COVID-19 and One-Lung Ventilation.

To the Editor

The Coronavirus Disease 2019 (COVID-19) pandemic highlights the risk of aerosol-generating medical procedures (AGMPs) and has led to the Canadian Anesthesiologists Society (CAS) “COVID-19 Recommendations During Airway Manipulation” (https://www.cas.ca/en/covid-19). One-lung ventilation (OLV) necessitates AGMPs, including intubation, bronchoscopy, deflating operative lung, and airway suctioning,[1] which place the anesthesiologist at high exposure risk.

Distinguishing between aerosolization “vulnerable” procedures and true AGMPs is needed to determine risk to the health care worker (HCW).[2] Vulnerable procedures occur in the absence of gas flow, and accordingly, the risk of aerosolization is minimized. The introduction of gas flow (ie, coughing with intubation) can transform a vulnerable procedure into an AGMP with the production of droplets and aerosols. Ensuring complete neuromuscular blockade and absence of gas flow (silent airway), minimizing periods that the patient’s respiratory system is open to atmosphere (open airway), and isolating patient ventilation from the surrounding atmosphere (closed circuit) are important in reducing the risk of aerosolization during procedures.

Time-sensitive surgical procedures will be performed during the projected time course of the COVID-19 pandemic. There is little published guidance for mitigating the risk of disease transmission among HCWs performing procedures requiring lung isolation and OLV. We have developed suggestions for placement of double-lumen tubes (DLTs) for OLV based on best evidence and local expert consensus. The principle of maintaining a “silent airway” was used as a guide for these strategies.

Goals during “open airway” periods (intubation/fiberoptic bronchoscopy [FOB]/suction)

a. Ensure paralysis

i.Confirm complete neuromuscular blockade

b. Ensure absence of airflow during apnea

i. Adjustable pressure-limiting (APL) valve set to 0

ii. Pause ventilation and gas flow

Perform procedure during apnea period

a. DLT intubation

i. Intubate and immediately confirm position with FOB

ii. Apnea until properly positioned, circuit attached, and DLT cuffs inflated (“closed circuit”)

iii. If concerning desaturation, remove FOB and confirm closed circuit before ventilating

b. Bronchoscopy

i. FOB through diaphragm of bronchoscopy adaptor to maintain closed circuit

ii. Avoid/limit use of suction

Before resuming ventilation, ensure you have a closed circuit:

a. Confirm all ports closed

b. Endotracheal cuffs adequately inflated

Extubation

a.Goal is to minimize coughing

b. Considerations:

i. Place a clear drape over patient’s head to minimize aerosol/droplet exposure

ii.Pharmacologic agents (ie, remifentanil, dexmedetomidine, propofol) to reduce emergence coughing.[3]

General Principles for Patients Undergoing Lung Isolation Procedures

Traditional management of OLV with a DLT includes clamping the appropriate lumen and opening the corresponding bronchoscope port to facilitate lung deflation. This maneuver creates a vulnerable AGMP. To minimize risk, we suggest 2 options (Figure). Bussières et al[4] have published stepwise approaches to expedite lung deflation with bronchial blockers; they also suggested the possibility that maintaining a closed port to the operative side (Figure, panel A) of the DLT, while clamping the appropriate lumen for OLV, could increase resorption atelectasis by eliminating dilution of intra-alveolar O2 with ambient air.[5] The benefit of this method is maintenance of a closed system. Alternatively, to open the operative DLT lumen to atmosphere with the clamp applied, a second filter should be added to the now “open” airway (Figure, panel B). Application of suction to the operative lung to expedite lung collapse can be considered with acknowledgement of inherent risks. To prevent environmental contamination with a soiled FOB, we have adjusted practice to keep it immediately available, but in a container separate from the FOB tower.

The COVID-19 pandemic poses significant challenges with AGMPs as we deliver increasing care toward time-sensitive surgical procedures. Deciphering between fact and fiction, especially in relation to AGMPs and those procedures vulnerable to aerosolization, will be important to investigate and mitigate risk to health care providers.

Management options of connector ports of DLT. A, shows keeping port closed with red arrow pointing to bronchoscope port closed and brown dashed arrow toward clamped lumen to operative lung. B, shows red triangle pointing to additional HEPA filter to "open" operative DLT lumen and brown dashed arrow to clamp remaining on connector to circuit. DLT indicates double-lumen tube; HEPA, high efficiency particulate air; OLV, one-lung ventilation.