Clinically validated ballistocardiograph for remote scoring of obstructive and central sleep apnea.
Emfit’s QS+CLINICAL™ hardware variant is a registered medical device in EU for the purpose of without a patient contact to transform the body, breathing and heart contractions movement into an electric signal.
QS+CLINICAL can record, transfer and store the signal data for the purpose of investigating physiological processes at rest. The collected signal data are intended for healthcare professionals to decide if further tests are needed to diagnose obstructive or central sleep apnea.
Emfit's sensors have been widely used in scientific research of ballistocardiography since early 1990's. Today there are close to 100 scientific publications in total. QS+CLINICAL makes it possible to conduct investigation easily and conveniently for patients, and collect data remotely over the Internet.
The information registered with QS+CLINICAL™
Emfit's QS+CLINICAL™ sensor signal can be used for detecting different kinds of breathing disturbances. In the follows are examples of the normal breathing of a healthy person and examples presenting breathing disturbances 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 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 bed sensor.
In the following figures, there is 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.
1) Normal Breathing (NB)
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.
Figure 2: Curve of respiration effort of normal breathing
Figure 3: Same as figures 1 and 2; all graphs enabled visible.
2) Periodic Obstructive Breathing (POB)
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.
Figure 5: Curve of respiratory effort during periodic obstructive breathing.
Figure 6: Same as figures 4 and 5; all graphs enabled visible.
3) Prolonged Partial Obstruction or Increased Respitatory Resistance (PPO/IRR)
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.
Figure 7: Respitatory effort starts to intensify which leads to increase in the respitatory amplitude.
Figure 8: Respitatory effort starts to intensify which leads to spiking phenomen.
Figure 9: Same as figures 7 and 8; all graphs enabled visible.
4) Central Apnea
Figure 10: In the left side of the curve, one can see an apnea period when the breathing stops completely. One can also see that there are no attemps to breathe neither. These are features of central sleep apnea.
Scoring of Breathing Disorders with EMFIT QS+CLINICAL™
EMFIT QS+Clinical 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)
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)