Unexpected Obstruction of a Parker Flex-Tip Endotracheal Tube Caused by Outward Bending of Its Tip: A Case Report.

We report a case of Parker Flex-Tip endotracheal tube obstruction caused by its tip bending outward against the tube lumen. The Parker Flex-Tip tube tip is designed to bend inward to prevent damage to airway structures during intubation. However, when its tip is bent outward, the tube aperture is distorted, shifts against the tracheal wall, and is occluded. Moreover, the cross-sectional area of the openings on the side of the endotracheal tube, the "Murphy's eyes" which are ellipses, decrease because the openings are pulled parallel to their long axis. Outward bending of the tip can obstruct the tube.

Comparison of effectiveness of the piston-pump method versus the pressure-infusor method for rapid infusion of crystalloids: A bench study.

BACKGROUND AND AIMS: The piston-pump method is a simple method for rapid administration of fluids but some problems are unsolved. We compared the effectiveness of using the piston-pump method with that of the pressure-infusor method. METHODS: Twelve anaesthetists were classified randomly into the piston-pump and pressure-infusor groups. They were asked to infuse 500 ml of saline three times successively through a 16-G intravenous cannula as rapidly as possible using a pump with a 50-ml syringe or a pressure-infusor at 300 mmHg. The time taken for infusion and the maximum or minimum pressure in the infusion circuit and substitute vessel were measured. Bacterial culture of the saline infused sterilely was performed to estimate bacterial contamination. RESULTS: The pressure-infusor group led to faster infusion of 500 ml of saline (233 ± 19 s) than the piston-pump group (301 ± 48 s) (P < 0.01). The infusion time at the third attempt (316 ± 43 s) was significantly longer than that at the first attempt (285 ± 53 s) only in the piston-pump group (P < 0.05). The maximum pressure (mmHg) in the circuit was 131 ± 9 and > 200 (P < 0.01) and in the substitute vessel was 5 ± 1 and 17 ± 7 (P < 0.01) in the pressure-infusor and piston-pump groups, respectively. A pressure of <-200 mmHg occurred at all infusion attempts in the piston-pump group. Bacterial contamination was not observed in either group. CONCLUSION: If fluids must be administered rapidly, the pressure-infusor method is more efficient than the piston-pump method because the latter is less effective in infusing fluids rapidly and associated with excessive positive and negative pressure in the infusion circuit.

Bougies as an aid for endotracheal intubation with the Airway Scope: bench and manikin comparison studies.

BACKGROUND: When encountering a difficult airway with an Airway Scope (AWS) a bougie can be inserted into the endotracheal tube in the AWS channel. The angulated tip of the bougie can be guided toward the glottis by rotating it. We tested the ease of rotating bougies (Venn reusable, Boussignac, Portex single-use, and Frova) in an endotracheal tube when placed in the AWS channel. METHODS: Bench study: Seven anesthesiologists inserted each of the four types of bougies into a 7.0 mm endotracheal tube in an AWS channel and rotated the bougie end (side of bougie operated by hand) clockwise or counterclockwise to an angle of 0°-180° in 45° increments. The rotation angle of the bougie tip (tracheal side) was measured for each bougie and the degree of force required to rotate them was examined. Manikin study: Using the same four bougies, the same seven anesthesiologists attempted to intubate a manikin that simulated a difficult airway. Success rate and time required for successful intubation were compared between the four bougies. RESULTS: Bench study: The difference in the rotation angle between the bougie tip and end was significantly larger with Portex single-use and Frova bougies than with Venn reusable and Boussignac bougies (P < 0.01). The rotation angles of the tips of Venn reusable, Boussignac, Portex single-use, and Frova bougies were 145°/123° (clockwise / counterclockwise), 92°/108°, 46°/56°, and 39°/51°, respectively, when their ends were rotated to an angle of 180°. Venn reusable and Boussignac bougies could be rotated in the endotracheal tube by clinically acceptable rotational force. Manikin study: Times to intubation with Venn reusable [25 (SD, 5) s] and Boussignac bougies [35 (6) s] were significantly shorter than with Portex single-use [61 (17) s] and Frova bougies [69 (22) s] (P < 0.01). There were no significant differences in success rate between the four bougies. CONCLUSIONS: Venn reusable and Boussignac bougies are a useful aid for intubation with an AWS. Portex single-use and Frova bougies seem to be less suitable for this technique. Different bougies may be of varying utility when used with an AWS or airway device with an endotracheal tube channel.

Prevention of aspiration of gastric contents during attempt in tracheal intubation in the semi-lateral and lateral positions.

BACKGROUND: Pulmonary aspiration of gastric contents during tracheal intubation is a life-threatening complication in emergency patients. Rapid sequence intubation is commonly performed to prevent aspiration but is not associated with low risk of intubation related complications. Although it has been considered that aspiration can be prevented in the lateral position, few studies have evaluated the ability to prevent aspiration. Moreover, this position is not always a favorable position for tracheal intubation. If aspiration can be prevented in a clinically relevant semi-lateral position, it may be advantageous. We assessed the ability to prevent aspiration in the lateral position and various degrees of the semi-lateral position using a vomiting-regurgitation manikin model. METHODS: A manikin's head was placed in the neutral, simple extension, or sniffing position. The amount of aspirated saline into the bronchi during simulated vomiting was measured at semi-lateral position angles of 0º to 90º in 10º increments. The difference in the vertical height between the mouth corner and the inferior border of the vocal cord was measured radiologically at each semi-lateral position in the three head-neck positions. RESULTS: Pulmonary aspiration was prevented at the ≥70º, ≥80º, and 90º semi-lateral positions in the neutral, simple extension, and sniffing positions, respectively. The mouth was lower than the vocal cord in the semi-lateral position in which aspiration was prevented. CONCLUSION: The lateral or excessive semi-lateral position was necessary to protect the lung from aspiration in the head-neck positions commonly used for tracheal intubation. Prevention of aspiration was difficult within clinically relevant semi-lateral positions.

Prevention of aspiration of gastric contents during attempt in tracheal intubation in the semi-lateral and lateral positions / 世界急诊医学杂志（英文）

@#BACKGROUND: Pulmonary aspiration of gastric contents during tracheal intubation is a life-threatening complication in emergency patients. Rapid sequence intubation is commonly performed to prevent aspiration but is not associated with low risk of intubation related complications. Although it has been considered that aspiration can be prevented in the lateral position, few studies have evaluated the ability to prevent aspiration. Moreover, this position is not always a favorable position for tracheal intubation. If aspiration can be prevented in a clinically relevant semi-lateral position, it may be advantageous. We assessed the ability to prevent aspiration in the lateral position and various degrees of the semi-lateral position using a vomiting–regurgitation manikin model. METHODS: A manikin's head was placed in the neutral, simple extension, or sniffing position. The amount of aspirated saline into the bronchi during simulated vomiting was measured at semi-lateral position angles of 0o to 90o in 10o increments. The difference in the vertical height between the mouth corner and the inferior border of the vocal cord was measured radiologically at each semi-lateral position in the three head-neck positions. RESULTS: Pulmonary aspiration was prevented at the ≥70o, ≥80o, and 90o semi-lateral positions in the neutral, simple extension, and sniffing positions, respectively. The mouth was lower than the vocal cord in the semi-lateral position in which aspiration was prevented. CONCLUSION: The lateral or excessive semi-lateral position was necessary to protect the lung from aspiration in the head-neck positions commonly used for tracheal intubation. Prevention of aspiration was difficult within clinically relevant semi-lateral positions.

[Airway Obstruction Caused by Heat and Moisture Exchange Filter Used during General Anesthesia: A Case Report and an In Vitro Study].

BACKGROUND: A previously healthy 54-year-old woman underwent a resection of the acoustic tumor. Following induction of general anesthesia and tracheal intubation, volume-controlled ventilation was started and the patient was placed in the left park bench position. The heat and moisture exchange filter (HMEF) was placed within the ventilatory circuit and positioned below the patient's head to avoid unintentional extubation. Six hours after the start of surgery, peak inspiratory pressure gradually rose, and 2 hours later ventilation of the patient's lung became increasingly difficult. When the HMEF was replaced, normal breathing was promptly restored. METHODS: We reproduced this scenario with a similar HMEF under the same ventilator settings by adding 0-8 g of normal saline into the HMEF housing, and measured the inspiratory pressure and tidal volume across the HMEF. RESULTS: When instilling 4 g of saline, an increase in inspiratory pressure occurred. CONCLUSIONS: This case shows a potential risk of unexpectedly early occurrence of obstruction of the HMEF due to accumulation of condensed water within the device when the HMEF was positioned below the patient's head. We recommend selection of the appropriate HMEF and suitable mounting to avoid this problem.

[Monitoring of Somatosensory Evoked Potentials during Foramen Magnum Decompression of Chiari Malformation Type I Complicated with Syringomyelia: A Report of Two Cases].

Few reports exist on anesthetic management for foramen magnum decompression (FMD) of Chiari malformation type I (CM I) complicated with syringomyelia. In two such cases we monitored somatosensory evoked potentials (SEP). Case 1 : A 40-year-old woman presented with occipital headache and nuchal pain for 2 months; numbness and muscular weakness of bilateral upper limbs for a month. Magnetic resonance imaging (MRI) scan showed CM I complicated with syringomyelia. Case 2 : A 32-year-old man presented with numbness and muscular weakness of bilateral upper limbs for 5 months; numbness and muscular weakness of lower limbs for 2 months. MRI scan showed CM I complicated with syringomyelia. They underwent FMD. In both cases, general anesthesia was induced with remifentanil, propofol and rocuronium, and was maintained with oxygen, air, remifentanil and propofol. Moreover, we monitored SEP. Their operative courses were uneventful. In case 1, SEP latency became shorter after FMD. Her preoperative neurologic symptoms disappeared on first postoperative day. In contrast there was no change of SEP latency after FMD in case 2. His preoperative neurologic symptoms showed no change on fifth postoperative day. SEP monitoring may be a useful index for prediction of early recovery of neurologic symptoms after FMD.

[Head extension during laryngoscopy for obtaining a best glottic view: comparison of the McGrath and Macintosh laryngoscopes].

BACKGROUND: Camera eye in the McGrath video-laryngoscope blade is located closer to the larynx, which may allow reduction of the head-neck movement during laryngoscopy compared with a conventional laryngoscope. We compared the degree of head extension during laryngoscopy with McGrath laryngoscope and that with Macintosh laryngoscope. METHODS: Fifty patients without cervical spine abnormality were randomized into two groups: laryngoscopies with Macintosh laryngoscope and that with McGrath laryngoscope. Each patient wearing goggles mounted with a goniometer lay supine with the head in the neutral position. After general anesthesia and muscle relaxation were obtained an experienced anesthesiologist obtained the best glottic view using either laryngoscope, and change in the angle of goggles (head extension angle) during laryngoscopy was measured. In addition, we compared the head extension angle with extension angle of the cervical spine between the occiput and the fourth cervical vertebra (C0-4) measured radiologically in 7 healthy volunteers. RESULTS: Head extension angles with Macintosh and McGrath laryngoscopes were 18.2 ± 4.3 degrees and 9.6 ± 2.7 degrees, respectively (P < 0.0001). There was a strong relationship between head extension angle and C0-4 extension angle measured radiologically in the volunteers (r = 0.92, P < 0.0001). CONCLUSIONS: The McGrath laryngoscope may be a reasonable technique of choice for intubation when minimal cervical spine movement is indispensable because of reduction of head extension during laryngoscopy compared with the conventional laryngoscopy.

Combining head-neck position and head-down tilt to prevent pulmonary aspiration of gastric contents during induction of anaesthesia: a volunteer and manikin study.

CONTEXT: Although a life-threatening complication, pulmonary aspiration of gastric contents caused by vomiting or regurgitation during induction of anaesthesia cannot be prevented. It may be prevented if the mouth is placed more inferiorly than the larynx and tracheal bifurcation by the use of head-down tilt and head-neck positioning. OBJECTIVE: We aimed to determine the head-down tilt required to prevent aspiration in the neutral, simple extension, sniffing and full cervical spine extension (Sellick) positions and to investigate the relationship between pulmonary aspiration and the vertical height of the mouth, larynx and tracheal bifurcation. DESIGN: Observational study. SETTING: Operating theatre at Nippon Steel Yawata Memorial Hospital. PATIENTS: Manikins with coloured fluid in the oesophagus and 30 adult volunteers. INTERVENTIONS: Use of head-down tilt between 0° and 50° in 5° increments in four head-neck positions (neutral, simple extension, sniffing and Sellick). MAIN OUTCOME MEASURES: Aspiration of oesophageal contents (coloured fluid) from the oesophagus into the trachea and bronchi. Measurement of the mouth-arytenoid angle (manikin and volunteers) and the mouth-carina angle (manikin). RESULTS: The head-down tilts required to protect both the trachea and bronchi from aspiration were 45°, 35° and 10° in the neutral, simple extension and Sellick positions, respectively, which coincided with the mouth-arytenoid angle in those positions. The maximum tilt used in this study was not adequate to prevent aspiration in the sniffing position. The head-down tilt required to level the mouth with the tracheal bifurcation (mouth-carina angle) protected the bronchi from aspiration but not the trachea. CONCLUSION: A head-down tilt equal to the mouth-arytenoid angle (levelling the mouth with the larynx) was necessary to completely prevent aspiration. This angle of tilt was within clinically relevant ranges only with the Sellick position.

Efficacy of the Airway Scope on tracheal intubation in the lateral position: comparison with the Macintosh laryngoscope.

BACKGROUND: The Airway Scope (AWS) may become a rescue airway device to secure the airway in the lateral position. We evaluated the efficacy of the AWS on tracheal intubation in patients in this position in comparison with the Macintosh laryngoscope. METHODS: Seventy patients scheduled for surgery in the lateral position under general anaesthesia with tracheal intubation were randomised into two groups: intubation with the Macintosh laryngoscope and that with the AWS. After general anaesthesia and muscle relaxation, experienced anaesthetists performed laryngoscopy and intubation using either laryngoscope in the right or left lateral position. Laryngoscopic view, intubation time, intubation difficulty scale score and success rate of tracheal intubation (within 60 s) were recorded and compared between intubation with the Macintosh laryngoscope and that with the AWS. RESULTS: In the lateral position, the laryngoscopic view with the AWS was significantly better than that with the Macintosh laryngoscope (P < 0.01). Tracheal intubation was successful at the first attempt with the AWS in all patients and with the Macintosh laryngoscope in 85.3% of patients (P < 0.05). The median times to intubation with the AWS and with the Macintosh laryngoscope were 14 (interquartile range, 9-19) s and 29 (20-31) s, respectively (P < 0.01). Also, the AWS significantly reduced the intubation difficulty scale score compared with the Macintosh laryngoscope (P < 0.01). CONCLUSION: In the situation in which securing the airway in the lateral position is required, the AWS is more effective than the Macintosh laryngoscope.

[Efficacy of bougie in difficult intubation with the Airway Scope caused by inability to lift the epiglottis directly].

BACKGROUND: There are some disadvantages of the Airway Scope (AWS), and the most crucial one is that the AWS has only one fixed-size AWS blade. When the blade is too short to reach beneath the epiglottis and to lift it directly, an endotracheal tube hits the epiglottis and cannot be advanced into the glottic aperture even when it is visible. A bougie may solve this difficulty because its angulated tip can be controlled in a desired direction. Therefore, we examined the efficacy of the bougie on this problem. METHODS: Forty patients were randomly classified into two groups: intubation with only the AWS, and with the AWS and the bougie. After general anesthesia and muscle relaxation, the AWS blade tip was positioned in the vallecula, the glottis was fully exposed, and intubation using the AWS with or without a bougie was performed. Success rate and time to intubation were compared in both groups. RESULTS: Success rate was 13/20 in intubation with only the AWS and 19/20 in intubation with the AWS and the bougie (P<0.05). Median intubation time was reduced from 48 sec without the bougie to 29 sec with the bougie (P<0.01). CONCLUSIONS: Use of the bougie was useful for difficult intubation with the AWS caused by inability to lift the epiglottis directly.

Approach combining the airway scope and the bougie for minimizing movement of the cervical spine during endotracheal intubation.

BACKGROUND: The Airway Scope (AWS, AWS-S100; Hoya-Pentax, Tokyo, Japan), a recently introduced video laryngoscope, has been reported to reduce movement of the cervical spine during intubation attempts in comparison with conventional laryngoscopes. Use of the bougie as an aid for the AWS may cause further reduction. The authors compared cervical spine movement during intubation with the AWS with and without a bougie. METHODS: Thirty patients without cervical spine abnormality were randomized into two groups: intubation with AWS only and intubation with the AWS and the bougie. The cervical spine motion between the occiput (C0) and the fourth cervical vertebra (C4) was observed fluoroscopically, and change in movement between adjacent vertebrae created by each intubation method was compared. Time to intubation was also measured. RESULTS: Laryngoscopy with the AWS produced extension of the cervical spine segments assessed (C0-4). Median extension angle of the C0-4 during intubation using the AWS was reduced from 16.0 degrees without the bougie to 6.5 degrees with the bougie (P < 0.01). There was no significant difference in time to intubation between them. CONCLUSIONS: Use of the bougie resulted in significantly reduced extension of the cervical spine during intubation attempt with the AWS in patients with a normal cervical spine.