Smart Devices Are Poised to Revolutionize the Usefulness of Respiratory Sounds.

The association between breathing sounds and respiratory health or disease has been exceptionally useful in the practice of medicine since the advent of the stethoscope. Remote patient monitoring technology and artificial intelligence offer the potential to develop practical means of assessing respiratory function or dysfunction through continuous assessment of breathing sounds when patients are at home, at work, or even asleep. Automated reports such as cough counts or the percentage of the breathing cycles containing wheezes can be delivered to a practitioner via secure electronic means or returned to the clinical office at the first opportunity. This has not previously been possible. The four respiratory sounds that most lend themselves to this technology are wheezes, to detect breakthrough asthma at night and even occupational asthma when a patient is at work; snoring as an indicator of OSA or adequacy of CPAP settings; cough in which long-term recording can objectively assess treatment adequacy; and crackles, which, although subtle and often overlooked, can contain important clinical information when appearing in a home recording. In recent years, a flurry of publications in the engineering literature described construction, usage, and testing outcomes of such devices. Little of this has appeared in the medical literature. The potential value of this technology for pulmonary medicine is compelling. We expect that these tiny, smart devices soon will allow us to address clinical questions that occur away from the clinic.

Reporter's occupation and source of adverse device event reports contained in the FDA's MAUDE database.

INTRODUCTION: A review of the medical device adverse events submitted to the United States Food & Drug Administration (FDA) Manufacturer and User Facility Device Experience (MAUDE) database was undertaken to determine the major sources of the information. METHODS: The reporter's occupation and source of the medical device report were determined for acquisition dates Jan 1, 1997 to Dec 31, 2018. A total of 7,766,737 adverse event records were analyzed. RESULTS: 96.6% of reports originated with the manufacturer. Patients (patients/family/friend) were the most frequent submitter of reports directly to the FDA, almost five times as often as physicians. Nurses submitted reports directly to the FDA 2.77 times as often as physicians. Only 0.49% of physician reports were submitted directly to the FDA, representing 0.09% of total MAUDE reports. CONCLUSION: Increasing physician reporting directly to the FDA and MAUDE through the MedWatch reporting system is an imperative. Incorporating information from the perspective of the physician has the potential of increasing the quality of the data and improving the reliability of post-market surveillance.

An Analysis of the FDA MAUDE Database and the Search for Cobalt Toxicity in Class 3 Johnson & Johnson/DePuy Metal-on-Metal Hip Implants.

INTRODUCTION: This study was designed to determine whether systemic cobalt toxicity as an adverse event could be documented using the Food and Drug Administration's (FDA) Manufacturer and User Facility Device Experience (MAUDE) database for cobalt-chromium containing hip implant recipients. Class 3 Johnson & Johnson (J&J)/DePuy devices were chosen for analysis because of the large number of adverse event reports related to their Pinnacle and ASR XL Acetabular hip replacement systems. A secondary goal was to characterize the reporters who are populating the information in the MAUDE database and to evaluate the quality of the data and information submitted. METHODS: Using FDA MAUDE downloadable data files, 83,528 adverse event medical device narrative reports were identified with the product code of KWA (Prosthesis, Hip, Semiconstrained [Metal Uncemented Acetabular Component]) for J&J/DePuy (KWA Text File). These are class 3 devices and devices with known high failure rates. The ASR XL Acetabular hip replacement Systems and Pinnacle fall into this category. This group of implants was chosen because implant failure is associated with elevated cobalt levels. Two additional subfiles were created from Free Text records in the narrative reports containing key words that indicated a chromium or cobalt (CrCo) device and another for key words indicating elevated levels of cobalt or toxicity. These files were then searched for symptoms of systemic cobalt toxicity with Microsoft Excel using key words pertaining to symptom categories of: cognitive/memory loss, tremor, neuropathy, depression, auditory symptoms, visual symptoms, cardiac, and thyroid disease. Reports are submitted to the FDA at the device component level. It was common for multiple reports to be submitted for a single device. RESULTS: It was not possible to differentiate systemic versus local symptoms for adverse event reports in the neuropathy category. This category was not analyzed. The number of adverse event reports in the other categories ranged from 119 to 16 for the J&J/DePuy KWA Text File and 59 to 4 in the file of records having key words indicating potential elevation of CrCo or toxicity. Cardiac, visual, and auditory conditions were most frequently reported. With the possible exception of cardiomyopathy, the numbers of these reports are far below the prevalence expected in the general population of comparable age. The content of the MAUDE database records often contained little objective data. We found less than 4% of 14,714 records, which indicated cobalt elevation or toxicity contained units for quantitative measurement. There was also frequent use of nondescript, all-encompassing words and phrases such as "mental anguish," found in 321 KWA Text File records. Manufacturers submitted more than 99% of the reports and the most common reporter occupation was attorney, found in 42.24% of the 83,550 J&J/DePuy KWA Reporter File records. Physician was the reporter's occupation in 20.48% of reports but seldom reported directly to the FDA. CONCLUSIONS: We were not able find in the FDA MAUDE database meaningful warning signs to support the contention that chromium-cobalt-containing Class 3 J&J and DePuy hip implants caused systemic neurological or thyroid symptoms in patients. The incidence of reported cardiomyopathy was rare but frequent enough to be cause of concern. The redaction of most patient data along with the nonstructured nature of data entry would be expected to hinder the identification of warning signs. Even identification of the type of device could not be consistently carried out. In addition, the FDA needs to implement a methodology to identify and group all reports from a single device implanted into a patient, so duplication of event counting would not occur. Of 83,550 J&J/DePuy KWA Reporter File records, we found only two physician reports sent directly to the FDA. Almost all reports are submitted by manufacturers and are most commonly authored by attorneys. A standard of care needs to be set for physicians to report medical device adverse events to the FDA.

Disclosing Adverse Events to Patients: International Norms and Trends.

OBJECTIVES: There is a growing expectation in health systems around the world that patients will be fully informed when adverse events occur. However, current disclosure practices often fall short of this expectation. METHODS: We reviewed trends in policy and practice in 5 countries with extensive experience with adverse event disclosure: the United States, the United Kingdom, Canada, New Zealand, and Australia. RESULTS: We identified 5 themes that reflect key challenges to disclosure: (1) the challenge of putting policy into large-scale practice, (2) the conflict between patient safety theory and patient expectations, (3) the conflict between legal privilege for quality improvement and open disclosure, (4) the challenge of aligning open disclosure with liability compensation, and (5) the challenge of measurement related to disclosure. CONCLUSIONS: Potential solutions include health worker education coupled with incentives to embed policy into practice, better communication about approaches beyond the punitive, legislation that allows both disclosure to patients and quality improvement protection for institutions, apology protection for providers, comprehensive disclosure programs that include patient compensation, delinking of patient compensation from regulatory scrutiny of disclosing physicians, legal and contractual requirements for disclosure, and better measurement of its occurrence and quality. A longer-term solution involves educating the public and health care workers about patient safety.

The physiologic basis of spirometry.

Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiological test that measures individual inhalation and exhalation volumes of air as a function of time. Pulmonologists and general-practice physicians commonly use spirometry in their offices in the assessment and management of lung disease. Spirometric indices are well validated and easily interpreted by comparison with established normal values. The remarkable reproducibility of spirometry results from the presence of compliant intrathoracic airways that act as air flow regulators during forced expiration. Because of this anatomic arrangement, expiratory flow becomes dependent solely on the elasticity of the lungs and airway resistance once a certain degree of expiratory force is exerted. Insight into this aspect of respiratory physiology can help in the interpretation of spirometry.

Air-borne and tissue-borne sensitivities of bioacoustic sensors used on the skin surface.

Measurements of body sounds on the skin surface have been widely used in the medical field and continue to be a topic of current research, ranging from the diagnosis of respiratory and cardiovascular diseases to the monitoring of voice dosimetry. These measurements are typically made using light-weight accelerometers and/or air-coupled microphones attached to the skin. Although normally neglected, air-borne sounds generated by the subject or other sources of background noise can easily corrupt such recordings, which is particularly critical in the recording of voiced sounds on the skin surface. In this study, the sensitivity of commonly used bioacoustic sensors to air-borne sounds was evaluated and compared with their sensitivity to tissue-borne body sounds. To delineate the sensitivity to each pathway, the sensors were first tested in vitro and then on human subjects. The results indicated that, in general, the air-borne sensitivity is sufficiently high to significantly corrupt body sound signals. In addition, the air-borne and tissue-borne sensitivities can be used to discriminate between these components. Although the study is focused on the evaluation of voiced sounds on the skin surface, an extension of the proposed methods to other bioacoustic applications is discussed.

Effect of body position on lung sounds in healthy young men.

BACKGROUND: The effect of body position on the generation of abnormal respiratory sounds (eg, snoring and stridor) is well recognized. Postural effects on normal lung sounds have been studied in less detail but need to be clarified if respiratory acoustic measurements are to be used effectively in clinical practice. METHODS: Lung sounds and airflow were recorded in six healthy male subjects. Two acoustic sensors were placed over corresponding sites of the right and left chest, first anteriorly and then on the back. Subjects were studied in sitting, supine, prone, and lateral decubitus positions. Lung sound intensity (LSI) was determined at flows of 0.4 to 0.6 L/s and 0.8 to 1.2 L/s within frequency bands of 150 to 300 Hz and 300 to 600 Hz. RESULTS: LSI was greater over the dependent lungs in the lateral decubitus positions. In the sitting position, LSI was greater on the left compared with the right posterior lung at the same airflow within the same frequency bands. Compared with sitting, neither the supine nor prone positions caused a significant change in LSI. CONCLUSIONS: Our study confirms previously reported asymmetries of normal lung sounds. The insignificant change of flow-specific LSI between the upright and horizontal positions in healthy subjects is encouraging for the clinical use of respiratory acoustic measurements. Further studies should address postural effects on lung sounds in patients with acute lung injury and other lung pathologies.

Transmission of lung sounds through light clothing.

BACKGROUND: Doctors are exhorted to always place the stethoscope directly on the skin and never to auscultate through clothing. Nevertheless, casual observation reveals that doctors and even pulmonologists often violate this principle. OBJECTIVES: This study was designed to evaluate the sensitivity of two common stethoscopes when used through clothing. METHODS: Littmann Classic and Littmann Master Cardiology stethoscopes were studied under conditions of light (60-100 g), medium (240 g) and heavy (555 g) force when placed on a lung sound test platform with one or two layers of cloth (T-shirt material and flannel) interposed between the stethoscope and the test surface. The test platform was designed to mimic the acoustic and mechanical properties of the chest wall and was driven by amplified white noise. The recorded amplitude spectra were compared over a range of 150-1,000 Hz. RESULTS: Compared to the sensitivity on a bare test platform surface, either fabric in single or double layers attenuated the sounds by a mean of 5-18 dB under light pressure. This attenuation was nearly abolished by the addition of either medium or heavy force on the stethoscope head. CONCLUSIONS: The deleterious effect of one or two layers of indoor clothing on lung sounds acquired through a stethoscope can be negated by force on the stethoscope head making effective auscultation possible. Nevertheless, auscultation through clothing remains problematic due to the hindrance to inspection and percussion and the risk of acoustic artifacts caused by clothing.

Design, construction, and evaluation of a bioacoustic transducer testing (BATT) system for respiratory sounds.

Many different transducers are employed for recording respiratory sounds including accelerometers and microphones in couplers. However, there is no standard lung sound transducer or any device to compare transducers so that measurements from different laboratories can be determined to be of physiologic origin rather than technical artifacts of the transducers. To address this problem, we designed and constructed a prototype of a device that can be used to compare accelerometers, microphones enclosed in couplers, and stethoscopes. The prototype device consists of a rigid chamber containing a loudspeaker that opens to an antechamber covered by a viscoelastic material with mechanical properties similar to human skin and subcutaneous tissue. When driven by a white noise source, we found the sound output at the surface to be useful to comparatively evaluate sensors between 100 and 1200 Hz where lung sounds have most of their spectral energy. We compared the viscoelastic layer to similar thicknesses of fresh meat and fat and found them to produce similar acoustic spectra. This device allows air-coupled transducers, accelerometers, and stethoscopes used in respiratory sounds measurements to be compared under physical conditions similar to their intended use.

Comparison of lung sound transducers using a bioacoustic transducer testing system.

Sensors used for lung sound research are generally designed by the investigators or adapted from devices used in related fields. Their relative characteristics have never been defined. We employed an artificial chest wall with a viscoelastic surface and a white noise signal generator as a stable source of sound to compare the frequency response and pulse waveform reproduction of a selection of devices used for lung sound research. We used spectral estimation techniques to determine frequency response and cross-correlation of pulses to determine pulse shape fidelity. The sensors evaluated were the Siemens EMT 25 C accelerometer (Siemens); PPG 201 accelerometer (PPG); Sony ECM-T150 electret condenser microphone with air coupler (air coupler; with cylindrical air chambers of 5-, 10-, and 15-mm diameter and conical air chamber of 10-mm diameter); Littman classic stethoscope head (Littman) connected to an electret condenser microphone; and the Andries Tek (Andries) electronic stethoscope. We found that the size and shape of the air coupler chamber to have no important effect on the detected sound. The Siemens, air coupler, and Littman performed similarly with relatively flat frequency responses from 200 to 1,200 Hz. The PPG had the broadest frequency response, with useful sensitivity extending to 4,000 Hz. The Andries' frequency response was the poorest above 1,000 Hz. Accuracy in reproducing pulses roughly corresponded with the high-frequency sensitivity of the sensors. We conclude that there are important differences among commonly used lung sound sensors that have to be defined to allow the comparison of data from different laboratories.

Fractal branching pattern of the monopodial canine airway.

Unlike the human lung, monopodial canine airway branching follows an irregular dichotomized pattern with fractal features. We studied three canine airway molds and found a self-similarity feature from macro- to microscopic scales, which formed a fractal set up to seven scales in the airways. At each fractal scale, lateral branches evenly lined up along an approximately straight main trunk to form three to four two-dimensional structures, and each lateral branch was the monopodial main trunk of the next fractal scale. We defined this pattern as the fractal main lateral-branching pattern, which exhibited similar structures from macro- to microscopic scales, including lobes, sublobes, sub-sublobes, etc. We speculate that it, rather than a mother-daughter pattern, could better describe the actual asymmetrical architecture of the monopodial canine airway.

John M. Eisenberg Patient Safety Awards. Advocacy: the Lexington Veterans Affairs Medical Center.

BACKGROUND: After the Veterans Affairs Medical Center (VAMC) in Lexington, Kentucky, lost two major malpractice cases in the mid-1980s, leaders started taking a more proactive approach to identifying and investigating incidents that could result in litigation. An informal risk management team met regularly to discuss litigation-prone incidents. During one in-depth review, the team learned that a medication error had caused the patient's death. Although the family would probably never have found out, the team decided to honestly inform the family of exactly what had happened and assist in filing for any financial settlement that might be appropriate. This decision evolved into an organization wide full disclosure policy and procedure. DISCLOSURE POLICY AND PROCEDURE: The Lexington VAMC's policy on full disclosure includes informing patients and/or their families of adverse events known to have caused harm or injury to the patient as a result of medical error or negligence. The disclosure includes discussions of liability and also includes apology and discussion of remedy and compensation. RESULTS: Full disclosure is the right thing to do and the moral and ethical thing to do. Moreover, doing the right thing actually seems to have mitigated the financial repercussions of inevitable adverse events that result in injury to patients. As reported in 1999, Lexington VAMC was in the top quarter of medical centers for number of tort claims filed but was in the lowest quarter for malpractice payouts resulting from these torts.

'Slide whistle' breath sounds: acoustical correlates of variable tracheal obstruction.

We report a case of a man who developed severe shortness of breath and the finding of breath sounds that rose in frequency during inspiration and fell during expiration. These unusual sounds were caused by a spherical tumour arising from the main carina that nearly completely obstructed the distal trachea. The frequency variation disappeared after the removal of the mass. We evaluated this phenomenon using a modelling technique that we had previously developed to analyse the human airways as acoustical tubes. This analysis revealed that the acoustical conditions in the trachea were substantially modified by the presence of the solid mass as the trachea slightly dilated during inspiration, partially relieving the obstruction. Most of the anomalous characteristics of the breath sounds could be explained using this model. We conclude that a detailed understanding of the acoustic conditions of the airways allows correlation with anatomical and physiological conditions and may be of use in diagnosis or evaluation of the airways in health and disease.

Are minidisc recorders adequate for the study of respiratory sounds?

Digital audio tape (DAT) recorders have become the de facto gold standard recording devices for lung sounds. Sound recorded on DAT is compact-disk (CD) quality with adequate sensitivity from below 20 Hz to above 20 KHz. However, DAT recorders have drawbacks. Although small, they are relatively heavy, the recording mechanism is complex and delicate, and finding one desired track out of many is inconvenient. A more recent development in portable recording devices is the minidisc (MD) recorder. These recorders are widely available, inexpensive, small and light, rugged, mechanically simple, and record digital data in tracks that may be named and accessed directly. Minidiscs hold as much recorded sound as a compact disk but in about 1/5 of the recordable area. The data compression is achieved by use of a technique known as adaptive transform acoustic coding for minidisc (ATRAC). This coding technique makes decisions about what components of the sound would not be heard by a human listener and discards the digital information that represents these sounds. Most of this compression takes place on sounds above 5.5 KHz. As the intended use of these recorders is the storage and reproduction of music, it is unknown whether ATRAC will discard or distort significant portions of typical lung sound signals. We determined the suitability of MD recorders for respiratory sound research by comparing a variety of normal and pathologic lung sounds that were digitized directly into a computer and also after recording by a DAT recorder and 2 different MD recorders (Sharp and Sony). We found that the frequency spectra and waveforms of respiratory sounds were not distorted in any important way by recording on the two MD recorders tested.