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What is high-frequency oscillation 1
国立成育医療研究センター
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概要
高頻度振動換気（HFO）の理論と歴史を解説します。平均気道内圧（mPaw）による酸素化と、主に振幅（ΔP）で決まる一回換気量による二酸化炭素除去という、独特なガス交換の原理を学習。通常換気とは異なる設定の基本を整理します。
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研修医／専攻医／専門医
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高頻振動の理論と歴史について
#1.
What is high-frequency oscillation? Part 1: Theory and History Satoshi Nakagawa
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目次 • HFOとその歴史 • HFOでのガス交換 • HFOの設定調節
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PICUで必要な知識や⼿技、 対応のポイントをスライド形式でまとめています ✓ 系統別に学ぶ⼩児集中治療の知識 ✓ ⼿技（挿管‧エコー等）の習得 ✓ ショック‧外傷など緊急対応の理解 スライドで詳しく学ぶ https://slide.antaa.jp/special/pediatric-intensive-care
高頻振動の基本概念とガス流
高頻振動と従来の換気法の比較
高頻振動における圧-容積ループの解析
高頻振動によるCO2除去のメカニズム
高頻振動の肺保護戦略とその効果
#4.
What is HFO? ■High-frequency oscillation; HFO ■High-frequency •Faster than 1 to 2 Hz (60 to 120/min) ■Oscillation •Active in inspiration and expiration •Tidal volumes are smaller than anatomical dead space • but the reality may be different in some countries
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Gas flow in HFO Piston pump (diaphragm) Fresh gas flow
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Airway pressure waveforms（PCV vs. HFO） Airway Pressure (Paw) What is the frequency? PIP mPaw PEEP 1 sec t
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Ventilation by high-frequency oscillation D J Bohn, K Miyasaka, B E Marchak, W K Thompson, A B Froese, A C Bryan The effect of applying a high-frequency small-volume sinusoidal oscillation at the airway was investigated in anesthetized apneic beagle dogs (mean wt 11 kg, mean VDphys 6.6 +/- 0.6 ml/kg). Oscillations generated by a piston in a cylinder were transmitter to the lungs through an uncuffed endotracheal tube (4.5 mm ID, 6.0 mm OD), which allowed a substantial leak back through the vocal cords. A bias flow of fresh gas presented inspired air to the midtracheal level. The minimum distal airway pressure (measured at the end of the endotracheal tube) was maintained between 0 and 2 cmH2O. Peak airway pressures were 4-8 cmH2O. The optimal frequency for CO2 elimination was 15 Hz. Using volumes of 1.9 ml/kg (range 1.7-2.3) at this frequency the mean PaCO2 was 33.1 +/- 0.5 Torr. In four dogs breathing 100% O2 the PaO2 was 594 +/- 9 Torr during spontaneous ventilation and 580 +/- 9 Torr
#11.
Slutsky AR, Drazen JM. Ventilation with small tidal volume. N Engl J Med 2002, 347;630-631.
#12.
High-frequency oscillatory ventilation compared with conventional mechanical ventilation in the treatment of respiratory failure in preterm infants. HIFI Study Group N Engl J Med 1989; 320:88-93.
#13.
A multicenter randomized trial of high frequency oscillatory ventilation as compared with conventional mechanical ventilation in preterm infants with respiratory failure. Y Ogawa 1, K Miyasaka, T Kawano, S Imura, K Inukai, K Okuyama, K Oguchi, H Togari, H Nishida, J Mishina Early Hum Dev 1993; 32:1-10.
#14.
Airway pressure waveforms（PCV vs. HFO） Airway Pressure (Paw) What is the frequency? PIP mPaw PEEP 1 sec t
#15.
Pressure-Volume Loops •mPaw of HFO • Is it OK at the same level of the one of conventional mode? • It is recommended to set 3 to 5 cmH2O higher than the one of conventional mode. • Why? • Conventional mode has PIP effect, but HFO does not.
#16.
Ventilation in HFO • CO2 removal • Conventional mode • CO2 elimination ∝ minute ventilation (VT x RR) • HFO • CO2 elimination ∝ f x (VT)2 • 10 Hz and VT=100 ml vs. 12 Hz and VT=80 ml • 10 x 1002 vs. 12 x 802 • 10 X 10000 vs. 12 x 6400 • 10 x 104 vs. 7.68 x 104
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Comparison of lung protection strategies using conventional and HFO ventilation. Imai Y, Nakagawa S, Ito Y, et al. J Appl Physiol 2001, 91:1836-1844.
#19.
Imai Y, et al. J Appl Physiol 2001, 91:1836-1844.
#20.
Imai Y, et al. J Appl Physiol 2001, 91:1836-1844. Table. Alveolar pathological score ----------------------------------------------Group Total Score ----------------------------------------------MVLP 2.62 ± 0.35* LVHP 2.21 ± 0.51* HFOV 1.01 ± 0.40 ----------------------------------------------- Values are means ± SD; n = 24 lung sections per group. Score of 0 = minimal (little) damage; 1+ = mild damage; 2+ = moderate damage; 3+ = severe damage; and 4+ = maximal damage. MVLP, moderate tidal volume, low positive end-expiratory pressure (PEEP); LVHP, low tidal volume, high PEEP; HFOV, high-frequency oscillatory ventilation. * P < 0.01 compared with HFOV group. The pathological score was higher in the MVLP and LVHP groups than in the HFOV group (P < 0.01). No significant differences were seen between the MVLP and LVHP groups.
#21.
Photomicrographs of membranous bronchioles from the animals in the MVLP (A), LVHP (B), and HFOV groups (C) (Masson's trichrome stain; original magnification x400) Imai, Y. et al. J Appl Physiol 91: 1836-1844, 2001. Copyright ©2001 American Physiological Society
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Summary • HFO: high-frequency oscillation • Started at Dr. Bryan’s team in 1970’s. • Oxygenation: lung volume maintained by mean airway pressure • Ventilation • CO2 elimination ∝ f x (VT)2 • Ultimate lung protective ventilation mode (at least at animal models) • Lower frequencies can provide larger tidal volumes, but those may be lung-injurious. • higher frequencies are preferred even in children and adults
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