ORIGIAL ARTICLES Res tk iratory Acidosis wi the Small Ston-Hopkins Bronchoscopes: Occurrence and Management Kang H. Rah, M.D., Arnold M. Salzberg, M.D., C. Paul Boyan, M.D., and Lazar J. Greenfield, M.D. ABSTRACT Carbon dioxide retention in the Storz rigid ventilating bronchoscope with the Hopkins lens system was investigated in the laboratory. The 3.5, 4.0, and 5.0 30-cm Storz bronchoscopes with a 3.95-mm (outside diameter) telescope lens were used in 10 mongrel dogs weighing between 8 and 15 kg. Significant (p < 0.01) accumulation of arterial carbon dioxide tension (PaCO,) (respiratory acidosis) was observed after 5 and 10 minutes of ventilation through the 3.5 and 4.0 bronchoscopes, but no significant increase in PaCO, was noted with the 5.0 bronchoscope. There was no significant change in arterial oxygen tension under the same conditions. Manual compression of the upper anterior abdominal wall during expiration was applied during bronchoscopy in 6 children. Arterial blood samples were taken before insertion of the bronchoscope and 5 minutes later with and without abdominal compression during expiration. A significant increase (p < 0.05) in PaCO, and a decrease in ph were observed after 5 minutes of the bronchoscopic procedure without manual compression of the abdominal wall, while no significant changes in PaC0, were observed with abdominal compression. The Storz rigid ventilating bronchoscope with the Hopkins lens system is indispensable in pediatric operations. The ventilating channel (the space between the telescope lens and the bronchoscope) in the 2.5,3.0,3.5, and 4.0 bronchoscope is small, and high inspiratory pressures are required to deliver a fixed volume of gas. In infants, passive pulmonary expiratory pressures and chest wall recoil may not be ca- From the Departments of Anesthesiology and Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA. Presented at the Twenty-fourth Annual Meeting of the Southern Thoracic Surgical Association, ov 3-5, 1977, Marco Island, FL. Address reprint requests to Dr. Rah, MCV Box 878, Richmond, VA 23298. pable of expelling the inspired gas through the ventilating channel in a closed anesthetic system. Gas trapping with carbon dioxide (CO,) retention and acidosis seemed a reasonable possibility and was investigated in the laboratory with mongrel dogs. Material and Method Ten mongrel dogs weighing from 8 to 15 kg (mean, 10.8 f 2.86 kg) were anesthetized with pentobarbital, 15.34 f 0.88 mg per kilogram of body weight, administered intravenously and paralyzed with dimethyl tubocurarine chloride, 0.3 mg per kilogram. Cannulation of the femoral arteries allowed constant monitoring of arterial pressure and sampling of blood gas. In each dog, the trachea was intubated with a 6.0 mm (inner diameter) Shiley endotracheal tube with the cuff inflated to provide a leak-free system. After 5 minutes of controlled mechanical ventilation with a tidal volume of 12.88 f 1.40 ml per kilogram of body weight and a respiratory rate of 20 times per minute, a control arterial blood sample was taken. The 3.5, 4.0, and 5.0 30-cm Storz bronchoscopes with a telescope lens of 3.95 f 0.05 mm (outside diameter) were utilized in this study. A disposable endotracheal cuff was placed around the bronchoscope above the uppermost side vent to duplicate the closed anesthetic system that occurs clinically (Fig 1). The antifog tube was not used. The suction orifice was occluded. The ventilating connection of the bronchoscope was attached to a circle CO, abs.orption anesthesia system with an Air Shields respirator (Fig 2). An airway pressure monitor and a Wright spirometer were incorporated into the system. Oxygen was supplied at a flow rate of 4 liters per minute. The respiratory rate was set by adjusting the respirator, while the spirometer measured tidal volume. 197 0003-49751791030197-06$01. 25 0 1978 by Kang H. Rah
198 The Annals of Thoracic Surgery Vol 27 o 3 March 1979 u u A Fig 1. Storz-Hopkins bronchoscope with antifog tube. A disposable cuff (C) is placed around the bronchoscope. (A = anesthesia attachment; L = connection for light source; 0 = connection for oxygen flow to antifog tube; PLD = prismatic light deflector; S = suction or instrumentation channel; V = side vents of bronchoscope.) For each dog, one of the three sizes of bronchoscope was selected at random and inserted into the trachea after the endotracheal tube was removed. This maneuver required less than 45 seconds. The bronchoscope was connected to the breathing system. Respiratory rate and tidal volume were maintained at control values. Arterial blood samples for gas analysis were taken at 5 and 10 minutes. After the last blood sample was taken, the bronchoscope was removed from the trachea and was replaced with the endotracheal tube used previously. Ventilation again was maintained mechanically with control values of tidal volume and rate. After 5 minutes, another blood sample was taken to provide control values for the second bronchoscope. The same procedure was repeated with the third and final bronchoscope. The arterial blood samples were analyzed for arterial oxygen tension (PaO,), arterial carbon dioxide tension (PaCO,), ph, and the bicarbonate radi- cal (HC03) by the same technician using an Instrumentation Laboratories Micro-13 blood gas analyzer. Results The changes in PaO,, PaCO,, ph, and HC03 from control to 5 minutes, 5 to 10 minutes, and control to 10 minutes with the three sizes of bronchoscope were analyzed biostatistically using Duncan's multiple range test. The statistical differences between the three sizes were also tested by the same method using PaO,, PaCO,, ph, and HC03 as the variables. PaOz There were no significant differences (p < 0.01) in PaO, from control to 5 minutes, 5 to 10 minutes, and control to 10 minutes for the different sizes of bronchoscopes (Table 1). At 5 and 10 minutes there were no significant differences (p < 0.01) in PaO, between bronchoscope sizes 3.5 and 4.0, 4.0 and 5.0, or 3.5 and 5.0. PaCOz There were significant increases (p < 0.01) in PaC0, from control to 5 minutes and control to 10 minutes with the size 3.5 and 4.0 broncho-' scopes, but no significant changes were seen with the size 5.0 bronchoscope (Table 2). At
199 Rah et al: Respiratory Acidosis with Small Storz-Hopkins Bronchoscopes GS Fig 2. Storz-Hopkins pediatric bronchoscope with anesthesia ventilating system. Arrows indicate direction of gas flow. (GS = gas supply from anesthesia machine; SL = soda lime; ASR = Air Shields respirator; IV = inspiratory valve; EV = expiratory valve; IL = inspiratory limb; EL = expiratory limb; AP = airway pressure monitor; SP = Wright spirometer; S-H = Storz- Hopkins bronchoscope; TR = dog's trachea.) 5 and 10 minutes there were significant differences (p < 0.01) in PaCOz between bronchoscope sizes 4.0 and 5.0, and 3.5 and 5.0, but no significant difference was seen between the 3.5 and 4.0 bronchoscopes at any time. HCO, There were significant increases (p < 0.01) in HCO, from control to 5 minutes, and control to 10 minutes with the size 3.5 bronchoscope, while no significant changes were seen with sizes 4.0 and 5.0 (Table 3). At 5 minutes there was a significant difference ( p < 0.01) in HC03 between sizes 3.5 and 5.0, while no differences were seen between sizes 3.5 and 4.0, and 4.0 and 5.0. PH There were significant differences ( p < 0.01) in ph from control to 5 minutes, and control to 10 minutes with the size 3.5 and 4.0 bronchoscopes, but with the size 5.0 a significant difference was seen only from control to 10 minutes (Table 4). At 5 and 10 minutes, there were significant differences (p < 0.01) in ph be-
200 The Annals of Thoracic Surgery Vol 27 o 3 March 1979 Table 1. Mean (fsd) PaOz Changes in Different Sized Storz-Hopkins Bronchoscopes PaOz Values (mm Hg) Time Significance Com- Signif- Size Size C 5 min 10 min parison icance Comparison C 5 min 10 min 3.5 518.5f 544.6f 535.5f C-5 (n = 10) 112.40 90.69 70.57 5-10 4.0 513.9f 543.0f 533.5f C-5 (n = 10) 116.51 98.64 106.56 5-10 5.0 473.8f 523.5f 536.0f C-5 (n = 10) 111.91 108.48 109.49 5-10 3.5-4.0 4.0-5.0 3.5-5.0 SD = standard deviation; PaOz = arterial oxygen tension; C = control; = not statistically significant at 0.01 level. Table 2. Mean (fsd) PaCo, Changes in Different Sized Storz-Hopkins Bronchoscopes PaC02 Values (mm Hg) Time Significance Com- Signif- Size Size C 5 min 10 min parison icance Comparison C 5 min 10 min 3.5 29.20f 55.45f 67.30f C-5 (n = 10) 12.41 16.93 18.22 5-10 4.0 29.755 50.00f 58.35+ C-5 (n = 10) 8.50 11.29 14.78 5-10 5.0 27.65f 33.45f 37.85f C-5 (n = 10) 7.41 9.31 10.65 5-10 3.54.0 4.0-5.0 S S 3.5-5.0 S S SD = standard deviation; PaCOZ = arterial carbon dioxide pressure; C = control; S = statistically significant at 0.01 level; = not statistically significant at 0.01 level. Table 3. Mean (fsd) HCO, Changes in Different Sized Storz-Hopkins Bronchoscopes HC03 Values Time Significance Com- Signif- Size Size C 5 min 10 min parison icance Comparison C 5 min 10min 3.5 22.73f 28.45f 28.56+ C-5 (n = 10) 6.28 5.21 5.34 5-10 4.O 23.18f 26.38f 26.37+ C-5 (n = 10) 4.55 4.75 3.95 5-10 5.0 21.74f 22.38f 24.10f C-5 (n = 10) 3.89 4.24 4.93 5-10 S S 3.54.0 4.0-5.O 3.5-5.O S SD = standard deviation; HCO, = bicarbonate radical; C = control; S = statistically significant at 0.01 level; = not statistically significant at 0.01 level.
201 Rah et al: Respiratory Acidosis with Small Storz-Hopkins Bronchoscopes Table 4. Mean (fsd) ph Changes in Different Sized Storz-Hopkins Bronchoscopes 3.5 7.54+ 7.31+ 7.26+ C-5 S (n = 10) 0.09 0.07 0.06 5-10 S 4.O 7.53+ 7.35+ 7.28f C-5 S (n = 10) 0.08 0.12 0.06 5-10 S 5.0 7.52+ 7.45+ 7.44+ C-5 (n = 10) 0.08 0.06 0.05 5-10 S 3.5-4.0 4.0-5.0 S S 3.5-5.0 S S tween sizes 4.0 and 5.0, and 3.5 and 5.0. o difference was seen between the 3.5 and 4.0 bronchoscopes. Comment The pediatric bronchoscope with the Hopkins lens system provides clear, bright, and wideangle visualization of the upper tracheobronchial tree. The space between the lens, with and without the antifogging cover, and the inner wall of the sheath is used for exchange of ventilatory air. A closed ventilating system is achieved with this bronchoscope, and the patient can be ventilated manually or mechanically. Inhalation anesthetics utilize the same channel. The Storz bronchoscopes of designated sizes 3.5, 4.0, and 5.0 actually have inner diameters of 5.20, 6.31, and 7.10 mm, respectively.* The outside diameter of the telescope lens is 3.95 f 0.05 mm, to which is added the thickness of the antifog sleeve. Thus, the 3.5 bronchoscope has a ventilatory space of less than 1.25 mm; the4.0, less than 2.36 mm; and the 5.0 bronchoscope, less than 3.15 mm. This small lumen can create difficulty for satisfactory ventilation, as calculated by modifying the formula of Grossman and colleagues [31. Significant accumulation of PaC0, (respiratory acidosis) was observed after 5 and 10 minutes of ventilation through the 3.5 and 4.0 bronchoscopes, while there was no significant increase in PaCO, with the 5.0 bronchoscope. Karl Storz Endoscopy-America, Inc: Personal communication, 1977. In this study, the rate of increase in PaC0, during the first 5 minutes of ventilation with the 3.5 and 4.0 bronchoscopes was 6.05 and 4.05 mm Hg per minute, respectively. However, the overall rise in PaC0, during the 10 minutes of ventilation was 3.81 mm Hg per minute with the 3.5 bronchoscope and 2.86 mm Hg per minute with the 4.0 bronchoscope. With the 5.0 bronchoscope, the mean PaCOz was satisfactory at 33.45 k 9.31 mm Hg at 5 minutes and 37.85 k 10.65 mm Hg at 10 minutes (see Table 2). The mean Pa02 for all dogs but 1 was higher than 500 mm Hg so that oxygenation was very adequate. The decrease in ph seen at 5 minutes with the 3.5 bronchoscope and at 10 minutes with the 3.5 and 4.0 bronchoscopes can be explained by COz retention. Metabolic acidosis may account for the decrease in ph at 10 minutes without an increase in PaC0, with the larger 5.0 bronchoscope. In the laboratory with paralyzed dogs, passive expiratory pressure cannot expel inspired air through the small ventilating space in the 3.5 and 4.0 Storz bronchoscopes. The hypercapnia so produced can be tolerated by healthy patients [l]. However, it can produce cardiac arrhythmias [51, hypertension 12, 41, or hypotension [ll in seriously ill or cardiac patients, and an increase in intracranial pressure [6]. The prevention and treatment of this CO, accumulation and respiratory acidosis might include rapid bronchoscopy, hyperventilation before insertion of the bronchoscope, release of the instrument channel during expiration, and intermittent removal of the telescope lens. In
202 The Annals of Thoracic Surgery Vol 27 o 3 March 1979 Table 5. PaC02 Changes with or without Abdominal Compression during Expiration in 6 Pediatric Patients WITHOUT ABDOMIAL COMPRESSIO Time Mean Mean (min) PaCOz SD Difference Probability C 35.50 5.99 5 56.50 19.30-21.00 0.029 WITH ABDOMIAL COMPRESSIO C 40.33 5.64 5 46.00 9.70-5.67 0.24 asignificant at 0.05 level. PaCOZ = arterial carbon dioxide tension; SD = standard deviation; C = control. addition, manual compression of the upper anterior abdominal wall during expiration should prevent respiratory acidosis. This was tried in 6 patients who were 11 months to 5 years old and weighed 6 to 15 kg. Five of these patients had suspected tracheal stenosis, and 1 had cystic fibrosis. Bronchoscopes of various sizes were used (3.5 mm, 20 cm in 4 patients; 4.0 mm, 30 cm in 1; and 5.0 mm, 30 cm in 1). General anesthesia was administered utilizing 100% oxygen and 1-3% halothane using the Jackson Rees modified T-piece anesthesia system. Respiration was controlled in all patients with or without the use of intermittent intravenous injections of succinylcholine. The other procedures duplicated those used in the laboratory except that the airtight system was obtained without an endotracheal cuff. Six bronchoscopies were done without manual compression of the abdominal wall and served as controls. A few days later, the same patients underwent bronchoscopy again with manual compression of the upper abdominal wall during expiration. Arterial blood samples were analyzed for PaO,, PaCO,, ph, and HCO, by the same technician using the Instrumentation Laboratories Micro-13 gas analyzer. The arterial blood samples were taken before insertion of the bronchoscope and 5 minutes later. A significant increase (p < 0.05) in PaC02 and decrease in ph were observed after 5 minutes of bronchoscopic examination without manual compression of the abdominal wall during expiration (Table 5). Arterial oxygenation was adequate in all patients. When manual compression of the abdominal wall was applied during expiration, there were no significant changes in the measured arterial variables. The results of the laboratory studies indicate that dogs weighing 8 to 15 kg can be well oxygenated through 3.5,4.0, and 5.0 Storz bronchoscopes by using l0oo/o oxygen and artificial ventilation. A statistically significant (p < 0.01) retention of CO, occurs with the smaller 3.5 and 4.0 bronchoscopes while none was observed with the size 5.0 under the same conditions. Manual compression of the upper anterior abdominal wall during expiration prevented CO, accumulation in infants in whom the 3.5 and 4.0 Storz bronchoscopes were used. References 1. Clowes G, Sabga G, Konttaxis A, et al: Effects of acidosis on cardiovascular function in surgical patients. Ann Surg 154:524, 1961 2. Cullen D, Eger E Jr: Cardiovascular effects of carbon dioxide in man. Anesthesiology 41:345, 1974 3. Grossman E, Jacobi A: Minimal optimal endotracheal tube size for fiberoptic bronchoscopy. Anesth Analg (Cleve) 53:475, 1974 4. Hoffman S, Bruderman I: Blood-pressure and blood-gas changes during anesthesia for bronchoscopy using a modified method of ventilation. Anesthesiology 37:95, 1972 5. Jenkins V: Electrocardiographic findings during bronchoscopy. Anaesthesia 21:449, 1966 6. Shapiro H: Intracranial hypertension: therapeutic and anesthetic considerations (review article). Anesthesiology 431445, 1975