key: cord-0892848-l0viz3qv
authors: Eslahpazir, Benjamin; Huang, Jeffrey
title: Negative Pressure Airway Management Hood for COVID-19 Patients during Invasive Airway Procedures
date: 2020-07-24
journal: Anesthesiology
DOI: 10.1097/aln.0000000000003516
sha: 181645be2646afc1d26c87465a23e4358e74c781
doc_id: 892848
cord_uid: l0viz3qv

nan

O ur group created an economical, disposable, and readily available negative-pressure system for protection against airborne viral particles when performing aerosolizing procedures ( fig. 1A) . This system uses a square aluminum frame mounted onto the end of an operating room table. The hood is created from a 42 × 74-inch transparent C-arm mobile x-ray drape, modified with a vertical slit from the bottom opening up to approximately 3 feet from the top (see video, Supplemental Digital Content 1, http://links.lww.com/ALN/C466). After the patient is transferred to the operating room table and fitted with a mask for preoxygenation, the drape is placed over the patient with the vertical slit oriented underneath the mattress as the drape is advanced in a sleeve-like fashion over the patient's head and torso. The drape is then securely fastened to the frame ( fig. 1A ). The frame remains external to the drape for removal when necessary. Three openings are cut into the drape as entry points for the breathing circuit, suction tubing, and GlideScope (Verathon Inc., USA). Two 4 × 4.75-inch IV-style Tegaderm (3M Inc., USA) dressings are then placed vertically on the drape for arm access similar to the typical vacuum glove box design, placed at a distance at least one to one-and-a-half shoulder-width apart ( fig. 1B ). Both dressings are modified with a vertical cut to facilitate arm access. Next, a disposable Argyle (Cardinal Health Inc., USA) Poole suction instrument is connected to suction tubing within the drape to serve as a nonocclusive negative pressure vacuum source. The opposite end of the tubing is connected to an anesthesia machine to ensure that evacuated air is sterilized in the central medical vacuum system. The GlideScope handle is then connected to its cord inside the hood in preparation for intubation. All points of hood entry can be sealed with additional Tegaderm dressings to ensure an isolated environment. Once the vacuum system is activated, the patient may then undergo intubation.

When the operator's arms are removed from the drape after intubation, each arm access site is quickly sealed with additional Tegaderm dressings by an assistant. The frame can then be removed for procedures involving the upper extremities, thorax, or neck, as the drape may remain over the patient and adjusted to avoid the sterile field and not impede the surgeon. Replacing the frame and resuspending the drape is necessary for extubation. Of note, this system maintains negative pressure throughout all stages of anesthesia.

In addition to the American Society of Anesthesiologists coronavirus disease 2019 (COVID-19) personal protective equipment guidelines for invasive airway procedures, 1 the user may also choose to don additional protective sleeves and an additional layer of gloves.

As a proof of concept, we performed a validation test on the final construct to assess the hood's air exchange rate. The drape's internal volume was filled with dry ice steam. A timer was then started with the suction valve 

opened to the maximum setting. Four observers (three anesthesiologists and one surgeon) watched the steam evacuate under negative pressure until all four observers agreed that the steam was completely removed, at which time the timer was stopped. This protocol was repeated two more times, resulting in an air turnover time of 43, 39, and 46 s, respectively (mean of 42 s). These results correlate with previous reports of GE (General Electric Co., USA) anesthesia machines producing a mean suction flow rate of 47.6 l/min. 2 Thus, in addition to barrier protection from droplet spray with clear plastic drapes, 3 our negative pressure system provides added protection against aerosol particles.

Our experience so far is suggestive of a rapid learning curve but may always require additional time to prepare for each case, even if used routinely. Furthermore, it may be easy to omit equipment necessary for intubation, maintenance, and extubation before induction, and we therefore recommend using an equipment checklist during hood assembly.

UPDATE: The use of personal protective equipment by anesthesia professionals during the COVID-19 pandemic -Joint position statement

Are there guidelines for anesthesia suction?

Clear plastic drapes may be effective at limiting aerosolization and droplet spray during extubation: Implications for COVID-19

The authors thank Jinping Wang, M.D., Ph.D., Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, for his advisory role and reviewing this article.

The authors declare no competing interests.