Information that can be derived from an assessment of the jugular venous pulse includes determination of the mean venous pressure, venous pulse contour, and presence and type of cardiac dysrhythmias. The jugular venous pressure is usually assessed by observing the right side of the patient's neck. The mean jugular venous pressure, determined as the vertical distance above the midpoint of the right atrium, is 6 to 8 cm HO. Deviations from this normal range reflect either hypovolemia (i.e., mean venous pressure less than 5 cm HO) or impaired cardiac filling (i.e., mean venous pressure greater than 9 cm HO). The normal jugular venous pulse contains three positive waves. By convention these are labeled "a," "c", and "v" (Figure 19.1). These positive deflections occur, respectively, before the carotid upstroke and just after the P wave of the ECG (a wave); simultaneous with the upstroke of the carotid pulse (c wave); and during ventricular systole until the tricuspid valve opens (v wave). The a wave is generated by atrial contraction, which actively fills the right ventricle in end-diastole. The c wave is caused either by transmission of the carotid arterial impulse through the external and internal jugular veins by the bulging of the tricuspid valve into the right atrium in early systole. The v wave reflects the passive increase in pressure and volume of the right atrium as it fills in late systole and early diastole. Normally the crests of the a and v waves are approximately equal in amplitude. The descents or troughs (Figure 19.1) of the jugular venous pulse occur between the "a" and "c" wave ("x" descent), between the "c" and "v" wave ("x" descent), and between the "v" and "a" wave ("y" descent). The x and x′ descents reflect movement of the lower portion of the right atrium toward the right ventricle during the final phases of ventricular systole. The y descent represents the abrupt termination of the downstroke of the v wave during early diastole after the tricuspid valve opens and the right ventricle begins to fill passively. Normally the y descent is neither as brisk nor as deep as the x descent. in the jugular venous pulse may be reflected in either the mean pressure, amplitude, or configuration of the positive waves or negative troughs, or in the sequence or absence of the positive waves. In this chapter emphasis is placed on measurement of the jugular venous pressure, use of the venous pulse to determine cardiac rhythm, and the more common cardiac problems of pulmonary hypertension, tricuspid regurgitation, and constrictive pericarditis.
通过评估颈静脉搏动可获得的信息包括确定平均静脉压、静脉搏动轮廓以及心律失常的存在和类型。通常通过观察患者颈部右侧来评估颈静脉压。平均颈静脉压是指高于右心房中点的垂直距离，为6至8厘米水柱。偏离此正常范围反映血容量不足（即平均静脉压低于5厘米水柱）或心脏充盈受损（即平均静脉压高于9厘米水柱）。正常的颈静脉搏动包含三个正向波。按照惯例，这些波分别标记为“a”、“c”和“v”（图19.1）。这些正向偏移分别发生在颈动脉搏动上升之前以及心电图P波之后（a波）；与颈动脉搏动上升同时出现（c波）；以及在心室收缩期直至三尖瓣开放期间（v波）。a波由心房收缩产生，在舒张末期主动充盈右心室。c波是由颈动脉搏动通过颈外静脉和颈内静脉传导，或者是由于收缩早期三尖瓣突入右心房所致。v波反映了右心房在收缩末期和舒张早期充盈时压力和容积的被动增加。正常情况下，a波和v波的波峰幅度大致相等。颈静脉搏动的下降或波谷（图19.1）出现在“a”波与“c”波之间（“x”下降）、“c”波与v波之间（“x”下降）以及“v”波与“a”波之间（“y”下降）。x和x′下降反映在心室收缩末期右心房下部向右侧心室的移动。y下降代表在三尖瓣开放且右心室开始被动充盈后的舒张早期v波下降突然终止。正常情况下，y下降不如x下降那样迅速和深切。颈静脉搏动的变化可能反映在平均压力、正向波或负向波谷的幅度或形态上，或者反映在正向波的顺序或缺失上。在本章中，重点在于颈静脉压的测量、利用静脉搏动确定心律，以及肺动脉高压、三尖瓣反流和缩窄性心包炎等更常见的心脏问题。
