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Causes of airway obstruction during cuffed oropharyngeal airway use
Resuscitation 48 (2001) 275– 278 www.elsevier.com/locate/resuscitation
Causes of airway obstruction during cuffed oropharyngeal airway use N. Yahagi *, M. Kono, M. Kitahara, K. Watanabe, Y. Fujiwara, Y. Asakawa, J. Katagiri, M. Sha, A. Ohmura Department of Anaesthesiology, Teikyo Uni6ersity Mizonokuchi Hospital, 213 -8507 Kanagawa, Japan Received 1 February 2000; received in revised form 6 July 2000; accepted 6 July 2000
Abstract This study investigated the cause for needing airway maneuvers to maintain a patent airway during the use of cuffed oropharyngeal airway (COPA). Twenty adult patients (29.4 9 6.8 years-old, ASA 1 – 2) scheduled for minor gynecological surgery who required brief manipulations of the airway despite COPA use following the manufacture’s guidelines, were enrolled in this study. To obtain airway patency, 15 patients required only the head-tilt maneuver. In eight of the 15 patients, the laryngeal inlet was opened partially (n=4) or completely (n =4). Despite lifting the epiglottis, the laryngeal inlet was incomplete at the level of pharyngeal view. The patency of the laryngeal inlet was decided by the extent of the distance between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone. In the other seven patients, the head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet. Five patients required both the jaw-thrust and head-tilt maneuver. Of these patients lifting the epiglottis was incomplete in three and the laryngeal inlet was partially collapsed in one even after the airway manipulations. The airways in these three patients, however, became patent after manipulations despite the persisting partial obstruction. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Hyoid bone; Laryngeal inlet; Equipment; Cuffed oropharyngeal airway; Bronchofiberscope; Manipulations; Head tilt; Jaw thrust
Resumo Este estudo investiga as causas de obstruc¸a˜o da via ae´rea e a necessidade de manobras de desobstruc¸a˜o durante a utilizac¸a˜o da via ae´ra orofarı´ngea com cuff (VAOF com cuff). Foram incluı´dos neste estudo 20 adultos (29.4 9 6.8 anos; ASA 1-2), submetidos a cirurgia ginecolo´gica minor e que necessitaram de manobras simples para manter a permeabilidade da via ae´rea durante a utilizac¸a˜o de VAOF com cuff, segundo as recomendac¸o˜es do fabricante. Em 15 doentes a obstruc¸a˜o resolveu com hiperextenc¸a˜o da cabec¸a. Em oito dos doentes a abertura da laringe foi parcial (n =4) ou total (n= 4). Apesar da elevac¸a˜o de epiglote, a abertura da laringe era incomplete quando observada da faringe. Em todos os casos a causa da obstruc¸a˜o foi investigada por fibroscopia, e a pateˆncia da fenda glo´tica medida pela distaˆncia entre a parede farı´ngea posterior e a prega glosso-epiglo´tica formada pelo osso hioide. Nos doentes do primeiro grupo a hiperextensa˜o da cabec¸a permeabilizou completamente a via ae´rea em apenas 7. Cinco dos doentes necessitaram de hiperextensa˜o da cabec¸a e subluxac¸a˜o da mandı´bula. Em treˆs destes a elevac¸a˜o da epiglote foi incompleta em treˆs e num deles a fenda glo´tica estava incompletamente aberta mesmo depois da manipulac¸a˜o da via ae´rea. Contudo a via ae´rea ficou permea´vel em todos os treˆs a seguir a´ manipulac¸a˜o da via ae´rea. © 2001 Elsevier Science Ireland Ltd. Todos os direitos reservados. © 2001 Elsevier Science Ireland Ltd. Todos os direitos reservados. Pala6ras cha6e: Osso hio´ide; Fenda glo´tica; Via orofarı´ngea com ‘‘cuff’’; Broncofibroscopia; Manipulaço˜es; Hiperextensa˜o da cabeça e subluxaçao da mandı´bula
1. Introduction * Corresponding author. Present address: Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. Tel.: +81-358418393; fax: + 81-3-58416481. E-mail address: [email protected] (N. Yahagi).
The cuffed oropharyngeal airway (COPA) is a modified Guedel airway with an inflatable distal cuff, designed to provide ‘hands free’ anesthesia for spontaneous breathing patients by displacing
0300-9572/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0300-9572(00)00258-6
276
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
the base of the tongue, lifting the epiglottis, and sealing the pharynx. In about 30–40% of the patients, however, brief manipulations (head tilt and jaw thrust) were necessary [1–3]. In this study, we investigated the mechanism for when airway manipulation was needed to maintain the airway and how this manipulation relieved the obstruction during COPA use by bronchofiberscopy.
2. Methods This study was approved by the Institutional Review Board (IRB). Twenty adult patients with ASA 1 – 2, 18 – 46 years-old were scheduled for minor gynecological surgery. All patients required underwent anesthesia using a COPA device following the manufacture’s guidelines. Patients were included in the study if they required any airway manipulation during the anesthesia. Patients were excluded from the trial if they were B18 years-old, required surgery in non-spine/non-lithotomy positions, had a known or predicted difficult airway, had respiratory tract pathology, had a sore throat within 10 days, had a body mass index \ 35 kg m − 2, were at risk of aspiration, or were considered otherwise unsuitable for a facemask [2]. The initial COPA size was chosen according to manufacturers instructions by placing the distal tip of the device at the angle of the jaw of a patient in the spine position with the COPA straight up, perpendicular to the floor. When viewed from the side, the tooth/lip guard of the COPA would be about 1 cm ventral to the lip in a properly sized device. Anesthetic management was standardized according to the following protocol: monitoring was applied before induction and included electrocardiograph, pulse oximeter, gas analyzer, and noninvasive blood pressure monitor. All patients were allowed to breathe spontaneously. Anesthesia was induced with the patient in the supine position with the head on a standard pillow. Sedation with pentazocine 0.03 mg kg − 1 and oxygen at a dose of 6 l min − 1 were administered. Anesthesia was induced with intravenous administration of propofol 2.5 –3 mg kg − 1 and maintained with 66% nitrous oxide, 33% oxygen and 1–2% sevoflurane. Facemask ventilation was commenced and continued for at least 30 s until conditions were suitable for insertion of the COPA.
Anesthesiologists were instructed to insert and fix the devices according to the manufacturer’s instructions. The device was connected to a circle breathing system, and the cuff was inflated to achieve a good seal or until the maximal recommended inflation volume was reached. An effective airway was judged by thoracoabdominal movement, a square wave capnograph trace, an oropharyngeal leak pressure \10 cm H2O, and maintenance of SpO2 \90%. All patients included in the study were those requiring airway intervention. Minor airway interventions included adjusting the head/neck position, or device adjustments, such as changing depth of insertion or adjusting the cuff volume of the COPA. Major airway interventions required the application of the jaw lift or changing the device size. Patients underwent manually assisted breathing (MAB) until spontaneous breathing (SB) resumed. During the MAB phase, an oropharyngeal leak test was performed by closing the expiratory valve of the circuit at a fixed gas flow of 6 l min − 1 and noting the airway pressure at which gas started to leak into the mouth (oropharyngeal leak pressure) [2]. Bronchofiberscopical (Olympus 3C-20, OD 3.6 mm or D-BASE Japan Easyscope SMS-ES1, OD 3.6 mm) assessment of the airway was made via the COPA device at two points, immediately proximal to the orifice of the COPA for a view of the base of the tongue and the larynx (pharyngeal view) and at the level of the epiglottis (laryngeal view) for assessment of the laryngeal inlet.
3. Results Table 1 shows demographic details of the patients. All 20 patients showed obstruction of the larynx by the sagged tongue base before airway manipulations despite the properly positioned distal orifice of the COPA (Fig. 1). In all 20 patients, the distal orifice of the COPA was situated very close to the top margin of the epiglottis and the Table 1 Demographic data of the patientsa Age Weight Height Size of COPA
a
Values are mean 9 S.D.
29.49 6.8 years old 51.2 9 5.0 kg 159.2 9 4.9 cm 9.0= 7 patients 10.0=13 patients
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
277
Fig. 1. The larynx was obstructed by the sagging tongue base before airway manipulations, despite the properly positioned distal orifice of COPA. Fig. 2. Top three views (pharyngeal view). Bottom three views (laryngeal view). In the pharyngeal view, epiglottis lifting was still incomplete in eight patients. The opening between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone, was moderate (2A-1) or complete (2B-1). The laryngeal inlet was opened partially (2A-2) or completely (2B-2). In seven patients (2C-1, 2C-2), head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet.
direction of the tip of the COPA bent forward and stuck to the base of the tongue. The laryngeal inlet of all 20 patients was covered with the base of the epiglottis, which was compressed by unlifted hyoid
bone. To obtain airway patency, 15 patients required only the head-tilt maneuver. In eight of the 15 patients, the laryngeal inlet was opened partially (n= 4, Fig. 2A-2) or completely (n=4, Fig.
278
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
2B-2). Despite lifting the epiglottis, the laryngeal inlet was obstructed at the pharyngeal view (Fig. 2A-1, Fig. 2B-1). The patency of the laryngeal inlet was decided by the extent of the distance between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone (Fig. 2A and B). In the other 7 patients, head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet (Fig. 2C-1, Fig. 2C-2). Five patients required both the jaw-thrust and head-tilt maneuvers. In these patients, lifting the epiglottis was incomplete in three and the laryngeal inlet was partially collapsed in one even after the airway manipulations. The airways in these three patients, however, became patent after manipulations despite the persisting partial obstruction.
4. Discussion The patency of the laryngeal inlet at the laryngeal view was essentially decided by the extent of the lifting of the hyoid bone was made by observing the distance between the posterior pharyngeal wall and the lateral glossopharyngeal fold. In the pharyngeal view whether the epiglottis was lifted or not, did not predict the opening of the laryngeal inlet. This is because of a wide variation exist in the degree of bend of the epiglottis and shape of the epiglottis (concaved, long, or floppy epiglottis). During use of laryngeal mask airway, which lifted hyoid bone, down fold of epiglottis were seen in 13–60% cases with no clinical symptom of airway obstruction [4 – 6]. Airway patency was due to the collapse of the hyoid bone. This caused obstruction of the laryngeal inlet through the tip of the COPA, which was situated just above the top edge of the epiglottis. Tongue was floppy which did not support the hyoid bone and maintain the laryngeal inlet patent. The tension of the hypopharynx may be decided not only by the anatomy but also by the
.
depth of anesthesia. In this study, the anesthetic level was not so different in each patient because the concentration of anesthetics was the same and the evaluation of airway patency was made at the same SB phase (Pet CO2 was similar). A limitation to this study was that we did not measure the anatomical variables which could suggest the characteristics of the airway though all the patients’ pharyngeal condition was Mallampati score 1 or 2. Further studies are needed to evaluate anatomic variability. The shape of the cuff has some room for improvement. The cuff height of the COPA is the same between the minor curvature and the major curvature. In our study, the tip of the COPA device bent forward and stuck to the base of the tongue in all 20 patients with or without minor manipulation. Ideally, the distal end of the minor curvature of the cuff, which should be thicker, might be extended more distally to lift the hyoid bone effectively. In conclusion, the difficulty of maintaining patent airway during COPA use may be in part explained by collapse of the larynx at the level of the hyoid bone.
References [1] Greenberg RS, Brimacombe JR, Berry A, Gouze V, Piantadosi S, Dake EM. A randomized controlled trial comparing the cuffed oropharyngeal airway and the laryngeal mask airway in spontaneously breathing anesthetized adults. Anesthesiology 1998;88:970– 7. [2] Brimacombe JR, Brimacombe JC, Berry AM, et al. A comparison of the laryngeal mask airway and cuffed oropharyngeal airway in anesthetized adult patients. Anesth Analg 1998;87:147– 52. [3] Asai T, Koga T, Jones RM, Stacey M, Latto IP, Vaughan RS. The cuffed oropharyngeal airway. Anaesthesia 1998;53:810– 22. [4] Nandi PR, Nunn JF, Charlesworth CH, Taylor SJ. Radiological study of the laryngeal mask. Eur J Anaesthesiol 1991;4:33– 9. [5] Molloy AR. Unexpected position of the laryngeal mask airway. Anaesthesia 1991;46:592. [6] Ball AJ. Laryngeal mask misplacement — a nonproblem. Anesth Analg 1995;81:204.
Causes of airway obstruction during cuffed oropharyngeal airway use N. Yahagi *, M. Kono, M. Kitahara, K. Watanabe, Y. Fujiwara, Y. Asakawa, J. Katagiri, M. Sha, A. Ohmura Department of Anaesthesiology, Teikyo Uni6ersity Mizonokuchi Hospital, 213 -8507 Kanagawa, Japan Received 1 February 2000; received in revised form 6 July 2000; accepted 6 July 2000
Abstract This study investigated the cause for needing airway maneuvers to maintain a patent airway during the use of cuffed oropharyngeal airway (COPA). Twenty adult patients (29.4 9 6.8 years-old, ASA 1 – 2) scheduled for minor gynecological surgery who required brief manipulations of the airway despite COPA use following the manufacture’s guidelines, were enrolled in this study. To obtain airway patency, 15 patients required only the head-tilt maneuver. In eight of the 15 patients, the laryngeal inlet was opened partially (n=4) or completely (n =4). Despite lifting the epiglottis, the laryngeal inlet was incomplete at the level of pharyngeal view. The patency of the laryngeal inlet was decided by the extent of the distance between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone. In the other seven patients, the head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet. Five patients required both the jaw-thrust and head-tilt maneuver. Of these patients lifting the epiglottis was incomplete in three and the laryngeal inlet was partially collapsed in one even after the airway manipulations. The airways in these three patients, however, became patent after manipulations despite the persisting partial obstruction. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Hyoid bone; Laryngeal inlet; Equipment; Cuffed oropharyngeal airway; Bronchofiberscope; Manipulations; Head tilt; Jaw thrust
Resumo Este estudo investiga as causas de obstruc¸a˜o da via ae´rea e a necessidade de manobras de desobstruc¸a˜o durante a utilizac¸a˜o da via ae´ra orofarı´ngea com cuff (VAOF com cuff). Foram incluı´dos neste estudo 20 adultos (29.4 9 6.8 anos; ASA 1-2), submetidos a cirurgia ginecolo´gica minor e que necessitaram de manobras simples para manter a permeabilidade da via ae´rea durante a utilizac¸a˜o de VAOF com cuff, segundo as recomendac¸o˜es do fabricante. Em 15 doentes a obstruc¸a˜o resolveu com hiperextenc¸a˜o da cabec¸a. Em oito dos doentes a abertura da laringe foi parcial (n =4) ou total (n= 4). Apesar da elevac¸a˜o de epiglote, a abertura da laringe era incomplete quando observada da faringe. Em todos os casos a causa da obstruc¸a˜o foi investigada por fibroscopia, e a pateˆncia da fenda glo´tica medida pela distaˆncia entre a parede farı´ngea posterior e a prega glosso-epiglo´tica formada pelo osso hioide. Nos doentes do primeiro grupo a hiperextensa˜o da cabec¸a permeabilizou completamente a via ae´rea em apenas 7. Cinco dos doentes necessitaram de hiperextensa˜o da cabec¸a e subluxac¸a˜o da mandı´bula. Em treˆs destes a elevac¸a˜o da epiglote foi incompleta em treˆs e num deles a fenda glo´tica estava incompletamente aberta mesmo depois da manipulac¸a˜o da via ae´rea. Contudo a via ae´rea ficou permea´vel em todos os treˆs a seguir a´ manipulac¸a˜o da via ae´rea. © 2001 Elsevier Science Ireland Ltd. Todos os direitos reservados. © 2001 Elsevier Science Ireland Ltd. Todos os direitos reservados. Pala6ras cha6e: Osso hio´ide; Fenda glo´tica; Via orofarı´ngea com ‘‘cuff’’; Broncofibroscopia; Manipulaço˜es; Hiperextensa˜o da cabeça e subluxaçao da mandı´bula
1. Introduction * Corresponding author. Present address: Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. Tel.: +81-358418393; fax: + 81-3-58416481. E-mail address: [email protected] (N. Yahagi).
The cuffed oropharyngeal airway (COPA) is a modified Guedel airway with an inflatable distal cuff, designed to provide ‘hands free’ anesthesia for spontaneous breathing patients by displacing
0300-9572/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0300-9572(00)00258-6
276
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
the base of the tongue, lifting the epiglottis, and sealing the pharynx. In about 30–40% of the patients, however, brief manipulations (head tilt and jaw thrust) were necessary [1–3]. In this study, we investigated the mechanism for when airway manipulation was needed to maintain the airway and how this manipulation relieved the obstruction during COPA use by bronchofiberscopy.
2. Methods This study was approved by the Institutional Review Board (IRB). Twenty adult patients with ASA 1 – 2, 18 – 46 years-old were scheduled for minor gynecological surgery. All patients required underwent anesthesia using a COPA device following the manufacture’s guidelines. Patients were included in the study if they required any airway manipulation during the anesthesia. Patients were excluded from the trial if they were B18 years-old, required surgery in non-spine/non-lithotomy positions, had a known or predicted difficult airway, had respiratory tract pathology, had a sore throat within 10 days, had a body mass index \ 35 kg m − 2, were at risk of aspiration, or were considered otherwise unsuitable for a facemask [2]. The initial COPA size was chosen according to manufacturers instructions by placing the distal tip of the device at the angle of the jaw of a patient in the spine position with the COPA straight up, perpendicular to the floor. When viewed from the side, the tooth/lip guard of the COPA would be about 1 cm ventral to the lip in a properly sized device. Anesthetic management was standardized according to the following protocol: monitoring was applied before induction and included electrocardiograph, pulse oximeter, gas analyzer, and noninvasive blood pressure monitor. All patients were allowed to breathe spontaneously. Anesthesia was induced with the patient in the supine position with the head on a standard pillow. Sedation with pentazocine 0.03 mg kg − 1 and oxygen at a dose of 6 l min − 1 were administered. Anesthesia was induced with intravenous administration of propofol 2.5 –3 mg kg − 1 and maintained with 66% nitrous oxide, 33% oxygen and 1–2% sevoflurane. Facemask ventilation was commenced and continued for at least 30 s until conditions were suitable for insertion of the COPA.
Anesthesiologists were instructed to insert and fix the devices according to the manufacturer’s instructions. The device was connected to a circle breathing system, and the cuff was inflated to achieve a good seal or until the maximal recommended inflation volume was reached. An effective airway was judged by thoracoabdominal movement, a square wave capnograph trace, an oropharyngeal leak pressure \10 cm H2O, and maintenance of SpO2 \90%. All patients included in the study were those requiring airway intervention. Minor airway interventions included adjusting the head/neck position, or device adjustments, such as changing depth of insertion or adjusting the cuff volume of the COPA. Major airway interventions required the application of the jaw lift or changing the device size. Patients underwent manually assisted breathing (MAB) until spontaneous breathing (SB) resumed. During the MAB phase, an oropharyngeal leak test was performed by closing the expiratory valve of the circuit at a fixed gas flow of 6 l min − 1 and noting the airway pressure at which gas started to leak into the mouth (oropharyngeal leak pressure) [2]. Bronchofiberscopical (Olympus 3C-20, OD 3.6 mm or D-BASE Japan Easyscope SMS-ES1, OD 3.6 mm) assessment of the airway was made via the COPA device at two points, immediately proximal to the orifice of the COPA for a view of the base of the tongue and the larynx (pharyngeal view) and at the level of the epiglottis (laryngeal view) for assessment of the laryngeal inlet.
3. Results Table 1 shows demographic details of the patients. All 20 patients showed obstruction of the larynx by the sagged tongue base before airway manipulations despite the properly positioned distal orifice of the COPA (Fig. 1). In all 20 patients, the distal orifice of the COPA was situated very close to the top margin of the epiglottis and the Table 1 Demographic data of the patientsa Age Weight Height Size of COPA
a
Values are mean 9 S.D.
29.49 6.8 years old 51.2 9 5.0 kg 159.2 9 4.9 cm 9.0= 7 patients 10.0=13 patients
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
277
Fig. 1. The larynx was obstructed by the sagging tongue base before airway manipulations, despite the properly positioned distal orifice of COPA. Fig. 2. Top three views (pharyngeal view). Bottom three views (laryngeal view). In the pharyngeal view, epiglottis lifting was still incomplete in eight patients. The opening between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone, was moderate (2A-1) or complete (2B-1). The laryngeal inlet was opened partially (2A-2) or completely (2B-2). In seven patients (2C-1, 2C-2), head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet.
direction of the tip of the COPA bent forward and stuck to the base of the tongue. The laryngeal inlet of all 20 patients was covered with the base of the epiglottis, which was compressed by unlifted hyoid
bone. To obtain airway patency, 15 patients required only the head-tilt maneuver. In eight of the 15 patients, the laryngeal inlet was opened partially (n= 4, Fig. 2A-2) or completely (n=4, Fig.
278
N. Yahagi et al. / Resuscitation 48 (2001) 275–278
2B-2). Despite lifting the epiglottis, the laryngeal inlet was obstructed at the pharyngeal view (Fig. 2A-1, Fig. 2B-1). The patency of the laryngeal inlet was decided by the extent of the distance between the posterior pharyngeal wall and the lateral glossoepiglottic fold, which was made by hyoid bone (Fig. 2A and B). In the other 7 patients, head-tilt maneuver elevated the epiglottis and completely opened the laryngeal inlet (Fig. 2C-1, Fig. 2C-2). Five patients required both the jaw-thrust and head-tilt maneuvers. In these patients, lifting the epiglottis was incomplete in three and the laryngeal inlet was partially collapsed in one even after the airway manipulations. The airways in these three patients, however, became patent after manipulations despite the persisting partial obstruction.
4. Discussion The patency of the laryngeal inlet at the laryngeal view was essentially decided by the extent of the lifting of the hyoid bone was made by observing the distance between the posterior pharyngeal wall and the lateral glossopharyngeal fold. In the pharyngeal view whether the epiglottis was lifted or not, did not predict the opening of the laryngeal inlet. This is because of a wide variation exist in the degree of bend of the epiglottis and shape of the epiglottis (concaved, long, or floppy epiglottis). During use of laryngeal mask airway, which lifted hyoid bone, down fold of epiglottis were seen in 13–60% cases with no clinical symptom of airway obstruction [4 – 6]. Airway patency was due to the collapse of the hyoid bone. This caused obstruction of the laryngeal inlet through the tip of the COPA, which was situated just above the top edge of the epiglottis. Tongue was floppy which did not support the hyoid bone and maintain the laryngeal inlet patent. The tension of the hypopharynx may be decided not only by the anatomy but also by the
.
depth of anesthesia. In this study, the anesthetic level was not so different in each patient because the concentration of anesthetics was the same and the evaluation of airway patency was made at the same SB phase (Pet CO2 was similar). A limitation to this study was that we did not measure the anatomical variables which could suggest the characteristics of the airway though all the patients’ pharyngeal condition was Mallampati score 1 or 2. Further studies are needed to evaluate anatomic variability. The shape of the cuff has some room for improvement. The cuff height of the COPA is the same between the minor curvature and the major curvature. In our study, the tip of the COPA device bent forward and stuck to the base of the tongue in all 20 patients with or without minor manipulation. Ideally, the distal end of the minor curvature of the cuff, which should be thicker, might be extended more distally to lift the hyoid bone effectively. In conclusion, the difficulty of maintaining patent airway during COPA use may be in part explained by collapse of the larynx at the level of the hyoid bone.
References [1] Greenberg RS, Brimacombe JR, Berry A, Gouze V, Piantadosi S, Dake EM. A randomized controlled trial comparing the cuffed oropharyngeal airway and the laryngeal mask airway in spontaneously breathing anesthetized adults. Anesthesiology 1998;88:970– 7. [2] Brimacombe JR, Brimacombe JC, Berry AM, et al. A comparison of the laryngeal mask airway and cuffed oropharyngeal airway in anesthetized adult patients. Anesth Analg 1998;87:147– 52. [3] Asai T, Koga T, Jones RM, Stacey M, Latto IP, Vaughan RS. The cuffed oropharyngeal airway. Anaesthesia 1998;53:810– 22. [4] Nandi PR, Nunn JF, Charlesworth CH, Taylor SJ. Radiological study of the laryngeal mask. Eur J Anaesthesiol 1991;4:33– 9. [5] Molloy AR. Unexpected position of the laryngeal mask airway. Anaesthesia 1991;46:592. [6] Ball AJ. Laryngeal mask misplacement — a nonproblem. Anesth Analg 1995;81:204.