Two-lung and one-lung ventilation in patients with chronic obstructive pulmonary disease: the effects of position and F(IO)2.

UNLABELLED: We compared the effects of position and fraction of inspired oxygen (F(IO)2) on oxygenation during thoracic surgery in 24 consenting patients randomly assigned to receive an F(IO)2 of 0.4 (eight patients, Group 0.4), 0.6 (eight patients, Group 0.6), or 1.0 (eight patients, Group 1.0) during the periods of two-lung (TLV) and one-lung ventilation (OLV) in the supine and lateral positions. TLV and OLV were maintained while the patients were first in the supine and then in the lateral position for 15 min each. Thereafter, respiratory mechanical data were obtained, and arterial blood gas samples were drawn. Pao2 decreased during OLV compared with TLV in both the supine and lateral positions. In all three groups, Pao2 was significantly higher during OLV in the lateral than in the supine position: 101 (72-201) vs 63 (57-144) mm Hg in Group 0.4; 268 (162-311) vs 155 (114-235) mm Hg in Group 0.6; and 486 (288-563) vs 301 (216-422) mm Hg in Group 1.0, respectively (P < 0.02, Wilcoxon's signed rank test). We conclude that, compared with the supine position, gravity augments the redistribution of perfusion as a result of hypoxic pulmonary vasoconstriction, when patients are in the lateral position, which explains the higher Pao2 during OLV. IMPLICATIONS: This study compares oxygenation during thoracic surgery during periods of two-lung and one-lung ventilation with patients in the supine and lateral positions when using three different fraction of inspired oxygen values. Arterial oxygen tension was decreased in all three groups during one-lung ventilation in comparison with the two-lung ventilation values, but the decrease was significantly less in the lateral, compared with the supine position.

Respiratory mechanics and gas exchange during one-lung ventilation for thoracic surgery: the effects of end-inspiratory pause in stable COPD patients.

OBJECTIVE: To examine the effects of end-inspiratory pause (EIP) of different durations on pulmonary mechanics and gas exchange during one-lung ventilation (OLV) for thoracic surgery. DESIGN: A prospective clinical study. SETTING: A university hospital. PARTICIPANTS: Eleven patients undergoing elective pulmonary resection with pulmonary hyperinflation on their preoperative pulmonary function studies. INTERVENTIONS: Patients were anesthetized, paralyzed, and intubated with a double-lumen endotracheal tube. Their lungs were ventilated with a Siemens 900C ventilator (Siemens; Solna, Sweden), with constant inspiratory flow. Tidal volume, respiratory rate, and inspiratory time were kept constant during the study. MEASUREMENTS AND RESULTS: During one-lung ventilation in the lateral decubitus position, three levels of EIP (0%, 10%, and 30%) were applied to the dependent lung in random order. After 15 minutes on the given ventilatory pattern, end-inspiratory and end-expiratory occlusions of at least 5 seconds were performed to obtain respiratory mechanics data. Arterial blood gas samples were drawn to assess gas exchange. Altering the duration of end-inspiratory pause from 0% to 30% resulted in a significant increase in intrinsic positive end-expiratory pressure (PEEPi) from 4.1 cm H2O to 7.0 cm H2O. Arterial oxygenation was significantly decreased from 109.7 to 80.5 mmHg and there was a significant negative correlation between the value of partial pressure of arterial oxygen (PaO2) and PEEPi by altering the duration of end-inspiratory pause. From the preoperative pulmonary function studies, the value of functional residual capacity (FRC) (% predicted) showed a significant negative correlation with the PaO2 changes. Partial pressure of arterial carbon dioxide (PaCO2) was not altered significantly by increasing the duration of end-inspiratory pause. CONCLUSION: During the period of OLV in the lateral position of patients with preexisting pulmonary hyperinflation, the magnitude of PEEPi increased and oxygenation decreased significantly, whereas the efficacy of ventilation was not changed by the addition of an end-inspiratory pause to the ventilatory pattern. Because arterial oxygenation is affected by the presence of pulmonary hyperinflation, the method of ventilation should take into account the magnitude of preoperative pulmonary hyperinflation.

Interrupted expiratory flow on automatically constructed flow-volume curves may determine the presence of intrinsic positive end-expiratory pressure during one-lung ventilation.

UNLABELLED: 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 (PEEPi). 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 H2O. During one-lung ventilation, the level of PEEPi and the number of true-positive findings was significantly higher (PEEPi = 4.7 cm H2O and 32 episodes) than during two-lung ventilation (2.9 cm H2O and 19 episodes). When the level of PEEPi was higher than 5 cm H2O, 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 PEEPi 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.

Airway pressure changes during one-lung ventilation.

This investigation analyzed the changes in inspiratory airway pressures during transition from two-lung to one-lung ventilation in patients tracheally intubated with a double-lumen endotracheal tube (DLT) using a classical method of intubation without fiberoptic bronchoscopy. All patients were anesthetized in a standardized fashion. Ventilation was accomplished with the Siemens 900 constant-flow mechanical ventilator (Solna, Sweden). Peak (Ppeak) and plateau (Pplateau) inspiratory airway pressures were recorded with an on-line respiratory monitor before and after clamping the tracheal limb of the DLT. The position of the DLTs was evaluated by fiberoptic bronchoscopy with the patient in supine position. Of the 51 intubations, the DLT was malpositioned in 15 cases (29.5%). Ppeak and Pplateau increased significantly when switched from two-lung ventilation to one-lung ventilation in both correctly and incorrectly positioned DLTs. When the DLT was in a correct position, Ppeak increased by a mean of 55.1% and Pplateau increased by a mean of 41.9%. When the DLT was malpositioned, this increase was significantly larger (74.9% and 68.8%, respectively). Three tests commonly used as markers of malpositioned DLTs were evaluated based on the data of this study, and it was established that, although the pressure differences related to position are statistically significant, as a single value, they cannot be used for clinical decision making.

Intrinsic positive end-expiratory pressure during one-lung ventilation for thoracic surgery. The influence of preoperative pulmonary function.

OBJECTIVE: To detect and to quantify intrinsic positive end-expiratory pressure (PEEPi) during thoracic surgery in the dependent lung of patients intubated with a double-lumen endotracheal tube (DLT) in the lateral position. METHODS: Twenty consecutive patients undergoing elective pulmonary resection were anesthetized, paralyzed, and intubated with a DLT. Their lungs were ventilated (Siemens Servo 900 C ventilator; Siemens Elevna; Solna, Sweden) with constant inspiratory flow. Fraction of inspired oxygen, tidal volume (10 mL/kg), frequency (10/min), and inspiratory time/total time (0.33) were kept constant during the study. PEEPi and ventilatory data were measured in the dependent lung in the supine then in the lateral position with a closed hemithorax. The obtained data were analyzed according to the presence (group PH) or absence (group N) of pulmonary hyperinflation determined from the preoperative pulmonary function data as higher than 120% of predicted value of functional residual capacity (FRC) and residual volume (RV). DATA ANALYSIS: In the dependent lung of patients in group PH (n = 11), PEEPi was present in the supine (n = 8) and in the lateral (n = 11) positions in the range of 1 to 10 cm H2O. In group N (n = 9), PEEPi was detected in one patient and only in the supine position. In the whole group of 20 patients, the preoperative value of FRC (% predicted) and RV (% predicted) was statistically significantly correlated to the presence of PEEPi, whereas the preoperative FEV1 (% predicted) was poorly related to PEEPi in both positions. There was no significant correlation between the value of PaCO2 and PEEPi during one-lung ventilation (OLV) but patients in group PH had a significantly higher PaCO2 during OLV than group N (p = 0.012). CONCLUSIONS: In patients with chronic obstructive lung disease and pulmonary hyperinflation, PEEPi occurs commonly during the period of OLV and only occasionally in patients with normal lungs. As the ventilatory pattern, the size of DLT, and the side of surgery were similar in the two groups of patients, we conclude that the occurrence of PEEPi in our patients was influenced mainly by the preexisting pulmonary hyperinflation and airflow obstruction.

Large tidal volume ventilation does not improve oxygenation in morbidly obese patients during anesthesia.

Eight morbidly obese patients (body mass index [BMI] = 46) were studied during general anesthesia and controlled mechanical ventilation. To evaluate the effect of large tidal volume ventilation on oxygenation and ventilation, the baseline 13 mL/kg tidal volume (VT) (calculated by the ideal body weight) was increased in 3 mL/kg volume increments to 22 mL/kg, while ventilatory rate (RR) and inspiratory time (TI) were kept constant. Each volume increment was maintained for 15 min. Gas exchange was assessed by measuring the arterial blood oxygen tensions, and calculating the indices of alveolar-arterial oxygen tension difference [P(A-a)O2] and arterial/alveolar oxygen tension ratio (a/A). Peak inspiratory airway pressure (Ppeak), end-inspiratory airway pressure (Pplateau), and compliance of the respiratory system (CRS) were recorded using the Capnomac Ultima (Datex, Helsinki, Finland) on-line respiratory monitor. Increasing tidal volumes to 22 mL/kg increased the recorded Ppeak (26.3 +/- 4.1 vs 37.9 +/- 3.2 cm H2O, P < 0.008), Pplateau (21.5 +/- 3.6 vs 27.7 +/- 4.3 cm H2O, P < 0.01), and CRS (39.8 +/- 7.7 vs 48.5 +/- 8.3 mL/cm H2O) significantly without improving arterial oxygen tension and resulted in severe hypocapnia. Since changes in arterial oxygenation were small and not statistically significant, mechanical ventilation of morbidly obese patients with large VTS seems to offer no advantage to smaller (13 mL/kg ideal body weight) VTS.

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).

Continuous spirometry: an aid to monitoring ventilation during operation.

We present six case-reports of patients who experienced inadequate ventilation as a result of endobronchial or oesophageal intubation, or obstruction to the tracheal tube or airway and were monitored with on-line spirometry. The continuously displayed pressure-volume or flow-volume loops may be compared with previously recorded baseline loops. The changing configuration of the curves offers additional and instantaneous information about the cause of increased inspiratory airway pressure, decreased compliance or increased airway resistance. Monitoring flow-volume and pressure-volume loops in conjunction with currently available techniques provides a comprehensive method of monitoring ventilation.

Continuous spirometry for detection of double-lumen endobronchial tube displacement.

Flow-volume and pressure-volume loops were measured with continuous spirometry in 49 patients in whom the trachea was intubated "blindly" with a double-lumen endobronchial tube for thoracic surgery. Nineteen endobronchial tubes were malpositioned by fibreoptic bronchoscopic criteria; 63% of these were suspected because of the configuration of the spirometric loops. During positioning of the patient and during operation, 34.7% of the endobronchial tubes migrated from the initially correct or corrected position. The secondary displacements were identified by abnormal loop configurations and confirmed with fibreoptic bronchoscopy. Continuous spirometric monitoring is helpful in detecting endobronchial tube displacement during intubation and surgery.

Ventilatory effects of pneumoperitoneum monitored with continuous spirometry.

Inspiratory and expiratory tidal volume, peak and plateau airway pressure, compliance of the respiratory system, pressure-volume and flow-volume loops were monitored continuously and recorded in seven women undergoing laparoscopy with carbon dioxide insufflation to an intra-abdominal pressure of 1.6 kPa. All patients were anaesthetised using a total intravenous technique and a constant minute ventilation was maintained. Peak airway and plateau airway pressures increased by 50% and 81% respectively, whilst the compliance of the respiratory system decreased by 47% during the period of increased intra-abdominal pressure. Following release of the pneumoperitoneum, peak and plateau pressures remained elevated by 37% and 27% respectively, and the compliance was 86% of the pre-insufflation value. On-line monitoring of respiratory volumes, pressures and compliance may be helpful during general anaesthesia for laparoscopic procedures to avoid the potential harmful effects of increased airway pressures occurring with increased intra-abdominal pressure.

Continuous noninvasive blood pressure monitoring during thoracic surgery.

To evaluate the usefulness of noninvasive blood pressure monitoring during thoracic surgery, blood pressure measurements obtained with the Finapres 2300 (Ohmeda, Boulder, CO) were compared with an intraarterial catheter system in 10 patients undergoing thoracotomy for lobectomy or pneumonectomy. The Finapres measurements were compared with pressure data obtained ipsilaterally from a radial artery catheter-transducer system. The waveforms were recorded using a strip chart recorder; the systolic (SBP) and diastolic blood pressures (DBP) were measured every 20 seconds on the paper trace. Precision and bias were calculated for SBP and DBP for each patient and for the pooled data, with the invasive blood pressure being considered the gold standard. A total of 1,861 measurement pairs were recorded, 938 pairs during one-lung ventilation. The Finapres underestimated SBP during two-lung ventilation, and overestimated SBP during one-lung ventilation. The precision was good and the biases were small, but there were wide individual variations. It is concluded that the Finapres can be useful in estimating the variability and following the trends of radial arterial blood pressure during thoracic surgery, and is an acceptable alternative to invasive blood pressure monitoring.

Prilocaine-induced methemoglobinemia evidenced by pulse oximetry.

Methemoglobinemia was suspected in a healthy 19-year-old woman, when the pulse oximeter reading (SpO2) was 88% after a plexus brachialis block with 550 mg (35 ml, 1.5%) prilocaine. The patient was receiving 50% oxygen, and the PaO2 was 48.6 kPa (365 mmHg). After start of methylene blue treatment, with a total dose of 1 mg/kg, the SpO2 showed a gradual increase. This case report emphasises the potential advantage of arterial oxygen saturation monitoring with a pulse oximeter, but also the importance of the correct interpretation of the SpO2 reading.

Spinal bupivacain anaesthesia in traumatological surgery.

Two-hundred forty spinal cases of bupivacain anaesthesia are reported. One third of the patients was over 60 years of age and one quarter in a poor condition. No serious or lasting complications were observed. In the overwhelming majority anaesthesia during operation was satisfactory, thus the drug was found suitable for use in traumatological surgery. Due to its protracted effect, bupivacain ensures analgesia in the early postoperative period.