Laszlo L Szegedi

Two-lung and One-lung Ventilation in Patients with Chronic Obstructive Pulmonary Disease: The Effects of Position and Fio2

We compared the effects of position and fraction of inspired oxygen (FIO2) on oxygenation during thoracic surgery in 24 consenting patients randomly assigned to receive an FIO2 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.

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. (Anesth Analg 1997;84:1034-7)

The effects of acute isovolemic hemodilution on oxygenation during one-lung ventilation

Data on the effects of isovolemic hemodilution (IH) on oxygenation during one-lung ventilation (OLV) are lacking. We studied 47 patients with hemoglobin >14 g/dL who were scheduled for lung surgery (17 with normal lung function [group NL], 17 with chronic obstructive pulmonary disease [COPD] [group COPD], and 13 with COPD as control for time/anesthesia effects [group CTRL]). Anesthesia was standardized. The tracheas were intubated with a double-lumen tube. Ventilatory settings and fraction of inspired oxygen remained constant. The study was performed with patients in the supine position before surgery. OLV was initiated for 15 min. Two-lung ventilation was reinstituted, and IH was performed (500 mL); an identical volume of hydroxyethyl starch was administered. Subsequently, OLV was again performed for 15 min. In group CTRL, the same sequences of OLV were performed without IH. At the end of each period of OLV, pulmonary mechanics and blood gases were recorded. Data were analyzed by analysis of variance (mean ± sd). In group NL and group CTRL, the arterial oxygen partial pressure remained constant, whereas it decreased in group COPD from 119 ± 21 mm Hg before IH to 86 ± 16 mm Hg after IH (P < 0.01). Mild IH impairs gas exchange during OLV in COPD patients, but not in patients with normal lung function.

Gravity is an important determinant of oxygenation during one‐lung ventilation

Background: The role of gravity in the redistribution of pulmonary blood flow during one‐lung ventilation (OLV) has been questioned recently. To address this controversial but clinically important issue, we used an experimental approach that allowed us to differentiate the effects of gravity from the effects of hypoxic pulmonary vasoconstriction (HPV) on arterial oxygenation during OLV in patients scheduled for thoracic surgery.

One-lung ventilation does not result in cerebral desaturation during application of lung protective strategy if normocapnia is maintained

BACKGROUND Previously a report has suggested that administration of lung protective strategy for one-lung ventilation(OLV) results in oxygen desaturation of the brain parenchyma. The aim of our work was to confirm that the maintenance of normocapnia during protective OLV strategy results in alteration of cerebral blood fl ow and cerebral oxygen saturation as compared to double-lung ventilation. METHODS Data were obtained from 24 patients undergoing thoracic surgery. Cerebral oxygen saturation (rSO2) was continuously monitored by INVOS 5100C Cerebral Oxymeter System along with measurement of cerebral blood fl ow velocity (MCAV) by transcranial Doppler sonography. Arterial blood samples were taken for blood gas analysis in the awake state, in the supine and lateral decubitus position during double-lung ventilation (DLV), and during OLV. RESULTS When ventilation was changed from DLV to OLV, no significant change was observed in rSO2. A significant decrease of rSO2 was found compared to the value observed during DLV in lateral decubitus at the time point 60 minutes after the start of OLV. No clinically significant changes in the MCAV was observed throughout the course of the thoracic surgical procedure. CONCLUSIONS OLV does not result in clinically relevant decreases in cerebral blood fl ow and cerebral oxygen saturation during application of lung protective ventilation if normocapnia is maintained.