Lumen Of Endotracheal Tube Research Articles

Antimicrobial Susceptibility Pattern and In-vitro Biofilm Forming Abilities of Potential Pathogens Isolated from Inner Lumen of Endotracheal Tubes of Patients Admitted in Critical Care Units

Antimicrobial Susceptibility Pattern and In-vitro Biofilm Forming Abilities of Potential Pathogens Isolated from Inner Lumen of Endotracheal Tubes of Patients Admitted in Critical Care Units

Retrospective computed tomography analysis of endotracheal tube constriction and mispositioning in cats and dogs

ObjectiveTo discover the prevalence of endotracheal tube (ETT) constriction and rostral and caudal mispositioning in anaesthetized cats and dogs, and to identify associated risk factors. Study designRetrospective analysis. AnimalsA total of 146 cats and 670 dogs. MethodsComputed tomography images of the head/neck/thorax from orotracheally intubated cats and dogs were visually assessed for constriction or mispositioning of the ETT. If constriction was present, measurements of the cross-sectional area (CSA) of the ETT lumen at constricted and un-constricted locations were compared. Location and cause of constriction were noted and the expected increase in resistance to gas flow was calculated. Animal information was collected from clinical records. Normality of continuous variables was assessed via the Shapiro–Wilk test. Chi-square tests examined associations between variables. Kendall’s tau-b test was performed between measured ETT size and degree of constriction. ResultsThe ETT extended rostrally beyond incisors in 52% of cases; the connector was within the oral cavity in 19% of cases. The ETT extended beyond the first rib in 25.5% of cases. The prevalence of ETT constriction was 22.7%. Median reduction in CSA was 7.68% (0.14–64.19%). Median increase in resistance assuming laminar and turbulent flow was 16.5% (0.3–680%) and 21% (0.3–1200%), respectively. The most common cause of constriction was the presence of a radiotherapy mouth gag. Significant associations existed between presence of constriction and rostral mispositioning, and caudal mispositioning and extreme brachycephaly. Increased severity of constriction was more likely in smaller ETT. Conclusions and clinical relevanceConstriction and mispositioning of ETT occurred very commonly in this population. Checking the ETT within the oral cavity for constriction and mispositioning is recommended. Radiotherapy mouth gags increase the risk of ETT compression. Smaller ETT are at greater risk of severe constriction. Brachycephalic dogs are at particular risk of caudal mispositioning.

The effect of prolonged intubation on ventilator associated pneumonia: endotracheal tube cuff is really steril or not?

Aims: Endotracheal tube (ETT) design, size, cuff material, cuff pressure, and intubation duration are critical in preventing nosocomial pneumonia. We aimed to evaluate the possible infection focus potential of ETT cuff and pilot balloon, particularly in prolonged intubated patients. Methods: A total number of 66 patients who underwent orotracheal intubation and received conventional mechanical ventilation more than 48 hours in the intensive care unit (ICU), were included in this prospective cohort study. Results:The mean duration of intubation was 10.36±4.82 days. Bacteriologically confirmed positive tracheal aspirate culture was 18.2% (n=12). The most frequent positive culture was detected inside of ETT lumen with a percentage of 83.3% (n=55) and followed by cuff (27.3%, n=18), pilot balloon (13.6%, n=9), respectively. It was documented that rates of lung infections were significantly increased after 14 days (p = 0.017) and rates of cuff positive cultures were significantly increased after 10 and 14 days of incubation (p= 0.001, p=0.004). The same type of bacteriological strains was identified from both pilot balloon (n=9) and ETT cuff (n=9), simultaneously. In the remaining 9-cuff positive patients pilot balloons were sterile and ETT lumens were positive culture with the same strains as identified from the cuff. There was a statistically significant positive correlation between the intubation duration and the number of infected ETT parts (p<0.001). Conclusion: ETT cuff was demonstrated to be a potential infection focus in the present study. In addition, it was observed that ETT cuff colonization increased in proportion to the intubation duration. We suggest changing ETT at appropriate time intervals in order to reduce ventilator-associated pneumonia in intubated patients.

Inactivation of biofilms in endotracheal tube by cold atmospheric plasma treatment for control and prevention of ventilator‐associated pneumonia

AbstractVentilator‐associated pneumonia (VAP) is a type of hospital‐acquired infection with high mortality and morbidity rates that is seen in critically ill patients who are connected to mechanical ventilators in intensive care units. Conventional infection control measures may remain insufficient for control and prevention of VAP. In the present study, biofilms of most common pathogens, which are responsible for VAP, namely Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, and Candida albicans, were grown in the lumen of endotracheal tubes (ETs) under low shear to mimic the biofilm formation in clinical settings using the drip flow reactor system. Antibiofilm efficacies of two different plasma treatment methods were tested on the biofilms that were grown in ETs. In the first method, deionized water (DIW), phosphate‐buffered saline (PBS) solution, and N‐acetylcysteine (NAC) solution were treated with air dielectric barrier discharge (DBD) plasma and then nebulized on the biofilms. In the second method, air plasma afterglow (APA), which was generated using a DBD jet electrode, was flown through the lumen of ETs. Effects of two different plasma treatment methods on biofilms were evaluated using colony‐counting and XTT assays. The quantity of extracellular polymeric substance (EPS) was evaluated with the safranin assay. Scanning electron microscopy (SEM) was used to visualize the effect of various plasma treatment methods on biofilms. Cytotoxic effects of two different plasma treatment methods were tested on the human tracheal epithelial cell line. Our results suggest that the nebulized plasma‐treated NAC solution had a superior antibiofilm effect as compared with DIW and PBS. Two different plasma treatment methods used effectively inactivated biofilms and significantly reduced the quantity of EPS without a significant damage to the human tracheal epithelial cell line. Furthermore, SEM images showed the inactivation of microbial cells mainly through membrane damage.

Endotracheal tube obstruction with a blood clot following aspiration of rumen contents in a reindeer

SummaryAn apparently otherwise healthy female reindeer was anaesthetised for open reduction and fixation of a hip luxation. The animal developed ruminal bloat which was treated with passage of an orogastric...

Partial endotracheal tube obstruction by a blood clot in two dogs

Case 1: A seven-year-old lurcher presented after an episode of severe respiratory distress and collapse, which had been treated by the referring veterinary surgeon with a tracheostomy tube placement. Laryngeal...

A new technique for avoiding barotrauma-induced complications in apnea testing for brain death

Prompted by our experience with complications occurring with apnea testing (AT), we discuss complications reported in the literature. AT is an integral part of brain death assessment. Many complications of AT have been described, including hypoxemia, arterial hypotension, tension pneumothorax and cardiac arrest. We conclude that a commonly used technique in conducting AT can create auto-positive end expiratory pressure (PEEP) and contributes to many complications. The mechanism of occult auto-PEEP in AT is discussed. Intensive care unit patients may have a compensated and asymptomatic relative hypovolemia that can be decompensated by a small amount of auto-PEEP produced by air trapping during insufflating oxygen (O2) through a 7.0 endotracheal tube (ETT). It could then lead to decreased preload, decreased stroke volume, decreased cardiac output and thus, to hypotension and a compensatory tachycardia. The placement of the standard O2 tubing (6mm outside diameter [OD]) inside the 7.0 ETT (7mm inside diameter [ID]) greatly decreased the ETT lumen (73%). We changed our practice to instead use readily available small pressure tubing to insufflate O2 for AT to avoid excessive reduction in the ETT lumen. The change from standard O2 tubing (6mm OD) to pressure tubing (3mm OD) will greatly decrease the reduction in cross-sectional area of 7.0 ETT lumen from 73 to 18% and avoid potential complications of air trapping, auto-PEEP and barotrauma. We have successfully used this new simple technique with readily available equipment to eliminate auto-PEEP in AT while preserving oxygenation.

Gum elastic bougie as a tube exchanger: Modified technique.

Sir, The standard gum elastic bougie (GEB) which is used mainly for aiding in difficult laryngoscopy and intubation can be used as a tube exchanger also. The essential steps of tube exchange using GEB require it to be inserted into the lumen of the endotracheal tube (ETT) until the markings of the GEB correlate with the markings on the ETT. This indicates that the tip of the GEB is at the tip of the ETT.[1] Subsequently, cuff of the ETT is deflated and the ETT withdrawn gently over the GEB, whereas the operator end of the GEB is held securely. However, by the time, the tip of the ETT comes to lie in the oral cavity; the whole length of the GEB gets lost within the ETT lumen and the oral cavity resulting in the anaesthesiologist losing control over the GEB completely. This is because the GEB measures 60 cm in length and an ETT of 8.0 mm inner diameter (ID) measures 36 cm [from its distal end to the edge of the blue connector, Figure 1a], thus resulting in only 24 cm of GEB length remaining outside the ETT. Furthermore, the ETT is usually fixed around 22–23 cm at the angle of the mouth. Hence, overall 59–60 cm length of the GEB is required to be inserted into the ETT (36 cm ETT length and 22–23 cm length inside the oral cavity) before the shaft of the GEB could be recovered outside the oral cavity, when the ETT tip comes out. Therefore, invariably the anaesthesiologist ends up losing control over the GEB for a brief while. This total loss of control over the GEB can result in the GEB either migrating deeper into the trachea, thus stimulating the carina in an already/almost awake patient, or there is a risk that the GEB comes out of the larynx along with the ETT and gets accidentally placed in the oral cavity or oesophagus. The traditional airway exchange catheters measure more than 80 cm (83 cm, 11 and 14 G), and, therefore, do not have this problem.[2] As long as the length of the GEB is more than twice that of the ETT, this problem should not happen. Bougies from other manufacturers that measure approximately 70 cm in length are available, and these problems are unlikely to be encountered with these.[3]Figure 1: (a) Length of the 8.0 mm internal diameter endotracheal tube is seen to be approximately 36 cm, and when gum elastic bougie is inserted appropriately, 24–25 cm of it projects outside the endotracheal tube. The figure also shows a shortened endotracheal tube of 8.0 mm internal diameter, which is cut at 24 cm mark. This allows for nearly 36 cm of the gum elastic bougie projecting out of the endotracheal tube. (b) A 4.5 mm internal diameter uncuffed endotracheal tube snugly fits the distal end of the gum elastic bougie thus lengthening the gum elastic bougie to >80 cmHaving experienced these problems with the traditional GEB when used as tube exchanger on a couple of occasions, we have devised two unique solutions to overcome these problems. First, prior to planned extubation of the ETT, the ETT is cut at its 24–26 cm mark (1 or 2 cm above the oral cavity), and the blue connector is fixed [Figure 1a]. Since the ETT length now is reduced by almost 10 cm relative to ETT, it ensures that the length of GEB (60 cm) is now more than double that of the ETT (26 × 2 = 52 cm). Hence, nearly 34-36 cm of it lies outside the ETT when correctly positioned and therefore, it allows the anaesthesiologist to be always in control of the GEB during the procedure of extubation. However, it requires that another ETT be cut to similar length and kept beside the patient for future tube exchange if need be. The second solution involves attaching an uncuffed 4.5 mm ID ETT to the proximal end of the bougie. This snugly fits the GEB [Figure 1b] and requires considerable force to separate the two. Thus, this setup helps in lengthening the GEB to >80 cm. We are confident these solutions to GEB can help minimise the complications discussed earlier. While a GEB may not be suitable for tube exchange through the nasal route due to the limitation of length, these 2 modifications can enable the traditional GEB to be used through both oral and nasal routes. Though an airway exchange catheter is ideal for extubation of the difficult airway and tube exchange, the modified GEB with the second solution that we have provided appears to have an edge as it is useful in aiding difficult intubation also. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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Pirrone, Massimiliano1; Pinciroli, Riccardo1; Mietto, Cristina1; Imber, David1; Chenelle, Christopher1; Kacmarek, Robert1; Berra, Lorenzo1 Author Information

Sudden endotracheal tube block in a patient of Achalasia Cardia

Endotracheal tube block due to various mechanical causes such as mucous, blood clot, denture, and ampoules have been reported. A patient of achalasia cardia with chronic passive aspiration pneumonitis developed mucoid mass in the respiratory passage which dislodged during the surgical procedure. The episode occurred almost an hour after induction of anesthesia and the dislodged mucoid mass blocked the lumen of endotracheal tube, leading to hypoxia and impending cardiac arrest. However, the patient was salvaged by replacing the tube.

Using the CAM Rescue Cath™ to Restore Endotracheal Tube Patency

PURPOSE: To determine if a novel device can successfully extract occlusive materials from the inner lumen of endotracheal tubes (ETT), thereby restoring the native lumen, minimizing the need to exchange the ETT and promote the weaning process. The Hypothesis is that the device is designed to successfully remove secretions that narrow the lumen and suction the ETT lumen, accomplishing these goals.

Airway Obstruction Due to Endotracheal Tube's Lumen Collapse Secondary to Cuff

To the Editor An 11-year-old boy was admitted to the emergency room after falling 15 m. His trachea was intubated in the field with a 5.5-mm inner diameter (ID) cuffed Rusch® endotracheal tube (ETT, Teleflex Medical, Research Triangle Park, NC), pulse oximeter saturation was 100%, and the ETT position was confirmed by capnography and chest radiograph. Ventilation became increasingly difficult (peak airway pressures of 30–35 cm H2O), breath sounds were barely audible, chest movements were minimal, and the end-tidal carbon dioxide was in the high 40s. The patient was urgently transported to the computed tomography (CT) suite, where after the initial scan sequences, ventilation became more difficult and the patient's trachea was reintubated with a styletted 5.5-mm ID cuffed ETT with immediate improvement of all respiratory variables. Examination of the initial CT images revealed a grossly overinflated ETT cuff causing collapse of the ETT lumen with almost complete airway obstruction (Fig. 1).Figure 1: Computed tomography of the head and anterior neck (sagittal image) showing the large, overinflated cuff and the collapsed endotracheal tube.Despite the suggestive CT imaging, we remained uncertain about the mechanism of the ETT collapse and decided to try to reproduce it in vitro. We placed the cuff of five 5.5-mm ID ETTs (Hi-Lo®; Mallinckrodt Co., Juárez, Mexico, the type of ETT we use in our institution) within the barrel of a 20-mL syringe and inflated the tube's cuff. We were unable to produce an ETT collapse in any of the ETTs studied even after cuff inflation with 20 mL of air, which developed a cuff pressure well above the maximal pressure (120 cm H2O) measurable with a cuff manometer (Cufflator #8199; Posey Co., Arcadia, CA). We repeated the in vitro test with three 6.0 Rusch ETTs (the type used for the prehospital intubation in our patient) and the lumens of the ETTs collapsed at lower volumes (12.5, 14.3, and 15 mL, respectively) and pressure >120 cm H2O (Fig. 2).Figure 2: Cuffed Rusch® endotracheal tube, 6.0-mm inner diameter, filled with contrast fluid, showing the collapsed tube after inflation of the cuff with 15 mL of air.When ETT cuff pressures are not monitored, cuff pressures greater than the recommended 20 to 30 cm H2O may develop. In one study, ETT cuff pressures were within the recommended ranges in only 27% of the patients.1 In the prehospital setting, most cuff pressures exceeded 40 cm H2O and required correction.2 In our in vitro trial, only the Rusch but not the Mallinckrodt ETT collapsed upon extreme overinflation of the cuff. The difference may stem from the quality of the polyvinyl chloride tube and hence from different compliances of the ETT wall. Although the findings in our in vitro model might resemble those of the in vivo situation, there are some differences. First, the human trachea has a greater compliance than that of a syringe barrel. Second, we did not warm the ETT and the syringe to body temperature but we theorize that warming would have made the ETT even softer (less rigid), thus requiring even less volume for cuff inflation to collapse the ETT. The patient's clinical timeline suggests that the obstruction worsened over time, possibly because of the temperature effect on the ETT tube, resulting in almost complete obstruction. Practitioners should be aware of the differences among different ETTs and the possibility that certain tubes may have the propensity to collapse after cuff overinflation. Dan Davis, MD Joseph Murphy, MDRadu B. Pop, MS Department of Anesthesiology and Pain Management University of Texas Southwestern Medical School and Children's Medical Center at Dallas Dallas, Texas Peter Szmuk, MD Department of Anesthesiology and Pain Management University of Texas Southwestern Medical School and Children's Medical Center at Dallas Dallas, Texas Outcomes Research Consortium The Cleveland Clinic Cleveland, Ohio [email protected] or [email protected]

Experience With a New Device for Clearing Mucus From the Endotracheal Tube

Partial or total obstruction of an endotracheal tube (ETT) by mucus can cause severe respiratory distress, hypoxemia, or death. Signs of an obstructed ETT include increased ventilation pressure, changes in the ventilator graphics, S(pO(2)) decrease, and cardiovascular changes. We present 3 patients whose ETTs were partially obstructed by mucus. In each case the patient displayed adverse effects from the obstruction, but once the obstruction was removed they showed dramatic improvement. In each case we used a new device (Rescue Cath, Omneotech, Tavernier, Florida) designed to remove mucus from the ETT lumen. The 3 cases demonstrate that the device is effective and capable of relieving the adverse effects of ETT mucus obstruction.

Detection of partial endotracheal tube obstruction by forced pressure oscillations

Rapid airway occlusions during mechanical ventilation are followed immediately by high-frequency pressure oscillations. To answer the question if the frequency of forced pressure oscillations is an indicator for partial obstruction of the endotracheal tube (ETT) we performed mathematical simulations and studies in a ventilated physical lung model. Model-derived predictions were evaluated in seven healthy volunteers. Partial ETT obstruction was mimicked by decreasing the inner diameter (ID) of the ETT. In the physical model ETTs of different ID were used. In spontaneously breathing volunteers viscous fluid was applied into the ETT's lumen. According to the predictions derived from mathematical simulations, narrowing of the ETT's ID from 9.0 to 7.0mm decreased the frequency of the pressure oscillations by 11% while changes of the respiratory system's compliance had no effect. In volunteers, a similar reduction (10.9%) was found when 5 ml fluid were applied. We conclude that analysis of pressure oscillations after flow interruption offers a tool for non-invasive detection of partial ETT obstruction.

Miniature acoustic guidance system for endotracheal tubes

Ensuring that the distal end of an endotracheal tube (ETT) is properly located within the trachea, and that the tube is not obstructed by mucus deposition, is a major clinical concern in patients that require mechanical ventilation. A novel acoustic system was developed to allow for the continuous monitoring of ETT position and patency. A miniature sound source and two sensing microphones are placed in-line between the ventilator hose and the proximal end of the ETT. Reflections of an acoustic pulse emitted into the ETT lumen and the airways are digitally analyzed to estimate the location and degree of lumen obstruction, as well as the position of the distal end of the tube in the airway. The system was evaluated through in vitro studies and in a rabbit model. The system noninvasively estimated tube position in vivo to within roughly 4.5 mm, and differentiated between proper tracheal, and erroneous bronchial or esophageal intubation in all cases. In addition, the system estimated the area and location of lumen obstructions in vitro to within 14% and 3.5 mm, respectively. These findings indicate that this miniature technology could improve the quality of care provided to the ventilated adult and infant.

A Warm Air Blanket Causes Intraoperative Airway Obstruction

THE safety of the anesthetized patient is facilitated by the use of many devices, such as standard monitors, eye tapes, warm air blankets, and heat moisture exchangers (HMEs). However, this myriad of ancillary devices occasionally may complicate airway management. We report a case of a foreign body causing a potentially lethal intraoperative airway obstruction.A 32-yr-old man was brought to the operating room 1 day after a 9-m fall for repair of a tile-C left hemipelvic disruption and a closed comminuted subtrochanteric fracture of the left proximal femur. History and physical examination showed that the man weighed 100 kg, had no previous medical problems, and had a class II airway. No hemodynamic or neurovascular derangements were noted. The patient was anesthetized with thiopental, fentanyl, and rocuronium and was intubated on the first attempt with an 8.0-mm ID endotracheal tube (ETT). Mechanical ventilation was initiated, and anesthesia was maintained with a mixture of N2O in oxygen and isoflurane. A warm air blanket (Bair Hugger; Augustine Medical, Eden Prairie, MN) and an HME (Humid Vent; Lous Gilbeck AB, Upplands-Vasby, Sweden) were used to help decrease heat loss during the procedure.After reduction of the hemipelvic disruption, preparations were made to transfer the patient to a fracture table for the femur repair. Fractional inspired oxygen was increased to 1.0 for several minutes before the transfer. Then, the circuit was disconnected from the HME, which remained connected to the ETT, and the patient was moved to the fracture table. The circuit was reconnected quickly, but the patient could not undergo ventilation as evidenced by the absence of chest movement and end-tidal carbon dioxide, a peak inspiratory pressure of more than 50 cm H2O, and a tidal volume of less than 100 ml. Then, ventilation was attempted vigorously with use of the reservoir bag, without success. As oxygen saturation began to decrease, the circuit was disconnected from the ETT, and a suction catheter was advanced, showing patency of the ETT lumen. While the circuit was disconnected, it was noted that the reservoir bag did not collapse. An Ambu bag was connected immediately to the ETT, the patient underwent ventilation easily, and oxygen saturation returned to 100%.Subsequent examination of the circuit showed a piece of plastic from the warm air blanket (fig. 1) lodged in the HME. The plastic head drape apparently had become trapped between the circuit and the HME, resulting in a small piece being torn off and occluding the airway. After removal of the obstructing plastic piece, the circuit was reconnected, and surgery was resumed without further incident. Many cases of intraoperative airway obstruction have been reported in the literature. 1–5Hosking et al. 1have proposed a practical algorithm for the management of airway obstruction. The first step is for the patient to undergo manual ventilation with the reservoir bag to remove the ventilator as a source of obstruction. If ventilation is performed easily, it is likely the fault lies within the ventilator. The second step, in the event of continued obstruction, should distinguish between circuit and ETT causes. ETT obstruction can be ruled out by passing a suction catheter or by successful direct ETT ventilation. If direct ETT ventilation is successful, then the circuit comes under suspicion. When the circuit and ETT have been eliminated as causes, patient sources of resistance, such as bronchospasm, pneumothorax, or pulmonary edema must be considered. In the current case, the ETT and the patient were eliminated as causes of obstruction when ventilation was restored by direct ETT ventilation.In the current patient, disconnecting and subsequent reconnecting of the circuit trapped a piece of the warm air blanket within the HME, producing total obstruction of the airway. An HME was implicated previously in airway obstruction in an infant. In that case, a small piece of paper was caught in the HME, preventing effective ventilation. 6Various causes of airway obstruction exist in the operative environment. When an obstruction is recognized, a systematic approach to diagnosis and treatment must be implemented. Because of the wide variety of adjunct devices used by anesthesiologists, we must always be aware of the possibility of an obstructing foreign body.

Role of bacterial biofilm in the pathogenesis of nosocomial pneumonia

Nosocomial pneumonia is still a common problem, especially in intubated and mechanically ventilated patients. The endotracheal tube contributes substantially to the pathogenesis of pneumonia in these patients, because it facilitates microaspiration and impairs host defense. Common nosocomial pathogens like Pseudomonas aeruginosa are known to produce exopolysaccharides and generate a complex biofilm structure, which allows adhesion to abiotic surfaces and protection against antibiotic action. Multiple studies have identified bacterial biofilm on the inner lumen of endotracheal tubes, which represents a permanent source of infectious material. Endotracheal tubes, removed from patients with ventilator-associated pneumonia, are covered more frequently with biofilm than those of uninfected controls. It remains unclear whether this represents a source of infection or contamination. Bacterial biofilm, however, may play an important role in recurrent pulmonary infections of the intubated and mechanically ventilated patient.

Mucoid impaction following nasal intubation in a child with an upper respiratory infection

We describe a case of mucoid impaction following nasotracheal intubation in a child with an upper respiratory infection that was successfully treated with a fiberoptic bronchoscope too large to pass through the endotracheal tube lumen. To the best of our knowledge, it is the first report in the anesthesia literature in which the placement of a nasal tracheal tube is implicated as the cause of the mucous obstruction. The physiologic changes that occur with anesthesia and that place patients at increased risk for this phenomenon, as well as the differential diagnosis, treatment, and prevention of this entity, are discussed.

Continuous low-flow supracarinal and subcarinal oxygen insufflation in addition to intermittent positive-pressure ventilation does not improve gas exchange

Recent studies in animals have demonstrated that continuous insufflation of oxygen near the tracheal carina results in ventilation and carbon dioxide removal that is proportional to the flow rate. The purpose of this study was to determine whether the addition of supracarinal and subcarinal low-flow oxygen insufflation to conventional intermittent positive-pressure ventilation (IPPV) of critically ill and anesthetized patients results in increased ventilation and improved oxygenation. In eight studies a supracarinal catheter (3.7 mm ON was placed 1 to 2 cm above the carina, and in another eight studies two subcarinal catheters (1.7 mm ON were placed 2 cm below the tracheal carina under direct vision with a fiberoptic bronchoscope. Both supracarinal and subcarinal catheters were passed within the lumen of an 8 mm ID endotracheal tube. In both groups, conventional IPPV consisted of a tidal volume of 10–12 mL/kg, respiratory rate of 8 to 10 breaths/min, O cm H 2O positive end-expiratory pressure (PEEP), and F 1O 2 of 1.0. In both groups, continuous oxygen insufflation flow rates were 0.05, 0.10, and 0.20 L/ kg/min. It was found that compared with control conditions (no insufflation), oxygen insufflation at all flow rates in both supracarinal and subcarinal insufflation groups did not cause any significant change in either oxygenation or ventilation. There was a significant increase in proximal peak airway pressure with each incremental increase in continuous oxygen flow rate. Conversely, there was a significant decrease in mean arterial pressure and cardiac output with each incremental increase in continuous oxygen flow rate. It is concluded that use of continuous low-flow insufflation of oxygen with simple administration systems (catheters within the lumen of endotracheal tube) in addition to conventional IPPV is contraindicated at the present time. Further studies using different insufflation systems may prove to be worthwhile.