Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Nursing

Major Professor

Cindy Munro, Ph.D., RN, ANP-BC, FAANP, FAAN, FAAAS

Co-Major Professor

John Clochesy, Ph.D., RN

Committee Member

Zhan Liang, Ph.D., RN

Committee Member

Karel Calero, M.D.

Committee Member

Ming Ji, Ph.D.

Keywords

geriatrics,, sleep efficiency, sleep fragmentation, grip strength, post-intensive care, mechanical ventilation

Abstract

The primary, descriptive aim of this dissertation was to describe the nighttime sleep quality of previously mechanically ventilated older adult patients within 24-48 hours of transfer out of the intensive care unit (ICU) to a medical-surgical floor. The secondary, exploratory aim was to examine the relationships between post-ICU sleep efficiency (SE) and wake after sleep onset (WASO) with grip strength in previously mechanically ventilated older adult patients within 24-48 hours of transfer out of the ICU.

The study included 30 adults ages 65 and older (11 women, 19 men; age 71.37 ± 5.35, range 65-86 years), who were functionally independent at home prior to hospitalization, mechanically ventilated during their ICU stay, and were within 24-48 hours of transfer out of ICU to a medical-surgical floor at Tampa General Hospital, a level 1 trauma center. Subjects wore an actigraph monitor on the dominant wrist (Actiwatch Spectrum) to monitor sleep over two consecutive nights. Parameters of post-ICU sleep quality included total sleep time (TST), sleep efficiency (SE), wake after sleep onset (WASO), sleep latency (SL), and number of awakenings (NA). The outcome measure of motor function was dominant hand grip strength, assessed by the National Institutes of Health Toolbox Motor Battery Grip Strength Test. Sleep data collected between nighttime hours (9:00 PM to 9:00 AM) on both nights were analyzed. For the descriptive aim, means for each sleep parameter and clinical characteristics were reported. For the exploratory aims, multiple regression analyses examined the individual associations between mean sleep parameters (SE and WASO) and grip strength.

Study subjects had a mean SE of 63.24 ± 3.88% and spent 135.39 ± 9.94 minutes awake after sleep onset. The mean TST among subjects was 7.55 ± 2.52 hours, ranging from 2.02 to 10.84 hours of sleep, out of the 12 hours of total time in bed. A total of 6 (20%) subjects slept less than 5 hours each night, and a total of 6 (20%) subjects slept greater than 10 hours each night. The mean SL among study subjects was 42.57 minutes, and ranged from 0.0 to 237.75 minutes. Overall, subjects’ average NA was 78.28 ± 26.39, ranging from 35 to 136 awakenings.

In multiple regression analysis, SE was significantly and negatively associated with grip strength, after adjusting for potential confounding factors. The model predictors explained 80.8% of the variance in grip strength, [R2 = .808, F(10, 15) = 6.324, p = .001]. Higher SE independently predicted worse grip strength (β = -0.326, p = .036). Further, among the tertiles of subjects with moderate or high TST (sleep duration ≥ 6 hours, n = 23), there remained a significant, negative association between SE and grip strength. The predictors explained 73.7% of the variance in grip strength, [R2 = .737, F(5, 15) = 8.416, p = .001]. Higher SE independently predicted worse grip strength among the subset of subjects with moderate or high sleep duration (β = -0.296, p = .046). Among the two quartiles of subjects with moderate-high or high WASO (≥ 120 minutes spent awake after sleep onset, n = 16), there was a significant, negative association between WASO and grip strength, after adjusting for covariates. The model indicated that the predictors explained 91.4% of the variance in grip strength [R2 = .914, F(6, 8) = 14.134, p = .001]. Greater WASO independently predicted worse grip strength (β = -0.276, p = .04). Finally, the effects of sex and preexisting obstructive sleep apnea (OSA) on grip strength were individually examined. Higher SE independently predicted worse grip strength among male subjects (β = -0.353, p = .039), as did preexisting OSA (β = -0.493, p = .033).

In summary, objectively measured sleep quality was disturbed among previously mechanically ventilated, hospitalized older adults, even after transfer out of ICU to a medical-surgical floor. Longer TST and greater SE predicted worse grip strength among these frail patients who were previously independent, community dwelling older adults. Among the subjects with more severely fragmented sleep, WASO also independently predicted weaker grip strength. As poor grip strength is an indicator of ICU-acquired weakness, optimal sleep duration and less sleep disturbances may be crucial in prevention of worse functional outcomes and new institutionalization. Additional research is needed to discern the temporality of associations between sleep quality and motor function among older adult survivors of critical illness.

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