Ventilation Considerations & Management

#### Ventilation Considerations

- Position with head of bed elevated, self-proning of non-ventilated conscious patients may improve ventilation and secretion management. Awake self-proning with high flow nasal cannula or nonrebreather may delay/prevent intubation.
- Sp02 goal 92% if conservation needed for oxygen supplies. Use surgical face mask over prongs/nonrebreather if possible. However, prone positioning poorly tolerated, DO NOT force position.
- Initiate lung-protective ventilation strategy for those requiring mechanical ventilation. Use the ARDSnet LOW PEEP table.
- Ventilate with tidal volume 4-6mL/kg ideal body weight (IBW) keeping plateau pressure (Plat) < 30mmH2O as goal
- Maintain OSpO2 88-92% or PaO2 55-80mmHg (Note: ARDSNet recommends SpO2 upper limit of 95%; targeting 92% is reasonable to extend oxygen supplies)
- Permissive hypercarbia (arterial pH > 7.20, venous pH >7.15)
- If ETT must be disconnected from the ventilator for ANY reason, clamp the ETT to prevent decruitment and minimize aerosolization of the virus.
- If in-line suction devices are not available, de-recruitment will likely occur with suctioning. Salvage recruitment maneuvers may be necessary.

COVID-19 Ventilator Selection Guide
COVID-19 Ventilator Selection

#### EMV+731 (mode AC-V) Recruitment Maneuver

1. Change upper limit of Peak Inspiratory Pressure (PIP) alarm to 50cmH20;
2. Decrease tidal volume as low as possible (50mL);
3. Increase PEEP to 30-40cmH20;
4. Hold for 40 seconds (if signs of hemodynamic instability develop, stop the recruitment maneuver, and resume prior settings);
5. Increase PEEP to 2cmH20 ABOVE prior PEEP setting;
6. Increase tidal volume back to prior setting;
7. Return upper limit of PIP alarm to prior setting;
8. Monitor hemodynamic instability or high PIP, indicates possible pneumothorax.

#### Oxygenation

1. Escalate PEEP to 14cmH20 as aggressively as possible as hemodynamics allow to optimize oxygenation, minimize FiO2 needs, and extend oxygen supply.
2. Use the ARDSNet Protocol LOW PEEP table as a guide for further titration of PEEP.
3. Be prepared to start vasopressors and extremely judicious use of IVF to support pre-load in the face of high PEEP (aka PEEP tamponade).
4. Consider a combination of paralysis and prone positioning early to lengthen duration of available oxygen supply.
5. Consider Inverse Ration Ventilation (IRV) once patient reaches PEEP 18cmH20 on the LOW PEEP table.

#### Manage Ventilation

- EtCO2 goal is 35mmHg +/- 5. Obtain ABG if available (iStat), obtain baseline PCO2, correlate with EtCO2. Note: (EtCO2 of 40 may actually represent PCO2 of 60 with a 7.24 pH in pulmonary disease.)
- Manual breath button on the bottom left of EMV+731 & allows for manual measurement of plateau pressure (Pplat). The Pplat goal is less than 30cmH2O. In the absence of Pplat, a PIP target of less than 35cmH20 is desired.
- If Pplat is greater than 30cmH20, decrease set tidal volume by 1 mL/kg steps (generally about 50-80 mL). Titrate set respiratory rate (RR) up increments of 2 bpm to maintain pH and EtCO2 at goal. Avoid RR above 30 bpm given significant risk for breath stacking and auto PEEP.
- Consider serial blood gas evaluation via iStat (adjusting frequency to patient stability).

#### Secretion Management

- Increased secretions & mucous plugging are extremely common causes for increased oxygen requirement, difficulty with ventilation, and respiratory failure.
- Secretions are heavier than usual. Use in-line suction (closed system), which minimizes aerosolization and de-recruitment, but not often available in austere settings.
- Use heated humidification to prevent drying out of secretions and promotes sputum clearance.
- Heated-humidification devices are equipment designed to be used along with ventilators (e.g. Hamilton H900).
- Heat-Moisture Exchangers (HME) are supplies that fit in-line with the ventilator tubing and trap heat and moisture within the circuit.
- Heat-Moisture Exchange Filters (HME-F) are supplies that fit in-line with the ventilator tubing and provide HME and microbiologic filtration.

#### Mucolytics

- Pre-treat with albuterol and/or ipratropium for 10-15 minutes
- 20% N-acetylcystine (Mucomyst) as 1-2mL direct instillation into ETT every 6 hours as needed for secretion control
- 3% Saline (Hypertonic Saline) as 5mL direct instillation into the ETT every 12 hours as needed for secretion control
- Use bronchodialators with caution. Albuterol and ipratropium effectively dry up secretions but they may increase mucous plugging.
- Anti-Sialagogues not routinely recommended for COVID-19 patients.

#### Adjunctive Strategies for ARDS

There is no single strategy recommended for management of severe ARDS. Many interventions are due to resource constraints within austere environments. If unfamiliar with these techniques, obtain teleconsultation guidance.

#### Pressure Control - Inverse Ratio Ventilation (PC-IRV)

- As more of the breath cycle will be spent in inspiration, ventilation may worsen with a transition to PC-IRV.
- EMV+731 with the most recent software package has the capability to do PC-IRV. While using AC-P mode, PC-IRV is achieved by increasing the I:E ratio above 1:2 (i.e. 1:1, 2:1, 3:1 and higher).
- PC-IRV cannot fully approximate Airway Pressure Release Ventilation (APRV), but is still the best available salvage mode using EMV+731.
- Once PEEP is maximized (or limited by peak inspiratory pressure) and oxygenation is still not yet at goal, increase the I:E ratio incrementally.
- Tidal volume goals remain the same as with conventional ventilation; adjust cycle time (60/RR) to optimize minute ventilation.
- As higher I:E ratios are non-physiologic, PC-IRV may require increased sedation for patient comfort and synchrony.