Some Nasogastric Intubation Procedures Lead to Less Aerosolization Than Feared

Will Pass

June 02, 2021

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," 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," 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," 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, Verbeure noted that particle counts were never higher than at the start of the examination. Fluorescein visualization showed "surprisingly little droplet spread," Verbeure said, apart from some contamination around the patient's neck.

"Esophageal investigations do not seem to generate additional [aerosol] particles," 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," Verbeure added.

SORTing the Results

According to Mahdi Najafi, MD, associate professor in the department of anesthesiology at Tehran University of Medical Sciences, Iran, and adjunct professor at Schulich School of Medicine & Dentistry, Western University, London, Ontario, the findings offer valuable insights. "[This study] is very important for at least two reasons: The extent of using this procedure in patient care, especially in the critical care setting, and the paucity of information for COVID-19 transmission and route of transmission as well," Najafi said in an interview.

Yet he cautioned against generalizing the results. "We cannot extend the results to all nasogastric tube intubations," Najafi said. "There are reasons for that. The tube for manometry is delicate and flexible, while the nasogastric tube used for drainage and GI pressure release — which is used commonly in intensive care and the operating room — is larger and rather rigid. Moreover, the patient is awake and conscious for manometry while the other procedures are done in sedated or unconscious patients."

He noted that nasogastric intubation is more challenging in unconscious patients, and often requires a laryngoscope and/or Magill forceps. "The result [of using these instruments] is coughing, which is undoubtedly the most important cause of aerosol generation," Najafi said. "It can be regarded as a drawback to this study as well. The authors would be better to report the number and/or severity of the airway reactions during the procedures, which are the main source of droplets and aerosols."

To reduce risk of coronavirus transmission during nasogastric intubation of unconscious patients, Najafi recommended the SORT (Sniffing position, nasogastric tube Orientation, contralateral Rotation, and Twisting movement) maneuver, which he introduced in 2016 for use in critical care and operating room settings.

"The employment of anatomical approach and avoiding equipment for intubation were devised to increase the level of safety and decrease hazards and adverse effects," Najafi said of the SORT maneuver. "The procedure needs to be done step-by-step and as smooth as possible."

In a recent study, the SORT maneuver was compared with nasogastric intubation using neck flexion lateral pressure in critically ill patients. The investigators concluded that the SORT maneuver is "a promising method" notable for its simple technique, and suggested that more trials are needed.

The investigators and Najafi reported no conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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