Rupture of the left main-stem bronchus with a polyvinylchloride double-lumen tube

Airway Rupture Caused by Double-Lumen Tubes: A Review of 187 Cases

The double-lumen tubes (DLTs) are the most widely used devices to provide perioperative lung isolation. Airway rupture is a rare but life-threatening complication of DLTs. The primary aim of this review was to collect all cases reported in the literature about airway rupture caused by DLTs and to describe the reported possible contributors, diagnosis, treatment, and outcomes of this complication. Another aim of this review was to assess the possible factors associated with mortality after airway rupture by DLTs. A comprehensive literature search for all cases of airway rupture caused by DLTs was performed in the PubMed, EMBASE, Ovid, Wanfang Database, and CNKI. The extracted data included age, sex, height, weight, type of operation, type and size of DLT, site of airway rupture, possible contributors, clinical presentation, diagnosis timing, treatment, and outcome. We included 105 single case reports and 22 case series with a total number of 187 patients. Most of the ruptures were in the trachea (n = 98, 52.4%) and left main bronchus (n = 70, 37.4%). The common possible contributors include use of a stylet, cuff overdistention, multiple attempts to adjust the position of a DLT, difficult intubation, and use of an oversized DLT. Most of the airway ruptures were diagnosed intraoperatively (n = 138, 82.7%). Pneumomediastinum, air leakage, hypoxemia, and subcutaneous emphysema were the common clinical manifestations. Most patients were treated with surgical repair (n = 147, 78.6%). The mortality of the patients with airway rupture by DLTs was 8.8%. Age, sex, site of rupture, diagnosis timing, and method of treatment were not found to be associated with mortality.

Comparison between computerized tomography-guided bronchial width measurement versus conventional method for selection of adequate double lumen tube size

Background:

Selection of adequate size double lumen tube (DLT) is complicated by marked inter-individual variability in morphology and dimensions of tracheobronchial tree. Computerized tomography (CT)-guided left bronchus width measurement has been used to predict adequate size DLT in European and Singapore population; however, no such data exist for Indian population who are racially different. We compared the effect of DLT size selection based on CT-guided bronchial width measurement to the conventional method of DLT selection on the adequacy of both lungs isolation and on the safety margin of right-sided DLT.

Methods:

Fifty-five adults scheduled to undergo thoracotomy were enrolled in this prospective observational study. An appropriate size left- or right-sided DLT with outer diameter 0.5–1 mm smaller than the CT-measured bronchial width was selected for the isolation of lungs. Adequacy of separation was checked using fiberoptic bronchoscope. The safety margin of selected right-sided DLT size was calculated from CT-measured right upper lobe bronchus width and diameter of right upper lobe ventilation slot of the DLT.

Results:

Adequate separation of lungs was achieved in 92.7% of studied population, 90.9% in males, and 95.4% in females. Among these, 54.9% patients required different sized DLT as compared to conventional method. Overall safety of margin of right-sided DLTs was comparable between two methods of DLT selection (median [IQR] 4.8 (3.5–6.8) vs. 6.59 (3.5–7.8), P = 0.317). DLT size with adequate isolation of lung correlated with height, tracheal width (TW) on chest X-ray, and age of the patients. A formula to calculate DLT size based on these variable was derived.

Conclusion:

CT-measured bronchial width predicts the appropriate DLT size better than conventional method. In the absence of CT scan facility, patient height, age, and chest X-ray TW may be used to predict DLT size with reasonable accuracy.

Rupture of Left Main Bronchus Associated with Radiotherapy-induced Bronchial Injury and Use of a Double-lumen Tube in Oesophageal Cancer Surgery

We report a case of rupture of the left main bronchus in a female patient with oesophageal carcinoma, who had received thoracic radiotherapy preoperatively. Endotracheal intubation was achieved with a left-sided double-lumen tube. After almost three hours of intubation and one and half hours of one-lung ventilation, bronchial injury was detected. Immediate surgical repair of the membranous part of the bronchus was undertaken, as well as completion of the oesophagectomy. Radiotherapy-induced damage to the bronchus was thought to have contributed to the rupture. The presentation, diagnosis and management of intraoperative bronchial rupture are discussed.

Bronchoscopy-guided topical hemostatic tamponade therapy for the management of life-threatening hemoptysis

STUDY OBJECTIVES

Massive hemoptysis is a life-threatening condition. Therapeutic strategies such as interventional angiography, surgery, and/or bronchoscopy have been applied in the clinical setting with variable results. We investigated the efficacy of bronchoscopy-guided topical hemostatic tamponade therapy (THT) using oxidized regenerated cellulose (ORC) mesh in the management of life-threatening hemoptysis.

DESIGN

Seventy-six consecutive patients underwent emergency bronchoscopy for massive hemoptysis. Fifty-seven patients (75%) had persistent endobronchial bleeding despite bronchoscopic wedging technique, cold saline solution lavage, and instillation of regional vasoconstrictors. These patients subsequently underwent THT according to the same procedure.

SETTING

Teaching hospital, bronchoscopy unit of a 300-bed tertiary pulmonary referral center.

RESULTS

THT with ORC was successfully performed on 56 of 57 patients (98%) with an immediate arrest of hemoptysis. All patients successfully treated with THT remained free of hemoptysis for the first 48 h. None required intensive care support or immediate surgery. Mean procedure time (+/- SD) of THT was 11.5 +/- 4.2 min. Recurrence of hemoptysis that was characterized as being mild (< 30 mL) to moderate (30 to 100 mL) developed in six patients (10.5%) 3 to 6 days after THT. Post-obstructive pneumonia developed in five subjects (9%) after endoscopic THT. A subgroup of patients (n = 14) underwent bronchoscopic follow-up 4 weeks after discharge. The ORC mesh was absorbed in all of these patients without signs of foreign body reaction.

CONCLUSIONS

Endobronchial THT using ORC is a safe and practicable technique in the management of life-threatening hemoptysis with a high success and a relatively low complication rate.

Rapid deflation of the bronchial cuff of the double-lumen tube after decreasing the concentration of inspired nitrous oxide

Deflationary phenomena of the endotracheal tube cuff may occur after inspired nitrous oxide (N(2)O) concentrations are reduced, but deflationary phenomena of the double-lumen tube (DLT) cuff have not been investigated. In this study, tracheal and bronchial cuffs of left-sided Mallinckrodt (Athlone, Ireland) DLTs were inflated with air, 40% N(2)O, or 67% N(2)O (Air, N40, or N67 groups, respectively) in 24 patients undergoing thoracic surgery; 40 min later, O(2) was substituted for N(2)O in some of the patients in the N40 group (N40-c group). Intracuff gas volumes, N(2)O concentrations, and cuff compliance were also measured. Both tracheal and bronchial cuff pressures significantly increased in the Air group but decreased in the N67 group. Neither pressure significantly changed in the N40 group, but both decreased in the N40-c group after terminating N(2)O anesthesia; the time required for bronchial cuff pressures to decrease by half (12.0 +/- 5.5 min) was less than that for tracheal cuff pressures (31.2 +/- 11.0 min, P < 0.01). The volume change in the N40-c group was not significantly different between the tracheal and bronchial cuffs, but tracheal cuff compliance was significantly higher than bronchial compliance. Therefore, filling DLT cuffs with 40% N(2)O stabilizes cuff pressure during anesthesia with 67% N(2)O, but bronchial cuffs deflate more quickly than tracheal cuffs after cessation of N(2)O administration through smaller compliance.

IMPLICATIONS

We demonstrated that after cessation of nitrous oxide (N(2)O) administration, bronchial N(2)O-filled cuffs of the double-lumen tube deflate more rapidly than tracheal cuffs. To avoid insufficient separation of the lungs by the bronchial cuff, a frequent check of the cuff pressure is recommended after the inspired N(2)O concentration is decreased.

Bilateral pneumothoraces, pneumomediastinum, pneumoperitoneum, pneumoretroperitoneum, and subcutaneous emphysema following intubation with a double-lumen endotracheal tube for thoracoscopic anterior spinal release and fusion in a patient with idiopathic scoliosis

Recently, thoracoscopic approaches to the spine have taken on greater clinical applications in the treatment of spinal deformity with generally good results. However, the steep learning curve must be ascended by the surgeon and may lead to complications early in one's experience. There also exists a learning curve for the anesthesiologist to become adept at obtaining single lung ventilation and managing this throughout the operative procedure. We report a case of an 11-year-old patient with severe scoliosis who developed air in both chest cavities, mediastinum, peritoneum, retroperitoneum, and subcutaneous tissue after intubation with a double-lumen endotracheal tube. The patient remained hemodynamically stable throughout this period, and bilateral chest tubes were placed. The patient remained on the ventilator for 24 hours and was extubated without sequelae. Complications from a thoracoscopic approach to the spine for deformity are most often attributed to the learning curve of the surgeon; however, the entire operative team becomes exposed to the challenges of performing this procedure. This report documents a life-threatening complication of air throughout the chest, mediastinum, abdomen, and subcutaneous tissues in a patient with severe scoliosis.

Positioning of a double-lumen endobronchial tube without the aid of any instruments: an implication for emergency management

BACKGROUND

Lung isolation and preservation of normal lung are the first lines of therapy in life-threatening massive hemoptysis. If bleeding continues but the side of origin is uncertain, use of a double-lumen tube (DLT) is reasonable. Utilizing a blind method to locate the bronchial cuff of a left-sided DLT without using any instrument, a DLT (Broncho-Cath, Mallinckrodt Medical Ltd., Athlone, Ireland) was successfully positioned without delay in a patient with massive hemoptysis, where auscultation could be misleading or useless and fiberoptic bronchoscope (FOB) was inapplicable. This study was performed to discern whether this blind method could substitute for FOB verification or auscultation in most circumstances where these two methods are unavailable or inapplicable.

METHODS

After receiving informed consent and hospital ethics board approval, 58 elective thoracic surgical patients, aged 17 to 67 years, were enrolled in the study and divided into two groups. A conventional method using an FOB was used to locate the left-sided DLT in 29 patients (group 1). In the other 29 patients (group 2), the blind manual method was used. The left-sided DLT was inserted until some resistance was felt, at which time the bronchial cuff was inflated with approximately 2.0 mL of air. While gently holding the pilot with thumb and index finger of the nondominant hand, the DLT was slowly withdrawn until an abrupt decrease of pilot pressure was sensed. At that moment, the bronchial cuff was deflated, and the DLT was advanced approximately 1.5 cm; using an FOB, its position was checked by an independent observer not involved in positioning the DLT. Success was defined as the point when the proximal margin of the carina was within the margin of safety for the DLT, which is defined as the difference between the length of the left main bronchus and the length of the tube between the proximal margin of the left bronchial cuff and the left lumen tip. Postoperative FOB was performed to evaluate bronchial injury.

RESULTS

In 26 of 29 patients (group 2), the position of the DLT was bronchoscopically confirmed to be a success. The other three cases were deemed to be too shallow; specifically, the bronchial cuffs were slightly herniated onto the carina (acceptable position). This method was more traumatic than FOB-guided DLT intubation (conventional method) (p = 0.001); however, the most severe damage was erosion.

CONCLUSION

This method, which requires no specific instrument and no time-consuming technique, can be taught easily and may be used in a situation where the rapidity of lung isolation or collapse is the key to saving life. We conclude that this blind method can be an alternative to the FOB and/or auscultation for the positioning of DLT in an emergency situation.

Computed tomography-based tracheobronchial image reconstruction allows selection of the individually appropriate double-lumen tube size

OBJECTIVES

To determine whether individualized selection of double-lumen tubes or alternatives based on three-dimensional reconstruction of the tracheobronchial image from routine preoperative computed tomography (CT) scans leads to clinically appropriate choices.

DESIGN

Prospective observational study; comparison to historic controls.

SETTING

Anesthesia and radiology facilities of a university medical center.

PARTICIPANTS

Forty-nine patients undergoing thoracic surgery requiring one-lung ventilation.

INTERVENTIONS

Three-dimensional image reconstruction of individual tracheobronchial anatomy was performed from routine preoperative spiral CT scans as well as from scans of five left-sided and four right-sided double-lumen tubes. Results of image-based tube size selection were compared with literature recommendations. Prospectively, individualized tube selection was performed by superimposition of printed transparencies of tubes over the tracheobronchial system and was validated using bronchoscopic and clinical criteria (n = 24).

MEASUREMENTS AND MAIN RESULTS

Three-dimensional reconstruction visualized individual anatomy with good accuracy and resolution. Correlations between patient morphology and tracheobronchial dimensions were weak (height versus mainstem bronchial diameters: r < 0.50). In 11 of 48 patients (23%). CT-fitted double-lumen tube sizes would have differed from a conventional height-based and gender-based selection. Individual, prospective, CT-based double-lumen tube selection was associated with (1) good fit and positioning confirmed by fiberoptic bronchoscopy, (2) adequate bronchial cuff seal volumes, (3) complete lung separation, and (4) oxygenation and ventilation parameters during one-lung ventilation similar to those with conventional size selection. In one patient, three-dimensional CT study allowed noninvasive evaluation of a tracheal stenosis precluding double-lumen tube placement.

CONCLUSION

Individualized selection of double-lumen tube size using CT-based reconstructions of tracheobronchial anatomy leads to clinically appropriate choices. Risks resulting from variations in tracheobronchial morphology are recognized in advance.

A new and simple maneuver to position the left-sided double-lumen tube without the aid of fiberoptic bronchoscopy

The double-lumen tube (DLT) is the mainstay of one-lung ventilation (OLV). We sought to determine whether this new intubation maneuver using an endobronchial cuff pressure could be substituted for verification by fiberoptic bronchoscope (FOB) in most conditions requiring left-sided DLT. Seventy-nine patients requiring video-assisted thoracoscopic surgery for pneumothorax or mediastinal mass, or open thoracotomy for lung or esophageal cancer were enrolled in this study. We used 35F (n = 23), 37F (n = 51), or 39F (n = 5) disposable polyvinyl chloride DLTs (Broncho-Cath; Mallinckrodt Medical Ltd., Athlone, Ireland), depending on the height and gender of the patients. The DLTs were inserted deeply until resistance was felt. At that time, the pilot of the endobronchial cuff was connected to the Control-Inflator (VBM Medizintechnik GmbH, Sulz am Neckar, Germany) via a three-way stopcock. The bronchial balloon was inflated with 1.0-2.0 mL of air through the stop-cock until approximately 30 cm H2O of cuff pressure was obtained. The DLT was slowly withdrawn until the pressure of the Control-Inflator decreased to approximately half the peak pressure during the initial phase of removal. At that time, the bronchial balloon was deflated, and the DLT was advanced approximately 1.0 cm (1.5 cm for the 39F DLT); using FOB, its position was checked by an independent observer not involved in positioning the DLTs. The ideal position was defined as that in which the carina was located at the same level with the middle 5 mm between the proximal margin of the endobronchial balloon and the circumferential black mark. In 50 patients the position was ideal, and in 27 patients it was not ideal but was within the margin of the safety. There were only two failures. We conclude that if a FOB is unavailable or inapplicable, this simple and new maneuver may be used as a substitute during the positioning of DLTs.

IMPLICATIONS

The correct position of the double-lumen tube is vital for one-lung ventilation, which has been confirmed with a fiberoptic bronchoscope. We devised a simple maneuver to position the double-lumen tube correctly without a fiberoptic bronchoscope.

Rupture of the left main-stem bronchus by the tracheal portion of a double-lumen endobronchial tube

We report a rupture of the left main-stem bronchus following the insertion of a left-sided double-lumen endobronchial tube in a 76-yr-old woman with a short trachea. A fiberoptic bronchoscope was not used during the initial insertion of the tube and the depth of insertion resulted in approximately 5 cm in excess of the optimal level for this patient. The rupture had been caused by the tracheal portion of the double-lumen tube. This damage may have been avoided if a fiberoptic bronchoscope was used routinely as an introducer and for positioning of the endobronchial tube under direct vision.

Total intravenous anesthesia and high-frequency jet ventilation during transthoracic endoscopic sympathectomy for treatment of essential hyperhidrosis palmaris: a new approach

OBJECTIVE

To evaluate the effects of high-frequency jet ventilation (HFJV) applied to both lungs on hemodynamic parameters, oxygenation, and operating conditions during bilateral videothoracoscopic sympathectomy.

DESIGN

A prospective, unblinded study.

SETTING

An ambulatory surgical unit at a university medical center.

PARTICIPANTS

30 patients (11 men, 19 women), ASA status 1.

INTERVENTION

Bilateral videothoracoscopic sympathectomies were performed using total intravenous anesthesia with propofol, alfentanil, and atracurium, and the patients were ventilated with an oxygen-air mixture using HFJV delivered to both lungs with a Hi-Lo Jet tracheal tube (Mallinckrodt).

MEASUREMENTS AND MAIN RESULTS

Mean total anesthesia time was 55 +/- 13 minutes. Hemodynamic parameters remained stable during surgery, although ablation of the sympathetic ganglia induced three incidences of bradycardia (10% of the patients), which were responsive to atropine. Four patients developed oxygen desaturation (Sa O2 < 90%) after the creation of the pneumothorax. Surgical conditions were considered excellent by the surgeons. Concerning postoperative complications, a temporary Horner's syndrome was observed in one patient. Another patient had a mild residual pneumothorax on the first postoperative day that resolved without insertion of a chest tube.

CONCLUSIONS

It was concluded that HFJV applied to both lungs is an easy and safe anesthetic technique that provides excellent surgical conditions and causes a minor incidence of morbidity.

Placement of left double-lumen endobronchial tubes with or without a stylet

PURPOSE

This study was designed to determine if leaving a stylet in the left Bronch-Cath endobronchial tube (DLT) for the entire intubating procedure improves the accuracy of placement on the initial attempt, without introducing complications.

METHODS

Sixty ASA 1-3 patients were randomized to one of two groups. In Group 1 (n = 30), the stylet was retained for the entire intubation procedure and in Group 2 (n = 30), the stylet was removed once the bronchial cuff had passed the vocal cords. In both groups, the DLT was turned 110 degrees counterclockwise and advanced until resistance was encountered. Placement was assessed by auscultation and fibreoptic bronchoscopy (FOB). After surgery, the DLT was replaced by a single-lumen endotracheal tube. The thoracic surgeon (blinded to the method of intubation, and using a FOB) assessed the appearance of the tracheobronchial mucosa.

RESULTS

The two groups were similar with respect to sex, height, weight, DLT size, surgeon and expertise of the laryngoscopist. When the stylet was retained, the DLT was correctly placed 60% of the time compared with 17%, if the stylet was removed, (P = 0.001). Seven out of 30 DLTs in Group 2 were initially placed into the right mainstem bronchus, (P = 0.005). The average time to confirmation of correct tube placement by FOB was increased in Group 2, (P = 0.01). Although the observed incidence of left bronchial, mucosal petechiae and erythema was greater in Group 2, this was not statistically significant, (P = 0.063).

CONCLUSION

Retaining the stylet for the entire intubation procedure allows for a more rapid, accurate placement of the DLT without increasing the incidence of tracheobronchial mucosa injury.

[Rupture of the left bronchus during intubation by Carlens tube]

The authors report a case of left main bronchus rupture following endotracheal intubation with a Carlens double-lumen tube. The bronchus rupture occurred during a cure of gastro-oesophageal-reflux and resection of oesophageal diverticula through a left thoracotomy. The patient was a 65-year-old woman treated with corticosteroids for an Addison's disease. The weakness of the bronchial wall initiated by the steroid hormones was an important factor contributing to the perforation. There is also a higher risk of rupture during oesophageal surgery because of surgical dissection and stretch on the tracheobronchial airway. This case demonstrates that such a complication can occur without ventilatory failure. A rupture must be recognized and treated surgically very rapidly. Recommendations regarding the use of double-lumen endotracheal tubes are reviewed in order to decrease the occurrence of such a complication.

Con: the Univent tube is not the best method of providing one-lung ventilation

The Univent tube is a new form of bronchial blocker and is an addition to the armamentarium of the anesthesiologist for managing thoracic surgical cases. As with any new equipment/technique it will require time until the exact indications for its use become clear. The preference of anesthesiologists has oscillated between bronchial blockers and DLTs for the past 50 years, and no overall "best" method of providing OLV has yet been found. Anesthesiologists will continue to use, and to need to know how to use, DLTs for the foreseeable future.

Pro: one-lung ventilation is best accomplished with the Univent endotracheal tube

Over the years, thoracotomy has changed from a procedure that prompted major concern over cross-contamination caused by infection to pulmonary tumors. Assisting the thoracic surgeon by providing OLV is one of the most specialized skills an anesthesiologist can offer. This must be done in a safe, easy, and efficient manner. The Univent tube appears to be a hybrid, combining the best qualities of both the DLT and the single-lumen endotracheal tube with separate Fogarty-like catheter. The Univent tube is a technical improvement over separate endobronchial blocking catheters because its blocker shaft is attached to the main tube and, therefore, displacement is less likely. In addition, the Univent's axial blocker shaft has a lumen that provides for irrigation, suction, oxygen insufflation, CPAP, and HFV. Though equally as effective as the DLT in treatment of intraoperative hypoxemia, the Univent tube presents a unique advantage in the areas of aspiration prevention, prolonged intubation without tube exchange, and selective blockade of lung segments. The Univent tube is also easier to insert and has fewer associated risks compared to the DLT. Is it my purpose to suggest that because the Univent tube is equal to, or better than, the DLT in many areas, we should abandon the use of DLTs? Definitely not. Double-lumen tubes have performed well in the past and will continue to offer specialized functions, such as postoperative independent lung ventilation in single-lung transplant recipients. As with the acquisition of any new medical skill, the use of the Univent tube has a learning curve. It is worth the time and effort to learn to use the Univent tube.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchial cuff pressures of two tubes used in thoracic surgery

The pressure/volume characteristics of the bronchial cuff of a polyvinylchloride (PVC) double-lumen endobronchial tube (DLT) was compared with the inflatable cuff of a bronchial blocker. At the volumes needed to seal a series of rigid model bronchi the PVC DLT bronchial cuff consistently generated significantly lower pressures than the bronchial blocker cuff.

Tracheobronchial rupture caused by blunt chest trauma: acute respiratory management

The clinical management of 12 patients with major intrathoracic tracheobronchial rupture (complete, 3; incomplete, 9) due to blunt trauma has been reviewed and compared with that of two groups of patients with chest injuries not involving the tracheobronchial tree, 17 patients with multiple rib fractures and 17 with chest injuries requiring thoracotomy for control of pneumothorax and hemothorax. The effect of injury on ventilatory function was significantly greater in the patients with tracheobronchial injury in whom an elevated PCO2 at the time of admission was associated with a poor prognosis. Conventional ventilatory management with endotracheal intubation and positive pressure ventilation causing increased air leakage produced further deterioration of pulmonary function in four of the patients with tracheobronchial disruption. The use of a double-lumen endobronchial tube in two patients with tracheobronchial rupture facilitated ventilatory support and subsequent operative management.

[Isolated rupture of the left main-stem bronchus during intubation with a Carlens tube]

A case is reported of bronchial rupture due to a Carlens double-lumen tube. A 73 year old male patient was to undergo a double right lower and middle lobectomy for carcinoma. All went well and as expected until 20 min after the start of left-sided unilateral ventilation by way of the double-lumen tube. A sudden increase in the inspiratory pressures led to the discovery, first, of a leak around the cuff, and then, air bubbles in the mediastinum. Surgical exploration showed up the 4 cm long rupture in the pars membrana of the left main bronchus through which the cuff was herniating. The patient was reintubated and the rupture surgically repaired. The right upper lobe had not been ventilated for 45 min and there were signs of micro-atelectasia. The immediate postoperative course was rather stormy, with severe cardiac failure, recurring right upper lobe atelectasia and bilateral pulmonary infection. The patient was only definitely weaned from the respirator 40 days after the surgical incident. Although such complications with double-lumen tubes are rare, they must be recognized and surgically repaired very rapidly. A few simple rules to prevent these complications are discussed.

A new tube for single lung ventilation

A recently developed endotracheal tube with a movable bronchial blocker (Univent tube) was used for single lung ventilation. A total of 50 intubations were undertaken for a wide variety of thoracic procedures. Each case was analyzed with respect to ease or difficulty of intubation, tube dislodgment, efficacy of lung collapse, and adequacy of single lung ventilation. Successful, safe selective intubation was accomplished in all cases.

Rupture of the tracheobronchial tree

Eleven cases of tracheobronchial rupture are described. Nine were the result of external non-penetrating trauma and all but three had other serious injuries. The remaining two were caused by endobronchial intubation. Of the cases caused by external injury, respiratory tract injury was confined to the cervical trachea in three. Two required tracheostomy and repair and the third was managed conservatively; all made satisfactory recoveries. Intrathoracic rupture was recognised on or soon after admission in three cases. One patient died of uncontrollable pulmonary haemorrhage before he could be operated on; immediate repair gave good long term results in the other two. In three cases rupture of the main bronchus was not recognised until complete obstruction developed three, five, and 12 weeks after the accidents. The strictures were resected and the lung re-expanded. Robertshaw endobronchial tubes ruptured the left main bronchus in two patients undergoing oesophageal surgery. Uneventful recovery followed immediate repair. The difficulty of confirming rupture of a major airway is discussed and the importance of conserving the lung when the diagnosis has been missed is emphasised.

Adverse effects of nitrous oxide

Although once considered completely devoid of complications, it is now recognised that the misuse or inappropriate use of nitrous oxide (N2O) often results in adverse side effects. Hypoxia, particularly the entity 'diffusion hypoxia', can occur with the administration of inadequate amounts of oxygen during or immediately after a N2O anaesthetic. N2O will diffuse into air-containing cavities within the body faster than nitrogen diffuses out. This results in a temporary increase in either the pressure and/or volume of the cavity depending upon the distensibility of its walls. The magnitude of the effect is proportional to the blood supply of the cavity, the concentration of N2O inhaled and the length of time the patient is exposed to N2O. Significant morbidity or even death can result from this phenomenon. A property unique to N2O is its ability to oxidise and inactivate the vitamin B12 components of certain enzymes in both animals and man. One such enzyme, methionine synthetase is essential for normal DNA production. Animal and human studies have demonstrated that the haematological, immune, neurological and reproductive systems are each affected. These adverse effects of N2O can occur after both acute (surgical) or long term (occupational) exposure to the gas. Because of its effects on the pressure and volume characteristics of air-containing spaces, N2O should not be used for patients with bowel obstruction, pneumothorax, middle ear and sinus disease, and following cerebral air-contrast studies. Many anaesthesiologists feel that use of N2O should be restricted during the first two trimesters of pregnancy because of its effects on DNA production and the experimental and epidemiological evidence that N2O causes undesirable reproductive outcomes. Since N2O affects white blood cell production and function, it has been recommended that N2O not be administered to immunosuppressed patients or to patients requiring multiple general anaesthetics. Many anaesthesiologists believe that the potential dangers of N2O are so great that it should no longer be used at all for routine clinical anaesthesia. However, the continued use of N2O remains a controversial topic since, at present, a suitable substitute gas is not available.