A disturbed sleep pattern of patients after open heart surgery has been reported. Neuman's Health Care System Model was the conceptual framework for this study in which a particular nursing prevention, self selected monotonous sounds, was used to aid the patient in assimilation and accommodation to the environment, in an effort to strengthen the patient's resistant forces to intrapersonal, interpersonal, and extrapersonal stressors.

The purpose of this study was to investigate the influence of self-selected monotonous sound (white noise) on the night sleep pattern of postoperative open heart surgery patients. Sixty men and women ages 29 to 69 years, having coronary artery bypass surgery for the first time, were randomly assigned to an experimental group or a control group. A two group pretest-posttest control group was the study design. The Richards-Campbell Sleep Questionnaire was used to depict scores of usual sleep at home and sleep after 3 nights posttransfer out of the intensive care unit. In the experimental group, sounds of the ocean or rain were played throughout the night for 3 nights, while patients in the control group experienced usual ambient sounds in their private progressive care rooms.

ANCOVA was used to test the difference in the posttest scores of the two groups with the pretest as the covariate. Significant differences were found for sleep depth scores ($p<$.01), awakening scores ($p<$.01), and total sleep scores ($p<$.01), with the experimental group reporting higher scores, indicating better sleep. There was no difference in the falling asleep scores between the groups. There were no significant differences in the groups in relation to age, gender, time of cardiopulmonary bypass, aortic cross clamp time, or medications received for sleep, pain, or nausea. Using Neuman's model, it is concluded that monotonous sounds are a useful nursing intervention for the patient after coronary artery bypass surgery.