EFFECTS OF TRANSIENT INTRATHORACIC PRESSURE CHANGES (HICCUPS) ON SYSTEMIC ARTERIAL-PRESSURE

The purpose of the study was to determine the effect of transient chan ges in intrathoracic pressure on systemic arterial pressure by utilizi ng hiccups as a tool. Values of systolic and diastolic pressures befor e, during, and after hiccups were determined in 10 intubated preterm i nfants. Early-systolic hiccups decreased systolic blood pressure signi ficantly (P < 0.05) compared with control (39.38 +/- 2.72 vs. 46.46 +/ - 3.41 mmHg) and posthiccups values, whereas no significant change in systolic blood pressure occurred during late-systolic hiccups. Diastol ic pressure immediately after the hiccups remained unchanged during bo th early-and late-systolic hiccups. In contrast, diastolic pressure de creased significantly (P < 0.05) when hiccups occurred during diastole (both early and late). Systolic pressures of the succeeding cardiac c ycle remained unchanged after early-diastolic hiccups, whereas they de creased after late-diastolic hiccups. These results indicate that tran sient decreases in intrathoracic pressure reduce systemic arterial pre ssure primarily through an increase in the volume of the thoracic aort a. A reduction in stroke volume appears to contribute to the reduction in systolic pressure.