**1.2 F-SAS sensor system**

**Figure 3** shows plastic optical fiber sheets and physics of measurement. Fibers interspaces are narrower one and wider one within several centimeters. Commercially available SI plastic optical fibers (CK10) were used. Physical principle is to measure the deviation of output optical power from fiber sheet by micro-bending loss and/or bending loss. **Figure 4** is the experimental response for intentional apnea. One pulse wave form means one breath in and out. Flat parts indicate the apnea after breath in or out. Narrower fiber interspaces POF sheet is more sensitive than the wider one. As shown in **Figure 5**, a plastic optical fiber (POF) sensor sheet is simply placed under the bottom bed sheet. There is no need for the subject to wear any special clothing or devices. The measurement data is transmitted to a remote location for analysis and diagnosis. The measurement principle is illustrated in **Figure 3**. The deviation in the output optical power from the POF sheet due to micro-bending loss and/or bending loss caused by the lateral pressure change created by the motion of the person's chest during respiration is measured.

**Figure 3.** *Measurement principle.*

It is both quiet and compact and thus potentially useful for screening potential SAS

This paper describes the F-SAS sensor and the measurement principle. It then describes its application in a hospital setting and in hotels [5, 6]. Under the assistance of the "Beautiful Fukushima Next-Generation Medical Industry Agglomeration Project," in Japan, we have succeeded in downsizing the F-SAS sensor and have

recognized that it highly correlates with polysomnography (PSG) and pulse

sufferers during normal sleep at home.

*Probability of traffic accident for various AHI levels of Japanese adults.*

*Sino-Nasal and Olfactory System Disorders*

**Figure 1.**

**Figure 2.**

**136**

*Subjects ready for PSG test.*

*N*: Average number of bends par meter, ð Þ 1*=R*<sup>1</sup>

*Optical Fiber-Based Sleep Apnea Syndrome Sensor DOI: http://dx.doi.org/10.5772/intechopen.91060*

tory disturbance index (RDI).

**Figure 6.**

**139**

*Sensor system components and configuration.*

2

: Correlation length, *d*: core diameter, Δ: Relative refractive index difference. Example measurement results for intentional apnea are shown in **Figure 4**. One pulse wave-form corresponds to one breath in and out. The flat parts indicate apnea after breathing in or out. Results are shown for a POF sheet with narrow fiber spacing and for one with wider spacing. The one with narrower spacing was more sensitive. As shown in **Figure 6**, the sensor system comprises a SI-POF (240/250 micron, NA = 0.5) sheet, an optical power meter (9 V DC) with a Si photodiode, an LED (650 nm) built-in controller, a microcomputer (5 V DC), a memory card, and a small liquid crystal display panel. Input power is 12 V DC from AC commercial power. Commercially available Si plastic fibers (ESCA CK10, Mitsubishi Rayon Co., Ltd.) are used. The sheet is packed between the bottom sheet and the bed. The user initiates operation by simply pushing the SW button and then sleeps on the bed as usual without wearing any electrodes. While sleeping, the user can freely roll over, change body position, and go to the toilet. The user ends operation upon awaking by again pushing the SW button. The measurement data are automatically stored on the memory card (SD card), which is attached to the side of the controller. The data for more than 200 nights can be stored; the data for each night is stored in a separate file with an automatically generated sequential file name. As necessary, the data can be analyzed at remote site or on site by inserting the SD card into a PC running a specially developed data analysis program. For one night's data file, it takes about 1 second to plot the signals for normal respiration, apnea, hypopnea, body motion, rolling over, and sleeping body position, and to generate the respira-

A clinical application of this F-SAS sensor system was conducted at JR Sendai Hospital and in Tsukuba University Hospital in Japan using 20 subjects with ages from 13 to 78 and with BMIs of from 19.2 to 39.3. The POF sheet and PSG were used concurrently. The F-SAS sensor data were automatically analyzed by using the specially developed data analysis program to plot the signals for normal respiration,

: Mean square of fiber curvature,

#### **Figure 4.**

*Example measurement results for intentional apnea.*

**Figure 5.** *Overview of F-SAS sensor system.*

The theoretical formula for irregular bending loss of multimode optical fibers was given by Furuya and Suematsu [12]. As shown by Eq. (1), R1 decreases/ increases depending on the stress increase/decrease with expansion/contraction of the chest by respiration. Therefore, the stress increases/decreases, and transmission loss Lm increases/decreases.

$$L\_m = 2500 \text{ N} \overline{\left(1/R\_1\right)^2 W^2}^2 \frac{1}{\Delta} \exp\left[-\left(\frac{\overline{W}}{d}\right)^2 \Delta\right] \text{(dB } / km\text{)}\tag{1}$$

*N*: Average number of bends par meter, ð Þ 1*=R*<sup>1</sup> 2 : Mean square of fiber curvature, : Correlation length, *d*: core diameter, Δ: Relative refractive index difference.

Example measurement results for intentional apnea are shown in **Figure 4**. One pulse wave-form corresponds to one breath in and out. The flat parts indicate apnea after breathing in or out. Results are shown for a POF sheet with narrow fiber spacing and for one with wider spacing. The one with narrower spacing was more sensitive. As shown in **Figure 6**, the sensor system comprises a SI-POF (240/250 micron, NA = 0.5) sheet, an optical power meter (9 V DC) with a Si photodiode, an LED (650 nm) built-in controller, a microcomputer (5 V DC), a memory card, and a small liquid crystal display panel. Input power is 12 V DC from AC commercial power.

Commercially available Si plastic fibers (ESCA CK10, Mitsubishi Rayon Co., Ltd.) are used. The sheet is packed between the bottom sheet and the bed. The user initiates operation by simply pushing the SW button and then sleeps on the bed as usual without wearing any electrodes. While sleeping, the user can freely roll over, change body position, and go to the toilet. The user ends operation upon awaking by again pushing the SW button. The measurement data are automatically stored on the memory card (SD card), which is attached to the side of the controller. The data for more than 200 nights can be stored; the data for each night is stored in a separate file with an automatically generated sequential file name. As necessary, the data can be analyzed at remote site or on site by inserting the SD card into a PC running a specially developed data analysis program. For one night's data file, it takes about 1 second to plot the signals for normal respiration, apnea, hypopnea, body motion, rolling over, and sleeping body position, and to generate the respiratory disturbance index (RDI).

A clinical application of this F-SAS sensor system was conducted at JR Sendai Hospital and in Tsukuba University Hospital in Japan using 20 subjects with ages from 13 to 78 and with BMIs of from 19.2 to 39.3. The POF sheet and PSG were used concurrently. The F-SAS sensor data were automatically analyzed by using the specially developed data analysis program to plot the signals for normal respiration,

**Figure 6.**

*Sensor system components and configuration.*

The theoretical formula for irregular bending loss of multimode optical fibers

ð1Þ

was given by Furuya and Suematsu [12]. As shown by Eq. (1), R1 decreases/ increases depending on the stress increase/decrease with expansion/contraction of the chest by respiration. Therefore, the stress increases/decreases, and transmission

loss Lm increases/decreases.

*Overview of F-SAS sensor system.*

**Figure 4.**

**Figure 5.**

**138**

*Example measurement results for intentional apnea.*

*Sino-Nasal and Olfactory System Disorders*

apnea, hypopnea, body motion and rolling over independently from the PSG analysis. The example respiration waveforms for the F-SAS sensor and PSG are shown in **Figure 7** exhibits good consistency. The correlation coefficient between the AHI from the PSG and the RDI from the F-SAS was 0.71 in the region of AHI from 0 to 85.9 as shown in **Figure 8**. For AHI values from 0 to 20, the correlation coefficient was much better 0.89. In contrast, it was 0.57 for AHI values from 20 to 85.9. This means that the F-SAS sensor is more accurate and sensitive for milder degrees of SAS. The RDI from the F-SAS sensor was smaller than the AHI from the PSG for moderate and severe degrees of SAS because of the bigger difference between the sleeping time and the time in bed. This means that the F-SAS sensor is better suited for screening than for diagnosis. In fact, in a separate study of at-home use, potential SAS sufferers from among 19 ordinary people were identified by using this

F-SAS sensor system. Definitive diagnoses made in the JR Sendai Hospital for the four potential sufferers were that three had mild cases and one had

The apnea and hypopnea distributions from the PSG and the F-SAS sensor for one night for a severe SAS sufferer (**Figure 9**) show good accordance. **Table 1** shows the reliability of the F-SAS sensor in comparison with PSG under the American Academy of Sleep Medicine (AASM) criteria published in 2001 [13]. It had

A multi-channel F-SAS sensor system has been developed and done field test in a

hotel, full medical check-up and clinical test in pediatrics. **Figure 10** shows the

*Apnea and hypopnea distributions from PSG and F-SAS sensor for one night for severe SAS sufferer.*

*Reliability of F-SAS sensor in comparison with PSG under AASM criteria published in 2001 [13].*

a moderate case.

**Figure 9.**

**Table 1.**

**141**

good sensitivity of 0.909.

**1.3 Application to other areas**

*Optical Fiber-Based Sleep Apnea Syndrome Sensor DOI: http://dx.doi.org/10.5772/intechopen.91060*

**Figure 7.** *Example respiration waveforms for F-SAS sensor and PSG [3] from 0 to 85.9 (R = 0.71).*

**Figure 8.** *Correlation between AHI by PSG and RDI from F-SAS for AHI values.*

*Optical Fiber-Based Sleep Apnea Syndrome Sensor DOI: http://dx.doi.org/10.5772/intechopen.91060*

F-SAS sensor system. Definitive diagnoses made in the JR Sendai Hospital for the four potential sufferers were that three had mild cases and one had a moderate case.

The apnea and hypopnea distributions from the PSG and the F-SAS sensor for one night for a severe SAS sufferer (**Figure 9**) show good accordance. **Table 1** shows the reliability of the F-SAS sensor in comparison with PSG under the American Academy of Sleep Medicine (AASM) criteria published in 2001 [13]. It had good sensitivity of 0.909.
