Towards an unsupervised device for the diagnosis of childhood pneumonia in low resource settings: automatic segmentation of respiratory sounds.

Pneumonia remains the worldwide leading cause of children mortality under the age of five, with every year 1.4 million deaths. Unfortunately, in low resource settings, very limited diagnostic support aids are provided to point-of-care practitioners. Current UNICEF/WHO case management algorithm relies on the use of a chronometer to manually count breath rates on pediatric patients: there is thus a major need for more sophisticated tools to diagnose pneumonia that increase sensitivity and specificity of breath-rate-based algorithms. These tools should be low cost, and adapted to practitioners with limited training. In this work, a novel concept of unsupervised tool for the diagnosis of childhood pneumonia is presented. The concept relies on the automated analysis of respiratory sounds as recorded by a point-of-care electronic stethoscope. By identifying the presence of auscultation sounds at different chest locations, this diagnostic tool is intended to estimate a pneumonia likelihood score. After presenting the overall architecture of an algorithm to estimate pneumonia scores, the importance of a robust unsupervised method to identify inspiratory and expiratory phases of a respiratory cycle is highlighted. Based on data from an on-going study involving pediatric pneumonia patients, a first algorithm to segment respiratory sounds is suggested. The unsupervised algorithm relies on a Mel-frequency filter bank, a two-step Gaussian Mixture Model (GMM) description of data, and a final Hidden Markov Model (HMM) interpretation of inspiratory-expiratory sequences. Finally, illustrative results on first recruited patients are provided. The presented algorithm opens the doors to a new family of unsupervised respiratory sound analyzers that could improve future versions of case management algorithms for the diagnosis of pneumonia in low-resources settings.

Smartphone attachment for stethoscope recording.

With the ubiquity of smartphones and the rising technology of 3D printing, novel devices can be developed that leverage the "computer in your pocket" and rapid prototyping technologies toward scientific, medical, engineering, and creative purposes. This paper describes such a device: a simple 3D-printed extension for Apple's iPhone that allows the sound from an off-the-shelf acoustic stethoscope to be recorded using the phone's built-in microphone. The attachment's digital 3D files can be easily shared, modified for similar phones and devices capable of recording audio, and in combination with 3D printing technology allow for fabrication of a durable device without need for an entire factory of expensive and specialized machining tools. It is hoped that by releasing this device as an open source set of printable files that can be downloaded and reproduced cheaply, others can make use of these developments where access to cost-prohibitive, specialized medical instruments are not available. Coupled with specialized smartphone software ("apps"), more sophisticated and automated diagnostics may also be possible on-site.

The medical and legal risks of the electronic fetal monitor.

Electronic fetal heart monitoring (EFM) is the most widely used method of monitoring the fetal heartbeat for possible signs of distress during delivery. Soon after its development in the 1960s, EFM replaced intermittent auscultation as the standard of care in the obstetrical community. However, Margaret Lent argues that the widespread use of EFM is both medically and legally unsound. Lent points to a series of clinical trials that demonstrate that EFM does not reduce fetal mortality, morbidity, or cerebral palsy rates. These studies suggest that EFM has a very high false positive rate, and that EFM usage correlates strongly with a rise in cesarean section rates. Similarly, EFM provides no protection in the courtroom. Though obstetricians believe that they should use EFM because its status as the standard of care will protect them from liability, Lent argues that it may in fact expose them to liability given its failings. Instead, she argues that auscultation is equally, if not more, safe and effective, and is more likely to protect physicians from liability. Lent concludes that obstetricians have an obligation to their patients and to themselves to adopt auscultation as the new standard of care.

ESTRACE--1: a stethoscope for functional checking of electrostimulators and low cost body surface mapping system.

In a project on the mapping of body surface potentials evoked by implanted spinal cord stimulators and transcutaneous electrostimulators, a simple device was developed for use in polyclinical practice for easy checking of the function of these stimulators. The device is an electrical stethoscope and consists of an instrumentation amplifier, bandpass filter, a distortion circuit and a headphone. In vivo measurements demonstrate the generation of an amplitude-dependent tone by the distortion circuit. The apparatus is in many aspects similar to a stethoscope: simple to understand and a practical tool for a fast Go/No-Go test. The device can be optionally connected with a PC and enables body surface mapping documentation within a few minutes.

Cost effectiveness in the detection of renal artery stenosis.

Cost effectivenesses of four tests for diagnosing renal artery stenosis were examined. Sensitivity, specificity, cost per patient, and cost per stenosis found for a variety of diagnostic strategies using these tests were retrospectively evaluated using clinical data from 605 hypertensive patients. Cost effectiveness of a given strategy was found to depend on the sequence in which the tests were performed, but to be relatively independent of the exact cost of the tests. Auscultation for a systolic/diastolic abdominal bruit was the most cost-effective test for beginning a diagnostic strategy and showed a 99.6% specificity for stenosis. When the patient has a systolic bruit only or no bruit, plasma renin activity measurement should guide the clinician's choice of whether to test further with intravenous pyelography or renal arteriography. Diagnosis of renal artery stenosis using these tests is estimated to cost between $2,300 and $6,200 per stenosis found, depending on the prevalence of renal artery stenosis.