Aerosol-generating procedure explained

An aerosol-generating procedure (AGP) is a medical or health-care procedure that a public health agency such as the World Health Organization or the United States Centers for Disease Control and Prevention (CDC) has designated as creating an increased risk of transmission of an aerosol borne contagious disease, such as COVID-19. The presumption is that the risk of transmission of the contagious disease from a patient having an AGP performed on them is higher than for a patient who is not having an AGP performed upon them. This then informs decisions on infection control, such as what personal protective equipment (PPE) is required by a healthcare worker performing the medical procedure, or what PPE healthcare workers are allowed to use.

Designation of a procedure as an AGP may indicate a presumption that such a procedure causes the emission of more aerosols than a patient not undergoing the procedure. Such a position is at increasing odds with the scientific understanding of bioaerosol production and airborne transmission of respiratory infections.[1] [2] [3] [4] At times, healthcare workers concerned about their own risk of contracting airborne infections have been denied access to respirators outside the employment of AGPs.[5]

Medical procedures that have been designated as AGPs include positive-pressure mechanical ventilation including BiPAP and continuous positive airway pressure (CPAP), high-frequency ventilation, tracheal intubation,[6] airway suction, tracheostomy, chest physiotherapy, nebuliser treatment, sputum induction, bronchoscopy[7] and ultrasonic scaling and root planing. Different public health agencies have different lists of AGPs. The term AGP became popular during the 2003 SARS epidemic, where small retrospective studies showed a higher rate of infection amongst healthcare workers in which the AGPs were performed.

COVID-19 pandemic

The COVID-19 pandemic[8] [9] has prompted research to measure the aerosols produced by patients during some AGPs including tracheal intubation and extubation,[10] gastroscopies, colonoscopies and trans-nasal endoscopies.[11] The AGPs studied generate less aerosols than a cough or even just breathing,[12] [13] [14] so some AGPs may not increase the risk from aerosol-borne diseases such as COVID-19 significantly above that of a patient breathing or coughing normally. In a study that looked for viral RNA in air samples taken near patients with COVID-19, no correlation was found between finding viral RNA and mechanical ventilation, high flow nasal cannula, nebuliser treatment or non-invasive ventilation.[15] However data are still lacking for many AGPs. Conversely, fine and ultrafine aerosols constitute the majority of all detectable viral RNA in COVID-19 positive symptomatic and asymptomatic individuals during breathing, talking, and singing.[16]

Notes and References

  1. Zayas. Gustavo. Chiang. Ming. Wong. Eric. MacDonald. Fred. F Lange. Carlos. Senthilselvan. Ambikaipakan. King. Malcolm. 21 March 2012. "Cough aerosol in healthy participants: fundamental knowledge to optimize droplet-spread infectious respiratory disease management" . BMC Pulmonary Medicine. 12 . 10.1186/1471-2466-12-11. free . 22436202 . "Small size droplets (< 1 μm) predominated the total number of droplets expelled when coughing". 3331822.
  2. Stadnytskyi. Valentyn. Bax. Christina E.. Bax. Adriaan. Anfinrud. Philip. May 13, 2020. "The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission". 117 . 22 . 11875–11877 . Proceedings of the National Academy of Sciences. 10.1073/pnas.2006874117. free . 32404416 . 7275719 . 2020PNAS..11711875S . "These observations confirm that there is a substantial probability that normal speaking causes airborne virus transmission in confined environments.".
  3. Bourouiba. Lydia. October 6, 2020. The Fluid Dynamics of Disease Transmission. 53 . 473–508 . Annual Review of Fluid Mechanics. 10.1146/annurev-fluid-060220-113712 . 21 March 2024.
  4. Wang. Chia C.. Prather. Kimberly A. Sznitman. Josué. Jimenez. Jose L. Lakdawala. Seema S.. Tufekci. Zeynep. Marr. Linsey C.. 27 Aug 2021. Airborne transmission of respiratory viruses. Science. 373. 6558 . 10.1126/science.abd9149. 34446582 . 8721651 . "Given the lack of evidence for droplet and fomite transmission and the increasingly strong evidence for aerosols in transmitting numerous respiratory viruses, we must acknowledge that airborne transmission is much more prevalent than previously recognized.".
  5. News: MacIntyre. C Raina. Veness. Benjamin. Ananda-Rajah. Michelle. June 16, 2021. "At last, health, aged care and quarantine workers get the right masks to protect against airborne coronavirus". The Conversation. 21 March 2024. "The existing guidelines said health providers working around COVID-19 patients should wear a surgical mask. It restricted use of the more protective P2 or N95 masks, which stop airborne particles getting through, to very limited scenarios. These involved “aerosol-generating procedures”, such as inserting a breathing tube.".
  6. El-Boghdadly. K.. Wong. D. J. N.. Owen. R.. Neuman. M. D.. Pocock. S.. Carlisle. J. B.. Johnstone. C.. Andruszkiewicz. P.. Baker. P. A.. Biccard. B. M.. Bryson. G. L.. 2020-06-09. Risks to healthcare workers following tracheal intubation of patients with COVID-19: a prospective international multicentre cohort study. Anaesthesia. 75 . 11 . 1437–1447 . 10.1111/anae.15170. 7300828 . 1365-2044. 32516833. free.
  7. Tran K, Cimon K, Severn M, Pessoa-Silva CL, Conly J . Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review . PLOS ONE . 7 . 4 . e35797 . April 2012 . 22563403 . 10.1371/journal.pone.0035797 . 3338532. free . 2012PLoSO...735797T .
  8. Wilson. Nick. Corbett. Stephen. Tovey. Euan. 2020. Airborne transmission of covid-19. BMJ . live. https://web.archive.org/web/20200821103308/https://www.bmj.com/content/370/bmj.m3206 . 2020-08-21 . BMJ 2020;370:m3206. 370 . m3206 . 10.1136/bmj.m3206. 32819961. 221178291 . free.
  9. Klompas. Michael. Baker. Meghan. Rhee. Chanu. 2021-02-01. What Is an Aerosol-Generating Procedure?. JAMA Surgery. en. 156. 2. 113–114. 10.1001/jamasurg.2020.6643. 33320188 . 2168-6254. free.
  10. Shrimpton . A. J. . Brown . J. M. . Gregson . F. K. A. . Cook . T. M. . Scott . D. A. . McGain . F. . Humphries . R. S. . Dhillon . R. S. . Bzdek . B. R. . Hamilton . F. . Reid . J. P. . 2021-08-26 . A quantitative evaluation of aerosol generation during manual facemask ventilation . en . 10.1101/2021.08.23.21262441v1.
  11. Phillips . Frank . Crowley . Jane . Warburton . Samantha . Gordon . George S.D. . Parra-Blanco . Adolfo . June 2022 . Aerosol and droplet generation in upper and lower gastrointestinal endoscopy: whole procedure and event-based analysis . Gastrointestinal Endoscopy . 96 . 4 . en . 603–611.e0 . 10.1016/j.gie.2022.05.018. 35659608 . 9386278 . 249324970 . free .
  12. Nestor. C. C.. Wang. S.. Irwin. M. G.. 2021. Are tracheal intubation and extubation aerosol-generating procedures?. Anaesthesia. en. 76. 2. 151–155. 10.1111/anae.15328. 0003-2409. 7753480. 33274761.
  13. Brown. J.. Gregson. F. K. A.. Shrimpton. A.. Cook. T. M.. Bzdek. B. R.. Reid. J. P.. Pickering. A. E.. 2021. A quantitative evaluation of aerosol generation during tracheal intubation and extubation. Anaesthesia. en. 76. 2. 174–181. 10.1111/anae.15292 . 33022093 . 7675579 . 0003-2409. free.
  14. Dhillon. R. S.. Rowin. W. A.. Humphries. R. S.. Kevin. K.. Ward. J. D.. Phan. T. D.. Nguyen. L. V.. Wynne. D. D.. Scott. D. A.. the Clinical Aerosolisation Study Group. Yule. A.. 2021. Aerosolisation during tracheal intubation and extubation in an operating theatre setting. Anaesthesia. en. 76. 2. 182–188. 10.1111/anae.15301. 0003-2409. 7675280. 33047327.
  15. Thuresson . Sara . 2022 . Airborne SARS-CoV-2 in hospitals – effects of aerosol-generating procedures, HEPA-filtration units, patient viral load and physical distance . Clinical Infectious Diseases. 75 . 1 . e89–e96 . 10.1093/cid/ciac161 . 35226740 . 9383519 . free .
  16. Coleman. Kristen K. Douglas Jie. Wen Tay. Kai. Sen Tan. Sean Wei. Xiang Ong. The Son. Than. Ming Hui. Koh. Yi Qing. Chin. Haziq. Nasir. Tze Minn. Mak. Justin. Jang Hann Chu. Donald K. Milton. Vincent T K. Chow. Paul Anantharajah. Tambyah. Mark. Chen. Kwok Wai. Tham. 15 May 2022. Viral Load of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Respiratory Aerosols Emitted by Patients With Coronavirus Disease 2019 (COVID-19) While Breathing, Talking, and Singing. March 20, 2024. Clinical Infectious Diseases. 74 . 10 . 1722–1728 . 10.1093/cid/ciab691 . 34358292 . 8436389 .

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