78. PREOXI Trial

Today, we’re going to be talking about pre-oxygenation methods for endotracheal intubation and the PREOXI Trial which is hot off the presses in the New England Journal of Medicine in June of 2024. This trial has potentially widespread, practice changing results and we’re lucky enough to be joined by two of the authors to discuss.

 

 

Dr. Kevin Gibbs is an Associate Professor of Medicine at Wake Forest University School of Medicine. He obtained his MD at George Washington University School of Medicine, and completed his residency and fellowship training at Johns Hopkins. He is an active researcher in critical care, ARDS, mechanical ventilation, and pragmatic trial design.

Dr. Jon Casey is an Assistant Professor of Medicine for the Division of Allergy, Pulmonary, and Critical Care Medicine at Vanderbilt University Medical Center. He obtained his MD from the University of Louisville School of Medicine, and completed his residency training at Brigham and Women’s Hospital before going to Vanderbilt for fellowship training. He is a physician scientist and also has his Masters of Science in Clinical Investigation. His research is focused on comparative effectiveness of ICU treatments and he also has a focus on pragmatic trials. He is supported with NIH funding and is active in the American Thoracic Society Critical Care Assembly.

Summarized Key Points


  • Significance of the Problem: Tracheal intubation in emergency and ICU settings is common, with significant risks such as hypoxemia (10-20% incidence) and cardiac arrest (2% incidence) associated with the procedure. This makes effective pre-oxygenation crucial.

  • Methods of Pre-oxygenation: Common methods include face mask oxygen (e.g., non-rebreather, bag-mask devices) and more advanced techniques like non-invasive ventilation (used in about 15% of cases globally). Each method has pros (e.g., simplicity, no risk of aspiration for face masks; 100% oxygen delivery, positive pressure for non-invasive ventilation) and cons (e.g., potential for gastric insufflation with non-invasive ventilation).

  • Study Design: The study discussed in the podcast is a pragmatic trial aiming to optimize pre-oxygenation strategies to prevent peri-intubation hypoxemia. Eligibility criteria were broad, encompassing most patients undergoing tracheal intubation in the ED or ICU, with exclusions mainly for safety reasons.

  • Primary Outcome: The primary outcome of the trial was hypoxemia, defined as oxygen saturation < 85%. This threshold was chosen because it signifies a critical point on the oxygen dissociation curve, where patients are at higher risk of further desaturation and adverse outcomes.

  • Secondary Outcomes: Secondary exploratory outcomes included more severe levels of hypoxemia (oxygen saturation < 80% and < 70%), aiming to capture varying degrees of oxygenation failure during intubation. Rates of cardiac arrest during intubation were an additional outcome.

  • Intervention Comparison:

    • The trial compared two methods of pre-oxygenation: non-invasive ventilation (NIV) and oxygen mask (face mask)

    • Both methods aimed to provide at least three minutes of pre-oxygenation before intubation.

    • NIV group specifics: Expiratory pressure of 5 cm H2O, Inspiratory pressure of 10 cm H2O, respiratory rate of 10 breaths per minute, and 100% oxygen delivery

    • Oxygen mask group specifics: Non-rebreather or bag mask device with at least 15 liters per minute oxygen flow.

    • Nasal cannulas and HFNC could be used in both groups.



  • Logistics and Equipment Use:

    • The trial allowed flexibility in using available equipment (invasive ventilator capable of NIPPV vs. dedicated BiPAP machine).

    • Sites were encouraged to use the same ventilator for both pre-oxygenation and subsequent ventilation to streamline workflow and reduce logistical challenges.



  • Primary and Secondary Outcomes:

    • Results showed a significant reduction in hypoxemia incidents in the NIV group compared to the oxygen mask group.

    • There was also a reduction in severe hypoxemia and a notable decrease in cardiac arrest incidents in the NIV group.



  • Aspiration Safety:

    • There was no statistical difference in aspiration-related outcomes between the NIV and oxygen mask groups, indicating that NIV did not increase the risk of aspiration.



  • Conclusions:

    • The trial concluded that NIV for pre-oxygenation significantly reduced the incidence of hypoxemia and possibly cardiac arrest during tracheal intubation.

    • It also dispelled concerns about increased aspiration risk with NIPPV as pre-oxygenation, suggesting it can be safely used in clinical practice.


Gibbs KW, Semler MW, Driver BE, Seitz KP, Stempek SB, Taylor C, Resnick-Ault D, White HD, Gandotra S, Doerschug KC, Mohamed A, Prekker ME, Khan A, Gaillard JP, Andrea L, Aggarwal NR, Brainard JC, Barnett LH, Halliday SJ, Blinder V, Dagan A, Whitson MR, Schauer SG, Walker JE Jr, Barker AB, Palakshappa JA, Muhs A, Wozniak JM, Kramer PJ, Withers C, Ghamande SA, Russell DW, Schwartz A, Moskowitz A, Hansen SJ, Allada G, Goranson JK, Fein DG, Sottile PD, Kelly N, Alwood SM, Long MT, Malhotra R, Shapiro NI, Page DB, Long BJ, Thomas CB, Trent SA, Janz DR, Rice TW, Self WH, Bebarta VS, Lloyd BD, Rhoads J, Womack K, Imhoff B, Ginde AA, Casey JD; PREOXI Investigators and the Pragmatic Critical Care Research Group. Noninvasive Ventilation for Preoxygenation during Emergency Intubation. N Engl J Med. 2024 Jun 20;390(23):2165-2177. doi: 10.1056/NEJMoa2313680. Epub 2024 Jun 13. PMID: 38869091.

70. Bronchoscopy Emergencies with Critical Care Time

We’re super excited to have a joint episode this week with Dr. Cyrus Askin and Dr. Nick Mark from Critical Care Time! We discuss all the ways that bronchoscopy can be your best friend in the ICU and how to be prepared for the unexpected scary situations that arise in the ICU. This ranges from airway bleeds, difficult intubations, lobar collapse, and trach emergencies. Don’t miss this great discussion!

Utility of bronchoscopy in people with critical illness

  • Bronchoscopy can be both diagnostic and therapeutic; both are potentially lifesaving. 
  • General situations where bronchoscopy is useful in the ICU:
    • Placing (or confirming placement of) an endotracheal tube or tracheostomy tube
    • Removing a foreign body or mucous plugs from the lungs
    • Localizing the source of pulmonary hemorrhage or performing interventions to stop/contain the bleed
    • Diagnosing certain rare conditions, particularly those where the diagnosis can substantially change management (e.g. DAH, AEP, rare infections, etc).
  • Proficiency with bronchoscopy is important to realize the benefits. Simply “having the equipment” is insufficient, regular practice/simulation is essential
    • Anesthesiologists, emergency physicians, and other specialists may have limited experience with bronchoscopy in training. Even experienced pulmonologists, who may be good at diagnostic bronchoscopy often have limited experience deploying bronchial blockers, using retrieval baskets, etc.
    • Remember: “People don’t rise to the occasion, they sink to the level of their training.”
    • If you haven’t regularly practiced with a bronchoscope, you are not going to be able to use it effectively under stress when performing high acuity low occurrence (HALO) procedures such as in emergent airways, deploying bronchial blockers, retrieving foreign bodies, etc.

Practice practice practice: High fidelity bronchoscopy simulators are available. Low cost bronchoscopy simulators (e.g. 3D printed DIY) are available.

Difficult Airways

  • Two broad situations where a bronchoscope is generally used:
    • Awake intubation in the anticipated difficult airway (e.g. someone with abnormal anatomy, airway tumor, etc)
    • Rescue method in the unanticipated difficult airway (e.g. very anterior cords, difficulty with Bougie, etc)
  • Nasal vs Oral approach:
    • Oral approach is usually used in an unanticipated difficult airway
    • Nasal approach: More common if performing an awake intubation. Nasal is often better tolerated however epistaxis can make a difficult airway almost impossible.
  • Sedation strategy:
    • Full topicalization: lidocaine vs cocaine (equally effective and lidocaine is normally preferred, however the vasoconstriction action of cocaine may be helpful in preventing epistaxis).
      • Which types of topicalization work best?
        • Spray as you go w/ or w/o and atomizer 
        • Nebulization (maybe better? maybe)
        • Gurgling (Nick: from personal experience lidocaine is super gross)
      • Remember total dose of lidocaine: < 8 mg/kg
    • Ketamine
      • Ideal because it’s dissociative and analgesic, maintains respiratory drive and (maybe) airway reflexes
      • Consider scopolamine patch to reduce oral secretions
    • Dexmedetomidine
      • Great adjunct
  • One vs two operator
    • Especially in unanticipated difficult airways; the second operator can use VL/DL to facilitate visualization of the vocal cords.
    • Second operator can also be preparing for a surgical airway.
  • Equipment considerations:
    • Preload the endotracheal tube onto the bronchoscope. Use the bronchoscope as a bougie to guide the ETT through the vocal cords.
    • Suction! You want two – one connected to the bronch and one connected to a yankuer.
    • Disposable vs “good” scope
    • Remember to load the tube first!
    • Also remember to lube the tube!

 

Tracheostomy troubleshooting 

  • Similarly to intubation, bronchoscopy can be very useful to confirm placement
  • Mechanics are similar to above
  • Goal is to avoid inadvertent placement of the tracheostomy tube into the soft tissues of the neck and to avoid putting air into those tissues (false lumen).
  • Advanced trick for exchanging tubes: You can use a disposable bronchoscope to exchange tubes: you can get it in, confirm placement, then cut it with trauma shears! Now you can slide the old tube out and put a new one in. (Don’t try this on a $40,000 fiberoptic bronchoscope!)
  • Ideally you should load the ETT onto the bronchoscope in advance (red arrow). If necessary however, you can cut the ETT and turn the disposable bronchoscope into a improvised exchange catheter. This technique is very useful for exchanging tracheostomy tubes.

 

Foreign Body Removal from airways

  • Bronchoscopy is invaluable for both diagnosis and treatment of foreign body aspirations. 
  • Most commonly these aspirations are food (nuts, seeds, etc), teeth, pills, etc
  • Great overview of the procedure.
  • Intubated vs awake
    • Intubated is harder in many cases: no cough to help, hard to get foreign body out of the ETT.
  • Flexible vs rigid
    • Most objects can be retrieved using flexible bronchoscope; however 15-20% require rigid bronchoscopy 
    • Flexible can reach smaller foreign bodies that are lodged more distally.
    • Rigid bronchoscopy is usually done if flexible bronchoscopy fails; an interventional pulmonologist wielding a rigid is superior but more invasive (requires GA)
  • Many different retrieval devices; technique depends on what equipment is available.
    • Forceps
      • Many types: shark tooth, rat tooth, alligator are most common
    • Basket
    • Grasper
    • Snare
    • Net (GI device repurposed)
    • Cryoprobe can be especially useful for frangible materials (e.g. food)

 

Mucous Plugs & Lobar collapse

  • Presentation can be subtle or dramatic.
  • Bronchoscopy can remove mucous plugs and help re-expand collapsed lung areas, which is potentially life saving.
  • Additionally, bronchoscopy can permit diagnosis of tracheal bronchus (bronchus sui)
    • Pig bronchus – 1-3% of people – have a RUL bronchus that comes off the trachea. 
    • Often presents with RUL collapse in an intubated person.
  • Suction considerations and bronchoscope size
    • Remember that suctioning force is highly dependent (i.e. radius raised to the fourth power!) upon the working channel size. Use the largest size bronchoscopy possible when suctioning.
  • Remember that other interventions: regular inline suctioning, chest PT, adequate hydration, mucolytics are also important to prevent recurrent mucous plugging.

 

Localization & Isolation of Pulmonary Hemorrhage

  • Pre-bronch interventions
    • Stabilization
    • Nebulized TXA
    • Bad side down → counter-intuitive because shifting blood flow, but also the goal is to protect the non-bleeding lung.
    • etc
  • Bronch can localize the bleeding site. Bronch can also perform interventions such as:
    • Cold saline
    • Epinephrine 1:100,000
    • Bronchial blockers – comparison of types
      • CRE balloon
      • Fogarty
    • Cryo probe – great for removing clots
    • Delivering ETT to contralateral side → single lung ventilation

 

Making “bronchoscopy only” diagnoses

  • Diffuse Alveolar Hemorrhage (DAH)
    • Finding: Increasingly bloody returns on serial lavages
  • Infections not covered by empiric therapies:
    • Invasive fungal infection (e.g. mucor), azole resistant fungi (C glabrata)
    • Rare/unusual infections (PJP, histoplasmosis, etc)
  • Infection mimics:
    • Acute eosinophilic pneumonia (AEP) and chronic eosinophilic pneumonia (CEP)
      • Finding: eosinophils > 20%
    • E-Cigarette Vaping Associated Lung Injury (EVALI)
      • Foamy lymphocytes
    • Organizing Pneumonia
    • Others
  • Remember to always send a cell count on a BAL! And cytology!
  • How often does bronchoscopy change management? Surprisingly often!
    • A study of how often bronchoscopy changes management in an oncology population. 500+ patients with AML or high grade myeloid neoplasms who underwent bronchoscopy at one center over 5+ years.
    • 1) an unexpected diagnosis was made and followed by a management change (as the most rigorous estimate of utility)
      • 13% of the time a diagnosis was only made because of bronchoscopy which changed management 
    •  2) the post-bronchoscopy diagnosis was discordant from the leading diagnosis considered before this procedure and was followed by a management change
      • 48% of the time pre and post procedure leading diagnoses were different
      • 26% of the time the change in leading diagnosis led to a change in therapy
    • 3) a change in management was made following bronchoscopy regardless of whether the diagnosis was expected or considered.
      • 32% escalation of antibiotics
      • 30% de-escalation of antibiotics
      • 9% addition of steroids
      • 2% mold → surgery
  • Remember that in critically ill patients whose symptoms are unexplained or failing to resolve with therapy, diagnostic flexible bronchscopy can provide useful insights.