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The Impact of Mechanical Ventilation on Pulse Oximetry in Thoracic Cavity

摘要:目的: 評價機械通氣對胸腔內脈搏氧飽和度的影響。 方法 :以食道、氣管和降主動脈作為胸腔內脈搏氧飽和度的監測位點,將改制后的氧飽和度探頭分別固定于上述部位,并連接于同一監護儀上。純氧通氣,待上述氧飽和度容積波波形和讀數穩定,停止機械通氣30s。以錄像的方式記錄機械通氣停止前后30 s內食道、氣管和降主動脈SpO2容積波和讀數的變化。同時記錄舌SpO2。 結果 :機械通氣時,食道、氣管和降主動脈三個監測位點均可獲得異常高大的SpO2容積波;停止通氣時,異常高大的氧飽和度波形消失。食道、氣管和降主動脈脈搏容積波變異率分別為112%,74%,302%。降主動脈脈搏容積波的變異率明顯高于食道和氣管( 〖WTBX〗P ＜005)。機械通氣停止前后30s內食道、氣管和降主動脈的SpO2讀數變化無顯著差異(〖WTBX〗P ＞005)。 結論 :機械通氣對胸腔內食道、氣管和降主動脈氧飽和度讀數無影響,主要影響是脈搏容積波。且各位點間脈搏氧容積波受呼吸的影響不同。Abstract: Objective: To investigate the impact of mechanical ventilation on pulse oximetry in thoracic cavity. Methods : After dogs anesthesia induction and thoracotomy, pulse oximeters were simultaneously placed at esophagus, trachea, and descending aorta, and connected with the same monitor for SpO2 monitoring. During ventilation with 100% oxygen, the mechanical ventilator was temporarily switched off for 30 seconds after high quality PPG waveforms and SpO2 readings were obtained. SpO2 signals and readings from esophagus (SeO2), trachea (StraO2), descending aorta (SDAO2) shown on the monitoring screen were recorded by the SONY video before and after stopventilation. And StonO2 were also recorded. Results : Abnormally largeamplitude PPG waves were found in normal waves at monitoring sites of esophagus, trachea, and descending aorta in all animals during ventilation; however, they disappeared without ventilator. The variation rate in ventilationinduced PPG amplitude were 112%, 74%, 302% at esophagus, trachea and descending aorta respectively. The PPG amplitude variation rate from SDAO2 was higher than that from SeO2 and StraO2 (〖WTBX〗P ＜005). However, the SpO2 readings obtained from pulse oximetries in all sites were no significantly statistical difference within 30s before and after temporarily stopventilation (〖WTBX〗P ＞005). Conclusion : Abnormally amplitude PPG waveforms from oximetry probe placed at esophagus, trachea, and descending aorta were induced by ventilation. The Variation rate in ventilationinduced PPG amplitude was various at different monitoring sites. The SpO2 readings from esophagus, trachea, and descending aorta were not significantly contaminated by ventilation.