Study objectives: To define the relation between
systolic arterial pressure (SAP) changes during ventilation and left
ventricular (LV) performance in humans.
Prospective repeat-measures series.
University of Pittsburgh Medical Center Operating Room.
Patients: Fifteen anesthetized cardiac surgery patients
before and after cardiopulmonary bypass when the mediastinum was either
closed or open.
Measurements and results: SAP and LV
midaxis cross-sectional areas were measured during apnea and then were
measured for three consecutive breaths. SAP increased during
inspiration, this being the greatest during closed chest conditions
(p < 0.05). Changes in SAP could not be correlated with changes in
either LV end-diastolic areas (EDAs), end-systolic areas, or stroke
areas (SAs). If SAP decreased relative to apnea, the decrease occurred
during expiration and was often associated with increasing LV EDAs and
SAs. SAP often decreased after a positive-pressure breath, but the
decrease was unrelated to SA deficits during the breath. Increases in
SAP were in phase with increases in airway pressure, whereas decreases
in SAP, if present, followed inspiration. No consistent relation
between SAP variation and LV area could be identified.
Conclusions: In this patient group, changes in SAP reflect
changes in airway pressure and (by inference) intrathoracic pressure
(as in a Valsalva maneuver) better than they reflect concomitant
changes in LV hemodynamics.