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Aerosol generation and droplet spread during nasogastric intubation in the COVID-19 era
  1. Wout Verbeure1,
  2. Annelies Geeraerts1,
  3. I-Hsuan Huang1,2,
  4. Lien Timmermans3,
  5. Joran Toth1,
  6. Hannelore Geysen1,
  7. Louise Cools1,
  8. Florencia Carbone1,3,
  9. Jolien Schol1,
  10. Herman Devriese4,
  11. Rico Haesaerts3,
  12. Hideki Mori1,
  13. Tim Vanuytsel1,3,
  14. Jan Tack1,3
  1. 1 Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Chronic Diseases and Metabolism (ChroMeta), KU Leuven, Leuven, Belgium
  2. 2 Division of Gastroenterology, Department of Internal Medicine, Tri-Service General Hospital, Taipei, Taiwan
  3. 3 Gastroenterology and Hepatology, KU Leuven University Hospitals, Leuven, Belgium
  4. 4 Prevention and Environment, KU Leuven University Hospitals, Leuven, Belgium
  1. Correspondence to Professor Jan Tack, Translational Research Center for Gastrointestinal Disorders (TARGID), Department of Chronic Diseases Metabolism and Ageing (ChroMetA), KU Leuven, Leuven 3000, Belgium; jan.tack{at}

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We read with interest the recent article by Repici et al who reported that gastrointestinal (GI) endoscopy seems relatively safe for medical staff wearing adequate protective measures, with 4.3% of 968 healthcare workers (HCW) in the endoscopy setting infected with COVID-19.1 Similar to GI endoscopy, oesophageal motility studies are common practice and potentially also high-risk medical procedures as COVID-19 may spread through generation of aerosols and droplets during insertion and removal of oesophageal high resolution manometry (HRM) and 24 hours multichannel intraluminal impedance-pH monitoring (pH-MII) probes.2 Current guidelines recommend high-level protection with N95 mask, Filtering FacePiece (FFP)2 or FFP3, double gloves, face shield and gown for HCW during oesophageal physiologic procedures to minimise the risk of transmission.3 4 However, there is a lack of scientific evidence on the spread of aerosols and droplets during nasogastric intubation. Therefore, we performed a prospective study, addressing these concerns.

Patients with a negative COVID-19 test by PCR undergoing nasogastric intubation for HRM or pH-MII were included. During the procedures, patients wore a mask over the mouth and were seated in a lowered position in front of the HCW. Quantification of aerosol (0.3, 0.5, 1.0, 3.0, 5.0 and 10 μm) was done using the Lasair II Particle Counter (Particle Measuring Systems, Boulder (Colorado), USA). For both probe positioning and removal, measurements were performed before and after 1 and 5 min. For droplet visualisation, fluorescein was applied to the nasal cavity at the beginning of the investigation. Patients were covered with a white sheet and HCW wore an apron allowing quantification of droplet spread. After the procedure, fluorescent drops on the sheet and apron were visualised with a Woods ultraviolet light, photographed and analysed using ImageJ. Aerosol particle counts were logarithmically transformed and presented as particles-per-cubic-metre. Statistical analyses were performed using repeated one-way analysis of variance (ANOVA) with stepdown Bonferroni adjustment. Data are presented as mean±SD and significance was set at p<0.05. Fluorescent droplet spread data were presented as total amount of detected spots and total surface per body region.

For aerosol particles generation, we studied 21 HRM examinations (both placement and removal), 12 pH-MII probe placements and 10 removals. One minute after HRM catheter placement, a general significant reduction in aerosol particles of all sizes compared with baseline except for 0.3 and 0.5 µm was observed (p=0.71; p=0.36; p=0.01; p=0.01; p=0.002; p=0.003, in ascending size order, respectively) (figure 1). Five minutes after placement, the number of particles was further reduced except for 0.3 µm (p=0.54). The removal of the HRM catheter did not affect particle spread within 5 min (p=0.053; p=0.75; p=1.00; p=0.75; p=0.77; p=0.77, respectively). The placement of the pH-MII probe did not affect aerosol counts of any size, except for a decrease of 1.0 µm-sized particles 5 min after placement (from 11.25±0.32 to 11.00±0.31; p=0.026). For every particle size, except 0.3 µm, the removal was associated with a reduction in aerosol particle numbers. For sizes 0.5, 1.0 and 3.0 µm, this occurred 1 min after (p=0.003; p=0.004 and p=0.017, respectively), while for the two bigger sizes 5.0 and 10 µm, the reduction occurred after 5 min (p<0.0001 and p=0.001, respectively).

Figure 1

. The number of aerosol particles for different sizes (0.3; 0.5; 1.0; 3.0; 5.0 and 10.0 µm) during a complete esophageal high-resolution manometry examination (n=21) and during placement (n=12) and removal (n=10) of a 24-hour pH-MII probe. Number of particles is shown on a logarithmic scale. Data are presented as mean±SD.

Additionally, little droplet spread was found on the white apron covering the HCW. The highest amount of fluorescein droplet spread was located in the right-sided neck region on the sheet covering the patient, with the highest intensity on pH-MII probe removal.

Our findings showed that oesophageal motility procedures, with a mask covering the patients’ mouth and position adjustments protects from significant aerosol spread and generates only sporadic droplets and this is likely to have a low risk of COVID-19 transmission.

Ethics statements

Ethics approval

The study protocol was approved by the Ethics Committee for clinical research of the University Hospitals Leuven (S64237).



  • Contributors JT designed the study. WV and AG planed and conducted the study. I-HH drafted the manuscript. All authors participated in the data collection and revised and approved the final manuscript.

  • Funding JT is supported by a Methusalem grant of KU Leuven and has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Grünenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and ZeriaJolien Schol is a PhD fellow fundamental research of the Flanders Research Foundation (FWO Vlaanderen).

  • Competing interests TV is a senior clinical investigator of the Flanders Research Foundation (FWO Vlaanderen) and has given Scientific Advice to Takeda, VectivBio, Shire, Dr. Falk Pharma, Tramedico, Truvion and Zealand Pharma and has served on the Speaker bureau for Abbott, Kyowa Kirin, Menarini, Takeda, Tramedico and Truvion.

  • Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

  • Provenance and peer review Not commissioned; internally peer reviewed.