The Physiologically Difficult Airway

Jarrod M. Mosier, MD , Raj Joshi, MD , Cameron Hypes, MD, Garrett Pacheco MD, Terrence Valenzuela, MD, John Sakles MD.
                                      University of Arizona ICU and ED Departments.
                                   Published, Western Journal of Emergency Medicine 2015

Full text available via open access http: escholarship.org/uc/uciem_westjem 

DOI 10.5811/westjem/ 2015

With recognition that many tools ( DL, VL, FOB, Surgical neck access),  are now available for the placement of endotracheal tubes and that CPAP , BIPAP also make a powerful contribution to oxygenation and ventilation ,  there remains another dimension of the airway management problem that needs to be addressed. 

Physiological Factors:

This important contribution to the teaching of Airway strategy underlines the four physiological states that add a complexity and risk to the Difficult Airway patient management. The special problems in the ICU and the ED are often coloured by the complex physiology of people who are suffering from profound general disorders. It is therefore fitting that this new look at the difficult Airway should come from Mosier (ICU) and Sakles (ED). Separation of these factors for special education and acute care consideration will surely make care safer in critical care areas.

1. Hypoxemia - with a patient at an unfavourable point on the oxygen dissociation curve leaving reduced margin for rapid deterioration. The pre oxygenation process becomes important prior to attempts at intubation. The use of Nasal approaches to provision of procedural oxygen are currently attracting more attention and study. These include the Thrive Hi Flo Nasal oxygen strategy, the simple use of nasal prongs (less effective but still added value) and nasal TSE PAP which uses the nose as a conduit for CPAP with a modified #2 Childrens mask.

    2. Hypotension- addressed  with standard volume optimization support  and pressor use as indicated. 

    3. Severe Metabolic acidosis - treated with disease specific therapy (i.e. Diabetic Keto-acidosis) and or other cause specific therapy such as septic state therapy.

    4. Right Ventricular failure - firstly awareness of the diagnosis is key followed by excellent strategies defined by truly expert care. The following are considered to be of value by Mosier and his team 1. Available bedside cardiac echo to assess right heart reserve allowing fluid use, 2. pre oxygenation (see above) 3. consider etomidate induction, 4. consider Norepinephrine to increase systemic pressure, and low mean airway pressure ventilation. To obtain a discussion of these outline points consult the original detail embodied in the paper itself.

Abstract