Object: Blood pressure is a biorhythm that is primarily exogenous, responds to cues, and has a diurnal pattern characterized by a daytime peak and a nighttime trough. The effect of changing environmental cues such as light-dark cycles on blood pressure is not well documented. This exploratory study identified the patterns of blood pressure in nonsurgical patients in an intensive care unit. The following research questions were addressed: 1. Does the diurnal pattern of blood pressure synchronize with the environment in nonsurgical patients who are in an intensive care unit? and 2. Does the diurnal pattern of blood pressure phase shift in nonsurgical patients who are in an intensive care unit environment? Design: In this exploratory study, a time series design was used to assess the environmental effects of an intensive care unit on the patterns of blood pressure. Population, Sample, Setting, Years: The study was conducted in a 10 bed medical surgical intensive care unit (ICU). Ten subjects, 3 females (30%) and 7 males (70%) who did not have congestive heart failure or recent surgery comprised the study. Ages ranges from 30 to 77 years with a mean are of 54.9 (+,- 15.23). Variable Studied: Blood pressure patterns in nonsurgical patients and environmental factors such as sleep-wake cycles and light-dark cycles were studied Method: Blood pressure readings were monitored with a printout and collected every 24 hours by the researcher along with information about the environment using the "Patients Activity" form. The blood pressure printout and the "Patient Activity" form were coded to ensure patient confidentiality. Data were collected for no less than 48 hours and no more than 72 hours. Blood pressure data were analyzed using cosinor rhythmometry and cosinor analysis to determine the presence of significant circadian rhythmicity and the acrophase of the rhythm, autocorrelation to determine cycle length and stability, and percentage rhythmicity to determine synchrony of blood pressure with the environment. Environmental information concerning lights on and off along with sleep interruption was also collected and related anecdotally related to each subject. Findings: Results from the analyses indicated that although significant circadian rhythms were present in the majority of subjects the usual diurnal pattern was altered by being either lengthened or attenuated. Percentage rhythmicity indicated no synchrony with the environment. Phase shifts were noted in the majority of the subjects indicating that the time of the peak blood pressure was altered from the expected time. Conclusions: It was concluded that nonsurgical patients in an ICU experienced not only disruption of the diurnal cycle length but also had phase shifts in both systolic and diastolic blood pressure related to sleep disruptions and a constant lighted environment. . It was also concluded that inactivity, such as being on bed rest, may play a role in desynchronizing systolic and diastolic blood pressure in patient in an ICU. Implications: 1.Nurses can potentially play a role in helping to maintain synchrony of the biorhythmic pattern of blood pressure readings in an ICU environment 2. Disruption of sleep should be minimized to ensure that a normal sleep pattern is maintained. 3. Nursing and patient activities should be scheduled or carried out mostly during daytime hours when the patients are less likely to sleep. 4. An environmental assessment of patients’ sleep-wake cycles, mealtime, activity (type and time), and lighting should be performed. This information can be used to simulate a home environmental, which may assist in maintaining blood pressure pattern synchrony.
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