容積目標式呼吸器在早產兒的使用

研究目的：近30年來壓力限定，時間週期性呼吸器［time-cycled, pressure-limited ventilation,（PLV）］被廣泛的使用在新生兒和早產兒身上。PLV 呼吸器使用時往往需要設定最高吸氣壓力（peak inspiratory pressure）及吸氣時間（inspiratory time），但此類呼吸器使用在早產兒容易造成肺部過度擴張（overexpansion）而造成肺容積傷害（volutrauma）或導致肺部擴張不全（underexpansion）或肺塌陷（collapse）。近年來許多研究發現容積目標式呼吸器［volume-targeted ventilation（VTV）］在早產兒使用上可調控及維持適當的潮氣容積［tidal volume（VT）］，這可以減少早產兒使用呼吸器時受到的肺損傷（lung injury）而導致之慢性肺疾病：肺支氣管形成不全［bronchopulmonary dysplasia,（BPD）］。為了探討VTV在早產兒使用的可能性（feasibility）及效率（efficiency），我們做了以下兩項研究。研究方法及研究結果：研究一：Volume-targeted versus pressure-limited ventilation for preterm infants （容積目標式與壓力限定式呼吸器在早產兒使用上的比較）。 2014年10月01日至2016年02月28日（period 1）共有50位早產兒使用PLV式呼吸器；2016年03月01日至2017年08月01日（period 2）也另有50位早產兒使用VTV式呼吸器。結果顯示使用VTV組比PLV組的早產兒有較少發生血中二氧化碳過高（hypercarbia）及死亡或BPD（combined outcome of death or BPD） 發生率較低。研究二：Effect of high-frequency oscillatory ventilation combined with volume guarantee on preterm infants with hypoxic respiratory failure（高頻震盪呼吸器合併容積保證在早產兒合併缺氧性呼吸衰竭的應用）。Volume guarantee（VG）為一種VTV，這種呼吸器電腦可以計算出呼出的潮氣容積（exhaled VT）而計算出最適當的目標潮氣容積（targeted VT）為何。共有52位早產兒使用傳統性呼吸器﹝conventional mechanical ventilation,﹙CMV﹚﹞後仍患有缺氧性呼吸衰竭﹝hypoxic respiratory failure,﹙HFR﹚﹞而必須使用高頻震盪呼吸器﹝high-frequency oscillatory ventilation﹙HFOV﹚﹞納入此研究中。2012年06月至2016年02月（period 1）共有34位早產兒使用HFOV（SLE 5000, SLE UK, United Kingdom），2016年03月至2017年12月（period 2）共有18位早產兒使用HFOV 合併VG（HFOV + VG）。結果顯示罹患缺氧性呼吸衰竭的早產兒使用HFOV合併VG比單獨使用HFOV（HFOV alone）較能減少血中二氧化碳濃度過高（hypercarbia），也較能減少死亡或BPD（combined outcome of death or BPD）的發生率。結論： 容積目標式呼吸器（VTV）可以用來治療早產兒合併呼吸窘迫（respiratory distress）或呼吸衰竭（respiratory failure）。容積目標式呼吸器要比傳統呼吸器更能減少早產兒的肺部受到傷害（lung injury）。

Introduction：Time-cycled pressure-limited ventilation (PVL) has been traditionally used for newborn infants. This form of ventilation uses a designated volume of gas with a peak inspiratory pressure (PIP), over a defined time cycle. Both overexpansion (volutrauma) and under expansion / collapse (atelectrauma) have been previously reported during the use of PVL. Volume-targeted ventilation (VTV) can regulate and maintain an appropriate tidal volume (VT). We have designed two studies to compare the effects of VTV with PVL in preterm infants.Method and Results：Study 1: To compare the effects of volume-targeted (VTV) versus pressure-limited ventilation (PLV) in preterm infants. We collected 100 preterm infants required mechanical ventilation during two time periods were studied. PLV was used in 50 preterm infants in period 1. VTV was used in 50 preterm infants in period 2. Clinical outcomes including mortality rate, duration of mechanical ventilation, air leak syndrome, hypocarbia, hypercarbia, hypoxemia, combined outcome of death or bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP) were evaluated. The results show that there was no significant difference (p > 0.05) in duration of mechanical ventilation, air leak syndrome, hypocarbia, hypoxemia, BPD between thesetwo groups. The mortality rate, hypercarbia and combined outcome of death or BPD were significantly lower (p < 0.05) in VTV group. We concluded that preterm infants using VTV have less mortality rate, less hypercarbia and decrease in the combined outcome of death or BPD.Volume guarantee (VG) is a form of VTV, in which a microprocessor compares the exhaled VT of the previous inflation and adjusts the working pressure up or down to deliver a target VT. We also have designed a study to assess the effect of VG on high-frequency oscillatory ventilation (HFOV) compared with HFOV alone in preterm infants with hypoxic respiratory failure (HRF).Study 2: The aim of this study was to assess the effect of volume guarantee (VG) on high-frequency oscillatory ventilation (HFOV) compared with HFOV alone in preterm infants with hypoxic respiratory failure (HRF). Fifty-two preterm infants with HRF refractory to conventional mechanical ventilation (CMV) were enrolled in this study. Between June 2012 and February 2016, HFOV alone was used as rescue therapy when CMV failed for 34 infants, whereas HFOV combined with VG was used as rescue therapy for the other 18 infants between March 2016 and December 2017. The results show HFOV combined with VG resulted in a reduction in the combined outcome of death or bronchopulmonary dysplasia (BPD) (p = 0.017) and also a reduction in episodes of hypercarbia (p = 0.010) compared with HFOV alone. We concluded that the preterm infants with HRF ventilated using HFOV combined with VG had a reduced combined outcome of death or BPD and hypercarbia compared with those who received HFOV alone.Conclusion：Base on the results of these two studies we conclude that VTV is feasible and effective to reduce the incidence of hypercarbia, and the combined outcome of death or bronchopulmonary dysplasia (BPD) in preterm infants.