Cardiorespiratory instability before and after implementing an integrated monitoring system

Abstract

Objectives: Cardiorespiratory instability may be undetected in monitored step-down unit patients. We explored whether using an integrated monitoring system that continuously amalgamates single noninvasive monitoring parameters (heart rate, respiratory rate, blood pressure, and peripheral oxygen saturation) into AN instability index value (INDEX) correlated with our single-parameter cardiorespiratory instability concern criteria, and whether nurse response to INDEX alert for patient attention was associated with instability reduction.

Design: Prospective, longitudinal evaluation in sequential 8-, 16-, and 8-wk phases (phase I, phase II, and phase III, respectively).

Setting: A 24-bed trauma step-down unit in single urban tertiary care center.

Patients: All monitored patients.

Interventions: Phase I: Patients received continuous single-channel monitoring (heart rate, respiratory rate, blood pressure, and peripheral oxygen saturation) and standard care; INDEX background was recorded but not displayed. Phase II: INDEX was background-recorded; staff was educated on use. Phase III: Staff used a clinical response algorithm for INDEX alerts.

Measurement and main results: Any monitored parameters even transiently beyond local cardiorespiratory instability concern triggers (heart rate of <40 or >140 beats/min, respiratory rate of <8 or >36 breaths/min, systolic blood pressure of <80 or >200 mm Hg, diastolic blood pressure of >110 mm Hg, and peripheral oxygen saturation of <85%) defined INSTABILITYmin. INSTABILITYmin further judged as both persistent and serious defined INSTABILITYfull. The INDEX alert states were defined as INDEXmin and INDEXfull by using same classification. Phase I and phase III admissions (323 vs. 308) and monitoring (18,258 vs. 18,314 hrs) were similar. INDEXmin and INDEXfull correlated significantly with INSTABILITYmin and INSTABILITYfull (r = .713 and r = .815, respectively, p < .0001). INDEXmin occurred before INSTABILITYmin in 80% of cases (mean advance time 9.4 ± 9.2 mins). Phase I and phase III admissions were similarly likely to develop INSTABILITYmin (35% vs. 33%), but INSTABILITYmin duration/admission decreased from phase I to phase III (p = .018). Both INSTABILITYfull episodes/admission (p = .03) and INSTABILITYfull duration/admission (p = .05) decreased in phase III.

Conclusion: The integrated monitoring system INDEX correlated significantly with cardiorespiratory instability concern criteria, usually occurred before overt instability, and when coupled with a nursing alert was associated with decreased cardiorespiratory instability concern criteria in step-down unit patients.

Figure 1

The University of Pittsburgh Medical Center clinical decision rules for Visensia red alerts. VSI, Visensia Index; MET, medical emergency treatment; HR, heart rate; BP, blood pressure; RR, respiratory rate; SpO₂, peripheral oxygen saturation; MD, medical doctor; CRNP, certified registered nurse practitioner; PA, physician assistant; VS, vital sign.

Figure 2

Comparison of the cumulative number of occurrences in which patients were across the thresholds of instability concern criteria for each phase (A), and cumulative duration of time in which patients were across the thresholds (B). hit, vital-sign-monitoring parameters across instability concern thresholds for any cause, including artifact; min, subset of hit for instability that was physiologically real (i.e., nonartifactual) even if transient; full, subset of min for instability judged as serious and persistent and in need of intervention; INSTABILITY, vital sign monitoring parameters were beyond instability-concern thresholds.

Figure 3

Comparisons of instability for only patients who experienced it in phase 1 (black bars) and phase 3 (gray bars). The percentages of admissions in each phase are compared with respect to the number of times each individual went beyond the instability concern threshold (top row) and the duration of time each individual spent in an instability state (bottom row). hit, vital-sign-monitoring parameters across instability concern thresholds for any cause, including artifact; min, subset of hit for instability that was physiologically real (i.e., nonartifactual) even if transient; full, subset of min for instability judged as serious and persistent and in need of intervention; INSTABILITY, vital sign monitoring parameters were beyond instability-concern thresholds.

Figure 4

Example from phase 1 of cyclic nature of instability episodes ramping upward to form instability events, which can be unrecognized in the early stages with only intermittent observation. A, The patient begins to have decrease in SpO₂ shortly after 2:30 AM, which triggers tachypnea and resultant rise in heart rate briefly. B, Between 6:00 AM and 9:00 AM, SpO₂ persistently trends downward. C, Between 10:00 AM and 2:30 PM, there are five bouts of instability episodes. VSI, Visensia Index; HR, heart rate; BP, blood pressure; RR, respiratory rate; SpO₂, peripheral oxygen saturation.