What are ventilation-related recommendations and suggestions for adults with COVID-19?

Updated: Jun 18, 2020
  • Author: Guy W Soo Hoo, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

There are considerable differences in opinion and controversy on the use of noninvasive ventilatory devices in patients with novel coronavirus disease 2019 (COVID-19). Much of this stems not from issues with efficacy, but from questions and concerns about aerosolization of potentially infectious exhaled gas, which may increase the possibility of spreading this infection to other healthcare workers or patients. Increased exhaled air dispersion has been demonstrated in simulation studies with mannequins with the amount of noted dispersion increasing with higher applied pressures (IPAP 18 cm water). [37] However, this does not seem to have translated to an increase in infections when reviewing the experience with severe acute respiratory syndrome (SARS), although in a small number of patients (20). [38] The authors did note endotracheal intubation was avoided in 70% of the patients with shorter ICU lengths of stay (3.1 vs 21.3 days, P< .001), with no nosocomial SARS infections noted in 105 healthcare workers involved with these patients. In addition to good infection control practices, they also mitigated the potential production of droplets with use of a facial mask (as opposed to a nasal mask), exhalation device with reduced jet-expired air, and a viral bacterial filter placed before the exhalation device. On the other hand, in a case control study to identify risk factors for a super-spreading nosocomial event defined as clusters of more than 3 cases, the use of high-flow oxygen and BiPAP were risk factors, although BIPAP did not achieve statistical significance in local-site multivariate models but only in pooled analysis. [39] In addition, the use of a dual-limb circuit noninvasive ventilator as opposed to one with a single-limb circuit, which typically has a circuit leak or leak valve to prevent carbon dioxide rebreathing, may also provide additional control of environmental aerosol generation.

In a retrospective cohort study of 26 healthcare workers who developed SARS, 38% had exposure to noninvasive ventilation (NIV), whereas 8% were exposed to high-flow oxygen, but neither modality was identified with increased transmission of SARS in a logistic regression model. [40] In a systematic review of the literature and risk of infections to healthcare workers with aerosol-generating procedures, NIV generated an odds ratio (OR) of 3.1 (95% confidence interval [CI], 1.4-6.8), but this only involved two small cohort studies. No association was noted with high-flow nasal cannula (HFNC) oxygen, but only one cohort was included in the analysis. [41] In comparison, higher ORs were identified with tracheal intubation (OR, 6.6; 95% CI, 2.3-18.9) and manual ventilation before intubation also had an increased OR (2.6; 95% CI, 1.3-6.4). This summarizes the experience and solutions applied during the SARS epidemic, which was also due to a coronavirus.

Because of the potential risk for nosocomial aerosol transmission, the role of NIV in the management of hypoxemic respiratory failure due to COVID-19 pneumonia, remains unsettled. While NIV and HFNC oxygen are options for the management of hypoxemic respiratory failure, some medical centers have raised concern for their use given the potential risk for nosocomial transmission of coronavirus. On the other hand, these options have been demonstrated to avoid intubation, which is a crucial aspect of management as patient demand has exceeded the inventory of ventilators at some sites, leading to difficult management and possible ethical conflicts in patient care.

The use of HFNC and NIV in the treatment of COVID-19 pneumonia and respiratory failure has varied greatly in series reported from worldwide sites. This may be in part a reflection of local practices, but it may also be a reflection of the severity of respiratory failure, as HFNC and NIV are not typically used in patients with severe hypoxemic respiratory failure, defined as low PaO2/FIO2 less than 200. There are also risks for aerosolization with both NIV and HFNC, but different practices may mitigate that risk as outlined above for NIV with the use of lower flows, a surgical mask on the patient, and close attention to minimizing condensation of tubing. These reports have focused on the overall experience in managing respiratory failure, and there has not been specific attention to noninvasive therapies except for one report from China. They retrospectively reviewed their experience and reported on a small group of 17 patients treated with HFNC in 7 (41%) of their patients, all with PaO2/FIO2 less than 200, but those failures also went on to be treated with NIV and only 2 (11.7% of those treated with HFNC and NIV) eventually required intubation. [42]

In three series from China, in a group of 138 patients with an overall death rate of 4.3%, 36 of their patients were treated in the ICU, with 11% receiving HFNC oxygen and 42% NIV, but it is not entirely clear in how many subjects these modalities had failed. [43] In another cohort of 201 patient with ARDS and overall death rate of 21.9%, HFNC (includes mask oxygen) use rates were 48% and NIV 30%. [44] They reported 42% of their cohort had ARDS and 33% were treated with mechanical ventilation, but they provided no information on the number in who whom HFNC oxygen and NIV failed. In a report that focused on 168 deaths, 34% received HFNC oxygen and 43% NIV, but only 20% were intubated. [45]

In the largest reported series from Italy, their cohort consisted of 1591 patients with a 26% mortality rate at the time of their report. The vast majority of patients were treated with invasive mechanical ventilation (88%) and 11% were treated with NIV. [46] In four US studies, two from Washington state, with 24 and 21 patients, respectively, with mortality rates of 50% and 67%, use of HFNC oxygen was 42% and 5%, respectively, NIV was 0% and 19%. [47, 48] In the largest case series from New York of 5700 patients, 2634 who had been discharged or died, the mortality rate was 21%, with 320 (12%) intubated. Of the intubated patients, the mortality rate was 88%. No information was provided on HFNC or NIV use. [49] In a cohort from Boston of 66 intubated patients with 16.7% mortality at the time of the report, only one patient was treated with HFNC or NIV (2%) and that patient was eventually intubated. [50]

It is evident that use of HFNC oxygen and NIV is much different in China than Italy and the United States. Until there is further analysis, it will be difficult to ascertain the true impact and/or advantage of HFNC oxygen and NIV in COVID-19 pneumonia. However, these modalities can be used, and based on the experiences with SARS, with minimal impact for healthcare workers provided proper infection control practices are in place. It should also be noted that the vast majority of the SARS experience occurred in the context of negative-pressure rooms, and this may be an important factor for the use of these modalities in COVID-19, as this has been largely unreported in these case series. One of the advantages in past use of HFNC or NIV in patients with hypoxemic respiratory failure was the ability to avoid intubation. While this may still be the case with COVID-19, the magnitude of this effect remains to be determined.

The following ventilation clinical practice guidelines in adults with COVID-19 were released by the European Society of Intensive Care Medicine and the Society of Critical Care Medicine [51] :

  • It is suggested to start supplemental oxygen if the peripheral oxygen saturation (SPO 2) is less than 92%. It is recommended to start supplemental oxygen if the SPO 2 is less than 90%.
  • In the event of acute hypoxemic respiratory failure on oxygen, it is recommended that the SPO 2 be maintained at no higher than 96%.
  • In patients with acute hypoxemic respiratory failure despite conventional oxygen therapy, it is suggested that a high-flow nasal cannula be used rather than conventional oxygen therapy.
  • In patients with acute hypoxemic respiratory failure, it is also suggested that a high-flow nasal cannula be used over noninvasive positive-pressure ventilation.
  • In these patients with acute hypoxemic respiratory failure, in the event a high-flow nasal cannula is not available and the patient has no urgent indication for endotracheal intubation, it is suggested that a trial of noninvasive positive-pressure ventilation be conducted, with close monitoring and short-interval assessment for worsening of respiratory failure.
  • While considered an option, no recommendation was made regarding helmet noninvasive positive-pressure ventilation versus mask noninvasive positive-pressure ventilation.
  • In patients receiving either noninvasive positive-pressure ventilation or high-flow nasal cannula, it is recommended they be closely monitored for worsening respiratory status; early intubation in a controlled setting is recommended if worsening occurs.
  • In patients with acute respiratory distress syndrome (ARDS) who are on mechanical ventilation, it is recommended to use low-tidal-volume ventilation (4-8 mL/kg of predicted body weight) versus higher tidal volumes (>8 mL/kg).
  • In patients with ARDS who are on mechanical ventilation, it is recommended to target plateau pressures at less than 30 cm water.
  • In patients with moderate-to-severe ARDS who are on mechanical ventilation, it is suggested to use a higher positive end-expiratory pressure (PEEP) strategy versus a lower PEEP strategy. When using a higher PEEP strategy (ie, PEEP >10 cm water), monitor patients for barotrauma.
  • In patients with ARDS who are on mechanical ventilation, it is suggested to use a conservative fluid strategy versus a liberal fluid strategy.
  • In patients with moderate-to-severe ARDS who are on mechanical ventilation, it is suggested to use prone ventilation for 12-16 hours versus no prone ventilation.
  • In patients with moderate-to-severe ARDS who are on mechanical ventilation, it is suggested to use, as needed, intermittent boluses of neuromuscular blocking agents versus a continuous infusion, to facilitate protective lung ventilation.
  • Use of a continuous infusion of neuromuscular blocking agents is suggested in the event of persistent ventilator dyssynchrony, a need for ongoing deep sedation, prone ventilation, or persistently high plateau pressures.
  • In patients with ARDS who are on mechanical ventilation, routine use of inhaled nitric oxide is not recommended.
  • In mechanically ventilated patients with severe ARDS and hypoxemia despite optimization of ventilation and other rescue strategies, a trial of inhaled pulmonary vasodilator is suggested as rescue therapy; if rapid improvement in oxygenation is not observed, taper off treatment.
  • In mechanically ventilated patients with severe ARDS and hypoxemia despite optimization of ventilation, use of recruitment maneuvers is suggested over not using recruitment maneuvers. If recruitment maneuvers are used, staircase (incremental PEEP) recruitment maneuvers are not recommended.
  • In those patients on mechanical ventilation who have refractory hypoxemia despite optimization of ventilation and who have undergone rescue therapies and proning, it is suggested to use venovenous extracorporeal membrane oxygenation (EMCO) if available; alternatively, refer the patient to center that has ECMO. However, because EMCO is resource-intensive and it requires experienced centers/healthcare workers and infrastructure, it should only be considered in carefully selected patients with severe ARDS.

Summary

HFNC and NIV have been effective in the treatment of hypoxemic respiratory failure in SARS and COVID-19.

The severity of hypoxemic respiratory failure defined as PaO2/FIO2 less than 200 may identify patients better suited for treatment with invasive ventilation.

The risk of transmission of potentially infectious aerosols may be mitigated by the use of filters, personal protective equipment, and negative-pressure rooms.

Local experience and expertise are important factors in the use of HFNC oxygen and NIV.

HFNC and NIV may avoid intubation in some patients with COVID-19 pneumonia and respiratory failure, but this remains to be determined and the use of these modalities should be made on a case-by-case basis.


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