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.
Normal breath sounds vary according to the diameter of the airways. For example, anteriorly over the trachea, you should hear a loud, high-pitched, hollow sound called a bronchial breath sound. It is abnormal to hear this sound over peripheral lung tissue, that is, away from the trachea and the large bronchi.Over the mainstem bronchi, which are relatively large-diameter airways, you should hear medium-pitched and quieter sounds, called bronchovesicular breath sounds.t is abnormal to hear this sound over peripheral lung tissue, that is, away from the trachea and the large bronchi. Over the mainstem bronchi, which are relatively large-diameter airways, you should hear medium-pitched and quieter sounds, called bronchovesicular breath sounds.