Two-lung Ventilation Research Articles

Double lumen tube location predicts tube malposition and hypoxaemia during one lung ventilation

Poor positioning of an endobronchial double lumen tube (DLT) could affect oxygenation during one lung ventilation (OLV). We set out to relate DLT position to hypoxaemia and DLT misplacement during OLV. We recruited 152 ASA physical status I-II patients about to have elective thoracic surgery. The trachea was intubated with a left-sided DLT. Tube position was assessed by fibre-optic scope and correction was made after patient positioning and during OLV. If Pa(O(2)) was less than 10.7 kPa, the DLT position was checked and then PEEP, continuous positive airway pressure (CPAP), oxygen insufflation, or two lung ventilation (TLV) were tried. The DLT was found to be misplaced in 49 patients (32%) after patient positioning, and in 38 patients (25%) during OLV. PEEP to the dependent lung, CPAP or apneic oxygen insufflation to the non-dependent lung, or brief periods of TLV, were applied in 46 patients (30%). Patients who had DLT malposition after placing the patient in the lateral position had a greater incidence of DLT malposition during OLV (59 vs 9%) and also required each intervention more frequently (57 vs 10%). Patients with DLT malposition during OLV also required interventions more often (84 vs 12%). Patients who have DLT malposition after placing the patient in the lateral position had more DLT malposition during OLV and hypoxaemia during OLV.

Effects of thoracic epidural meperidine on arterial oxygenation during one-lung ventilation in thoracic surgery

Objective: To compare the effects that the use of general intravenous anesthesia (propofol-fentanyl) (GA) or general anesthesia combined with thoracic epidural anesthesia with meperidine (TEA-M) may have on arterial oxygenation during one-lung ventilation (OLV). Design: Prospective. Setting: Tertiary care hospital. Participants: Seventy-two patients undergoing OLV for thoracic surgery. Interventions: Patients were prospectively randomized into two groups: GA (n = 37) fentanyl, propofol, rocuronium anesthesia was used; and group TEA-M (n = 35) were anesthetized with propofol, rocuronium and thoracic epidural meperidine (2 mg/kg in 10–12 mL) administered before anesthetic induction. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during study. Mean arterial pressure, heart rate and arterial and venous blood gases were recorded with the patients in the lateral decubitus position in three phases: during two-lung ventilation (TLV), 15 and 30 minutes after beginning OLV (OLV + 15 and OLV + 30 respectively). The authors measured arterial and venous central oxygen tension, arterial and venous central oxygen saturation, arterial and venous central oxygen content and venous admixture percentage (Qs/Qt%). Measurements and Main Results: There were no statistical differences between the two groups for PaO 2 during OLV + 15 (GA = 165 mmHg, TEA-M = 153 mmHg) and OLV + 30 (GA = 176 mmHg, TEA-M = 158 mmHg); and with values for Qs/Qt%. Conclusions: It is concluded that GA combined with TEA-M (2 mg/kg) do not affect arterial oxygenation during OLV in thoracic surgery.

Alterations of the Ventilation-Perfusion Ratio Measured by Using a Multiple Inert Gas Elimination Technique (MIGET) in One Lung Ventilated Rabbit

Background: In this study, we performed one-lung ventilation (OLV) in rabbits to assess the effects of OLV on the / ratio and the respiratory physiological changes using MIGET. Methods: Ten male New Zealand white rabbits, weighing 3-4 kg were selected. To perform MIGET, six inactive gases (SF, krypton, desflurane, enflurane, diethyl ether, acetone) in 500 ml normal saline were injected intravenously. During two-lung ventilation (TLV), and after OLV for 30 minutes, blood was sampled for blood gas analysis and MIGET, hemodynamic variables were measured. For MIGET, the concentrations of the injected inert gases were measured and converted to retention/excretion data; the / distribution curve was obtained using a computer. Results: Systolic, mean, and diastolic pulmonary pressures were elevated significantly and pulmonary resistance was doubled (P ＜ 0.05) in OLV compared to TLV. Blood pH decreased in OLV. The calculated intrapulmonary shunt was 19% and 52%, TLV and OLV, respectively. The analysis of / using MIGET showed that the / distribution curve was wider and that the / area was larger in normal rabbits. And, that intrapulmonary shunt approximated to 11%. In the case of OLV, a significant increase in shunt was observed but no change in the amount of dead space at distribution area, (log SD, log SD) remained the same, whereas the / distribution curve shifted toward the right. Conclusions: OLV in rabbits showed severe hypercapnia and hypoxemia leading to a considerable increase in shunt. Because of the wide range of / distribution in TLV, no significant changes in respiratory variables were observed during OLV.

Contralateral Tension Pneumothorax During One-Lung Ventilation for Lobectomy: Diagnosis Aided by Fiberoptic Bronchoscopy

Contralateral Tension Pneumothorax During One-Lung Ventilation for Lobectomy: Diagnosis Aided by Fiberoptic Bronchoscopy

Alveolar recruitment strategy increases arterial oxygenation during one-lung ventilation

Background. Deterioration of gas exchange during one lung ventilation (OLV) is caused by both total collapse of the nondependent lung and partial collapse of the dependent lung. A previous report demonstrated that an alveolar recruitment strategy (ARS) improves lung function during general anesthesia in supine patients. The objective of this article was to study the impact of this ARS on arterial oxygenation in patients undergoing OLV for lobectomies.Methods. Ten patients undergoing open lobectomies were studied at three time points: (1) during two-lung ventilation (TLV), (2) during OLV before, and (3) after ARS. The ARS maneuver was done by increasing peak inspiratory pressure to 40 cm H2O, together with a positive end-expiratory pressure (PEEP) of 20 cm H2O for 10 respiratory cycles. After the maneuver, ventilation parameters were returned to the settings before intervention.Results. During OLV, Pao2 was statistically lower before the recruitment (data as median, first, and third quartile, 217 [range 134 to 325] mm Hg) compared with OLV afterwards (470 [range 396 to 525] mm Hg) and with TLV (515 [range 442 to 532] mm Hg). After ARS, Pao2 values during OLV were similar to those during TLV. During OLV, the degree of pulmonary collapse in the nondependent lung, the hemodynamic status, and the ventilation parameters were similar before and after ARS.Conclusions. Alveolar recruitment of the dependent lung augments PaO2 values during one-lung ventilation.

Anaesthesia for thoracoscopic surgery

The surgical requirement for thoracoscopy is a good view of the contents of the thorax. This is achieved by capitalizing on natural consequences and the skills of anaesthesiologists to produce a pneumothorax and collapse the ipsilateral lung – a process that is commonly enhanced by insufflating carbon dioxide.Insufflating CO2 to actively promote lung collapse creates the dynamics of a tension pneumothorax. Complications are clinically insignificant if CO2 is used judiciously.There is a body of experience using ordinary endotracheal tubes and two-lung ventilation. Techniques of one-lung ventilation are more widely reported.All the factors known to contribute to the significant increase in shunt fraction associated with one-lung ventilation apply. The manoeuvre of collapsing a lung is no longer regarded as benign. Chemical attempts to produce a reversible post-pneumonectomy pulmonary circulation have not been shown to be an improvement.Post-operative pain can be severe. The mechanism is not defined but it differs from that associated with thoracotomy. Epidural analgesia and opioids may be required. Chronic pain syndromes have been described as complications.

A Comparison of the Effects of Isoflurane Verus Propofol Anesthesia on Blood Gas Parameters during One Lung Ventilation for Lung Surgery

Background: During one-lung ventilation (OLV) for thoracic surgery, hypoxic pulmonary vasoconstriction (HPV) may reduce venous admixture and ameliorate the decrease in arterial oxygenation by diverting blood from the non-ventilated to the ventilated lung. Volatile anesthethics are the drugs of choice in thoracic surgery despite numerous experimental data showing their inhibiting effect on the HPV. The object of the present study was to compare the effects of propofol with those of isoflurane on oxygenation & shunt during two lung ventilation (TLV) and OLV in human volunteers.Methods: Thirty patients who needed OLV for an elective thoracic surgery were randomly assigned to receive either isoflurane (1 MAC isoflurane + fentanyl + vecuronium, n = 15) or propofol (2-3g/ dl propofol + fentanyl + vecuronium, n = 15) with 100% oxygen in separate groups. Systemic hemodynamic data was recorded, and blood gas values were obtained 30 min after the start of TLV (TLV-30) and 30, 45 and 60 min after the start of OLV (OLV-30, 45, 60) in the lateral position. Results: A significant reduction in PaO2 and increase in shunt fractions at all study times after the start of OLV compared with TLV were observed in both groups at OLV-30, 45 and 60. Percent changes of PaO2 and shunt of OLV-60 to those of TLV-30 were less in the propofol group than the isoflurane group. Other blood gas data (SaO, S￣ｖO, PaCO, P￣ｖCO, pH, Hb, CaO2 and C￣ｖO) and systemic hemodynamics (mean arterial blood pressure, heart rate and central venous pressure) were not different after the start of OLV compared with TLV in either group. Conclusions: TIVA with propofol was superior than isoflurane anesthesia in terms of arterial blood oxygenation and pulmonary shunting during OLV for lung surgery.

Capnography and Severe COPD

To The Editor: The influences of chronic obstructive pulmonary disease (COPD) on end-tidal CO2 concentration (ETco2) monitoring are well known and consist primarily of the appearance of a significant gradient Paco2/ETco2 secondary to the increase of the alveolar dead space, and the appearance of an ascending capnogram, of which the slope is proportional to the degree of expiratory airway obstruction (1). The extreme stressing of these phenomena can lead to surprising clinical presentations, one of which is described below. A 51-yr-old female patient was scheduled for bilateral thoracoscopic lung reduction for severe postnicotinic bronchoemphysema. Preoperatively, forced vital capacity and FEV1 were 58% and 16%, of normal values, respectively, and Pao2 and Paco2 in air were 59 and 46 mm Hg, respectively. Ventilation and perfusion ratios were respectively 33% and 34% for the left lung and 67% and 66% for the right lung. Anesthesia consisted of a combined thoracic epidural analgesia and general anesthesia that included propofol, sufentanil, and cisatracurium. The trachea was easily intubated with a 37-ch left double-lumen endotracheal tube, of which the right positioning was checked by fibroscopy. Ventilation was controlled with a Fio2 of 0.5, with a maximal peak pressure limit set to 30 cm H2O, at a frequency of 12 breaths/min. Ten minutes after initiation of the mechanical ventilation, ETco2 was 31 mm Hg for a Paco2 value of 47 mm Hg. The operation was performed in dorsal decubitus. The left pulmonary reduction was uneventfully achieved in 68 min during one-lung ventilation. The right thoracoscopy was then started after the exclusion of the right lung. The total absence of a reading on the capnogram was noticed concomitant to the development of increased insufflation pressure and a decrease of tidal volume (120 mL). The permeability of both the endotracheal tube and the left bronchial tree were then checked again by fibroscopy. Surprisingly, the Sao2 remained normal. The reventilation of the right lung systematically allowed the reappearance of breathed out CO2 as well as a slight increase of the tidal volume, whereas the left one-lung ventilation was always associated with a “flatline” capnogram. The examination of the patient did not reveal the cause of this problem. The thoracic drain of the left side had a moderate air leak, but this could not explain the clinical picture by itself. It was then noticed that a several-seconds period of apnea resulted in a very slow appearance of CO2 coming from the left lung. Obviously, the degree of expiratory obstruction of the left lung airway were such that the extent of the ascending inclination of the ETco2 did not allow the appearance of CO2 while breathing out before occurrence of the next ventilatory cycle (Fig. 1). The reason for this was probably a result of the severity of the broncoemphysematic pathology on the left side, increased by the fact that this lung had been previously nonventilated during 68 min, which most certainly caused a slight interstitial edema, worsening the degree of stenosis of the small airways. Last, the presence of the bronchopleural air leak could explain the persistence of moderate alveolar ventilation although no ETco2 has been measured. Obviously, our patient was hypoventilated (maximum Paco2 value of 70.7 mm Hg) because of the important increase of the insufflation pressures of the left side and the subsequent decreasing of its tidal volume, but its oxygenation remained satisfactory. Finally, the right pulmonary reduction was completed in 50 min. The return to two-lung ventilation allowed the reappearance of ETco2, and the trachea could finally be extubated just after the procedure.Figure 1: ETco2 (upper curve) and airway pressure (lower curve) trends showing absence of capnogram during mechanical ventilation (small arrows) and progressive appearance of ETco2 during a period of apnea (large arrow) resulting from severe expiratory airway obstruction.In conclusion, the absence of capnographic reading in patients showing severe COPD is not an absolute indicator of no ventilation. Serge M. Broka, MD Sihem Boujlel, MD

Relation of the Static Compliance Curve and Positive End-expiratory Pressure to Oxygenation during One-lung Ventilation

Positive end-expiratory pressure (PEEP) is commonly applied to the ventilated lung to try to improve oxygenation during one-lung ventilation but is an unreliable therapy and occasionally causes arterial oxygen partial pressure (PaO(2)) to decrease further. The current study examined whether the effects of PEEP on oxygenation depend on the static compliance curve of the lung to which it is applied. Forty-two adults undergoing thoracic surgery were studied during stable, open-chest, one-lung ventilation. Arterial blood gases were measured during two-lung ventilation and one-lung ventilation before, during, and after the application of 5 cm H(2)O PEEP to the ventilated lung. The plateau end-expiratory pressure and static compliance curve of the ventilated lung were measured with and without applied PEEP, and the lower inflection point was determined from the compliance curve. Mean (+/- SD) PaO(2) values, with a fraction of inspired oxygen of 1.0, were not different during one-lung ventilation before (192 +/- 91 mmHg), during (190 +/- 90), or after ( 205 +/- 79) the addition of 5 cm H(2)O PEEP. The mean plateau end-expiratory pressure increased from 4.2 to 6.8 cm H(2)O with the application of 5 cm H(2)O PEEP and decreased to 4.5 cm H(2)O when 5 cm H(2)O PEEP was removed. Six patients showed a clinically useful (> 20%) increase in PaO(2) with 5 cm H(2)O PEEP, and nine patients had a greater than 20% decrease in PaO(2). The change in PaO(2) with the application of 5 cm H(2)O PEEP correlated in an inverse fashion with the change in the gradient between the end-expiratory pressure and the pressure at the lower inflection point (r = 0.76). The subgroup of patients with a PaO(2) during two-lung ventilation that was less than the mean (365 mmHg) and an end-expiratory pressure during one-lung ventilation without applied PEEP less than the mean were more likely to have an increase in PaO(2) when 5 cm H(2)O PEEP was applied. The effects of the application of external 5 cm H(2)O PEEP on oxygenation during one-lung ventilation correspond to individual changes in the relation between the plateau end-expiratory pressure and the inflection point of the static compliance curve. When the application of PEEP causes the end-expiratory pressure to increase from a low level toward the inflection point, oxygenation is likely to improve. Conversely, if the addition of PEEP causes an increased inflation of the ventilated lung that raises the equilibrium end-expiratory pressure beyond the inflection point, oxygenation is likely to deteriorate.

Gas Exchange and Pulmonary Hemodynamics During Lung Resection in Patients at Increased Risk: Relationship With Preoperative Exercise Testing

Study objectivesTo evaluate the intraoperative evolution of patients with COPD during lung resection and to test whether exercise testing could be helpful in the prediction of the intraoperative course. DesignProspective study. SettingUniversity teaching hospital. PatientsForty patients (mean [± SD] age, 65 ± 9 years) with COPD (ie, FEV1, 55 ± 11% of predicted) and resectable lung neoplasms. InterventionsPreoperatively, pulmonary function testing, quantitative lung perfusion scanning, and exercise performance testing were administered. Intraoperatively, pulmonary, hemodynamic, and blood gas measurements were performed at five stages, including periods of two-lung ventilation (TLV) and periods of one-lung ventilation (OLV). ResultsDuring OLV, compared with TLV, the Pao2/fraction of inspired oxygen (Fio2) ratio decreased from 458 ± 120 to 248 ± 131 mm Hg (p < 0.05), whereas pulmonary artery pressure (PAP) increased from 18 ± 5 to 23 ± 5 mm Hg (p < 0.05). Cardiac output (▪t) also increased from 4.0 ± 1.2 to 5.1 ± 1.9 L/min (p < 0.05), yielding to a higher mixed venous Po2. Both Pao2 and ▪t during OLV were significantly lower in patients who had undergone right thoracotomies compared with those who had undergone left thoracotomies. The Pao2/Fio2 ratio during OLV correlated with the Pao2 during exercise (r = 0.39; p = 0.01) and with the perfusion of the non-neoplastic lung (r = 0.44; p = 0.005). ConclusionsIn COPD patients, OLV leads to a significant derangement of gas exchange, which is more pronounced in right thoracotomies. Preoperative measurement of Pao2 during exercise and the distribution of perfusion by lung scan might be useful to identify those patients who are at the greatest risk of abnormal gas exchange during lung resections.

Techniques and complications of one-lung ventilation in children with suppurative lung disease: Experience in 15 cases

Objective: To evaluate lung isolation with Fogarty catheters and to analyze respiratory consequences of one-lung ventilation (OLV) in children with suppurative lung disease. Dign: Prospective. Setting: University hospital. Participants: Fifteen children undergoing thoracotomy. Interventions: Bronchial blockade with a 7F Fogarty catheter was attempted. In case of incomplete blockade or failure in directing the catheter into the desired mainstem bronchus, endobronchial intubation was done. Volume-controlled ventilation was performed with fraction of inspired oxygen (FIO2), 0.5; inspiratory-to-expiratory (I: E) ratio, 1:2; and 10 mL/kg tidal volume during two-lung ventilation (TLV). FIO2 was increased to 1.0 by the initiation of OLV. If peak airway pressure exceeded basal values during TLV by 35%, tidal volume was reduced to 8 mL/kg, inspiratory pause was zeroed, and I:E ratio was increased to 1:1. Hemodynamic and respiratory parameters were recorded during TLV and 30 minutes after initiation of OLV. Peripheral oxygen saturation and end-tidal carbon dioxide tension were recorded every 5 minutes. Measurements and Main Results: Right lung isolation was successfully obtained by Fogarty catheters in 10 children undergoing right thoracotomy. Endobronchial intubation was performed in 2 children (40%) undergoing left thoracotomy. Three children (20%) developed episodes of severe hypercapnia and hypoxia requiring treatment during OLV. All of the parameters recorded at 30 minutes of OLV revealed statistically significant differences from TLV. OLV was transiently discontinued in 1 child. Conclusion: The use of Fogarty embolectomy catheters for lung isolation in children undergoing thoracotomy is recommended. Respiratory problems are not rare during OLV in children with suppurative lung disease and require immediate management. Copyright © 2001 by W.B. Saunders Company

Thoracic Epidural Anesthesia Combined with General Anesthesia: The Preferred Anesthetic Technique for Thoracic Surgery

Thoracic epidural anesthesia (TEA) combined with general anesthesia (GA) as well as total-IV anesthesia (TIVA) are both established anesthetic managements for thoracic surgery. We compared them with respect to hypoxic pulmonary vasoconstriction, shunt fraction and oxygenation during one-lung ventilation. Fifty patients, ASA physical status II-III undergoing pulmonary resection were randomly allocated to two groups. In the TIVA group, anesthesia was maintained with propofol and fentanyl. In the TEA group, anesthesia was maintained with TEA (bupivacaine 0.5%) combined with low-dose concentration 0.3-0.5 vol% of isoflurane (end-tidal). Changing from two-lung ventilation to one-lung ventilation caused a significant increase in cardiac output (CO) in the TIVA group, whereas no change was observed in the TEA group. One-lung ventilation caused significant increases in shunt fraction in both groups which was associated per definition with a significant decrease in PaO(2) in both groups but PaO(2) remained significantly increased in the TEA group (P < 0.05). We conclude that both anesthetic regimens are safe intraoperatively. However, TEA in combination with GA did not impair arterial oxygenation to the same extent as TIVA, which might be a result of the changes in CO. Therefore, patients with preexisting cardiopulmonary disease and impaired oxygenation before one-lung ventilation might benefit from TEA combined with GA. Fifty patients underwent lung surgery through the opened chest wall requiring ventilation of only one lung. Patients were randomly assigned to receive either general anesthesia alone or in combination with regional anesthesia via a catheter in the back. Oxygen content in the blood and blood pressure was better maintained in the group receiving the combination of general with regional anesthesia.

Effects of sevoflurane and propofol on pulmonary shunt fraction during one-lung ventilation for thoracic surgery

Forty patients requiring one-lung ventilation (OLV) for thoracic surgery were randomly assigned to receive propofol (4-6 mg kg(-1) h(-1)) or sevoflurane (1 MAC) for maintenance of anaesthesia. Three sets of measurements were taken: (i) after 30 min of two-lung ventilation (TLV), (ii) after 30 min of one-lung ventilation (OLV-1) in the supine position and (iii) during OLV in the lateral position (OLV-2) with the chest open and before surgical manipulation of the lung. There were no differences between groups in patient characteristics or preoperative condition. Increases in shunt fraction during OLV-1 were 17.4% and 17.2% (P=0.94), those during OLV-2 were 18.3% and 16.5% (P=0.59) for the propofol and sevoflurane group, respectively. Cardiac index and other haemodynamic and respiratory variables were similar for the two groups. We conclude that inhibition of hypoxic pulmonary vasoconstriction by sevoflurane may only account for small increases in shunt fraction and that much of the overall shunt fraction during OLV has other causes.

Lung isolation for the prevention of air embolism in penetrating lung trauma. A case report

To illustrate a new airway and ventilatory management strategy for patients with unilateral penetrating lung injury. Emphasis is placed on avoiding positive pressure ventilation (PPV)-induced systemic air/gas embolism (SAE) through traumatic bronchiole-pulmonary venous fistulas. A 14-yr-old male, stabbed in the left chest, presented with hypovolemia, left hemopneumothorax, an equivocal acute abdomen, and no cardiac or neurological injury. In view of the risk of SAE, we did not ventilate the left lung until any fistulas, if present, had been excised. After pre-oxygenation, general anesthesia was induced and a left-sided double-lumen tube (DLT) was placed to allow right-lung ventilation. Bronchoscopy was performed. The surgeons performed a thorascopic wedge resection of the lacerated lingula. Upon completion of the repair, two-lung ventilation was instituted while the ECG, pulse oximetry, PETCO2, and blood pressure were monitored. Peak inflation pressure was increased slowly and was well tolerated up to 50 cm H2O. The patient's intravascular status was maintained normal. Patients with lung trauma are at risk of developing SAE when their lungs are ventilated with PPV. In a unilateral case, expectant non-ventilation of the injured lung until after repair is recommended.

Videoendoscopic thoracic aorta-to-femoral artery bypass in the pig.

The thoracoscopic approach to the aorta has the advantages of easy aortic dissection, excellent inflow, improved exposure in the thorax without insufflation, and ability to employ both laparoscopic and traditional instruments. Our aim was to develop a thoracoscopic technique for descending thoracic aorta-to-femoral artery bypass (TAFB) in the pig that results in acceptable short-term survival and graft patency. Thoracoscopic TAFB was performed in 11 pigs. Using two-lung ventilation, the animals were placed in a 45 degrees left lateral semidecubitus position. A fan lung retractor, two dissecting ports, intercostal artery loops, and camera were placed through five 10- to 20-mm thoracoscopic incisions. After aortic dissection, an 8-mm graft was passed through a retroperitoneal tunnel. Rumel tourniquets were used for aortic occlusion after placement of a shunt. End-to-side endoscopic anastomosis was completed with knots tied extracorporeally. The left femoral anastomosis was completed under direct vision. Duplex ultrasound of the graft was done on postoperative days 1, 3, and 7. Thoracoscopic TAFB was completed in all animals. Mean aortic anastomosis time was 57 min (range, 34-145); and mean cross-clamp time, 74 min (range, 53-155). Mean operative time was 310 min; the first six operations lasted longer than the last five (338 min vs 276 min, P < 0.04). Average blood loss was 611 ml (range, 250-1300). Two animals died due to anesthetic complications. One (11%) of the nine surviving pigs died on day 2 due to bleeding. Complications were paraplegia in one (11%) and graft thrombosis in another (11%). Videoendoscopic TAFB can be completed in pigs with acceptable short-term patency and survival. Further experience in thoracoscopic techniques can make TAFB a feasible and low-risk option for selected patients with aortoiliac occlusive disease.

Apnea-induced hemoglobin desaturation during one-lungvs two-lung ventilation

To compare the rate of apnea-induced hemoglobin desaturation during one-lung ventilation (OLV) vs. two-lung ventilation (TLV) in patients undergoing thoracic surgery. Six patients undergoing thoracotomy or thoracoscopy were included. Each patient served as his/her own control. The lungs were ventilated with oxygen 100% using TLV, followed after 20-30 min by OLV and the resultant PaO2 was measured. Apnea was then induced following the two techniques of ventilation, and the times for every 1% decrease in hemoglobin saturation from 100% to 95%, as monitored by pulse oximetry, were recorded. The times for every 1% decrease in the saturation were compared in the two groups. The mean PaO2 value following TLV (445+/-99 mm Hg) was higher than the mean PaO2 following OLV (156+/-18 mm Hg). Also, the mean time for subsequent apnea induced hemoglobin desaturation from SpO2 100% to 95% following TLV was twice the time of desaturation following OLV (6.3+/-1.2 min vs. 3.2+/-0.5 min, P<0.05). Hemoglobin desaturation occurs more rapidly during apnea following OLV than TLV. The rapid desaturation may be attributed to the decrease of FRC, associated with an increased transpulmonary shunting. The results suggest that two-lung ventilation with oxygen 100% provides a greater safety margin than one-lung ventilation with oxygen 100% whenever ventilation is interrupted.

Pulmonary air trapping during two-lung and one-lung ventilation

Objective: Evaluation of the magnitude of pulmonary air trapping during routine thoracic surgery and single-lung transplantation. Design: Prospective study on consecutive patients. Setting: Single institution, university hospital. Participants: Sixteen patients with no or moderate obstructive lung disease undergoing routine thoracic surgery (group 1), six patients with severe emphysema (group 2), and six patients with severe fibrosis (group 3) undergoing single-lung transplantation. Interventions: Occlusion maneuver timed at the end of expiration to measure auto-positive end-expiratory pressure (auto-PEEP) and trapped volume ( Δ FRC). The maneuver was performed during two-lung ventilation in supine (2LV supine) and lateral decubitus (2LV lateral) positions and during one-lung ventilation (OLV) in lateral decubitus position. At the same time, airway pressures and PaO 2 measurements were performed. Measurements and Main Results: In group 1, consistent values of auto-PEEP and Δ FRC occurred only during OLV: 4.8 ± 2.5 cm H 2O and 109 ± 61 mL (mean ± standard deviation). In group 2, auto-PEEP and Δ FRC values were 11.7 ± 6.9 cm H 2O and 355 ± 125 mL during 2LV supine, 8.8 ± 5.7 cm H 2O and 320 ± 122 mL during 2LV lateral, and 15.9 ± 3.9 cm H 2O and 284 ± 45 mL during OLV. In group 3, pulmonary air trapping was low. For the three groups together, auto-PEEP and Δ FRC ( p < 0.0001) related inversely to the ratio of forced expired volume in 1 second (FEV 1) to forced vital capacity (FVC) expressed in percent (FEV 1/FVC%) during OLV. In contrast, there was no correlation between PaO 2 and auto-PEEP or Δ FRC. Conclusion: Pulmonary air trapping must be suspected in patients with no or moderate obstructive lung disease during OLV and in those with severe obstructive disease as soon as 2LV is initiated.

The Effect of Two-Lung Ventilation Time on PaO2 during the Sequential One-Lung Ventilation

The Effect of Two-Lung Ventilation Time on PaO2 during the Sequential One-Lung Ventilation

Damaged Univent[registered sign] Tubes

Univent[registered sign] endotracheal tube (Fuji Systems, Tokyo, Japan) damage is rare, but we have encountered two such cases: a fragmented tube and a fractured tube. Case Reports Case 1 The patient was a 62-yr-old, 158-cm, 58-kg man scheduled for surgery with a diagnosis of esophageal cancer. After placement of a 8.5-mm single-lumen cuffed Univent[registered sign] tube made of silicon, the built-in cuff was advanced into the right mainstem bronchus with the aid of fiberoptic bronchoscopy. The bronchial blocker cuff was inflated to permit one-lung ventilation that was confirmed by auscultation of the lungs. The patient was in a left semilateral decubitus position, and the operating Table wasrotated to the left according to the surgical procedure. During two-lung ventilation, analysis of arterial blood gases was normal, and pulse oximetry showed 99%-100% oxygen saturation. However, during one-lung ventilation, oxygen saturation decreased to 93%, and PaO2 gradually decreased from 130 to 52 mm Hg despite the inhalation of 100% oxygen. One-lung ventilation time was 90 min in total, and during this period, both lungs were ventilated manually a few times until oxygen saturation recovered to 100%. Surgery was completed in 6 h 20 min; the anesthesia time was 7 h 40 min. The patient entered the intensive care unit with the Univent[registered sign] endotracheal tube still in place. When the trachea was suctioned, using a fiberoptic bronchoscope, we found a foreign body at the proximal region of the left anterior segmental bronchus, and the object was removed. As it seemed to be a silicon fragment, the Univent[registered sign] endotracheal tube was replaced with a single-lumen tube, and we inspected the Univent[registered sign] tube carefully. The inner part where a slip joint (a tracheal tube connector) attached to the tube was broken, and the object that was removed from the patient's bronchus fit perfectly into the defective area (Figure 1). Neither atelectasis nor the foreign object was seen on chest radiograph taken immediately after the patient entered the intensive care unit.Figure 1: A fragmented Univent[registered sign] tube and a silicon tip that was removed from the patient's bronchus. The size of the fragment is approximately 9 x 3 mm. The outer diameter of the slip joint (the tracheal tube connector) shown on the right is apparently larger than the inner diameter of the tube.Case 2 The patient was a 57-yr-old, 160-cm, 56-kg man undergoing surgery for esophageal cancer. A 9.0-mm Univent[registered sign] tracheal tube was used. During surgery, the slip joint disconnected from the Univent[registered sign] tube several times and had to be reconnected. After extubation, we checked the Univent[registered sign] tube for fracture and noticed that the inside of the tube was damaged (Figure 2).Figure 2: The orifice of the Univent[registered sign] tube is fractured at the same place as in the first case.Discussion Before intubation, the tube and the slip joint must be joined together because the Univent[registered sign] tube itself and its connector, the slip joint, are packed separately. It seems to be easier to detach the slip joint from the Univent[registered sign] tube after inserting it into the tube if a fiberoptic bronchoscope with a large diameter is used to verify adequate placement of the tube. The inner diameter of the tube is smaller than the outer diameter of the slip joint by 1 mm (Figure 1). Consequently, if a tube and a slip joint are attached improperly, they can easily disconnect. However, so much force is needed to connect them properly that it may cause a fracture in the inner layer of the tube. The silastic Univent[registered sign] tubes are more elastic and fragile than conventional tubes made of polyvinyl chloride. In the first case, we assume that a silicon fragment chipped away from the tube on connection and traveled into the patient's bronchus [1] when we were performing fiberoptic bronchoscopy or when the airway was suctioned. Fortunately, the silicon tip fragment did not cause a serious complication, such as airway obstruction [2,3] or atelectasis. In the second case, the tube was fractured at the same place as in the first case, and this was not noticed until tracheal extubation. Our experiences illustrate that the tracheal tube connector can damage the Univent[registered sign] tube. The two parts should be connected cautiously.

Interrupted Expiratory Flow on Automatically Constructed Flow-Volume Curves May Determine the Presence of Intrinsic Positive End-Expiratory Pressure During One-Lung Ventilation

We studied patients undergoing elective pulmonary surgery to establish whether observing interrupted expiratory flow (IEF) on the flow-volume curves constructed by the Ultima SV respiratory monitor is a reliable way to identify patients with dynamic pulmonary hyperinflation and intrinsic positive end-expiratory pressure (PEEP (i)). Patients' tracheas were intubated with a double-lumen endotracheal tube and ventilated with a Siemens 900C constant flow ventilator. In 30 patients, PEEPi was determined by the end-expiratory occlusion (EEO) method during the periods of two-lung and one-lung ventilation in the lateral position. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of the IEF method were calculated. From the 122 measurement pairs, PEEPi was identified with the EEO method in 65 occasions. The mean level of PEEPi was 4.4 cm H2 O. During one-lung ventilation, the level of PEEPi and the number of true-positive findings was significantly higher (PEEPi = 4.7 cm H2 O and 32 episodes) than during two-lung ventilation (2.9 cm H2 O and 19 episodes). When the level of PEEPi was higher than 5 cm H2 O, the predictive value of IEF was 100%. The overall sensitivity of the IEF method was 0.78, its specificity was 0.91, and its predictive value was 0.92. In conclusion, examination of the flow-volume curves displayed on the respiratory monitor may identify patients with dynamic hyperinflation and PEEP (i) during anesthesia for thoracic surgery. Implications: To identify patients with intrinsic positive end-expiratory pressure during anesthesia without the need to interrupt mechanical ventilation, the flow-volume curves of an online respiratory monitor may be examined. The presence of an interrupted expiratory flow may suggest the presence of intrinsic positive end-expiratory pressure with a reasonable accuracy. (Anesth Analg 1998;86:880-4)