We talk about evidences on respiratory support in the dyspneic and moderately/severe hypoxic suspect COVID-19 patient on the field. Clinical evidences and contamination risks in the potentially infected COV 19 patients to guide our efforts toward a good outcome when the conventional O2 therapy is not enough.
Clinical characteristics and imaging manifestations of the 2019 novel coronavirus disease (COVID-19):A multi-center study in Wenzhou city, Zhejiang, China
The imaging pattern of multifocal peripheral ground glass or mixed opacity with predominance in the lower lung is highly suspicious of COVID-19 in the first week of disease onset.
Not much of that. NIV in SARS and MERS epidemic demonstrated a poor outcome over invasive mechanical ventilation and possible delay effect on tracheal intubation and mechanical ventilation.
Noninvasive ventilation in critically ill patients with the Middle East respiratory syndrome. Basem M. Alraddadi et al. Influenza Other Respi Viruses. 2019;13:382–390
The vast majority (92.4%) of patients who were managed initially with NIV re‐ quired intubation and invasive mechanical ventilation, and were more likely to require inhaled nitric oxide compared to those who were managed initially with invasive MV. ICU and hospital length of stay were similar between NIV patients and invasive MV patients. The use of NIV was not independently associated with 90‐day mortality (propensity score‐adjusted odds ratio 0.61, 95% CI [0.23, 1.60] P = 0.27).
DSC Hui, MTV Chan, B Chow. Aerosol dispersion during various respiratory therapies: a risk assessment model of nosocomial infection to health care workers. Hong Kong Med J 2014;20(Suppl 4):S9-13
When inspiratory positive airway pressure (IPAP) increased from 10 to 18 cmH2O, the exhaled air of a low normalised concentration through the ComfortFull 2 mask increased from 0.65 to 0.85 m at a direction perpendicular to the head of the HPS along the median sagittal plane. In contrast, when an IPAP of 10 cmH2O was applied via the Image 3 mask connected to the whisper swivel exhalation port, the exhaled air dispersed to 0.95 m towards the end of the bed along the median sagittal plane, whereas a higher IPAP resulted in wider spread of a higher concentration of smoke (….) It is also important to avoid the use of higher IPAP, which could lead to wider distribution of exhaled air and substantial room contamination.
When high flow conventional O2 therapy is not enough to reach clinical goals in the highly risk patient, non otherwise transportable and at risk of rapidly loosing airway patency One level PEEP respiratory support (CPAP) is the best compromise between clinical efficacy and contamination risk.
Ventilatory inspiratory support (BiPAP) doesn’t add much from a clinical point of view and increase the risk of contamination so has to be avoided.
The generic dyspneic patients do not pose any particular self protection issues above the general precautions
Non infected dyspneic patient need moderately high FiO2 but considerately high oxygen flow rates.
The available systems we have in this moment (at least on my operative setting) to deliver normally pressured O2 are:
To satisfy the increased minute ventilation of the highly dyspneic patient Venturi mask is the best device (high flow rate) and permits at the same time to tritrate the FiO2 based on the patients need avoiding indiscriminate hyperoxygenation.
The following considerations derived from our initial experience on the field in suspect or confirmed COVID-19 with respiratory symptoms at their presentation or in the initial phases. Those are the majority of the patients we observed till the day this post was written.
The following considerations are not intended for all the severe hypoxic patients who definitively need early intubation and positive pressure ventilation.
Those are dyspneic hypoxic patients who needs moderately high FiO2 and request more gas flow rates to satisfy increased minute ventilation.
So from an exclusively clinical point of view the best way to deliver oxygen it would be a Venturi mask.
In the actual situation in Italy the epidemiological geographical criteria is no more reliable to identify COVID-19 patients so any prehospital healthcare professional providing direct care to a dyspneic patient needs to be protected al least with:
At the same time good practice is to reduce at minimum the number of direct caring providers, to maintain, if possible, a security distance > 1 mt, to invite any patient to wear, if tolerated, a surgical mask, and a pair of disposable gloves to minimise the risk of infection.
When providing direct care of dyspneic patients who needs O2 therapy the level of risk for droplet diffusion is generally increased cause of the presence of the gas flow.
All the available systems for oxygen delivery we mentioned above are open and allow a free exaltation of the patient in the surrounding area and potentially exposes all the healthcare caregivers to an increased risk of contamination cause of the augmented droplet dispersion and to a lack of protection.
So when dealing with O2 therapy in the potentially infected patients we need to consider the relationship between risk of contamination and clinical efficacy of any device.
Nasal Cannula is the only device that permits the patient to wear a surgical mask on nose and mouth, decreasing droplet diffusion and protecting the healthcare team and at the same time maintains a certain clinical efficacy..
So my first approach is Nasal Cannula underneath a medical mask.
Utilising a different device than nasal cannula plus medical mask on the patient mouth and nose (simple, non rebreather or Venturi face mask) to deliver oxygen therapy all healthcare professionals need to be aware that the risk infection increases and the patient has no barriers and so they have to consider improving his own self protection level (N95, FPP2 mask at least)
When you can’t reach a clinical acceptable SpO2 with nasal cannula we need to downgrade on our first goal (protection) to achieve a better clinical outcome.
Simple facial masks maintain a moderate protection form droplet spreading with a more clinical efficacy respect th the nasal cannula.
Nonrebreather facial mask either moderately protects against droplet diffusion with an improvement in FiO2 above simple face mask but the nonrebreather bag is a potential expirate gas reservoir potentially increasing the risk of spreading.
High flow titratable FiO2 in an open system mask can satisfy all minute ventilation needing guaranteeing Oxygenation at a cost of a great risk of spreading. My last choice in the scale of conventional Oxygen therapy.
References:
DSC Hui, MTV Chan, B Chow. Aerosol dispersion during various respiratory therapies: a risk assessment model of nosocomial infection to health care workers. Hong Kong Med J 2014;20(Suppl 4):S9-13
M. P. Wan , C. Y. H. Chao , Y. D. Ng , G. N. Sze To & W. C. Yu (2007) Dispersion of Expiratory Droplets in a General Hospital Ward with Ceiling Mixing Type Mechanical Ventilation System, Aerosol Science and Technology, 41:3, 244-258, DOI: 10.1080/02786820601146985
Shu-An Lee, Dong-Chir Hwang, He-Yi Li, Chieh-Fu Tsai, Chun-Wan Chen,and Jen-Kun Chen. Particle Size-Selective Assessment of Protection of
European Standard FFP Respirators and Surgical Masks against Particles-Tested with Human Subjects. Journal of Healthcare Engineering. Volume 2016, Article ID 8572493, 12 pages
Thanks for reviewing and suggesting to: Scott Weingart, Jim DuCanto, Velia Marta Antonini, Giacomo Magagnotti, Andrea Paoli and all the other colleagues and friends who supported this post
Beyond Advanced Cardiac Life Support. Do we have to change our practice in COVID Era?
3 MayMain changes in recommendations
Personal Protective Equipment for Advanced Life Support interventions need to be at maximum level of protection of full body, eyes and airways.
CAT 3 level of protection 4 (at least) for the full body
FPP2/N95 airway filter for team members who are NOT directly involved in airway management, ventilation or manual chest compressions
FPP3/N99 airway filter for providers who are directly involved in airway management, ventilation and manual chest compressions.
Face shield and protective googles are strongly suggested
Mechanical Chest compressors devices are the gold standard to perform cardiac massage. They reduce contacts and contamination risk and team member exposure to contaminants.
Adhesive disposable pads are the only option to check rhythm and deliver shock. Dispose non-disposable, manual pads.
Passive O2 administration (via simple face mack at a rate of 15l/m) during chest compressions is the first option over bag mask ventilation when performing Basic Life Support waiting for advanced airway management.When using a Bag Valve Mask always put a HEPA/HME filter between Bag and mask to avoid contamination
Hold chest compressions when performing airway managment
Cover patient head with a transparent plastic foil to minimise virus spreading and contamination when performing airway management and bag mask ventilation
Tracheal intubation using a video laryngoscope is the first line option for advanced airway management to minimise contamination.
If video laryngoscope is not available Extraglottic devices are an acceptable first line option
Use all the implementation to improve intubation first passage success:
Video laringoscopy
Bougie
RAMP positioning
Suctioning (SALAD technique)
Use all the implementation to improve Extraglottic device placement
Laryngoscope for tongue displacement and mouth opening (DO NOT USE hands)
Deflate cuff
Lubrificate the device
Whatever plan you apply use an HEPA/HME filter immediately after the ventilation device
Use disposable cover and disposable gel to perform Ultrasound during chest compressions
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Tags: ACLS, COVID-19, Emergency Medicine guidelines, emergenza, emergenza sanitaria territoriale, medicina d'urgenza, medicina d'urgenza preospedaliera