Nasogastric intubation for esophageal manometry or impedance monitoring does not generate significant aerosol particles and is associated with minimal droplet spread, according to a Belgian study presented at the annual Digestive Disease Week® (DDW). These findings suggest that standard personal protective equipment and appropriate patient positioning are likely sufficient to protect health care workers from increased risk of coronavirus transmission during tube placement and removal, reported lead author Wout Verbeure, PhD, of Leuven University Hospital, Belgium, and colleagues.
“Subsequent to the COVID-19 peak, [nasogastric tube insertion and extraction] were scaled back based on the assumption that they generate respiratory aerosol particles and droplet spread,” the investigators reported. “However, there is no scientific evidence for this theory.”
To address this knowledge gap, the investigators conducted an observational trial involving SARS-CoV-2-negative patients and including 21 insertions and removals for high-resolution manometry (HRM), plus 12 insertions and 10 removals for 24-hour multichannel intraluminal impedance-pH monitoring (MII-pH). During the study, a Camfil City M Air Purifier was added to the examination room. This was present during 13 of the 21 HRM insertions and removals, allowing for comparison of aerosol particle measurements before and after introduction of the device.
The mechanics of the study
Aerosol particles (0.3-10 mcm) were measured with a Particle Measuring Systems LASAIR II Particle Counter positioned 1 cm away from the patient’s face. For both procedures, measurements were taken before, during, and up to 5 minutes after each nasogastric tube placement and removal. Additional measurements were taken while the HRM examination was being conducted.
To measure droplet spread, 1% medical fluorescein in saline was applied to each patient’s nasal cavity; droplets were visualized on a white sheet covering the patient and a white apron worn by the health care worker. The patients’ masks were kept below their noses but were covering their mouths.
“During the placement and removal of the catheter, the health care worker was always standing sideways or even behind the patient, and they always stood higher relative to the patient to ensure that when there was aerosol or droplet spread, it was not in their direction,” Dr. Verbeure said during his virtual presentation.
During placement for HRM and removal for MII-pH, aerosol particles (excluding those that were 0.3 mcm), decreased significantly. Otherwise, particle counts remained stable. “This shows that these investigations do not generate additional aerosol [particles], which is good news,” Dr. Verbeure said.
When the air purifier was present, placement and examination for HRM were associated with significant reductions in aerosol particles (excluding those that were 0.3 mcm or 0.5 mcm), whereas removal caused a slight uptick in aerosol particles (excluding those that were 0.3 mcm or 0.5 mcm) that did not decline after 5 minutes. “This was actually a surprise to us,” Dr. Verbeure said. “Because we now had an air purifier present, and we expected an even lower number of particles.”
He suggested that the purifier may have been reducing particle counts during HRM examination, thereby lowering baseline values before removal, making small changes more noticeable; or the purifier may have been causing turbulence that spread particles during removal. Whether either of these hypotheses is true, Dr. Verbeure noted that particle counts were never higher than at the start of the examination. Fluorescein visualization showed “surprisingly little droplet spread,” Dr. Verbeure said, apart from some contamination around the patient’s neck.
“Esophageal investigations do not seem to generate additional [aerosol] particles,” Dr. Verbeure concluded. “So wearing the recommended protective gear and also considering the right positioning of the health care worker relative to the patient is important to keep performing this daily clinical routine.” To avoid droplet spread, health care workers should “be aware of the [patient’s] neck region and the direction of the catheter,” Dr. Verbeure added.