Knowledge Translation Tools to Guide Care of Non-Intubated Patients With Acute Respiratory Illness During the COVID-19 Pandemic

David Leasa; Paul Cameron; Kimia Honarmand; Tina Mele; Karen J. Bosma

Disclosures

Crit Care. 2021;25(22) 

In This Article

Clinical Management of ARI During the Pandemic

COVID-19 should be suspected in patients presenting with an acute or acute on chronic respiratory illness. In addition to causing de novo ARI, the virus may also cause worsening of underlying cardiorespiratory disease with an acute exacerbation of COPD or CHF, or respiratory failure in the setting of pulmonary hypertension, obstructive sleep apnea (OSA)/obesity hypoventilation syndrome (OHS), or neuromuscular disease. Patients with acute on chronic respiratory failure may or may not have concomitant COVID-19 infection, but appropriate precautions should be taken until confirmed negative by testing. After donning appropriate personal protective equipment (PPE), isolating the patient from other patients, and sending a nasopharyngeal swab viral polymerase chain reaction (PCR) for SARS-CoV-2, the next step is to determine the most appropriate respiratory support.

Figure 1 represents a summary of recommendations as a decision algorithm (1A) and accompanying table (1B) for the early management of ARI during the COVID-19 pandemic. The algorithm is based on upholding best-evidence guidelines for non-COVID patients, and emerging evidence and worldwide clinical experience with COVID-19 during the pandemic. The purpose of this tool is to identify and categorize patients into three groups based on their likelihood of requiring non-AGMP support, AGMP or high-risk AGMP (intubation) as first-line therapy, so that patients can be admitted to the appropriate area within the hospital with the necessary level of expertise and appropriate precautions taken by HCPs. The decision algorithm was designed to be a pragmatic, easily applied bedside tool, and hence, we used pulse oxygen saturation (SpO2) and fraction of inspired oxygen (FiO2) values, but provided relative PaO2/FiO2 values for reference.

Figure 1.

a Acute respiratory illness (ARI) early management decision algorithm (COVID-19). The ARI decision algorithm guides determination of the level of support required for the hypoxemic patient, and patient factors that determine appropriateness for NIV, HFNO, awake prone positioning and intubation. b Personal protective equipment, isolation and level of monitoring required for various treatments and conditions during COVID-19. This table accompanies a and outlines the PPE, isolation strategy and level of monitoring required for non-AGMP, AGMP and high-risk AGMP care. ARI acute respiratory illness, RR, respiratory rate, AGMP aerosol generating medical procedure, COPD chronic obstructive pulmonary disease, OSA obstructive sleep apnea, OHS obesity hypoventilation syndrome, NMD neuromuscular disease, CHF congestive heart failure, WOB work of breathing, HFNO high flow nasal oxygen, NIV non-invasive ventilation, Bi-PAP bi-level positive airway pressure, CPAP continuous positive airway pressure. AAMI Association for the Advancement of Medical Instrumentation, PPE personal protective equipment, ICU intensive care unit

Patients with elevated respiratory rate and SpO2 < 94% on room air need oxygen applied by nasal prongs or face mask.[6] Patients without distress who are able to maintain a SpO2 ≥ 94% on a FiO2 ≤ 0.40 may be admitted to a hospital ward single-patient room and observed.[6] Patients with persistent elevated respiratory rate and moderate to severe hypoxemia require further assessment to determine whether early ETI will be necessary, or if NRS is appropriate.

In an effort to balance the risks of invasive mechanical ventilation with deleterious consequences of delayed intubation, we recommend consideration of intubation as the initial approach for patients with mental status changes (e.g., agitation or obtundation), shock requiring vasopressors, multi-organ failure (e.g., acute kidney injury requiring renal replacement therapy) or unmanageable secretions accompanying hypoxemia or acidosis. Such patients are not appropriate for NRS,[25,26] and early intubation facilitates safe airway management and protective lung ventilation which would not be possible with the spontaneous-breathing patient.[23]

Co-operative patients with single system respiratory failure who do not require prompt intubation may be managed with NRS, but must be monitored closely for response to treatment. Both NIV (bi-level positive airway pressure) and CPAP should remain the treatment of choice as per usual indications: CPAP for CHF and OSA, and NIV for COPD exacerbations, neuromuscular disease or OHS complicated by hypercapnic respiratory failure.[25] If NIV is being considered for acute on chronic hypercapnic respiratory failure, this should be initiated at hospital admission. Do not prevent NIV use where previously appropriate prior to the COVID-19 pandemic.

Patients with de novo hypoxemic respiratory failure may be considered for HFNO[26] or CPAP (preferably by helmet), if HFNO is not available. Potential candidates for HFNO or CPAP should be alert, cooperative, able to protect their airway, with acceptable ventilation (pH > 7.30). Work of breathing should decrease with NRS measures and may be assessed by palpation of the sternomastoid muscle, detection of phasic contraction[27] and/or a reduction in an elevated serum lactate produced by fatiguing respiratory muscles.[28] HFNO and CPAP can support both oxygenation and ventilation by reducing work of breathing for patients with hypoxemia and dyspnea with presumed COVID-19 pneumonia.[29,30] In Lombardy Italy, where numbers of COVID-19 patients surpassed ICU capacity, necessitating NRS in specially developed Respiratory COVID Units, ETI was avoided in approximately 2/3 of patients without increasing the relative risk of death.[12] However, available best practice guidelines[29–31] suggest NRS should not be used for severe hypoxemic respiratory failure with high respiratory rate/high work of breathing not relieved with support,[32] or a trajectory that suggests that invasive ventilation is inevitable. Patients with high respiratory rate or effort in the setting of acute lung inflammation are at risk of exacerbating the acute lung injury by means of hyperventilation or high transpulmonary pressures, termed "patient self-inflicted lung injury" (P-SILI).[33,34] Furthermore, if NRS does not reduce respiratory effort, patients may fatigue[32] and/or deteriorate precipitously. In such circumstances, patients should be intubated and transitioned to invasive ventilation without delay. Although intubation is the preferred option for patients failing to meet targets on HFNO, it is acceptable to use NIV for patients with restricted resuscitation goals that preclude intubation.

After HFNO or CPAP initiation, patients may be encouraged to assume the prone position, particularly if the PaO2/FiO2 ratio is below 200. The suggestion for a trial of awake prone positioning during NRS is based on physiologic benefit[35] and extrapolation from non-COVID studies rather than proven clinical outcomes in COVID-19 patients. Ventilation in prone position reduces mortality in patients with ARDS receiving invasive mechanical ventilation[36,37] and improves oxygenation in awake, spontaneously breathing patients with moderate to severe ARDS receiving oxygen therapy by HFNO or NIV.[38,39] Although small case series of spontaneously breathing and NIV-assisted COVID-19 patients have recently described feasibility, tolerance and safety with improvement in oxygenation, larger randomized controlled trials are needed to determine if it improves outcomes.[40–43] In our experience, patients are able to pronate themselves but may need assistance adjusting their HFNO or NIV interface with turns. Although less complicated and labour-intensive than prone positioning in unconscious patients, potential risks and barriers include patient discomfort, nausea, increased leak from the interface, and nurse and respiratory therapist time to assist. If considered, prone positioning should be implemented early after hospital admission in patients fitting selection criteria (i.e., cooperative, able to protect airway, with low work of breathing).[44] Thoracic CT and ultrasound findings[45] in COVID-19 are varied, but prone positioning may best help those with dorsal lung region ground glass consolidation and/or atelectasis through more homogenous lung inflation and improved ventilation-perfusion matching (i.e., when dorsal regions become nondependent).[23] Encourage patients to accrue a total of 8 to 16 h per 24 h in the prone position, especially over the first 24–48 h. Ensure patients have access to oral suction, the means to contact the nurse (e.g., call bell, baby monitor), have continuous SpO2 monitoring and frequent assessment of respiratory rate and work of breathing. Aborting prone positioning in favour of intubation should not be delayed if failing HFNO/NIV.

The respiratory rate-oxygenation (ROX) index, developed to identify patients at high risk for needing intubation while on HFNO,[46] may help guide intubation decision-making.[45] The ROX index is calculated as:

Previously healthy patients with normal lung compliance and cardiac output are likely to tolerate a lower SpO2 without significant distress. A ROX index ≥ 4.88 is reassuring, and such patients can continue to be observed. Figure 1a shows the ROX index thresholds at various time points which should prompt a change in management and consideration of intubation. The trend in ROX index over time may be as indicative as the absolute value, as the ROX index should improve over time. While validated for use during HFNO,[46] the ROX index has not been studied for its predictive value in COVID-19 specifically and should not supplant clinical exam or clinical judgement. Furthermore, patients who develop acidosis, confusion, changes in mentation or are unable to manage their secretions should be intubated and invasively ventilated using a lung protective strategy.

Finally, patients undergoing NRS should be cared for in a monitored setting with well-trained staff accustomed to use and titration of these modalities (Figure 1b). At our institution, our Respirology Service (led by staff pulmonologist with resident house staff) or Critical Care Outreach Team (a Rapid Response Team led by staff intensivist with specially trained ICU registered nurse and registered respiratory therapist) must be consulted to manage all patients on NRS, with patients admitted to a Respiratory Unit, ward or ICU where bedside staff are appropriately trained. Both pre-COVID and COVID-19 experience support the association between admission to the appropriate setting with team expertise and better outcomes for NRS.[3,12]

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