An experimental investigation to model wheezing in lungs.

A quarter of the world's population experience wheezing. These sounds have been used for diagnosis since the time of the Ebers Papyrus (ca 1500 BC). We know that wheezing is a result of the oscillations of the airways that make up the lung. However, the physical mechanisms for the onset of wheezing remain poorly understood, and we do not have a quantitative model to predict when wheezing occurs. We address these issues in this paper. We model the airways of the lungs by a modified Starling resistor in which airflow is driven through thin, stretched elastic tubes. By completing systematic experiments, we find a generalized 'tube law' that describes how the cross-sectional area of the tubes change in response to the transmural pressure difference across them. We find the necessary conditions for the onset of oscillations that represent wheezing and propose a flutter-like instability model for it about a heavily deformed state of the tube. Our findings allow for a predictive tool for wheezing in lungs, which could lead to better diagnosis and treatment of lung diseases.

Delay of Fetal Anatomy Ultrasound Assessment Based on Maternal Body Mass Index Does Not Reduce the Rate of Inadequate Visualization.

OBJECTIVES: To determine whether delay of initial anatomy ultrasound based on the maternal body mass index (BMI) reduces the rate of inadequate visualization compared to standard timing at 180/7 to 196/7 weeks. METHODS: A retrospective study of singleton anatomy assessments was conducted at a tertiary care center in the 2-year period before (A, 2012-2014) and after (B, 2014-2016) protocol initiation. Assessments in period B were scheduled on the basis of the BMI in the first trimester: lower than 25 kg/m2 , 180/7 to 196/7 weeks; 25 to 29.9 kg/m2 , 190/7 to 206/7 weeks; 30 to 34.9 kg/m2 , 200/7 to 216/7 weeks; 35 to 39.9 kg/m2 , 210/7 to 226/7 weeks; and 40 kg/m2 or higher, 220/7 to 236/7 weeks. In period A, assessments were scheduled between 180/7 and 196/7 weeks. The rate of inadequate visualization and repeated assessments in periods A and B were compared. Multivariable logistic regression, per-protocol, and BMI subgroup analyses were completed. RESULTS: In total, 3491 pregnancies in period A and 3672 in period B were included. In period B, 74% were scheduled per protocol; however, this rate decreased for higher-BMI categories (52% for BMI ≥40 kg/m2 ). The inadequate visualization rate was slightly higher in period B versus A (16.9% versus 15.0%; P = .03) and exceeded 35% for a BMI of 40 kg/m2 or higher, with or without delay. After adjusting for maternal age and fetal presentation, period B had small increased odds of inadequate visualization versus period A (adjusted odds ratio, 1.2; 95% confidence interval, 1.02-1.38). Repeated assessment rates were similar in periods B and A (14.0% versus 13.1%; P = .25). CONCLUSIONS: In pregnancies with obesity, a protocol delaying the initial assessment beyond 196/7 weeks based on the maternal BMI does not reduce the rate of inadequate visualization.

No. 239-Obesity in Pregnancy.

OBJECTIVE: To review the evidence and provide recommendations for the counselling and management of obese parturients. OUTCOMES: Outcomes evaluated include the impact of maternal obesity on the provision of antenatal and intrapartum care, maternal morbidity and mortality, and perinatal morbidity and mortality. EVIDENCE: Literature was retrieved through searches of Statistics Canada, Medline, and The Cochrane Library on the impact of obesity in pregnancy on antepartum and intrapartum care, maternal morbidity and mortality, obstetrical anaesthesia, and perinatal morbidity and mortality. Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to April 2009. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. VALUES: The evidence obtained was reviewed and evaluated by the Maternal Fetal Medicine and Clinical Practice Obstetric Committees of the SOGC under the leadership of the principal authors, and recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care. BENEFITS, HARMS, AND COSTS: Implementation of the recommendations in this guideline should increase recognition of the issues clinicians need to be aware of when managing obese women in pregnancy, improve communication and consultation amongst the obstetrical care team, and encourage federal and provincial agencies to educate Canadians about the values of entering pregnancy with as healthy a weight as possible.

No 129-L'exercice physique pendant la grossesse et le postpartum.

OBJECTIF: Énoncer une directive canadienne visant à informer les fournisseurs de soins obstétricaux des répercussions, pour la mère, le fœtus et le nouveau-né, des exercices de conditionnement aerobique et musculaire pendant la grossesse. RéSULTATS ATTENDUS: Effets sur la morbidité maternelle, fœtale et néonatale et mesures de la forme physique maternelle. PREUVES: Une recherche sur MEDLINE des articles, publiés en anglais de 1966 à 2002, appartenant aux catégories suivantes : études sur le conditionnement aérobique et musculaire chez des femmes ne faisant pas jusque-là d'exercice et chez des femmes actives avant leur grossesse, ainsi que des études sur les répercussions du conditionnement aérobique et musculaire sur les issues précoces et tardives de la grossesse ou sur les issues néonatales; rapports de synthèse et méta-analyses portant sur l'exercice pendant la grossesse. VALEURS: Les résultats recueillis ont été revus par la Société des obstétriciens et gynécologues du Canada (Comité de la pratique clinique - obstétrique), avec la participation de la Société canadienne de physiologie de l'exercice, et ils ont été classés suivant les critères d'évaluation des preuves établis par le Groupe de travail canadien sur l'examen de santé périodique. RECOMMANDATIONS: VALIDATION: Cette directive a été approuvée par le Comité de pratique clinique - obstétrique de la SOGC, par le Comité exécutif et par le Conseil de la SOGC, ainsi que par le Conseil d'administration de la Société canadienne de physiologie de l'exercice. PARRAINé PAR: la Société des obstétriciens et gynécologues du Canada et par la Société canadienne de physiologie de l'exercice.

No. 129-Exercise in Pregnancy and the Postpartum Period.

OBJECTIVE: To design Canadian guidelines advising obstetric care providers of the maternal, fetal, and neonatal implications of aerobic and strength-conditioning exercises in pregnancy. OUTCOMES: Knowledge of the impact of exercise on maternal, fetal, and neonatal morbidity, and of the maternal measures of fitness. EVIDENCE: MEDLINE search from 1966 to 2002 for English language articles related to studies of maternal aerobic and strength conditioning in a previously sedentary population, maternal aerobic and strength conditioning in a previouslyactive population, impact of aerobic and strength conditioning on early and late pregnancy outcomes, and impact of aerobic and strength conditioning on neonatal outcomes, as well as for review articles and meta-analyses related to exercise in pregnancy. VALUES: The evidence collected was reviewed by the Society of Obstetricians and Gynaecologists of Canada (SOGC Clinical Practice Obstetrics Committee) with representation from the Canadian Society for Exercise Physiology, and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam. RECOMMENDATIONS: VALIDATION: This guideline has been approved by the SOGC Clinical Practice Obstetrics Committee, the Executive and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise Physiology. SPONSORS: This guideline has been jointly sponsored by The Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology.

The elastic theory of shells using geometric algebra.

We present a novel derivation of the elastic theory of shells. We use the language of geometric algebra, which allows us to express the fundamental laws in component-free form, thus aiding physical interpretation. It also provides the tools to express equations in an arbitrary coordinate system, which enhances their usefulness. The role of moments and angular velocity, and the apparent use by previous authors of an unphysical angular velocity, has been clarified through the use of a bivector representation. In the linearized theory, clarification of previous coordinate conventions which have been the cause of confusion is provided, and the introduction of prior strain into the linearized theory of shells is made possible.

We Should Proceed With Caution When It Comes to Antenatal Corticosteroids After 34 Weeks.

The Society for Maternal-Fetal Medicine recently released a statement supporting the use of antenatal corticosteroids for women at high risk of late preterm birth. This followed a trend of increasing use of antenatal corticosteroids after 34 weeks' gestation, based on evidence for decreased respiratory morbidity. The absolute benefits, however, are relatively small. We should balance this against the possible long-term harms of corticosteroids after 34 weeks before expanding the indications for their antenatal use.

Using geometric algebra to represent curvature in shell theory with applications to Starling resistors.

We present a novel application of rotors in geometric algebra to represent the change of curvature tensor that is used in shell theory as part of the constitutive law. We introduce a new decomposition of the change of curvature tensor, which has explicit terms for changes of curvature due to initial curvature combined with strain, and changes in rotation over the surface. We use this decomposition to perform a scaling analysis of the relative importance of bending and stretching in flexible tubes undergoing self-excited oscillations. These oscillations have relevance to the lung, in which it is believed that they are responsible for wheezing. The new analysis is necessitated by the fact that the working fluid is air, compared to water in most previous work. We use stereographic imaging to empirically measure the relative importance of bending and stretching energy in observed self-excited oscillations. This enables us to validate our scaling analysis. We show that bending energy is dominated by stretching energy, and the scaling analysis makes clear that this will remain true for tubes in the airways of the lung.

Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 2-the effect of exercise on the fetus, labour and birth.

This is Part 2 of 5 in the series of evidence statements from the IOC expert committee on exercise and pregnancy in recreational and elite athletes. Part 1 focused on the effects of training during pregnancy and on the management of common pregnancy-related symptoms experienced by athletes. In Part 2, we focus on maternal and fetal perinatal outcomes.

Emergency Caesarean Section in Obese Parturients: Is a 30-Minute Decision-to-Incision Interval Feasible?

OBJECTIVE: To determine the effect of obesity on decision-to-incision and decision-to-delivery time intervals in emergency Caesarean section. METHODS: We performed a retrospective study of emergency Caesarean sections performed between 2005 and 2009. Indications for emergency Caesarean section were defined as those posing an immediate threat to the life of the mother or fetus. The primary outcomes were the time intervals from decision for emergency delivery to skin incision, and decision to delivery of the infant. The secondary outcome was a composite of poor neonatal outcomes comprising umbilical cord artery pH lt; 7.20, Apgar score lt; 7 at five minutes, admission to NICU, or neonatal death. RESULTS: A total of 232 women underwent emergency Caesarean section, and 140 of these met the inclusion criteria. At the time of delivery, 78/140 (55.7%) patients were categorized as obese (BMI ≥ 30kg/m2). The median decision-to-incision and decision-to-delivery intervals were significantly longer in the obese group, with a median delay of 4.5 minutes in both time intervals. Time-to-event analysis demonstrated prolongation of the decision-to-incision interval in the obese group (hazard ratio 0.71, P lt; 0.05). There was no difference in the neonatal composite outcome, but there was a significant reduction in median five-minute Apgar score in the obese group (P = 0.02). CONCLUSION: Obesity is associated with prolonged decision-to-incision and decision-to-delivery intervals, without associated neonatal morbidity, in a tertiary hospital setting. Further studies are required to assess the specific factors limiting expedient delivery in this population.

Objective : Déterminer l'effet de l'obésité sur les intervalles décision-incision et décision-accouchement en ce qui concerne la tenue d'une césarienne d'urgence. Méthodes : Nous avons mené une étude rétrospective portant sur les césariennes d'urgence menées entre 2005 et 2009. Les indications menant à la tenue d'une césarienne d'urgence ont été définies comme étant celles qui constituaient une menace immédiate pour la vie de la mère ou celle du fœtus. Les critères d'évaluation principaux ont été l'intervalle entre la décision de procéder à un accouchement d'urgence et l'exécution de l'incision cutanée, et l'intervalle entre cette décision et la naissance de l'enfant. Le critère d'évaluation secondaire était un composite de diverses mauvaises issues néonatales, dont un pH artériel (cordon ombilical) lt; 7,20, un indice d'Apgar lt; 7 à cinq minutes, l'admission à l'UNSI et le décès néonatal. Résultats : Au total, 232 femmes ont subi une césarienne d'urgence et 140 d'entre elles répondaient aux critères d'inclusion. Au moment de l'accouchement, 78/140 (55,7 %) patientes ont été catégorisées comme étant obèses (IMC ≥ 30kg/m2). Les intervalles décision-incision et décision-accouchement médians étaient considérablement plus longs dans le groupe des femmes obèses (délai médian de 4,5 minutes pour ce qui est de ces deux intervalles). L'analyse du délai avant la survenue de l'événement a démontré la prolongation de l'intervalle décision-incision au sein du groupe des femmes obèses (rapport de risque, 0,71; P lt; 0,05). Bien qu'aucune différence n'ait été constatée en ce qui concerne l'issue composite néonatale, une baisse significative de l'indice d'Apgar médian à cinq minutes a été observée au sein du groupe des femmes obèses (P = 0,02). Conclusion : L'obésité est associée à une prolongation des intervalles décision-incision et décision-accouchement, sans répercussions connexes sur la morbidité néonatale, en milieu hospitalier tertiaire. La tenue d'autres études s'avère requise pour l'évaluation des facteurs particuliers qui limitent la tenue d'un accouchement en temps opportun au sein de cette population.

Creation of plastinated placentas as a novel teaching resource for medical education in obstetrics and gynaecology.

INTRODUCTION: Knowledge of the gross anatomy of the placenta is fundamental in order to help identify potential complications during pregnancy. The placenta is difficult to study without a three-dimensional appreciation of its structure. The aim of this study was to develop a collection of plastinated placenta specimens and accompanying clinical educational materials to provide learning resources for placental abnormalities and their associated pregnancy outcomes. These plastinates and educational modules were used as teaching resources for both undergraduate and post-graduate medical trainees in Obstetrics and Gynaecology. METHODS: Placentas were plastinated by S10 silicone plastination. Clinical education materials were created that included ultrasound images, photographs and information on the associated pregnancy outcomes. Utility of the plastinates was assessed using questionnaires completed by 70 medical students and 33 attendees at the 8th and 9th Annual International Human Placenta Workshop held at Queen's University, Kingston, ON. Attendees included graduate students, post-doctoral fellows, medical residents, research investigators and clinicians. RESULTS: Data collected demonstrated that 76.7% of medical student (n = 60) and 78.1% of Placenta Workshop attendees (n = 32) preferred plastinates as a supplemental learning resource compared to textbooks and images alone (36.7% and 37.5% respectively). All respondents also expressed the desire to have plastinated placentas available for future learning opportunities. DISCUSSION: Plastinated placentas are a valuable addition as teaching resources for many demographic groups with an interest in placental anatomy and pathology. Medical trainees and residents in Obstetrics and Gynaecology would benefit from the availability of plastinates as educational tools.

Review: the enigmatic role of endoglin in the placenta.

The cellular expression, structure and function of endoglin, and its implication in several vascular disorders remain enigmatic, even 30 years after its discovery. Endoglin (CD105) is a homodimeric glycoprotein (180 kDa) constitutively expressed in the vascular endothelium. It is essential for cardiovascular development and mutations in the ENG gene lead to Hereditary Hemorrhagic Telangiectasia, a disorder characterized by arteriovenous malformations. Endoglin is also expressed in the syncytiotrophoblast throughout pregnancy, but transiently upregulated in the extravillous trophoblast of anchoring villi. Endoglin modulates responses to several TGF-ß superfamily ligands and is essential for the negative regulation by TGF-ß isoforms 1 and 3 of extravillous trophoblast differentiation. Membrane endoglin binds endothelial NO synthase and regulates its activation and vasomotor tone. There is also a circulating soluble form of endoglin (sEng; 65 kDa); its levels in the serum of women with preeclampsia are increased and correlated with disease severity. The exact sequence of sEng is still unresolved and the proposed mechanism of release from the syncytium by metalloproteases would not yield the expected size protein. The nature of the ligand sequestered by sEng is also an enigma. sEng is said to block the effects of TGF-ß on NO-mediated vasorelaxation. However, sEng alone cannot scavenge these ligands for which it has very low affinity. sEng binds with high affinity to BMP9, which stimulates secretion from endothelial cells of the vascoconstrictor endothelin-1, also implicated in endothelial cell stabilization. It remains to be determined if scavenging of circulating BMP9 by sEng is important in preeclampsia and regulation of hypertension.

Thromboembolism in the obese pregnant woman.

We sought to quantify the added risk of thromboembolism in the obese parturient, evaluate risk factors for thromboembolism in the obese parturient, and provide suggestions as to when and in what form thromboembolism prophylaxis should be considered. Although recent guidelines from national colleges and advisory groups have attempted to guide the clinician in thromboprophylaxis in the obese parturient, the lack of adequate prospective series and trials has lead to some contrary recommendations. The arbitrary use of bed rest in the obese patient is a significant risk factor for venous thromboembolism without proven benefit. Despite a paucity of gold standard evidence, the prevalence of obesity and its associated risk of venous thromboembolism warrants careful consideration for the use of thromboprophylaxis in the obese pregnant population. This is especially important in the presence of additional thromboembolism risk factors.

Brachial artery flow-mediated dilation is not affected by pregnancy or regular exercise participation.

Whether brachial artery FMD (flow-mediated dilation) is altered in pregnancy by 28-35 weeks compared with non-pregnant women remains controversial. The controversy may be due to limitations of previous studies that include failing to: (i) test non-pregnant controls in the mid-late luteal phase, (ii) account for effects of pregnancy on the dilatory shear stimulus, (iii) account for physical activity or (iv) control for inter-individual variation in the time to peak FMD. In the present study, brachial artery FMD was measured in 17 active and eight sedentary pregnant women (34.1±1.6 weeks of gestation), and in 19 active and 11 sedentary non-pregnant women (mid-late luteal phase). Decreased vascular tone secondary to increased shear stress contributes minimally to pregnancy-induced increases in baseline brachial artery diameter, as shear stress removal during distal cuff inflation in pregnant women did not reduce diameter to baseline levels observed in non-pregnant controls. Neither the shear stimulus nor the percentage FMD was affected by pregnancy or regular exercise. Continuous diameter measurements are required to control for delayed peak dilation during pregnancy (57±15 compared with 46±15 s; P=0.012), as post-release diameter measured at 60 or 55-65 s post-release underestimated FMD to a greater extent in non-pregnant than in pregnant women.

SOGC Clinical Practice Guidelines: Obesity in pregnancy. No. 239, February 2010.

OBJECTIVE: To review the evidence and provide recommendations for the counselling and management of obese parturients. OUTCOMES: OUTCOMES evaluated include the impact of maternal obesity on the provision of antenatal and intrapartum care, maternal morbidity and mortality, and perinatal morbidity and mortality. EVIDENCE: Literature was retrieved through searches of Statistics Canada, Medline, and The Cochrane Library on the impact of obesity in pregnancy on antepartum and intrapartum care, maternal morbidity and mortality, obstetrical anaesthesia, and perinatal morbidity and mortality. Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to April 2009. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. VALUES: The evidence obtained was reviewed and evaluated by the Maternal Fetal Medicine and Clinical Practice Obstetric Committees of the SOGC under the leadership of the principal authors, and recommendations were made according to guidelines developed by the Canadian Task Force on Preventive Health Care. BENEFITS, HARMS, AND COSTS: Implementation of the recommendations in this guideline should increase recognition of the issues clinicians need to be aware of when managing obese women in pregnancy, improve communication and consultation amongst the obstetrical care team, and encourage federal and provincial agencies to educate Canadians about the values of entering pregnancy with as healthy a weight as possible.