• Mau Kenneth E Stone, Terry D Bauch, and Bernard J Rubal.
• Department of Cardiology, Brooke Army Medical Center, Fort Sam Houston, Texas 78234-6200, USA. kenneth.stone2@cen.amedd.army.mil
• Clin Cardiol. 2006 Sep 1;29(9):411-4.

BackgroundTimely identification of hemodynamic compromise in patients with acute pericardial effusion and tamponade is critical in patient management. Respiratory variability in pulse-oximetry waveforms has been correlated with pulsus paradoxus, but has not been reported with cardiac tamponade in adult patients.HypothesisThis study describes changes in respiratory variability in pulse-oximetry waveform pre and post pericardiocentesis in patients with hemodynamically significant pericardial effusions.MethodsA single-center, catheterization laboratory hemodynamic database was reviewed for all patients who underwent pericardiocentesis for clinically suspected tamponade and had continuous digital pulse-oximetry, electrocardiographic, and respiration waveforms recorded during the procedure. Phasic respiratory changes in pulse-oximetry waveform amplitude (maxima-minima) were expressed as an expiratory/inspiratory ratio and compared pre and post pericardiocentesis.ResultsThe study population consisted of 12 patients (6 men:6 women, age 60 +/- 10 years) with pericardial effusion documented by echocardiography on the day of pericardiocentesis. Phasic respiratory variability in the pulse-oximetry waveform was evident in all patients prior to aspiration (respiratory ratio = 1.9 +/- 0.5). Following pericardiocentesis (aspirated volume: 650 +/- 300 ml), the respiratory ratio decreased in all patients (1.2 +/- 0. 1, p = 0.001). Receiver operator characteristic curve analysis suggests that pulse-oximetry respiratory ratios > or = 1.5 should raise suspicion of hemodynamic compromise in high-risk populations.ConclusionsPulse-oximetry is a commonly used tool for monitoring critically ill patients. The present study suggests that increased respiratory variability in the pulse-oximetry waveform should raise suspicion for hemodynamic compromise in patients at risk for pericardial effusion.

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