Pregnancy and Positional Therapy

A significant proportion of non-pregnant people with sleep-disordered breathing (SDB) are classified as position-dependent, which means that they experience most of their breathing abnormalities while lying supine. Positional therapy (PT) is a simple, non-invasive, inexpensive, long-established, safe, and effective intervention for preventing people with positional-dependent SDB from sleeping on their back and thereby prevents exacerbation of their condition, improves it or totally eliminates it [1-6]. PT helps a person avoid an undesired sleeping position through the use of physical barriers (e.g., pillows, wedges) to prevent achieving the position or by use of pressure points (e.g., tennis ball technique) or alarms (e.g., vibration, sound) when in the position in order to precipitate a change to a more desired position.

There are several commercially available PT products for people with positional-dependent SDB. Despite their effectiveness, these devices universally focus on the position of the thorax, neck, and head, which make them of doubtful utility for pregnant women when it is important that the maternal pelvis is not supine. In large studies of positional dependency of SDB in the general population, positional dependency has been shown to be inversely related to BMI [7,8]; therefore, in pregnancy, a state accompanied by rapid weight gain and increased airway edema [9,10], SDB, if present, may be less likely to be dependent on body position. In addition, pregnant women are also significantly different from the general population in various aspects such as anatomy (e.g., gravid uterus, widened subcostal angle, increased thoracic diameter, elevated diaphragm, decreased chest wall compliance), physiology (e.g., increased metabolism, increased oxygen consumption, increased carbon dioxide production) and nocturnal behaviour (e.g., rising up more often during the night to void due to compression of the bladder from the gravid uterus). An issue particularly specific to pregnancy is that of the impact of the position of the maternal pelvis on maternal, placental, and fetal hemodynamics. No clinically tested PT devices to date, besides the PrenaBelt™, have taken this important factor into account.

Efforts to achieve safe sleeping positions in pregnancy via PT ought to be balanced against possible detrimental effects on the quality and quantity of sleep. A recent systematic review and meta-analysis demonstrated the clinical utility of newer generation PT devices that attach to the neck or chest and provide a subtle vibratory stimulus when the user is in the supine position [11]. Although this review included two studies that indicated objective sleep quality parameters improved with such sleep position trainers [12,13], these studies have a small sample size, and the external validity of the meta-analysis is limited to persons with mild to moderate position-dependent obstructive sleep apnea (OSA) (the mean (standard deviation) apnea-hypopnea index was 21.8 (7.2) events per hour). Treatment with newer generation PT devices resulted in these individuals experiencing, on average, a reduction in their AHI by 11.3 events per hour; therefore, because OSA is known to disrupt sleep architecture, it is intuitive that these individuals would experience improved sleep quality (despite their sleep being intermittently interrupted by a supine alarm) as a result of a reduced AHI and, thus, OSA severity.

However, when the primary indication for PT is not to treat positional OSA, there is a paucity of data regarding the safety and efficacy of passive methods of PT in comparison to active methods (e.g., vibratory alarms). For example, if the primary indication of PT is to optimize maternal-fetal hemodynamics via the pelvis position, in the absence of positional OSA and its impact on sleep architecture, it becomes obvious that active methods of PT are more likely to disrupt sleep architecture and result in reduced sleep quality. Moreover, the authors of the meta-analysis emphasize the need for larger randomized control trials and recommend future research focus on how PT devices affect quality-of-sleep metrics including sleep fragmentation, sleep continuity, sleep stage changes as well as their effect on daytime sleepiness [11].

Further, vibrational stimuli have been previously demonstrated to have a deleterious effect on sleep quality in individuals without SDB [14,15]. The impact of PT on sleep quality and quantity is of critical importance as poor sleep quality and quantity in pregnancy have been directly linked to adverse outcomes such as postpartum depression [16–18]. Although there are some PT devices that help pregnant women sleep on their side, these devices are characteristically limited in that they inherently ignore the position of the pelvis, are not clinically tested or validated, and/or are prohibitively expensive.

The simplest method of PT is to simply instruct pregnant women to avoid sleeping supine, and anecdotally, when so instructed, most pregnant women respond that they do not sleep supine. However, we have published data indicating that pregnant women do spend a significant proportion of the night sleeping supine [19], they also underestimate this proportion [20], and when asked to maintain a lateral sleeping position, they can do so moderately well but at the cost of reduced sleep quality [21].

Drawing on the concept of PT for SDB, our team designed a PT device for pregnant women called the PrenaBelt™ (patent pending). The PrenaBelt™ is a belt-like device worn at the level of the pregnant woman’s pelvis. While the PrenaBelt™ does not prevent the user from lying supine during sleep, it significantly decreases the amount of time she spends in this position via the mechanism of PT [20,22].

A feasibility study done on the PrenaBelt™ to determine if it would reduce supine sleep time in the home setting in the third trimester showed that supine sleeping time can be reduced with the use of PrenaBelt™ without affecting sleep quality and duration and with added benefits in nocturnal maternal respiration and fetal heart rate pattern [22]. Another study that investigated the use of the PrenaBelt™ by pregnant Ghanian women in their third trimester in a home setting showed that the use of the PrenaBelt™ resulted in increased birth weight and GROW centile by 100g and 7% respectively, despite a 56% adherence. For every 1% increase in adherence to using either the PrenaBelt™ or sham-PrenaBelt™, the GROW centile increased by 0.5% and this was statistically significant [23].

Sources

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