比較不同呼吸器壓力支持程度對重症病患耗氧量及能量消耗之影響

Comparison of Oxygen Consumption and Energy Expenditure of Different Level of Pressure Support Ventilation in Patients with Critical Illness

10.6269/JRT.201907_18(1).0003

蕭秀鳳(Hsiu-Feng Hsiao)；陳妍慧(Yen-Huey Chen)；許蕙文(Hui-Wen Hsu)；周蘭娣(Lan-Ti Chou)；卓秀英(Hsiu-Ying Cho)；黃崇旂(Chung-Chi Huang)

呼吸功 ； 耗氧量 ； 間接熱量測量 ； 壓力支持通氣 ； work of breathing ； oxygen consumption ； indirect calorimetry ； pressure support ventilation

呼吸治療

18卷1期（2019 / 07 / 01）

27 - 36

繁體中文

研究背景：重症病患呼吸器脫離失敗常見原因有呼吸做功增加、呼吸肌疲勞等。適當的呼吸器支持有助於作功的降低。間接熱量測量儀可正確測量氧氣消耗及身體作功狀態。本研究目的為探討呼吸器不同支持程度對重症病患耗氧量及代謝負荷之影響。研究方法：本研究為前瞻性、交叉次序研究。符合呼吸器脫離條件的重症病患被招募。在原始支持程度（壓力支持模式pressure support ventilation，PSV＝8cmH_2O）完成測量後，病患隨機進入不同次序呼吸器支持（“由高（PSV＝12cmH_2O）轉低支持程度（氣道持續正壓continuous positive airway pressure，CPAP）”或“由低轉高支持程度”），各支持程度皆持續20分鐘，過程中以間接熱量測量儀測量受試者的耗氧量（VO_2）、能量消耗等參數。並記錄受試者的潮氣容積、呼吸速率、呼吸驅力（P0.1）等呼吸相關參數。結果：在PSV模式下，熱量消耗量在PSV 12cmH_2O（1173±287kcal）時顯著低於CPAP（1429±384kcal）及PSV 8cmH_2O（1285±304kcal）（p＜0.05）。PSV 12cmH_2O時的耗氧量（179±42ml／min）顯著低於CPAP（217±59ml／min）及PSV 8cmH_2O（195±46 ml／min）（P＜0.05）。呼吸驅力（P0.1）與耗氧量顯著相關（r＝0.464，p＜0.05），當P0.1增加，耗氧量也上升。結論：重症病患的呼吸器壓力支持的程度會影響耗氧量的變化，呼吸驅力伴隨耗氧量增加，耗氧量的監測或可成為臨床評估呼吸功與呼吸器設定之依據。

Background: Critically ill patients are often failed to wean from mechanical ventilation due to high workload of breathing (WOB) and/or respiratory muscle fatigue. An appropriate ventilator setting may be beneficial in reducing WOB. The aim of this study was to compare the metabolic status among different support levels in critically ill patients who required MV. Methods: This study is a randomized crossover controlled trial. Critically ill patients who were judged eligible for weaning were enrolled. At baseline, the ventilator status was started from pressure support ventilation (PSV) 8 cmH_2O. The patients were then randomly assigned to group 1: support level from high (PSV 12 cmH_2O) to low (CPAP), or group 2: low to high level. Each level remained for 20 min. The oxygen consumption (VO_2), carbon dioxide production(VCO_2) and energy expenditure (EE) were measured by an indirect calorimetry. The tidal volume, respiratory rate, and P0.1 during each level were also recorded. Results: Under the PSV mode, the EE in PS 12 cmH_2O (1173±287 kcal) was significantly lower than those in CPAP (1429±384 kcal) and PS 8 cmH_2O (1285±304kcal)( p ＜ 0.05 ). The VO2 (179±42 ml/min) in PSV 12 cmH_2O was significantly lower than those in PS 8 cmH_2O (195 ± 9 ml/min) and CPAP (218 ± 11 ml/min) (p ＜ 0.05). There was a significant relationship between P0.1 and VO_2 (r =0.464, p ＜0.05). A higher P0.1 was associated with a higher oxygen consumption in patients with mechanical ventilation. Conclusion: The increased P0.1 was associated with higher oxygen consumption in patients with critical illness. The oxygen consumption varied with different ventilator support level. The monitoring of VO_2 may be used as an indicator of workload of breathing and the setting of the ventilator.