Shelledy D C, Rau J L, Thomas-Goodfellow L
Department of Respiratory Care, University of Texas Health Science Center at San Antonio 78284-7784, USA.
Heart Lung. 1995 Jan-Feb;24(1):67-75. doi: 10.1016/s0147-9563(05)80097-4.
To quantify the ventilatory efficiency of different modes of mechanical ventilation used to achieve full ventilatory support in normal subjects. Modes compared were assist-control, synchronized intermittent mandatory ventilation (SIMV), and SIMV with 10 cm H2O (0.98 kPA) of pressure support.
Prospective, randomized blocks repeated measures design. Subjects served as their own controls.
A university affiliated pulmonary laboratory.
Ten healthy volunteers, aged 31-54 years.
Minute volume, respiratory rate, average tidal volume, oxygen consumption, and ventilatory equivalent.
Baseline spontaneous ventilation data collection was followed by mechanical ventilation by mouthpiece in each of three modes in a random sequence. All modes used a machine set rate of 12 breaths per minute, VT of 10 cc/kg of ideal body weight, inspiratory time of 1 second, square wave flow pattern and a sensitivity of -1 cm H2O (-0.09806 kPa) to achieve full ventilatory support. Data were collected continuously for 5 minutes and the mean values were reported. Ventilatory equivalent for oxygen is a measure of the efficiency of the ventilatory pump at various work loads and was calculated by dividing VE (BTPS) by the VO2 (STPD).
There were significant differences by mode of mechanical ventilation in average tidal volume (p = 0.02), minute volume (p = 0.02), oxygen consumption (p = 0.04), and ventilatory equivalent (p = 0.01) using ANOVA. There was no significant difference (p = 0.66) by mode of ventilation in respiratory rate. Pairwise follow-up comparisons for these variables found that SIMV with pressure support produced a significantly greater average tidal volume, minute volume, oxygen consumption, and ventilatory equivalent than SIMV alone. SIMV with pressure support also produced a significantly greater minute volume and ventilatory equivalent than assist-control. There were no significant differences between assist-control and SIMV. All three modes produced a lower ventilatory equivalent and higher oxygen consumption than spontaneous breathing.
SIMV with pressure support significantly increased minute volume and ventilatory equivalent when compared with assist-control or SIMV alone, and thus was the most efficient mode of full ventilatory support for our subjects. We found no difference in ventilatory efficiency between assist-control and SIMV. All three mechanical modes were less efficient for our subjects than spontaneous breathing. The inspiratory time of 1 second used in this study, although common in clinical practice, may be inadequate for some patients.
量化用于为正常受试者提供完全通气支持的不同机械通气模式的通气效率。比较的模式有辅助控制通气、同步间歇指令通气（SIMV）以及压力支持为10 cm H₂O（0.98 kPa）的SIMV。
前瞻性、随机区组重复测量设计。受试者自身作为对照。
一所大学附属医院的肺功能实验室。
10名年龄在31至54岁之间的健康志愿者。
分钟通气量、呼吸频率、平均潮气量、耗氧量和通气当量。
先收集基线自主通气数据，然后通过咬嘴以随机顺序依次采用三种模式进行机械通气。所有模式的机器设定频率均为每分钟12次呼吸，潮气量为理想体重每千克10 cc，吸气时间为1秒，采用方波气流模式，灵敏度为-1 cm H₂O（-0.09806 kPa）以实现完全通气支持。持续收集5分钟的数据并报告平均值。氧通气当量是衡量通气泵在不同工作负荷下效率的指标，通过将VE（BTPS）除以VO₂（STPD）来计算。
使用方差分析发现，不同机械通气模式在平均潮气量（p = 0.02）、分钟通气量（p = 0.02）、耗氧量（p = 0.04）和通气当量（p = 0.01）方面存在显著差异。不同通气模式在呼吸频率方面无显著差异（p = 0.66）。对这些变量进行两两后续比较发现，压力支持的SIMV产生的平均潮气量、分钟通气量、耗氧量和通气当量显著高于单纯的SIMV。压力支持的SIMV产生的分钟通气量和通气当量也显著高于辅助控制通气。辅助控制通气和SIMV之间无显著差异。与自主呼吸相比，所有三种模式的通气当量均较低，耗氧量均较高。
与辅助控制通气或单纯的SIMV相比，压力支持的SIMV显著增加了分钟通气量和通气当量，因此是为我们的受试者提供完全通气支持的最有效模式。我们发现辅助控制通气和SIMV在通气效率方面无差异。对于我们的受试者，所有三种机械通气模式的效率均低于自主呼吸。本研究中使用的1秒吸气时间虽然在临床实践中很常见，但对某些患者可能并不足够。
