Feasibility and user acceptability of Breezing^™, a mobile indirect calorimetry device, in pregnant women with overweight or obesity

Abstract

Emerging evidence has suggested that prenatal resting energy expenditure (REE) may be an important determinant of gestational weight gain. Advancements in technology such as the real-time, mobile indirect calorimetry device (Breezing^™) have offered the novel opportunity to continuously assess prenatal REE while also potentially capturing fluctuations in REE. The purpose of this study was to examine feasibility and user acceptability of Breezing^™ to assess weekly REE from 8–36 weeks gestation in pregnant women with overweight or obesity participating in the Healthy Mom Zone intervention study. Participants (N=27) completed REE assessments once per week from 8–36 gestation using Breezing^™. Feasibility of the device was calculated as compliance (# of weeks used/total # of weeks). User acceptability was measured by asking women to report on the device’s enjoyability and barriers. Median compliance was 68%. However, when weeks women experienced technical difficulties (11 of 702 total events) and the device was unavailable were removed (13 of 702 total events), median compliance increased to 71%. Over half (56%) of the women reported that the device was enjoyable or they had neutral feelings about it whereas the remaining 44% reported that it was not enjoyable. The most common barrier reported (44%) was the experience of technical issues. Study compliance data suggest the feasibility of using Breezing^™ to assess prenatal REE is promising. However, acceptability data suggest future interventionists should develop transparent and informative protocols to address any barriers prior to implementing the device to increase use.

1. Introduction

Despite public health efforts to mitigate the effects of the obesity epidemic, over 60% of childbearing women in the United States enter pregnancy with overweight (body mass index [BMI] = 25–29.9 kg/m²) or obesity (BMI ≥ 30 kg/m²) (C. Chen et al., 2018). Pregnant women with overweight or obesity are at an elevated risk for developing gestational diabetes, hypertensive conditions, and preterm birth (Yang et al., 2019). Moreover, these risks are often exacerbated by excessive gestational weight gain (GWG). Excessive GWG is defined as >11.3kg for women with overweight and >9.1kg for women with obesity and is an independent predictor of adverse maternal (e.g., hypertension, preeclampsia, postpartum weight retention, gestational diabetes) and infant (e.g., high birth weight, macrosomia, mortality) outcomes (Bianchi et al., 2018; H. Y. Chen & Chauhan, 2019; Haugen et al., 2014; Rasmussen & Yaktine, 2009; Ren et al., 2018), as well as long-term overweight and obesity (Mamun et al., 2010). Despite these risks, over 60% of pregnant women with overweight or obesity have excessive GWG (Kominiarek & Peaceman, 2017). Emerging evidence suggests that resting energy expenditure (REE) is an important determinant of GWG (Berggren et al., 2017; Leonard et al., 2021; Vander Wyst et al., 2020). There is also evidence suggesting that there is a need to revise prenatal energy intake recommendations and that REE can be used to develop individualized energy intake goals to better regulate GWG (Savard et al., 2021). This has highlighted the need to better understand REE over the course of pregnancy.

While most studies have shown that REE increases throughout pregnancy (Berggren et al., 2017; Leonard et al., 2021; Vander Wyst et al., 2020), the amount and pattern of increase is highly variable with some pregnant women with overweight or obesity adopting non-linear trajectories (Leonard et al., 2021), which is in contrast to what has been traditionally assumed (i.e., linear increase from pre- to post-pregnancy). The variability and fluctuations in REE may more accurately predict GWG rather than absolute levels and/or changes in REE (Leonard et al., 2021; Vander Wyst et al., 2020). To test this hypothesis, more frequent assessments of prenatal REE, particularly in pregnant women with overweight or obesity who are at elevated risk for excessive GWG, is warranted.

The widespread use of mobile health (mHealth) technologies (e.g., smartphones) among perinatal women (Urrutia et al., 2015) and advancements in technology have allowed for the development of a commercially available, novel mobile metabolism device, Breezing^™. An advantage of the Breezing^™ device is that it allows for collection of real-time and continuous measures of REE using indirect calorimetry, as opposed to the current gold standard of REE assessment, the Douglas Bag method (indirect calorimetry). Although valid, the Douglas Bag method is a laboratory-based assessment that is not feasible for obtaining frequent (e.g., weekly) assessments of REE during pregnancy. Breezing^™ is an established and valid assessment of REE and is strongly correlated with the gold standard of REE assessment (Deng & Scott, 2019; S Jimena et al., 2020; Xian et al., 2015). However, little is known regarding whether pregnant women with overweight or obesity will actually use the device to measure REE throughout pregnancy and if they will like using the device or experience particular barriers. Answering questions of feasibility (e.g., “are measurement procedures feasible) is important as it can provide insight on future intervention development and implementation (Gadke et al., 2021). The purpose of this study was to examine the feasibility and user acceptability of Breezing^™ to assess REE in pregnant women with overweight or obesity throughout pregnancy. We hypothesized that Breezing^™ would be both feasible and acceptable for assessing prenatal REE. Study findings may also provide a unique contribution to understanding energy balance and GWG, which can inform future intervention strategies and clinical guidance for regulating GWG.

2. Methods

The Healthy Mom Zone study was approved by the Pennsylvania State University Institutional Review Board. The Healthy Mom Zone study was a randomized controlled trial testing the feasibility of an adaptive, theoretically-based behavioral intervention to regulate GWG in pregnant women with overweight or obesity. The Healthy Mom Zone study was based on a conceptual framework that expanded on a dynamical mathematical energy balance model that predicted GWG, to include principles from the Theory of Planned Behavior (Ajzen, 1991) and Self-Regulation (Carver & Scheier, 1998). Women were eligible to participate if they were 18–40 years old and had: 1) overweight/obesity (BMI range 25–45 kg/m²; >40 kg/m² with physician consultation), 2) singleton pregnancy ≥8 weeks gestation, 3) physician consent to participate, and 4) were English-speaking, residing in or near central Pennsylvania. Exclusion criteria were: 1) multiple gestation, 2) diabetes at study entry, 3) not having overweight/obesity, 4) severe allergies or dietary restrictions, 5) contraindications to prenatal PA (H et al., 2021), 6) not English-speaking and, 7) not residing in area for duration of study. Women were recruited using on-site clinic, community-based, and web-based strategies. Women randomized to the intervention group attended weekly face-to-face sessions with a registered dietician who delivered evidence-based education/counseling. Each woman’s GWG was monitored weekly, and then summarized every four weeks. During the fourth week, if women were within the GWG IOM recommendations, they continued with education. If women were gaining above the GWG IOM recommendations, the intervention adapted and women received a more intensive intervention (e.g., additional physical activity sessions). Women randomized to the control group received usual prenatal care (i.e., prenatal education and regular appointments with healthcare provider). In order to inform the energy balance model of the Healthy Mom Zone study, all women used mHealth tools to obtain measures of weight, physical activity, resting energy expenditure, and energy intake. For the purpose of this current study, we focus on the assessment of resting energy expenditure. The primary findings of the Healthy Mom Zone showed that the intervention group had a non-significant 21% lower GWG compared to controls (Symons Downs et al., 2021). A more detailed explanation of the protocol and primary findings of the Healthy Mom Zone study has been published and can be found elsewhere (Symons Downs et al., 2018, 2021). Women completed a 30-minute baseline session (~8 weeks gestation) at the Pennsylvania State University’s Clinical Research Center in which study procedures were explained and informed consent obtained.

2.1. Participants

Pregnant women with overweight or obesity (N = 31) participated in the Healthy Mom Zone Study, a theoretically-based behavioral intervention that adapted the intervention dosage and intensity over time in pregnant women with overweight or obesity from ~8 to 36 weeks gestation to regulate GWG (Symons Downs et al., 2018). Inclusion criteria were: pregnant women with a singleton pregnancy >8 weeks gestation, BMI ≥ 25 kg/m²; English-speaking; residing in or near Centre County, Pennsylvania; and with physician consent to participate. A total of N = 31 women completed baseline sessions and were trained to use the Breezing^™ device. Of these women, 1 dropped out and 3 had early miscarriages. Thus, a total of N = 27 women were included in the feasibility and user acceptability analyses.

2.2. Breezing^™

The Breezing^™ device is an indirect calorimetry analyzer of REE and is compatible with both iOS and Android software platforms. During a baseline session (~8-weeks gestation), women were instructed to download the Breezing^™ application (Version 3.2) onto their smartphones. The women were asked to create an account in which they filled out information on their name, gender, age, height, weight, and activity level (e.g., sedentary, lightly active, etc.). The application included the following tabs: metabolism, history, goals, and settings. For the purpose of the Healthy Mom Zone study, women were instructed to only use the “metabolism” tab to obtain a measurement. It was explained to each woman that Breezing^™ was to assess their REE which may be useful for understanding their total energy expenditure, and thus may help with regulating their GWG. Women were trained on how to use the Breezing^™ device and sent home with detailed instructions for how to use the device. They were also instructed to contact the research investigators if they experienced any difficulty using the device. Women were instructed to use Breezing^™ one time per week (on the same day of the week) at the same time each morning from 8–36 weeks gestation. A full Breezing^™ measurement took approximately 1–2 minutes to complete. Women were instructed to obtain their assessment after 8 hours of sleep, immediately after waking up while lying down and in a fasting state (i.e., no food for the past 8–12 hours). Once the Breezing^™ application was initiated, women were able to follow a check-list of step-by-step directions to obtain a measurement. They were first instructed to scan a QR code on the package of provided sensor cartridges. The sensor cartridges included pre-calibrated information and were used to determine the rate of oxygen consumption and carbon dioxide production. Next, with a nose clip, women were instructed to practice breathing in the provided mouthpiece without the device until breathing was consistent. Once breathing was consistent, they were prompted to insert one new sensor cartridge into the Breezing^™ device (for calibration and for determining the rate of oxygen consumption and carbon dioxide production) and preform an actual measurement. Women blew into the device through the mouthpiece until the application said the test was completed. The algorithm within the Breezing^™ device then calculates REE according to the Weir equation, a well-known equation used with indirect calorimetry (Weir, 1949):

$$[3.9*{\text{VO}}_2+1.1*{\text{VCO}}_2]*1.44$$

VO₂ represents the volume of oxygen consumed and VCO₂ represents the volume of carbon dioxide produced. All data was then transmitted via Bluetooth to the women’s’ smartphone and then sent to the research team. The device did not produce results if the woman had ‘irregular breathing’ (i.e., too slow or fast and/or irregular rate, as detected by the device). If the device registered the measurement as ‘irregular,’ women were instructed to complete another measurement until a successful assessment was obtained. At ~36 weeks gestation, women returned the device during their 30-minute post session.

2.3. User Acceptability

During post intervention sessions (~36 weeks gestation), each woman was asked to rate the item “how enjoyable did you find the Breezing^™ device” on a scale of 1 (Not at all enjoyable) to 5 (Extremely enjoyable) with 3 being neutral. Women were also asked to describe any issues or barriers to using the Breezing^™ device.

2.3. Statistical Analysis

All data was analyzed using IBM SPSS Statistics (version 26.0). Median compliance was calculated for each woman by calculating the number of weeks Breezing^™ was successfully completed out of the total number of weeks (i.e., ~27 weeks). Similar to past studies using mHealth tools and programs to measure behaviors and outcomes, an overall compliance rate of 70% or higher was considered sufficient compliance (Druce et al., 2017; Kauw et al., 2019). User acceptability was analyzed as the percentage breakdown of women’s enjoyability ratings. Answers to the open-ended question of issues experienced were descriptively examined.

3. Results

3.1. Participant Characteristics

Participant characteristics are presented in Table 1. Participants had a median age of 30.0 (interquartile range [IQR] = 4.0) years and 10.0 (IQR = 3.0) gestational weeks at study entry. Women had a median pre-pregnancy BMI of 28.7 kg/m² (IQR = 13.4; overweight = 59%, obese = 41%). The majority of women were Non-Hispanic, White (96%), married (92%), employed full-time (89%), and reported a family income ≥ $40,000 (77%). Almost half of the sample had a graduate/professional degree (48%).

Table 1.

Participant Baseline Characteristics

	Median	IQR	N (%)
Age	30.0	4.0
Gestational Week at Study Entry	10.0	3.0
Pre-pregnancy BMI	28.7	13.4
OW			16 (59)
OB			11 (41)
Race
White			26 (96)
Asian			1 (4)
Current Employment
Full-Time			24 (89)
Other			3 (11)
Highest Level of Maternal Education
High School			1 (4)
College			13 (48)
Graduate/Professional			13 (48)
Yearly Family Income
$10–20,000			1 (4)
$20–40,000			5 (19)
$40–100,000			12 (44)
>$100,000			9 (33)
Marital Status
Married			25 (92)
Single			1 (4)
Divorced			1 (4)
Parity
Nulliparous			20 (74)
Primiparous			7 (26)

IQR = Interquartile range; BMI = body mass index; OW = overweight; OB = obese.

3.2. Feasibility

Median compliance of Breezing^™ during the duration of the study was 68% (IQR = 65) with individual compliance rates ranging from 0–100% (Figure 1). Of the 27 women, 13 (48%) reached the threshold of 70% for sufficient compliance. Eight women (30%) had to repeat at least one measurement due to irregular breathing. Of these 8 women, 4 (50%) were able to obtain a successful measurement following at least one irregular measurement. Also of the 8 women, one woman (13%) only completed measures with irregular breathing, resulting in 0 successful measurements over the entire study period, and thus a compliance rate of 0%. Four women (15%) experienced technical issues with the Breezing^™ device that precluded the ability to obtain a measurement during these experiences. One woman (4%) discontinued Breezing^™ 4 weeks early following experiencing technical issues. The technical issues included the Breezing^™ device failing to pair with Bluetooth on the woman’s smartphone and the QR code not scanning. Because technical issues prevented completion and were not a result of participant user error, the weeks with issues (24 of 702 data points) were removed to recalculate compliance rates. When the weeks with technical issues were removed, median compliance increased to 71% (IQR = 70; Figure 2) with 14 women (52%) reaching the threshold of 70% for sufficient compliance.

Figure 1.

Individual and median compliance of Breezing^™ across total study duration.

Note. Dashed line = 70% compliance threshold.

Figure 2.

Individual and median compliance of Breezing^™ across total study duration on weeks with no technical issues.

Note. Dashed line = 70% compliance threshold.

3.3. User Acceptability

Of the 27 women, 25 (93%) completed some of the follow up interviews (Figure 3). Fourteen women (56%) rated the device as neutral or somewhat enjoyable whereas the remaining 11 (44%) rated the device as not enjoyable. Of the 11 women who reported the device as not enjoyable, 8 (73%) were women who experienced a technical difficulty and/or irregular breathing. Eleven women (44%) reported that the primary barrier experienced was due to the technical issues experienced (i.e., QR code, incompatibility with phone, Bluetooth connection, charging, reports would not send, reset the device). Five women (20%) reported that it was hard to breath or felt it did not accurately assess their breathing, it was inconvenient (e.g., had to use scissors to open sensor cartridge package), it did not feel natural to use, or that they forgot to complete the assessments. Six women (24%) reported no barriers. Finally, one woman (4%) reported wanting to know more about the Breezing^™ measurement and to receive more feedback on how she was doing.

Figure 3.

User acceptability of Breezing^™.

4. Discussion

This study aimed to establish feasibility and user acceptability of a mobile metabolism device, Breezing^™, in pregnant women with overweight or obesity from ~8–36 weeks gestation. Overall, compliance of weekly REE assessments via Breezing^™ met the threshold of 70% compliance. While 56% of women reported the device was enjoyable or they had neutral feelings about using it, the remaining 44% reported the device as not enjoyable. Many women (40%) reported a primary barrier to enjoyment was technical difficulties such as the device not connecting to Bluetooth after multiple attempts to connect the device for use. This study illustrates the importance of addressing these barriers in a timely manner (e.g., real-time technical support) to improve the acceptability of this device, and thus, its feasibility in future research.

The median compliance of 68–71% is considered sufficient and comparable to past studies examining the compliance rates of other mHealth tools and platforms (Darvall et al., 2020; Druce et al., 2017; Kauw et al., 2019; Larsen et al., 2020; Van Dijk et al., 2016). For example, Van Dijk et al. found a compliance rate of 65% for a pregnancy-based mHealth platform and suggested that this compliance rate was considered high (Van Dijk et al., 2016). Further, Darvall et al. found that pregnant women with obesity had a compliance rate of 61–79% of wearing a Fitbit (Darvall et al., 2020). Similarly, Larsen et al. found that pregnant women with diabetes had a compliance rate of 71% for wearing a Fitbit regularly (Larsen et al., 2020). Individual compliance for each woman in this study ranged from 0–100% indicating large variation in adherence to protocol. The results regarding user acceptability may provide insight as to why there was such a large variation in compliance. Specifically, slightly over half of the women reported feeling neutral or that they enjoyed using the device whereas slightly less than half rated that they did not enjoy using the device. While the reports of neutral feelings and enjoyment suggest some promise for the device, the lack of enjoyment may be explained by the fact that many women reported technological issues and/or were not able to obtain successful first-time measurements due to irregular breathing.

Indeed, past research has found that individuals are less likely to adopt mHealth use if they encounter technical difficulties suggesting that technical difficulties is a significant barrier to compliance of mHealth apps and tools (Davies et al., 2015). In fact, many studies in various populations suggest that issues with compliance and attrition of mHealth use may be attributed to experiences of technical difficulties and issues (Almufarij & Alharbi, 2022; Huber et al., 2019; Selter et al., 2018; Taki et al., 2017). In the current study, the most commonly reported technical issue was that the Bluetooth would not register the device and thus would not work. Additionally, the device would not read the sensor cartridge that was inserted. While the research investigators acted upon these issues and attempted to solve them in a timely manner, many of the participants became frustrated with the device and did not look forward to using it. After the investigators became aware that these types of technological issues were occurring, they provided the women with instructions on how to overcome potential barriers in order to minimize frustration. Future researchers working with Breezing^™ should consider being upfront about potential issues that may arise with Breezing^™ and provide participants with all potential solutions from the start while continuing to address any technological issues that arise in a timely manner. Also, the REE measurements were not considered successful if the woman had irregular breathing. The device would inform the woman of this in which she was then instructed to redo the measurement, which may have attributed to the level of enjoyment. Future investigators should ensure that women practice breathing in a consistent manner prior to an actual measurement and only take a measurement when consistent breathing is achieved. This could potentially limit the number of attempts of using the device before a successful measurement is obtained. Addressing these barriers of Breezing^™ associated with user acceptability may help in increasing compliance rates.

Interestingly, one woman reported that she would have enjoyed Breezing^™ more if she understood more about the Breezing^™ measurement and if she were to receive feedback on her REE. During the baseline session, each woman received an explanation of what REE is and why we were obtaining these measurements. They were also given an explanation of what REE means for their GWG regulation (e.g., REE is a component of energy expenditure and helps determine energy balance). Although women were able to see their REE value after each measurement, they were not provided feedback on how they were doing (e.g., the trajectory of their REE) or feedback on the utility of Breezing^™. The purpose of the Breezing^™ device within the Healthy Mom Zone study at the time was for measurement only and was not included as an intervention component (i.e., the purpose of including Breezing^™ was not to elicit behavior change). For example, one reason for obtaining Breezing^™ measurements within the Healthy Mom Zone was to understand variation in prenatal REE in relation to GWG regulation. That is, research has suggested that fluctuations in REE may be indicative of high or excessive GWG (Leonard et al., 2021; Vander Wyst et al., 2020). Thus, informing pregnant women with overweight or obesity that the purpose of assessing their REE is to better understand their GWG trajectory may be useful for increasing compliance/enjoyment of using the Breezing^™ device. Although this current study did not use Breezing^™ as an intervention tool, the device offers a unique opportunity for self-monitoring, particularly as it relates to energy intake and weight regulation, which may be useful for future intervention purposes. Specifically, after Breezing^™ is used to obtain a REE assessment, the smartphone application outputs an energy intake goal based on the inputted weight goal and REE assessment. This may be useful for future GWG regulation interventions such that in addition to a measurement tool, interventionists may want to include Breezing^™ as a self-monitoring tool to create individualized energy intake goals to regulate weight.

This was the first study to assess feasibility and user acceptability of using Breezing^™ weekly throughout pregnancy. Understanding these aspects of the device will be useful for future intervention development. For example, the findings from this study can help predict future barriers women may face when using the device, such as technological barriers (e.g., the device not connecting to Bluetooth), in which investigators can prepare solutions ahead of time. An additional strength of the study was the focus on pregnant women with overweight or obesity. There is a lack of standardized recommendations for energy balance (i.e., energy intake and expenditure) in pregnant women with overweight or obesity. Thus, better understanding feasible and accurate assessments of components of energy balance (e.g., REE) will be particularly useful for informing future interventions aiming to manage prenatal weight gain in pregnant women with overweight or obesity via energy balance. However, there are some limitations worth noting. One limitation includes the generalizability of the study findings. The sample was representative of pregnant women with overweight or obesity in Central Pennsylvania who were White, highly educated, and married. Future studies should replicate these study findings in more diverse samples. Replicating this study in a more diverse sample can help with understanding whether compliance of Breezing^™ may differ based on individual backgrounds, which researchers have deemed as an important need for future research (Brusniak et al., 2020). Although women were instructed on the importance of obtaining 8 hours of sleep and fasting for 8–12 hours prior to a Breezing^™ measurement, it may have been the case that women did not adhere to these instructions. Due to limited data availability, the current study was unable to analyze the data by adherence to these instructions. Future researchers should aim to incorporate methods to track adherence to these instructions in order to better monitor compliance and adjust feasibility analyses accordingly. Another limitation was the technological barriers women faced when using Breezing^™ that may have impacted the usability and enjoyment of the device. Future researchers should make sure to be upfront about potential technological issues and should aim to quickly solve them by providing users with a list of potential solutions. Finally, another limitation was the assessment of user acceptability. The current study only included one question of acceptability and not all women completed the assessment (i.e., two women did not attend their post session). Future studies should include more detailed and in-depth measures of user acceptability (e.g., open ended questions or validated user acceptability scales) in more pregnant women with overweight or obesity to better understand whether users perceive the device to be easy to use and enjoyable.

5. Conclusion

Overall, these findings suggest that Breezing^™ appears to be a promising tool for pregnant women with overweight or obesity to use throughout pregnancy. However, addressing key technological issues and barriers to using the device by developing a plan/protocol for women in advance, for example, will be key to increasing long-term feasibility and acceptability of Breezing^™ in pregnant women with overweight or obesity. In addition, given that Breezing^™ may be a useful mHealth tool for interventions managing prenatal weight gain, interventionists may want to provide women with education and/or information of the importance of obtaining REE assessments throughout pregnancy. Finally, future researchers may want to focus on identifying additional factors (e.g., sociodemographic factors, motivation, technology literacy, etc.) that may influence the compliance and acceptability of Breezing^™ in an effort to develop strategies to facilitate the adoption and enjoyment of Breezing^™ in pregnant women with overweight or obesity.