Surgeons Guide to Airway Management Dr John Allen Pacey MD , FRCSc No.2

The Tools For Excellence In Airway Management Are Now Available.

         The last 20 years have provided many new tools for airway management with the result that there are many options now available for management of most anatomical and physiological states. This is not meant to be any kind of complete history of development of useful devices and will not consider, for example, the “Iron Lung” developed for the polio era or many other useful devices.

         The “Big Seven” Airway Tool Strategies include :

1. Direct surgical access. 

2. Facial Masks – Standard Face Mask and Nasal Mask.

3. DL-Direct Laryngoscopy.

4. FOL-Fiberoptic Laryngoscopy.

5. VL-Video Laryngoscopy.

6. Supra-Glottic Airways –LMA , I-GEL , King LT etc.

7. HFN- Hign Flow Nasal (THRIVE) or High Pressure Nasal (NASAL _TSE PAP)

·      The ancient tracheotomy and surgical approach to the airway goes back to Egyptian Medicine circa 3600 BC where tablets have been found with images of tracheal access surgery. The relief of airway obstruction in ancient times was not documented in a way that would allow determination of how many thousand years BC this practice was invented.

·      The cuffed endotracheal tube was invented by Trendelenburg  in approximately 1895 and popularized the development of endotracheal anesthesia that replaced the Ether drop and Chloroform muzzle of earlier days.

·      The vintage 30 degree angulated Direct view Macintosh laryngoscope  1943  with its partner the Direct view Miller Laryngoscope have been the mainstay resources throughout the development of Intubation strategies for Anesthesiology and Emergency Medicine. While these devices were not the first Direct viewing devices they were substantial leaps forward with implementation of a reliable light carried onboard.

·      The development of a fiberoptic endoscope in 1957 with light bundle fiber clusters to carry light to the body interior and then carry an image back to the Medical observer. This led to the first indirect viewing class of endoscopes that proved to be a great advance in capability. These devices were popularized by Andranic Ovassapian who later with friends in the airway community innovated the “Society for Airway Management” designed to develop and foster a culture aimed at solving the difficult airway conundrum.

·      The flexible light fibers and small DC bulbs also permitted development of lighted flexible stylet products , some with viewing capability like the Shikani laryngoscope and others without viewing such as  the Trachlight class of lighted stylets.

·      The development of the Laryngeal Mask Airway concept was innovated by Archie Brain to move the mask seal component from the face where seals could be problematic to the area immediately behind the glottic complex. This strategy was effective and provided a “Plan B “ backup for the cannot intubate cannot ventilate ( CICV) situation that was causing a continuous string of failed airways resulting in patient death and cerebral cell death. Then a prolific period of innovation provided a plethora of SGA (Supra Glottic Airways) that followed the original designs.

·      The invention of the GlideScope Highly Angled CMOS Video Laryngoscope (60 Degree)by Pacey in 2000 provided a new asset for airway managers and proved to be a useful new portable device for hospital and out of hospital use. Storz developed their fiberoptic rigid laryngoscope direct view device by adding a video camera in the handle. Later a variety of 60-90 degree rigid video laryngoscopes were introduced by Pentax, McGrath and others.  Some carried display screens on the handle while Saturn introduced the rugged compact 1.5 lb. water proof  USAF inspired Ranger for Military and Civil EMS application. Verathon subsequently has developed and marketed in excess of 30 variants of the original GlideScope. The video laryngoscope has subsequently earned a place in the DAS 2015 and ASA 2013 difficult airway guidelines where its use may be implemented as a first attempt device or at many stages in the decision making tree.

·       Surgical kits designed to gain access to the trachea used the Seldinger strategy with guide wires and even ultrasound guidance to aid the user. A series of dilating devices like the “ Blue Rhino” became common for ICU tracheostomy to elegantly wean ventilated patients.

The field use of these surgical kits proved to be less satisfactory because usually the application of these kits was carried out too late at a time when the patient was in an extreme pre- arrest state. The US Army had a disappointing legacy with these devices because of the training gap that exists for a device or system that requires a significant judgement level for optimal application.

·       Nasal strategies are now the most quickly developing  approaches to attack the problem of inadequate ventilation prior to intubation. The initial work was done using normal flow nasal prongs to augment the standard 4 minute BVM preoxygenation . Then higher flows were used to provide a flush during intubation and mixed results were obtained but these efforts were encouraging in some patients. The goal is to increase the period of sustained oxygenation and slow the deterioration on the classic curve of Benumof which shows the minutes to desaturation for Obese, Normal 10 Kg. Child , Moderately ill Adult, Normal 70 Kg. Adult .

The evolution in Nasal Oxygen delivery has progressed to the delivery of up to 70 L/min. of HFNO (High Flow Nasal Oxygen) via the proprietary  THRIVE device from Australia which can deliver humidified high flow Nasal O2 and result in a defacto Nasal CPAP where the flow is so high that continuous positive pressure exists. This high flow is in effect providing CPAP and apneic oxygenation with the attendant expenditure of copious amounts of oxygen. ( 40-70L/min.) This use of oxygen could be a problem for prehospital transfer or forward military sites  where  oxygen supplies are less plentiful.

Dr James Tse has taken another tack with nasal TSE PAP which involves using a Pediatric size 2 oro-nasal mask  which is applied to the nose of an adult and used to create Nasal CPAP which acts by opening the Nares, Displacing the soft palate forward against the tongue, avoidance of posterior displacement of the Jaw and tongue, and finally administration of a positive pressure throughout the respiratory cycle. This has been shown to be superior to the classic  Facial mask which applies pressure to the jaw and mouth area forcing the jaw back and the posterior aspect of the tongue against the posterior wall of the pharynx.

         The mask can be in position throughout the intubation process as well with the effect that the only time that TsePAP is not providing positive pressure is during actual laryngoscopic opening of the oropharynx. During this reduction in pressure the nasal oxygen continues to flow providing an oxygen rich environment down to the Glottis and to alveoli that have just recently been opened by the TsePAP effect. The net result is that it is uncommon to have oxygen saturation below 100 % even when various manouvers have been executed.  The consumption of oxygen with TsePAP is more in the range of 5-10 L/min.

Figure. 1 Time in minutes to precipitous desaturation of oxygen in the blood for (Left to Right) obesity , 10 Kg. Child , & 70 Kg. moderately ill Adult, and Normal Adult  .