External fixation of endotracheal tubes while skin grafting severe burns of the face.

The use of an external cranial device for endotracheal tube fixation can prevent mechanical dislodgement of skin grafts and permit easy access while one is operating on extensive burns of the face.     

Effects of helium-oxygen mixtures on endotracheal tubes: an in vitro study

QUESTION: To determine flow pattern and critical Reynolds numbers in endotracheal tubes submitted to different helium-oxygen mixtures under laboratory conditions. MATERIALS AND METHODS: Flow-pressure relationships were performed for seven endotracheal tubes (rectilinear position, entry length applied) with distal end open to atmosphere (predicted internal diameters: 6-9 mm). Nine helium-oxygen mixtures were tested, with FIHe varying from zero to 0.78 (increment: 10%). Nine flows were tested, with rates varying from 0.25 to 1.60 l s(-1) (increment: 0.15 l s(-1)). Gas flow resistance was calculated, and for each endotracheal tube, a Moody diagram was realised. Flow regime and critical Reynolds numbers were then determined (fully established laminar, nonestablished laminar, smooth turbulent, or rough). RESULTS: Even low concentration of helium in inspiratory mixture reduces endotracheal tubes resistance. Effect is maximal for high flows, small tube and high FIHe. Critical Reynolds numbers are inversely correlated to tube diameter. ANSWER: Under laboratory conditions, flow pattern in endotracheal tubes varies from fully established laminar to rough. Knowledge of the critical Reynolds numbers allows correct application of fluid mechanic formula when studying tube or gaseous mixture effects on respiratory mechanisms.     

A simple laryngoscopic technique for the endotracheal intubation of rabbits

A safe and reliable technique for the endotracheal intubation of rabbits is described. Direct laryngoscopy is followed by intubation of the trachea with a fine catheter, and subsequent advancement of the endotracheal tube over this catheter.     

Endotracheal Anæsthesia

(1) With certain exceptions, endotracheal an?sthesia is the best method for operations on the head and neck and for any other operation in which there may be a difficulty in controlling the patient's air-way. (2) Expiration should be provided for, in endotracheal an?sthesia, either by means of a second tube or by a tube of calibre sufficient to permit to-and-fro respiration. (3) Cocainization of the upper air-passages has decided advantages in endotracheal an?sthesia. (4) "Blind" intubation through the nose renders the method possible in cases where it is impossible to use a speculum. (5) The insufflation method is not specially indicated in abdominal surgery. (6) The routine use of endotracheal an?sthesia in teaching-hospitals for every class of case is detrimental to the production of sound an?sthetic knowledge in students who are likely to become general practitioners.     

Velocity profiles in central airways with endotracheal intubation: a model study

Steady inspiratory velocity profiles were measured at two flow rates in a 3:1 scale model of the human central airways in the presence of five modes of endotracheal intubation. The presence of an orifice or a short endotracheal tube had no significant effect on the velocity profiles distal to the carina. Long endotracheal tubes change the profiles in both main bronchi. A significant peak occurred in the frontal plane near the walls, and the maximum velocity in the airway was almost identical to the endotracheal tube center-line velocity. The flow impinging on the medial wall of the main bronchus was redirected up around the anterior and posterior walls yielding bipeak velocity profiles in the sagittal plane. A tube placed eccentrically in the trachea over the right main bronchus did not alter the velocity profiles in the left main bronchus, suggesting a redirection of flow over the carina into the left lung. An endobronchial tube at the mouth of the right main bronchus did change the shape of the velocity profiles in the left main bronchus. In the left upper lobar bronchus the presence of trachea intubation had no effect on the velocity profiles. However, in the right upper lobar bronchus, the long endotracheal tube flattened the velocity profiles from the strongly skewed ones seen in the absence of the endotracheal inserts. These results not only are relevant to distribution of ventilation and aerosol particle deposition, but also have strong implications in intrapulmonary gas mixing, especially when high-frequency low tidal-volume ventilation is involved.     

Laryngeal perforation during a standard intubation procedure in a pig

Pigs are frequently anaesthetized in animal research settings. Due to the unique laryngeal anatomy, endotracheal intubation is demanding in pigs. Several complications associated with endotracheal intubation have been reported in pigs, but laryngeal perforation following difficult intubation has not been documented so far. The present case report describes laryngeal perforation in a three-month-old pig following difficult intubation.     

Face mask application for calibration of respiratory inductive plethysmography in lambs

Respiratory inductive plethysmography is a non-invasive method of assessing breathing patterns that requires an airway connection for calibration. In previous studies an endotracheal tube was used to establish this connection. We employed a single position graphic calibration technique for gain calculation using a conical face mask in place of the endotracheal tube, thus eliminating the need for sedation and topical anaesthesia. Thirteen studies were completed on seven lambs. Validation of gains was performed by comparing volumes obtained simultaneously by respiratory inductive plethysmography and integrated pneumotachography. Total study time ranged between 5 and 10 min for each calibration procedure. Our results suggest that the conical mask can be used to perform accurate and time-efficient calibration of the respiratory inductive plethysmograph in the spontaneously breathing non-sedated lamb and eliminates the need for endotracheal intubation.     

大鼠气管插管方法学概述

由于大鼠呼吸频率较快、口腔狭小、声门较高,医学实验中气管内插管操作具有较多困难,多年来很多学者对大鼠气管内插管方法进行了大量研究。本文主要对大鼠气管内插管时动物和气管导管的选择、麻醉方式、插管的体位以及各种插管工具和方法等作一简要的综述。     

Effect of air humidity on spinability and transport capacity of canine airway secretions

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T degrees:20 degrees C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m3 air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m3 air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p less than 0.01) lower (range: 0.59-0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70-1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p less than 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.     

Videoendoscopic endotracheal intubation of the rat

Mechanical ventilation is essential to the proper maintenance of anaesthesia in research animals undergoing laparoscopic research investigations with prolonged pneumoperitoneum. Ventilatory assistance is greatly aided by endotracheal intubation, which in rats can be a challenging procedure with a substantial risk of complication. The difficulty of the procedure arises primarily from the limited exposure and access to the laryngeal opening. We describe a simple and safe technique for endotracheal intubation in the rat that permits the introduction of a large-bore tube under direct visualization using equipment commonly found in the endosurgical research setting.     

Molecular analysis of microbial communities in endotracheal tube biofilms

Background

Ventilator-associated pneumonia is the most prevalent acquired infection of patients on intensive care units and is associated with considerable morbidity and mortality. Evidence suggests that an improved understanding of the composition of the biofilm communities that form on endotracheal tubes may result in the development of improved preventative strategies for ventilator-associated pneumonia.

Methodology/Principal Findings

The aim of this study was to characterise microbial biofilms on the inner luminal surface of extubated endotracheal tubes from ICU patients using PCR and molecular profiling. Twenty-four endotracheal tubes were obtained from twenty mechanically ventilated patients. Denaturing gradient gel electrophoresis (DGGE) profiling of 16S rRNA gene amplicons was used to assess the diversity of the bacterial population, together with species specific PCR of key marker oral microorganisms and a quantitative assessment of culturable aerobic bacteria. Analysis of culturable aerobic bacteria revealed a range of colonisation from no growth to 2.1×10⁸ colony forming units (cfu)/cm² of endotracheal tube (mean 1.4×10⁷ cfu/cm²). PCR targeting of specific bacterial species detected the oral bacteria Streptococcus mutans (n = 5) and Porphyromonas gingivalis (n = 5). DGGE profiling of the endotracheal biofilms revealed complex banding patterns containing between 3 and 22 (mean 6) bands per tube, thus demonstrating the marked complexity of the constituent biofilms. Significant inter-patient diversity was evident. The number of DGGE bands detected was not related to total viable microbial counts or the duration of intubation.

Conclusions/Significance

Molecular profiling using DGGE demonstrated considerable biofilm compositional complexity and inter-patient diversity and provides a rapid method for the further study of biofilm composition in longitudinal and interventional studies. The presence of oral microorganisms in endotracheal tube biofilms suggests that these may be important in biofilm development and may provide a therapeutic target for the prevention of ventilator-associated pneumonia.     

The oesophageal obturator airway: a new device in emergency cardiopulmonary resuscitation.

Experience with 29 000 cases in which the oesophageal obturator airway has been used in cardiopulmonary resuscitation indicates its safety, efficacy, and ease of use. Blood gases, fractional inspired oxygen, and pH were measured in 18 patients given both the oesophageal obturator airway and the endotracheal tube; there was no significant difference between the two. The former was found to be inserted more rapidly and reliably; moreover, paramedical staff are quickly trained to use it. It is concluded that the oesophageal obturator airway provides the technique of choice whenever ideal conditions and facilities--and trained staff--for endotracheal intubation are not immediately available.     

Factors influencing mechanical performance of neonatal high-frequency ventilators

Factors influencing the mechanical performance of neonatal high-frequency ventilators of diverse design were assessed under controlled conditions. Each of eight ventilators was coupled to in vitro models of the neonatal respiratory system simulating disease of varying severity. The principal performance characteristics examined were frequency dependence and load dependence of tidal volume delivered, peak inspiratory flow rate, and waveforms of pressure at either end of the endotracheal tube. Despite wide diversity of ventilator designs, including jets, flow interrupters, and oscillators, common features emerged. In almost all devices tidal volume increased with endotracheal tube size, was invariant with respiratory system compliance, and decreased with frequency of oscillation. Peak inspiratory flow rates for a given tidal volume and frequency were smallest in the group of oscillators compared with jets and flow interrupters. Proximal pressure was a poor indicator of distal pressure. These findings suggest that delivered tidal volume may be sensitive to endotracheal tube size and airway patency but relatively insensitive to changes in lung tissue or chest wall mechanical properties. In these regards high-frequency ventilation differs from pressure-limited conventional mechanical ventilation. Comparison of data obtained at different clinical centers using high-frequency ventilators of varying design may be possible by taking these factors into account.     

Complete Thymectomy in Adult Rats with Non-invasive Endotracheal Intubation

Thymectomy in neonatal rodents is an established and reliable procedure for immunological studies. However, in adult rats, complications of hemorrhage and pneumothorax from pleural disruption can result in a significant mortality rate. This protocol is a simple method of rat thymectomy that utilizes a mini-sternotomy and endotracheal intubation. Intubation is accomplished with a non-invasive and easily reproducible method and allows for positive pressure ventilation to prevent pneumothorax and a controlled airway that allows sufficient time for careful thymus dissection to minimize pleural disruption. A 1.5 cm sternal incision decreases contact with mediastinal vessels and pleura, while still providing full visualization of the thymus. Following exposure of the mediastinum, the thymus is removed by blunt dissection under magnification. The pleural space is then sealed by suture closure of the pre-tracheal muscles followed by the application of surgical glue. The thorax is then closed by suture closure of the sternum, followed by suture closure of the skin. All thymectomies were complete as evidenced by immunohistochemical (IHC) staining of mediastinal tissue, and absence of naïve T-cells by flow cytometry, and the procedure had a 96% survival rate. This method is suitable when complete thymectomy with minimal complications is desired for further immunological studies in athymic adult rats.     

Postanesthesia death and suspected peracute endotoxic shock due to Pseudomonas putida in a cynomolgous macaque (Macaca fascicularis)

An adult male cynomolgous macaque (Macaca fascicularis) died suddenly after anesthesia for a positron emission tomography scan. Bacteriologic culture of the mucopurulent secretions recovered from the endotracheal tube yielded heavy growth of Pseudomonas putida, a known endotoxin producer. Histologically, the lungs had severe, diffuse perivascular edema and neutrophils marginating to the endothelium. The sudden death and the pathologic findings were consistent with peracute endotoxic shock. Numerous environmental swab specimens of the surgical suite and equipment were submitted for bacteriologic culture, as were swab specimens of endotracheal secretions from a control animal; however, Pseudomonas putida was not isolated from any specimen. The animal in this report may have carried Pseudomonas putida as a commensal in the oropharynx, and the stress of anesthesia may have resulted in increased sensitivity to the endotoxin.     

Effect of air entrainment on airway pressure during endotracheal gas injection

Turbulent jets in endotracheal tubes induce air entrainment and airway pressure changes. We attempted to understand the physical explanation for these effects, which open up to a wide range of applications in intubated patients. An in vitro study was performed on standard size endotracheal tubes with diameters of 8, 7, and 3 mm and several capillaries molded into the wall (less than 1 mm diam) allowing gas injection at approximately 1-2 cm from the tracheal end of the endotracheal tube. This produced a jet velocity-dependent gain in tracheal pressure (Ptr) during inspiration. Data have been interpreted with a theory, based on the classic momentum theorem, which indicates that the mechanisms involved resemble those of axisymmetrical confined jets: air entrainment by turbulent friction with a longitudinal increase in lateral pressure. The difference with axisymmetrical systems lies in the nonconservation of the total thrust in our system because, secondary to wall friction and to the nonaxial incidence of the jets, only a fraction of the jet momentum flux is transformed into pressure. This suggests faster mixing in the present lateral jet system, as shown by 1) the independence of Ptr on tracheal geometry and 2) the very rapid increase in lateral pressure. The present study supports the idea that pressure changes in the airways, which are potentially beneficial in intubated patients, can be satisfactorily generated by turbulent jets.     

Role of the carotid chemoreceptors in regulation of inspiratory onset

We studied the effect of intermittent tidal breaths of CO2-enriched air (3-9% CO2) on the duration of expiratory time (TE) in five trained dogs, before and after (3 dogs) bilateral surgical denervation of the carotid bodies (CBD). During studies the dogs lay quietly, either awake or in nonrapid-eye-movement sleep, and breathed through a cuffed endotracheal tube inserted via a chronic tracheostomy. Studies were conducted during bilateral blockade of the cervical vagus nerves (VB), achieved by circulating cold alcohol through radiators placed around exteriorized vagal skin loops. Prior to CBD, single breaths of CO2 significantly shortened TE and thus advanced the onset of the subsequent inspiration. Further, the decrease in TE induced by the CO2 stimulus was in direct proportion to the inspired CO2 concentration. Thus 3% CO2 shortened TE by 1.82 +/- 0.93 (SD) s, and 9% CO2 by 3.44 +/- 1.53 s. Changes in TE occurred in the absence of associated changes in either tidal volume or inspiratory time. After CBD, test breaths of CO2 failed to shorten TE during VB. We conclude that the carotid bodies have the ability to mediate changes in the timing of inspiratory onset in response to a transient CO2 stimulus.     

Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs.

Large volume, low pressure endotracheal tube cuffs are claimed to have less deleterious effect on tracheal mucosa than high pressure, low volume cuffs. Low pressure cuffs, however, may easily be overinflated to yield pressures that will exceed capillary perfusion pressure. Various large volume cuffed endotracheal tubes were studied, including Portex Profile, Searle Sensiv, Mallinkrodt Hi-Lo, and Lanz. Tracheal mucosal blood flow in 40 patients undergoing surgery was assessed using an endoscopic photographic technique while varying the cuff inflation pressure. It was found that these cuffs when overpressurised impaired mucosal blood flow. This impairment of tracheal mucosal blood flow is an important factor in tracheal morbidity associated with intubation. Hence it is recommended that a cuff inflation pressure of 30 cm H2O (22 mm Hg) should not be exceeded.     

An alternative method of endotracheal intubation of common marmosets (Callithrix jacchus)

Endotracheal intubation was carried out in 11 common marmosets (Callithrix jacchus). A commercially available tilting stand and a Miller laryngoscope blade were used to visualize the larynx. Anaesthesia was induced with alphaxalone (10.6 ± 1.6 mg/kg intramuscularly, followed by 3.2 ± 1.2 mg/kg intravenously). The diameter of the proximal trachea easily fitted an endotracheal tube made from readily available material (a 12 G 'over the needle' catheter). Once the tip of the endotracheal tube was at the level of the vocal folds, the tube had to be gently rotated through a 180° angle in order to pass through the larynx into the trachea. Assessment of the dimensions of the larynx and trachea, and comparison with external anatomical features of the animals (n = 10) showed that the length of the trachea could be predicted by multiplying the craniosacral length of the marmoset by a factor of 0.42.     

Simplified rat intubation using a new oropharyngeal intubation wedge.

Our new oropharyngeal intubation wedge made from a plastic 3-ml syringe has been used successfully for the expansion of the oropharyngeal cavity and visualization of vocal cords for endotracheal intubation in the rat. All the animals we used tolerated the intubation and ventilation procedures in a series of experiments. After the proper setting of the respirator, vital signs were maintained within normal range. The postmortem examination and measurements in the upper airway confirmed that the endotracheal tube was properly sited and also demonstrated the precise size of the device that should be used. The main advantages of this method include low cost, simplicity, and reliability. Furthermore, because no expensive, elaborate, difficult-to-operate, or hard-to-get special equipment is needed, this technique can be used in every laboratory.