Two-lung Ventilation Research Articles

Delayed Bronchial Stenosis After Blunt Chest Trauma

Delayed Bronchial Stenosis After Blunt Chest Trauma

Continuous monitoring of ventilatory mechanics during one-lung ventilation.

The Ultima SV respiratory monitor can be used to monitor the intraoperative effects of the lateral decubitus position and one-lung ventilation on ventilatory mechanics. Eight patients with esophageal cancer who required one-lung ventilation for esophagectomy and reconstruction were enrolled in the study. We monitored pressure-volume or flow-rate-volume loops continuously throughout the operation. Respiratory parameters were evaluated closely during five conditions of ventilation: two-lung ventilation in the supine position, two-lung ventilation in the lateral decubitus position, dependent one-lung ventilation in the lateral decubitus position, nondependent one-lung ventilation in the lateral decubitus position, and dependent one-lung ventilation in the lateral decubitus position with the chest opened. Respiratory rate was controlled at 10 breaths/min, and tidal volume was kept constant (10 ml/kg) during surgery. Peak inspiratory pressure increased to 29.0 +/- 9.0 (mean +/- SD) cm H2O in the dependent one-lung in the lateral decubitus position with the chest opened (p < 0.01). Dynamic compliance decreased to 29.4 +/- 4.9 ml/cm H2O in the dependent one-lung in the lateral decubitus position with the chest opened (p < 0.01). The changing configuration of the loops also offered additional and instantaneous information during one-lung ventilation. One-lung ventilation caused several changes in the whole respiratory system (lung, thorax, and endotracheal tube). Continuous monitoring of flow-rate-volume or pressure-volume loops with in-line spirometry provided comprehensive information regarding parameters in one-lung ventilation.

Video-Assisted Thoracoscopic Surgery for the Treatment of Congenital Cardiac Defects in the Pediatric Population

Recent technologic advances have contributed to a renewed interest in thoracoscopic surgery.In our institution, thoracoscopy through video-assisted technology has been successfully applied to congenital heart surgery. We reviewed the charts of 45 consecutive patients (ASA physical status II-IV) who underwent video-assisted thoracoscopic surgery (VATS) for various congenital heart defects. The mean age of the patients was 2.65 yr and the mean weight was 11.78 kg. The surgical procedures included patent ductus arteriosus interruption (n = 28) and vascular ring division (n = 8), and 9 patients had miscellaneous procedures. The most commonly used anesthetic regimen consisted of isoflurane, pancuronium, fentanyl, air, and oxygen. Seven patients were managed with one-lung ventilation, the remainder by two-lung ventilation with surgical lung retraction. Intraoperative desaturation occurred in 12 patients (26.7%) but resolved quickly with brief reexpansion of the lungs. Postoperative complications included: pleural effusions (n = 3), chylothorax (n = 2), right upper lobe atelectasis (n = 1), small pneumothorax (n = 1), and vocal cord paralysis (n = 1). Seven patients (15.5%) required conversion to a thoracotomy for insufficient exposure (n = 4) or due to concern over bleeding (n = 3). This experience with VATS in pediatric patients with congenital heart disease may provide a database for comparison with others who work with the VATS technique. (Anesth Analg 1996;82:563-67)

Video-Assisted Thoracoscopic Surgery for the Treatment of Congenital Cardiac Defects in the Pediatric Population

Recent technologic advances have contributed to a renewed interest in thoracoscopic surgery. In our institution, thoracoscopy through video-assisted technology has been successfully applied to congenital heart surgery. We reviewed the charts of 45 consecutive patients (ASA physical status 11-IV) who underwent video-assisted thoracoscopic surgery (VATS) for various congenital heart defects. The mean age of the patients was 2.65 yr and the mean weight was 11.78 kg. The surgical procedures included patent ductus arteriosus interruption (n = 28) and vascular ring division (n = 8), and 9 patients had miscellaneous procedures. The most commonly used anesthetic regimen consisted of isoflurane, pancuronium, fentanyl, air, and oxygen. Seven patients were managed with one-lung ventilation, the remainder by two-lung ventilation with surgical lung retraction. Intraoperative desaturation occurred in 12 patients (26.7%) but resolved quickly with brief reexpansion of the lungs. Postoperative complications included: pleural effusions (n = 3), chylothorax (n = 2), right upper lobe atelectasis (n = 1), small pneumothorax (n = 1), and vocal cord paralysis (n = 1). Seven patients (15.5%) required conversion to a thoracotomy for insufficient exposure (n = 4) or due to concern over bleeding (n = 3). This experience with VATS in pediatric patients with congenital heart disease may provide a database for comparison with others who work with the VATS technique.

Near-sitting position and two-lung ventilation for endoscopic transthoracic sympathectomy

To control for hypoxemia during endoscopic transthoracic sympathectomy, usually by using double-lumen tube and one-lung ventilation, a different anesthetic technique was adopted. A prospective clinical study. A university-affiliated medical center. Twenty-one adult patients (10 male and 11 female) between 15 and 44 years of age (mean, 22 years), ASA (American Society of Anesthesiologists) physical status I and II, participated in the study. Under general anesthesia, a single-lumen endotracheal tube was inserted. The radial artery was cannulated for blood pressure monitoring and blood gas sampling. Patients were gradually raised from a supine position to 60 to 70 degrees from the horizontal plane. Mean fractional inspiratory O2 ratio was 0.4 +/- 0.02 (mixture of O2 and air) throughout the operation. Blood gas samples were taken during two-lung ventilation before surgery, at each one-chest operation, and when switching between the operated chest sides. An artificial pneumothorax was established by insufflation of CO2, the sympathetic chain coagulated, the pneumothorax released, and the lung reinflated. Comparisons were performed using one-way analysis of variance and the Bonferroni post-test. Arterial O2 partial pressure at right- and left-chest operation were 209 +/- 83 and 189 +/- 63 mmHg, respectively, compared with 227 +/- 43 and 241 +/- 69 mmHg on two-lung ventilation before and during surgery, respectively. O2 saturation, arterial CO2 partial pressure, bicarbonate, base excess, peak inspiratory pressure, and hemodynamic parameters (in most patients) did not change throughout the operation. The near-sitting position, a single-lumen tube, and a continuous two-lung ventilation technique is simple and may prevent hypoxemia during endoscopic transthoracic sympathectomy.

Left, but not right, one-lung ventilation causes hypoxemia during endoscopic transthoracic sympathectomy

To describe the respiratory and cardiovascular effects of one-lung ventilation, using a double-lumen tube, during endoscopic transthoracic sympathectomy. A prospective clinical study. A university-affiliated medical center. Nineteen adult patients (10 men, 1 woman) between 16 and 35 years of age, ASA (American Society of Anesthesiologists) physical status I and II, participated in the study. Endoscopic transthoracic sympathectomy was performed under general anesthesia, using a double-lumen endobronchial tube, after induction of artificial pneumothorax plus insufflation of CO2 into the operated chest. Via radial artery cannulae, one to three arterial blood gas samples were taken during two-lung ventilation before surgery, at each one-lung ventilation, in most cases during the period of two-lung ventilation when switching between the operated sides, and after surgery. Comparisons were performed using the Wilcoxon matched-pairs single-ranks test. Left-lung ventilation and right-chest operation caused profound decrease of arterial oxygen partial pressure (PaO2), compared with two-lung ventilation before surgery (70.7%, P > 0.0003) and compared with PaO2 at two-lung ventilation during and after surgery (decrease of 80.1% and 75.3%, respectively; P > 0.001 and < 0.005, respectively). Right-lung ventilation and left-chest operation did not cause hypoxemia. Arterial CO2 partial pressure, pH, and bicarbonate, as well as hemodynamic parameters, did not change from baseline values throughout surgery. Pulse oximetry and repeated blood gas measurements are needed during endoscopic transthoracic sympathectomy in order to detect and treat hypoxemic events, which may jeopardize the patient's life.

Improvement of arterial oxygenation by selective infusion of prostaglandin E1 to ventilated lung during one-lung ventilation.

One-lung anesthesia provides a better surgical field for thoracic procedures but also impairs the arterial oxygenation and venous admixture. During one-lung ventilation, pulmonary vasoconstriction is assumed to be present within both ventilated and collapsed lungs. We propose that arterial oxygenation could be optimized by offsetting the vasoconstriction within the microcirculation of ventilated lung. In an anesthetized dog model, incremental doses of prostaglandin E1 (PGE1) were selectively infused into the main trunk of the pulmonary artery of the ventilated lung after one-lung ventilation for 60 min (PGE1 group, n = 9). Arterial oxygenation and calculated venous admixture (Qs/Qt) was also assessed in a time-course control group (Control group, n = 5). During two-lung ventilation (FIO2: 0.66), arterial PO2 and venous admixture was 44.2 +/- 3.5 kPa and 10.7 +/- 2.3%, respectively. One-lung ventilation (FIO2: 0.66) with left lung collapsed reduced arterial PO2 to 11.6 +/- 1.7 kPa and increased venous admixture to 40.7 +/- 5.8% (P<0.001). Venous O2 tension also decreased from 6.3 +/- 0.7 kPa to 5.0 +/- 0.6 kPa with a slight increase in mean pulmonary artery pressure and pulmonary vascular resistance (P<0.05). During selective infusion of PGE1 at a dose of 0.04 to 0.2 mu g kg-1 min-1, there was a dose-dependent improvement in arterial PO2 with a parallel reduction of venous admixture during one-lung ventilation. Arterial PO2 increased to a maximum of 23.0 +/- 4.3 kPa, and the venous admixture decreased significantly to a minimum of 27.4 +/- 4.2% by PGE1 at a dose of 0.04-0.4 mu g kg-1 min-1 (P<0.01). PGE1 resulted in a small increase in cardiac output and decreases of pulmonary pressure and pulmonary vascular resistance at a relatively high dose of 0.4 mu g kg-1 min-1 during selective infusion (P<0.05). These results suggest that a selective pulmonary artery infusion of PGE1 to the ventilated lung within the dose range of 0.04-0.4 mu g kg-1 min-1 is practical and effective to improve arterial oxygenation and reduce venous admixture during one-lung ventilation.

Continuous Intra-arterial Blood Gas Monitoring in Patients Undergoing Suprarenal Aortic Surgery

The authors used an on-line, real-time, continuous blood gas monitor in 5 patients undergoing elective suprarenal aortic reconstruction. They retrospectively analyzed data to evaluate its utility in acid-base management and in detection of dynamic changes in oxygenation. Seven sets of data were analyzed since 1 patient underwent two additional periods of aortic crossclamping. A similar group of 7 patients undergoing elective suprarenal aortic surgery without continuous blood gas monitoring was analyzed and served as a control group. There was a highly significant mean decrease in partial pressure of oxygen (P02) of 158 mm Hg (P = 0.0060) with unclamping. In 1 patient the P02 dropped from 218 to 63 mm Hg within sixty seconds of unclamping, and this required immediate reinstitution of two-lung ventilation. Continuous availability of pH permitted accurate therapy with bicarbonate infusion during clamping. As a result there was no significant change in pH between preclamp and immediately after unclamping (P = 0.97). In the control group the pH decreased from a mean of 7.38 to a mean of 7.24 (P = 0.0005) between preclamp and after unclamping. In summary, dynamic changes in oxygenation and pH are observed during suprarenal aortic surgery. Continuous blood gas monitoring provided data resulting in improved management of acid-base status and early detection of significant decreases in oxygenation.

Anesthetic techniques for pediatric thoracoscopy

Since 1981, we have performed 68 thoracoscopic procedures in 62 patients aged 7 months to 21 years. We reviewed the anesthetic and ventilation strategy used for each procedure to determine which anesthetic strategies are safe and effective for particular children and conditions. Regional anesthesia with sedation was used for six procedures in 5 patients with a mean age of 16 years (range, 9 to 21 years). One patient required conversion to general anesthesia. General anesthesia with one-lung ventilation was attempted for 18 procedures in 17 patients with a mean age of 12 years (range, 7 months to 18 years). Two patients required conversion to two-lung anesthesia secondary to pulmonary intolerance. One of these patients and 2 others required thoracotomy. General anesthesia with two-lung ventilation was used for 44 procedures in 41 patients with a mean age of 9 years (range, 1 to 17 years). There were no anesthesia-related difficulties. Regional anesthesia should be limited to the older, more cooperative patient. General anesthesia with one-lung ventilation is useful in adolescents, as they tolerate collapse of one lung well, and it is particularly desirable for procedures requiring exposure of the mediastinum and for talc pleurodesis. General anesthesia with two-lung ventilation can be used in any age group but is generally necessary for infants and small children, as they often will not tolerate the collapse of one lung, and in the larger child or adolescent with severe pulmonary compromise.

Effects of isoflurane on regional pulmonary blood flow during one-lung ventilation

Isoflurane has been reported to inhibit hypoxic pulmonary vasoconstriction. However, the effects of one-lung ventilation and isoflurane on regional pulmonary blood flow (Qr) have not been investigated in detail. Therefore, using radionuclide labelled microspheres we measured Qr in rabbits (n = 8) in the left lateral decubitus position during two- and one-lung ventilation under i.v. baseline anaesthesia and during additional administration of 1.5% isoflurane. Macrohaemodynamic variables were recorded continuously. Isoflurane increased non-dependent lung blood flow during two-lung ventilation. One-lung ventilation caused a homogeneous decrease in Qr throughout the hypoxic lung, irrespective of isoflurane administration (P < 0.001). However, isoflurane significantly augmented Qr of the hypoxic lung during one-lung ventilation (P < 0.05). During all phases, Qr of the upper lobe was higher compared with that in the lower lobe in isogravitational slices of both lungs; a ventrodorsal perfusion gradient was found in the left upper lobe. We conclude that 1.5% isoflurane increased perfusion of the non-dependent lung, inhibited hypoxic pulmonary vasoconstriction-induced redistribution of pulmonary blood flow and did not influence isogravitational perfusion gradients.

Isoflurane Inhibits Hypoxic Pulmonary Vasoconstriction

Contradictory results have been reported in previous studies investigating the effect of isoflurane on hypoxic pulmonary vasoconstriction by indirect approaches. The current study measured the effects of one-lung ventilation (1LV) and isoflurane 1.5% by direct visual observation of the pulmonary microcirculation. Ten New Zealand White rabbits were anesthetized with intravenous thiopental, alpha-chloralose, and piritramid. Arterial, central venous, pulmonary arterial, left atrial, and airway pressures and cardiac output were recorded continuously. 1LV was facilitated by a bronchial blocker in the right main bronchus. A transparent window was implanted into the right thoracic wall for videofluorescence microscopy of the subpleural pulmonary microcirculation. After intravenous injection of fluorescein isothiocyanate-labeled red blood cells, vessel diameters, red blood cell flux, red blood cell velocity, and dynamic microhematocrit were measured in pulmonary arterioles and venules during two-lung ventilation and 1LV during baseline anesthesia and with supplementary isoflurane 1.5%. During intravenous anesthesia, 1LV caused significant reduction of vessel diameters and red cell flux and velocity and an increase in microvascular hematocrit in pulmonary arterioles and venules. The decreases in arteriolar diameters and red blood cell flux and velocity induced by 1LV were significantly attenuated by isoflurane as compared with those measured during baseline anesthesia (P = 0.010, P = 0.029 and P = 0.047). Accordingly, 1LV-induced reduction of venular red cell flux (P = 0.023) and velocity (P = 0.036) were less pronounced during isoflurane. Isoflurane caused a significant decrease in arterial pressure. Venous admixture increased and arterial oxygen tension decreased significantly during 1LV; the changes were more pronounced during 1LV with isoflurane 1.5% than during 1LV with baseline anesthesia. 1LV leads to a marked reduction of microvascular diameters and blood flow in the hypoxic lung. Isoflurane 1.5% inhibits hypoxic pulmonary vasoconstriction in pulmonary arterioles and increases regional blood flow in the hypoxic lung.

One-lung or two-lung ventilation during transthoracic oesophagectomy?

The purpose of this study was to determine the safety of one-lung ventilation (OLV) during transthoracic oesophagectomy. Changes in circulatory and respiratory variables during and after operation were compared in patients receiving OLV or conventional two-lung ventilation (TLV). Thirty patients undergoing transthoracic oesophagectomy were randomly divided into either the OLV or the TLV group. During thoracotomy, FIO2 was kept to 1.0. The PaO2 in the OLV group decreased from the prethoracotomy value of 467 +/- 84 mmHg to 227 +/- 162 mmHg during OLV. This decrease was greater than the decrease from 484 +/- 79 mmHg to 380 +/- 119 mmHg in the TLV group (P < 0.05). The shunt ratio increased in the OLV group from 20 +/- 7% to 35 +/- 13% during OLV which was greater than the increase in the TLV group (26 +/- 7% from 17 +/- 8%) (P < 0.05). Other variables and the incidence of the complications, however, were little different between the two groups during and after OLV and up to POD 3. It is concluded that OLV is as safe as TLV during oesophagectomy.

High-frequency jet ventilation vs continuous positive airway pressure for differential lung ventilation in patients undergoing resection of thoracoabdominal aortic aneurysm

Twenty patients, scheduled for surgical resection of thoracoabdominal aortic aneurysm were divided into two groups according to the type of differential lung ventilation used during graft replacement of the descending thoracic aorta. In the high-frequency jet ventilation (HFJV) group of ten patients, HFJV was applied to the left lung once collapsed and retracted by the surgeon, the patient lying in the right lateral decubitus and being intubated by a Carlens' tube. In the continuous positive airway pressure (CPAP) group of ten patients, CPAP was applied to the left lung at the same mean airway pressure as HFJV (1 kPa). Before anaesthetic induction, an arterial and a Swan-Ganz catheter were inserted for cardiovascular monitoring. The same anaesthetic technique using fentanyl 6 micrograms.kg-1, flunitrazepam 0.02 mg.kg-1 and pancuronium 0.1 mg.kg-1 was used for each patient. Haemodynamic and respiratory measurements were made; 15 min after positioning the patients in the right lateral decubitus using two-lung ventilation; 15 min after collapse and retraction of the left lung using one-lung ventilation and 15 min after using differential lung ventilation with CPAP or HFJV. Left lung collapse with conventional one-lung ventilation induced a dramatic decrease in arterial oxygenation: PaO2/FIO2 ratio decreased from 43 +/- 6 kPa to 20 +/- 8 kPa, alveolo-arterial oxygen difference increased from 24 +/- 7 kPa to 72 +/- 11 kPa and pulmonary shunt increased from 17 +/- 2% to 37 +/- 3%. Whereas differential lung ventilation with CPAP did not improve any of the respiratory parameters measured, differential lung ventilation with HFJV, significantly increased PaO2/FIO2 ratio to 41 +/- 14 kPa.(ABSTRACT TRUNCATED AT 250 WORDS)

Variation in the arterial to end-tidal Pco2 difference during one-lung thoracic anaesthesia

We have measured the arterial to end-tidal PCO2 difference (PaCO2-PE'CO2) in 22 patients undergoing pulmonary resection in the lateral thoracotomy position during two-lung ventilation (TLV) and after transition to one-lung ventilation (OLV). With OLV for each patient, the practice of correcting the estimate by an initial measurement of (PaCO2-PE'CO2) was evaluated by subtracting the initial (PaCO2-PE'CO2) from subsequent values measured at 10-min intervals. Net (uncorrected) and corrected differences during OLV were analysed using ANOVA. (PaCO2-PE'CO2) values during TLV and OLV were similar: mean (SD) 1.3 (0.6) kPa and 1.2 (0.7) kPa, respectively (ns). Mean (PaCO2-PE'CO2) varied in the range 0.2-2.5 kPa, while maximum (PaCO2-PE'CO2) was 0.3-2.8 kPa. The mean (SD) of 133 pairs of measurements with OLV was 1.1 (0.7) kPa. Even after correction, mean (PaCO2-PE'CO2) varied in the range -0.7 to 0.8 kPa; individual extreme values were from -1.3 to 1.7 kPa. Variation between patients was found to be greater than variation within patients for both net and corrected differences (F ratio = 37.0 and 10.9, respectively), although calculating a corrected difference did reduce variation between patients from a mean square value of 2.44 to 0.61. The wide variation in (PaCO2-PE'CO2) suggests that the accuracy of estimation of PaCO2 by monitoring PE'CO2, although improved by the use of a corrected difference, remains questionable during OLV.

Is hypoxic pulmonary vasoconstriction important during single lung ventilation in the lateral decubitus position?

Hypoxic pulmonary vasoconstriction (HPV) has not been demonstrated in human single lung anaesthesia in the lateral decubitus position (LDP). The purpose of this study was to determine whether (1) HPV occurs in the non-dependent, non-ventilated lung, and (2) if the infusion of sodium nitroprusside (SNP) inhibits HPV. During intravenous anaesthesia the tracheas of seven patients were intubated with double lumen endotracheal tubes. Standard monitors plus radial and pulmonary arterial catheters were placed. Patients were positioned in the LDP and haemodynamic and gas exchange data were recorded for each of three stages; I: two-lung ventilation, II: single, dependent lung ventilation (1 LV) and III: 1LV with infusion of SNP. In stage II the PaO2 decreased from 531 +/- 42 mmHg to 285 +/- 42 mmHg (P < 0.05) and Qs/Qt increased from 12.3 +/- 2.7 to 29.0 +/- 6.3% (P < 0.05). With SNP infusion there was a 30% increase in cardiac index (CI) (P < 0.05). The SNP infusion was not associated with changes in Qs/Qt or PaO2. This model demonstrates changes in Qs/Qt and PaO2 associated with single-lung ventilation in ASA I and II patients in the LDP but we were unable to demonstrate inhibition of HPV by SNP.

On-line expiratory flow-volume curves during thoracic surgery: occurrence of auto-PEEP

Flow-volume loops were monitored continuously in 39 patients undergoing thoracic surgery requiring one-lung ventilation. In 26 of the 39 patients (67%), auto-positive end-expiratory pressure (auto-PEEP) was seen on the flow-volume curves during both two-lung and one-lung ventilation. Eighty-seven percent of the patients whose trachea was intubated with a smaller size (35- and 37-French gauge) double-lumen tracheal tube exhibited auto-PEEP, compared with patients in whom the tube used was larger (39- or 41-French gauge: 54% and 50%, respectively). Before operation, mean airway resistance was significantly greater in patients who exhibited auto-PEEP during anaesthesia (2.4 cm H2O litre-1 s) than in patients without auto-PEEP (1.7 cm H2O litre-1 s).

Sevoflurane anaesthesia for one-lung ventilation with PEEP to the dependent lung in sheep: effects on right ventricular function and oxygenation.

This study was undertaken to examine the effect of sevoflurane on right ventricular function, the safety of sevoflurane for one-lung ventilation and the effects of PEEP (positive end-expiratory pressure) to the dependent lung in this model using 12 open-chest sheep. Haemodynamic variables, including cardiac output, mean arterial blood pressure, right ventricular pressure and pulmonary arterial pressure, and right ventricular segment shortening (sonomicrometry) were measured. First, animals received 2.0, 3.0 or 4.0% sevoflurane for 20 min each, respectively, during two-lung ventilation to measure the dose-dependent haemodynamic effects of sevoflurane. Then one-lung ventilation was performed with a randomized sequence of 0 (ZEEP), 5 and 10 cm H2O PEEP to the dependent lung under 2.0% sevoflurane anaesthesia after one-hour stabilization. A decrease in systolic segment shortening along with increases in both the end-diastolic and end-systolic lengths of the right ventricle were observed at 3.0 and 4.0% sevoflurane, while global right ventricular function remained substantially unchanged during two-lung ventilation. During one-lung ventilation the PaO2 was greater with 5 cm H2O PEEP 198 mmHg (+/- 25 SEM) than with ZEEP 138 mmHg (+/- 22) or with 10 cm H2O PEEP 153 mmHg (+/- 23) (P < 0.05). No differences in haemodynamic variables or segment shortening between ZEEP and PEEPs during one-lung ventilation were observed. We conclude that although sevoflurane causes a dose-dependent depression of right ventricular function, sevoflurane anaesthesia can be safely applied to one-lung ventilation, and that 5 cm H2O PEEP to the dependent lung can improve arterial oxygenation without causing changes in right ventricular function.

Anesthesia for thoracoscopic laser ablation of bullous emphysema.

We describe the anesthetic management for a new surgical procedure: laser ablation of emphysematous bullae via thoracoscope. Although thoracoscopy is not new, this is the first description of a series of patients with bilateral, chronic lung disease who underwent long periods of one-lung ventilation (OLV) during thoracoscopic therapy. Twenty-six laser ablation procedures were performed in 22 patients. The patients were elderly (mean age 63 yr) with a large incidence of coexisting cardiovascular disease. Most required chronic home oxygen therapy. Patients were monitored invasively, and hemodynamic data were recorded every 5 min. Arterial blood gas analyses were performed every 15 min. Comparisons were made between three intraoperative periods: two-lung ventilation (TLV) before thoracoscopy, OLV during thoracoscopy, and TLV after thoracoscopy. All patients survived the operation despite a mean OLV duration of 170 min, but several experienced serious intraoperative problems, such as hypoxemia or hypotension. Hypoxemia was treated with nondependent lung continuous positive airway pressure and dependent lung positive end-expiratory pressure. In all patients the lungs were adequately ventilated, but bronchopleural fistulae occurred upon return to TLV in every case. The resulting air leaks, often 50% of inspired tidal volume, required the use of a pressure-cycled ventilator to maintain oxygenation. Postoperative air leaks greater than 50% of inspired tidal volume usually required subsequent surgical correction, while smaller leaks resolved spontaneously. Mechanical ventilation was required for an average of 5 days. Eighty-four percent have survived at least 6 months, and nearly all survivors report symptomatic improvement. Ablation of bullae appears to provide symptomatic improvement, and thoracoscopy might be better tolerated than thoracotomy, especially in patients with severe bullous emphysema.

Predicting arterial oxygenation during one-lung anaesthesia.

Eighty patients undergoing elective thoracotomy were studied to assess the possibility of predicting arterial oxygenation (PaO2) during one-lung anaesthesia (OLA). The first 50 patients were studied retrospectively. The method of multiple linear regression was used to construct a predictive equation for PaO2 during OLA. Potential predictors of PaO2 during OLA which were considered were: age, side of operation, preoperative pulmonary flow rates, preoperative and intraoperative PaO2 during two-lung ventilation. The three most significant predictors for PaO2 during OLA were: side right of operation (P < 0.05), preoperative FEV1% (P < 0.01) and intraoperative PaO2 during two-lung ventilation (P = 0.0001). The predictive equation for PaO2 after ten minutes of OLA was: PaO2 = 100 - 72 (side) - 1.86 (FEV1%) + 0.75 (two-lung) PaO2; (for side insert 0 for left-sided thoracotomy and 1 for right-sided thoracotomy). The remaining 30 patients were studied prospectively and the predicted PaO2 correlated with the observed PaO2 after ten minutes of OLA (r = 0.73, P < 0.01). Four of 30 patients had a predicted PaO2 at ten minutes of OLA < 150 mmHg. Of these, 2/4 subsequently required abandonment of OLA for pulse oximetric saturation < 85%. We conclude that although it is not possible to predict an individual patient's PaO2 during OLA with a high degree of accuracy, it is possible, before the initiation of OLA, to identify those patients whose arterial oxygenation is likely to decrease to low levels during OLA.

An experimental model for simultaneous quantitative analysis of pulmonary micro- and macrocirculation during unilateral hypoxia in vivo.

An experimental model was developed for quantitative analysis of pulmonary microcirculation using in vivo fluorescence videomicroscopy during unilateral hypoxia induced by one-lung ventilation (1 LV). In five white New Zealand rabbits, pulmonary arterioles on the surface of the right lung were visualized by means of intra-arterial injection of FITC-labeled erythrocytes and FITC-Dextran. During 1 LV of the left lung, the mean airway pressure in the right lung was kept at the level of two-lung ventilation (2 LV) by means of N2-CPAP. Arteriolar diameters as well as parameters of macrocirculation (AP, CVP, PAP, LAP, CO) and gas exchange (paO2, Qs/Qt) were measured simultaneously during 2 LV and 1 LV. FiO2 was kept constant at 1.0 during both experimental phases. Macrohemodynamic parameters during 1 LV did not differ from those measured during 2 LV. 1 LV induced a significant decrease in paO2 (213 +/- 105 versus 427 +/- 22 mm Hg, P < 0.05) and a significant increase in Qs/Qt (22 +/- 7 versus 13 +/- 2%, P < 0.05). During 2 LV (baseline), the pulmonary arteriolar diameters ranged from 15-120 microns. 1 LV resulted in a significant decrease of arteriolar diameters to 89.0 +/- 9.3% of baseline (P < 0.05). Relative changes in arteriolar diameters were similar for vessels with baseline diameters of 0-40, 40-60, and 60-120 microns (88.4 +/- 9.9%, 89.6 +/- 9.4%, and 88.4 +/- 8.7%, respectively). The present model is the first one allowing in-vivo investigation of HPV during 1 LV and 2 LV on the basis of simultaneous measurement of pulmonary arteriolar diameters and macrocirculatory parameters in vivo. Although PAP and PVR did not change significantly, a reduction of pulmonary arteriolar diameters was proven in response to alveolar hypoxia during 1 LV. We suggest the model to be useful in studying the physiological effects of HPV on macro- and microcirculation as well as investigating pathophysiological and pharmacological influences on HPV.