{"id":24489,"date":"2023-09-09T04:19:00","date_gmt":"2023-09-08T20:19:00","guid":{"rendered":"http:\/\/csccm.org.cn\/?p=24489"},"modified":"2023-09-09T06:20:19","modified_gmt":"2023-09-08T22:20:19","slug":"lancet-respir-med%e5%8f%91%e8%a1%a8%e8%ae%ba%e6%96%87%ef%bc%9a%e9%87%87%e7%94%a8%e8%b6%85%e5%b0%8f%e6%bd%ae%e6%b0%94%e9%87%8f%e9%80%9a%e6%b0%94%e8%bf%9b%e8%a1%8c%e8%82%ba%e4%bf%9d%e6%8a%a4","status":"publish","type":"post","link":"https:\/\/csccm.org.cn\/?p=24489","title":{"rendered":"[Lancet Respir Med\u53d1\u8868\u8ff0\u8bc4]\uff1a\u91c7\u7528\u8d85\u5c0f\u6f6e\u6c14\u91cf\u901a\u6c14\u8fdb\u884c\u80ba\u4fdd\u62a4\uff1a\u65f6\u673a\u5c1a\u65e9"},"content":{"rendered":"\n

COMMENT|ONLINE FIRST<\/a><\/p>\n\n\n\n

Ultra-low tidal volume ventilation for lung protection: not so fast<\/h1>\n\n\n\n

Laura A Buiteman-Kruizinga, <\/a>Marcus J Schultz<\/h3>\n\n\n\n

Lancet Respir Med Published:July 12, 2023DOI:https:\/\/doi.org\/10.1016\/S2213-2600(23)00225-4<\/a><\/h3>\n\n\n\n

Since 2000, following the publication of the ARMA study,1<\/a><\/sup>\u00a0low tidal volume (VT<\/sub>) ventilation (LTV) has been the standard of care for patients with acute respiratory distress syndrome (ARDS). LTV often refers to ventilation with VT<\/sub>\u00a0of 6\u00b70 mL\/kg predicted bodyweight, based on what was compared in the landmark ARMA study (ventilation with VT<\/sub>\u00a0of 6\u00b70 mL\/kg\u00a0vs<\/em>\u00a012\u00b70 mL\/kg predicted bodyweight resulting in a mortality rate of 31%\u00a0vs<\/em>\u00a040%). Several\u2014mostly observational\u2014studies have since confirmed the benefits of ventilation with VT<\/sub>\u00a0of 6\u00b70 mL\/kg predicted bodyweight, including in invasively ventilated patients with COVID-19.2<\/a><\/sup><\/p>\n\n\n\n

Should VT<\/sub> always be as low as 6\u00b70 mL\/kg predicted bodyweight? In medicine, there is never a strategy that is applicable to all patients, and this rule also applies to VT<\/sub>. Notably, in the ARMA study, ventilation with a VT<\/sub> up to 8\u00b70 mL\/kg predicted bodyweight was allowed with LTV. Additionally, most patients in this study were deeply sedated and paralysed, which is important for two reasons. First, maintaining VT<\/sub> as low as 6\u00b70 mL\/kg predicted bodyweight in spontaneously breathing patients is difficult, if not impossible. Second, passive patients might benefit from ventilation with low VT<\/sub> more than active patients because an inactive diaphragm leads to further atelectasis, which reduces end-expiratory lung volume and consequently increases the risk of volutrauma.<\/p>\n\n\n\n

In the past 10 years, it became clear that VT<\/sub>\u00a0should be titrated to the functioning size of the lung. Several observational studies have shown that low driving pressure, the resultant of applied VT<\/sub>\u00a0and the functioning size of lung, has a strong association with outcome even when periods of high driving pressure are short.3<\/a><\/sup> A post-hoc analysis of the Xtravent study4<\/a><\/sup>\u00a0suggested a benefit of a reduction of VT<\/sub>\u00a0to 3\u00b70 mL\/kg predicted bodyweight in patients with severe ARDS, albeit this strategy required extracorporeal CO2<\/sub>\u00a0removal to prevent severe respiratory acidosis.<\/p>\n\n\n\n

In\u00a0The Lancet Respiratory Medicine<\/em>, Jean-Christophe Richard and colleagues5<\/a><\/sup>\u00a0report on a randomised trial that compared ultra-low VT<\/sub>\u00a0ventilation ([ULTV] 4\u00b70 mL\/kg predicted bodyweight; without extracorporeal CO2<\/sub>\u00a0removal) with LTV (6\u00b70 mL\/kg predicted bodyweight) in patients with COVID-19-related ARDS.5<\/a><\/sup>\u00a0ULTV resulted in a significant reduction in marginal mean VT<\/sub>\u00a0(4\u00b79 mL\/kg predicted bodyweight [SE 0\u00b71]\u00a0vs<\/em>\u00a06\u00b72 mL\/kg predicted bodyweight [0\u00b71]; p<0\u00b70001) and driving pressure (9\u00b77 cm H2<\/sub>O [SE 0\u00b73]\u00a0vs<\/em>\u00a011\u00b74 cm H2<\/sub>O [0\u00b73]; p<0\u00b70001). However, there was no difference in the primary outcome (win ratio in the ULTV group 0\u00b785 [95% CI 0\u00b760 to 1\u00b719]; p=0\u00b738), a composite of death at day 90 and ventilator-free days at day 60. The rate of severe respiratory acidosis was higher in patients receiving ULTV (absolute difference 20% [95% CI 9 to 31]; p=0\u00b70004).<\/p>\n\n\n\n

Should Richard and colleagues conclude that ULTV is not beneficial? Is a VT<\/sub>\u00a0of 6\u00b70 mL\/kg predicted bodyweight sufficiently low or was driving pressure in this study already sufficiently low, and a reduction of less than 6\u00b70 mL\/kg predicted bodyweight had no added value? Does ULTV not improve outcomes in patients with COVID-19, even if it is questionable whether this type of ARDS differs from other types of ARDS?6<\/a><\/sup><\/p>\n\n\n\n

Not so fast; maybe ULTV improves outcomes, but we should take more care of the respiratory rate. Studies from 2018 and 2020 have shown associations of mechanical power with outcome.3<\/a>,\u00a0<\/sup>\u00a07<\/a><\/sup>\u00a0Mechanical power is mostly driven by VT<\/sub>, driving pressure, and respiratory rate. One study published in 2021 even suggested that with use of a low VT<\/sub>, mechanical power is only dependent on driving pressure and respiratory rate.8<\/a><\/sup>\u00a0In the study by Richard and colleagues, mechanical power was slightly, but non-significantly, lower with ultra-low VT<\/sub>\u00a0ventilation than with LTV (21\u00b79 J\/min\u00a0vs<\/em>\u00a023\u00b78 J\/min), probably because clinicians chose a higher respiratory rate to compensate for the reduction in minute ventilation (29 breaths per min\u00a0vs<\/em>\u00a025 breaths per min). Could the higher respiratory rate have nulified the potential benefit of ultra-low VT<\/sub>?<\/p>\n\n\n\n

Here, we want to cite a randomised trial published in 1998, 2 years before the ARMA study.9<\/a><\/sup>\u00a0In this study, a so-called protective ventilation strategy consisting of ventilation with a VT<\/sub>\u00a06\u00b70 mL\/kg predicted bodyweight, titrated positive-end expiratory pressure (PEEP) with driving pressure less than 20 cm H2<\/sub>O, and permissive hypercapnia compared with a conventional strategy consisting of ventilation with a VT<\/sub>\u00a012\u00b70 of mL\/kg predicted bodyweight, the lowest PEEP for acceptable oxygenation, and normal arterial CO2<\/sub>concentration resulted in markedly reduced mortality, improved liberation of ventilation, and less barotrauma. The impressive outcome benefit of this protective strategy might not be explained by higher PEEP,10<\/a><\/sup> but the combination of a lower VT<\/sub>\u00a0and permissive hypercapnia resulting in a lower respiratory rate.<\/p>\n\n\n\n

However, Richard and colleagues showed that ULTV resulted in higher CO2<\/sub>\u00a0levels (55\u00b77 Torr\u00a0vs<\/em>\u00a046\u00b70 Torr), so they used permissive hypercapnia? However, arterial pH was not different between the groups and higher CO2<\/sub>\u00a0concentrations were maybe required. Additionally, ventilation with low VT<\/sub>\u00a0combined with high respiratory rate might only be beneficial in patients with ARDS and a very low compliance (ie, when a higher VT<\/sub>\u00a0greatly increases the driving pressure).8<\/a><\/sup>\u00a0Whereas in patients with a relative normal compliance, ventilation with low VT<\/sub>\u00a0combined with high respiratory rate could be harmful, because it greatly increases the mechanical power.<\/p>\n\n\n\n

In conclusion, ventilation is a complex intervention and in the right context, personalised titrations of VT<\/sub>\u00a0and respiratory rate are crucial (figure<\/a>). New studies are needed with the best combination of VT<\/sub>\u00a0and respiratory rate, maybe by using driving pressure and mechanical power as targets. As a start, clinicians could consider accepting a higher arterial CO2<\/sub>\u00a0or low pH level more often.<\/p>\n\n\n\n

\"\"\/<\/figure>\n","protected":false},"excerpt":{"rendered":"

COMMENT|ONLINE FIRST Ultra-low tidal volume ventilation […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[24,23],"tags":[],"_links":{"self":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/24489"}],"collection":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=24489"}],"version-history":[{"count":3,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/24489\/revisions"}],"predecessor-version":[{"id":24493,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=\/wp\/v2\/posts\/24489\/revisions\/24493"}],"wp:attachment":[{"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24489"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24489"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/csccm.org.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24489"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}