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Respiratory support in suspected COVID-19 patients. When conventional O2 therapy is not enough!

20 Mar

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.

A step backward

The COVID-19 pneumonia. More than a “baby lung”

Clinical features and Imaging in early phases

  • Mild dyspnea
  • Severe hypoxia
  • Low P/F ratio
  • Respiratory failure
  • Lung failure
  • ARDS pattern
  • Ground glass
  • Crazy paving

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. 

Lung mechanics

  • High compliance
  • Low driving pressure
  • Reclutability
  • PEEP responsive

Evidences of clinical features of OneLevel (CPAP) and BiLevel (BiPAP) respiratory support in massive epidemic crisis.

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).

Clinical features OneLevel respiratory support

  • It’s not a ventilation but a spontaneous breathing on a fixed one expiratory level pressure. No inspiratory support.
  • Give a tritrable PEEP in the highly reclutable and “PEEP responsive” COVID-19 lung

Clinical features BiLevel respiratory support

  • It’s a proper ventilation on two level pressure
  • Give expiratory and inspiratory support with a tritrable driving pressure

Risk benefits assessment

More risk patient level
  • Patient may become agitated or combative due to hypoxia
  • Patient PPE must be removed
  • Clinicians are in close proximity to the patient’s airway
  • Aerosol generating events are more likely
More risk device level
  • High flow oxygen
  • Aerosol generation procedure
  • Poor mask sealing
  • Continuous manipulation at the mask/strap level to optimise sealing and patients compliance
Droplet spreading. OneLevel VS BiLevel respiratory support

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.

Prehospital strategy and practical tips

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.

Practical tips when using CPAP on the field

  • Use a non ventilated elbow to prevent risk of dissemination
  • Use a filter between the mask and the patient to prevent risk of contamination
References
  1. Wenjie Yang et al. Clinical characteristics and imaging manifestations of the 2019 novel coronavirus disease (COVID-19):A multi-center study in Wenzhou city, Zhejiang, China. Journal of Infection. 2020
  2. Hui DS, Chow BK, NG SS, et al. Exhaled air dispersion distances during noninvasive ventilation via different Respironics face masks. Chest 2009;136:998-1005.
  3. Randy S. Wax, MD. Practical recommendations for critical care and anesthesiology teams caring for novel coronavirus (2019-nCoV) patients, Can J Anesth/J Can Anesth. https://doi.org/10.1007/s12630-020-01591-x
  4. WHO. Clinical management of severe acute respiratory infection (SARI) when COVID-19 disease is suspected. Interim guidance 13 March 2020
  5. Xiaobo Yang, Yuan Yu. Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a single-centered, retrospective, observational study. http://www.thelancet.com/respiratory
  6. David J Brewster , Nicholas C Chrimes. Consensus statement: Safe Airway Society principles of airway management and tracheal intubation specific to the COVID-19 adult patient group.

COVID-19 and O2 therapy. Initial prehospital approach in mild symptomatic patients.

16 Mar

General considerations (dyspneic non infective patients)

Self Protection 

The generic dyspneic patients do not pose any particular self protection issues above the general precautions

Clinical needs

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:

  1. Nasal cannula
    • Maximum gas flow 15 l/m
    • FiO2 variable between 25-45% 
  2. Simple face mask
    • Maximum gas flow 15 l/m 
    • FiO2 variable between 40-60% at the mask level
  3. Nonrebreather face mask (reservoir)
    • Maximum gas flow 15 l/m
    • FiO2 more 80-100%
  4. Venturi mask 
    • Gas flow between 40 to over 80 l/m
    • FiO2 titratable between 24% and 60%management-devices-fio2-oxygen-delivery-original

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. 


Particular considerations in dyspneic potentially infective COVID-19 patients

Disclaimer

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.

Clinical needs

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. 

Self Protection 

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:

    • Eye protection or Facial shield
    • Medical mask 
    • Disposable gown
    • Disposable gloves

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.


Considerations 

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

  • Oxygenation –—+
  • Protection ++++

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)

Simple/Non rebreather Facial Mask 

  • Oxygenation —++
  • Protection ++–

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.

Venturi mask

  • Oxygenation -++++
  • Protection —-+

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

Hands Free Criticale Care. Yes We Can!

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Spinal Motion Restriction: Why?

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Year in Review. 2019 Advanced Life Support Literature of note.

15 Gen

Chest Compressions

Airway Management 

Pulse Check

Cath Lab

EtCO2

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Year in Review. 2019 Guidelines you must read. Free Open Access.

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Year in Review. 2019 Trauma Literature of note.

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Year in Review. 2019 Airway Management Literature of note.

8 Gen

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TXA in Trauma Patients. The CRASH 3 Trial.

21 Ott

Pulseless electrical activity following traumatic cardiac arrest: Sign of life or death?

11 Giu

On May 2019 was published an article we review today, cause the authors conclusions are pretty astonishing and worth a deeper look.

Israr, S & Cook, AD & Chapple, KM & Jacobs, JV & McGeever, KP & Tiffany, BR & Schultz, SP & Petersen, SR & Weinberg, JA. (2019). Pulseless electrical activity following traumatic cardiac arrest: Sign of life or death?. Injury. 10.1016/j.injury.2019.05.025.

Authors Conclusions: Following pre-hospital traumatic cardiac arrest, PEA on arrival portends death. Although Cardiac Wall Motion (CWM) is associated with survival to admission, it is not associated with meaningful survival. Heroic resuscitative measures may be unwarranted for PEA following pre-hospital traumatic arrest, regardless of CWM.Trauma death 2.jpg

What kind of study is this?

retrospective, cohort study consisting of adult trauma patients (n. 277 patients ≥18 years of age) admitted to one of two American College of Surgeons verified level 1 trauma centers in Maricopa County, Arizona within the same hospital system between February 2013 to September 2017 and January 2015 to December 2017.

Pre-hospital management by emergency medical transport services was guided by advanced life support protocols. 

Both hospitals for management of Traumatic Cardiac Arrest (TCA) followed the Western Trauma Association Guidelines

The following variables were collected from each patient:

  • Age
  • Gender
  • Duration of pre-hospital CPR
  • Survival to admission vs. pronouncement of death in ED
  • Disposition at hospital discharge

Results

  • 277 trauma patients that underwent pre-hospital CPR for TCA
  • Mean patient age was 43.1
  • Mechanism of injury was penetrating in 99 patients (35.7%), the most common of which was due to ballistic injuries, the rest where blunt trauma.
  • 52.0% of the patients were intubated prior to hospital arrival
  • 235 patients received epinephrine in route (84.8%)
  • Pre-hospital resuscitation duration, 20.0 (15.0 – 25.0) minutes

Outcomes

20 patients were identified on arrival to have had ROSC. 18 of these patients survived to hospital admission and 4 of them were discharged alive from hospital

147 patients were identified on arrival in asystole. Among these patients none were discharged alive from hospital.

The remaining 110 patients presented with PEA. 10 patients survived to admission, 9.1%, but only one, 0.9% was discharged from alive from hospital.

P-FAST was performed in 79 of the 110 patients with PEA (71.8%)

Presence of CWM was significantly associated with survival to hospital admission (2 but not to hospital discharge (zero with or without CWM).

Authors conclusions

  • Resuscitative efforts are unlikely to reverse the course of this pathophysiology, warranting sound clinical judgement from the treating physician concerning the decision to continue or desist, relative to mechanism of injury and clinical presentation.
  • CWM (signifying a beating heart and thereby pseudo PEA) was not associated with meaningful survival.
  • Nonetheless, we conclude that P-FAST is a useful tool for distinguishing PEA with cardiac standstill, which is in all likelihood terminal (and continued resuscitation would become an attempt at reanimation), versus pseudo PEA, whereby the heart is actually still beating, representative of a veritable sign of life, and ongoing resuscitative attempts may be considered appropriate despite the unfavorable prognosis.

My considerations on methodology and results

  1. Conventional ACLS protocol, as performed in the study, IS NOT the standard of care in TCA.
  2. No clinical intervention to address reversible causes where performed (or mentioned) in the field.
  3. The only clinically oriented manoeuvre performed in the field was tracheal intubation in just half of the patients (52.0% of the patients were intubated).
  4. Prehospital resuscitation time (20 minutes mean time) was spent performing non useful and potentially  dangerous interventions (closed chest compressions, epinephrine administration) for TCA.
  5. Patients with PEA and documented CWM (but not only them) at their arrival in ED has been hypo perfused during the entire pre-hospital resuscitation time and lost most of their chances for good clinical outcome.

So in my opinion this study and it’s conclusions are biased by a wrong approach to Traumatica Cardiac Arrest in the prehospital phase.

Emergency providers, when treating patients in traumatic cardiac arrest, need to perform interventions addressing the possible REVERSIBLE causes:

  1. Exanguination/Massive Hemorrage (Pelvic Binding, TXA administration, Tourniquet or direct compression)
  2. Hypoxia (Tracheal Intubation)
  3. Tension Pneumo (Double Thoracostomy)
  4. Hypovolemia (Blood or fluid resuscitation)

Emergency providers need to rely on direct (central pulse palpation, Ultrasuond) or indirect (EtCO2, Plethysmography) signs of perfusion to guide their clinical interventions.

Resuscitation of Traumatic Cardiac Arrest patients in not futile just need to be performed in the right way.

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References

Israr, S & Cook, AD & Chapple, KM & Jacobs, JV & McGeever, KP & Tiffany, BR & Schultz, SP & Petersen, SR & Weinberg, JA. (2019). Pulseless electrical activity following traumatic cardiac arrest: Sign of life or death?. Injury. 10.1016/j.injury.2019.05.025.

 

 

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