3100B HFOV Operator Manual - CareFusion

3100B HFOV 77
Chapter 9 Clinical Guidelines
Treatment Strategies
The 3100B is not indicated for use with infants or small children. The clinical guidelines described below
reflect the strategies and applications developed during the course of the Multicenter Oscillatory ARDS
Trial (MOAT II) Prospective Randomized Control Trial.
A recently published trial by the National Institutes of Health ARDS network, comparing a “lung
protective” strategy of lower tidal volumes (< 6 ml/kg) and plateau pressures (< 30 cm H 2O) with a
higher tidal volume strategy, reported an absolute mortality reduction of 9%. High frequency oscillatory
ventilation (HFOV) is an alternative method of ventilation, which theoretically achieves the goals of lung
protective ventilation. HFOV achieves gas exchange by applying a constant mean airway pressure,
higher than that usually applied during conventional ventilation. Thus, HFOV allows maintenance of
alveolar recruitment while potentially avoiding both the cyclic closing and opening of alveolar units as
well as the high peak airway pressures that occur with conventional ventilation techniques.
Adjusting the Controls to
Execute the Treatment Strategies
The strategies are easy to implement because, for most clinical situations, only two of the 3100B's five
controls are employed: mean airway pressure and oscillatory pressure amplitude (∆P). The other three,
Bias Flow, Frequency and % Inspiratory Time, are rarely changed during the course of treatment, as
explained below.
Bias Flow
A continuous flow of fresh, humidified gas from a standard humidifier and Air/Oxygen blender is a
fundamental requirement for replenishing oxygen and removing carbon dioxide from the patient circuit.
In most applications the flow rate should be set at not less than 20 l/min. However, the effect of
increasing this control is relatively benign unless exceptionally high oscillatory amplitudes are required.
In these cases, bias flow should be higher to insure that the patient circuit clearance flow is greater than
the patient’s oscillatory flow. If the bias flow is inadequate, the patient circuit's effective dead space will
increase and diminish the ventilation affect being sought by increasing the oscillatory amplitude (∆P).
Additionally, when operating the ventilator at high oscillatory amplitudes it may be necessary to
increase the flow to maintain mean airway pressure. Although changes in Bias Flow will cause changes
in Pa, in practice a flow rate of 20–40 l/min is typical.
If signs of carbon dioxide retention persist, increase the bias flow in increments of 5 l/min as frequently
as every 15 minutes. Remember that the Pa Adjust control will have to be turned counterclockwise to
compensate for the increased flow, and maintain the desired Pa.
Frequency
For adult applications the typical starting frequency is 5Hz. In patients who present with refractory
hypercapnia with maximal oscillatory amplitude, the frequency is then decreased incrementally to
improve ventilation.
% Inspiratory Time
For most therapeutic situations, 33% has been found to be effective for most patients. This control
typically does not change during the course of treatment.
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