Negative pressure face shield for flexible laryngoscopy in the COVID-19 era

Abstract

Objective: Introduce novel methods and materials to limit microdroplet spread when performing transnasal aerosol generating procedures in the COVID-19 era.

Methods: Prototypes of a negative pressure face shield (NPFS) were tested then used clinically to create a suction-clearing negative pressure microenvironment with controlled access to the nose and mouth. Air pressure measurements within prototypes were followed by prospective evaluation of 30 consecutive patients treated with the device assessed through questionnaires and monitoring oximetry.

Results: The NPFS is a transparent acrylic barrier with two anterior instrumentation ports and a side port to which continuous suction is applied. It is positioned on a stand and employs a disposable antimicrobial wrap to secure an enclosure around the head. This assembly was successfully used to complete transnasal laryngoscopy in all 30 patients studied. Tolerance of the design was excellent, with postprocedure questionnaire identifying no shortness of breath (27/30), no claustrophobia (27/30), no pain (29/30), and no significant changes in pulse oximetry.

Conclusion: Diagnostic laryngoscopy was successfully performed in a negative pressure microenvironment created to limit dispersion of aerosols. Further application of the NPFS device is targeted for use with transnasal laryngeal laser and biopsy procedures to be followed by additional modification to enable intranasal and intraoral procedures in a similar protected environment.

Level of evidence: Level 2b (Cohort Study).

Keywords: COVID‐19; diagnostic flexible; laryngoscopy; laryngoscopyaerosol generating procedure.

FIGURE 1

The acrylic negative pressure face shield oriented upright demonstrating inferior attachment flange (dotted arrows), flat upper surface, anterior access ports and suction port on the side

FIGURE 2

A stable camera stand is employed to secure the negative pressure face shield in front of the patient's face

FIGURE 3

The H100 “one step sterilization wrap” is unfolded and taped circumferentially around the back of the negative pressure face shield (NPFS) (black arrows) and then pulled forward to permit the patient to place their face in the device (white arrows)

FIGURE 4

Testing negative pressure with full wall suction applied (here shown with second port opened). An average of 18 individual readings was −0.0131 in. of water

FIGURE 5

The negative pressure face shield with sterilization wrap is rotated in place and secured around the neck

FIGURE 6

Instillation of nasal decongestant with anesthesia through anterior access port. Note the full protective equipment as depicted in examining this patient early in the study was modified with further experience to employ only a face shield, mask, and gloves without perceived need for gown or N95

FIGURE 7

The procedure is done with the flexible scope passed through the upper of two ports

FIGURE 8

The end of a cotton tipped applicator is used to create a small opening providing a tight fit through which the flexible laryngoscope is placed. Note the procedure may be done with the patient on oxygen as this man required 24 hours/day at 3 L per minute

FIGURE 9

Successful experience in use of the negative pressure face shield permitted safely performing the flexible transnasal laryngoscopy without addition of gown or N95

FIGURE 10

Pre‐, intra‐, and postprocedure pulse oximetry measurements identified saturation SpO₂ consistently above 96%. NPFS, negative pressure face shield

FIGURE 11

Postprocedure assessment by the patients identified no more than “slight” ratings for claustrophobia, shortness of breath and pain during the procedure. NPFS, negative pressure face shield