Fluid Shift on Obstructive and Central Sleep Apnea
Condition: Apnea (Central and Obstructive)
MeSH terms: Apnea
Study type: Observational

Summary: 
      Fluid retention in the legs due to chronic heart failure (CHF) during the daytime may
      redistribute to neck when with supine positioning at night. A portion of the shifted fluid
      accumulates in the neck, and narrows the upper airway, predisposing the patient to
      obstructive sleep apnea (OSA) and central sleep apnea (CSA). However, the mechanism of
      overnight fluid shift on OSA and CSA remains unclear. The investigators pre-experiment
      demonstrated there may be a different mechanism of overnight fluid shift on OSA and CSA. The
      accumulation of water content in neck soft tissue increases neck circumference and leads to
      pharyngeal resistance, upper airway collapse and causes OSA. The effect of nocturnal fluid
      shift on CSA may be because of increasing of chemosensitivity (fluctuation of PaCO2),
      circulation delay and hemodynamic disordered. This study is aimed to explore the different
      mechanism of overnight fluid shift on OSA and CSA by comparing the changes of upper airway
      (inside diameter, water content, and pharyngeal resistance), PaCO2, circulation delay
      (lung-to-finger circulation time) and hemodynamic (loop gain).
    

Detailed description: 
      Methods:

      Between June 2015 and December 2017, 180 patients with chronic heart failure caused by
      rheumatic heart disease, cardiomyopathy and coronary heart disease (in Cardiology Department
      and Cardiothoracic Surgery Department of the First Affiliated Hospital of Nanjing Medical
      University), were screened for sleep apnea by polysomnography (PSG). Of them, 20 obstructive
      sleep apnea (OSA) and 20 central sleep apnea (CSA) were enrolled. Clinical evaluations
      including NYHA class, electrocardiographic, echocardiographic, arterial blood gas analysis
      findings, baseline medication, and 6-minute walk test (6MWT) were recorded.

      The fluid index, head and neck CT and pharyngeal resistance were tested at 20:00. Then a full
      night PSG and percutaneous PaCO2 were performed. The fluid index, head and neck CT and
      pharyngeal resistance were repeated at 6:00 after PSG.

      The volume of fluid shift from legs to head and neck,inside diameter of the upper airway, and
      water content of neck soft tissue were calculated. The lung-to-finger circulation time and
      loop gain were measured.

        1. Mechanism of overnight fluid shift on OSA:

           Fluid shift volume from legs to head and neck,inside diameter of upper airway, water
           content of neck soft tissue, percutaneous PaCO2, severity of sleep apnea, minimum SP02,
           lung-to-finger calculation time and loop gain were measured at 22:00 and repeated at
           6:00 next morning in patients with OSA.Correlations between changes of fluid shift
           volume and changes in diameter of upper airway, water content of neck soft tissue,
           PaCO2, minimum SP02, lung-to-finger calculation time and loop gain were analyzed.

        2. Mechanism of overnight fluid shift on CSA:

      Fluid shift volume from legs to head and neck,inside diameter of upper airway, water content
      of neck soft tissue, percutaneous PaCO2, severity of sleep apnea, minimum SP02,
      lung-to-finger calculation time and loop gain were measured at 22:00 and repeated at 6:00
      next morning in patients with CSA.Correlations between changes of fluid shift volume and
      changes in diameter of upper airway, water content of neck soft tissue, PaCO2, minimum SP02,
      lung-to-finger calculation time and loop gain were analyzed.
    

Intervention name(s): no interventions
Intervention type(s): Other
Intervention description(s): This is an observational study and no intervention applied.
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        patients with chronic heart failure caused by rheumatic heart disease, cardiomyopathy and
        coronary heart disease.
      
Keywords: central sleep apnea; Cheyne-Stokes respiration; obstructive sleep apnea; chronic heart failure; fluid shift