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Corresponding author: Linda L. Chlan, RN, PHD, University of Minnesota School of Nursing, 5-160 Weaver-Densford Hall, 308 Harvard St SE, Minneapolis, MN 55455 (e-mail: chlan001{at}umn.edu).
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Abstract |
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• Objective To explore the influence of music on serum biomarkers of the stress response in patients receiving ventilatory support.
• Methods A convenience sample of 10 patients receiving mechanical ventilation was recruited from an 11-bed medical intensive care unit. Patients were randomly assigned to listen to music or to rest quietly for 60 minutes. Levels of corticotropin, cortisol, epinephrine, and norepinephrine were measured 4 times during the 60 minutes.
• Results The levels of the 4 biomarkers of the stress response did not differ significantly between patients who listened to music and patients who rested quietly, though the levels of corticotropin and cortisol showed interesting trends.
• Conclusions Additional research is needed with a larger sample size to evaluate further the influence of music on biochemical markers of the stress response in patients receiving mechanical ventilatory support. In future studies, confounding factors such as endotracheal suctioning and administration of medications that influence the stress response should be controlled for.
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Methods |
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Ten patients (6 women, 4 men; 9 white, 1 black) with a mean age of 64.9 years (range 53–79 years, SD 7.8 years) who had been receiving ventilatory support for an average of 14.2 days (range 1.5–44 days, median 7.5 days, mode 3 days, SD 15.0 days) participated. Medical diagnoses included pneumonia (n = 5), respiratory failure (n = 2), shortness of breath (n = 1), ventricular tachycardia (n = 1), and ischemic bowel (n = 1). Modes of ventilatory support included assist-control(n =6), synchronized intermittent mandatory ventilation (n=2), and pressure-release ventilation (n=2).
Subjects provided their own informed consent and were randomly assigned to either 60 minutes of listening to music through headphones (n = 5) or to resting quietly for 60 minutes (n = 5). Subjects in the music group selected a preferred tape from a collection containing a variety of genres (classical, new age, easy listening, country). All subjects selected classical music.
Data Collection Procedure
Beginning at 5:40 AM, blood samples were obtained from the central venous catheter at 4 intervals: baseline, 15 minutes after baseline, 30 minutes after baseline, and 60 minutes after baseline. Specimens were transferred to their respective collection tubes and immediately placed on ice. Biomarkers of both components of the stress response were measured: corticotropin and cortisol for activity of the HPA axis, and epinephrine and norepinephrine for SNS activity. Heart rate, an indirect indicator of SNS activity, was recorded from the bedside monitor at the same times the blood samples were obtained.
Corticotropin and Cortisol Assays. Approximately 5 mL of blood was placed in a siliconized, lavender glass tube. Plasma level of corticotropin was assayed with direct radioimmunoassay as described previously6; plasma level of cortisol was measured with a radioimmunoassay kit (ICN Biochemical, Costa Mesa, Calif).
Epinephrine and Norepinephrine Assays. Approximately 7 mL of blood was placed in a heparinized glass collection tube. Epinephrine and norepinephrine were assayed by using high-performance liquid chromatography with electrochemical detection; the assay was performed by a diagnostic laboratory (ARUP Laboratories, Salt Lake City, Utah).
Data Analysis
The biomarkers were not normally distributed; at baseline, all levels were equivalent between groups (see Table
), except for cortisol (U = 2.0, P = .03). A Kruskal-Wallis test was used to detect any differences between groups in heart rate and levels of corticotropin, epinephrine, and norepinephrine. A Friedman test was used to detect any differences in cortisol level.
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| Music therapy reduces blood pressure and heart and respiratory rate.
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Results |
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Description of Serum Levels of Stress Hormones
Mean heart rate and levels of corticotropin, cortisol, epinephrine, and norepinephrine are presented in the Table
. Heart rate means were within the normal range for both groups. All subjects had corticotropin levels of less than 18 pmol/L (80 pg/mL), the normal range in the morning. The normal range for cortisol is 140 to 630 nmol/L (5–23 µg/dL).7 At baseline, mean cortisol level was elevated for the subjects in the music group and was within the normal range for the subjects in the rest group.
The normal ranges for epinephrine and norepinephrine are 50 to 1090 pmol/L (10–200 pg/mL) and 473 to 3073 nmol/L (80–520 pg/mL), respectively (ARUP Laboratories). Levels of both epinephrine and norepinephrine were within the normal range at baseline for all subjects and were similar to the levels measured in other studies.8
Results of Statistical Analyses of Serum Biomarkers
No statistically significant differences were detected between groups for heart rate or for any of the serum levels of biomarkers of the stress response (see Table). The following data trends were detected. The biomarkers of SNS activity showed variable changes between groups during the study period. Mean levels of epinephrine and norepinephrine in the subjects who listened to music decreased from baseline to 15 minutes after baseline, increased slightly at 30 minutes after baseline, and then decreased (norepinephrine) or remained stable (epinephrine) at 60 minutes after baseline. This variable pattern of SNS activity could have been influenced by the fact that 2 subjects in the music group needed endotracheal tube suctioning before the blood sample was obtained 30 minutes after baseline.9 In the subjects who rested quietly without music, levels of epinephrine and norepinephrine both decreased at 15 minutes after baseline, increased slightly (norepinephrine) or decreased (epinephrine) at 30 minutes after baseline, and then both increased at 60 minutes after baseline.
Heart rate decreased slightly for the music group until 60 minutes after baseline, when it began increasing. For the rest group, heart rate decreased during the study period. Three of the 5 subjects in the rest group received intravenous morphine sulfate immediately before or during implementation of the protocol, which could have artificially reduced heart rate and levels of epinephrine and norepinephrine.8,10 Subjects who listened to music did not receive such medications before or during the protocol. Biomarkers of activity of the HPA axis also showed variable changes between groups during the study period.
| No difference was found in stress response markers between subjects receiving music therapy and those not receiving it.
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Discussion |
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Although subjects in the music group and subjects in the rest group experienced divergent types of care interventions during the research protocol (endotracheal tube suctioning, which increases the stress response, and receipt of sedatives, which diminishes the stress response), no clear pattern of SNS activity was apparent from the levels of biomarkers. Further study is needed to determine whether music can directly influence serum levels of SNS biomarkers by demonstrating effects similar to those of sedative medications.
Findings of music’s influence on biomarkers of activity in the HPA axis also were not clearly articulated in the study data. As with the SNS biomarkers, further study is needed to see whether music directly influences the activity of the HPA axis.
Study Limitations
Although the goal was to recruit as homogeneous a sample as possible, the duration of ventilatory support varied widely. Although the difference was not statistically significant, subjects in the music group had been receiving ventilatory support for almost 3 days longer than had the subjects in the rest group. Subjects who had been receiving ventilatory support for longer could have acclimated to this stressful experience. However, patients who receive ventilatory support for more than 20 days experience some of the highest anxiety levels.11 Attenuation of the stress response in patients receiving prolonged ventilatory support and how such attenuation might be influenced by music require further study.
Other limitations of this study include the small sample size and the wide variability in sample means. Problems with central venous catheters resulted in the inability to extract blood from 2 subjects in the rest group. The influence of these missing data on study findings is not known.
Because of the risks associated with blood loss and the limitations placed on the protocol by the institutional review board, only 4 serum samples were obtained from participants. Additional serum samples during the study period might have provided a more complete representation of biomarker activity. Variations in serum levels of biomarkers between 30 and 60 minutes after baseline were not assessed.
Last, the investigators were unable to prevent nurses from administering medications that would affect the SNS to subjects in the rest group. These medications may have influenced the findings.
Directions for Further Research
This pilot study provides preliminary data on which to build future investigations that test the influence of music on the stress response. Further study with a larger sample is warranted to evaluate whether music can interrupt the stress response in patients receiving mechanical ventilation and to obtain a clearer picture of the activity of biomarkers of the stress response while controlling for confounding factors. Power analysis calculations (power = .80, P < .05) indicate that 57 patients per group would be needed to detect a statistically significant difference in all biomarkers of the stress response. A multisite study would be necessary to recruit the required number of subjects. However, obtaining serial blood samples at exactly the same time from all participants would be a challenge. Investigators could consider measuring more readily obtainable biomarkers of the stress response from samples of urine or saliva. Researchers also are advised to plan for longer recruitment periods and use of additional resources to obtain a homogeneous sample in the ICU.
Implications of Findings for Nursing Practice
Although the results from this study indicate that further research is needed, they also suggest that the potential exists for music intervention to favorably influence the stress response in patients receiving ventilatory support. Music is a safe intervention that is not detrimental to patients. It provides a welcome opportunity for patients to focus on a pleasant, comforting stimulus rather than on stressful thoughts or environmental stimuli. In addition, headphones can attenuate some of the distracting noises that often cause a stress response in the ICU.12,13 Nurses can implement music intervention with selections that are preferred by the patients to induce relaxation for short-term benefit; wearing headphones for as little as 30 minutes can be beneficial.2–4,12 Music used for relaxation should have a tempo of 60 to 80 beats per minute, predictable dynamics, fluid melodic movement, pleasing harmonies, regular rhythm, and tonal qualities including strings, flute, piano, or specially synthesized tones.14 Longer periods of uninterrupted music listening are encouraged if the patient desires.
Further research that tests patients’ responses to music by measuring salient biomarkers of the stress response will increase knowledge about nonpharmacological interventions for managing stress and promoting relaxation in patients receiving ventilatory support. Future studies should assess the clinical benefit of not only music but other nonpharmacological interventions to promote relaxation in patients receiving mechanical ventilatory support.
To purchase reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, reprints{at}aacn.org.
This study was supported in part by a grant-in-aid from the University of Minnesota Graduate School awarded to Dr Linda Chlan and in part by National Science Foundation grant IBN-0112543 awarded to Dr William Engeland.
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