Background questions
These clinical questions are about physiology, pathology, epidemiology, and general management and are often asked by clinicians in training. The answers to background questions are often best found in textbooks or narrative review articles.

Barrel chest sign
The anterior-posterior dimension of the chest increases in relation to the lateral dimensions, giving the shape of a barrel. This occurs in conditions that result in hyperinflation of the lung.

Barthel Index
The Barthel Index, originally designed for older patients, assesses ability to transfer from bed to chair or commode, bowel and bladder function, and other aspects of self-care. For more information, see the following Web site for the index: http://www.strokecenter.org/trials/scales/barthel_reprint.pdf.

Base case
In an economic evaluation, the base case is the best estimates of each of the key variables that bear on the costs and effects of the alternative management strategies.

Baseline characteristics
Factors that describe study participants at the beginning of the study (eg, age, sex, disease severity); in comparison studies, it is important that these characteristics be initially similar between groups; if not balanced or if the imbalance is not statistically adjusted, these characteristics can cause confounding and can bias study results.

Baseline risk
The proportion or percentage of study participants in the control group in whom an adverse outcome is observed. See also Absolute risk.

Bayesian analysis
An analysis that starts with a particular probability of an event (the prior probability) and incorporates new information to generate a revised probability (a posterior probability). The approach to diagnosis assumes that diagnosticians are intuitive Bayesian thinkers and move from pretest to posttest probabilities as information accumulates.

Baystate Quality of Dying Score
The Baystate Quality of Dying Score is a measure of the quality of end-of-life care in renal dialysis patients and comprises 5 domains (pain, nonpain symptoms, advance care planning, peacefulness, and time) that are scored and then summed. For more information, see the following article for the scoring: Spital A (ed.). Ethical issues in dialysis. Measuring quality of dying in end-stage renal disease. Semin Dialysis. 2008;17(5):376-379.

Beck triad
The classic findings of tamponade as described in 1935 by thoracic surgeon Claude Schaeffer Beck are characterized by decreasing arterial blood pressure, increasing jugular venous pressure, and a small, quiet heart.

Before-after design
Study in which the investigators compare the status of a group of study participants before and after the introduction of an intervention. See also Crossover study.

Bereavement
The response to loss, particularly to the loss of someone to whom a bond was formed. Also known as grief.

Bias
A systematic error in the design, conduct, or interpretation of a study that may cause a systematic deviation from the underlying truth (eg, overestimation of a treatment effect because of failure to randomize).

Biphasic positive airway pressure (BiPAP)
A method of respiratory ventilation using a tightly fitted face mask primarily used for critically ill hospital patients with respiratory failure, often as a temporizing measure to avoid the need for intubation and mechanical ventilation.

Blind
Patients, clinicians, data collectors, outcome adjudicators, or data analysts unaware of which patients have been assigned to the experimental or control group. In the case of diagnostic tests, those interpreting the test results are unaware of the result of the reference standard or vice versa. See also Concealment.

Boas sign
Originally, this sign referred to point tenderness in the region to the right of the 10th to 12th thoracic vertebrae, but contemporary sources describe hyperesthesia to light touch in the right upper quadrant or infrascapular area.

Body image
A person’s perception of his/her physical body.

Bonacini cirrhosis discriminant score (CDS)
A score used to help determine the likelihood of cirrhosis. Combines the aspartate aminotransferase:alanine aminotransferase ratio with the platelet count and prothrombin international normalized ratio into a discriminant function with possible total values between 0 and 11; higher values are associated with an increased likelihood of cirrhosis.

Boolean operators
Words used when searching electronic databases. These operators are AND, OR, and NOT and are used to combine terms (AND/OR) or exclude terms (NOT) from the search strategy.

Bootstrap technique
A statistical technique for estimating parameters such as standard errors and confidence intervals based on resampling from an observed data set with replacement from the original sample.

Bordetella pertussis
The bacteria that causes whooping cough or pertussis.

Brachytherapy
A type of radiotherapy in which the source of radiation is placed (or implanted) in or close to the area being treated.

Brain death
The irreversible cessation of all functions of the entire brain, including the brainstem.

Bridge program
A bridge program is provided by a hospice in collaboration with a home health agency or other health care service provider that offers pain and symptom management and emotional support during a period when a patient with a life-limiting condition may still be pursuing active treatment or is not yet ready to enroll in a hospice.

Bridges to Health model
The Bridges to Health model identifies the following categories of patient care as the anchoring principles for designing efficient and effective services: healthy, acutely ill, maternal/infant, serious long-term disability, chronic illness consistent with normal social role, and the following 3 trajectories, which represent the trajectories of people living with disabling, progressive, and eventually fatal conditions: those with “terminal cancer,” those with chronic organ system failure, and those with progressive disability (such as dementia or frailty) in old age. For more information, see the following article for the model: Lynn J, Straube BM, Bell KM, Jencks SF, Kambic RT. Using population segmentation to provide better health care for all: the “Bridges to Health” model. Milbank Q. 2007;85(2):185-212. [PMID: 17517112]

Brief Fatigue Inventory
A fatigue assessment tool that asks patients to rate, on a scale of 0 (none) to 10 (severe), their current level of fatigue, usual fatigue level in the last 24 hours, worst level of fatigue in the last 24 hours, and how fatigue has interfered with general activity, mood, walking, work, relationships, and enjoyment of life. For more information, see the following article for the inventory: Mendoza TR, Wang XS, Cleeland CS, et al. The rapid assessment of fatigue severity in cancer patients: Use of the Brief Fatigue Inventory. Cancer. 1999;85:1186-1196. [PMID: 10091805]

Brief Pain Inventory
A pain assessment tool that asks patients whether they have any pain now and, if so, where it is located; to rate, on a scale of 0 (none) to 10 (severe) their level of pain in the last 24 hours (worst, least, average); current level of pain; treatments for pain and how much they have relieved the pain; and how pain has interfered with general activity, mood, walking, work, relationships, and enjoyment of life.

Bronchiolitis
Inflammation of the bronchioles.

Brudzinski sign
Meningeal inflammation and irritation that elicits a protective reflex to prevent stretching of the inflamed and hypersensitive nerve roots, which is detectable clinically as neck stiffness or Kernig or Brudzinski signs. A Brudzinski sign (also known as the "nape of the neck" sign) is present when passive neck flexion in a supine patient results in flexion of the knees and hips.

Buerger test
The clinician examines for development of pallor with the patient's leg elevated to 90° with the patient lying supine. The leg is then lowered slowly and the angle at which the reddish hue returns is known as the “angle of circulatory sufficiency”; the result is positive if the angle is less than 0° (ie, hangs below the examining table).

Burnout
A form of mental distress manifested in normal individuals by decreased work performance, resulting from negative attitudes and behaviors. In end-of-life care, burnout often results from stresses that arise from the clinician’s interaction with the work environment.