急性呼吸窘迫综合征中，在分钟通气量和吸气流量恒定的情况下降低潮气量的生理效应。

Physiological effects of reduced tidal volume at constant minute ventilation and inspiratory flow rate in acute respiratory distress syndrome.

作者信息

Kiiski R, Kaitainen S, Karppi R, Takala J

机构信息

Department of Intensive Care, Kuopio University Hospital, Finland.

出版信息

Intensive Care Med. 1996 Mar;22(3):192-8. doi: 10.1007/BF01712236.

DOI:10.1007/BF01712236

PMID:8727431

Abstract

OBJECTIVE

To assess the effect of changes in tidal volume (VT) with a constant inspiratory flow and minute ventilation (VE) on gas exchange and oxygen transport in acute respiratory distress syndrome (ARDS).

DESIGN

A crossover study of three VT in two study groups, using patients as their own controls.

SETTING

A medical-surgical intensive care unit in a tertiary care center.

PATIENTS

Eight patients with ARDS and seven postoperative cardiac surgery patients with uncomplicated recoveries were studied during volume-controlled mechanical ventilation.

INTERVENTIONS

During controlled mechanical ventilation, patients were first ventilated with a VT of 9-11 ml/kg. VT was then increased to 12-14 ml/kg (+ 25%) for 30 min and subsequently decreased to 6-8 ml/kg (- 25%) for 30 min by adjusting the respiratory rate (RR) while the inspiratory flow rate, VE, and inspiratory duty cycle (TL/T(TOT)) were kept constant. At the end, patients were ventilated with the baseline settings for another 30 min.

MEASUREMENTS AND RESULTS

VE, carbon dioxide production (VCO2) and oxygen consumption (VO2) were measured continuously with a gas exchange monitor, and cardiac output and arterial and mixed venous blood samples were taken at the end of each 30-min period to assess CO2 removal and oxygen transport. Alveolar minute ventilation (VA) and the deadspace to tidal volume ratio (VD/VT) were calculated from the Bohr equation. Despite large changes in VT, arterial oxygenation (PaO2) and oxygen transport (DO2) were unchanged throughout the study. When VT was increased, physiological VD increased from 448 +/- 34 ml to 559 +/- 46 ml (mean +/- SE) in ARDS (P < 0.001) and from 281 +/- 22 ml to 357 +/- 35 ml in CABG (P < 0.05). With the small VT, VD decreased to 357 +/- 22 ml in ARDS (P < 0.01), and to 234 +/- 24 ml in CABG (P < 0.05). In ARDS, VD/VT decreased from 0.57 +/- 0.03 to 0.55 +/- 0.03 (P < 0.05) with the large VT, and increased to 0.60 +/- 0.03 (P < 0.01), when VT was reduced. In CABG, VD/VT did not change significantly. ARDS patients had a higher PaCO2 than cardiac patients (P < 0.001), and only minor changes in PaCO2 were observed (for ARDS and CABG respectively, baseline 5.9 +/- 0.3 kPa and 4.1 +/- 0.1 kPa, large VT 5.7 +/- 0.3 kPa and 4.1 +/- 0.2 kPa, small VT 6.2 +/- 0.3 kPa and 4.2 +/- 0.2 kPa; P < 0.05).

CONCLUSIONS

Tidal volumes can be reduced to 6-8 ml/kg in ARDS patients without compromising oxygen transport, while adequate CO2 elimination can be maintained.

摘要

目的

评估在吸气流量和分钟通气量（VE）恒定的情况下，潮气量（VT）变化对急性呼吸窘迫综合征（ARDS）患者气体交换和氧输送的影响。

设计

一项交叉研究，在两个研究组中设置三种VT水平，以患者自身作为对照。

地点

一家三级医疗中心的内科-外科重症监护病房。

患者

8例ARDS患者和7例术后心脏手术恢复良好的患者在容量控制机械通气期间接受研究。

干预措施

在控制机械通气期间，患者首先以9 - 11 ml/kg的VT进行通气。然后将VT增加至12 - 14 ml/kg（增加25%），持续30分钟，随后通过调整呼吸频率（RR）将VT降至6 - 8 ml/kg（降低25%），持续30分钟，同时保持吸气流量、VE和吸气占空比（TL/T(TOT)）恒定。最后，患者以基线设置再通气30分钟。

测量与结果

使用气体交换监测仪连续测量VE、二氧化碳产生量（VCO2）和氧消耗量（VO2），并在每个30分钟时段结束时采集心输出量以及动脉和混合静脉血样本，以评估二氧化碳清除和氧输送情况。根据玻尔方程计算肺泡分钟通气量（VA）和死腔与潮气量之比（VD/VT）。尽管VT有较大变化，但在整个研究过程中动脉氧合（PaO2）和氧输送（DO2）均未改变。当VT增加时，ARDS患者的生理死腔从448±34 ml增加至559±46 ml（平均值±标准误）（P < 0.001），心脏搭桥手术（CABG）患者从281±22 ml增加至357±35 ml（P < 0.05）。在小VT时，ARDS患者的VD降至357±22 ml（P < 0.01），CABG患者降至234±24 ml（P < 0.05）。在ARDS中，大VT时VD/VT从0.57±0.03降至0.55±0.03（P < 0.05），VT降低时则升至0.60±0.03（P < 0.01）。在CABG中，VD/VT无显著变化。ARDS患者的PaCO2高于心脏手术患者（P < 0.001），且观察到PaCO2仅有微小变化（ARDS和CABG患者的基线值分别为5.9±0.3 kPa和4.1±0.1 kPa，大VT时为5.7±0.3 kPa和4.1±0.2 kPa，小VT时为6.2±0.3 kPa和4.2±0.2 kPa；P < 0.05）。