP-3) and propranolol. For advanced stages of ROP, laser ablation of avascular retina, early treatment of ROP (ETROP) protocol, intravitreal injection of anti-VEGF antibodies (e.g. bevacizumab) and vitrectomy are used to protect central vision and prevent retinal detachment. Long-term complications such as refractory errors, recurrence of ROP and risk of retinal detachment require continued follow-up with an ophthalmologist through adolescence and beyond. Optimal nutrition including adequate intake of omega-3 polyunsaturated fatty acids and decreasing infection/inflammation to promote normal vascularization are important strategies. Screening guidelines for ROP based on local incidence of ROP in different regions of the world are very important. Oxygen therapy is clearly a modifiable risk factor to decrease ROP that needs further study. Understanding the two phases of ROP will help to identify appropriate therapeutic strategies and improve visual outcomes in many preterm infants globally.

Neonatal Outcomes by Mode of Delivery in Preterm Birth

OBJECTIVE

We set out to test the hypothesis that infants born vaginally at ≤ 30 weeks gestation have less respiratory distress syndrome (RDS) than those born by cesarean delivery.

STUDY DESIGN

We conducted a retrospective cohort study of 652 infants born between 24 and 30 (6/7) weeks gestation from March 31, 1996 to May 31, 2014. Comparisons of neonatal outcomes by intended and actual mode of delivery were made using chi-square and t-tests (α = 0.05). Multiple logistic regression was performed to control for confounding variables.

RESULTS

Neonates born by cesarean delivery were more likely to have RDS (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.10-2.90), require intubation (OR, 1.80; 95% CI, 1.12-2.88), and have longer neonatal intensive care unit stay (70.0 ± 37.1 vs. 57.3 ± 40.1 days, p = 0.02).

CONCLUSION

Compared with cesarean delivery, vaginal delivery is associated with a significant reduction in RDS among infants born at ≤ 30 weeks gestation.

Assessment of hot flushes and vaginal dryness among obese women undergoing bariatric surgery

OBJECTIVE

Menopausal symptoms are associated with a negative impact on the quality of life, leading women to seek medical treatment. Obesity has been linked to higher levels of menopausal symptoms such as hot flushes. This assessment will explore whether the prevalence and bother of hot flushes and vaginal dryness change from pre- to post-bariatric surgery among obese midlife women.

METHODS

This study is a longitudinal analysis of data from 69 women (ages 35-72 years) undergoing bariatric surgery with reported reproductive histories and menopausal symptoms at preoperative and 6-month postoperative visits. Prevalence of and degree of bother of hot flushes and vaginal dryness at pre- and post-surgery were compared using McNemar's test and Wilcoxon signed-rank test.

RESULTS

The reported degree of bother of symptoms associated with hot flushes decreased from pre- to post-surgery (p < 0.01). There was no significant change in the prevalence of hot flushes or vaginal dryness in the overall study sample.

CONCLUSIONS

The degree of bother of symptoms associated with hot flushes among midlife women may decrease after bariatric surgery. These results highlight important secondary gains, including less bothersome menopausal symptoms, for women who choose bariatric surgery for weight loss.

Effect of Mucosal Cytokine Administration on Selective Expansion of Vaginal Dendritic Cells to Support Nanoparticle Transport

PROBLEM

The capacity of antigen-carrying vaccine nanoparticles (NPs) administered vaginally to stimulate local immune responses may be limited by the relatively low numbers of antigen-presenting cells (APCs) in the genital mucosa. Because inflammation is associated with increased susceptibility to sexually transmitted infections, we sought to increase APC numbers without causing inflammation.

METHOD OF STUDY

In this study, we evaluated intravaginal delivery of chemokines, growth factors, or synthetic adjuvants to expand APCs in reproductive tissues.

RESULTS

We found that granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulated expansion of CD11b+ dendritic cells (DCs) within 24 hr of intravaginal administration, with no effect on Langerhans cells or macrophages. Expansion of the CD11b+ DC population was not associated with increased inflammatory cytokine production, and these cells retained phagocytic function.

CONCLUSION

Our data suggest that non-inflammatory expansion of mucosal APCs by intravaginal GM-CSF could be used as an adjuvanting strategy to potentiate the genital immune response to nanoparticulate mucosal vaccines.

Urinary tract infections in a neonatal intensive care unit

OBJECTIVE

Our aim was to describe laboratory findings and imaging results for neonatal patients diagnosed with urinary tract infection (UTI).

STUDY DESIGN

Medical records were reviewed for infants diagnosed with UTI in a single neonatal intensive care unit (NICU) over a 13-year period.

RESULTS

Of the 8,241 patients admitted to the NICU during the study period, 137 infants were diagnosed with UTI. Imaging was reviewed for 101 patients. Renal pelvis dilation was found in 34% of patients and vesicoureteral reflux was found in 21%. Renal pelvis dilation was not associated with reflux (OR: 0.53 [95% CI: 0.18-1.5]). The sensitivity of urinalysis to detect a positive culture was 76%, and the specificity was 41%. Tests of cure for bacterial infections were uniformly negative.

CONCLUSION

Renal pelvis dilation was common but not associated with reflux among NICU patients diagnosed with UTI. Diagnostic criteria in this population are not well defined, and guidelines are needed for diagnosis and management of UTIs in NICU patients.

Reverse electron transport effects on NADH formation and metmyoglobin reduction

The objective was to determine if NADH generated via reverse electron flow in beef mitochondria can be used for electron transport-mediated reduction and metmyoglobin reductase pathways. Beef mitochondria were isolated from bovine hearts (n=5) and reacted with combinations of succinate, NAD, and mitochondrial inhibitors to measure oxygen consumption and NADH formation. Mitochondria and metmyoglobin were reacted with succinate, NAD, and mitochondrial inhibitors to measure electron transport-mediated metmyoglobin reduction and metmyoglobin reductase activity. Addition of succinate and NAD increased oxygen consumption, NADH formation, electron transport-mediated metmyoglobin reduction, and reductase activity (p<0.05). Addition of antimycin A prevented electron flow beyond complex III, therefore, decreasing oxygen consumption and electron transport-mediated metmyoglobin reduction. Addition of rotenone prevented reverse electron flow, increased oxygen consumption, increased electron transport-mediated metmyoglobin reduction, and decreased NADH formation. Succinate and NAD can generate NADH in bovine tissue postmortem via reverse electron flow and this NADH can be used by both electron transport-mediated and metmyoglobin reductase pathways.

Proximal Tibia Bone Graft: An alternative Donor Source especially for Foot and Ankle Procedures

Bone graft is essential in various orthopaedic procedures. Among the many donor sites for harvesting autologous bone graft, the iliac crest has been the most commonly used. However, for foot and ankle procedures the proximal tibia has gained popularity as an alternative donor site due to its anatomic proximity to the primary surgical site. In this article we evaluated the possible complications associated with harvesting proximal tibia bone graft. Our study showed the low incidence of morbidity in harvesting proximal tibia bone graft, thereby providing a good alternative donor for foot and ankle procedures.

Effect of daily lithium chloride administration on bone mass and strength in growing broiler chickens

The objective was to determine the effects of oral lithium chloride supplementation on bone strength and mass in broiler chickens. Ninety-six broilers were assigned to 1 of 2 treatment groups (lithium chloride or control; n=48/treatment). Beginning at 1 or 3 wk of age, chickens were administered lithium chloride (20 mg/kg body weight) or water daily by oral gavage. At 6 wk of age, chickens were euthanized and bone and muscle samples were collected. A 24 h lithium chloride (20 mg/kg body weight) challenge determined that serum lithium chloride increased within 2 h and cleared the system within 24 h, demonstrating the effective delivery of lithium chloride. Treatment did not influence body weight (P≥0.20) or feed intake (P≥0.81), demonstrating that lithium chloride did not negatively affect broiler growth. To determine bone strength, 3-point bending was performed on the femora and tibiae obtained from control and lithium chloride-treated birds in the 1 wk group. Lithium chloride-treated birds had a 22% reduction in stiffness compared with control in the femora (P=0.02) without a corresponding reduction in elastic modulus. No differences were observed in yield or ultimate load and in the corresponding calculations of stresses (P≥0.26). The toughness of tibiae was not altered in lithium chloride compared with control (P=0.11). Bone length and micro-CT imaging were performed on the tibiae of control and lithium chloride groups. No differences (P≥0.52) in bone length, cortical or trabecular bone volume, trabecular thickness, number, or spacing were observed. Lithium chloride treatment did not affect pectoralis muscle color or lipid oxidation (P>0.05). In conclusion, lithium chloride treatment in broilers did not negatively affect growth or meat quality. A reduction in bone stiffness of the femur with lithium chloride treatment was observed, however unlike the mouse model, the dosages of lithium chloride used in the current study did not result in anabolic effects on broiler long bones.

Neonatal resuscitation using a nasal cannula: a single-center experience

OBJECTIVE

The aim of the study was to describe our experience using a modified nasal cannula to deliver nasal continuous positive airway pressure and/or nasal intermittent positive pressure ventilation during primary neonatal resuscitation of preterm and term newborns.

STUDY DESIGN

Data were collected retrospectively for all neonates resuscitated with nasal cannula in the delivery room. The primary outcome was the number of newborns intubated in the delivery room. Secondary outcomes included need for chest compressions, intubations in the first 24 hours, air-leaks, and surfactant administration.

RESULTS

A total of 102 infants were resuscitated using nasal cannula. Eight (7.8%) were intubated in the delivery room, five (4.9%) required chest compressions, and five (4.9%) had pneumothorax noted on chest X-ray. No deaths occurred in the delivery room. Twenty-eight patients (27.5%) received early rescue surfactant after admission to the neonatal intensive care unit.

CONCLUSION

Neonatal resuscitation can be effectively performed in preterm and term newborns using a modified nasal cannula in the delivery room.

Study on return to work following surgery on patients with thoracolumbar fracture

OBJECTIVE

The aim is to find rate of return to work of surgically treated thoracolumbar fracture patients and to know if back pain, compensation issues or neurological status influence this rate.

METHODOLOGY

A retrospective cohort study analysing the patients with thoracolumbar fractures treated surgically from January 2008 till December 2009.

RESULTS

Neurological status is the main factor deciding return to work in this group. Back pain and compensation related issues were not statistically significant in influencing return to work. 74% of patients in this group return to work.

CONCLUSION

Return to work among the patients with thoracolumbar fracture, treated surgically, is mainly dependent on neurological status and not the compensation related issues or back pain.

Mortality in preterm infants with respiratory distress syndrome treated with poractant alfa, calfactant or beractant: a retrospective study

OBJECTIVE

The objective of this study is to compare all-cause in-hospital mortality in preterm infants with respiratory distress syndrome (RDS) treated with poractant alfa, calfactant or beractant.

STUDY DESIGN

A retrospective cohort study of 14 173 preterm infants with RDS, treated with one of three surfactants between 2005 and 2009, using the Premier Database was done. Multilevel, multivariable logistic regression modeling, adjusting for patient- and hospital-level factors was performed.

RESULT

Calfactant treatment was associated with a 49.6% greater likelihood of death than poractant alfa (odds ratio (OR): 1.496, 95% confidence interval (CI): 1.014-2.209, P=0.043). Beractant treatment was associated with a non-significant 37% increase in mortality, compared with poractant alfa (OR: 1.370, 95% CI: 0.996-1.885, P=0.053). No differences in mortality were observed between calfactant and beractant treatment (OR: 1.092, 95% CI: 0.765-1.559, P=0.626).

CONCLUSION

Poractant alfa treatment for RDS was associated with a significantly reduced likelihood of death when compared with calfactant and a trend toward reduced mortality when compared with beractant.

Bovine mitochondrial oxygen consumption effects on oxymyoglobin in the presence of lactate as a substrate for respiration

Research suggests that NADH formed from lactate addition can increase mitochondrial oxygen consumption. However, limited research has assessed the subsequent effects of lactate-mediated mitochondrial oxygen consumption on oxymyoglobin. Therefore, our objective was to assess the effects of bovine mitochondrial oxygen consumption on oxymyoglobin in the presence of lactate, LDH, and NAD. Isolated beef cardiac and skeletal muscle mitochondria (n=5) were reacted with lactate (40 mM), LDH (100 units), and NAD (0.02 mM) to initiate oxygen consumption. Myoglobin redox state was measured to assess the effects of oxygen consumption on oxymyoglobin. The addition of lactate-LDH-NAD to mitochondria increased (p<0.05) both oxygen consumption and conversion of oxymyoglobin to deoxymyoglobin compared with control mitochondria without substrates. The addition of antimycin A to mitochondria decreased oxygen consumption and deoxymyoglobin formation (p<0.05). The results suggest that increased oxygen consumption can influence myoglobin redox state and this effect might be partially responsible for the darkening effect in lactate enhanced beef.

Surfactants in the management of respiratory distress syndrome in extremely premature infants

Respiratory distress syndrome (RDS) is primarily due to decreased production of pulmonary surfactant, and it is associated with significant neonatal morbidity and mortality. Exogenous pulmonary surfactant therapy is currently the treatment of choice for RDS, as it demonstrates the best clinical and economic outcomes. Studies confirm the benefits of surfactant therapy to include reductions in mortality, pneumothorax, and pulmonary interstitial emphysema, as well as improvements in oxygenation and an increased rate of survival without bronchopulmonary dysplasia. Phospholipids (PL) and surfactant-associated proteins (SP) play key roles in the physiological activity of surfactant. Different types of natural and synthetic surfactant preparations are currently available. To date, natural surfactants demonstrate superior outcomes compared to the synthetic surfactants, at least during the acute phase of RDS. This disparity is often attributed to biochemical differences including the presence of surfactant-associated proteins in natural products that are not found in the currently available synthetic surfactants. Comparative trials of the natural surfactants strive to establish the precise differences in clinical outcomes among the different preparations. As new surfactants become available, it is important to evaluate them relative to the known benefits of the previously existing surfactants. In order to elucidate the role of surfactant therapy in the management of RDS, it is important to review surfactant biochemistry, pharmacology, and outcomes from randomized clinical trials.

A Cost Minimization Comparison of Two Surfactants-Beractant and Poractant alfa-Based Upon Prospectively Designed, Comparative Clinical Trial Data

OBJECTIVES

To compare the pharmacoeconomic profiles of beractant (Survanta(®), Ross Laboratories, Columbus, Ohio) and poractant alfa (Curosurf(®), DEY LP, Napa, CA) via a cost-minimization analysis.

METHODS

This analysis was based upon clinical data from two previously published studies (Speer C, et al. Arch Dis Child 1995;72: F8-13; and Ramanathan R, et al. Am J Perinatol 2004; 21:109-19) where investigators found significant differences in the number of doses required to achieve a similar clinical response. Our analyses employed several models based upon single-use or multiple-use of single-use vial scenarios, average wholesale pricing, and costs computed on a per-patient basis. Model 1 involved single-dose vials and mean weight of the infants (both trials). Models 2 and 3, based on individual patient weights, assessed single-dose and multiple-use of single-dose vials cost scenarios, respectively. Individual patient weights allowed for statistical evaluation in Models 2 and 3.

RESULTS

Model 1 savings with poractant alfa treatment was $949.67 (53%) based upon Speer and $617.90 (46%) based upon Ramanathan. Models 2 and 3 reported savings for poractant alfa of $220.50 (20%) (P = 0.11) and $180 (20%) (P = 0.018), respectively over beractant.

CONCLUSIONS

These analyses would suggest poractant alfa may offer a less costly, clinically-equivalent option. Savings may vary with vial usage and mix, patient weight distribution, and how surfactants are used in practice. Institutions utilizing surfactants may wish to examine usage patterns, dosing protocols, and patient mix to determine what potential savings may exist.

Entropic test of quantum contextuality

We study the contextuality of a three-level quantum system using classical conditional entropy of measurement outcomes. First, we analytically construct the minimal configuration of measurements required to reveal contextuality. Next, an entropic contextual inequality is formulated, analogous to the entropic Bell inequalities derived by Braunstein and Caves [Phys. Rev. Lett. 61, 662 (1988)], that must be satisfied by all noncontextual theories. We find optimal measurements for violation of this inequality. The approach is easily extendable to higher dimensional quantum systems and more measurements. Our theoretical findings can be verified in the laboratory with current technology.

The development of the circadian heart rate rhythm (CHR) in Asian infants

OBJECTIVE

To test the hypothesis that term-born Asian infants, at reduced risk to die of Sudden Infant Death Syndrome (SIDS) exhibit a circadian heart rate rhythm (CHR) at a later age than non-Asian term infants.

METHOD

Repeated overnight heart rate (HR) traces obtained with a battery-operated Polar S810i heart-rate monitor at home in 17 Asian Torajan infants in Indonesia, were compared with those of 52 non-Asian infants monitored as part of the Collaborative Home Infant Monitoring Evaluation (CHIME). HR was determined using a moving window averaging technique. A comparison of median HR during quiet sleep (QS) episodes (identified by minimum HR variability), established the presence of CHR.

RESULTS

Seventy three percent of non-Asian CHIME infants ≤7 weeks exhibited CHR compared to 45% of Asian Torajan infants. Between 8 and 12 weeks, 94% of non-Asian CHIME infants exhibited CHR, compared to 33% of Asian Torajan infants (p<0.001). Forty seven and 56% of Asian Torajan infants exhibited the CHR at the age intervals of 16-20 weeks and 21-25 weeks respectively. Active wakefulness percentages as a function of the entire recording and median QS HR were not significantly different in the two groups.

CONCLUSION

Despite the fact that Asian Torajan infants were on average a week older than non-Asian CHIME babies, between two and three months of age only one in three exhibited the CHR, compared to virtually all non-Asian CHIME infants. We speculate that the cause of this difference rests in the infants' environment rather than their genetic origin.

Nasal intermittent positive pressure ventilation after surfactant treatment for respiratory distress syndrome in preterm infants <30 weeks' gestation: a randomized, controlled trial

OBJECTIVE

To compare the effect of early extubation to nasal intermittent positive pressure ventilation (NIPPV) versus nasal continuous positive airway pressure (NCPAP) on the need for mechanical ventilation via endotracheal tube (MVET) at 7 days of age in preterm infants <30 weeks' gestation requiring intubation and surfactant for respiratory distress syndrome (RDS) within 60  min of delivery.

STUDY DESIGN

Multicenter, randomized, controlled trial. A total of 57 infants were randomized within 120  min of birth to NCPAP (BW 1099 g and GA 27.8 weeks) and 53 infants to NIPPV (BW 1052  g, and GA 27.8 weeks). Infants were stabilized on NCPAP at birth and were given poractant alfa combined with MVET within 60  min of age. When stabilized on MVET, they were extubated within the next hours or days to NCPAP or NIPPV.

RESULT

A total of 42% [corrected] of infants needed MVET at 7 days of age in the NCPAP group compared with 17% in the NIPPV group (OR: 3.6; 95% CI: 1.5, 8.7). Days on MVET were 12 ± 11 days in NCPAP group compared with 7.5 ± 12 days in the NIPPV group (median 1 vs 7 days; P=0.006). Clinical bronchopulmonary dysplasia (BPD) was 39% in the NCPAP group compared to 21% in the NIPPV group (OR: 2.4; 95% CI: 1.02, 5.6). Physiological BPD was 46% in the NCPAP group compared with 11% in the NIPPV group (OR: 6.6, 95% CI: 2.4, 17.8; P=0.001). There were no differences in any other outcomes between the two groups.

CONCLUSION

NIPPV compared with NCPAP reduced the need for MVET in the first week, duration of MVET, and clinical as well as physiological BPD in preterm infants receiving early surfactant for RDS.

Accuracy of pulse oximeter readings from probe placement on newborn wrist and ankle

OBJECTIVE

To compare the accuracy of pulse oximetry oxygen saturation (SpO(2)) measured on the wrist compared with the ipsilateral palm, and SpO(2) measured on the ankle compared with the ipsilateral sole.

STUDY DESIGN

In this prospective observational study, neonates admitted to the neonatal intensive care unit were enrolled. We recorded SpO(2) (Masimo Radical-7 pulse oximeter) detected at the palm and ipsilateral wrist initially, then at 30 s, and at 1 min, and we repeated the same procedure over the sole and ipsilateral ankle. We recorded the time to obtain the SpO(2) readings from all these sites. Regression analysis was performed to determine the relationship between paired SpO(2) measurements. The mean difference (bias) and standard deviation of the paired SpO(2) differences (precision) were calculated (Bland-Altman plots).

RESULT

A total of 150 patients (birth weight 2381±1020 g, gestational age 34.3±4.3 weeks, median postnatal age 3.5 days (25th-75th percentile 1-16 days)) were enrolled. There was a good correlation between SpO(2) measured at the palm versus the wrist (r=0.95, P<0.001 (right); r=0.97, P< 0.001 (left)) and between SpO(2) measured at the sole versus the ankle (r=0.92, P<0.001 (right); r=0.91, P<0.001 (left)). There was also a good agreement between paired SpO(2) measurements from these sites. The bias and precision for SpO(2) at the right palm and right wrist was 0.08±0.94% and for the left palm and left wrist 0.22±0.87%. Similarly, the bias and precision for SpO(2) at the right sole and right ankle was -0.03±0.93% and for the left sole and left ankle was -0.01±0.93%.

CONCLUSION

Our results show that the wrist and ankle can be used as alternative sites to measure SpO(2) in newborn infants in place of the routinely used palm or sole.

Effects of 4-hydroxy-2-nonenal on beef heart mitochondrial ultrastructure, oxygen consumption, and metmyoglobin reduction

The effects of 4-hydroxy-2-nonenal (HNE) on mitochondria isolated from bovine hearts (n=5) were assessed using ultrastructure, oxygen consumption, membrane permeability, HNE binding, and metmyoglobin reduction in vitro. Pre-incubation (pH 5.6 and 7.4 at 25°C) of mitochondria with HNE decreased oxygen consumption compared with samples without HNE (P<0.05). Electron microscopy revealed that HNE-treated mitochondria were swollen and had increased membrane permeability at pH 7.4, compared with ethanol controls. Conversely, mitochondria incubated with HNE at pH 5.6 had decreased volume and permeability. Fluorescence studies indicate that HNE binds to the membrane of mitochondria isolated from bovine cardiac muscle (at pH 5.6 and 7.4). HNE-treated mitochondria at both pH 5.6 and 7.4 had lower metmyoglobin reduction and NADH dependent metmyoglobin reductase activity compared with control mitochondria without HNE (P<0.05). In addition to covalent binding with myoglobin, HNE may influence beef color stability by interacting with mitochondria.

Longitudinal assessment of hemoglobin oxygen saturation in preterm and term infants in the first six months of life

OBJECTIVE

To report longitudinal home recordings of hemoglobin O(2) saturation by pulse oximetry (Spo(2)) during unperturbed sleep in preterm and term infants.

STUDY DESIGN

We recorded continuous pulse oximetry during the first 3 minutes of each hour of monitor use (nonevent epochs) for 103 preterm infants born at <1750 g and ≤ 34 weeks postmenstrual age (PMA), and 99 healthy term infants.

RESULTS

Median baseline Spo(2) was approximately 98% for both the preterm and term groups. Episodes of intermittent hypoxemia occurred in 74% of preterm and 62% of term infants. Among infants with intermittent hypoxemia, the number of seconds/hour of monitoring <90% Spo(2) was initially significantly greater in the preterm than the term group and declined with age at a similar rate in both groups. The 75(th) to 95(th) percentiles for seconds/hour of Spo(2) <90% in preterm infants were highest at 36 weeks PMA and progressively decreased until 44 weeks PMA, after which time they did not differ from term infants.

CONCLUSIONS

Clinically inapparent intermittent hypoxemia occurs in epochs unperturbed by and temporally unrelated to apnea or bradycardia events, especially in preterm infants at 36 to 44 weeks PMA.

Local realism of macroscopic correlations

We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles.

Correlation complementarity yields bell monogamy relations

We present a method to derive Bell monogamy relations by connecting the complementarity principle with quantum nonlocality. The resulting monogamy relations are stronger than those obtained from the no-signaling principle alone. In many cases, they yield tight quantum bounds on the amount of violation of single and multiple qubit correlation Bell inequalities. In contrast with the two-qubit case, a rich structure of possible violation patterns is shown to exist in the multipartite scenario.