title: Respiratory changes in the pulse-oximetry waveform associated with pericardial tamponade.
abstract: BACKGROUND
  Timely 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.
  
  
  OBJECTIVE
  This study describes changes in respiratory variability in pulse-oximetry waveform pre and post pericardiocentesis in patients with hemodynamically significant pericardial effusions.
  
  
  METHODS
  A 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  Pulse-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.
authors.affiliation: Department of Cardiology, Brooke Army Medical Center, Fort Sam Houston, Texas 78234-6200, USA. kenneth.stone2@cen.amedd.army.mil
authors.forename: Mau Kenneth E
authors.initials: MK
authors.lastname: Stone
authors.forename: Terry D
authors.initials: TD
authors.lastname: Bauch
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Rubal
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D001794:Blood Pressure; D002305:Cardiac Tamponade / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010490:Pericardial Effusion / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D020519:Pericardiocentesis; D012119:Respiration; D012680:Sensitivity and Specificity