Title: The CobraPLA™ in 110 anaesthetized and paralysed patients: what size to choose?
Abstract: Editor'The Cobra Perilaryngeal Airway (PLA)™ is a new supraglottic device,1Agrò F Barzoi G Carassiti M Gallì B Getting the tube in the oesophagus and oxygen in the trachea: preliminary results with the new supraglottic device (CobraPLA™) in 28 anaesthetised patients.Anaesthesia. 2003; 58: 920-921Crossref PubMed Scopus (30) Google Scholar which consists of a tube with an inflatable cuff and a 15 mm standard adaptor. The softened distal end (CobraPLA™ head) of the breathing channel is designed to be positioned in the hypopharynx, opposite the laryngeal inlet, to divert the inspiratory gas into the trachea through the slotted openings (Fig. 1). Ethics committee approval and written informed consent was obtained from the patients before starting this study. Under supervision of a consultant anaesthetist, four residents inserted the CobraPLA™ in 110 ASA I/II patients aged 20–78 yr, undergoing general anaesthesia. The residents had already inserted the CobraPLA™ in a manikin 100 times and in 10 patients. Patients with gastro-oesophageal reflux, hiatus hernia, or other risk factors for pulmonary aspiration were excluded. After preoxygenation for 3 min, anaesthesia was induced with fentanyl 2–3 μg kg−1, followed by propofol 2–3 mg kg−1 and vecuronium 0.1 mg kg−1, and maintained with oxygen/air and sevoflurane. Routine monitoring was applied. The CobraPLA™ size was chosen according to patient weight in the range suggested by the manufacturer: size 3 (between 35–70 kg), size 4 (70–100 kg), and size 5 (100–130 kg). The device was inserted when the eyelash reflex was lost, the jaw had relaxed, and the patient was apnoeic. Patient position for placement was extension of the head with flexion of the neck (sniffing position), and the mouth was opened using the non-dominant hand. After deflating the cuff and folding it back against the breathing tube, the front and the back of the tube were lubricated together with the cuff itself. The CobraPLA™ was held in the dominant hand and inserted blindly straight back through the mouth until moderate resistance was felt. Ventilation was controlled with a tidal volume of 8 ml kg−1 and a ventilatory frequency of 10 bpm. Variables such as SpO2, E′CO2, blood pressure and heart rate were monitored and remained stable during insertion and the surgical procedure. Two attempts at insertion of the CobraPLA™ were permitted. If an effective airway was not achieved, the CobraPLA™ was removed and a tracheal tube inserted. CobraPLA™ insertion was possible in 100% of patients. It was considered easy (no tactile resistance or minimum tactile resistance) in 85/110 (77.3%), difficult (necessary to perform jaw trust or neck hyperextension) in 25/110 (22.7%) patients, and impossible in none. In 48/110 patients, a size 3 CobraPLA™ was inserted, in 62/110 a size 4. After insertion, adequate ventilation and a satisfactory seal were verified. We documented airway sealing pressures by closing the expiratory valve of the circular breathing system and noting the airway pressure at which a leak was heard, using a stethoscope placed on the neck. All patients were artificially ventilated through the CobraPLA™. In 56/110 (51%) patients there was a leak, although the cuff was inflated with the maximum volume indicated by the manufacturers: size 3 <65 ml, size 4 <70 ml, and 5 < 85 ml. In these patients, the device was removed and a larger size of CobraPLA™ was inserted. In 23 of the 48 patients in whom a size 3 CobraPLA™ was inserted (mean (sd) weight: 65.1 (3.6) kg, 95% CI 62.3–67.8), a size 4 was used successfully. In 33 of the 62 patients in whom a size 4 CobraPLA™ was inserted (weight 82.3 (3.4) kg, 95% CI 81.0–83.5), a size 5 was used successfully. As a result, a good seal (leak pressure 34.2 (2.8) cm H2O) was obtained using a size 3 CobraPLA™ in 25/110 patients (22.7%) who weighed 55.5 (3.6) kg (95% CI 53.9–56.9), a size 4 CobraPLA™ in 52/110 (47.3%) with a weight of 70.2 (7.2) kg (95% CI 68.2–72.2), and a size 5 in 33 /110 (30%) with a weight of 82.3 (3.5) kg (95% CI 81.0–83.5). Cuff inflation volumes were 26.5 (2.1) ml for size 3; 31.9 (4.0) ml for size 4; and 40.0 (4.1) ml for size 5. The mean time of insertion was 6.8 (2.0) s, which is shorter than that required to insert the laryngeal tube and LMA †LMA® is the property of Intavent Limited. †LMA® is the property of Intavent Limited. ProSeal.2Cook TM McKinstry C Hardy R Twigg S Randomized crossover comparison of the ProSeal™ laryngeal mask airway with the Laryngeal Tube® during anaesthesia with controlled ventilation.Br J Anaesth. 2003; 91: 678-683Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar No adverse airway events occurred and gastric inflation was not detected by auscultation over the epigastrium, in any patient. The mean time of artificial ventilation through the CobraPLA™ was 75 (12) min. These preliminary results suggest that the CobraPLA™ is easy to place blindly, allowing a rapid achievement of adequate oxygenation. In contrast to the recommendations of the manufacturers, we suggest the following range for choosing the size of CobraPLA™: size 3 for patients <60 kg; size 4 between 60–80 kg; and size 5 >80 kg. When using this range, the cuff inflation volume is much reduced from the maximum recommended by the manufacturer.