To the Editor

The video by Shrestha et al. (Feb. 18 issue)1 shows a method for emergency intubation in a patient with Covid-19 that includes the use of a negative-pressure isolation room. This measure was initially recommended to prevent hospital-acquired infections. However, negative air pressure in rooms in the intensive care unit could increase the risk of invasive pulmonary aspergillosis,2 which has been reported in 10 to 30% of patients with Covid-19 in the intensive care unit.3

Positive-pressure isolation rooms are used to reduce the risk of invasive pulmonary aspergillosis in immunocompromised patients, but their use is not suitable for patients with Covid-19 owing to the risk of airborne transmission. Air quality can be controlled through other solutions, such as portable high-efficiency particulate air (HEPA) filters.4 These filters have proven efficiency in the capture of SARS-CoV-2 particles, and some results have suggested that their use leads to a reduction in the incidence of invasive pulmonary aspergillosis among high-risk patients.5 We suggest that patients with Covid-19 undergo intubation in a neutral-pressure, rather than negative-pressure, room with a portable HEPA filtration system to reduce the incidence of invasive pulmonary aspergillosis.

Nicolas Herzog, M.D.
Christophe Giacardi, M.D.
Marc Danguy des Déserts, M.D.
Military Training Hospital Clermont–Tonnerre, Brest, France

No potential conflict of interest relevant to this letter was reported.

This letter was published on April 21, 2021, at

  1. 1. Shrestha GS, Shrestha N, Lamsal R, et al. Emergency intubation in Covid-19. N Engl J Med 2021;384(7):e20.

  2. 2. Ichai P, Saliba F, Baune P, Daoud A, Coilly A, Samuel D. Impact of negative air pressure in ICU rooms on the risk of pulmonary aspergillosis in COVID-19 patients. Crit Care 2020;24:538-538.

  3. 3. Alanio A, Dellière S, Fodil S, Bretagne S, Mégarbane B. Prevalence of putative invasive pulmonary aspergillosis in critically ill patients with COVID-19. Lancet Respir Med 2020;8(6):e48-e49.

  4. 4. Mousavi ES, Kananizadeh N, Martinello RA, Sherman JD. COVID-19 outbreak and hospital air quality: a systematic review of evidence on air filtration and recirculation. Environ Sci Technol 2021;55:4134-4147.

  5. 5. Abdul Salam Z-H, Karlin RB, Ling ML, Yang KS. The impact of portable high-efficiency particulate air filters on the incidence of invasive aspergillosis in a large acute tertiary-care hospital. Am J Infect Control 2010;38(4):e1-e7.

To the Editor

Developing countries may not have sophisticated equipment to aid in the performance of tracheal intubation. If a tracheal tube is mistakenly placed into the esophagus, the soft walls will most likely collapse into and obstruct the tip of a tracheal tube when negative pressure is applied. Esophageal negative-pressure detectors that use bladder syringe aspiration,1,2 a squeezed Ellick bladder evacuator,3 or a Positube endotracheal detection device may be applied if the tube has not been observed to pass through the vocal cords and exhaled carbon dioxide detection is not available. If the endotracheal tube has been placed in the trachea, air will be aspirated from the tip of the tube, because the trachea is a rigid, cartilage-supported structure. Without a direct view of the glottic opening, an elbow-tipped bougie at least 60 cm in length may be used to assist in intubation.4,5 If the bougie passes its full length from the patient’s lips, the endotracheal tube is in the esophagus. Because the trachea varies in length, auscultation should be performed, especially in children, in order to avoid bronchial intubation. Tracheal cuff pressures should be determined, kept within a defined range, and measured regularly during lung ventilation.

William F.S. Sellers, F.R.C.A.
University Hospital Coventry and Warwickshire, Coventry, United Kingdom

No potential conflict of interest relevant to this letter was reported.

This letter was published on April 21, 2021, at

  1. 1. Wee MYK. The oesophageal detector device: assessment of a new method to distinguish oesophageal from tracheal intubation. Anaesthesia 1988;43:27-29.

  2. 2. Sellers WFS, Holesworth SP. Updating Wee’s oesophageal detector. Anaesthesia 2003;58:615-616.

  3. 3. Nunn JF. The oesophageal detector device. Anaesthesia 1988;43:804-804.

  4. 4. Birmingham PK, Cheney FW, Ward RJ. Esophageal intubation: a review of detection techniques. Anesth Analg 1986;65:886-891.

  5. 5. Kidd JF, Dyson A, Latto IP. Successful difficult intubation: use of the gum-elastic bougie. Anaesthesia 1988;43:437-438.

To the Editor

With regard to the recent video by Shrestha et al., we would like to share additional points that we think are helpful in performing intubation safely. In addition to the use of personal protective equipment (PPE), we encourage that emergency intubation be performed in a negative-pressure tent because airway manipulation poses a great risk of viral dissemination in the era of Covid-19.1,2 The Food and Drug Administration has authorized various negative-pressure barrier enclosures because, with no safety concerns at this time, the benefits for emergency use outweigh the risks.3 This method can be used for other aerosol-generating procedures, such as airway suctioning, bronchoscopy, and tracheostomy. In addition, the implementation of a strong means of communication, such as a two-way radio system (walkie-talkie), could be highly effective in facilitating communication between care providers outside and inside the room. Finally, double-gloving should be encouraged to prevent the transfer of virus to the hands and clothing during removal of PPE.4 These simple and practical steps can further improve safety during emergency intubation.

Jigar Patel, M.D.
Rajesh N. Janapala, M.D.
Ali Pourmand, M.D., M.P.H.
George Washington University School of Medicine and Health Sciences, Washington, DC

No potential conflict of interest relevant to this letter was reported.

This letter was published on April 21, 2021, at

  1. 1. Bidkar P, Goneppanavar U, Kaur J, Ramamoorthy SV. Safety tent for enhanced personal protection from aerosol-generating procedures while handling the COVID-19 patient airway. J Anaesthesiol Clin Pharmacol 2020;36:Suppl 1:S157-S160.

  2. 2. Hung O, Hung D, Hung C, Stewart R. A simple negative-pressure protective barrier for extubation of COVID-19 patients. Can J Anaesth 2020;67:1478-1480.

  3. 3. Food and Drug Administration. Protective barrier enclosures without negative pressure used during the COVID-19 pandemic may increase risk to patients and health care providers — letter to health care providers. 2020 (

  4. 4. Casanova LM, Rutala WA, Weber DJ, Sobsey MD. Effect of single- versus double-gloving on virus transfer to health care workers’ skin and clothing during removal of personal protective equipment. Am J Infect Control 2012;40:369-374.


The authors reply: Herzog et al. refer to a recent report that describes the risk of invasive pulmonary aspergillosis among patients undergoing mechanical ventilation in negative-pressure isolation rooms.1 Our video describes the care of patients undergoing endotracheal intubation, an aerosolizing procedure. Both the Centers for Disease Control and Prevention (CDC) and the American Society of Anesthesiologists recommend performing aerosol-generating procedures in airborne-infection isolation rooms with negative pressure relative to the surrounding area.2,3

Sellers comments that endotracheal tube placement should be verified and notes some measures that may be used. When equipment to detect carbon dioxide, such as a capnography device or colorimetric carbon dioxide detector, is not available to corroborate placement, care providers should use the methods and equipment they are most familiar with and follow institutional guidelines.

Patel et al. note several issues. With regard to the optional use of protective barrier enclosures to perform endotracheal intubation, the Food and Drug Administration currently recommends devices that incorporate negative pressure.4 Protective barrier enclosures should be removed if they hinder the ability of the care provider to manage the airway. As for double-gloving, given that a meticulous doffing process has been established, a second set of gloves may help reduce disease transmission. However, this is not recommended by the CDC. Finally, communication is important during endotracheal intubation in patients with Covid-19. As described in our video, a printed checklist may facilitate the preparation and voicing of concerns. Two-way radios may be useful for care providers inside and outside the isolation room to communicate with each other.

Balancing appropriate patient care with the availability of equipment and the safety of health care providers has been a hallmark of the Covid-19 pandemic. Additional equipment should not replace the use of PPE and, after having been brought into the isolation room, should be discarded or decontaminated in accordance with institutional guidelines.

Robert Canelli, M.D.
Boston Medical Center, Boston, MA

Gentle S. Shrestha, M.D.
Tribhuvan University Teaching Hospital, Kathmandu, Nepal

Rafael Ortega, M.D.
Boston Medical Center, Boston, MA

Since publication of their article, the authors report no further potential conflict of interest.

This letter was published on April 21, 2021, at

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