Dr K K Aggarwal
President Confederation of Medical Associations of Asia and Oceania,
HCFI and Past National President IMA
With regular inputs from Dr Monica Vasudev
Specific aspects of respiratory care relevant to deteriorating patients with COVID-19 before admission to the intensive care unit (ICU) include oxygenation with low flow and high-flow systems, noninvasive ventilation and the administration of nebulized medications.
688: How many will require oxygen
Data from Wuhan, China, show that more
than a third of patients with this infection (41.3%) will require oxygen and
more than 1 in 20 (6.1%) will require mechanical ventilation. A somewhat
smaller portion (3.4%) will develop acute respiratory distress syndrome (ARDS).
689: What should be ideal oxygen levels : SPO2 94-98%
In 2016 the Oxygen-ICU randomized clinical trial reported an improvement in outcomes with a conservative oxygen strategy. That strategy targeted a PaO2 of 70-100 mm Hg, or an arterial oxyhemoglobin saturation (SpO2) between 94% and 98%. The comparison group targeted a more liberal goal of an SpO2 of 97%-100%.
The authors concluded that the conservative protocol resulted in lower ICU mortality. As a result, guidelines developed by an international panel of experts updated their oxygen targets. A 2018 systematic review and meta-analysis more or less confirmed the benefits of a more conservative oxygen strategy.
690: What about other trials
In March 2020, two new randomized clinical trials examining oxygen therapy were published in the New England Journal of Medicine. A large retrospective study was published in CHEST in late 2019. Each analyzed oxygen targets in the critically ill. The first found no difference in a conservative versus liberal approach, the second found potential harm with the conservative approach, and the third reported that an oxygen saturation range of 94%-98% was optimal.
691: What is the current consensus
First, an oxygen saturation target as low as SpO2 88% is probably contraindicated, particularly for patients with moderate to severe ARDS.
Limiting SpO2 to below 96%. This certainly seems safe and it may still prove to be beneficial.
692: What are the recommendations in COVID 19
Experts have issued guidelines for the management of critically ill patients with the disease. They recommend starting oxygen at a SpO2 of 90% and maintaining it no higher than 96%. Essentially, this is a target of 90%-96%. Setting a lower limit of 92% gives you a little breathing room.
693: What Silent hypoxemia
It is being described in many of these COVID patients. That means the patient is very hypoxemic—they may have an oxygen saturation of about 85% on room air, but clinically they look very comfortable—they are not dyspneic or tachypneic and may not even verbalize a significant sense of shortness of breath.
It's not every patient, but it has been interesting to see patients sitting there looking fairly normal, with a resting oxygen saturation much lower than you would expect for someone who doesn't have an underlying pulmonary disease or other symptoms.
694: what are the equipment required for Escalation of O2 Therapy
Starting with patients with O2 sat <90%
Goal should be to maintain O2 sat > 90-96%
NC 1 – 6LPM + Surgical Mask
Venti Mask
NRB + NC
HFNC + Surgical Mask
NIV (i.e. CPAP)
695: If SPO2 < 90%
Low flow oxygen — For patients with COVID-19, supplemental oxygenation with a low flow system via nasal cannula is appropriate ( up to 6 L/min). Although the degree of micro-organism aerosolization at low flow rates is unknown, it is reasonable to surmise that it is minimal. So, start with nasal canula at 6 L/ minute.
As demand increases higher flows of oxygen may be administered using a simple face mask, venturi face mask, or non-rebreather mask (up to 10 to 20 L/minute), but as flow increases, the risk of dispersion also increases, augmenting the contamination of the surrounding environment and staff.
Some experts have suggested having patients who wear nasal cannula wear a droplet mask (during transport to protect spread to the surrounding environment).
696: What if it fails
1. NPPV: FIO@ always
at 100%, EPAP set to 5, Ensure the viral filter is connected, perform in negative pressure
room
2. HFNC: FIO2 always at 100%, start at 20 l/mt,
Goal SPO2 > 88%, Preferred over NPPV. This is for patients with higher
oxygen requirements — As patients progress, higher amounts of oxygen are
needed. Options at this point in non-COVID-19 patients are high-flow oxygen via
nasal cannulae (HFNC) or the initiation of noninvasive ventilation (NIVor NPPV).
In retrospective cohorts, rates for HFNC use ranged from 14 to 63 percent while
11 to 56 percent were treated with NIV.
.
697: What next
Proning, buys time, change position every hour
698: What next
Intubate and transfer
699: when to transfer to ICU
For hospitalized patients who develop progressive symptoms, early admission to the ICU is prudent when feasible. The hospitalized patient spends as much time as is feasible and safe in a prone position while receiving oxygen.
700: What are Oxygenation targets
The World Health Organization (WHO) suggests titrating oxygen to a target peripheral oxygen saturation (SpO2) of ≥90 percent.
For most critically ill patients prefer the lowest possible fraction of inspired oxygen (FiO2) necessary to meet oxygenation goals, ideally targeting a SpO2 between 90 and 96 percent, if feasible.
701: Which patients require lower targets of SPO2
Some patients may warrant a lower target ( patients with a concomitant acute hypercapnic respiratory failure from chronic obstructive pulmonary disease [COPD]) and others may warrant a higher target (eg, pregnancy).
702: NIV or intubation
In patients with COVID-19 who have acute hypoxemic respiratory failure and higher oxygen needs than low flow oxygen can provide, noninvasive modalities may be used selectively rather than proceeding directly to intubation (eg, a younger patient without comorbidities who can tolerate nasal cannulae). On the other hand, some patients may warrant avoidance of HFNC and may benefit from proceeding directly to early intubation (eg, elderly or confused patient with comorbidities and several risk factors for progression).
703: Can we avoid both modalities HFNC or NIV and proceeding to early intubation if escalating beyond 6 L/min with continued hypoxemia or increased work of breathing).
This is predicated on an increased risk of aerosolization and high likelihood that patients who need these modalities will ultimately, rapidly deteriorate and require mechanical ventilation (eg, within one to three days). This approach may be reasonable when resources are available. However, using this as an absolute rule may result in an excess of unnecessary intubations and place an undue load on ventilator demand as the disease surges. In addition, this is particularly problematic for patients under investigation (eg, COVID-19 testing pending), patients who have chronic nocturnal NIV requirements, patients with chronic respiratory failure who have high baseline oxygen requirements, and patients with do-not-intubate status but who might benefit otherwise from NIV or HFNC.
704: What about Nebulized medications (spontaneously breathing patients)
Nebulizers are associated with aerosolization and potentially increase the risk of SARS-CoV-2 transmission. In patients with suspected or documented COVID-19, nebulized bronchodilator therapy should be reserved for acute bronchospasm (eg, in the setting of asthma or chronic obstructive pulmonary disease [COPD] exacerbation). Otherwise, nebulized therapy should generally be avoided, in particular for indications without a clear evidence-base; however some uses (eg, hypertonic saline for cystic fibrosis) may need to be individualized.
705: What to use
Metered dose inhalers (MDIs) with spacer devices should be used instead of nebulizers for management of chronic conditions (eg, asthma or COPD controller therapy).
706: If nebuliser is necessary
If nebulized therapy is used, patients should be in an airborne infection isolation room, and healthcare workers should use contact and airborne precautions with appropriate personal protection equipment (PPE); this includes a N95 mask with goggles and face shield or equivalent (eg, powered air-purifying respirator [PAPR] mask]) as well as gloves and gown.
All non-essential personnel should leave the room during nebulization. Some experts also
707 : what needs to be avoided
•Positive airway devices for chronic nocturnal ventilation support
•Chest physical therapy or oscillatory devices
•Oral or airway suctioning
●Sputum induction should be avoided
●Bronchoscopy should be avoided in spontaneously breathing patients and limited to therapeutic indications (eg, life-threatening hemoptysis, central airway stenosis)
If any of these therapies are performed, similar PPE to that described for nebulizer therapy should be used.
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