Calderini E, Confalonieri M, Puccio P G, Francavilla N, Stella L, Gregoretti C
Terapia Intensiva Malattie Infettive CSL, IRCCS H San Raffaele, Milano, Italy.
Intensive Care Med. 1999 Jul;25(7):662-7. doi: 10.1007/s001340050927.
Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure.
Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol.
Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20' conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm H2O, PEEP of 5 cm H2O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (delta Pes) were measured to evaluate the patient's respiratory effort. A subjective "comfort score" and the difference between patient and machine respiratory rate [delta RR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction.
Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H2O) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, delta Pes, and delta RR(p-v) when compared to NIPS-Vfc [230 +/- 41 (SE) vs 376 +/- 72 cm H2O.s.min-1; 8 +/- 2 vs 13 +/- 2 cm H2O; 1 +/- 1 vs 9 +/- 2 br.min-1; respectively] with a concomitant significant improvement of the "comfort score".
In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV.
在无创通气期间，面罩周围很可能会出现漏气，尤其是在需要长时间通气治疗时。有人提出，当使用吸气压力支持通气（PSV）时，面罩漏气可能会损害呼气触发循环机制。本研究的目的是比较在严重低氧血症性呼吸衰竭的无创吸气压力支持通气（NIPSV）过程中，两种不同的呼气循环机制（时间切换与流量切换）对患者-呼吸机同步性的短期影响。
六名因获得性免疫缺陷综合征（AIDS）相关机会性肺炎导致急性肺损伤（ALI）的患者纳入本方案。
首先让每位受试者佩戴文丘里氧面罩进行自主呼吸（SB），随后随机接受20分钟的传统流量切换（NIPSVfc）或时间切换吸气压力支持通气（NIPSVtc）。预设参数为：吸气压力10 cm H₂O，呼气末正压5 cm H₂O，吸入氧分数与SB时相同。避免面罩紧密贴合，以便于面罩周围漏气。测量食管压力时间乘积（PTPes）和潮气量波动（δPes）以评估患者的呼吸努力。根据食管和气道压力曲线计算主观“舒适度评分”以及患者与机器呼吸频率之差[δRR(p-v)]，作为患者-机器相互作用的指标。
六名患者中有五名出现面罩漏气。内源性呼气末正压（PEEPi）值（<1.9 cm H₂O）排除了明显的呼气肌活动。与NIPS-Vfc相比，NIPSVtc显著降低了PTPes、δPes和δRR(p-v) [分别为230±41（SE）对376±72 cm H₂O·s·min⁻¹；8±2对13±2 cm H₂O；1±1对9±2次/分钟]，同时“舒适度评分”有显著改善。
在存在漏气的情况下，在NIPSV期间时间切换呼气触发比流量切换呼气触发能提供更好的患者-机器相互作用。
