Diameter Endotracheal Tube Research Articles

Review of the variation in the outer diameter of uncuffed neonatal and paediatric endotracheal tubes

Review of the variation in the outer diameter of uncuffed neonatal and paediatric endotracheal tubes

Effect of endotracheal tube leak on capnographic measurements in a ventilated neonatal lung model

Uncuffed endotracheal tubes (ET) are commonly used for mechanically ventilated infants to protect airways, but this bears the risk of an air leak around the ET. In contrast to the measurements of tidal volume and respiratory mechanics, very little is known about the effect of ET leaks on capnographic measurements. To investigate the relationship between ET leakage and the CO2 measuring error of the exhaled breathing gas a neonatal lung model was used consisting of two silicon bellows. A constant but very low flow of pure CO2 was injected so that the exhaled breathing gas contained an adjustable CO2 plateau. This lung model was ventilated via a 3 mm inner diameter ET with different respiratory rates (RR) (20, 40 and 60 min−1). ET leaks (0–80%) were simulated by a needle valve. The end-expiratory CO2 partial pressure (PetCO2) was reduced up to zero when an air leak was simulated. Provided that the exhaled CO2 reached a plateau before entering the CO2 washout of the sample chamber by the leak flow, the magnitude of the CO2 decreased independently of RR, and only slightly with increasing ET leak. For ET leaks of up to 20% the CO2 plateau error was <10%. However, in newborns with stiff lungs and a short alveolar plateau capnographic measurements should be interpreted with caution if the ET leak is considerable.

Gas flow between coaxial tubes: Impedance to gas flow in an endotracheal tube increases with a catheter within

The insertion of a suction catheter or a bronchoscope down an endotracheal tube increases the resistance to gas flow down the tube. The extent to which this occurs depends on the relative diameters of the endotracheal tube and the coaxially introduced catheter. This study utilises a laboratory model to quantify this effect, using a steady flow down an annulus between two tubes whose long axes lie co-axially. Two diameters of an endotracheal tube were modelled to represent flow down adult and neonatal endotracheal tubes; these were of internal diameter (d(o)) 6.3 mm and 3.2 mm, and of length (L) 555 mm. A steady flow of air was generated to pass through the model 'endotracheal' tube. Flowrates were calculated to give Re of approximately 5000 for the larger endotracheal tube, and of approximately 1300 for the smaller. These values correspond to clinically appropriate flowrates in adult and neonatal patients, respectively. The pressure drop deltaPo down the endotracheal tube was measured initially without any obstruction, using a calibrated pressure transducer. Catheters of diameter (d(i)) 0.8 mm, 1.6 mm, and 3.2 mm were introduced into the larger diameter endotracheal tube, while catheters of 0.8 mm and 1.6 mm were introduced into the smaller one, and flow was restored to its original value. The pressure drops deltaP down the endotracheal tubes were measured with the catheters introduced a length 'x' into the tube, to x = L/2 and to x = L. Results are compared with a theoretical calculation on the basis of laminar flow for concentric tubes. If a sampling tube or suction catheter is used down the length of an infant's endotracheal tube, the results show that for most values of do/di, there is a significant rise in deltaP/deltaPo. Where a flexible bronchoscope is used down an endotracheal tube or a telescope down a rigid bronchoscope, the value of deltaP/deltaP(o) may also increase unacceptably where d(o)/d(i) is low. The results show that for equal d(o)/d(i), and equal values of x, deltaP/deltaPo are lower for higher values of Re than for lower; and that for lower values of Re there is a more rapid increase in deltaP/deltaPo as x increases, than for higher Re, especially at low values of d(o)/d(i). This result quantifiably confirms clinical experience; that care must be taken in introducing a catheter down a neonatal endotracheal tube. Deviation of these results from the theoretical calculation is less for the smaller Reynolds numbers and smaller values of d(o)/d(i), because under these conditions the flow is more likely to be laminar, with a greater degree of concentricity.

The influence of catheter diameter, endotracheal tube diameter, suction pressure, and PEEP on the tracheal pressure and lung volume during endotracheal suctioning using a lung model

The influence of catheter diameter, endotracheal tube diameter, suction pressure, and PEEP on the tracheal pressure and lung volume during endotracheal suctioning using a lung model

Influence of catheter diameter, endotracheal tube diameter, suction pressure, and PEEP on the tracheal pressure and lung volume during endotracheal suctioning using a lung model

Endotracheal suctioning (ETS) is frequently performed in the ICU for clearing bronchial secretions in intubated and ventilated patients. However, research shows that subatmospheric pressures in the trachea and decreases in lung volume are measured during ETS when unfavourable parameters are chosen, causing complications (for example, atelectasis) [1,2]. The aim of this study was to investigate the influence of the parameters: area ratio 'catheter/endotracheal tube', suction pressure, type of ventilation, and positive end-expiratory pressure (PEEP) on tracheal pressure and lung volume during ETS.

Anesthetic management of a neonate with congenital laryngeal cyst

Anesthetic management of a neonate with congenital laryngeal cyst

Pleural effusion due to intraoperative rupture of an infected renal cyst

Pleural effusion due to intraoperative rupture of an infected renal cyst

Iatrogenic intramural esophageal dissection secondary to insertion of nasogastric tubes and the transorally inserted anvil during robot-assisted total gastrectomy

A 37-year-old female patient (height, 161.5 cm; weight, 49.5 kg) was scheduled to undergo robot-assisted total gastrectomy for early gastric cancer. Her past medical history and physical examination were unremarkable. In the operation room, the patient was induced with 2.0-3.0 vol% sevoflurane after receiving 110 mg of propofol by intravenous injection. Tracheal intubation using a 7.0 mm internal diameter endotracheal tube was performed without difficulty 3 minutes after the patient received 10 mg of cisatracurium by intravenous injection. A 16 French silicone nasogastric tube (Levin tube, Yushin Medical, Bucheon, Korea) was inserted through the left nostril with some difficulty. The nasogastric tube was passed to 55 cm and was noted to drain a small amount of turbid fluid. Twenty minutes after induction of anesthesia, a skin incision was made. The duodenum was resected, the esophagus was clamped and stomach was removed. One and a half hours later, the nasogastric tube was removed. The surgeon made a request to insert the OrVil TM transorally and said that the anvil head should be passed as the convex surface of the anvil head is directed at the posterior wall of the esophagus. At first, the OrVil

The reaction of a patient with suspicious retroverted epiglottis to an anesthetic

The reaction of a patient with suspicious retroverted epiglottis to an anesthetic

Comparison of the effects of two humidifier systems on endotracheal tube resistance

To compare the effects of two humidifier systems on endotracheal tube (ETT) resistance during mechanical ventilation, either an active heated humidifier (HH) or a passive heat and moisture exchanger (HME) was selected using current clinical recommendations. This was a prospective clinical cohort study performed in an intensive care unit. Gas conditioning was performed using the HH in 22 patients and the HME in another 22. Patients were matched for endotracheal tube diameter, days of mechanical ventilation, simplified acute physiology score II (SAPS II), and fluid balance. Used-ETT resistance was measured immediately after extubation. Unused-ETT resistance was calculated with an identical, clean ETT. No differences were found between the HH and HME groups in ETT diameter (7.9 ± 0.4 vs. 7.9 ± 0.3 mm; p = 0.98), days of mechanical ventilation (11.3 ± 7.7 vs. 9.5 ± 4.5; p = 0.34), SAPS II (41.0 ± 13.6 vs. 42.0 ± 11.7; p = 0.79), or fluid balance (-2,552 ± 6,268 vs. -2,579 ± 5,422 mL; p = 0.98). ETT resistance increased from intubation to extubation: from 6.8 ± 1.1 to 10.6 ± 4.3 cmH(2)O L(-1) s(-1) in the HH group, (p < 0.001) and from 6.8 ± 1.1 to 10.2 ± 3.8 cmH(2)O L(-1) s(-1) in the HME group (p < 0.001), which is a 53% average increase in resistive load. We did not find differences between the two types of humidifiers in terms of airflow resistance during prolonged mechanical ventilation when the devices were selected on the basis of individual clinical needs. The increase in resistive load is physiologically relevant.

Performance of the CoughAssist Insufflation-Exsufflation Device in the Presence of an Endotracheal Tube or Tracheostomy Tube: A Bench Study

The CoughAssist is a mechanical insufflator-exsufflator designed to assist airway secretion clearance in patients with ineffective cough. The device may benefit intubated and tracheotomized patients. We assessed the impact of various artificial airways on peak expiratory flow (PEF) with the CoughAssist. We measured PEF and pressure at the airway opening in a lung model during insufflation-exsufflation with the CoughAssist, at 3 set pressures: 30/-30, 40/-40, and 50/-50 cm H(2)O, first without (control), and then with different sizes (6.5 to 8.5 mm inner diameter) of endotracheal tube (ETT) and tracheostomy tube (6, 7, and 8 mm inner diameter), compliance settings of 30 and 60 mL/cm H(2)O, and resistance settings of 0 and 5 cm H(2)O/L/s). We analyzed the relationship between PEF and pressure with linear regression. With compliance of 30 mL/cm H(2)O and 0 resistance the slope of the control relationship between PEF and pressure was statistically significantly greater than during any conditions with ETT or tracheostomy tube. Therefore, in comparison to the control, the relationship of PEF to pressure significantly went in the direction from top to bottom as the ETT or tracheostomy tube became narrower. The findings were the same with compliance of 30 mL/cm H(2)O and resistance of 5 cm H(2)O/L/s. With compliance of 60 mL/cm H(2)O the highest set pressure values were not achieved and some relationships departed from linearity. The control slope of the relationship between PEF and pressure with compliance of 60 mL/cm H(2)O and 0 resistance did not significantly differ with any ETT or tracheostomy tube. The artificial airways significantly reduced PEF during insufflation-exsufflation with CoughAssist; the narrower the inner diameter of the artificial airway, the lower the PEF for a given expiratory pressure.

Low-Frequency Jet Ventilation Through a Bronchial Blocker for Tracheal Repair After a Rare Complication of Percutaneous Dilatational Tracheostomy

p f ( t t a v t m m o r d t c t t n r l p q A67-YEAR-OLD woman was admitted to the hospital with a left hemispheric hemorrhagic insult. Previously, the atient had been treated with low-dose aspirin for a transient schemic attack and had moderate obesity (with an estimated eight of 90 kg and an estimated height of 1.70 m) but was therwise healthy and independent. Because of a lack of neuologic improvement and difficulties weaning from ventilation weeks after the insult, a decision was made to perform a edside percutaneous dilatational tracheostomy using a comercial kit set (CIAGLIA Blue Rhino; Cook Incorporated, loomington) in the intensive care unit. The procedure was erformed under bronchoscopic guidance. After puncture of the rachea and subsequent aspiration of air into a saline-filled yringe, a guidewire was placed, and the position was conrmed by bronchoscopy. The dilatational sequence was neventful, and the tracheostomy tube was placed. After a entilation check, the absence of CO2 return was noted by apnography. Bronchoscopy showed that the tracheostomy ube had passed through both the anterior and the left posteroateral tracheal wall. The tracheostomy tube was withdrawn, nd an endotracheal tube with a 7.0-mm internal diameter was eplaced beyond the lesion under bronchoscopic guidance. Efective ventilation was confirmed by CO2 return waveform with cceptable value. During the entire procedure, no significant decrease in oxyen saturation or major hemodynamic instability was noted; owever, extensive subcutaneous emphysema in the neck and pper chest was found. The chest x-ray revealed a left-sided neumothorax, which was treated by inserting a chest tube. hereafter, the patient was transferred rapidly to the operating oom for repair of the tracheal tear. The planned operative pproach was through an anterior cervical incision with the eck fully extended. It was believed this would provide good xposure to the site of injury and allow for an open tracheosomy to be performed at the end of the case. The surgeons were repared to perform a partial sternal split if necessary. Before he start of the surgery, a 2nd chest tube was inserted because f the posterior malposition of the 1st tube. Bronchoscopy was erformed through the endotracheal tube so that a bronchial lesion ould be excluded. Thereafter, a 7F Arndt bronchial blocker Arndt Endobronchial Blocker Set; Cook Incorporated, Bloomingon, IN) was advanced successfully through the single-lumen .0-internal diameter endotracheal tube into the right main ronchus under bronchoscopic guidance using the guidewire

Palonosetron-induced migraine-type headache

To the Editor, I read with great interest the case written by Singh et al. regarding ondansetron-induced migraine-type headache. I recently encountered a case of severe migraine-type headache triggered in a young female following the administration of palonosetron for postoperative nausea and vomiting (PONV) prophylaxis prior to two different anesthetic exposures. The patient provided her consent to publish details about this case. A 25-yr-old female with primary infertility was scheduled to undergo diagnostic laparoscopy. Her medical history included occasional migraines and anxiety for which she was taking oral propanolol 80 mg once a day. Physical examination and investigations were unremarkable. The patient fasted overnight, and she was premedicated with diazepam 5 mg po and ranitidine 150 mg po the night before and the morning of surgery. She was also given propanolol 80 mg po the morning of surgery. After applying routine anesthesia monitors in the operating room, an 18G venous access was secured in the patient’s right upper limb. Subsequently, palonosetron 0.075 mg iv was administered over ten seconds for the prophylaxis of PONV. After approximately ten minutes and before induction of anesthesia, the patient complained of a severe throbbing headache that was reported as predominantly unilateral and frontal in location. The patient described the headache as similar to her previous migraine attacks. The symptoms lasted for 25 min and responded to treatment with a bolus of propofol 20 mg iv followed by a propofol infusion at the rate of 150 mg hr. Additionally, paracetamol 1 g iv was given over 20 min. After discussion with the patient and the surgeon, anesthesia was induced intravenously with fentanyl 100 lg and propofol 80 mg. The airway was secured with a 7.5-mm internal diameter endotracheal tube after adequate neuromuscular blockade with intravenous vecuronium. The procedure lasted about 45 min, and the patient’s trachea was extubated after she awoke following reversal of neuromuscular blockade with neostigmine and glycopyrolate. There was no headache on recovery, and the patient was transferred to the postanesthesia care unit. The patient was rescheduled for tubal reconstruction one week later. After an 18G epidural catheter was secured at the L1-L2 interspace for intraoperative and postoperative pain management, a pre-emptive dose of palonosetron was administered as PONV prophylaxis. Once again, the patient developed a similar migraine-like headache after five minutes, which was treated effectively with propofol sedation. With the patient’s agreement, anesthesia was induced with propofol and fentanyl. Anesthetic maintenance and recovery were uneventful. On the first postoperative day, intravenous paracetamol 1 g was given every six hours to prevent repeated attacks of migraine, and epidural analgesia with a continuous infusion of a dilute solution of local anesthetic was provided for 48 hr. The patient remained asymptomatic except for dull migraine following discharge to the ward. Palonosetron is the latest 5-hydroxytryptamine-3 (5-HT3) antagonist, which is being described as the first of a ‘‘second generation’’ of 5-HT3 antagonists. Following successful Phase III clinical trials, the Food and Drug Administration approved its use for prevention of PONV in A. Jain, MD (&) Alchemist Hospitals Ltd., Panchkula, India e-mail: amitvasujain@gmail.com

Superior glottic views with the GlideScope® and Airtraq® laryngoscopes compared with an anterior commissure laryngoscope

To the Editor, In the unanticipated difficult airway, an anesthesiologist or otolaryngologist may perform direct laryngoscopy with a rigid anterior commissure laryngoscope. There have been case reports of using the anterior commissure laryngoscope for laryngoscopic rescue in difficult airways. We describe a case in which the view we obtained using two different video laryngoscopes was improved over that seen by an experienced otolaryngologist using an anterior commissure laryngoscope and over that seen by an anesthesiologist using a direct laryngoscope. This observation provides anecdotal support for the role of video laryngoscopy as an early rescue device when direct laryngoscopy affords an inadequate laryngeal view. This report is presented with the written consent of the patient. A 41-yr-old man presented with a recurrence of a squamous cell carcinoma of the tongue. On this occasion, we planned a diagnostic panendoscopy tracheostomy, bilateral neck dissection, composite mandibular resection, and reconstruction. Twelve months earlier, the patient had undergone a panendoscopy, bilateral neck dissection, mandibulotomy, partial glossectomy, and a free forearm flap to the floor of the mouth. Seven months later, a recurrence prompted cisplatin chemotherapy and irradiation with 70 Gy delivered in 35 fractions over seven weeks. The anesthesia chart from the first operation revealed no problems with bag-mask ventilation; direct laryngoscopy offered a Cormack-Lehane (C/L) grade 1 laryngeal view. The patient’s airway assessment prior to the second operation revealed an obvious flap reconstruction of the right tongue, modified Mallampati 2 view, mouth opening greater than three finger breadths, and normal neck flexion with slightly restricted extension. He had full dentition and a prominent overbite but could just approximate his maxillary and mandibular incisors. His anterior neck was swollen and firm to the touch. His body mass index was 21 kg m, and he denied any gastro-esophageal reflux. We felt that direct laryngoscopy would be difficult, but not bag-mask ventilation. Anesthesia was induced with midazolam 2 mg, remifentanil 40 lg, propofol 150 mg, and succinylcholine 100 mg iv. Following induction of anesthesia bag-mask, ventilation was easily achieved. The staff otolaryngologist inserted the anterior commissure laryngoscope as part of the panendoscopy. Since this was achieved with some difficulty, the surgeon introduced an Eschmann Tracheal Tube Introducer (Smiths Medical International Ltd, Hythe, Kent, UK) into the patient’s trachea over which an 8-mm (internal diameter) endotracheal tube was advanced. The best laryngeal view obtained with the anterior commissure laryngoscope, by using external laryngeal pressure and considerable force, was a C/L 2-B. Once a tracheostomy had been performed, three different laryngoscopes were compared by one of the authors (S.K.). Direct laryngoscopy using a Macintosh #3 provided a C/L 3 view. The Airtraq Optical Laryngoscope (Prodol Meditec, Viscaya, Spain) and the GlideScope Cobalt Advanced Video Laryngoscope (AVL) (Verathon Medical, Bothell, WA, USA), both indirect laryngoscopes, provided better views compared with the previous two laryngoscopes. No Electronic supplementary material The online version of this article (doi:10.1007/s12630-010-9413-2) contains supplementary material, which is available to authorized users.

Prediction of Pediatric Endotracheal Tube Size by Ultrasonography

Formulas based on age and height often fail to reliably predict the proper endotracheal tube (ETT) size in pediatric patients. We, thus, tested the hypothesis that subglottic diameter, as determined by ultrasonography, better predicts optimal ETT size than existing methods. A total of 192 patients, aged 1 month to 6 yr, who were scheduled for surgery and undergoing general anesthesia were enrolled and divided into development and validation phases. In the development group, the optimal ETT size was selected according to standard age-based formulas for cuffed and uncuffed tubes. Tubes were replaced as necessary until a good clinical fit was obtained. Via ultrasonography, the subglottic upper airway diameter was determined before tracheal intubation. We constructed a regression equation between the subglottic upper airway diameter and the outer diameter of the ETT finally selected. In the validation group, ETT size was selected after ultrasonography using this regression equation. The primary outcome was the fraction of initial cuffed and uncuffed tube sizes, as selected through the regression formula, that proved clinically optimal. Subglottic upper airway diameter was highly correlated with outer ETT diameter deemed optimal on clinical grounds. The rate of agreement between the predicted ETT size based on ultrasonic measurement and the final ETT size selected clinically was 98% for cuffed ETTs and 96% for uncuffed ETTs. Measuring subglottic airway diameter with ultrasonography facilitates the selection of appropriately sized ETTs in pediatric patients. This selection method better predicted optimal outer ETT diameter than standard age- and height-based formulas.

This Month In Anesthesiology

968 Melatonin premedication is effective in reducing preoperative anxiety.812 Sitting is an advantageous posture over supine posture during induction of anesthesia.892 The Post-operative Recovery Scale can discriminate recovery in multiple domains at multiple times.906 This study indicates the feasibility of using stem cells as an experimental model of human cardiomyocytes for preconditioning.977 Smoking is a risk factor for chronic painful conditions.794 For perioperative β-blockade, early studies demonstrated reduced risk of myocardial ischemia and infarction; however, more recent studies showed increases in bradycardia, hypotension, strokes, and all-cause mortality. This epidemiologic retrospective study analyzed the association of the pattern of use of perioperative β-blockers with postoperative mortality. The pattern of use was divided into four groups: None, Addition, Withdrawal, and Continuous. In patients meeting Perioperative Cardiac Risk Reduction indications for perioperative β-blockade, Addition was associated with a reduction in 30-day (odds ratio [OR], 0.52; 95% confidence interval [CI], 0.33 to 0.83) and 1-yr mortality (OR, 0.64; 95% CI, 0.51 to 0.79). Continuous was also associated with a reduction in 30-day (OR, 0.68; 95% CI, 0.47 to 0.98) and 1-yr mortality (OR, 0.82; 95% CI, 0.67 to 1.0). Withdrawal was associated with an increase in 30-day (OR, 3.93; 95% CI, 2.57 to 6.01) and 1-yr mortality (OR, 1.96; 95% CI, 1.49 to 2.58). This study demonstrated that in using the Perioperative Cardiac Risk Reduction protocol, adding or continuing β-blockers to appropriate patients was associated with a reduction in mortality whereas withdrawal increased mortality. See the accompanying Editorial View on page 767 782 Little is known about response times and outcomes time to defibrillation for intraoperative and periprocedural cardiac arrest. In a retrospective study of data from the American Heart Association registry, this relationship was examined. Data from 865 patients who had intraoperative or periprocedural cardiac arrest because of ventricular fibrillation or pulseless ventricular tachycardia in 259 hospitals were examined. The median time to defibrillation was less than 1 min. Delays in defibrillation occurred in 13.8% of patients. Characteristics associated with delayed defibrillation included pulseless ventricular tachycardia and noncardiac admitting diagnosis. For patients who arrested outside the operating room, delayed defibrillation was associated with a lower probability of surviving to hospital discharge (31.6% vs. 62.1%). This was not the case for cardiac arrests in the operating room (46.8% vs. 39.6%). Delayed defibrillation after cardiac arrests was associated with lower rates of survival only in periprocedural areas, but not in the operating room. See the accompanying Editorial View on page 765 819 Proper endotracheal tube (ETT) size is required to optimize ventilation and to reduce adverse events in pediatric patients. This study utilized ultrasonography to determine if subglottic diameter would better predict optimal ETT size compared with existing methods. One hundred ninety two patients, aged 1 month to 6 yr, scheduled for surgery undergoing general anesthesia, were enrolled. In the study group, the subglottic upper airway diameter was measured via ultrasonography and then standard age-based formulas were used to select ETT size. In a validation group, ETT size was selected based on ultrasonography. Subglottic upper airway diameter highly correlated with outer ETT diameter deemed optimal on clinical grounds (98% agreement for cuffed and 96% for uncuffed ETTs). Appropriately sized ETT selection was improved by first measuring subglottic airway diameter with ultrasonography compared with age- and height-based formulas in pediatric patients.

Successful Tracheal Intubation through an Intubating Laryngeal Airway in Pediatric Patients with Airway Hemorrhage

Background This case report describes the use of the air-Q intubating laryngeal airway (air-Q ILA; Cookgas LLC, St. Louis, MO) for airway rescue and a conduit for blind tracheal intubation in two pediatric patients with failed rapid sequence intubation and difficult airways secondary to airway bleeding in the emergency department (ED). Objectives To describe the use of a new supraglottic rescue device in the management of the pediatric patient’s difficult airway in the emergency setting. Case Report Case 1 was a 5-year-old boy who presented to the ED for bleeding one day after his tonsillectomy. After a rapid sequence intubation, direct laryngoscopy was difficult, with copious bleeding in the oropharynx and inability to visualize the glottis. After two failed direct laryngoscopic attempts to intubate, a size-2 air-Q ILA was inserted. A cuffed 5.0-mm inner diameter (ID) endotracheal tube (ETT) was blindly inserted through the lumen of the air-Q ILA into the trachea successfully. Case 2 was a 13-year-old boy who presented to the ED with a large nasopharyngeal laceration from a motor vehicle accident. After a rapid sequence intubation, direct laryngoscopy showed copious blood with no glottic visualization. A size 3 Laryngeal Mask Airway Classic™ (cLMA; LMA North America Inc., San Diego, CA) was inserted with a large airway leak, and blind ETT insertion via the cLMA was unsuccessful. Subsequently, a size-2.5 air-Q ILA was inserted and adequate ventilation was restored. A cuffed 6.0-mm ID ETT was blindly inserted through the air-Q ILA into the trachea successfully. Conclusion Two cases of failed laryngoscopy in pediatric patients with blood in the airway are described. In each case, insertion of an air-Q ILA was followed by successful blind tracheal intubation via the lumen of the air-Q ILA.

Flow resistance, work of breathing of humidifiers, and endotracheal tubes in the hyperbaric chamber

Humidification of inspired gas is critical in ventilated patients, usually achieved by heat and moisture exchange devices (HMEs). HME and the endotracheal tube (ETT) add airflow resistance. Ventilated patients are sometimes treated in hyperbaric chambers. Increased gas density may increase total airway resistance, peak pressures (PPs), and mechanical work of breathing (WOB). We tested the added WOB imposed by HMEs and various sizes of ETT under hyperbaric conditions. We mechanically ventilated 4 types of HMEs and 3 ETTs at 6 minute ventilation volumes (7-19.5 L/min) in a hyperbaric chamber at pressures of 1 to 6 atmospheres absolute (ATA). Peak pressure increased with increasing chamber pressure with an HME alone, from 2 cm H 2O at 1 ATA to 6 cm H 2O at 6 ATA. Work of breathing was low at 1 ATA (0.2 J/L) and increased to 1.2 J/L at 6 ATA at minute ventilation = 19.5 L/min. Connecting the HME to an ETT increased PP as a function of peak flow and chamber pressure. Reduction of the ETT diameter (9 > 8 > 7.5 mm) and increase in chamber pressure increased the PP up to 27.7 cm H 2O, resistance to 33.2 cmH 2O*s/L, and WOB to 3.76 J/L at 6 ATA with a 7.5-mm EET. These are much greater than the usually accepted critical peak pressures of 25 cm H 2O and WOB of 1.5 to 2.0 J/L. Endotracheal tubes less than 8 mm produce significant added WOB and airway pressure swings under hyperbaric conditions. The hyperbaric critical care clinician is advised to use the largest possible ETT. The tested HMEs add negligible resistance and WOB in the chamber.

Anaesthesia and ventilation strategy in a horse undergoing pulmonectomy

SummaryA 7‐year‐old, 430 kg Standardbred gelding was presented to the hospital with severe bilateral purulent pleuropneumonia requiring partial pulmonectomy. Prior to surgery the trachea was intubated through a tracheotomy site using a customised tube (10 mm internal diameter)‐in‐tube (26 mm internal diameter) endotracheal tube, similar to a bronchial blocker tube in design. The left lung was selectively mechanically ventilated. Thoracotomy was performed and a major lung abscess and surrounding lung tissue were resected. Arterial PO2 and PCO2 remained 79–305 and 43–72 mmHg, respectively, and haemodynamic variables within a range acceptable for general anaesthesia in the horse. A 5 month follow‐up revealed complete resolution of the pleuropneumonia without signs of recurrence.

Letters to the Editor

9 July 2009 Dear Editor, ENDOTRACHEAL SUCTION CATHETER AS A FOREIGN BODY IN A NEONATE Endotracheal suction is a routinely performed procedure in ventilated infants. Endotracheal suctioning is associated with various complications like bacterial colonization, bronchial perforation and rupture of the catheter.1 We report a case of a cut endotracheal suction catheter acting as a foreign body in the tracheobronchial tree causing acute airway obstruction. A term infant with a birth weight of 3742 g required resuscitation with size 3.5-mm endotracheal tube (Portex Tracheal Tube, Smiths Medical Int Ltd, Hythe, Kent, UK). Closed endotracheal suction catheter was attached to the ET tube (Kimberly-Clark Ballard Trach Care closed suction system for neonates, Ballard Medical, Draper, UT, US) (Fig. 1). The endotracheal tube was cut short to reduce dead space. The tip of the suction catheter was accidentally cut, which migrated down to the tracheobronchial tree. Inspection of the suction catheter revealed the presence of the cut end. The suction catheter was not radio-opaque and was difficult to visualize on the X-ray. With change in contrast of the film, the cut end of the catheter was identified in the right main bronchus. A chest X-ray (Fig. 2) showed the collapse of the right upper lobe. The catheter was removed with a rigid bronchoscope and a 1.8-cm length catheter (distal part of the closed suction system) was removed from the right main bronchus. The baby was successfully extubated within 24 h of the removal of the suction catheter. Tracheobronchial foreign bodies are extremely rare in neonates. In hospitalized infants, the foreign bodies include shearing of plastic sheath of the endotracheal stylet2 and rare cases of rupture of closed endotracheal suction catheters.3 A closed system is used frequently and this becomes part of the ventilatory circuit. Shortening an ETT to a length appropriate for patient use (e.g. a 4.0-mm inner diameter endotracheal tube shortening, from 20.7 to 11.3 cm reduces its resistance by 22%.4) If the ET tube is to be shortened, the suction catheter needs to be withdrawn completely. Visualization of the suction catheter is difficult and care needs to be exercised before any shortening of the ET tubes is attempted. The black mark at the tip of the inline suction suction should be within the dome before cutting. This case highlights the need to exercise care with cutting of the ET tubes especially when an inline suction is attached.