Which of the following shows the correct asymmetrical alarm widths for arterial and venous lines?

• A. Arterial width 100; Venous width 120
• B. Arterial width 120; Venous width 100
• C. Arterial width 110; Venous width 90
• D. Arterial width 130; Venous width 110

Answer: (B)

The main idea is that alarm widths represent how much deviation from the setpoint you’ll tolerate before sounding an alarm. These widths are not the same for arterial and venous lines because their pressures behave differently during dialysis.

The arterial line experiences more rapid and larger fluctuations due to the needle/catheter dynamics, pump interactions, and vascular movement. To prevent frequent nuisance alarms from normal arterial pressure swings, the arterial alarm width is made larger. The venous line, on the other hand, tends to be more stable, so a tighter (narrower) alarm width helps catch real trouble like occlusions or abnormal return pressure more promptly.

Therefore, the chosen combination—arterial alarm width larger (120) and venous alarm width smaller (100)—reflects this asymmetry: more tolerance on the arterial side and tighter monitoring on the venous side.