FinePointe - Apnea Analysis
Apnea analysis and breath scoring is an analysis module added to the WBP sites of FinePointe™ software starting with version 2.4. The goal of this type of analysis is to score each breath and categorize it as:
- Apnea (3 different types)
- Sigh
- Sniff
- Erratic
- Normal
The information in this article is found in the WBP User Manual. Please see the user manual for additional information.
IMPORTANT!!
Synchronized bias flow pumps are required for Apnea analysis. All breaths are categorized, meaning no breaths are rejected. Previous bias flow design could introduce artifact that may be misinterpreted by the software and reported inaccurate scoring. Therefore, the need to isolate the hardware is essential and the updated synchronized bias flow pump design is required.
The Synchronized bias flow pump design was introduced with the 4-site WBP Controller Rev11 and the 2-Site WBP Controller Rev06. Previous revision may be updated with this new design to permit Apnea analysis.
Unlike traditional WBP analysis where the analyzer focuses on what a representative breath is and ignores unusual or outlier breaths and noise, apnea analysis starts out with the assumption that every pattern seen is a breath. The first stage of apnea analysis is to delineate each breath with a start marker. Once this is achieved, the breath is compared with breaths that preceded it to determine if it is especially deep, long, shallow, quick etc.
The first stage of apnea analysis which delineates each breath is species dependent and relies heavily on a filter designed to adequately exclude noise and baseline shifts. And since the baseline of the box flow in a Whole Body chamber shifts routinely due to minute volume changes, the baseline filtering properties are critical.
An apnea is defined as an unusually long breath, from start of inspiration to the end expiration. FinePointe™ allows you to specify values to suite your definition. An apnea can be defined as a breath which is a minimum fixed duration, or a certain percentage greater than the breaths before, or a combination of those two criteria.
There are three types of apneas which categorize apnea with respect to a sigh: Type 0, Type 1, and Type 2.
Apnea Type | Definition |
Type 0 | An apnea with no sigh before it |
Type 1 | An apnea which is also a sigh |
Type 2 | An apnea with a sigh before it |
A sniff is defined as a shallow breath (a volume less than a certain amount) which is also very short in duration.
A sigh is defined as an especially deep breath, either relative compared to the breaths that precede it, or a breath which exceeds a specified volume.
A normal breath is none of those breaths, but also has a single defined inspiratory volume and expiratory volume.
An erratic breath is anything else.
The form shown here allows you to configuration your breath scoring.
The Scoring Interval specifies how often the apnea analyzer reports data.
The Breathing Baseline Interval is the period of time before each breath that the analyzer examines for normal breaths. The normal breaths found in this interval before a given breath is categorized are used to determine the
normal characteristics. For example, the average volume of all normal breaths in this period is used to determine how much volume is in the smallest sigh. Further, the average normal breath duration is used to determine the minimum breath duration of an apnea.
The Apnea Definition section allows you to specify how an apnea is determined. There are 3 basic algorithms to determine if a breath is an apnea:
Algorithm | Description |
Absolute Breath Duration Threshold | A breath that is longer than a specified duration |
Normalized Breath Duration Threshold | A breath that is a certain percentage longer than the breaths that preceded it. |
Combined Thresholds | A breath that is either longer than a specified duration or is a certain percentage longer than the breaths that preceded it. |
Important
Keep in mind that the normalized definition of apnea alone will sometimes produce unexpected results since apneas sometime occur during a period of slow breathing. In this case, breaths that you expect to be marked as apnea may not be.
The Sigh Definition section allows you to specify how a sigh is determined. There are 2 basic algorithms to determine if a breath is a sigh:
Algorithm | Description |
Absolute TV Threshold | The tidal volume of a breath exceeds a specified volume. |
Normalized TV Threshold | The tidal volume of a breath exceeds a certain percentage greater than the breaths before it. |
Depending on which algorithm you select, the edit box below the algorithm selection will change so that you can specify the additional argument. If you select Absolute TV Threshold, then you can set the minimum TV which constitutes a sigh.
The Sniff Definition section allows you to specify how a sniff is determined. A sniff is both a minimum rate and a maximum volume. Minimum Sniff Rate defines the minimum rate. Maximum Sniff Volume defines the maximum volume allowed for a sniff. Keep in mind that the maximum sniff volume is not the animal’s volume, but the volume derived by integrating the Box Flow. This volume is typically 1/10 of the volume of the animal.
The Base Breathing Profile specifies the filter needed for the first phase of analysis. There is only one setting here, but should you be working with an unusual species or a new species or rodent, we can provide other profiles which will be designed for their breathing patterns.
Reviewing Apnea Data
It is a good idea to review the apnea data when you are new to it. And when you do review it, the most important thing to check is that the analyzer is delineating the breaths properly. The first stage of the analysis starts by applying a special filter to the data in order to exclude noise and wandering baselines on the box flow. It produces the Conditioned Box Flow signal which is the Box Flow with the filter applied.
Next enable the plotting of breath delineation tick by pulling down the Ticks button and checking the Start Mark under Apnea.
The start mark will place a white score at the start of each breath on the Conditioned Box Flow trace.
Under Charts->Signals, select to show only the Box Flow and the Conditioned Box Flow. By hiding the other traces, display space is not wasted on traces we may not be concerned with.
Example review of apnea data showing the Start Mark on the Conditioned Box Flow.
Looking at the Conditioned Box Flow, the white strokes indicate the placement of the Start Marks. This is where the analyzer determined the start of each breath. If these start marks are placed properly without missing any breaths, you should be extremely confident that the determinations of the categorization will be applied correctly.
Scroll through the data and spot check it to ensure these are applied properly. You can reject regions which are not properly applied.
Once you are satisfied with the placement of the Start Mark, you can then return to the Ticks menu and enable additional ticks to see which breaths the analyzer scored as some of the other categories.
Examples
Type 0
Type 1 with Sigh
Type 2 with Sigh
Sniffing
Comments
0 comments
Please sign in to leave a comment.