Users Online: 1111 Home Print this page Email this page Small font sizeDefault font sizeIncrease font size  
Home | About us | Editorial board | Search | Ahead of print | Current issue | Archives | Submit article | Instructions | Subscribe | Contacts | Login 

RSACP wishes to inform that it shall be discontinuing the dispatch of print copy of JOACP to it's Life members. The print copy of JOACP will be posted only to those life members who send us a written confirmation for continuation of print copy.
Kindly email your affirmation for print copies to preferably by 30th June 2019.


Table of Contents
Year : 2016  |  Volume : 32  |  Issue : 4  |  Page : 543-544

Lower tidal volumes through ProSeal laryngeal mask airway as compared to endotracheal tube?

Department of Anaesthesiology and Critical Care, University College of Medical Sciences and GTB Hospital, New Delhi, India

Date of Web Publication25-Nov-2016

Correspondence Address:
Rashmi Salhotra
A-2/268, II Floor, Paschim Vihar, New Delhi - 110 063
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-9185.194775

Rights and Permissions

How to cite this article:
Tyagi A, Salhotra R. Lower tidal volumes through ProSeal laryngeal mask airway as compared to endotracheal tube?. J Anaesthesiol Clin Pharmacol 2016;32:543-4

How to cite this URL:
Tyagi A, Salhotra R. Lower tidal volumes through ProSeal laryngeal mask airway as compared to endotracheal tube?. J Anaesthesiol Clin Pharmacol [serial online] 2016 [cited 2020 Sep 25];32:543-4. Available from:


In a randomized controlled trial, Kannan et al. compared the “ventilatory parameters and airway dynamics needed to maintain normocarbia” between ProSeal laryngeal mask airway (PLMA) versus endotracheal tube (ETT).[1] It was concluded that PLMA maintained normocarbia at “lower tidal volumes” and peak pressures without increasing the airway resistance, as compared to ETT. This apparently greater efficacy of PLMA needs closer scrutiny and may indeed be contrary to the quoted finding.

The tidal volume/minute ventilation requirement is expected to depend on apparatus dead space. The dead space of a size 3 PLMA is different from a size of 7.5 mm ETT. It is 39.6 ml for PLMA and 30.8 ml for ETT when calculated using Enghoff's modification of Bohr's equation by substituting the mean ETCO2 values reported by the authors (ETT: 37 mmHg; PLMA: 35 mmHg) and assuming similar PaCO2 of 40 mmHg. This finding of almost 9 ml higher dead space of the PLMA was also corroborated by us, by measuring the apparatus dead space in vitro using saline (approximately 21 ml and 13 ml for PLMA and ETT, respectively). For the ETT, we measured it only until the expected level at glottis, aiming to negate the effect of anatomical dead space. Thus, the use of PLMA entails a higher apparatus dead space. This would result in dilution of the recorded ETCO2 when initiating ventilation with same tidal volume. If further tidal volumes will be titrated using ETCO2 as done by the authors, an apparently lower tidal volume requirement will be seen progressively. On the contrary had PaCO2 been monitored by the authors, the results could show raised PaCO2 following the decreased volumes through PLMA. Thus, it is perhaps inaccurate to suggest a decreased tidal volume requirement through PLMA.

Second, the in vivo airway resistance was found to be same through both devices by the authors. This is contradictory to clinical perception regarding the devices as well as the earlier finding of Berry et al. who noted significantly lower resistance through the PLMA (almost 50% lesser).[2] Despite citing this particular article, Kannan et al. have made no comparison or give a probable explanation for this surprising and contradictory finding.[1]

If it is accepted that the resistance is indeed similar with both these devices, the finding of raised peak airway pressure with ETT is then a likely consequence of the raised tidal volume itself. Since Kannan et al. did not measure the plateau airway pressures, relative contribution by resistive, and elastic components on peak airway pressure cannot be commented upon.[1]

Finally, what is worrisome is the method used for sample size calculation by the authors. No previous dataset/value that is required for the calculation is mentioned. How was it calculated with only a presumed clinical difference?

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Kannan S, Harsoor SS, Sowmiya L, Nethra SS, Rani DD, Sathesha M. Comparison of ventilator efficacy and airway dynamics between ProSeal laryngeal mask airway and endotracheal tube in adult patients during general anesthesia. J Anaesth Clin Pharmacol 2015;31:517-21.  Back to cited text no. 1
Berry A, Brimacombe J, Keller C, Verghese C. Pulmonary airway resistance with the endotracheal tube versus laryngeal mask airway in paralyzed anesthetized adult patients. Anesthesiology 1999;90:395-7.  Back to cited text no. 2


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this article

 Article Access Statistics
    PDF Downloaded190    
    Comments [Add]    

Recommend this journal