Analysing Supraglottic Airway Devices Biology Essay

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Supraglottic airway devices are now widely used for surgery requiring general anesthesia. The laryngeal mask airway and similar supraglottic airway devices use an inflatable cuff to wedge into the upper oesophagus and provide a perilaryngeal seal (Miller DM 2004). They provide a perilaryngeal seal with an inflatable cuff and are an alternative to tracheal intubation. Inflatable masks provide an airway seal but can negatively impact on how these devices are inserted, how they are positioned and how they perform. Inflation using the recommended volumes increases mask rigidity, decreases conformity with perilaryngeal structures and lessens the effective seal pressure. Mechanically, inflation can cause movement of the device because of the distal wedge shape of the mask.

Tissue distortion, venous compression and nerve injury have also been reported with the use of supraglottic airway devices with inflatable cuff. Finally, depending upon their materials, they can absorb anaesthetic gases especially Nitrous oxide, leading to increased mucosal pressures (Brimacombe et al 1998).

The I-Gel was designed to overcome limitations of cuffed supraglottic devices and marketed for clinical use after initial studies in cadavers and manikins.

The present study entitled "An Observational Study of the I-Gel - Supraglottic airway device with a noninflatable Cuff and an esophageal vent." was conducted to observe efficacy of the I-Gel in terms of:

Ease of insertion.

Time taken for placement of device.

Hemodynamic changes and changes in spo2.

Gastric distention.

Postoperative complications

The study comprised of 30 ASA I - II patients of either sex, aged between 20 and 60 years, scheduled for elective Surgery in the supine position in general anaesthesia.

Patients fulfilling exclusion criteria (pathology of the neck, upper respiratory tract or upper alimentary tract; predicted difficult airway, mouth opening <2.0 cm, body Mass Index >35 kg/m2, history of obstructive sleep apnoea, trendelenberg position, history of lung disease, potentially full stomach patients, history of gastric regurgitation and heart burn, oesophageal reflux) were excluded from study.

In the present study most of patients were of age group 20-30. Mean age was 35.87 ±12.34 years.

Male female ratio was 1:2 (male-10, female-20).This may be due to male patients not fulfilling inclusion criteria or fulfilling exclusion criteria hence excluded. However, there is no evidence with other supraglottic airway devices that gender influences success rate or seal pressure.

Mean duration of surgery was 61.26 ±21.15 min. Most of the patient's surgery lasted between 31-60 min.

Ease of insertion was recorded in three grades:

Grade I -Insertion within the pharynx without resistance in a single maneuver.

Grade II - Resistance to insertion or when more than one attempt/maneuver are required to seat the I-Gel within the pharynx.

Grade III- Failure of the I-Gel placement.

While most of the insertions were graded 1(n-26), effective airway could not be achieved in one patient despite three attempts/recommended maneuvers been performed. 3 patients required more than one attempt/maneuver to seat the I-Gel within the pharynx.

Maneuvers attempted were in the form of jaw thrust, chin lift and changing the size of the I-Gel. Onetime tongue got carried away posteriorly along with cuff of the I-Gel making further motion impossible. The device was reinserted after stabilizing the tongue along the floor of mouth (Taxak and Gopinath 2010).

The I-Gel was easy to insert and remove.

Levitan and Kinkle 2005 in their initial anatomic investigations of the I-Gel airway presumed that the smooth contiguous undersurface of the I-Gel from the tip of the bowl and throughout the entire tube section helps it to easily slide posteriorly along the palate, pharynx and hypopharynx. The I-Gel does not catch or become hung up on the tongue or epiglottis edge.

Richez et al 2008 described the first attempt at insertion was successful in every case. Insertion was scored very easy in 66 cases (93%) or easy in 5 others (7%). Only two failures occurred in seventy patients.

Francksen et al 2010 conducted a study for comparison of three different endotracheal tubes for blind intubation via LMA-Fastrach disposable and the I-Gel in an airway management manikin. The I‐Gel was inserted successfully with the first attempt by all investigators, whereas the insertion of the LFD was successful in 90% with the first attempt and in 10% with second attempt.

In our study time taken for the placement of the I-Gel was (8.83 ± 3.4) sec. Least time taken was 5 sec and longest time taken was 16 sec. Median time for insertion was 8 sec.

Bamgbade et al 2008 in an evaluation of 300 I-Gel insertions reported that in 290 patients, the I-Gel could be inserted within 5 sec, but they did not specify how insertion time was defined.

Most of the previous studies and case reports mention about short time taken for the I-Gel placement as compared to other supraglottic devices. The reason behind this could be insertion does not require an introducer or placement of the finger into the mouth as the device is simply pushed into place.

Other reason that leads to easy and quick placement is tube design. The tube section of the I-Gel is not a conventional rounded tube but has a widened and symmetrical, laterally flattened, cross-sectional shape. This design provided good vertical and lateral stability on insertion. The tube section is harder and more rigid than the soft bowl of the device. The firmness of the tube section and its natural straightness allowed the device to be inserted by grasping the proximal end of the I-Gel and guiding the leading edge against the palate into the pharynx. The smooth contiguous undersurface of the device from the tip of the bowl and throughout the entire tube section helps it to easily slide posteriorly along the palate, pharynx and hypopharynx.

Since no cuff inflation is needed in this device, which may lead to further shortening of time to achieve effective airway.

Theiler et al 2009 in their study reported insertion time 48± 26 sec when used as first device and insertion time 36 ± 18 sec when used as second device. These high values may be due to different definition of insertion time and simulated difficult airway scenario.

Francksen et al 2010 in their study found insertion time significantly shorter in I‐Gel group (p<0.0001).

Although in our study we did not check the position of the device with a fiberoptic laryngoscope, absence of clinically significant leak and absence of signs of airway obstruction suggested that the device was correctly positioned and that the epiglottis was not included or down-folded in the cuff. The noninflatable cuff is semi rigid and cannot be folded over, overinflated, or inserted in the trachea, thus diminishing the risk of airway obstruction.

Levitan and Kinkle 2005 in their cadaver study observed I-Gel was consistently positioned over the laryngeal inlet (mean percentage of glottis opening score of 82%) and conformation of the device to the perilaryngeal anatomy, as shown by endoscopy, dissection and radiography.

Theiler et al 2009 in their crossover study described fiberoptic view of the glottis remarkably good through the I-Gel compared with the LMA-Supreme. There was little epiglottic down-folding over glottic opening.

There was no significant change in pulse rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, SpO2 and rate pressure product during peri-operative period, which was recorded 5 minutes before induction, immediately after induction, immediately after the I-Gel placement and 1 min., 3 min., 5 min. and 10 min. after the I-Gel placement.

During the insertion of LMA, stress response (i.e. increase in heart rate and arterial pressure), may be induced by the passage of the LMA through the oral and pharyngeal spaces, pressure produced in the larynx and the pharynx by the inflated cuff and the dome of the LMA. Airway devices that cause a reduced stress response could be beneficial in patients with cardiovascular disease. Supraglottic devices are generally thought to cause minimal stress responses; however, this might not necessarily be true as some supraglottic devices, especially those with large oropharyngeal cuffs have been shown to provoke an increase in mean arterial pressure that might be considerably greater than that found following tracheal intubation.

Oczenski et al 1999 in their study haemodynamic and catecholamine Stress responses to insertion of the Combitube, Laryngeal Mask Airway or tracheal Intubation found that insertion of the Combitube was associated with a significantly higher and longer lasting increase in systolic arterial pressure, diastolic arterial pressure, mean arterial pressure, heart rate, and plasma catecholamine concentrations compared with insertion of the Laryngeal Mask Airway or endotracheal tube.

But in another study Dahaba et al 2006 found no major haemodynamic changes associated with placement of Laryngeal Tube-Suction Airway and the pLMA.

Jindal et al 2009 conducted a comparative study of three supraglottic devices:

I-Gel, SLIPA and LMA. They observed that the I-Gel produced less hemodynamic changes than SLIPA which is also a non inflatable supraglottic device. They reported that this difference may be due to different nature of materials of SLIPA and I-Gel. While SLIPA is made of moulded plastic (polypropylene) that does not conform to anatomic structures. The I-Gel is made up of SEBS (Styrene Ethylene Butadiene Styrene).

Shin et al 2010 in a comparative study of the I-Gel with pLMA and cLMA in anaesthetized patients found no differences in the haemodynamic data immediately after insertion of devices among the three groups.

In our study no significant adverse event was noted in any patient. The incidence of adverse events during peri-operative period was low. Proper oxygenation was maintained in all patients throughout device placement and operation. No suboptimal oxygenation (SpO2<95%) or hypoxia (SpO2 <90%) was detected in any patient probably due to shorter time for successful placement of the device.

Kannaujia et al 2009 in their study observed that two patient (4 %) suffered suboptimal oxygenation (SpO2<95%) which was rectified by airway manipulation in the form of increasing the depth of anaesthesia. None of the patient in their study had any episode of hypoxia (SpO2 <90%).

In our study no patient had significant gastric distension. Nasogastric tube was not passed through the gastric channel of the I-Gel in any patient. There was also no evidence of aspiration in any patient. Pulmonary aspiration associated with supraglottic devices are rare and has incidence comparable with the face mask and tracheal tube (Brimacombe and Berry 1995).

Kannaujia et al 2009 in their study found no gastric distention or evidence of aspiration in any patient. Nasogastric tube was passed in 50% of their patients which was successful and easy in every patient.

Uppal et al 2009 in their study randomized crossover comparison between the I-Gel and the LMA-U in anaesthetized, paralyzed adults found no evidence of gastric insufflation, regurgitation or gastric aspiration.

Three cases of regurgitation, including one confirmed gastric aspiration, have been reported by Gibbison et al 2008. In all these cases, the gastric channel allowed early identification of the regurgitation. In one patient in whom aspiration occurred, volume and speed of regurgitation was greater though bulk of regurgitant fluid exited through I-Gel drain tube.

Schmidbauer et al 2009 using cadaver model compared Oesophageal seal of the novel supralaryngeal airway device I-Gel in comparison with the laryngeal mask airways Classic and Proseal. Their study demonstrated that the cLMA and pLMA can withstand a significantly higher oesophageal pressure than the I-Gel airway when using a cadaver model. Independent of this finding, the pLMA and the I-Gel permitted a fast and complete drainage of oesophageal fluid through their open oesophageal lumens. Thus, tracheal aspiration may be prevented with their use.

Immediate postoperative complications were recorded in form of trauma of the mouth, tooth or pharynx or blood on device, nausea & vomiting, sore throat, dysphagia, dysphonia. There was no evidence of trauma to oral or pharyngeal cavities. While no patient complained of sore throat, dysphagia or dysphonia, one patient complained of nausea and one episode of vomiting was recorded in same patient. Causes of post operative nausea and vomiting are multifactorial. In this patient important factor associated may be female gender, young age, non smoker and use of nitrous oxide.

Singh et al 2009 in their study found incidence of blood staining of the device was more with pLMA (6/30) than with I-Gel (1/30) and tongue, lip & dental trauma was more with pLMA(5/30) than with I-Gel (1/30), although it was statistically not significant. There was no incidence of bronchospasm / laryngospasm and hoarseness.

Higher incidence of visible blood on the I-Gel after removal 12% (3/25) was found by Uppal et al 2009 in their study that they considered equivalent to those reported with other supraglottic airway devices in previous studies.

Shin et al 2010 in their comparative study of the I-Gel with pLMA and cLMA in anaesthetized patients found no differences in the incidence of adverse events except for the larger incidence of sore throat in the cLMA group.

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