Emfit Corp. (USA)



Sleep apnea scoring

Breathing disturbance data registered

The sensor signal from EMFIT QS can be used for detecting different kinds of breathing disturbances. The following examples present how you can use EMFIT QS data for screening breathing disorders. First, you will see examples of the normal breathing of a healthy person. examples of breathing disturbance situations during sleep.

In the first chapter, there is an example of the normal breathing of a healthy person. In each example, there are two curves that are measured with the EMFIT QS sleep sensor. Each curve represents registered data with different filtering of the raw BCG signal. Respiration flow and oxygen saturation cannot be measured with the sensor.

In the following chapters, you can see sleep registering in different situations. In figure 1, normal breathing is represented and in the figures following that, there are descriptions of the sleep-related breathing disorders.

"When compared to visual scoring, the EMFIT mattress had sensitivity of 100% and specificity of 82%" *

* Excerpt from:  “Screening sleep-related breathing disturbances in stroke patients using the Emfit ferroelectret film sensor and the oximeter”, T.S. Niiniviita*1, M. Takala*1,2, E. Rauhala*2 and A. Holm*1,2 

1 University of Turku, University of Turku Graduate School, Turku, Finland 

2 Satakunta Central Hospital, Department of Clinical Neurophysiology, Pori, Finland


Sleep apnea scoring

Figure 1: The amplitude of the normal breathing with a healthy person stays quite constant during the whole sleep period. Breathing is regular and BCG is quite stable. Some irregular spiking is normal. This can be observed from the both signals derived from the bed sensor.

Sleep apnea scoring

Figure 2: Curve of respiration effort of normal breathing

Figure 2: Curve of respiration effort of normal breathing

Figure 3: Same as figures 1 and 2; all graphs enabled visible.

Sleep apnea scoring

Figure 4: Periodic obstructive breathing (POB) consists of hypopnea and apnea periods. When the airways open after apnea, there are spiking and the amplitude of the curve changes periodically.

Sleep apnea scoring

Figure 5: Curve of respiratory effort during periodic obstructive breathing.

Sleep apnea scoring

Figure 6: Same as figures 4 and 5; all graphs enabled visible.

The upper airways of the patient are obstruced caused by the increased level of thoracic cavity. Breating is laboured and the intrathoracic negative pressure is greater than -8 CmH2O. This causes spiking in he curve in relation to the base line.

Sleep apnea scoring

Figure 7: Respitatory effort starts to intensify which leads to increase in the respitatory amplitude.

Sleep apnea scoring

Figure 8: Respitatory effort starts to intensify which leads to spiking phenomen.

Sleep apnea scoring

Figure 9: Same as figures 7 and 8; all graphs enabled visible.

Sleep apnea scoring

Figure 10: In the left side of the curve, you can see an apnea period when the breathing stops completely. You can also see that there are no attempts to breathe neither. These are features of central sleep apnea.

Screening and Scoring Breathing Disorders

EMFIT QS can be used as an aid for screening breathing related disorders. Measured night can be scored into four different breathing categories.

Breathing is scored into:

  • NB -Normal Breathing
  • POB -Periodic Obstructive Breathing (apnea/hypopnea events)
  • PPO –Prolonged Partial Obstruction
  • CA -Central Apnea

Scoring can be made visually from the signal view, where there are breathing, PPO/respiratory effort, raw signal (which shows cross body movements) as separate channels. Scoring is made by the breathing categories, which dominates the 3 minutes period (1/3 is used) Central apneas can be marked in the view too, so they can be calculated as a count during TST.

If over 20% of breathing is periodic obstructive breathing (POB) of total sleep time, then it is beneficial to start CPAP treatment (AHI >15, apnea/hypopnea index). This has been shown in the (Tenhunen et al.2013)

Adjusted AHI:

Sometimes calculating AHI may lead in underestimating the obstructive breathing. Usually the duration of apnea period is not calculated, so if the apnea periods are long, the duration of those are not shown in the incereased value of apnea/hypopnea index (AHI).

Calculating the AHI by taking into account the duration of the apnea periods, will lead to more accurate detection of apnea and hypopnea events. (Muraja-Murro et al. 2014)

EMFIT QS provides an easy, non-invasive way for screening the sleep. By screening the breathing with EMFIT QS, medical doctor can refer the patient into further research if needed (Tenhunen 2015). Also CPAP-treatment can be started if the symptoms affect negatively to the daily life (In Finland: Käypä hoito)