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P256 Treatment of obstructive sleep apnoea syndrome with continuous positive airways pressure alters haemostasis: further data on the use of fractal analysis to measure microstructure of incipient clot
  1. M Wilczynska1,
  2. KE Lewis1,
  3. S Stanford2,
  4. M Lawrence2,
  5. K Hawkins3,
  6. PR Williams3,
  7. PA Evans2
  1. 1Prince Philip Hospital, Llanelli, United Kingdom
  2. 2NISCHR Haemostasis Biomedical Research Unit, Swansea, United Kingdom
  3. 3College of Engineering, Swansea University, Swansea, United Kingdom


Introduction Untreated obstructive sleep apnoea syndrome (OSAS) increases cardiovascular risk and altered haemostasis is at least partly implicated. As previously reported using fractal analysis and a new biomarker called fractal dimension (Df) it is possible to assess the microstructure of incipient clot in whole blood (1). Df relates to the kinetics of clot formation and quantifies clot fibrin network microstructure as it forms. A higher Df represents a more pro-coagulable state. Healthy volunteers have a reproducible Df of 1.74(0.07) (2).

Aim To see if Df changes in OSAS after an acute and subacute treatment with CPAP.

Methods 36 patients with newly diagnosed OSAS: 32 males, mean (SD), BMI = 37.1 (7.5) kg/m2, age 56.6 (10.2) years, 4% desaturation rate (4% DR) = 44.6 (31.1) events/hour, Epworth Sleepiness Score (ESS) 13.23 (5.0). Blood was collected at baseline prior to CPAP treatment and then after the first night and 4 weeks of CPAP. Samples were tested for fractal analysis (AR-G2 Rheometer, TA Instruments, UK).

Results Patients who were commenced on CPAP were followed up within an average of 36.97(6.29) days. CPAP compliance was overall satisfactory with a mask on average time of 4.43 (1.8) hrs/night. Repeated overnight pulse oximetry while on CPAP showed a significant improvement in sleep study variables (4% DR = 7.58 (8.3) events/hr; p < 0.001) when compared to pre-CPAP measurements. CPAP use resulted in the significant reduction in Df (ANOVA p < 0.001) (Figure 1). Post-hoc analysis (Tukey HSD) showed that an acute (1 night, p < 0.001) and a short period (1 month, p = 0.01) CPAP treatment both resulted in the significant change in Df levels when compared to the baseline.

Abstract P256 Figure 1.

Individual Df measurements at the baseline and after a night of CPAP treatment and a month of CPAP treatment in OSAS group.

Conclusion As reported previously OSAS is associated with a significantly increased prothrombotic state in the morning that is detected by Df. Acute CPAP use in OSAS is sufficient to alter fibrin clot microstructure which can be quantified with Df. This preliminary data suggest Df could be used as a new sensitive biomarker to assess vascular risk.


  1. Wilczynska M et al Thorax. 2012;67:A23-A23

  2. Evans PA et al Blood. 2010;116:3341–3346

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