Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano University , Milan , Italy.
Neonatal Intensive Care Unit, Fondazione MBBM-ASST-Monza, Monza, Italy.
J Appl Physiol (1985). 2019 Apr 1;126(4):928-933. doi: 10.1152/japplphysiol.01086.2018. Epub 2019 Feb 7.
The distribution of ventilation during high-frequency ventilation (HFV) is asynchronous, nonhomogeneous, and frequency dependent. We hypothesized that differences in the regional distribution of ventilation at different oscillatory frequencies may affect gas exchange efficiency. We studied 15 newborn infants with a median gestational age of 28.9 (26.4-30.3) wk and body weight of 1.0 (0.8-1.4) kg. Five ventilation frequencies (5, 8, 10, 12, and 15 Hz) were tested, keeping carbon dioxide diffusion coefficient constant. The displacements of 24 passive markers placed on the infant's chest wall were measured by optoelectronic plethysmography. We evaluated the amplitude and phase shift of displacements of single markers placed along the midline and the regional displacements of the chest wall surface. Blood gases were unaffected by frequency. Chest wall volume changes decreased from 1.6 (0.4) ml/kg at 5 Hz to 0.7 ml/kg at 15 Hz. At all frequencies, the abdomen (AB) oscillated more markedly than the ribcage (RC). The mean (SD) AB/RC ratio was 1. 95 (0.7) at 5 Hz, increased to 2.1 (1.3) at 10 Hz, and then decreased to 1.1 (0.5) at 15 Hz ( P < 0.05 vs. 10 Hz). Volume changes in the AB lagged the RC and this phase shift increased with frequency. The AB oscillated more than the RC at all frequencies. Regional oscillations were highly inhomogeneous up to 10 Hz, and they became progressively more asynchronous with increasing frequency. When the carbon dioxide diffusion coefficient is held constant, such differences in regional chest wall expansion do not affect gas exchange. NEW & NOTEWORTHY We characterized the regional distribution of chest wall displacements in infants receiving high-frequency oscillatory ventilation at different frequencies. When carbon dioxide diffusion coefficient is held constant, there is no combination of frequency and tidal volume that optimizes gas exchange. The relative displacement between different chest wall compartments is not affected by frequency. However, at high frequencies, chest wall displacements are lower, with the potential to reduce total and regional overdistension without affecting gas exchange.
高频通气（HFV）期间的通气分布是异步的、不均匀的和频率依赖的。我们假设在不同的振荡频率下，通气的区域分布差异可能会影响气体交换效率。我们研究了 15 名胎龄中位数为 28.9（26.4-30.3）周、体重为 1.0（0.8-1.4）kg 的新生儿。保持二氧化碳扩散系数不变，测试了 5 种通气频率（5、8、10、12 和 15 Hz）。通过光电体积描记法测量 24 个被动标记物放置在婴儿胸壁上的位移。我们评估了沿中线放置的单个标记物的位移幅度和相移以及胸壁表面的区域位移。血气不受频率影响。胸壁容积变化从 5 Hz 时的 1.6（0.4）ml/kg 下降到 15 Hz 时的 0.7 ml/kg。在所有频率下，腹部（AB）的波动比肋骨（RC）明显。AB/RC 的平均值（SD）为 5 Hz 时为 1.95（0.7），增加到 10 Hz 时为 2.1（1.3），然后降低到 15 Hz 时为 1.1（0.5）（P <0.05 与 10 Hz 相比）。AB 的容积变化滞后于 RC，随着频率的增加，这种相位滞后增加。在所有频率下，AB 的波动都大于 RC。直到 10 Hz，区域振荡高度不均匀，随着频率的增加，它们变得越来越不同步。当二氧化碳扩散系数保持恒定时，区域胸壁扩张的这种差异不会影响气体交换。新的和值得注意的是，我们描述了在不同频率下接受高频振荡通气的婴儿的胸壁位移的区域分布。当二氧化碳扩散系数保持恒定时，没有一种频率和潮气量的组合可以优化气体交换。不同胸壁隔室之间的相对位移不受频率影响。然而，在高频下，胸壁位移较低，有可能在不影响气体交换的情况下减少总容积和区域性过度扩张。
