CURRENT Essentials of Critical Care.pdf

20 Current Essentials of Critical Care■■Pulse OximetryEssential Concepts• Finger, ear, or other cutaneous probe measures transmission orreflectance of red and infrared light through tissue• Pulsatile absorbance (“beat-to-beat”) determines percentage ofoxyhemoglobin in blood• Oxyhemoglobin, carboxyhemoglobin, and methemoglobin readas “oxyhemoglobin”• Pulsatile waveform essential for calculation; low perfusion, hypotension,arterial disease, motion artifacts interfere with measurement• Correlates well with arterial blood O 2 saturationEssentials of Management• Use for routine monitoring of patients in ICU and during endoscopy,bronchoscopy, minor surgery, suctioning, sleep apneaepisodes, bronchodilator therapy• Use to adjust supplemental oxygen therapy, including mechanicalventilation• Provides estimate of arterial oxygenation; still need arterialblood gases for PaCO 2 and pH.• Do not use to exclude significant carboxyhemoglobinemia (eg,after smoke inhalation)• May not be accurate during cardiopulmonary resuscitation• Attach to ear lobe or finger according to manufacturer’s instructions• Check for pulsatile waveform on monitor (if provided)• If waveform is poor or pulse oximeter does not provide an adequatereading, try other locations■ PearlVery high methemoglobin levels have the peculiar effect of causingthe pulse oximeter to read 75% regardless of concentration or oxygenation.ReferenceLee WW et al: The accuracy of pulse oximetry in the emergency department.Am J Emerg Med 2000;18:427. [PMID: 10919532]