Wet rales are due to the thin liquid in the trachea or bronchus, such as exudate sputum, blood, mucus pus sputum, etc., in the breathing gas through the liquid, the formation of blisters rupture and produce sound, that is, blister sound. Mostly appear during inspiration, or more clearly at the end of inspiration, sometimes can also appear in the early exhalation site and the nature of more constant. Differential diagnosis: 1, the distinction between wet rales and pleural friction sounds dry pleurisy, the surface is rough, the wall layer and the dirty layer of pleura rubbing against each other during breathing is the sound of pleural friction, easy to confuse with wet rales during auscultation, pleural friction sounds can be heard during expiration and inspiration, disappear when holding breath, the sound is often clearer during deep breathing or pressure, palpation has a sense of pleural friction, coughing can not change its nature. Coughing can not change its nature, often accompanied by chest pain, while wet rales appear more often during inspiration, or more clearly at the end of inspiration, coughing can sometimes disappear, the two to distinguish. 2, the distinction between wet rales and pericardial friction sounds pericarditis wall layer and dirty layer of the pericardial surface rough, in the process of heart diastole and contraction of the two layers of inflamed pericardium rubbing against each other and produce sound for pericardial friction sounds, sometimes similar to pleural friction sounds and wet rales, while the occurrence of pericardial friction sounds and heart activity, not related to respiratory movements, breath-holding is also present, systolic to diastolic can be heard, sometimes only in systole These are its characteristics, so it is distinguished from wet rales. 3. When there is a subcutaneous emphysema in the chest, a sound similar to the twisting of hair can be heard during auscultation, which is similar to wet rales, but this sound can be heard during both expiration and inspiration, and the gas can also form a sound when the hand is pressed and displaced in the tissue under this, just like the sense of twisting hair or grip snow. Subcutaneous emphysema can spread from the chest wall to the neck, abdomen, upper limbs and other parts of the body, so it can be distinguished from wet rales.