Under control conditions, the right ventricle operates at maximum efficiency and submaximal work output. Compliance of the pulmonary artery is a significant factor in decoupling the right ventricle from its vascular load. As the compliance decreases with acute pulmonary hypertension, the maximum stroke work against load point shifted in such a manner that the right ventricle changed its operational status from a flow to a pressure pump, resulting in a decreased stroke volume.

No abstract

Background It would be helpful if patients with asthma who require admission to hospital for an acute attack could be identified. Methods The relation between the severity of an attack of asthma as determined by admission assessment and the eventual outcome was studied in 52 asthmatic patients aged 14 to 44 years and admitted to an asthma emergency room. The patient's history, including medication and previous admissions to hospital, was recorded and a clinical assessment, including a full inspiratory and expiratory flow-volume loop, was performed on four occasions: on admission, at two hours and at 12-18 hours after the start of a standardised treatment, and two weeks later on an outpatient basis. Patients who were discharged and who had an uneventful follow up at the two week assessment were defined as good responders. Patients who had to be admitted to hospital after 12 to 18 hours or were readmitted during the two weeks, or both, were defined as poor responders. Results Thirty eight patients were good responders and 14 were poor responders (seven admitted at 12 to 18 hours, seven returned to hospital). All four patients with a raised arterial carbon dioxide tension (Paco2) ( > 6 kPa) and the three with cyanosis were in the poor responder group, and this group had lower peak expiratory flow (PEF) values (21% v 30% predicted) on admission. There was, however, considerable overlap in PEF between the two groups and no clinical measure was able to distinguish between the good and the poor responders reliably. Poor

An easy and accurate method of assessing bronchial hyper-reactivity could be of great value in identifying and classifying the degree of severity of asthma in children. The sensitivity and specificity of three methods of provocation, ie, histamine, nebulized water, and exercise, were compared in 20 asthmatic and 20 control children between ages 5 and 13 years. Three clinical categories of severity ranging from slight (Group 1) through moderate (Group 2) to severe asthma (Group 3) were identified. The three methods were compared in each subgroup for detecting a tendency to bronchospasm. An inverse correlation (-0.57) was found between the histamine dose and clinical degree of severity, whereas distilled water and exercise proved to be too insensitive for identifying Group 1 asthmatics. Histamine challenge in children is a safe and sensitive technique for identifying asthma and for monitoring the severity of the disease during follow-up.

Attention-decit/hyperactivity disorder (ADHD) is a common neuropsychiatric disorder that impairs social, academic, and occupational functioning in children, adolescents and adults. It is estimated that approximately as high as 10% of South African children have ADHD. Some dilemmas are however present in terms of the treatment of the disorder: rstly, there are no risk-free methods for its treatment and secondly, no fully objective diagnostic assessments exist. To date, very few quantitative methods have been successfully implemented. It is therefore necessary to further investigate methods that objectively diagnose, treat, and manage the disorder. The aim of the study is thus to develop a novel method that can be used as an aid to provide screening of ADHD. The method proposed is the form of a tablet-based game with underlying algorithms. The objective of the method is to dierentiate between an ADHD individual versus a non-ADHD individual, based on the way they play the game. A beta-testing phase was done and comprised of 30 children (19 non-ADHD and 11 ADHD) between the ages of 4 and 18 years old. The machine learning model that was used was linear support vector machine (SVM). Two datasets were used: 1) game-play dataset which included data such as task completion time and number of mistakes made and 2) accelerometer data set from the tri-axial accelerometer. A feature set was extracted from these two datasets and the best features were selected using sequential forward selection. These best features were then used for developing the classier. A test set accuracy of 85.7% was achieved. Leave-one-out cross-validation (LOOCV) was performed and its accuracy was 83.5%. An overall classication accuracy of 86.5% was achieved. For the application of a screening tool, sensitivity was deemed an important metric and. The model achieved a sensitivity of 75% which was seen as acceptable. The results of the classier were indicative that a quantitative tool could indeed be developed to screen for ADHD. iv Stellenbosch University https://scholar.sun.ac.za I would like to extend the most sincere gratitude and thanks to the following individuals: Prof. Pieter Fourie, for his guidance, vision, enthusiasm and inspiration, without which this project would not be possible. Prof. Fourie spoke to me at the end of my nal year undergrad and convinced me to join him on this project. Ever since then, it's been a great journey towards creating a tangible solution that would change many people's lives for the better. Romano Swart, my colleague, whose support and teamwork in the conceptualisation phases of the game design was very valuable. Mark Atkinson and his team, for delivering a high quality game that met the requirements of the project within a feasible budget and time frame. My family, for being an ever-present support structure throughout the course of the study and throughout all of my endeavours. Lastly, I would like to extend great gratitude to Ms. Veronica Mwamfupe, whose moral support has been tremendous. She's encouraged me an...

In 11 pigs under general endotracheal anaesthesia, the time-domain method of determining the pulmonary arterial input impedance was compared with the frequency-domain equivalent under normal conditions as well as acute pulmonary hypertension induced by glass microspheres. The time-domain methods of determining the pulmonary arterial compliance C and pulmonary vascular bed resistance Rp compared favourably with the frequency-domain equivalents (r = 0.774, n = 60, p < 0.001 and r = 0.906, n = 60, p < 0.001, respectively), even at mean pulmonary artery pressures (MPAP) of 35 mmHg and above. A consistent and ever-increasing difference between characteristic impedance Zo(omega), estimated by averaging input impedance modulus values over a selected frequency range, and its time domain equivalent Ro with increasing MPAP was shown to be the cause of the poor fit between the measured and remodelled pulmonary blood flow. By analysing a time-domain estimate of the pulmonary characteristic impedance Ro(C, Rp, t), it was demonstrated that the characteristic impedance was dependent on C. Ro is therefore not an accurate representation of the characteristic impedance, especially under conditions of acute pulmonary hypertension. Ro(C, Rp, t) should therefore be calculated instead.

No abstract

In article number 2100346, Jürgen Kosel and coworkers develop a facile magnetic tracking system for subcutaneous medical devices, consisting of a lightweight, flexible permanent magnet at the tip and a sensing unit to scan the dermal surface. It enables locating and tracking in a handheld format without the use of x-ray imaging and contrast dyes.