Biomedical subjects

Charles Ho

Publications and source records attributed to Charles Ho.

8 recordsLinked to original sources

PubMed2005

Use of standards in the review of medical devices.

In keeping with its mandate to provide the least burdensome means of product regulation, the US Food and Drug Administration's (FDA) Center for Devices and Radiological Health uses many different standards to facilitate the review of premarket submissions of medical devices. The benefits of using standards in this manner include providing a set of common requirements and test protocols to the device manufacturer, thus reducing the manufacturer's need to "reinvent the wheel" for each new bench test to ensure safety and effectiveness of the device. With the current trend toward international harmonization of standards, tests performed in accordance with an international standard may be acceptable to several countries. However, there are instances in which the FDA does not agree with certain provisions in a standard. This article aims to clarify the approaches taken by the FDA to balance or resolve issues that arise when there is disagreement regarding the acceptability of a particular standard. One approach begins with the recognition of only some provisions of a standard, or more commonly, excluding those parts of a standard that are unacceptable to the FDA for regulatory or scientific validity reasons. Other approaches include working with the standards development organizations to revise the standard to include language more agreeable to all parties involved. Specific examples will be presented on medical devices, such as electrocardiogram cables and connectors, and noninvasive blood pressure monitors.

Device Approval↗

PubMed2004

Regulatory issues for computerized electrocardiographic devices.

Computerized electrocardiogram (ECG) devices are regulated in the U.S. by the FDA Center for Devices and Radiological Health (CDRH). This article aims to highlight the salient points of the FDA regulatory review process, including the important distinction between a "tool" claim and a "clinical" claim in the intended use of a computerized ECG device. Specifically, a tool claim relates to the ability of the device to accurately measure a certain ECG parameter, such as T-wave alternans (TWA), while a clinical claim imputes a particular health hazard associated with the identified parameter, such as increased risk of ventricular tachyarrhythmia or sudden death. Given that both types of claims are equally important and receive the same regulatory scrutiny, the manufacturer of a new ECG diagnostic device should consider the distinction and regulatory pathways for approval between the two types of claims discussed in this paper.

Death, Sudden, Cardiac↗

PubMed2004

Advances in ambulatory monitoring: regulatory considerations.

Conventional ambulatory electrocardiogram (ECG) (Holter) monitoring involves 2 or 3 surface leads recorded with electrode positions and signal characteristics that are different from diagnostic quality 12-lead ECGs due to the limitations imposed by technology on the ambulatory recorders. The rapid pace of technological development for medical devices, particularly electrocardiography, has now enabled the recording of diagnostic quality 12-lead ECG waveforms for extended time periods. This capability allows Holter recording to become another source for diagnostic 12-lead ECG records on a par with other modalities such as resting ECG and exercise stress testing. Additionally, other diagnostic techniques such as S-T segment analysis and Q-T interval analysis that rely on diagnostic quality waveforms can now be applied. All of these enhancements to the traditional Holter modality have altered the regulatory perspective of these devices, since the enhancements may represent a new intended use for the device.

Biomedical Engineering↗

PubMed2004

Asymptomatic tibial stress reactions: MRI detection and clinical follow-up in distance runners.

OBJECTIVE: The purpose of this study was twofold: to determine if asymptomatic elite distance runners exhibit stress reactions of the tibia on MR images and to determine if the presence of bone stress lesions predicts later development of symptomatic tibial stress injuries. CONCLUSION: Signs of a tibial stress reaction were found on MRI in 43% of the 21 asymptomatic college distance runners in this study. The presence of these changes was not found to be a predictor of future tibial stress reactions or stress fractures. Our findings underscore the importance of correlating MRI findings with clinical findings before making therapeutic decisions.

Adolescent↗

PubMed2003

Issues in using databases of pre-recorded physiological signals to test medical devices.

Bench testing with databases of pre-recorded physiological signals is a common step in the verification and validation of medical devices. For example, in the case of an electrocardiographic (ECG) monitor to be tested, the physiological signals are ECG tracings that have previously been recorded from patients using other ECG monitors. Human overreaders then annotate the tracings to determine the occurrence of significant clinical events such as ventricular tachycardia. These annotations can be used to determine the sensitivity and specificity of the ECG monitor to be tested. This article aims to highlight some issues associated with such bench testing, such as the way the pre-recorded signals are presented to the medical device to be tested, the adequacy of single channel versus dual channel versus multi-channel testing in the bench testing, and the need for the human overreaders and the medical device to use the same set of rules for determining the occurrence of a clinical event. These issues are also applicable to other monitors such as the apnea monitor. Some suggestions for addressing the issues are presented.

Analog-Digital Conversion↗

PubMed2002

Discitis associated with pregnancy and spinal anesthesia.

UNLABELLED: Discitis (inflammation of the intervertebral disk) most commonly develops as a rare complication of bacterial infection or chemical or mechanical irritation during spine surgery (1) with a postoperative incidence of 1%-2.8% (2). It is also a complication of discography-the intradiscal injection of saline or contrast material (3). The incidence of postdiscography discitis is 1%-4% (3); no cases have been reported when prophylactic antibiotics have been used, supporting the theory of bacterial contamination (3). Although it is controversial whether discitis can be caused by an aseptic or infectious process, recent data suggest that persistent discitis is almost always bacterial (4). Honan et al. (5) reported 16 cases of spontaneous discitis and reviewed another 52 patients from the literature. In their series, patients tended to have one or more comorbid conditions, such as diabetes, vertebral fracture, or a preexisting spine injury. Spontaneous discitis has also been associated with advanced age, IV drug abuse, IV access contamination, urinary tract infection, and immunocompromised states (5,6). No cases of infectious discitis associated with pregnancy and spinal anesthesia have been reported in the English literature. Discitis presents as spasmodic pain in the back that may be referred to the hips or groin (7). The pain may radiate to the lower extremities. The erythrocyte sedimentation rate is usually increased. Radiological changes in discitis include narrowing of the intervertebral disk space, vertebral sclerosis, and erosion of the end plates. The best diagnostic measure may be magnetic resonance imaging (MRI) or a combination of bone and gallium scanning (2). The mainstay for discitis treatment is pain control and antibiotics; surgical intervention is usually not required. Complications of discitis include intervertebral fusion, epidural abscess, and paralysis. IMPLICATIONS: This is a case report of a disk infection (discitis) caused by the bacteria, Streptococcus bovis after spinal anesthesia for cesarean delivery. S. bovis rarely causes discitis, and spinal anesthesia for labor and delivery has not been reported as a cause of discitis.

Adult↗

PubMed2002

Challenges in designing a multi-function patient monitor.

This article presents a discussion of some challenges in the design of a multi-function patient monitor. The term "multi-function patient monitor" refers to a single medical device that monitors multiple physiological parameters from the same patient. A common configuration of the monitor is a personal computer (PC) platform communicating with several modules each designed to monitor one physiological parameter. Although such an integration of modules allows the modules to access to the display screen, keyboard, power supply and printer of the PC, the integration also involves new design challenges. The foremost challenge is the increased demand on the PC's resources, while another challenge is compatibility among the various modules. Examples of compatibility are electromagnetic compatibility, and clinical compatibility. A well-known example of incompatibility is the non-invasive blood pressure monitor cuff cutting off blood flow to the finger with a pulse oximeter probe, resulting in a Low Signal alarm in the pulse oximeter. Other challenges include clutter on the display screen and confusing alarm annunciation. This article discusses these design challenges and proposes some solutions based on engineering principles, and common sense considerations. Examples will also be drawn from case reports available in the public domain.

Blood Pressure Monitors↗

PubMedDate not supplied

Accuracy of magnetic resonance imaging in determining the presence and size of recurrent rotator cuff tears.

We attempted to assess the accuracy of magnetic resonance imaging (MRI) in determining the size of recurrent cuff tears in correlation with size measured at surgery. Thirty-seven shoulders in 33 patients who had reoperation for a presumed failed rotator cuff repair were retrospectively evaluated. All patients had preoperative MRI, the results of which were read by a musculoskeletal radiologist to determine the presence of a tear and to estimate its size. All tears were measured intraoperatively in sagittal and coronal planes. Thirty-three shoulders had recurrent tears of the rotator cuff, and MRI correctly identified the presence of 30 of them. MRI correctly identified only 1 of the 4 patients without a recurrent tear of the cuff. The correlation coefficient for MRI accurately defining the size of cuff tears was 0.46. The sensitivity of MRI for the diagnosis of retear was 91%, and the specificity was 25%. MRI is accurate in diagnosing a recurrent full-thickness cuff tear in postsurgical shoulders. However, it is relatively inaccurate in correctly defining the size of the tear. MRI also has a tendency to overdiagnose cuff tears in postsurgical patients with continued pain and symptoms.

Humans↗