Pharyngeal pouch as a cause of difficult intubation

The presence of a lateral pharyngeal pouch may cause difficulty in recognising the glottis when awake intubation is undertaken. This is mainly because the orifice may open and close during phonation and therefore be mistaken for the glottis. A case is described and some aspects of relevance to the anaesthetist are discussed.     

Diagnosis of clinically unrecognized endobronchial intubation in paediatric anaesthesia: which is more sensitive,pulse oximetry or capnography?

In a prospective, randomized, single-blind study of combined pulse oximetry and capnography in 196 children whose anaesthetic was managed by endotracheal intubation we observed 10 patients with 14 episodes of endobronchial intubation (EBI). Pulse oximetry provided the first diagnostic clue in 13 events; the one event first diagnosed by capnography was also accompanied by oxygen desaturation. Two EBI occurred immediately after the initial intubation (‘primary’ EBI). Twelve episodes of EBI in eight patients occurred after correct initial endotracheal tube position (‘secondary’ EBI). EBI gave rise to eight episodes of ‘minor’ desaturation (oxygen saturation (Spo₂) ≤ 95%≥ 60 s); four resulted in ‘major’ desaturation (Spo₂≤ 85% for 30 s). Only three EBI events produced clinical signs or symptoms. Seven patients were less than 1 year; EBI was not, however, related to age. A high frequency (5.1%) of clinically unrecognized EBI was found in infants and children. A persistent yet small, reduction in oxygen saturation provided the early evidence of secondary EBI in the majority of cases. Clinical signs and capnography proved least effective in the early diagnosis of secondary EBI.     

Endotracheal suctioning: an example of the problems of relevance and rigour in clinical research

• ? Endotracheal suctioning is a routine but potentially dangerous procedure. The literature documenting approaches to minimizing the cardiopulmonary complications of endotracheal suctioning is reviewed. Hyperoxygenation, hyperventilation, hyperinflation and the use of adaptors are all evaluated. The effects of endotracheal suctioning on haemodynamics and oxygen transport are also examined. The traditional dualist approach to the respiratory and cardiovascular systems is contrasted with the recent emphasis on oxygen transport by the cardiopulmonary system.
• ? The trade-off between the rigour of laboratory studies (which can be well controlled but are difficult to generalize) and the relevance of clinical research (which is more easily generalized but which often lacks internal validity) is discussed. Although research studies have become both more methodologically and conceptually sophisticated, definitive recommendations for a safe and effective suctioning procedure still remain elusive.

     

颅通定减轻气管插管反应的研究

目的　观察颅通定减轻气管插管反应的效果。方法　选择 4 8例全麻患者 (ASAⅠ～Ⅱ级 ) ,随机分为 2组 ,A组诱导前静注颅通定 1mg/kg,B组诱导前静注生理盐水 2mL ,监测两组患者插管前后血压、心率等指标的变化。结果　A组在喉镜窥视及插管后 1min、3min、5min时SBP ,MAP ,DBP和HR均明显低于B组。结论　颅通定能有效减轻气管插管反应。     

Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions

BACKGROUND: The aim of this study was to evaluate and compare information about lung mechanics obtained by dynamic pressure/volume loops based on Y-piece and intratracheal airway pressure. METHODS: Airway pressure was measured simultaneously at the Y-piece and trachea. Flow/tidal volume was measured by sidestream spirometry at the Y-piece. The effect of an intraluminal catheter in the tube was evaluated in a lung model. Ten adults with acute lung injury and mechanical ventilation were studied. Measurements were performed during volume-(VC) and pressure-controlled (PC) ventilation at different ventilator settings. RESULTS: Lung model: There was a statistically significant difference (P<0.001) between trachea and Y-piece pressure/volume loop areas during both VC and PC ventilation. The ratio trachea area/Y-piece area decreased with increased endotracheal tube resistance (r=0.96). Patients: The difference between trachea and Y-piece P/V-loops was statistically significant at all 21 ventilatory settings (P<0.05-0.001). The tracheal loop revealed clearly intrinsic PEEP and lowered compliance during overinflation, which was difficult or impossible to see in the Y-piece pressure/volume loop. CONCLUSION: By measuring airway pressure at the trachea the effect of endotracheal tube resistance during inspiration is excluded while it is included during expiration, yielding correct end-points of inspiration and expiration. This makes it possible to calculate accurately total compliance of the respiratory system during dynamic conditions. By monitoring of airway pressure in the trachea, respiratory mechanics can be assessed more accurately and ventilatory settings adjusted to attenuate ventilator induced lung injury.     

Two cases of bronchospasm during operation in a prone position

Key words  bronchospasm - prone position - aerosol via endotracheal tube     

全身麻醉诱导用药对眼内压的影响

目的 观察全麻诱导气管插管时异丙酚、硫喷妥钠及乙咪酯对眼内压（IOP）的影响以及异丙酚与氯胺酮合用时的相互影响。方法 50例ASAⅠ-Ⅱ组择期非眼科手术患者,随机分为硫喷妥钠（SP）组、乙咪酯（EM）组、异丙酚（P）组、氯胺酮－异丙酚（K－P）组、异丙酚－氯胺酮（P－K）组。分别于诱导前、注药后、插管前、插管后1、2、5分钟用Schiotz眼压计测定IOP,同时监测平均动脉压（MAP）和心率（HR）。结果 IOP变化 P组从注药后到插管后5分钟显著低于诱导前（P＜0．05）,SP组与EM组注药后各时点有降低趋势（P＞0．05）。K－P组注药后IOP短暂升高,但于插管前迅速下降,P－K组变化趋势与P组基本一致。P、SP、SM组注药后各时点较诱导前下降的百分率分别平均为－41．28％、－12．13％和－10．62％。MAP变化趋势与IOP基本一致,HR的变化组内组间均无显著差异（P＞0．05）。结论 异丙酚在全身麻醉诱导气管插管期间降低IOP的作用较强而稳定;硫喷妥钠、乙咪酯降低IOP的作用较弱。异丙酚与氯胺酮合用可预防及减轻各自的副作用并互补麻醉效果。