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Nonlinear Processes of Fluid Redistribution in the Head and Neck Region Caused by Body Posture Changes in Severe Obstructive Sleep Apnea Patients
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A2423 - Nonlinear Processes of Fluid Redistribution in the Head and Neck Region Caused by Body Posture Changes in Severe Obstructive Sleep Apnea Patients
Author Block: Y. Huang, H. Zhang, C. Wang, H. Lin, S. Wang, H. Xu; School of Biomedical Engineering, Capital Medical University, Beijing, China.
RATIONALE: When the body posture changes from standing or sitting to supine position, the fluid in the lower body will shift into the head and neck region, resulting in upper airway narrowing. Investigating the process of fluid redistribution in the soft tissues of the head and neck resulting from body posture changes is very important in understanding the role played by fluid shift in airway obstruction in obstructive sleep apnea (OSA) patients. The aim of this study is to test our hypothesis that the amount of fluid shifted into the head and neck changes nonlinearly with time in OSA patients. METHODS: Overnight polysomnography is performed in 9 patients with apnea-hypopnea index AHI > 30 to monitor sleep stages and AHI. The leg fluid volume at standing, right after lying down, lying supine for 15 min, and before rising in the morning are measured to analyze process of fluid shift with time. Neck, calf and ankle circumferences at standing, lying supine for 5 min, and before rising in the morning are also measured. RESULTS: AHI of the patients is 48.9 ± 14.3. The results show that almost 20 percent of the total amount of displaced fluid shifts immediately after the body posture changes from standing to supine position. This value increases to one third of the total fluid displacement after 15 min of lying supine. Polysomnography data show that the time elapsed between lying down and sleep onset in these OSA patients is 30.1 ± 18.3 min. We can predict from data fitting that the amount of fluid shift after 30 min of lying supine will increase to 50% of the total amount of displaced fluid from standing before going to bed in the evening to lying supine before rising in the morning. The changes in the neck, calf and ankle circumferences are all nonlinear with time. CONCLUSION: The amount of fluid shifted into the head and neck changes very nonlinearly with time in OSA patients. Compared to the total amount of fluid shift during the whole night, the major process of fluid shift has largely finished before sleep onset in these severe OSA patients.
Author Block: Y. Huang, H. Zhang, C. Wang, H. Lin, S. Wang, H. Xu; School of Biomedical Engineering, Capital Medical University, Beijing, China.
RATIONALE: When the body posture changes from standing or sitting to supine position, the fluid in the lower body will shift into the head and neck region, resulting in upper airway narrowing. Investigating the process of fluid redistribution in the soft tissues of the head and neck resulting from body posture changes is very important in understanding the role played by fluid shift in airway obstruction in obstructive sleep apnea (OSA) patients. The aim of this study is to test our hypothesis that the amount of fluid shifted into the head and neck changes nonlinearly with time in OSA patients. METHODS: Overnight polysomnography is performed in 9 patients with apnea-hypopnea index AHI > 30 to monitor sleep stages and AHI. The leg fluid volume at standing, right after lying down, lying supine for 15 min, and before rising in the morning are measured to analyze process of fluid shift with time. Neck, calf and ankle circumferences at standing, lying supine for 5 min, and before rising in the morning are also measured. RESULTS: AHI of the patients is 48.9 ± 14.3. The results show that almost 20 percent of the total amount of displaced fluid shifts immediately after the body posture changes from standing to supine position. This value increases to one third of the total fluid displacement after 15 min of lying supine. Polysomnography data show that the time elapsed between lying down and sleep onset in these OSA patients is 30.1 ± 18.3 min. We can predict from data fitting that the amount of fluid shift after 30 min of lying supine will increase to 50% of the total amount of displaced fluid from standing before going to bed in the evening to lying supine before rising in the morning. The changes in the neck, calf and ankle circumferences are all nonlinear with time. CONCLUSION: The amount of fluid shifted into the head and neck changes very nonlinearly with time in OSA patients. Compared to the total amount of fluid shift during the whole night, the major process of fluid shift has largely finished before sleep onset in these severe OSA patients.
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