Journal of Laryngology and Voice

LETTER TO EDITOR
Year
: 2020  |  Volume : 10  |  Issue : 1  |  Page : 18--19

Modified Kleinsasser laryngoscope for use with high flow nasal cannula


Rakesh Srivastava 
 Department of ENT, Sushrut Institute of Plastic Surgery and Super Specialty Hospital, Lucknow, Uttar Pradesh, India

Correspondence Address:
Rakesh Srivastava
Sushrut Institute of Plastic Surgery and Super Specialty Hospital, Lucknow, Uttar Pradesh
India




How to cite this article:
Srivastava R. Modified Kleinsasser laryngoscope for use with high flow nasal cannula.J Laryngol Voice 2020;10:18-19


How to cite this URL:
Srivastava R. Modified Kleinsasser laryngoscope for use with high flow nasal cannula. J Laryngol Voice [serial online] 2020 [cited 2020 Nov 30 ];10:18-19
Available from: https://www.laryngologyandvoice.org/text.asp?2020/10/1/18/299958


Full Text



Sir,

High-flow nasal cannula (HFNC) delivers heated humidified oxygen at 100%. Hence, it is advantageous to many diagnostic and therapeutic procedures of the upper airway.

Before HFNC usage, familiarity with the terms (1) safe apnea, (2) apneic oxygen, and (3) the mechanism of action of HFNC is imperative.

Safe apnea time is the duration of time until critical arterial desaturation (SaO288%–90%) occurs following cessation of breathing/ventilation. In a healthy preoxygenated patient, the safe apnea time is 8–9 min as against <1 min if he is breathing room air. During the apneic phase, no room air or expired gas with low oxygen enters the nasopharynx to dilute the 100% oxygen delivered through nasal prongs.

During apneic oxygenation, alveoli continue to take up oxygen even without the diaphragmatic movement or lung expansion. In healthy adults, 200–250 ml/min of oxygen move from alveoli into the bloodstream during the apneic phase, while 8–10 ml/min of carbon dioxide moves into the alveoli during apnea. The pressure difference results in a net gas flow of 240 ml/min from alveoli into the blood, generating a negative pressure gradient.[1],[2] This negative pressure gradient generates a gas flow into the lungs, also called aventilatory mass flow.

HFNC (Optiflow-Fisher and Paykel Healthcare Limited, New Zealand) has silicon make nasal cannula and it delivers 100% humidified oxygen at flow rate from 7 L to 70 L/min. The mechanism of HFNC functions is fourfold: (1) it washes out nasopharyngeal and pharyngeal dead space resulting in an increased fraction of oxygen. It denitrogenises the lungs and creates an alveolar oxygen reservoir. It bathe whole airway with oxygen, (2) Reduces the airway resistance and work of breathing by the continuous and adequate flow. (3) Improves lung compliance and airway conductance by providing heated, humidified oxygen. (4) Provide end distending pressure to the lung. HFNC can generate FiO21.0 and positive end-expiratory pressure of up to 7.4 cmH2O at 60 L/min oxygen.

Patel and Nouraei used HFNC on 25 difficult airway patients with different hypopharyngeal or laryngotracheal lesions under apnoeic conditions. The surgeries were done through transnasal high-flow humidified oxygen with intravenous induction and later neuromuscular blockade (Transnasal Humidified Rapid-Insufflation Ventilatory Exchange-THRIVE technique).[3]

Suspension microlarygoscopic surgeries are done with various rigid laryngoscopes. Kleinsasser laryngoscope is most often used. During micro laryngoscopy, the distal end of the laryngoscope is positioned at the level of vocal folds, thus it completely blocks the laryngeal inlet. Complete occlusion hampers the flow of oxygen coming from HFNC into the lower airway. Prolonged surgical procedure duration and with the use of sucker in the airway, the oxygen concentration in dead space (pharyngeal, laryngotracheal) drops. To maintain continuous flow and concentration of oxygen in dead space and distal airway, fenestrae were created in Kleinsasser laryngoscope. Six fenestrae on the back surface and two on either side of adult Kleinsasser laryngoscope were created. The opening has rounded edges with diameter of 5 mm [Figure 1]. Author has been using this fenestrated laryngoscope with HFNC for the past 2 years in all airway and micro laryngeal procedures in adults with success.[4]{Figure 1}

Acknowledgment

To my Anaesthetist and Operation Room Assistant.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Tanoubi I, Drolet P, Donati F. Optimizing preoxygenation in adults. Can J Anaesth 2009;56:449-66.
2Holmdahl MH. Pulmonary uptake of oxygen, acid-base metabolism, and circulation during prolonged apnoea. Acta Chir Scand Suppl 1956;212:1-28.
3Patel A, Nouraei SA. Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE): A physiological method of increasing apnoea time in patients with difficult airways. Anaesthesia 2015;70:323-9.
4Srivastava R, Agarwal AC, Agarwal S, Pathak M. High Flow Nasal Cannula: A Game Changer in Airway Surgery. Indian J Otolaryngol Head Neck Surg 2019;71:299-303.