Keszler M, Nassabeh-Montazami S, Abubakar K
Department of Pediatrics, Division of Neonatology, Georgetown University Hospital, 3800 Reservoir Rd NW, Washington, DC 20007, USA.
Arch Dis Child Fetal Neonatal Ed. 2009 Jul;94(4):F279-82. doi: 10.1136/adc.2008.147157. Epub 2008 Dec 5.
Volume-targeted ventilation is used in neonates to reduce volutrauma and inadvertent hyperventilation. Little is known about appropriate tidal volume (V(T)) settings in extremely low birthweight (ELBW) infants who remain intubated for extended periods.
The V(T) required to maintain adequate partial pressure of carbon dioxide (P(CO2) levels changes as the underlying disease evolves in infants ventilated for prolonged periods.
To obtain normative data for V(T) associated with normocapnia in ELBW infants ventilated with Volume Guarantee over the first 3 weeks of life.
DESIGN/METHODS: Set and measured V(T), peak pressure, respiratory rate and blood gas values were extracted from the records of babies <800 g born January 2003 to August 2005 and ventilated with Volume Guarantee. Data were collected at the time of each blood gas measurement during days 1-2, 5-7 and 14-21. Only the V(T) corresponding to P(CO2) values within a defined normal range were included. Descriptive statistics were used to define the patient cohort. Mean V(T) and P(CO2) for each patient during each epoch was calculated, and these values were analysed by repeated-measures analysis of variance.
Twenty-six infants, mean (SD) birth weight 615 (104) g, were included. A total of 828 paired blood gas and V(T) sets were analysed: days 1-2 = 251; days 5-7 = 185; days 14-17 = 216; days 18-21 = 176. P(CO2) values (mean (SD)) rose from 44.0 (5.4) mm Hg on days 1-2 to 46.3 (5.2) mm Hg on days 5-7 and remained stable during days 14-17 and 18-21 (53.9 (6.8) and 53.9 (6.2) mm Hg, respectively). Mean exhaled V(T) rose from 5.15 (0.62) ml/kg on day 1 to 5.24 (0.71) ml/kg on days 5-7, 5.63 (1.0) ml/kg on days 14-17, and 6.07 (1.4) ml/kg on days 18-21 (p<0.05).
Despite permissive hypercapnia, V(T) requirement rises with advancing postnatal age in ELBW infants. The increase is greatest during the third week of life, which is probably due to distension of the upper airways (acquired tracheomegaly) and increasing heterogeneity of lung inflation (increased alveolar dead space).
容量目标通气用于新生儿以减少容积伤和无意的通气过度。对于长时间插管的极低出生体重（ELBW）婴儿，合适的潮气量（V(T)）设置知之甚少。
在长时间接受通气的婴儿中，维持足够二氧化碳分压（P(CO2)）水平所需的V(T)会随着潜在疾病的发展而变化。
获取出生体重＜800g、在出生后第1个3周内接受容量保证通气的ELBW婴儿中与正常二氧化碳水平相关的V(T)的规范数据。
设计/方法：从2003年1月至2005年8月出生且体重＜800g、接受容量保证通气的婴儿记录中提取设定和测量的V(T)、峰值压力、呼吸频率及血气值。在第1 - 2天、5 - 7天和14 - 21天每次进行血气测量时收集数据。仅纳入对应于定义正常范围内P(CO2)值的V(T)。采用描述性统计来定义患者队列。计算每个患者在每个时期的平均V(T)和P(CO2)，并通过重复测量方差分析对这些值进行分析。
纳入26例婴儿，平均（标准差）出生体重615（104）g。共分析828对血气和V(T)数据组：第1 - 2天 = 251组；第5 - 7天 = 185组；第14 - 17天 = 216组；第18 - 21天 = 176组。P(CO2)值（平均（标准差））从第1 - 2天的44.0（5.4）mmHg升至第5 - 7天的46.3（5.2）mmHg，并在第14 - 17天和第18 - 21天保持稳定（分别为53.9（6.8）和53.9（6.2）mmHg）。平均呼出V(T)从第1天的5.15（0.62）ml/kg升至第5 - 7天的5.24（0.71）ml/kg，第14 - 17天为5.63（1.0）ml/kg，第18 - 21天为6.07（1.4）ml/kg（p<0.05）。
尽管采用允许性高碳酸血症，但ELBW婴儿的V(T)需求随出生后年龄增长而增加。在出生后第3周增加最大，这可能是由于上呼吸道扩张（获得性气管扩大）和肺膨胀异质性增加（肺泡死腔增加）所致。
