Nasopharyngeal airway continuous positive airway pressure: a method to wean from or avoid mechanical ventilation in adults

A simple technique using a nasopharyngeal airway and a continuous positive airway pressure circuit has proved an effective alternative to a tight fitting nasal or face mask for delivery of continuous positive airway pressure. Nasal trauma, discomfort and mouth breathing are the main disadvantages.     

Evaluation of ejectors using the venturi effect for a continuous positive airway pressure system without compressed air

The purpose of this study is to perform a test in the application of the existing ejectors with the continuous positive airway pressure (CPAP) system without compressed air. Four types of ejector (jet mixer, the former and new puritan nebulizer and the deluxe nebulizer) for blending oxygen and room air by the Venturi effect were tested. A decrease of mixed gas flow and an increase of oxygen concentration were observed according to the increase of positive pressure in all systems. The former puritan nebulizer and deluxe nebulizer were found to be unavailable for the CPAP system for high oxygen concentration and low mixed gas flow for the increase of positive pressure. In the system, however, with the new puritan nebulizer and jet mixer, a sufficient mixed gas flow and an appropriate oxygen concentration could be supplied at an adequate positive pressure. The CPAP system using only oxygen was judged as possibly giving availability.(Hayakawa J, Usuda Y, Numata K: Evaluation of ejectors using the Venturi effect for a continuous positive airway pressure system without compressed air. J Anesth 3: 166–171, 1989)     

机械通气治疗连枷胸的临床分析

目的 探讨双水平正压通气（biphasic positive airway pressure，BiPAP）在连枷胸中的治疗作用。方法 将我院1999年1月-2005年3月符合连枷胸条件的43例患者，其中14例采用无创正压通气BiPAP模式作为BiPAP组，另外29例患者采用的机械通气模式为常规的间歇正压通气（intermittent positive pressure ventilation，IPPV），作为IPPV组，比较两组的ICU住院时间、并发症、死亡率，以及24、48、72h的动脉血气中的PO2、PCO2与氧合指数。结果 BiPAP组中在ICU中治疗时间比IPPV组明显缩短，并发症、死亡率少于IPPV组。监测24、48、72h的血气分析，PO2、PCO2、PaO2／FiO2差异无显著性。结论 在连枷胸患者的治疗中，BiPAP的机械通气模式优于IPPV。     

Negative Pressure Pulmonary Edema After Oral and Maxillofacial Surgery

Negative pressure pulmonary edema (NPPE) following upper airway obstruction (UAO) has been reported in several clinical situations. The main cause of NPPE is reported to be increased negative intrathoracic pressure. We present a case of NPPE that occurred after general anesthesia for plate removal after jaw deformity surgery. After completion of the surgery, administration of inhaled anesthetics was stopped and the patient opened his eyes on verbal command. Immediately after extubation, the patient stopped breathing and became cyanotic. Acute UAO following laryngospasm was suspected. Soon after reintubation, pink, frothy fluid came out of the endotracheal tube, and a tentative diagnosis of NPPE was made. Continuous positive airway pressure was applied. In addition, furosemide and dexamethasone were administered. By the next day, the symptoms had almost disappeared.     

Postoperative CPAP and BiPAP use can be safely omitted after laparoscopic Roux-en-Y gastric bypass

BACKGROUND: Obstructive sleep apnea (OSA) is prevalent in the morbidly obese population. The need for routine preoperative testing for OSA has been debated in bariatric surgery publications. Most investigators have advocated the use of continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP) in the postoperative setting; however, others have reported pouch perforations or other gastrointestinal complications as a result of their use. From a review of our experience, we present an algorithm for the safe postoperative treatment of patients with OSA without the use of CPAP or BiPAP. METHODS: From January 2003 to December 2007, 1095 laparoscopic Roux-en-Y gastric bypasses were performed at our institution. Preoperative testing for OSA was not routinely performed. A prospective database was maintained. The data included patient demographics, co-morbidities (including OSA and CPAP/BiPAP use), perioperative events, complications, and follow-up information. Patients with known OSA were not given CPAP/BiPAP after surgery. They were observed in a monitored setting during their inpatient stay, ensuring continuous oxygen saturation of >92%. All patients used patient-controlled analgesia, were trained in the use of incentive spirometry, and ambulated within a few hours of surgery. The outcomes were compared between the OSA patients using preoperative CPAP/BiPAP versus those with OSA without preoperative CPAP/BiPAP versus patients with no history of OSA. RESULTS: A total of 811 patients were included in the study group with no known history of OSA. Of the 284 patients with a confirmed diagnosis of OSA, 144 were CPAP/BiPAP dependent. Statistically significant differences were present in age distribution and gender, with men having greater CPAP/BiPAP dependency. No significant differences were found in body mass index, length of stay, pulmonary complications, or deaths. One pulmonary complication occurred in the OSA, CPAP/BiPAP-dependent group, three in the OSA, non-CPAP group, and six in the no-known OSA group. No anastomotic leaks or deaths occurred in the series. CONCLUSION: Postoperative CPAP/BiPAP can be safely omitted in laparoscopic Roux-en-Y gastric bypass patients with known OSA, provided they are observed in a monitored setting and their pulmonary status is optimized by aggressive incentive spirometry and early ambulation.     

Use of the Inspiron nebuliser during continuous positive airway pressure ventilation

The Inspiron Nebuliser 002305 with air entrainment was assessed as a gas delivery device in a continuous positive airway pressure system. Inspired oxygen concentrations, total gas flows and pressures within the system were measured over a range of settings, with and without positive and expiratory pressure. Inspired oxygen concentrations and total flows were completely disrupted when a positive and expiratory pressure valve was applied, and the system failed to generate continuous positive airway pressure. We would not therefore recommend the Inspiron nebuliser as a gas delivery system for continuous positive airway pressure.     

双相正压通气治疗急性呼吸窘迫综合征

目的探讨双相气道正压(BIPAP)通气模式治疗急性呼吸窘迫综合征(ARDS)患者的疗效及其对血流动力学和气道力学的影响.方法随机将20例ARDS患者分为BIPAP通气模式组(BIPAP组)和间歇正压通气模式组(IPPV组),行机械通气治疗,每组各10例.观察两组血流动力学、血气分析、呼吸力学指标.结果BIPAP组机械通气时间平均为13天,显著低于IPPV组的21天(P＜0.05).BIPAP组患者安定、吗啡和万可松用量显著低于IPPV组(P＜0.05);IPPV组吸气峰压、平台压和呼气末正压均显著高于BIPAP组(P＜0.05).心率、平均动脉压、平均肺动脉压、体循环阻力和心脏指数两组差别无显著性意义(P＞0.05),但IPPV组肺血管阻力显著高于BIPAP组(P＜0.05).两组间动脉血氧分压、二氧化碳分压和pH值差别无显著性意义(P＞0.05),BIPAP组混合静脉血氧分压显著高于IPPV组(P＜0.05).结论BIPAP通气模式人机关系协同性好,能够降低肺血管阻力,增加混合静脉血氧分压,缩短了ARDS治疗的机械通气时间.     

Nasal CPAP reduces systemic blood pressure in patients with obstructive sleep apnoea and mild sleepiness

BACKGROUND: A randomised controlled study was undertaken to examine the effect of nasal continuous positive airway pressure (CPAP) on 24 hour systemic blood pressure (BP) in patients with obstructive sleep apnoea (OSA). METHODS: Patients were fitted with an ambulatory BP measuring device as outpatients during normal activities and recorded for 24 hours before starting therapeutic or subtherapeutic (4 cm H(2)O) CPAP treatment. BP monitoring was repeated before completion of 12 weeks of treatment. The primary end point was the change in 24 hour mean BP. RESULTS: Twenty three of 28 participants in each treatment arm completed the study. There was no significant difference between the two groups in age, body mass index, Epworth Sleepiness Score, apnoea-hypopnoea index, arousal index, and minimum Sao(2). Twenty four patients were hypertensive. The pressure in the therapeutic CPAP group was 10.7 (0.4) cm H(2)O. CPAP usage was 5.1 (0.4) and 2.6 (0.4) hours/night for the therapeutic and subtherapeutic CPAP groups, respectively (p<0.001). After 12 weeks of treatment there were significant differences between the two CPAP groups in mean (SE) changes in 24 hour diastolic BP (-2.4 (1.2) v 1.1 (1.0) mm Hg (95% CI -6.6 to -0.5), p = 0.025); 24 hour mean BP (-2.5 (1.3) v 1.3 (1.1) mm Hg (95% CI -7.2 to -0.2), p = 0.037); sleep time systolic BP (-4.1 (2.1) v 2.2 (1.8) mm Hg (95% CI -11.8 to -0.7), p = 0.028); and sleep time mean BP (-3.6 (1.7) v 1.3 (1.4) mm Hg (95% CI -9.2 to -0.4), p = 0.033). CONCLUSIONS: Compared with subtherapeutic CPAP, 12 weeks of treatment with therapeutic CPAP leads to reductions in 24 hour mean and diastolic BP by 3.8 mm Hg and 3.5 mm Hg, respectively, in mildly sleepy patients with OSA.     

ProSeal laryngeal mask airway in 120 pediatric surgical patients: a prospective evaluation of characteristics and performance

BACKGROUND: The ProSeal LMA (PLMA) has recently been introduced in pediatric sizes (1.5, 2, 2.5, 3). Limited pediatric data have been published. METHODS: After Institutional Review Board (IRB) approval, the PLMA was placed in 120 children aged 4 months to 13 years (5-50 kg). The following data were collected prospectively: induction agent, number of placement attempts (limited to three), placement success or failure, PLMA size, leak pressure, ventilatory pattern [spontaneous (SV) or controlled positive pressure ventilation (PPV)], success or failure of gastric suction tube placement, hypoxemia, dislodgement, laryngospasm, bronchospasm, aspiration, and traumatic placement. RESULTS: The PLMA was easily placed in children with a higher first attempt success rate (94%) than reported for adults. Overall PLMA and gastric tube placement were both 100% successful. Leak pressures were similar to those reported for the PLMA in adults and higher than reported for the Classic LMA in children. No bronchospasm, laryngospasm, hypoxemia, dislodgement, or aspiration occurred. CONCLUSIONS: Although the PLMA can be used with SV or PPV, the higher leak pressure achieved with the PLMA, and the ability to evacuate fluid and air from the stomach suggest that it may be a useful alternative to tracheal intubation for procedures in which PPV is desired in children aged 4 months to 13 years.     

双水平气道正压无创通气用于老年患者全麻恢复期的呼吸支持

目的研究双水平气道正压(BiPAP)通气在老年患者全麻恢复期呼吸支持的可行性。方法30例择期手术的老年患者随机分为BiPAP组与对照组,每组15例。在术前、拔管后、吸氧或无创通气1h后三个时点比较血液动力学、动脉血气分析参数和呼吸动力学指标。结果两组患者血液动力学的各项指标在各时点差异无显著意义;BiPAP组无创通气1h后PaCO2较拔管后降低,与对照组吸氧1h后比PaCO2低;拔管后两组患者PaO2较术前降低,BiPAP组吸氧1h可提高PaO2。BiPAP无创通气1h后,VTi、VE、Cdyn升高,RAWm降低;而对照组吸氧1h后较拔管后无明显改善。结论老年患者短期BiPAP面罩支持无创通气耐受性好,对血液动力学无明显影响,可以改善通气和氧合,降低气道阻力,提高肺顺应性。     

食管引流型喉罩间歇正压通气时头前屈位对气道密封压的影响

Objective To evaluate the influence of head anteflexion on airway sealing pressure during intermittent positive pressure ventilation(IPPV) with ProSeal laryngeal mask airway (PLMA) with an esophageal vent.Methods Fifty ASA Ⅰ or Ⅱ patients (20 males and 30 females), aged 18-51 ye are, weighing 50-70 kg and scheduled for elective plastic surgery under general anesthesia, were enrolled in this study. Anesthesia was induced with fentanyl 2 μg/kg, propofol 2 μg/kg and vecuromium 0.1 mg/kg. PLMA with an esophageal vent was inserted at 2 min after intravenous vecuronium injection.The airway sealing pressure, the anatomic position of the cuff and the efficacy of positive pressure ventilation were checked in the neutral and anteflexed head positions with the cuff deflated and inflated to an intracuff pressure of 60 cm H2 O, respectively.Results The lungs were better ventilated in the head anteflexion position than in the head neutral position whether the cuff was deflated or inflated. There was no significant difference in the volume of air required to achieve an intracuff pressure of 60 cm H2O between the two head positions ( P＞ 0.05). The airway seating pressure increased from (27 ± 6) cm H2O in the head neutral position to (33 ± 6) cm H2O in the head anteflexion position, with no significant difference between them ( P＞ 0.05). The expired tidal volume and the peak inspiratory pressure during IPPV were (496 ± 81 ) ml and (14.3 ± 1.9) cm H2O respectively in the head neutral position and (496 ± 81 ) ml and ( 14.5 ± 2.1 )cm H2O respectively in the head anteflexion position.Conclusion Head anteflexion can significantly improve airway sealing but does not affect the anatomic position of the cuff.Appropriate head anteflexion is a simple and effective way to improve IPPV when the airway sealing pressure is inadequate in the head neutral position.     

The effect of positive airway pressure during pre-oxygenation and induction of anaesthesia upon duration of non-hypoxic apnoea

Positive end-expiratory pressure (PEEP) applied during induction of anaesthesia may prevent atelectasis formation in the lungs. This may increase the duration of non-hypoxic apnoea by increasing the functional residual capacity. We studied the benefit of PEEP applied during the induction of anaesthesia on the duration of apnoea until the SpO2 reached 90%. Forty ASA I-II patients were randomly allocated to one of two groups. In the PEEP group (n = 20) patients were pre-oxygenated using 100% O2 administered using a CPAP device (6 cmH2O) for 5 min. Following induction of anaesthesia, patients were mechanically ventilated (PEEP 6 cm H2O) for a further 5 min. In the ZEEP group (n = 20), no CPAP or PEEP was used. The duration of apnoea until SpO2 reached 90% was measured. Non-hypoxic apnoea duration was longer in the PEEP group compared to ZEEP group (599 +/- 135 s vs. 470 +/- 150 s, p = 0.007). We conclude that the application of positive airway pressure during induction of anaesthesia in adults prolongs the non-hypoxic apnoea duration by > 2 min.     

The ProSeal laryngeal mask airway in children

BACKGROUND: The ProSeal (PLMA) is a new laryngeal mask device with a modified cuff to improve the seal and a drain tube to provide access to the gastrointestinal tract. We assessed the performance of the size 2 (which has no dorsal cuff) and size 3 (which has a dorsal cuff) in terms of insertion success, efficacy of seal, tidal volume, gas exchange, fiberoptic position, gastric tube placement and frequency of problems. METHODS: Eighty children undergoing minor surgery were studied (n = 40, size 2 PLMA, weight 10-25 kg; n = 40, size 3 PLMA, weight >25-50 kg). Induction was with remifentanil and propofol. Insertion was with the introducer tool and by experienced users. Maintenance was with propofol or sevoflurane and pressure controlled ventilation. RESULTS: The first-time and overall insertion success rate was 84 and 100%, respectively. Oropharyngeal leak pressure was 31 +/- 5 cmH2O. There were no gastric or drain tube air leaks. Tidal volume and gas exchange was adequate in all patients, other than two brief episodes of hypoxia because of airway reflex activation. The vocal cords and epiglottis were visible in 99 and 80%, respectively, via the airway tube. The first-time and overall insertion success rate for gastric tube insertion was 87 and 100%, respectively. During maintenance, the PLMA was removed in one patient with airway reflex activation and another required epinephrine for bronchospasm. There were no differences in performance between the sizes 2 and 3 PLMA. CONCLUSION: The PLMA is an effective airway device in children and isolates the glottis from the esophagus when correctly positioned. Despite the lack of a dorsal cuff, the performance of the size 2 was similar to the size 3 PLMA in the age groups tested.     

Estudio multicéntrico observacional de la mascarilla Ambu® AuraGain® en pacientes adultos

PurposeThe main objective of this study was to evaluate the performance of the Ambu? AuraGain? device by determining its main parameters of use and complications.MethodsA total of 250 adult ASA physical status i to iii patients from five hospitals in Spain who received general anaesthesia with a supraglottic airway (SGA) device were enrolled in this study.ResultsThe primary outcome was analysed for 244 patients and a median OLP of 32 cm H2O (IQR 28-36 cm H2O) was obtained. Insertion was achieved at first attempt in 85% of cases, and overall in 98% of cases, in a median time of 15 s (12-22.5). We applied manoeuvres in 61% of patients to facilitate the process. Ventilation was effective in 97.2% of the interventions (95% CI 0.99-0.94) throughout the procedure. Insertion of the gastric tube was easily performed in 99.6% of the patients, and the vocal cords were viewed by fibrobronchoscopy in 96.3% of cases. Logistic regression analysis identified the use of sizes smaller than those recommended as a risk factor for low OLP (< 25 cm H2O). The main complication recorded was the presence of blood when withdrawing the SGA device (15%).ConclusionsOur results confirm that the use of AuraGain allows airway management in a reliable and effective way achieving high OLP and low incidence of associated complications, establishing it as a useful alternative in the routine clinical setting of anaesthesiologists. AuraGain performance was consistent in all five centres.     

Changes in respiratory pattern during continuous positive airway pressure in infants after cardiac surgery

Purpose Spontaneous breathing trials are commonly used in adults to enable smooth weaning from mechanical ventilation. However, few investigations have examined spontaneous breathing tests in infants. We investigated how respiratory patterns of infants changed during continuous positive airway pressure (CPAP) and whether successful extubation followed CPAP.Methods Fifty-one consecutive post—cardiac surgery infants satisfied the following weaning criteria: stable hemodynamics, pH > 7.30, tidal volume > 5ml·kg^–1, and respiratory rate < 50 breaths·min^–1 with pressure control of 10–16cm H₂O. We applied CPAP of 3cm H₂O for 30min to these 51 infants. During CPAP, tidal volume, respiratory rate, and arterial blood gases were measured. CPAP was terminated if the patient showed a sustained increase or decrease in heart rate or blood pressure (>20%), a decrease in arterial oxygen saturation (>5%), agitation, or diaphoresis. After the completion of CPAP, tracheal extubation was performed. We considered extubation successful if no reintubation was required in the ensuing 48h.Results Although hemodynamic and ventilatory variables were unstable for the first 5min, they stabilized after 10min of CPAP. Fifty infants completed the CPAP trial safely. Of these, 46 (92%) underwent successful extubation after the CPAP trial. The failure group (4 infants) showed lower pH, higher arterial carbon dioxide tension, and more rapid shallow breathing during CPAP than the success group.Conclusion After cardiac surgery, when infants recovered stable hemodynamics and spontaneous breathing, the ventilatory pattern and hemodynamics became stable after 10min of CPAP. Ninety-two percent of the patients were successfully extubated following a 30-min CPAP trial.