Invasive Mechanical Ventilation

Patients With or Under Investigation for COVID-19

                                                                                             

Background

  • Mechanical ventilation is required up to 10% of all patients with COVID-19. The ARDS picture of COVID-19 is unique. Many patients will present with “silent hypoxemia”; i.e. degree of hypoxemia is out of proportion to lung compliance. Because lung compliance is relatively preserved, the work of breathing may initially appear normal.

  • In patients on nasal cannula, keeping SpO2 90 – 92% will facilitate early detection of worsening oxygenation, since oxyhemoglobin curve is steepest in this range

 

Indications

  • Acute hypoxemic respiratory failure requiring > 6 L/min nasal cannula

  • Acute hypercarbic respiratory failure

  • Other conventional indications for mechanical ventilation

 

Contraindications

  • Absolute: DNI

  • Relative: None

 

Team & Equipment

  • Respiratory Therapist

  • CCRN

  • Staff Intensivist

  • Ventilator 

 

PPE

  • ACE for aerosol-generative procedures

  • Whenever possible, the ventilator controller/servo should be detached from the machine manifold and placed outside of the patient room (see photo below). This reduces entry/re-entry and utilization of PPE for routine ventilator management.












 

 

 

 

Lung-Protective Ventilation

  • All patients should receive mechanical ventilation with non-injurious tidal volumes (≤ 6 cc/kg ideal body weight) according to existing NIH ARDSNet protocols, using the High PEEP ladder (see below)

  • Patients with COVID-19-ARDS appear to have a prompt and sustained response to PEEP, indicating the alveoli may be partially drowned but durably recruitable if an “open lung” approach of high PEEP is initiated early

  • Checklist for Lung Protection (best outcomes when all 4 are met)

    • VT ≤ 6 cc/kg IBW

    • Plateau pressure ≤ 30

    • Driving pressure (Pplat – PEEP) ≤ 18

    • Minimal or no asynchrony  

  • Staff intensivist will prescribe and actively manage ventilator settings to achieve desired clinical and physiologic outcomes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Special Considerations

 

  • ARDS with superimposed expiratory airflow limitation (asthma, COPD, CF)

    • Lung protective ventilation remains the priority

    • Higher risk of global overdistention/barotrauma due to incomplete lung emptying. Higher risk of regional overdistention/barotrauma due to heterogeneous lung emptying

    • Attention to expiratory waveform and periodic assessment for auto-PEEP

    • See protocol for Respiratory Treatment: Bronchodilators (Section ##). In general, bronchodilator treatments should be given as metered dose inhaler (MDI) puffs delivered in-line with the ventilator to minimize aerosolization. In some cases of severe bronchospasm, intravenous bronchodilators may be used.

    • Corticosteroids generally avoided for COVID-19-ARDS, but may be used in cases of acute, severe, and reversible airflow limitation

 

  • ARDS with acute cor pulmonale (ACP)

    • ACP = acute right ventricular failure due to hypoxemic lung disease

    • Clues pointing to ACP: hemodynamic dysfunction with evidence of LV underfilling (high pulse pressure variation), high dead space fraction (wide discrepancy between etCO2 and pCO2), TTE shows RV dilatation

    • ACP occurs in 20% of ARDS cases and requires specific RV protective priorities. Failure to unload the RV is independently associated with mortality.

    • RV protective ventilation checklist

      • Keep pCO2 ≤ 48 (respiratory acidosis causes pulmonary vasoconstriction)

      • Decreased alveolar distending pressure (keep Pplat < 27) by lowering VT or PEEP

      • Decrease hypoxic pulmonary vasoconstriction

    • These patients will most likely improve with proning (see Prone Ventilation protocol)

 

  • ARDS with severe refractory hypoxemia

    • Severe hypoxemia is usually due to lung derecruitment owing to worsening ARDS. However, a significant fraction of patients with COVID-19 may have hypoxemia due to decreased lung perfusion in the setting of cardiogenic shock or acute cor pulmonale.

      • Limited TTE (can be at point of care) to evaluate cardiac function

    • Prone Ventilation

      • Initiate when P/F < 150 on FIO2 = 60% and PEEP = 10

      • Follow Prone Ventilation protocol (here) for further guidance

    • Airway Pressure Release Ventilation (APRV)

      • Initial settings – PHigh = 30, THigh = 5 sec, PLow = 0, PLow = 0 - 1 sec

      • Staff intensivist will prescribe and titrate APRV settings

      • Follow APRV protocol (here) for further guidance

    • Referral for ECMO if possible ​

 

Prophylaxis

  • Nutrition: early enteric trophic feeding with escalation as tolerated

  • Peptic Ulcer Disease: H2 receptor antagonist

  • VAP: AVAMC ICU VAP bundle

    • Daily sedation holiday and weaning assessment as soon as feasible

    • Oral hygiene with chlorhexidine q4 hours

    • HOB > 30°

    • Continuous aspiration of subglottic secretions (CASS) if available

  • DVT: AVAMC ICU standard thromboprophylaxis

    • Low dose unfractionated heparins (LDUH) q8 – q12 hours OR

    • Low dose low molecular weight heparins (LMWH) q24 hours OR

    • Fondaparinux

    • SCD if excessive bleeding risk precludes anticoagulation

Detached and externalized ventilator display/servo

High PEEP ladder and ARDSNet protocol

Information presented on this website does not reflect the views or positions of the US Veterans Health Administration, Emory Healthcare, or its affiliated institutions. This is a rapidly evolving field. As such. the content on this site is being updated daily and protocols will be updated in real time.  The purpose of this site is to provide a centralized resource for ICU topics and protocols to promote the well-being of hospitalized or critically ill patients suffering from COVID-19.  Defer to your institutional guidelines for all clinical practice decisions.

 

© 2020  Victor Tseng, MD