This device extends the basic concept of respiratory visual biofeedback breathing prompting of the Biofeedback Incentive Systemtm (BIStm) system into the Metered Dose Inhaler arena.
An additional important advance is the ability to define and regulate breathing patterns precisely within the Total Lung Capacity. In other words, a breathing pattern may be started at a known point within the Total Lung Capacity.
There is no dispute that correct MDI inhalation technique is critically important in the delivery of aerosol medication. Indeed, even with proper MDI use (without an adjunctive so-called "Spacer" device) only a maximum of about 15% of the medication spray is actually delivered to the lung. And numerous journal articles note the high frequency of improper MDI use, and particularly so among the young and elderly populations. Likewise the difficulty of training patients in proper technique, and having these techniques retained and used on a long term basis.
Sierra Biotechnology's MDI Training device obviates these problems by:
The overall MDI Training system is as noted:
Note the MDI is attached to a Flowmeter, which in turn inputs data to a computer. A microswitch senses activation of the MDI. The patient observes the computer screen, and interacts with the visual biofeedback prompts. Screen #1 establishes the lung volume parameters, and defines the point the patient must exhale to, before beginning the MDI inhalation breath. On achieving this expiration volume, the computer display switches to Screen #2, which is the MDI prompting program.
ESTABLISHING LUNG VOLUME PARAMETERS
All breathing maneuvers must start somewhere within the available lung volume, and take place within a range of lung volume from that starting point. Establishing these lung volumes is critically important for proper breathing techniques. The mechanical properties of the lung vary greatly, depending on the volumetric position the particular breathing maneuver takes place. For example, a proper MDI inhalation breath cannot take place if the patient has already halfway inspired. This MDI training device permits precise setting of lung volume parameters.
This is achieved traditionally by establishing the patient's Resting Expiratory Level (REL), the slight pause at the end of expiration. As noted in the first stylized diagram, resting Tidal Volume respiration is displayed in a mid-field display. Below is a dotted line, which is moved manually by the operator to visually match the average REL point as noted in the right hand diagram. This locks the MDI Trainer system to the patient's relative REL lung volume.
From a previously determined Vital Capacity, the operator then enters a value of how far below the REL the patient should exhale, and how large a breath is to be inhaled from that point. This becomes the MDI Inhalation Breath, to a desired point of maximal inspiration. Also entered is the desired Inspiratory Flow Rate, the Breath Holding Time at full inspiration, and the Expiratory Flow Rate. After entering this data the following diagrams appear.
Note there are now two dotted lines. The upper one is the REL line, and may again be adjusted immediately before the MDI breath if there has been any "drift" of the baseline REL. This is shown in the right hand picture. The lower dotted line is the volumetric level the patient must exhale down to, in order to begin the MDI inhalation breath on the next screen display.
The patient is now ready to begin the MDI training. They are instructed to gently exhale, down to the lower dotted line. Immediately on achieving this point, the screen switches to the MDI prompting program on Screen 2, which is the MDI Prompting Display.
THE MDI PROMPTING DISPLAY
This display is a modified BIStm program designed for MDI training purposes. The following is a graphic display of correct MDI technique.
Note the display now shifts to the bottom of the screen, which by definition is the lung volume starting point just established. Note also the steady flow inspiration line, all the way to full lung volume. This is followed by a breath holding period, and then controlled exhalation. Also note a short vertical line has been superimposed on the breathing signals, right at the beginning of inspiration, therefore indicating correct timing of the activation of the MDI device. The patient's real time performance is matched in real time to the programmed analogs, to identify errors and to provide a means for visual biofeedback correction of deficient performance.
The following is an example of incorrect MDI use.
Note the Inspiratory flow is too rapid, full lung inflation has not been achieved, the Breath Holding time is too short, and the MDI has been activated too late.
The following is another example of incorrect MDI use.
Note the correct Inspiratory flow and desired full lung inflation have been achieved. However, Breath Holding time is still too short, and that the MDI has been activated late, and twice.
In most instances, these visual displays are all that is needed for quality control. However, for more definitive control the Phantom Line error definition technique may be employed. This will not be described here. Please refer to the section on Biofeedback Incentive System for a description of Phantom Lines.
For the monitoring of long-term results and ongoing training in MDI use, the patient may have several follow-up sessions. Once the setup parameters have been established, it takes only a moment to input the patient's individual program. Hard copy of patient performance may be kept to evaluate training progress. The patient's prompting screen may optionally be blanked, to see if they are able to perform correctly without the visual prompting. The patient may be re-evaluated during an episode of decompensation (e.g. an acute Asthma attack) to see whether or not they maintain their MDI skills under duress.
In this manner an individual patient's MDI technique needs may be precisely defined, modified if need be, monitored to see whether or not they have learned the technique, and to objectively evaluate whether or not this learning has been retained.
The Sierra Biotechnology MDI Training device gives the Physician and Respiratory Therapy staff complete control of MDI technique definition, specifically tailored to individual patient needs. And the visual biofeedback technology provides a powerful method to teach and quality control this technique. As such, this is a major advance solving a difficult and important area of medication delivery to the Asthmatic and COPD patient population.