| Description |
This study compared arterial blood pressure measurements obtained from analog recordings with those obtained from bedside monitor digital displays. Baseline arterial blood pressure waveforms were sampled in a clinical intensive care unit, using waveforms which were chosen to be representative of a variety commonly encountered clinically. The waveforms were then analyzed using three different bedside monitors. The results indicate that there can be considerable differences between the analog waveform and digital monitor measurements of systolic, diastolic, and mean arterial blood pressure. The magnitude of difference varies depending on the type of waveform, the specific pressure being monitored (systolic, diastolic, or mean), and the monitor used. Three monitors were tested: an older Hewlett Packard (HP) monitor (#782050 - introduced in the early 1970s), the Marquette monitor (7000), and the new Hewlett Packard (HP) monitor (#78534A - introduced in 1983). Clinically important differences (greater than or equal to 5 mm Hg) were as follows: The differences between the analog and digital readings seen on the older Hewlett Packard monitor were the larges and occurred more frequently than on either of the other two monitors evaluated. The systolic pressure showed differences in all categories except normal (range = 7.4 - 15.4 mm Hg). The diastolic pressure showed differences with pulsus paradoxus, arrhythmias, and artifact (range = 5.2 - 5.5 mm Hg). The mean arterial pressure showed differences with hypertension, pulsus paradoxus, arrhythmias, artifact, and overall (range = 5.3 - 10.0 mm Hg). For the Marquette monitor, a difference between the analog and digital systolic pressure was seen with hypotension, hypertension, arrhythmias, and artifact (range = 5.4 - 6.5 mm Hg). The only difference for the diastolic pressure was with artifact (5.7 mm Hg). The mean arterial pressure showed differences with hypertension, arrhythmias, artifact, and an overall category which combined all other categories (range = 5.0 - 7.8 mm Hg). For the newer Hewlett Packard monitor, the systolic and diastolic pressures showed a difference between the analog and digital measurements only with artifact (range = 5.7 - 8.3 mm Hg). The mean arterial pressure showed differences with normal arterial blood pressures, hypertension, and artifact (range = 5.2 - 8.3 mm Hg.) The digital display or arterial pressure monitors may differ considerably from the analog arterial pressure measurements. When a wave form other than normal is monitored, analog strip recordings should be done to validate the digital display. Another implication concerns the automatic sampling and acquisition of blood pressure data. When an arterial waveform with a configuration that varies from normal is being monitored, analog strip recordings should be done to validate the digital display. If the difference between the analog and digital readings is clinically important, the data which have been automatically sampled should not be used to guide the evaluation and treatment of a patient. Finally, the importance of validating bedside pressure monitors with clinical data was demonstrated. |
