Fig. 2. Figure represents the heart pressure and volume events that ensue after the institution of 15 cm H2O CPAP. The onset of CPAP is marked A . The beginning and end of the heart cycle sequence where left ventricular pressure-volume relationship (LVPVR) is analyzed for systolic function parameters are marked B and C , and these cycles have end-diastolic and end-systolic points marked for the period between B and C on the corresponding pressure-volume curves. The CVP curve illustrates the timing of CPAP start in relation to the start of left ventricular pressure and volume reduction (see Results text). Note the relatively small change in end-systolic pressure between B and C , whereas end-systolic volume increases, occurring after an increase in systolic pressures during the period where lung inflation has occurred but before progressive end-systolic and end-diastolic pressure and volume decreases have begun (B ).