|LETTER TO EDITOR
|Year : 2021 | Volume
| Issue : 1 | Page : 67-68
Volume control mode: Guide for positioning of laryngeal mask airway
Preety Mittal Roy
Department of Anaesthesiology and Critical Care, Medanta: The Medicity, Gurugram, Haryana, India
|Date of Submission||29-Apr-2021|
|Date of Acceptance||09-Mar-2021|
|Date of Web Publication||29-Apr-2021|
Dr. Preety Mittal Roy
Department of Anaesthesiology and Critical Care, Medanta: The Medicity, Gurugram, Haryana
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Roy PM. Volume control mode: Guide for positioning of laryngeal mask airway. Airway 2021;4:67-8
Placement of the appropriate-sized laryngeal mask airway (LMA) under the correct plane of anaesthesia results in a high rate for satisfactory ventilation. Sometimes, the LMA is not correctly positioned leading to inadequate ventilation. In such cases, there is the need for performing the up-down manoeuvre described by Brain,, flexion or extension of the neck to correctly position the LMA. Brain manoeuvre consists of moving the whole LMA up and down inside the oral cavity without deflating the cuff. This helps in repositioning the infolded epiglottis., A little flexion or extension of the neck can also help in achieving adequate ventilation with LMA.
Van Zundert et al. have described common malpositions of supraglottic airway devices (SAD). The most common malpositions described were the tip of the distal cuff folding over backwards, the tip of the distal cuff positioned between the vocal cords, epiglottis folding double and positioning of the epiglottis in the bowl of the SAD with or without downfolding of the epiglottis. The presence of epiglottis in the bowl of the SAD will not lead to high airway pressures as there is no airway obstruction to begin with in this particular malposition.
We have observed that the pressure-time scalar during volume control ventilation can guide correct positioning of the LMA during these manoeuvres. Ventilation of the patient should be continued with volume control mode and the pressure-time scalar should be carefully observed on the monitor of the ventilator. When the LMA is not correctly positioned, the pressure-time scalar will show tall peaking waves [Figure 1]a. The peak airway pressure will be very high and the expired tidal volume will be very low on volume control mode. As soon as the LMA is correctly repositioned, there will be sudden reduction in the peak airway pressure and the expired tidal volume will improve. The pressure-time scalar will also return to its normal shape [Figure 1]b. We believe that barring the presence of the epiglottis in the bowl of the SAD, all other malpositions described by Van Zundert et al. can be identified by the changes in the pressure-time scalar.
|Figure 1: Pressure-time scalar during volume control mode of ventilation showing tall peaking waves (a) when the laryngeal mask airway (LMA) is not correctly positioned and return to normal shape (b) with improvement in tidal volume when LMA is correctly positioned|
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We propose that the observation of the pressure-time scalar during volume control ventilation can aid in confirming the correct position of the LMA while performing adjustment manoeuvres.
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Conflicts of interest
There are no conflicts of interest.
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