Respiratory origin of fluctuations in arterial blood pressure in premature infants with respiratory distress syndrome.

A variable fluctuating pattern of arterial BP often precedes intraventricular hemorrhage in mechanically ventilated preterm infants. To learn more about the origin of this pattern, arterial BP and respiratory muscle activity were studied in five intubated premature infants who were at high risk for intraventricular hemorrhage. We monitored esophageal pressure, gastric pressure, and arterial BP. Consistent findings were: (1) arterial BP fluctuations have the same frequency and direction of change as esophageal and gastric pressure changes associated with spontaneous breathing (R ranged from .93 to .98, P less than .001); (2) spontaneous apneic pauses were accompanied by sudden and complete cessation of arterial BP fluctuations; (3) large "cough-like" fluctuations in esophageal and gastric pressures, seen in all infants, were associated with the largest fluctuations in arterial BP; (4) cutaneous stimulation had negligible effect on fluctuation in arterial BP provided no change in esophageal and gastric pressures occurred; (5) the effects of change in esophageal and gastric pressures on arterial BP were nearly simultaneous (0.05 to 0.25 second latency); (6) respirator pressure fluctuations had negligible effects on the fluctuations in arterial BP. These data suggest that the fluctuations in arterial BP are directly related to respiratory muscle activity and are most consistent with the familiar pulsus paradoxus that occurs in various other cardiorespiratory diseases.