A characterization of motion affecting pulse oximetry in 350 patients.

As part of an oximetry research effort in which plethysmographic data were collected from moving patients, a wide variety of patient motion affecting pulse oximetry was observed and characterized by the clinical incidence, type, severity and duration of patient motion. 350 patients were observed for movement in clinical settings, including ICU, SICU, MICU, PICU, NICU, OR and PACU, at 4 hospitals and on an ambulance. 20% (70) of the patients exhibited motion. Half (35) of the moving patients were instrumented to record oximetric, plethysmographic and/or acceleration information. 31% of NICU infants moved compared to only 7% of adults in ICUs. The most common noisy oximetry signals were caused by motion characterized by extending/flexing (/kicking in infants) and by clenching/pressing/rubbing. In infants, these motion types accounted for 53% and 11% of motion, respectively. Less common infant motion types were patient cares, shifting body position and cough/cry. The most common adult motions were equally divided among extend/flex, clench/press/rub, twitch/shake and transport motion types. Extend/flex motions typically demonstrated high plethysmographic waveform modulation (71.5% maximum) and high acceleration. Clench/press/rub motions typically also had high modulations, but low G-force. With one high-G exception, twitch/shake motions had little or no effect on oximetry readings. Less common adult motion types affecting pulse oximetry included cough/cry, strain/posture, tremors and tap/bump. Most recorded motions were aperiodic and short-lived, 62% lasting less than 10 seconds, only 5% lasting over 1 minute. NICU patients made the longest lasting continuous series of motions, while adults made 86% of the motions lasting a second or less.