Richard Levitan, MD Epiglottoscopy, [email protected] ... levitan - airway.pdf · Positioning, The Neglected Oriﬁce, & Passive Oxygenation Richard M. Levitan, MD Jeﬀerson Medical

Epiglottoscopy, Positioning,

The Neglected Orifice, & Passive Oxygenation

Richard M. Levitan, MD Jefferson Medical College

Philadelphia PA

Richard Levitan, MD [email protected]

EPIGLOTTIS:

The AnatomicCenter of the

Airway

Start to Finish

Tongue toCords

Right / Leftmidline


Tongue

Tracheal

axis

Epiglottis

Epiglottis positioned at intersection of two critical curves.Atlanto-occipital extension pivots tongue backward - not opening airway.

Head elevation improves jaw mechanics, jaw distraction lifts tongue and jaw upward, opening the space between the blue and yellow curves.

Mechanical

Center of the

Airway


Courtesy ofGeorge Kovacs, MD

Dalhousie NSEmergency Medicine

Atlanto-occipital extension (tilting head backward)does NOT open the airway


Imaging with Glidescope video system (Verathon)Epiglottis rests on the posterior pharyngeal wall when starting


Keys to Epiglottoscopy★Proceed slowly, methodically down tongue

★Distract tongue and jaw forward, and lift epiglottis edge off the posterior pharynx

★ If epiglottis is not seen, march down the tongue midline and then control the tongue

Beware of epiglottis camouflage !

fluids, blood, saliva poolin hypopharynx –

use suction tip if needed to clear hypopharynx and see

epiglottis edge

epiglottis: - reliable anterior landmark- able to be lifted out of fluids- top of laryngeal inlet


By the way, have been meaning to get this story to you... on my LAST SHIFT OF RESIDENCY at Jefferson I had the best airway story of my career... a poor young guy in his 20's comes in with a single GSW from his submental area extending through his face and out his forehead. Awake. Alert. Oxygenating, but blood gushing out of the remnants of his face and mouth... Trauma level 1's was called, so the whole ER and trauma/anesthesia service is surrounding me. I suction, push drugs...I take a look, see epiglottis edge and posterior cartilages, angle the blade so it lifts the epiglottis out of view, suction the pooling blood again, and get first pass success. Take a look at the 3D recon... with the tube in place.


Effect of different head positions on upper airway dimensionsand mechanics of jaw opening

Atlanto-occipital Extension

Neutral Head forwardpositioning


Jaw mechanics:

Mouth opening:widest with head brought forwardrelative to chest

Thyromental distance:

space tongue gets pushed into during

laryngoscopy,enlarges withhead forward


Kitamura Y, et al.Dynamic interaction of craniofacial structures

during head positioning and direct laryngoscopy...Anesth 2007, 107; 875-83.

Lifting the head lengthens the submandibular space (from M – L),allowing the anterior structures to be distracted forward and upward.

Note how axis of view steepens between positions.

Caudal and upward movementsof the mandible and tongue base

increase the distance between anterior and posterior obstacles ...an increase of the submandibular space may be essential for caudal movements of

anterior obstacles, allowing vertical arrangement of the anterior

obstacles and larynx.

“sniffing”

DL w lift


Elevate the head until the ear is at the sternal notch

Universal intubating and ventilation positionIndependent of age and size


Bimanual Laryngoscopy & Head Elevation


Cricoid Pressure > > Airway Collapse

Cricoid deformation, vocal cord closure and difficult ventilation all increase with increasing force of CP.

86-100% of patients have difficult ventilation at 44N

20 Newtons:51-99%100%

30 Newtons:51-99%100%

44 Newtons:51-99%100%

1 (7%)0

1 (7%)2 (13%)

1 (7%)4 (27%)

2 (13%)7 (47%)

011 (73%)

1 (7%)11 (79%)

Male Female(n=15) (n=15)

% CricoidDeformation

20 Newtons30 Newtons44 Newtons

Male Female(n=15) (n=15)Vocal Cord Closure

20 Newtons30 Newtons44 Newtons

Male Female(n=15) (n=15)Difficult Ventilation

6 (43%)8 (57%)11 (78%)

6 (50%)7 (58%)7 (58%)

6 (43%)10 (71%)12 (86%)

9 (75%)12 (100%)12 (100%)

These observations having been made, the fibrescopewas removed and the patient proceeded to surgery. Patientswere visited postoperatively to question them as to anyadverse effects, specifically sore throat and hoarseness.

Logistic regression was used to compare the relationshipof age, sex and body mass index (BMI) with deformationof the cricoid, difficult ventilation and vocal cord closure.Fisher’s exact test was used to compare rates of cricoiddeformation and difficult ventilation by sex at 20, 30 and44 N. The same method was used to compare rates ofvocal cord closure and associated difficult ventilation.Comparison of proportions was used to examine rates ofdifficult ventilation from any cause at 20, 30 and 44 N.Mann–Whitney test and Fisher’s exact test were used tocompare characteristics of those receiving neuromuscularblocking drugs and those who did not. A p-value of ! 0.05was considered significant when comparing differencesbetween sexes or forces. Patients in whom the glottisdeviated out of view or where the aryepiglottic foldscollapsed, obscuring the glottis, were excluded fromthe analysis. Including these as negative results (i.e. nocord closure and easy ventilation) had no effect on testsof significance.

Results

Thirty patients were recruited into the trial, 15 males and15 females (Table 1). There were no anaesthetic compli-cations. No patient suffered coughing or bucking duringthe study and no spontaneous vocal cord movement waswitnessed, regardless of anaesthetic technique. There wasno difficulty in ventilating the lungs of any patient whencricoid pressure was not applied. In 27/30 patients (90%)the view of the larynx and cricoid was classed as goodand remained so throughout. The view was average in onepatient and poor in another, in whom the LMA waschanged for one of a smaller size with an improvement inthe view. In two patients, during examination of the vocalcords the larynx deviated out of view below 20 N and intwo others there was inward collapse of the aryepiglotticfolds below 20 N; further assessment of the vocal cords wasnot possible in these patients.

Deformation of the cricoid occurred in a large numberof subjects (Fig. 2), with females especially vulnerable(Table 2). Vocal cord closure and difficult ventilationwere also common (Table 2). Difficult ventilation wasmore common at 44 N (24/30; 80%) than at 20 N (15/30;50%) for the whole group (p! 0.004). Occlusion of thecricoid and difficult ventilation were independently asso-ciated with female sex at all forces (Table 3). Vocal cordclosure was independently related to difficulty in ventila-tion at all forces, but not to age, sex or BMI, except at20 N, where there was a relationship between BMI anddifficulty in ventilation.

At 44 N, there were six subjects in whom complete cordclosure did not occur but in whom ventilation wasdifficult. In all of these cases, there was complete cricoidocclusion at that force.

There were no significant differences between patientswho received neuromuscular blocking drugs and thosewho received a propofol infusion, for age, sex, BMI or riskof vocal cord closure at all forces.

There were no complaints postoperatively that could bepositively ascribed to the examination performed.

Discussion

Cricoid pressure to prevent reflux of gastric contentsduring tracheal intubation has been described as ‘thelynchpin’ of the rapid sequence intubation. [3]. Since itsreintroduction by Sellick [1] it has become a standard of

Anaesthesia, 2000, 55, 260–287 Forum................................................................................................................................................................................................................................................

265! 2000 Blackwell Science Ltd

Figure 2 Sample view through the fibrescope of the anterioraspect of the cricoid cartilage (above) touching the posterioraspect. Note the two channels remaining on either side, a typicalappearance.

Table 1 Patient characteristics. Values are median [range].

Male Female(n!15) (n! 15)

Age; years 35 [17–73] 30.7 [17–70]Weight; kg 76.5 [51–98] 63.2 [48–92.6]Body mass index; kg.m"2 26.6 [20.7–31.1] 24.8! [19–31]

!n! 14; one subject excluded because no height was recorded.

The effect of cricoid pressure on the cricoid cartilage and vocal cords: an endoscopic study.

Palmer JHM. Anaesthesia, 2000: 55; 260 – 287.


Boyce JR et al., Obes Surg. 2003 Feb;13(1):4-9. A preliminary study of the optimal anesthesia positioning for

the morbidly obese patient.• 26 patients, BMI ~56 !• Reverse Trendelenburg (RT, 30 degrees tilt), Flat , Back Up Fowlers• Time SaO2 to drop 100% to 92%: Safe Apnea Period (SAP)


• 3 min pre-oxygenation , safe apnea period (SaO2 drop from 100% to 95%)

• 386 seconds to fall to 95% in head up group

• 282 seconds to fall to 95% in supine group

• 100 sec EXTRA safe apnea with head elevation

A Prospective, Randomized Controlled TrialComparing the Efficacy of Pre-Oxygenation

in the 20° Head-Up vs Supine PositionLane S, et. al. Anaesthesia 2005; 60: 1054-7.


- 40 obese patients (BMI >35); Group 1 (sitting, n=20) or Group 2 (supine, n=20).

- RSI in decubitus position, trachea intubated, pt left apneic and disconnected.

- Time desaturation to 90% from end of induction of anaesthesia was recorded.

- O2 and CO2 similar between groups, baseline and after pre-oxygenation.

- Mean time to desaturation to 90% was significantly longer in the sitting group compared with the supine group [mean (SD): 214 (28) vs 162 (38) s, P<0.05].

- Pre-oxygenation in sitting position significantly extends the tolerance to apnoea in obese patients.

Pre-oxygenation in the obese patient: effects of position on tolerance to apnoea

Aldermatt FR, et. al. BJA 2005; 95: 706-9.


of preoxygenation; to describe the slow and fast techniques for

preoxygenating patients; to review the effectiveness of thesetechniques in healthy adults with normal weight; to evaluate

the modifications to be applied in obese, pregnant, and elderly

patients; and to provide a brief overview of preoxygenationdevices other than the face mask.

Physiology of preoxygenation

In adults with ideal body weight, oxygen consump-

tion at rest is approximately 3 mL ! kg-1 ! min-1 or

200–250 mL ! min-1. During apnea, mobilizable oxygenreserves located chiefly in the lungs and blood are rapidly

depleted.1,2 An individual breathing room air has an oxy-

gen reserve of 1.0–1.5 L, most of which is bound tohemoglobin in red blood cells. Theoretically, patients

should be able to tolerate apnea that lasts up to 5 or 6 min;

however, oxygen saturation (SpO2) would decrease below90% after 1–2 min. If oxygen is given before the onset of

apnea, most of the additional oxygen is stored in the lungs

instead of the blood. This procedure creates an oxygenreserve that can be spent before depleting hemoglobin-

bound oxygen, thus it markedly increases the safe duration

of apnea (Fig. 1).At end expiration, when lung volume is equal to func-

tional residual capacity (FRC), alveloar fraction of oxygen

(FAO2) is approximately 16% in patients breathing air and

95% in patients breathing oxygen; CO2 occupies the

remaining 5%. Breathing 100% oxygen only marginally

increases the blood oxygen content because hemoglobin isnearly 100% saturated when breathing room air, and oxy-

gen is poorly soluble in plasma. Thus, virtually all of the

extra oxygen provided by preoxygenation is found in thelungs. This additional amount can be calculated as equal to

the FAO2at the end of preoxygenation (theoretically 95%)

minus the FAO2when SpO2 = 90% (FAO2

& 10%) multi-plied by FRC. If FRC = 2500 mL, the oxygen reserve

is 2500(0.95 - 0.10) = 2125 mL with preoxygenation,

compared to only 2500(0.16 - 0.10) = 150 mL with roomair. Assuming an oxygen consumption of 250 mL ! min-1,

the 2125 mL in the patient’s lungs can provide 2125/

250 = 8.5 min of apnea.Healthy humans can tolerate periods of relative hypoxia

lasting hours or days (SpO2 = 80% or less), as indicated by

altitude experiments. However, avoiding SpO2 \ 90% isrecommended at induction of anesthesia because SpO2

usually diminishes rapidly after the initial decrease is

observed. Therefore, a useful concept is the ‘‘safe durationof apnea’’, also termed duration of apnea without desatu-

ration (DAWD), which is defined here as the interval

between the onset of apnea and the time SpO2 reaches avalue B90%. This duration depends on: (1) the oxygen

reserve at the start of apnea; (2) oxygen consumption;

and (3) the amount of oxygen required to maintain

SpO2 = 90% (Table 1). In healthy adults, DAWD is typ-ically 6.9 min after inhaling 100% oxygen (slightly less

than the calculations above), 5.0 min after inhaling 80%,

3.5 min after inhaling 60%, and 1 min with room air.3

Clinical indications

Preoxygenation before induction of anesthesia is especially

indicated when mask ventilation is contraindicated, forinstance, in the case of a presumed full stomach; when

difficulties with mask ventilation are anticipated; when

tracheal intubation may take longer than usual; with specialairway management techniques, such as the insertion of a

double lumen tube; in patients who are likely to desaturate

quickly, such as those who are obese, pregnant, or febrile;and in patients with pulmonary disease. Since unantici-

pated difficulties with tracheal intubation are relatively

common, preoxygenation is recommended for all patientsbefore induction of general anesthesia.1

55459

838838931912

250400

250

2375

0

500

1000

1500

2000

2500

3000

3500

Air SpO2 =90%

Oxygen SpO2 =90%

Oxygen Reserves (mL)

Lungs

Hemoglobin

Plasma

Fig. 1 Oxygen reserves in a normal healthy adult when breathingroom air (left), after breathing 100% oxygen (right), at onset of apnea,and when reaching an oxygen saturation (SpO2) of 90%. In thisexample, the oxygen available for consumption during the apneicperiod amounts to 228 mL when breathing air and 2267 mL whenbreathing oxygen. Calculations are based on a functional residualcapacity of 2500 mL, hemoglobin concentration 140 g ! L-1,SpO2 = 98% on air, SpO2 = 100% on oxygen, and blood volume 5L. In this example, a subject with an oxygen consumption of250 mL ! min-1 could sustain a period of apnea of 228/250 =0.9 min after breathing air and 2267/250 = 9 min after breathingoxygen

450 I. Tanoubi et al.

123

Oxygen reserves in a normal healthy adult when breathing room air (left), after breathing 100% oxygen (right), at onset of apnea, and when reaching an oxygen saturation (SpO2) of 90%. In this example, a subject with an oxygen consumption of 250 mL per min could sustain a period of apnea of 228/250 =0.9 min after breathing air and 2267/250 = 9 min after breathing oxygen.

Pre-oxygenation: How it worksOptimizing preoxygenation in adults

Issam Tanoubi, et al. Can J Anesth/J Can Anesth (2009)) 56:449–466

Gasabsorptioncontinues

with apnea


With pulse ox saturation in 90's,how close are you to the edge?

Small changesin SaO2can correlatewith majorchanges inPaO2



Pre-oxygenation...get up onto on ledge

No-oxygenation...jump!

Post-oxygenation...landing

What if it was not the cessation of ventilation

that causes hypoxemia....but the REMOVAL of oxygen?


NO DESAT - Case Example:EtOH intoxication, level 560! Video Laryngoscopy

• Flat positioning, no O2, sonorous respiration - 70%• Flat positioning, no O2, nasal trumpet - 70%• Flat positioning, face mask, nasal trumpet - 73%• Head up, trumpet, face mask 15 lpm, NC 15 lpm - 90%• Head up, trumpet, bag mask, NC 15 lpm - 94%• Head up, trumpet, apnea during VL*, NC 15 lpm - 98%

*Video laryngoscopy with Glidescope x 4(two operators, lots of secretions)


- Pre-oxygenation with 100% O2 followed by O2 insufflation

- During the apnoeic period, O2 is extracted from the FRC into the blood at a rate of 250 ml/min to maintain metabolic O2 consumption.

- Due to greater solubility of CO2 in blood (90% stays in tissue)CO2 is added to the alveolar space at a rate of only 10 ml/min

- Net gas flow from the alveoli to the blood of 240 ml/min

- A subatmospheric pressure is established in the alveoli, and theambient oxygen is drawn ‘en masse’ into the lungs and maintains oxygenation.

Pulmonary uptake of oxygen, acid-base metabolism and circulation during prolonged apnea. Apneic diffusion oxygenation. Holmdahl M.

Acta Chirurgica Scandinavica 1956; 212 Supplement 1-128 (Suppl.): 1–128.

How apneic diffusion oxygenation worksRichard Levitan, MD

[email protected]

Apneic Oxygenation in ManFrumin MJ, Epstein RM, Cohen G.

Anesthesiology, Nov-Dec 1959, pp 789-798

18-55 minutes without any ventilationSaturation O2 98%-100%

Gas absorption CONTINUES without ventilation!


Apneic Oxygenation in ManHeller ML, Watson R, Imredy DS

Anesthesiology, Jan-Feb 1964, pp 25-30

When man becomes apneic after preliminary oxygenation, there is a marked

difference in the rate of arterial deoxygenationon whether the airway is open to room air

or attached to an oxygen reservoir.

Polarographic arterial studies PO2 studies show a rapid fall in PaO2 when atmospheric air

(containing 80% nitrogen) moves down theairway. In the case of pure oxygen reaching the

alveolar space, high PO2 values greater than 400mm of mercury were observed even after 5

minutes of apnea.

On the other hand, air with high nitrogen content dilutes alveolar oxygen...

Oxygen uptake is inhibited as alveolar oxygen tension falls.


Pulmonary and Cardiac Effects of Apneic Oxygenation in Man

Fraioli RL, Sheffer LA Anesthesiology, Dec 1973, pp 588-596


Pulmonary and Cardiac Effects of Apneic Oxygenation in Man

Fraioli RL, Sheffer LA Anesthesiology, Dec 1973, pp 588-596

Group IIObese, FRC 1/2 of Group 1


– n=20, nasal airway s/p induction (36 Fr)

– 8 Fr Catheter inserted just beyond nasal trumpet, 3

liters per minute– Sux, sedation, apnea until

pulse ox 92% or , 10 minutes had elapsed

– Each patient served as their own control

(with and w/o 3 lpm)

Pharyngeal Insufflation of Oxygen Prevents Arterial

DesaturationDuring Apnea

Teller LE, et al. Anesthesiology 1988; 69: 980-982


Nasopharyngeal oxygen insufflation followingpre-oxygenation using the four deep breath technique. Taha SK, et al. , Anaesthesia, 2006, 61, pages 427–430

- Preoxygenation 4 deep breath technique within 30 s, 30 ASA I or II patients

- Study group (n = 15), pre-oxygenation and insufflation O2 5 liter per min via a nasopharyngeal catheter commenced at the onset of apnoea.

- In the control group, pre-oxygenation was not followed by nasopharyngeal oxygen insufflation (n = 15).

- In the control group, SpO2 fell to 95% within a mean (SD) apnoea time of 3.65 (1.15) min,

- in the study group, SpO2 was maintained in all patients at 100% throughout the 6 min of apnoea

- Nasopharyngeal oxygen insufflation following pre-oxygenation using the four deep breath technique can delay the onset of haemoglobin desaturation for a

significant period of time during the subsequent apnoea.


http://www.ncbi.nlm.nih.gov.proxy1.lib.tju.edu:2048/pubmed?term=%22Ramachandran%20SK%22%5BAuthor%5D


– n = 30, BMI ~31 – 5 lpm via NC, 25 degree head up– 8 deep breaths pre-oxygenation

Apneic oxygenation during prolonged laryngoscopy in obese patients: a randomized, controlled trial of nasal oxygen administration.

Ramachandran SK, et al. J Clin Anesth. 2010 May;22(3):164-8.

Onas (n=15) NOnas (n=15)Pre-induction ETO2 (mmHg) 88.3 (1.9) 88.7 (2.6)Pre-induction FIO2 (%) 97.4 (1.7) 97.6 (1.9)Initial ETCO2 45.3 (4.6) 43.8 (3.9)Lowest SpO2 (%) 94.3 (4.4) 87.7 (9.3)*SpO2 ≥95% time (min) 5.29 (1.02) 3.49 (1.33)*Resaturation time (min) 0.69 (0.4) 1.57 (1.49)

Results means (SD). Onas=nasal O2 NOnas= no nasal O2, ETO2=end-tidal O2, FIO2=inspired O2 concentration, ETCO2=end-tidal CO2,

SpO2=oxygen saturation as measured by pulse oximetery.Resaturation time=time to regain SpO2 100% after tracheal intubation.

⁎ Statistically significant difference.




HIGH FLOW NASAL VS HIGH FLOW MASK OXYGEN DELIVERY: TRACHEAL GAS CONCENTRATIONS THROUGH A HEAD EXTENSION AIRWAY MODEL

2002 Open Forum Abstracts, Am Assoc Resp Care (OF-02-078)Tiep B, et. al.

- Ultrasonic flow studies recorded on digital video- Mask O2 remains outside the nose and mouth until the subject inhales

- Nasal O2 is stored in upper airways during exhalation - High flow nasal cannula delivery is more efficacious than the non-rebreather

mask at equivalent flows, due to O2 storage in the upper airways during exhalation poised for delivery upon the next inhalation

in addition to the continuous supply flow.


DELIVERY OF HIGH FIO2John W. Earl RRT, BS. Abstracts Am Assoc Resp Care 2003

Flow rates 10, 15, 30, 45, 60 lpm comparing a non-rebreather mask (NRB) vs. simple face mask (SM) and simple mask with side ports taped. Healthy subjects, breaths 12-18 per minute, TV 300-500

Each test 5 minutes, nitrogen washout 3 minutes

Results: Expired PO2 measured in pharynx:10 LM SM-51% NRB-50%15 LM SM-51% NRB-56%30 LM SM-55% NRB-77%45 LM SM-73% NRB-78%

60 LM SM 86% NRB-89% SM taped-93%

"Current thinking that a NRB mask running at 15 L/m is an acceptable way to deliver high FIO2 is not valid and should be revised."


Flat, mask only > poor pulmonary function, flow doesn't meet requirements


Upright, mask only > better pulmonary function, flow insufficent


Ear-to-sternal notch > promotes upper airway patencyPositioning improves pulmonary function

Mask and NC combined flow approach appropriate needs 30 liters/minute


Improved positioning for oxygenation, ventilation, intubation, and reducedrisk of regurgitation in trauma / C-spine immobilized


APNEIC oxygenation via nasal cannula during oral intubationNO DESAT: Nasal Oxygen During E!orts Securing A Tube

NO DESAT !

NO DESAT !

Mouth opened by oral device

O2 drawnpassively

into trachea

High FiO2in pharynx


Passive Apneic Oxygenation During Laryngoscopy


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Oxygenation andVentilation Strategy

Based on Pulse OximetryWeingart S, Levitan RM

Preoxygenation and Prevention of Desaturation During Emergency Airway Management, Ann Emerg Med, in press.TextWeingart S, Levitan RM. Ann Emerg Med. 2012 Mar;59(3):165-75


END of presentation

CONCLUSIONS• Safety hinges on oxygenation throughout procedure• Positioning is easy, very important, under appreciated• Pre-oxygenation: patent airway, max FiO2 > nasal O2• Passive oxygenation via nose during intubation efforts NO DESAT !

• Redundancy throughout: 2 ways to oxygenate 2 ways to intubate 2 ways to ventilate

Cannot intubate >>> Passively oxygenate, then ventilate?

thanks!


Documents

Richard Levitan, MD Epiglottoscopy, [email protected] ... levitan - airway.pdf · Positioning, The Neglected Oriﬁce, & Passive Oxygenation Richard M. Levitan, MD Jeﬀerson Medical