Introduction to High Frequency Ventilation. Michael Haines, MPH, RRT-NPS, AE-C. Objectives. TYPES OF HFV There are four basic types of HFV: High frequency jet ventilation High frequency oscillatory ventilation High frequency percussive ventilation
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Introduction to High Frequency Ventilation
Michael Haines, MPH, RRT-NPS, AE-C
High Frequency Jet Ventilation
HFOV 3100 A – Neonates/Peds
HFVO 3100 B- Adults
High frequency percussive ventilation
»Animal studies of HFV: adequate ventilation can be achieved with VT as low as 1 ml/kg
» Flow streaming reduces effective dead space - only portions of the anatomic DS are used
» Fresh gas penetrates some alveoli
smaller VT at higher PEEP (MAP)
compared to larger VT at lower PEEP
Bulk flow to non compliant airways and alveoli increase distending pressure resulting in air leaks
HFV is a method of mechanical ventilation that employs supra-physiological breathing rates and tidal volumes frequently less than dead space. Because conventional ventilation relies on the production of large pressure changes to induce mass flow of gas in and out of the lungs, it may be associated with deleterious consequences of volume and pressure changes at alveolar level. These include air leaks, such as PIE and pneumothorax, and bronchiolar-alveolar injury leading to chronic lung disease.
»Abundant fresh gas “washes out” expired gas from the airways
»Decreased pCO2 at the gas exchange boundary
Venegas and Fredberg: Crit Care Med 22 (suppl):S49, 1994
1. Direct bulk flow
2. Taylor dispersion
4. Asymmetric velocity
5. Cardiogenic mixing
6. Molecular diffusion
Chang, HK Mechanisms of gas transport during ventilation by high frequency oscillation. ;-563
Respiratory rate >150 bpm
Tidal volume= 1-3 mL/kg
noncompliant ventilator circuits
The 3100A has a diaphragmatically sealed piston driver. It is theoretically capable of ventilating patients up to 30 kg. Tidal volume typically delivered ≈ 1.5-3.0 ml/kg (< dead space). It is a efficient ventilator secondary to an active expiratory phase, but it is not capable of delivering sigh breaths for alveolar recruitment.
↓ delta P / AMP
– Wean FiO2 for arterial saturation > 90%
– Once FiO2 is 60% or less, re-check chest x-ray and if appropriate inflation, begin decreasing the Paw in 2 - 3 cmH2O increments
– Wean Delta-P in 5 cmH2O increments for PaCO2
No Limit Adjust
(PaCO2) is elevated include: increasing the driving pressure in 5 psi
increments to a maximum of 50 psi, increasing the inspiratory fraction in 5 percent increments to a maximum of 40 percent, increasing the frequency in 10 breaths per minute increments to a
maximum of 250 breaths per minute, or adding an another mode of mechanical ventilation
Differences in CMV, HFOV and HFJV pressure waveforms
- Pulmonary interstitial emphysema
- Intraventricular haemorrhage & periventricular leukomalacia
Early application provides protection and reduces incidence of further lung damage
Nitric Oxide (NO), not to be confused with the anesthetic nitrous oxideselective vasodilation properties.
NO is the active metabolite of a number of other vasodilators, including sodium nitroprusside and nitroglycerin.
Produced in all human organ systems, including the nasopharynx and lungs.
In high concentration, NO is profoundly toxic and causes disease identical to Acute Respiratory Distress Syndrome (ARDS).
In presence of oxygen, NO is broken down to form nitrogen dioxide (NO2). In the blood NO interacts with hemoglobin. The byproduct of this reaction produces increased levels of methemoglobin. Methemoglobin will not carry oxygen, and therefore, its level must be closely monitored during NO therapy.
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