Protective ventilation to reduce inflammatory injury from one lung ventilation in a piglet model

Objectives: To test the hypothesis that protective ventilation strategy (PVS) as defined by the use of low stretch ventilation (tidal volume of 5 ml·kg^?1 and employing 5 cm of positive end expiratory pressure (PEEP) during one lung ventilation (OLV) in piglets would result in reduced injury compared to a control group of piglets who received the conventional ventilation (tidal volume of 10 ml·kg^?1 and no PEEP). Background: PVS has been found to be beneficial in adults to minimize injury from OLV. We designed the current study to test the beneficial effects of PVS in a piglet model of OLV. Methods: Ten piglets each were assigned to either ‘Control’ group (tidal volume of 10 ml·kg^?1 and no PEEP) or ‘PVS’ group (tidal volume of 5 ml·kg^?1 during the OLV phase and PEEP of 5 cm of H₂O throughout the study). Experiment consisted of 30 min of baseline ventilation, 3 h of OLV, and again 30 min of bilateral ventilation. Respiratory parameters and proinflammatory markers were measured as outcome. Results: There was no difference in PaO₂ between groups. PaCO₂ (P < 0.01) and ventilatory rate (P < 0.01) were higher at 1.5 h OLV and at the end point in the PVS group. Peak inflating pressure (PIP) and pulmonary resistance were higher (P < 0.05) in the control group at 1.5 h OLV. tumor necrosis factor‐alpha (P < 0.04) and IL‐8 were less (P < 0.001) in the plasma from the PVS group, while IL‐6 and IL‐8 were less (P < 0.04) in the lung tissue from ventilated lungs in the PVS group. Conclusions: Based on this model, PVS decreases inflammatory injury both systemically and in the lung tissue with no adverse effect on oxygenation, ventilation, or lung function.     

Physiological effects of a lung-recruiting strategy applied during one-lung ventilation

Background: One‐lung ventilation (OLV) affects respiratory mechanics and ventilation/perfusion matching, reducing functional residual capacity of the ventilated lung. While the application of a lung‐recruiting manoeuvre (RM) on the ventilated lung has been shown to improve oxygenation, data regarding the impact of RM on respiratory mechanics are not available. Methods: Thirteen patients undergoing lung resection in lateral decubitus were studied. During OLV, a lung‐recruiting strategy consisting in a RM lasting 1 min followed by the application of positive end‐expiratory pressure 5 cmH₂O was applied to the ventilated lung. Haemodynamics, gas exchange and respiratory mechanics parameters were recorded on two‐lung ventilation (TLV_baseline), OLV before and 20 min after the RM (OLV_pre‐RM, OLV_post‐RM, respectively) and TLV_end. Haemodynamics parameters were also recorded during the RM. Results: The PaO₂/FiO₂ ratio was 358±126 on TLV_baseline; it decreased to 235±113 on OLV_pre‐RM (P<0.01) increased to 351±120 on OLV_post‐RM (P<0.01 vs. OLV_pre‐RM), and remain stable thereafter. During the RM, CI decreased from 3.04±0.7 l/m² OLV_pre‐RM to 2.4±0.6 l/m² (P<0.05), and returned to baseline on OLV_post‐RM (3.1±0.7 l/m², NS vs. OLV_pre‐RM). The RM resulted in alveolar recruitment and caused a significant decrease in static elastance of the dependent lung (16.6±8.9 cmH₂O/ml OLV_post‐RM vs. 22.3±8.1 cmH₂O/ml OLV_pre‐RM) (P<0.01). Conclusions: During OLV in lateral decubitus for thoracic surgery, application to the dependent lung a recruiting strategy significantly recruits the dependent lung, improving arterial oxygenation and respiratory mechanics until the end of surgery. However, the transient haemodynamic derangement occurring during the RM should be taken into account.     

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. Methods: Forty patients with chronic obstructive pulmonary disease scheduled for right lung tumour resection were randomized to undergo dependent (left) one‐lung ventilation (D‐OLV; n=20) or non‐dependent (right) one‐lung ventilation (ND‐OLV; n=20) in the supine and left lateral positions. Partial pressure of arterial oxygen (PaO₂) was measured as a surrogate for ventilation/perfusion matching. Patients were studied before surgery under closed chest conditions. Results: When compared with bilateral lung ventilation, both D‐OLV and ND‐OLV caused a significant and equal decrease in PaO₂ in the supine position. However, D‐OLV in the lateral position was associated with a higher PaO₂ as compared with the supine position [274.2 (77.6) vs. 181.9 (68.3) mmHg, P<0.01, analysis of variance (ANOVA)]. In contrast, in patients undergoing ND‐OLV, PaO₂ was always lower in the lateral as compared with the supine position [105.3 (63.2) vs. 187 (63.1) mmHg, P<0.01, ANOVA]. Conclusion: The relative position of the ventilated vs. the non‐ventilated lung markedly affects arterial oxygenation during OLV. These data suggest that gravity affects ventilation–perfusion matching independent of HPV.     

Effects of desflurane and propofol on arterial oxygenation during one-lung ventilation in the pig

Background: Desflurane depresses hypoxic pulmonary vasoconstriction (HPV) in vitro. During one-lung ventilation (OLV), HPV may reduce venous admixture and ameliorate the decrease in arterial O₂ tension by diverting blood from the non-ventilated to the ventilated lung. Accordingly, this study compares the effects of desflurane with those of propofol on oxygenation during two-lung (TLV) and OLV in vivo. Methods: Ten pigs (25–30 kg) were premedicated (flunitrazepam 0.4 mg/kg im), anaesthetized (induction: propofol 2 mg/kg iv; maintenance: N₂O/O₂ 50%/50%, desflurane 3%, propofol 50 μg kg^?1 min^?1, and vecuronium 0.2 mg kg^?1 h^?1 iv), orally intubated and mechanically ventilated. Femoral arterial and thermodilution pulmonary artery catheters were placed, and the orotracheal tube was replaced by a left-sided 28-Ch double-lumen tube (DLT) via tracheotomy. After DLT placement, N₂O and propofol were discontinued, FiO₂ was increased to 0.85, and anaesthesia continued randomly with either desflurane (1 MAC) or propofol 200 μg kg^?1 min^?1. Using a cross-over design, in each animal the effects of a), changing from TLV to OLV (left lung) during both desflurane and propofol and b), the effects of changing between the two anaesthetics during OLV were studied. Results: When changing from TLV to OLV, PaO₂ decreased more (P<0.05) during desflurane (mean 75%) than during propofol (mean 60%). Changing between desflurane and propofol during OLV resulted in small but consistent (P<0.05) increases in PaO₂ (mean 15%) during propofol. Conclusion: Consistent with in vitro results on HPV, 1 MAC desflurane impaired in vivo oxygenation during OLV more than did propofol.     

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

The purpose of this study was to determine the safety of onelung 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.     

The effect of timing of application of positive end-expiratory pressure on oxygenation during one-lung ventilation

Many studies have confirmed that applying positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation (OLV) improves oxygenation. Our purpose was to investigate the best time and level of PEEP application. Thirty patients undergoing thoracic surgery were randomised into three groups. After 20 minutes of two-lung ventilation (TLV) in the lateral position, all patients received OLV for one hour During OLV, 0, 5, 10 cmH2O PEEP were applied in order in group A, with each level sustained for 20 minutes. Group B had 5 cmH2O PEEP applied and maintained for one hour Patients in group C received PEEP with levels set in the opposite order to that of group A. The ventilation model was then converted to TLV. PaO2, PaCO2 and respiratory mechanical variables were compared at five different time points among groups, 20 minutes after TLV (T1), 20 (T2), 40 (T3) and 60 minutes (T4) after OLV and 20 minutes after conversion to TLV (T5). We found that PaO2 was lower in group A than the other two groups at T2 (P <0.05). PaO2 decreased significantly at T5 compared with T1 (P <0.05) in group A only. When PEEP was set to 10 cmH2O, the airway pressure increased significantly (P <0.05). These findings indicate that PEEP applied at the initial time of OLV improves oxygenation most beneficially. Five cmH2O PEEP may produce this beneficial effect without the increase in airway pressure associated with 10 cmH2O PEEP.     

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

Background. Poor positioning of an endobronchial double lumentube (DLT) could affect oxygenation during one lung ventilation(OLV). We set out to relate DLT position to hypoxaemia and DLTmisplacement during OLV. Methods. We recruited 152 ASA physical status I–II patientsabout to have elective thoracic surgery. The trachea was intubatedwith a left-sided DLT. Tube position was assessed by fibre-opticscope and correction was made after patient positioning andduring OLV. If Pa_O2 was less than 10.7 kPa, the DLT positionwas checked and then PEEP, continuous positive airway pressure(CPAP), oxygen insufflation, or two lung ventilation (TLV) weretried. Results. 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 insufflationto the non-dependent lung, or brief periods of TLV, were appliedin 46 patients (30%). Patients who had DLT malposition afterplacing the patient in the lateral position had a greater incidenceof DLT malposition during OLV (59 vs 9%) and also required eachintervention more frequently (57 vs 10%). Patients with DLTmalposition during OLV also required interventions more often(84 vs 12%). Conclusions. Patients who have DLT malposition after placingthe patient in the lateral position had more DLT malpositionduring OLV and hypoxaemia during OLV. Br J Anaesth 2004; 92: 195–201     

Effect of epidural dexmedetomidine on intraoperative awareness and post‐operative pain after one‐lung ventilation

Background: During combined general and regional anaesthesia, it is difficult to use autonomic signs to assess whether wakefulness is suppressed adequately. We compared the effects of a dexmedetomidine–bupivacaine mixture with plain bupivacaine for thoracic epidural anaesthesia on intraoperative awareness and analgesic benefits, when combined with superficial isoflurane anaesthesia (<0.05 maximum alveolar concentration) in patients undergoing thoracic surgery with one‐lung ventilation (OLV). Methods: Fifty adult male patients were randomly assigned to receive either epidural dexmedetomidine 1 μg/kg with bupivacaine 0.5% (group D) or bupivacaine 0.5% alone (group B) after induction of general anaesthesia. Gasometric, haemodynamic and bispectral index values were recorded. Post‐operative verbal rating score for pain and observer's assessment of alertness/sedation scale were determined by a blinded observer. Results: Dexmedetomidine reduced the use of supplementary fentanyl during surgery. Patients in group B consumed more analgesics and had higher pain scores after operation than patients of group D. The level of sedation was similar between the two groups in the ICU. Two patients (8%) in group B reported possible intraoperative awareness. There was a limited decrease in PaO₂ at OLV in group D compared with group B (P<0.05). Conclusion: In thoracic surgery with OLV, the use of epidural dexmedetomidine decreases the anaesthetic requirements significantly, prevents awareness during anaesthesia and improves intraoperative oxygenation and post‐operative analgesia.     

"Best" PEEP during one-lung ventilation

Eight patients were studied under general anaesthesia for elective pulmonary lobectomy to see if intrinsic positive end-expired pressure (PEEPi) would appear or increase in the dependent lung during one-lung ventilation (OLV) or if application of external PEEP equal to individually measured PEEPi would produce better arterial oxygenation, haemodynamic state and oxygen delivery than either zero PEEP (ZEEP) or an external PEEP 5 cm H2O greater than PEEPi. Patients were non-obese, without obstructive airways disease, aged 53-76 yr and ASA < III. They received standardized anaesthesia with fentanyl, 50% nitrous oxide in oxygen and isoflurane; monitoring included radial and fibreoptic pulmonary arterial catheters and intermittent positive pressure ventilation with a tidal volume of 8 ml kg-1, 16 bpm, and an I:E ratio of 1:2. PEEPi was measured during two-lung ventilation (TLV) and OLV, using rapid airway occlusion at end-expiration. There was no PEEPi during TLV, but 2-6 mm Hg of PEEPi appeared during OLV. Applying external PEEP equal to individually measured PEEPi reduced venous admixture and increased PaO2 without a decrease in cardiac index (thus increasing oxygen delivery) compared with ZEEP, but the improvement in pulmonary gas exchange was lost and an additional penalty of reduced cardiac output was imposed when external PEEP was increased to 5 mm Hg above PEEPi.      

Effects of tidal volume and PEEP on arterial blood gases and pulmonary mechanics during one-lung ventilation

Purpose

The main problem of one-lung ventilation (OLV) is hypoxemia. The use of a high tidal volume for preventing hypoxemia during OLV is controversial. We compared the effects of a high tidal volume versus a low tidal volume with or without PEEP on arterial oxygen tension (PaO₂) and pulmonary mechanics during OLV.

Methods

Sixty patients (age range, 16–65?years; ASA I, II) who underwent wedge resection with video-assisted thoracostomy during OLV were assigned to three groups: group I received a high tidal volume (10?ml/kg) (n?=?20), group II received a low tidal volume (6?ml/kg) (n?=?20), and group III received a low tidal volume (6?ml/kg) with PEEP (5?cmH₂O) (n?=?20). Patient hemodynamics, pulmonary mechanics, and arterial blood gases were measured before (T₀) OLV and 5 (T₁), 15 (T₂), 30 (T₃), and 45?min (T₄) after OLV.

Results

The PaO₂/FiO₂ ratios of group II and III were significantly decreased and the incidence of hypoxemia was significantly higher in groups II and III than in group I (P?Conclusion During OLV, mechanical ventilation with a low tidal volume with or without PEEP increased hypoxemia as compared to that when performing OLV with a high tidal volume.     

根据静态压力-容量曲线指导开胸手术病人保护性单肺通气的效果

目的 评价根据静态压力.容积曲线(P-V曲线)设置开胸手术病人的呼气末正压(PEEP)行单肺通气(OLV)的效果.方法 择期行肺叶切除术病人120例,性别不限,年龄20～60岁,体重40～ 80 kg,ASA分级Ⅱ或Ⅲ级.双肺通气(TLV)3 min后,描绘准静态P-V曲线,确定P-V曲线低位拐点对应的压力(PLIP).采用随机数字表法,将病人随机分为5组(n＝24):对照组(C组)和不同保护性OLV方式组(P1～4组).C组PEEP为0,vT为10 ml/kg;P1组PEEP为0,vT为6ml/kg; P2组PEEP为PLIP,-2 cm H2O,VT为6ml/kg;P3组PEEP为PLIP,VT为6 ml/kg;P4组PEEP为PLIP+2 cmH2O,VT为6 ml/kg.分别于TLV和OLV呼吸力学指标平稳后,记录气道峰压、气道平台压、气道阻力和肺顺应性.分别于麻醉诱导前、TLV 20 min和OLV 20 min时,取动脉血样,进行血气分析,计算肺内分流率.分别于OLV开始时和OLV结束时采集动脉血样,采用酶联免疫吸附法测定血浆II-6和TNF-α的浓度.结果 与C组比较,P4组TLV和OLV呼吸力学指标平稳后气道峰压和气道平台压升高,气道阻力降低,OLV结束时血浆IL-6浓度降低,P1组、P2组、P3组和P4组PaC02升高(P<0.05或0.01);P1组、P2组和P3组各呼吸力学指标、血气分析指标和血浆IL-6和TNF-α的浓度比较差异无统计学意义(P＞0.05).与P1组、P2组和P3组比较,P4组气道峰压和气道平台压升高,OLV结束时血浆IL-6浓度降低(P<0.05或0.01).结论 VT为6 ml/kg,根据PLIP+2 cm H2O确定PEEP,有助于改善开胸手术病人的氧合,抑制炎性反应,是保护性OLV的有效手段.     

Effect of PEEP on regional ventilation during laparoscopic surgery monitored by electrical impedance tomography

Background: Anesthesia per se and pneumoperitoneum during laparoscopic surgery lead to atelectasis and impairment of oxygenation. We hypothesized that a ventilation with positive end‐expiratory pressure (PEEP) during general anesthesia and laparoscopic surgery leads to a more homogeneous ventilation distribution as determined by electrical impedance tomography (EIT). Furthermore, we supposed that PEEP ventilation in lung‐healthy patients would improve the parameters of oxygenation and respiratory compliance. Methods: Thirty‐two patients scheduled to undergo laparoscopic cholecystectomy were randomly assigned to be ventilated with ZEEP (0 cmH₂O) or with PEEP (10 cmH₂O) and a subsequent recruitment maneuver. Differences in regional ventilation were analyzed by the EIT‐based center‐of‐ventilation index (COV), which quantifies the distribution of ventilation and indicates ventilation shifts. Results: Higher amount of ventilation was examined in the dorsal parts of the lungs in the PEEP group. Throughout the application of PEEP, a lower shift of ventilation was found, whereas after the induction of anesthesia, a remarkable ventral shift of ventilation in ZEEP‐ventilated patients (COV: ZEEP, 40.6 ± 2.4%; PEEP, 46.5 ± 3.5%; P<0.001) was observed. Compared with the PEEP group, ZEEP caused a ventral misalignment of ventilation during pneumoperitoneum (COV: ZEEP, 41.6 ± 2.4%; PEEP, 44 ± 2.7%; P=0.013). Throughout the study, there were significant differences in the parameters of oxygenation and respiratory compliance with improved values in PEEP‐ventilated patients. Conclusion: The effect of anesthesia, pneumoperitoneum, and different PEEP levels can be evaluated by EIT‐based COV monitoring. An initial recruitment maneuver and a PEEP of 10 cmH₂O preserved homogeneous regional ventilation during laparoscopic surgery in most, but not all, patients and improved oxygenation and respiratory compliance.     

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.     

Intermittent reinflation is safe to maintain oxygenation without alteration of extravascular lung water during one-lung ventilation

Study ObjectiveTo investigate whether a maneuver for repeated cycles of collapse and reexpansion of the operative lung, termed “intermittent reinflation” (IR), to counter hypoxemia during one-lung ventilation (OLV), results in a time-dependent alteration of extravascular lung water.DesignProspective, randomized clinical study.SettingOperating room and postsurgical intensive care unit of a university hospital.Patients36 ASA physical status 1 and 2 patients undergoing elective, video-assisted thoracic surgery for lung tumors.InterventionsPatients were randomly assigned to two groups. Group C consisted of 18 patients whose nondependent lung was kept collapsed during OLV, while Group IR included 18 patients with IR that consisted of 4 separate, 10-second manual inflations and 5-second openings within one minute at intervals of 20 minutes during OLV.MeasurementsPerioperative parameters included transcutaneous oxygen saturation (SpO₂), hemodynamic data, extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI) as determined by the single-indicator transpulmonary thermodilution technique, and partial pressure of arterial oxygen/inspired oxygen fraction (PaO₂/FIO₂) ratio.Main ResultsGroup IR had significantly higher SpO₂ at 20 minutes after commencement of OLV (98.9% vs 96.3%, P = 0.029) and average SpO₂ throughout OLV (98.7% vs 97.0%, P = 0.020). Hemodynamic data, EVLWI, PVPI, and PaO₂/FIO₂ ratio did not differ between the groups, and there were no differences between groups in postoperative morbidity or hospital stay.ConclusionsIntermittent reinflation had a beneficial effect on oxygenation during OLV, without any significant effects on EVLW or postoperative outcomes.     

Capnography reflects ventilation/perfusion distribution in a model of acute lung injury

Background: Changes in the shape of the capnogram may reflect changes in lung physiology. We studied the effect of different ventilation/perfusion ratios (V/Q) induced by positive end‐expiratory pressures (PEEP) and lung recruitment on phase III slope (S_III) of volumetric capnograms. Methods: Seven lung‐lavaged pigs received volume control ventilation at tidal volumes of 6 ml/kg. After a lung recruitment maneuver, open‐lung PEEP (OL‐PEEP) was defined at 2 cmH₂O above the PEEP at the onset of lung collapse as identified by the maximum respiratory compliance during a decremental PEEP trial. Thereafter, six distinct PEEP levels either at OL‐PEEP, 4 cmH₂O above or below this level were applied in a random order, either with or without a prior lung recruitment maneuver. Ventilation–perfusion distribution (using multiple inert gas elimination technique), hemodynamics, blood gases and volumetric capnography data were recorded at the end of each condition (minute 40). Results: S _III showed the lowest value whenever lung recruitment and OL‐PEEP were jointly applied and was associated with the lowest dispersion of ventilation and perfusion (Disp_R?E), the lowest ratio of alveolar dead space to alveolar tidal volume (VD_alv/VT_alv) and the lowest difference between arterial and end‐tidal pCO₂ (Pa?ETCO₂). Spearman's rank correlations between S_III and Disp_R?E showed a ρ=0.85 with 95% CI for ρ (Fisher's Z‐transformation) of 0.74–0.91, P<0.0001. Conclusion: In this experimental model of lung injury, changes in the phase III slope of the capnograms were directly correlated with the degree of ventilation/perfusion dispersion.     

Histochemical alterations in one lung ventilation

BACKGROUND: One lung ventilation is a commonly performed surgical procedure. Although there have been several reports showing that one-lung ventilation can cause pathophysiological alterations such as pulmonary hypoxic vasoconstriction and intrapulmonary shunting, there have been virtually no reports on the effects of one-lung ventilation on lung histology. MATERIALS AND METHODS: Yorkshire pigs (11-17 kg) were anesthetized, a tracheotomy performed and a tracheal tube inserted. The chest was opened and one lung ventilation (OLV), was induced by clamping of the right main bronchus. OLV was continued for 60 min before the clamp was removed and two lung ventilation (TLV) started. TLV was continued for 30 to 60 min. Blood and lung biopsies were taken immediately before OLV, 30 min and 60 min of OLV and after restoration of TLV. RESULTS: Histological analyses revealed that the non-ventilated lung was totally collapsed during OLV. On reventilation, there was clear evidence of vascular congestion and alveolar wall thickening at 30 min after TLV. At 60 min of TLV, there was still vascular congestion. Serum nitrite levels (as an index of nitric oxide production) showed steady decline over the course of the experimental period, reaching a significantly low level on reventilation (compared with baseline levels before OLV). Lung MPO activity (marker of neutrophil sequestration) and serum TNFalpha levels were not raised during the entire experimental period. CONCLUSIONS: These results suggest that there was lung vascular injury after OLV, which was associated with reduced levels of nitric oxide production and not associated with an inflammatory response.     

Monitoring of vecuronium-induced neuromuscular blockade during one-lung ventilation

Purpose  We investigated the monitoring of neuromuscular blockade caused by vecuronium in patients receiving one-lung ventilation (OLV) anesthesia for lung surgery. Methods  Eighteen adult patients requiring OLV for lung surgery (OLV group) and 18 undergoing two-lung ventilation (TLV) for colon surgery (control group) were enrolled in this study. In the two groups, anesthesia was maintained with sevoflurane, fentanyl, and epidural lidocaine. Time from vecuronium 0.1 mg·kg⁻¹ to the onset of neuromuscular blockade; times to the return of T1, T2, T3, or T4 (the first, second, third, or fourth response of the train-of-four [TOF]); and recovery of T1/control or TOF ratio (T4/T1) were compared between the two groups. Results  Time to the onset of neuromuscular blockade in the OLV group was similar to that in the control group (289 ± 74 vs 270 ± 85 s [mean ± SD]; P = 0.482). Times from vecuronium to the return of T1, T2, T3, or T4 in the OLV group did not significantly differ from those in the control group (21.9 ± 7.0 vs 25.8 ± 6.7 min for T1; P = 0.099). T1/control in the OLV group was significantly higher than that in the control group 50-120 min after vecuronium (P < 0.05). The TOF ratio did not differ significantly between the two groups. Conclusion  During OLV for lung surgery, recovery of T1/control is accelerated in anesthetized patients receiving vecuronium.     

Smoking as a risk factor for intraoperative hypoxemia during one lung ventilation

Background

Smoking is associated with many intra and postoperative events, especially respiratory complications. Hypoxemia and airway damage are found to aggravate any pre-existing respiratory pathology among smokers. One lung ventilation (OLV) carries a 4–10 % risk of development of hypoxia.

Aim

The purpose of this study was to predict the incidence of hypoxemia for smokers during OLV for patients undergoing video-assisted thoracoscopic surgery (VATS).

Patients and methods

Sixty patients undergoing VATS using OLV by double lumen tube were included in this pilot cross-sectional study. These patients were divided into 2 groups, group S which included 30 heavy smoker patients (smoking more than 20 cigarettes per day for more than 20 years) and group NS which included 30 non-smoker patients. Intra and postoperative arterial oxygen tension (PaO₂), arterial carbon dioxide tension (PaCO₂), and intraoperative peak airway pressure were compared between the 2 groups.

Results

PaO₂ was significantly higher in the non-smoker group than in the smoker group, both at the start and end of OLV. It was 173 ± 68 mmHg for NS compared with 74 ± 10.8 mmHg for S at the start of OLV; at the end of OLV it was 410 ± 78 mmHg for the former and 360 ± 72 mmHg for the latter (P < 0.05).

Conclusion

From this study it can be concluded that for heavy smoker patients there was a significant reduction in arterial oxygen tension (PaO₂) in comparison with non-smokers. However, hypoxemia reported for both groups was comparable.     

Experimental model of laryngotracheal stenosis in infants: effects of different high-frequency jet ventilation patterns on pulmonary parameters

Background: Supraglottic high‐frequency jet ventilation (HFJV) in laryngotracheal surgery in infants with modified jet laryngoscopes offers the surgeon an unimpaired operating field. However, supraglottic HFJV is associated with the development of high airway pressures, inadvertent positive end‐expiratory pressure (PEEP) levels, and barotrauma. Methods: We investigated the total lung volumes (TLV) and tidal volume variations at peak inspiratory pressure levels (PIP) and at PEEP levels along with the pulmonary pressures (PIP and PEEP) during two conventional methods of supraglottic HFJV in an infant trachea–lung model without stenosis and with different degrees of stenosis. Results: With augmentation of the driving pressure in the experiment without stenosis, the TLV plus the pulmonary pressures increased. With narrowing of the stenosis, TLV reduced at PIP level and increased at PEEP level. Volume shifts were significantly higher during superimposed HFJV compared with monofrequent HFJV at equivalent stenosis diameter (P < 0.05) except for the setting with 0.3 bar driving pressure (P > 0.05). The pulmonary PIP was in none of the test series higher than 20 mbar, and the pulmonary PEEP did not exceed 14 mbar. Conclusions: The results from our experimental model support the safe and effective clinical use of supraglottic HFJV in infants with tracheal stenosis. Moderate driving pressures provide acceptable pulmonary pressures in normal compliant lungs.