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.
Respiratory sounds, breath sounds, or lung sounds refer to the specific sounds generated by the movement of air through the respiratory system.These may be easily audible or identified through auscultation of the respiratory system through the lung fields with a stethoscope. Usually it is due to a blockage of airflow in the windpipe (trachea) or in the back of the throat. 2  Wheezing: High-pitched sounds produced by narrowed airways. 3  They are most often heard when a person breathes out (exhales).