What are beta blockers and how do they work? Beta blockers, also known as beta-adrenergic blocking agents, are a class of drugs that works by blocking the neurotransmitters norepinephrine and epinephrine from binding to receptors. There are three known types of beta receptors, known as beta1 (Î²1), beta2 (Î²2) and beta3 (Î²3).
Although many newer imaging techniques for the evaluation of lung pathology have been developed, auscultation of the chest remains an invaluable clinical tool and is still probably the most common method of evaluating the lung. Evaluation of lung sounds is a routine part of a clinical examination. Breath sounds can be classified into 2 broad categories: normal breath sounds and adventitious (or abnormal) sounds. Adventitious breath sounds include wheezes, coarse crackles, fine crackles, and rhonchi. See the video of breath sound assessment, below.
Abnormal breath sounds include: the absence of sound and/or ; the presence of normal sounds in areas where they are normally not heard. For example, bronchial (loud & tubular) breath sounds are abnormal in peripheral areas where only vesicular (soft & rustling) sounds should be heard. When bronchial sounds are heard in areas distant from where they normally occur, the patient may have consolidation (as occurs with pneumonia) or compression of the lung. These conditions cause the lung tissue to be dense. The dense tissue transmits sound from the lung bronchi much more efficiently than through the air-filled alveoli of the normal lung. The term âadventitiousâ breath sounds refers to extra or additional sounds that are heard over normal breath sounds.