Low-cost monitors accurately measure indoor air quality for pregnant women with asthma

Key takeaways:

• The performance of the commercial PurpleAir system was comparable with the professional DustTrak system.
• Remote spirometry produced quality results, and patients said its use was acceptable.

WASHINGTON — Low-cost remote systems accurately monitored indoor air pollution and asthma health among high-risk pregnant women with asthma, according to data presented at the American Thoracic Society International Conference.

These systems have the potential to improve the surveillance of respiratory health in larger population studies, Ann Wang, MD, pulmonary and critical care medicine fellow, division of pulmonary, critical care and sleep medicine, Icahn School of Medicine, Mount Sinai, and colleagues wrote.

“We basically embarked on a pilot project to really look at how we can remotely monitor indoor air quality and also respiratory health in pregnant women with asthma living in an urban population, because we know that asthma is a really big contributor to both maternal morbidity and perinatal morbidity,” Wang told Healio.

Loss of asthma control is common during pregnancy, potentially leading to complications including gestational hypertension and gestational diabetes for the mother as well as low birth weight and other impacts on early childhood health, Wang said.

Meanwhile, the researchers continued, indoor air pollution worsens asthma health and often exceeds outdoor exposures in urban environments. Yet the influence of these indoor environmental factors on worsening asthma control during pregnancy remains understudied, the researchers said, particularly among racially and ethnically diverse populations.

The pilot study was designed to establish the feasibility of monitoring indoor particulate matter of 2.5 µm and smaller (PM_2.5) using the traditional DustTrak (TSI Incorporated) and low-touch, low-cost PurpleAir (PurpleAir Inc.) devices.

The researchers recruited an ethnically diverse urban population from the greater New York area with a high burden of asthma symptoms and multiple environmental exposures.

“Our population was specifically high risk because they had active asthma before their pregnancy,” Wang said. “They had been diagnosed with asthma, and they were actively using medications.”

The cohort included 31% who were Black, 13% who were Asian American and Native Hawaiian/Pacific Islander, and 56% who were other or who chose not to answer. Also, 69% were Hispanic, 19% were non-Hispanic and 13% preferred not to answer.

Education included 56% with some college, 19% with a bachelor’s degree, 19% with less than high school, and 6% with a high school diploma, GED or equivalent.

Further, 50% of these patients reported visiting the hospital at least once during their life for asthma and 50% did not. Additionally, 53% reported using one or more prednisone packs in the previous year and 47% did not.

During each trimester, there was a 7-day period that included an indoor PM_2.5 assessment via home visits. DustTrak and PurpleAir devices both were installed in each participant’s home. Temperature and humidity monitors were installed as well.

“The DustTrak is more of a traditionally used research tool. It’s been used in many other previous trials to collect these data, but is obviously much more expensive and cumbersome,” Wang said. “The PurpleAir is something that’s marketed directly to consumers. It’s a much less cumbersome, much smaller device.”

Participants also completed assessments of asthma signs and symptoms via an activity diary and remote spirometry conducted via video visit with a member of the research team.

“All of the participants were given a handheld spirometer that linked to an app on their phone, and that allowed us to capture spirometry remotely,” Wang said.

Participants also completed the Asthma Control Test (ACT) and forced exhaled nitric oxide testing once each trimester. Once the child was born, the researchers assessed birth outcomes and the acceptability of the monitoring system.

The most common environmental exposures included spending more than 6 hours a day in the residence (93.75%), gas stoves (81.25%), pets (56.25%), current or former marijuana use (50%), exposures at work (37.5%), living with a smoker (31.25%), being a former smoker (31.25%) and secondhand smoke from the hallway (25%).

There were significant variations in median indoor PM_2.5 concentrations between homes, the researchers said, and they all exceeded the EPA’s annual 12 µg/m³ annual outdoor limit for “good” air quality.

There also were strong correlations between the measurements obtained with the DustTrak and PurpleAir devices, the researchers said, with a Spearman’s rho total of 0.977.

“The PurpleAir was able to capture the indoor air quality with pretty high fidelity,” Wang said.

Wang also expressed confidence in the results provided by the remote spirometry.

“Ninety-six percent of all the remote spirometry was considered ‘A’ grade by [American Thoracic Society] standards,” Wang said. “It was high quality.”

Participants used a rescue inhaler during 47% of the days recorded in the activity and respiratory symptom diary. Also, asthma symptoms bothered participants on 37% of the days, and 83% of the days included more than 6 hours at home. Other daily influences included candles or incense (42%), cleaning (80%), cooking (73%) and smoking (21%).

The median FeNO was 13 ppb (interquartile range [IQR], 9-17), and the median ACT score was 16 (IQR, 14-22).

Finally, 91.4% of the participants said that the video coached remote spirometry sessions were acceptable.

Based on these findings, the researchers said that low-cost, remote methods for monitoring indoor air pollution and asthma health in high-risk pregnant women can achieve high fidelity and possibly improve the surveillance of respiratory health in larger population studies.

“We found that it was feasible to do this kind of remote monitoring and remote spirometry during these people’s pregnancies,” Wang said. “And, we overall have found that indoor air quality tends to be much worse than outdoor air quality, which was an interesting finding.”

Wang said that she and her colleagues hope this pilot study can lead to larger studies that delve into how indoor air quality and activities correlate with spirometry and respiratory health in a pregnant population. Meanwhile, recruitment continues for this study.

“Some of the things we’re looking at next are the addition of nutritional data. We’re looking at what these women are eating during their pregnancy and how that affects respiratory health,” Wang said. “We’re also planning to potentially monitor indoor air quality for the entirety of someone’s pregnancy just to get more data.”