Assessing High Frequency Oscillatory Ventilation-Part Two

This is part 2 of our series focusing on assessing high-frequency oscillatory ventilation. Check out part one here.

Due to difficulties in assessing the outputs (from the patient’s perspective) of HFOV ventilators, many analysts have resorted to monitoring pressure outputs. The theory is that so long as an adequate FIO2 (fraction of inspired oxygen) reaches the patient and the pressures remain safe, the ventilation is a success. Unfortunately, this method does little to help us understand HFOV on a deeper level, and without this understanding, it is difficult to know how the science and practice of modern ventilation will progress in the future.

Why is it important to understand volume and flow parameters?

Measuring ventilated volume is a common way of fact-checking a ventilator. For the display on a ventilator to show an accurate delivered volume the vast majority of the unit’s internal systems must be working properly. Flow, similarly, can offer insight into what might be going wrong with one of these ventilators, should it malfunction or require calibration. These parameters are sometimes overlooked in testing as the ventilator itself will display variations of them. Other variables make themselves in apparent when the problem of calibration is approached scientifically. Compressible volume in the airway and lungs can damage the accuracy of calculations performed by the ventilator, and without the ability to control airway resistance and lung compliance to a known value outputs are not always consistent.

The patient’s perspective.

Changes in flow and volume must be explored from the perspective of the patient as a way to understand, calibrate, and tweak ventilators. This sort of testing, however, requires a new type of test lung device capable of measuring flows, volumes, and pressures at different points throughout the respiratory system of a simulated patient.

We’ll get into test lung devices in part three. In the meantime, if you have any questions about the use of high-frequency oscillatory ventilation, don’t hesitate to contact Michigan Instruments anytime.

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Using High Frequency Oscillatory Ventilation – Part Three

In using high frequency oscillatory ventilation (HFOV) tidal volume and LPM (flow) values can be exceptionally difficult to monitor. Several third-party devices have been developed to monitor this, but due to a lack of any solid standard of operation, it is still considered to increase patient risk over conventional ventilation. Regardless, let’s take a look at its current applications and uses.

Currently, HFOV has found a niche in non-conventional settings, primarily in the treatments of neonatal patients and some adult cases where the patient is considered to be past the point at which traditional ventilation would be beneficial. It is important to note that the largest fear surrounding HFOV concerns is the lack of understanding of the delivered tidal volume and other common parameters used to describe breaths.

HFOV, in some medical systems, has become a “last resort” treatment option.

The Benefit

It doesn’t expose the lungs of a patient to the same dramatic swings in pressure and flow that a standard ventilator does. Damaged lungs can be further exacerbated by such swings, and the underdeveloped lungs of premature infants are especially susceptible.

The Drawbacks

HFOV is such a departure from a standard breath that it invites mistrust, and without the ability to really explore the WHY of the effectiveness of HFOV, such a departure is difficult to justify. It is often found, in medical studies, that the human body is very well adapted to its’ natural processes.

The mention of a ventilator forcing hundreds of miniature breaths onto a patient every minute is, admittedly, a bit intimidating. It could, however, offer some excellent treatment options to future patients. We aren’t saying advocating to press this sort of treatment—not until we find a way to confirm effectiveness and minimize risk to patients—but we do believe that the benefits of better understanding this non-conventional form of ventilation would far outweigh the cost.

Review part one and part two of the series and contact us with any follow-up questions or comments.

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