Respiratory Management of COVID 19

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Introduction

There is currently no treatment recommended for corona virus infections except for supportive care as required, in particular respiratory management. Approximately 14% of individuals who are diagnosed with COVID-19 develop severe disease that requires hospitalization and oxygen support, with only  5% of those who require admission to an intensive care unit . In these severe cases of COVID-19, main complications include acute respiratory distress syndrome (ARDS), sepsis and septic shock, multiorgan failure, including acute kidney injury and cardiac injury, which are more prevalent in at risk groups including older age (>70 years) and those with co-morbid disease such as cardiovascular disease, lung disease, diabetes and those who are immunosuppressed. In a small proportion of these, the illness may be severe enough to lead to death. Data currently suggests that illness is less common and usually less severe in younger adults.

Clinical Syndromes Associated with COVID-19

Clinical Syndromes Associated with COVID-19

Mild Illness	Patients presents with uncomplicated upper respiratory tract viral infection and may have non-specific symptoms such as fever, fatigue, cough (with or without sputum production), anorexia, malaise, muscle pain, sore throat, dyspnea, nasal congestion, or headache. Rarely, patients may also present with diarrhoea, nausea, and vomiting. The elderly and immunosuppressed may present with atypical symptoms. Symptoms due to physiologic adaptations of pregnancy or adverse pregnancy events, such as dyspnea, fever, GI-symptoms or fatigue, may overlap with COVID- 19 Symptoms.
Pneumonia	Adult with pneumonia but no signs of severe pneumonia and no need for supplemental oxygen. Child with non-severe pneumonia who has cough or difficulty breathing + fast breathing: Fast Breathing (in breaths/min) and no signs of severe pneumonia. < 2 months ≥ 60; 2-11 months ≥ 50; 1-5 years ≥ 40, Patients may be productive, with an increased sputum load but this is a less common presentation.
Severe Pneumonia	Adolescent or Adult: Fever or suspected respiratory infection, plus one of the following: High Respiratory Rate > 30breaths/min; Severe Respiratory Distress; or SpO2 ≤ 93% on Room Air. Child with cough or difficulty in breathing, plus at least one of the following: Central Cyanosis or SpO2 < 90%; Severe Respiratory Distress (e.g. Grunting, Very Severe Chest Indrawing); Signs of Pneumonia with a general danger sign: Inability to breastfeed or drink Lethargy or Unconsciousness, or Convulsions. Other signs of pneumonia may be present: Chest Indrawing Fast Breathing (in breaths/min): < 2 months: ≥ 60; 2 - 11 months: ≥ 50; 1 - 5 years: ≥ 40. While the diagnosis is made on clinical grounds; chest imaging may identify or exclude some pulmonary complications.
Acute Respiratory Distress Syndrome (ARDS)	Onset: Within 5 - 7 days from the onset of initial respiratory symptoms Diagnostic Tools (Radiograph, CT Scan, or Lung Ultrasound): Bilateral Opacities, not fully explained by volume overload, lobar or lung collapse, or nodules. Origin of Pulmonary Infiltrates: Respiratory failure not fully explained by cardiac failure or fluid overload. Need Objective Assessment (e.g. Echocardiography) to exclude Hydrostatic cause of infiltrates/oedema if no risk factor present. Oxygenation Impairment in Adults: Based on PF Ratio, which is the ratio of arterial oxygen partial pressure to fractional inspired oxygen Mild ARDS: 200 mmHg < PaO2/FiO2a ≤ 300 mmHg (with PEEP or CPAP ≥ 5 cmH2O, Ornon-ventilated) Moderate ARDS: 100 mmHg < PaO2/FiO2 ≤ 200 mmHg (with PEEP ≥ 5 cmH2O, or Non-ventilated) Severe ARDS: PaO2/FiO2 ≤ 100 mmHg (with PEEP ≥ 5 cmH2O, or Non-ventilated) When PaO2 is not available, SpO2/FiO2 ≤ 315 suggests ARDS (including in Non-ventilated patients). Oxygenation Impairment in Children: Note OI = Oxygenation Index and OSI = Oxygenation Index using SpO2. Use PaO2-based metric when available. If PaO2 not available, wean FiO2 to maintain SpO2 ≤ 97% to calculate OSI or SpO2/FiO2 ratio: Bilevel (NIV or CPAP) ≥ 5 cmH2O via full face mask: PaO2/FiO2 ≤ 300 mmHg or SpO2/FiO2 ≤ 264 Mild ARDS (Invasively Ventilated): 4 ≤ OI < 8 or 5 ≤ OSI < 7.5 Moderate ARDS (Invasively Ventilated): 8 ≤ OI < 16 or 7.5 ≤ OSI < 12.3 Severe ARDS (Invasively Ventilated): OI ≥ 16 or OSI ≥ 12.3.
Sepsis	Adults: Life-threatening organ dysfunction caused by a dysregulated host response to suspected or proven infection. Signs of organ dysfunction include: Altered Mental Status Difficult or Fast Breathing Low Oxygen Saturation Reduced Urine Output Fast Heart Rate Weak Pulse Cold Extremities Low blood Pressure Skin Mottling Laboratory Evidence of Coagulopathy, Thrombocytopenia, Acidosis, High Lactate, or Hyperbilirubinemia. Children: Suspected or proven infection and ≥ 2 age- based systemic inflammatory response syndrome criteria, of which one must be abnormal temperature or white blood cell count.
Septic Shock	Adults: Persisting hypotension despite volume resuscitation, requiring vasopressors to maintain MAP MAP ≥ 65 mmHg and serum lactate level > 2 mmol/L. Children: Any hypotension (SBP < 5th centile or > 2 SD below normal for age) or two or three of the following: Altered mental state Tachycardia or Bradycardia HR < 90 bpm or > 160 bpm in Infants HR < 70 bpm or > 150 bpm in Children; Prolonged Capillary Refill (> 2 sec) or Feeble Pulse; Tachypnoea; Mottled or Cool Skin or Petechial or Purpuric Rash; Increased Lactate; Oliguria; Hyperthermia or Hypothermia

Patients with severe disease often need oxygenation support. High-flow oxygen and noninvasive positive pressure ventilation have been used, but the safety of these measures is uncertain, and they should be considered aerosol-generating procedures that warrant specific isolation precautions. Some patients may develop acute respiratory distress syndrome and warrant intubation with mechanical ventilation; extracorporeal membrane oxygenation may be indicated in patients with refractory hypoxia.

Procedures at Risk of Contamination

Particular attention should be given during those interventions that place the health staff at greater risk of contamination for aerial dispersion of droplets. (Rachael)

Aerosol Generating Procedures (AGP)

Aerosols generated by medical procedures are one route for the transmission of the COVID-19 virus. For patients with suspected/confirmed COVID-19, any of these potentially infectious AGPs should only be carried out when essential and minimised as much as possible. Where these procedures are indicated, they should be carried out in a single room with the doors shut, but preferably should be completed in a Negative Pressure Side Room. Only those healthcare staff who are needed to undertake the procedure should be present. Full PPE Equipment including a disposable, Fluid Repellent Surgical Gown, Gloves, Eye Protection and a FFP3 Respirator Mask should be worn by those undertaking the procedure and those in the room and good hand hygiene following the procedure. Hair cover should also be considered.

The following procedures are considered to be potentially infectious AGPs:

• Intubation, Extubation and Related Procedures;
• Tracheotomy/Tracheostomy Procedures;
• Manual Ventilation;
• Open Suctioning;
• Bronchoscopy;
• Non-Invasive Ventilation (NIV) e.g. Bi-level Positive Airway Pressure (BiPAP)and Continuous Positive Airway Pressure Ventilation (CPAP);
• Surgery and Post-Mortem Procedures in which high-speed devices are used;
• High-Frequency Oscillating Ventilation (HFOV);
• High-flow Nasal Oxygen (HFNO)
• Induction of Sputum; Note:Induction of sputum typically involves administration of nebulised saline to moisten and loosen respiratory secretions (this may be accompanied by chest physiotherapy such as percussion and vibration to induce forceful coughing. This may be required if lower respiratory tract samples are needed

Certain other procedures/equipment may generate an aerosol from material other than patient secretions but are not considered to represent a significant infectious risk. Procedures in this category include:

• Administration of Pressurised Humidified Oxygen;
• Administration of Medication via Nebulisation; Note: During nebulisation, the aerosol derives from a non-patient source (the fluid in the nebuliser chamber) and does not carry patient-derived viral particles. If a particle in the aerosol coalesces with a contaminated mucous membrane, it will cease to be airborne and therefore will not be part of an aerosol. Staff should use appropriate hand hygiene when helping patients to remove nebulisers and oxygen masks.

Physiotherapy Specific Aerosol Generating Techniques:

• Manual Techniques (e.g. Percussion/Manual Assisted Cough) that may lead to coughing and expectoration of sputum
• Use of Positive Pressure Breathing Devices (e.g. IPPB), Mechanical Insufflation-Exsufflation (Cough Assist) Devices, Intra/Extra Pulmonary High Frequency Oscillation Devices (e.g. the Vest / MetaNeb / Percussionaire etc.)
• Any Mobilisation or Therapy that may result in Coughing and Expectoration of Mucus
• Any Diagnostic Interventions that involve use of Video Laryngoscopy that can result in Airway Irritation and Coughing (e.g. Direct Visualisation during airway clearance techniques or when assisting Speech and Language Therapists perform Fibreoptic Endoscopic Evaluation of Swallow)

Decontamination

• Reusable (communal) non-invasive equipment must be decontaminated:
• between each patient and after patient use;
• after blood and body fluid contamination; and
• at regular intervals as part of equipment cleaning.

An increased frequency of decontamination should be considered for reusable non- invasive care equipment when used in isolation/cohort areas.

Equipment

• Reusable equipment should be avoided if possible; if used, it should be decontaminated according to the manufacturer’s instructions before removal from the room. If it is not possible to leave equipment inside a room then follow IPC Guidelines on Decontamination. This usually involves cleaning with neutral detergent, then a chlorine-based disinfectant, in the form of a solution at a minimum strength of 1,000ppm available chlorine (e.g. “Haz-Tab” or other brand).
• If possible use dedicated equipment in the isolation room. Avoid storing any extraneous equipment in the patient’s room
• Dispose of single use equipment as per clinical waste policy inside room
• Point of care tests, including blood gas analysis, should be avoided unless a local risk assessment has been completed and shows it can be undertaken safely
• Ventilators and mechanical devices (e.g. Cough Assist Machines) should be protected with a high efficiency viral-bacterial filter such as BS EN 13328-1.
• When using mechanical airway clearance filters should be placed at the machine end and the mask end before any expiratory or exhalation ports. Filters should be changed when visibly soiled or dependent on the filter used either after each use or every 24 hours and complete circuit changes should be undertaken every 72 hours (please follow trust guidance on this)
• Closed system suction should be used if patients are intubated or have tracheostomies
• Disconnecting a patient from mechanical ventilation should be avoided at all costs but if required the ventilator should be placed on standby
• Manual hyperinflation (bagging) should be avoided if possible and attempt ventilator recruitment manoeuvres where possible and required
• Water humidification should be avoided, and a heat and moisture exchanger should be used in ventilator circuits
• Disposable crockery and cutlery may be used in the patient’s room as far as possible to minimise the numbers of items which need to be decontaminated
• Any additional items such as Stethoscopes, Pulse Oximeters, Ultrasound Probes taken into a room will also need to be disinfected, regardless of whether there has been direct contact with the patient or not. This is due to the risk of environmental contamination of the equipment within the isolation room.

Patients Rooms

• If AGPs are undertaken in the patient’s own room, the room should be decontaminated 20 minutes after the procedure has ended (please follow trust IPC guidance on this also).
• If a different room is used for a procedure it should be left for 20 minutes, then cleaned and disinfected before being put back into use.
• Clearance of any aerosols is dependent on the ventilation of the room. In hospitals, rooms commonly have 12 to 15 air changes per hour, and so after about 20 minutes, there would be less than 1 per cent of the starting level (assuming cessation of aerosol generation).
• If it is known locally that the design or construction of a room may not be typical for a clinical space, or that there are fewer air changes per hour, then the local IPCT would advise on how long to leave a room before decontamination.

Oxygen Support

Give supplemental oxygen therapy immediately to patients with SARI and respiratory distress, hypoxaemia or shock and target SpO2 > 94%.

Patients may continue to have increased work of breathing or hypoxemia even when oxygen is delivered via a face mask with reservoir bag (flow rates of 10 - 15 L/min, which is typically the minimum flow required to maintain bag inflation; FiO2 0.60–0.95). Hypoxemic respiratory failure in ARDS commonly results from intrapulmonary ventilation-perfusion mismatch or shunt and usually requires mechanical ventilation.

Early recognition and referral of patients with worsening respiratory function while on conventional oxygen therapies such as simple face masks or masks with reservoir bags is important to ensure timely and safe escalation of respiratory support. Early optimisation of care and involvement of ICU is recommended. The following can be considered in caring for COVID-19 patients in ICU if required prior to invasive ventilation:

High Flow Nasal Oxygen (HFNO) Therapy (in ICU):

As long as staff are wearing optimal airborne PPE, HFNO is a recommended therapy for hypoxia associated with COVID-19 disease. The risk of airborne transmission to staff is low with well fitted newer HFNO systems when optimal PPE and other infection control precautions are being used. Negative pressure rooms are preferable for patients receiving HFNO therapy. Patients with worsening hypercapnia, acidaemia, respiratory fatigue, haemodynamic instability or those with altered mental status should be considered for early invasive mechanical ventilation if appropriate.

Ventilatory Support

Acute or chronic hypoxaemia is a common reason for admission to intensive care and for provision of mechanical ventilation. Various refinements of mechanical ventilation or adjuncts are employed to improve patient outcomes.

Non-Invasive Ventilation (NIV)

Routine use of non-invasive ventilation is not recommended.

Although non-invasive ventilation may temporarily improve oxygenation and reduce the work of breathing in patients with viral infections complicated by pneumonia this method does not necessarily change the natural disease course and as such NIV is not routinely recommended. Current experience suggests that NIV for COVID-19 hypoxic respiratory failure is associated with a high failure rate, delayed intubation, and possibly increased risk of aerosolization with poor mask fit. It seems clear from the available evidence that NIV and HFNO should not be routinely used when the patient has severe respiratory failure, or a trajectory that suggests that invasive ventilation is inevitable. In such circumstances, deteriorating patients should be considered for early endotracheal intubation and transitioned from oxygen therapy via a simple facemask to invasive ventilation without delay.

If NIV is appropriate for an alternate clinical presentation of COVID-19 (e.g. concomitant COPD, APO), this should be provided using similar precautions as for HFNO. Negative pressure single rooms are preferable for patients receiving NIV. For all patients receiving NIV determine a clear plan for treatment failure. 

In Italy where NIV has been used they recommend to perform a single attempt of up to 1 Hour.  If you don't see substantial improvements, alert the medical team, as the patient should be considered for early endotracheal intubation and invasive ventilation.

To minimize the risk of airolising infected material, in Italy they suggest the safest interface to use is the hood or helmet. In relation to face mask choice, it is preferable to combine a double circuit with an exhalation valve. If necessary to combine the face mask with a single circuit, use a version equipped with a built-in exhalation port breath valve and not exhalation port, as well as the installed antimicrobial filter.

HUMIDIFICATION It is advisable to use a double-c fanin non-invasive mode, with an active heated humidifier (HH).

ANTIMICROBIAL FILTERS: Evaluate positioning depending on the ventilation setting and IPR available to staff. Position the filters so that they can protect the patient and ventilator (if necessary), as well as limit the dispersion of exhaled air into the surrounding environment.

Invasive

Lung protective mechanical ventilation (MV) is recommended for management of acute respiratory failure.

Mechanical ventilation should be employed with the use of a low tidal volume strategy (4-8ml/kg predicted body weight) and limiting plateau pressures to less than 30 cmH2O. Permissive hypercapnia is usually well tolerated and may reduce volutrauma. Higher levels of PEEP, greater than 15 cmH2O, are recommended.

Alternate modes of ventilation such as APRV may be considered based on clinician preference and local experience. Viral, rather than HME filters, should be utilised, and circuits should be maintained for as long as allowable (as opposed to routine changes).

Weaning and Liberation from Mechanical Ventilation

Standard weaning protocols should be followed. HFNO and/or NIV with well fitted facemask with separate inspiratory and expiratory limbs, can be considered as bridging therapy post-extubation but must be provided with strict airborne PPE.

Positioning

Prone ventilation is ventilation that is delivered with the patient lying in the prone position. Prone ventilation may improve lung mechanics and gas exchange, thus improving oxygenation in the majority of patients with ARDS, and could improve outcomes. Current reports suggest prone ventilation is effective in improving hypoxia associated with COVID-19 and should be completed in the context of a hospital guideline that includes appropriate PPE for staff, and that minimise the risk of any adverse events, e.g. accidental extubation.

https://youtu.be/bE4mmGdjA5I?list=PLpClorbJ0-261TRyh3nH9r7xdP3ri8wCz

Suctioning

Closed inline suction catheters are recommended. Any disconnection of the patient from the ventilator should be avoided to prevent lung decruitment and aerosolization. If necessary, the endotracheal tube should be clamped and the ventilator disabled (to prevent aerosolization).

Nebulisation

Use of nebulisers is not recommended and use of metered dose inhalers are preferred where possible.

Prevention of Complications (WHO)

Reduced Days of Mechanical Ventilation:

●       Use weaning protocols that provide for the daily assessment of the spontaneous breathing capacity.

Reduce the Incidence of Ventilator-Associated Pneumonia

• Keep the patient in a semi-sitting position (30 - 45 degrees);
• Use a closed Suction System; Periodically Drain and Discard Condensate In Tubing;
• Use a new ventilation circuit for each patient, once the patient is ventilated change the circuit only if it is damaged or soiled, not routinely;
• Change Heat Moisture Exchanger when it malfunctions, when soiled, or every 5-7 days

Reduce the Incidence of Pressure Ulcers

• Turn Patient every 2 Hours

Reduce the Incidence of Intensive Care-Related Myopathy

• Mobilize the patient as soon as their condition allows and when safe to do so.

Resources

World Health Organisation

This document is intended for clinicians taking care of hospitalised adult and paediatric patients with severe acute respiratory infection (SARI) when a nCoV infection is suspected. It is not meant to replace clinical judgment or specialist consultation but rather to strengthen clinical management of these patients and provide to up-to-date guidance. Best practices for severe acute respiratory infection including Infection Prevention and Control and optimized supportive care for severely ill patients are essential.

• Clinical management of Severe Acute Respiratory Infection when Novel Coronavirus (nCoV) Infection is suspected

References