CPAP reduces augmentation index, left ventricular workload in healthy males
In healthy young males, continuous positive airway pressure (CPAP) acutely reduces augmentation index (AIx), left ventricular workload and heart rate, a recent study has shown.
Radial artery tonometry was used to measure increased resting and CPAP AIx and central blood pressure parameters in 17 healthy males (mean age 32±16 years). AIx was significantly reduced from baseline (103±10 percent) after CPAP at 5 mbar (97±11 percent (p<0.01) and 10 mbar (95±11 percent; p<0.01). Values significantly increased to 100±10 percent during the recovery phase (p<0.01).
Heart rate likewise showed a significant decline after CPAP at 5 and 10 mbar (64±8 bpm at baseline vs 61±10 and 61±8 bpm, respectively; p=0.02 and p<0.01). The increase during the recovery phase was not significant (63±8 bpm; p=0.37).
CPAP also significantly affected pressure-time integral and performance. For instance, using systolic time integral (2,115±231 mm Hg/s per minute at baseline) as a marker, the researchers observed declines in left ventricular workload after 5 mbar (1,978±290 mm Hg/s per minute; p=0.02) and 10 mbar (1,940±218 mm Hg/s per minute; p<0.001) of CPAP.
Ejection duration was also significantly decreased from baseline after 5 and 10 mbar of CPAP (35±3 vs 33±3 and 32±3, respectively; p=0.02 and p<0.01). No significant recovery effect was observed.
In contrast, the subendocardial viability ratio, as represented by the Buckberg Index, increased following CPAP. From 164±28 percent at baseline, the Index scores rose to 182±32 and 186±23 percent (p<0.001 for both) after 5 and 10 mbar of CPAP, respectively.