Increased augmentation index (AIx) is accompanied by an elevated cardiovascular risk. A reduction of AIx is known for long-term continuous positive airway pressure (CPAP) therapy. We hypothesised that acute preload and left ventricular workload effects AIx and subendocardial viability ratio (SEVR) as a marker of coronary flow reserve.

Increased augmentation index and central blood pressure parameters were measured by radial artery tonometry in 17 healthy men (32/±6years) at rest and during CPAP ventilation at pressures of 5, 10mbar and after recovery. In a subset of seven individuals, haemodynamic parameters and autonomic function were additionally examined using combined impedance cardiography and continuous noninvasive blood pressure monitoring.

Continuous positive airway pressure reduced heart rate corrected (AIx@75) (-2.8±8.1 [rest] to −10.7±11.3 [5mbar], p<0.01, to −12.2±10.5% [10mbar], p<0.01) and systolic time integral as a marker of left ventricular workload (2115±231 [rest] to 1978±290 [5mbar], p=0.02 to 1940±218 [10mbar], p<0.01 to 2013±241mmHg/s per min [recovery], p=0.03), while central systolic pressure did not change during CPAP. Total Peripheral Resistance Index increased reaching level of significance at 10mbar CPAP condition (1701±300 [rest] to 1850±301dyn*s*m²/cm⁵ [10mbar], p=0.04). There was a reversible increase of SEVR under CPAP conditions.

Continuous positive airway pressure ventilation acutely reduces AIx, heart rate and left ventricular workload in healthy young men. These effects seem to be mediated by left ventricular filling pressure, workload and reflection wave. Furthermore, we found an increase of subendocardial viability ratio as an indication for a rising coronary flow reserve by CPAP.