Abstract:
:In 11 ventilator-dependent patients, we undertook a head-to-head comparison of patient-ventilator interaction during four ventilator modes: assist-control ventilation (ACV), intermittent mandatory ventilation (IMV), pressure support (PS), and a combination of IMV and PS. Progressive increases in IMV rate and PS level each decreased inspiratory pressure-time product (PTP) (p < 0.0001). These reductions in PTP were greater with PS than with IMV at lower but proportional levels of maximal assistance (p < 0.005). When PS 10 cm H2O was added to a given level of IMV, greater reductions in PTP were achieved not only during intervening (PS) breaths (p < 0.001), but also during mandatory (volume-assisted) breaths (p < 0.0005); this additional unloading during mandatory breaths was proportional to the decrease in respiratory drive (dP/dt) during intervening breaths (r = 0.67, p < 0.0001). Maximal unloading occurred with ACV, achieving more than a fivefold decrease in PTP compared with unassisted breathing. Decreases in PTP were confined to the post-trigger phase, and PTP of the post-trigger phase correlated with dP/dt (r = 0.78, p < 0.0001). Effort during the trigger phase remained constant despite marked changes in drive and intrinsic positive end-expiratory pressure (PEEPi). Ineffective triggering occurred with all modes, and wasted PTP increased with increasing levels of assistance as a result of the accompanying decrease in drive and increase in volume. Breaths preceding nontriggering efforts had shorter respiratory cycle times (p < 0.0005) and expiratory times (p < 0.0001) and higher PEEPi (p < 0.0001), indicating that neural-mechanical asynchrony resulted from inspiratory activity commencing prematurely before elastic recoil pressure had fallen to a level that could be overcome by a patient's muscular effort. Thus, increases in the level of ventilator assistance produced progressive decreases in inspiratory muscle effort and dyspnea,which were accompanied by increases in the rate of ineffective triggering.
journal_name
Am J Respir Crit Care Medauthors
Leung P,Jubran A,Tobin MJdoi
10.1164/ajrccm.155.6.9196100subject
Has Abstractpub_date
1997-06-01 00:00:00pages
1940-8issue
6eissn
1073-449Xissn
1535-4970journal_volume
155pub_type
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journal_title:American journal of respiratory and critical care medicine
pub_type: 杂志文章
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journal_title:American journal of respiratory and critical care medicine
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journal_title:American journal of respiratory and critical care medicine
pub_type: 杂志文章,多中心研究
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更新日期:2000-10-01 00:00:00
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journal_title:American journal of respiratory and critical care medicine
pub_type: 临床试验,杂志文章,随机对照试验
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更新日期:2000-09-01 00:00:00
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pub_type: 杂志文章,多中心研究
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更新日期:2018-02-15 00:00:00
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pub_type: 杂志文章,随机对照试验
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更新日期:2007-08-15 00:00:00
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journal_title:American journal of respiratory and critical care medicine
pub_type: 杂志文章
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更新日期:2020-01-01 00:00:00
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journal_title:American journal of respiratory and critical care medicine
pub_type: 杂志文章
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更新日期:2019-01-15 00:00:00