End-expiratory lung volume and ventilation distribution with different continuous positive airway pressure systems in volunteers

Background: Continuous positive airway pressure (CPAP) has been shown to improve oxygenation and a number of different CPAP systems are available. The aim of this study was to assess lung volume and ventilation distribution using three different CPAP techniques. Methods: A high‐flow CPAP system (HF‐CPAP), an ejector‐driven system (E‐CPAP) and CPAP using a Servo 300 ventilator (V‐CPAP) were randomly applied at 0, 5 and 10 cmH₂O in 14 volunteers. End‐expiratory lung volume (EELV) was measured by N₂ dilution at baseline; changes in EELV and tidal volume distribution were assessed by electric impedance tomography. Results: Higher end‐expiratory and mean airway pressures were found using the E‐CPAP vs. the HF‐CPAP and the V‐CPAP system (P<0.01). EELV increased markedly from baseline, 0 cmH₂O, with increased CPAP levels: 1110±380, 1620±520 and 1130±350 ml for HF‐, E‐ and V‐CPAP, respectively, at 10 cmH₂O. A larger fraction of the increase in EELV occurred for all systems in ventral compared with dorsal regions (P<0.01). In contrast, tidal ventilation was increasingly directed toward dorsal regions with increasing CPAP levels (P<0.01). The increase in EELV as well as the tidal volume redistribution were more pronounced with the E‐CPAP system as compared with both the HF‐CPAP and the V‐CPAP systems (P<0.05) at 10 cmH₂O. Conclusion: EELV increased more in ventral regions with increasing CPAP levels, independent of systems, leading to a redistribution of tidal ventilation toward dorsal regions. Different CPAP systems resulted in different airway pressure profiles, which may result in different lung volume expansion and tidal volume distribution.     

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.     

An individualized recruitment maneuver for mechanically ventilated patients after cardiac surgery

Purpose  The recruitment maneuver (RM) has been shown to improve oxygenation for post-cardiopulmonary bypass (CPB) patients; however, sustained inflation of the lung gives rise to hypotension. The primary goal of our study was to evaluate the safety and efficacy of our proposed RM, defined on the basis of dynamic lung compliance (Cdyn). Methods  Twenty-eight patients undergoing elective cardiac surgery with CPB were assigned to two treatment groups: an individualized RM group, in which a pressure equal to 15 ml × real body weight/Cdyn + positive end-expiratory pressure (PEEP) cmH₂O was applied for 15 s; and a control RM group, in which a pressure of 20 cmH₂O was applied for 25 s. Arterial blood pressure, cardiac output, pulmonary artery pressure, and heart rate (HR) were monitored. Tidal volume (V_T), and airway pressure were continuously obtained from an expiratory flow meter and pressure monitor. Blood samples were obtained and analyzed with a blood gas analyzer. Results  The changes in HR, mean arterial pressure, mean pulmonary artery pressure, and cardiac index at the end of the RM were not significantly different between the two groups. The mean airway pressure of sustained inflation was 28.3 ± 1.3 cmH₂O in the individualized RM group. The individualized RM significantly improved the Cdyn and partial pressure arterial oxygen/inspiratory fraction of oxygen (P/F) ratio compared with values in the control RM group (P = 0.026 and P = 0.012, respectively). Conclusion  The present study indicates that the individualized RM resulted in minimum changes of hemodynamics and brought about improvement in oxygenation and lung compliance.     

Better postoperative oxygenation in thoracoscopic esophagectomy in prone positioning

Intrathoracic procedures can be performed with thoracoscopy in esophagectomy because the laparoscopic technique has recently been developed. During intrathoracic procedures, prone positioning of the patient allows gravity to facilitate optimal exposure of the esophagus, thereby affording a superb surgical view. In the current study, we compared the influence of prone positioning with lateral decubitus positioning on oxygenation in esophagectomy. We enrolled 18 patients and divided them into two groups: patients who underwent esophagectomy via thoracoscopy in the prone position (group P) and patients who underwent thoracotomy in the lateral decubitus position (control group, group L). Arterial blood gas analyses were performed before the operation was started (T1), 20 min after the initiation of one-lung ventilation (OLV) (T2), and two other points. The P/F ratio at T2 in group P was higher. Further, percent (%) change of the P/F ratios from T1 and thereafter in group P was higher at all points. We thought the reason why the prone position had contributed to maintenance oxygenation was as follows. First, the functional residual capacity and ventilation/perfusion matching in the prone position are satisfactory. Second, a bronchial blocker might contribute to reduction of atelectasis. Third, minimally invasive esophagectomy might reduce respiratory complications and blood loss because this procedure reduces edema and inflammation in the lung. In conclusion, the oxygenation provided by prone positioning is better than that provided by the lateral decubitus position during OLV in esophagectomy.     

Efficacy and safety of artificial pneumothorax under two-lung ventilation in thoracoscopic esophagectomy for esophageal cancer in the prone position

Background

Thoracoscopic esophagectomy for esophageal cancer performed using two-lung ventilation in the prone position has many advantages, such as convenient anesthesia induction and maintenance, and good oxygenation. We examined the safety of surgery and anesthetic management by following chronological changes in intraoperative respiration and hemodynamics.

Methods

We focused on the most recent and consecutive 14 cases of thoracoscopic esophagectomy for esophageal cancer in the prone position performed from November 2010 until recently. We measured the following items by use of FloTrac system : cardiac index (CI), central venous pressure (CVP), mean arterial pressure, partial pressure of oxygen in arterial blood (PaO₂), partial pressure of carbon dioxide in arterial blood (PaCO₂), peak airway pressure (APmax), and tidal volume.

Results

No major changes were observed in CI, systolic blood pressure, and TV after the start of pneumothorax (statically not significant). Conversely, CVP increased immediately after pneumothorax (p < 0.05) and decreased almost to its original level thereafter. The mean APmax value was 18–20 cm H₂O [mean increase, 4.2 cm H₂O; (p < 0.05)]. The mean P/F ratio and mean PaCO₂ were 244.4 and 48.3 mmHg, respectively, during artificial pneumothorax.

Conclusion

No excessive increases in airway pressure or clear circulatory depressions were observed because of artificial pneumothorax under two-lung ventilation in thoracoscopic esophagectomy for esophageal cancer in the prone position. These results suggest that artificial pneumothorax under two-lung ventilation is beneficial for maintaining stable hemodynamics and oxygenation in thoracoscopic esophagectomy in prone position.     

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.     

Iloprost inhalation redistributes pulmonary perfusion and decreases arterial oxygenation in healthy volunteers

Background: Previous studies have shown that ventilation–perfusion matching is improved in the prone as compared with that in the supine position. Regional differences in the regulation of vascular tone may explain this. We have recently demonstrated higher production of nitric oxide in dorsal compared with ventral human lung tissue. The purpose of the present study was to investigate regional differences in actions by another vasoactive mediator, namely prostacyclin. The effects on gas exchange and regional pulmonary perfusion in different body positions were investigated at increased prostacyclin levels by inhalation of a synthetic prostacyclin analogue and decreased prostacyclin levels by unselective cyclooxygenase (COX) inhibition. Methods: In 19 volunteers, regional pulmonary perfusion in the prone and supine position was assessed by single photon emission computed tomography using ^99mTc macro‐aggregated albumin before and after inhalation of iloprost, a stable prostacyclin analogue, or an intravenous infusion of a non‐selective COX inhibitor, diclofenac. In addition, gas distribution was assessed in seven subjects using ^99mTc‐labelled ultra‐fine carbon particles before and after iloprost inhalation in the supine position. Results: Iloprost inhalation decreased arterial PaO₂ in both prone (from 14.2±0.5 to 11.7±1.7 kPa, P<0.01) and supine (from 13.7±1.4 to 10.9±2.1 kPa, P<0.01) positions. Iloprost inhalation redistributed lung perfusion from non‐dependent to dependent lung regions in both prone and supine positions, while ventilation in the supine position was distributed in the opposite direction. No significant effects of non‐selective COX inhibition were found in this study. Conclusions: Iloprost inhalation decreases arterial oxygenation and results in a more gravity‐dependent pulmonary perfusion in both supine and prone positions in healthy humans.     

Exposure to anaesthetic trace gases during general anaesthesia: CobraPLA vs. LMA classic

Background: To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Methods: Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N₂O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. Results: N₂O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7±7.2 p.p.m. in CobraPLA vs. 4.1±4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16±3 vs. 14±2 cmH₂O, P=0.01). The average leak pressure of the CobraPLA was 24±4 cmH₂O, compared with 20±4 cmH₂O of the LMA classic (P<0.001; all values means±SD). Conclusion: Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N₂O trace concentrations in the anaesthetists' breathing zone.     

Comparison of the CobraPLA (Cobra Perilaryngeal Airway) and the Laryngeal Mask Airway Unique in children under pressure controlled ventilation

Background: The Laryngeal Mask Airway‐Unique (LMAU) and CobraPLA^TM (Cobra Perilaryngeal Airway) are supraglottic airway devices. There are no published studies comparing these devices in children breathing with pressure controlled ventilation (PCV). Methods: Eighty pediatric patients, scheduled for elective general surgery of short duration, were randomly assigned to have either a CobraPLA^TM or a LMAU used for airway management using PCV. We compared the devices with respect to (i) ability to form an effective cuff seal, (ii) oxygenation, (iii) endtidal carbon dioxide level, (iv) time to achieve an effective airway, (v) airway interventions required for insertion, (vi) fiberoptic score, (vii) respiratory variables and (vii) adverse events. Results: Cuff seal pressure was significantly higher for CobraPLA^TM (27.08 ± 4.15 cmH₂O) than for LMAU (20.91 ± 2.47 cmH₂O). Oxygenation was similar in both groups while the mean endtidal CO₂ in the CobraPLA^TM group was significantly higher than in the LMAU group (36.47 ± 1.93 mmHg vs 34.71 ± 3.05 mmHg, P = 0.021). Time and ease of insertion were similar, with CobraPLA^TM requiring more frequent jaw lift and LMAU requiring more frequent adjustment of the head and neck to achieve a proper position. Fiberoptic scores were excellent with both devices. Respiratory variables were similar with the exception that the plateau pressure and mean peak pressures were significantly lower with CobraPLA^TM. There was a low rate of blood mucosal staining of the devices. No patient in either group reported a sore throat. Conclusions: Both devices appear to be safe and effective in establishing an adequate airway in healthy children undergoing surgery of short duration with PCV.     

A comparison of the I-Gel supraglottic device with endotracheal intubation for bronchoscopic lung volume reduction coil treatment

Study objectiveTo compare the use of the I-gel airway with orotracheal intubation (OTI) for bronchoscopic lung volume reduction (BLVR) coil treatment in patients with severe chronic obstructive pulmonary disease (COPD) with heterogeneous emphysema, since it has been proved that supraglottic airways have lower incidence of postoperative respiratory complaints compared to OTI.DesignA comparative, prospective observational study was designed to assess the use of the I-gel airway compared with the OTI.SettingBronchoscopy room at the University Hospital Fundación Jimenez Diaz, Madrid. Tertiary care center.PatientsThirty-three procedures were carried out in 22 patients diagnosed with COPD with severe heterogeneous emphysema undergoing BLVR coil treatment under general anaesthesia.InterventionSeventeen procedures were carried out with I-gel and 16 with endotracheal tube. Airway device choice was left to the attendant anesthesiologist.MeasurementsTidal volume, peak pressure, and the presence of gas leaks were compared. Adverse events during the procedure and within the first 3 hours later were also recorded.Main resultsVentilation parameters obtained showed no significant differences. Mean tidal volume was 466.6 ± 28.2 mL and 478.7 ± 34.0 mL (P > .05), mean peak pressure was 17.9 ± 2.5 cmH₂O and 19.4 ± 2.4 cmH₂O (P > .05) and mean gas leaks was 71 ± 17.6 mL and 79 ± 15.5 mL (P > .05) for I-gel group (IgelG) and endotracheal tube group respectively. No serious complications were reported. One case of pneumothorax was reported in the endotracheal tube group, which was resolved with a chest drainage tube without further complications.ConclusionThe I-gel airway ensures appropriate ventilation and makes the use of the flexible fiberoptic bronchoscope quite easy. Therefore, we consider that the I-gel device is an effective and safe alternative to classical OTI for airway management in COPD patients with severe heterogeneous emphysema undergoing BLVR coil treatment.     

Effect of high-frequency jet ventilation on oxygenation during one-lung ventilation in patients undergoing thoracic aneurysm surgery

Purpose To evaluate the effect of high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) on oxygenation and the shunt fraction (Qs/Qt) during one-lung ventilation (OLV). Methods Twenty-five patients who were undergoing resection of a descending aortic aneurysm were studied. Arterial oxygenation, Qs/Qt, and hemodynamics were evaluated just before the initiation of OLV (T₁), 15 min after OLV (T₂), and 15 min (T₃) and 30 min (T₄) after the application of HFJV or CPAP to the nondependent lung. Results There were no significant changes in the mean arterial blood pressure (MAP), heart rate (HR), central venous pressure (CVP), or mixed venous partial pressure of oxygen throughout this study. The arterial partial pressure of oxygen (Pa_O2) values after the application of HFJV or CPAP increased significantly, from 173.8 ± 39.6 mmHg (T₂) to 344.1 ± 87.9 mmHg (T₃) and 359.9 ± 82.4 mmHg (T₄) in the HFJV group (P < 0.05), and from 153 ± 38.5 mmHg (T₂) to 243 ± 48.5 mmHg (T₃) and 249.7 ± 55.0 mmHg (T₄) in the CPAP group (P < 0.05). The shunt fraction decreased significantly after the initiation of HFJV or CPAP, from 38.7% ± 8.9% (T₂) to 27.0% ± 8.0% (T₃) and 25.9% ± 8.7% (T₄) in the HFJV group (P < 0.05), and from 44.6% ± 8.6% (T₂) to 34.3% ± 10.2% (T₃) and 32.6% ± 8.5% (T₄) in the CPAP group (P < 0.05). The arterial saturation of oxygen (Sa_O2) increased significantly after the application of either HFJV or CPAP (P < 0.05). Conclusions Both HFJV and CPAP can improve oxygenation during OLV.     

Application of PEEP using the i-gel during volume-controlled ventilation in anesthetized, paralyzed patients

Purpose

This prospective, randomized trial was designed to assess whether the i-gel supraglottic airway device is suitable for volume-controlled ventilation while applying positive end-expiratory pressure (PEEP) of 5 cmH₂O under general anesthesia. It was believed that this device might improve arterial oxygenation.

Methods

Forty adult patients (aged 20–60 years) scheduled for elective orthopedic surgery were enrolled in this study. Twenty patients were ventilated without external PEEP [zero positive end-expiratory pressure (ZEEP) group], and the other 20 were ventilated with PEEP 5 cmH₂O (PEEP group) after placing an i-gel device. Volume-controlled ventilation at a tidal volume (TV) of 8 ml/kg of ideal body weight, leak volume, and arterial blood gas analysis were investigated.

Results

The incidences of a significant leak were similar in the ZEEP and PEEP groups (3/20 and 1/20, respectively; P = 0.605), as were leak volumes. No significant PaO₂ difference was observed between the two groups at 1 h after satisfactory i-gel insertion (215 ± 38 vs. 222 ± 54; P = 0.502).

Conclusions

The use of an i-gel during PEEP application at 5 cmH₂O did not increase the incidence of a significant air leak, and a PEEP of 5 cmH₂O failed to improve arterial oxygenation during controlled ventilation in healthy adult patients.     

ProSeal?-Kehlkopfmaske in normalgewichtigen und adip?sen Patienten

Background

Most of the data on combining pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) come from studies with an endotracheal tube (ETT) whereas data on utilization of PEEP with a laryngeal mask airway (LMA) are limited. The LMA-ProSeal? (PLMA) forms a more effective seal of the airway than the LMA-Classic? (CLMA). The application of PEEP when PCV is used with the PLMA could have an impact on oxygenation in adult patients.

Methods

For this study 148 patients with an mean age of 44 years (range18?C65 years) and mean weight of 86?kg (range 49?C120?kg) were recruited in 2 groups: group?N _(Normal): body-mass index (BMI) <30?kg/m² and group?O _(Obesity) BMI ??30 and <36?kg/m². Cardiovascular and pulmonary disease and a history of smoking were exclusion criteria in addition to the usual LMA contraindications. The bispectral index-guided (BIS) anesthesia technique was used with propofol, fentanyl, and remifentanil without muscle relaxants. Measurement of PLMA seal pressure served as recruitment maneuver and PCV was randomly combined with 0?cmH₂O, 5?cmH₂O or 8?cmH₂O PEEP. An arterial blood gas sample was taken 50?min after induction of anesthesia under an inspiratory oxygen fraction (F_IO₂₎ of 0.3. In the first part partial oxygen pressure (p_aO₂) under 0?cmH₂O was compared with p_aO₂ under 5?cmH₂O and in the second part p_aO₂ under 5?cmH₂O was compared with p_aO₂ under 8?cmH₂O. A significant difference was set as p<0.025.

Results

The PLMA could be placed after 3 attempts in 147 patients. The mean seal pressure was in the range of 24?C30?cm?H₂O. Application of randomized PEEP was possible in all patients and ventilation was comparable between corresponding groups. In group?N no differences were found in part?1 (139±28 vs. 141±28?mmHg, p=0.88) or part?2 (127±24 vs. 134±26?mmHg, p=0.35). In group?O there was a significant difference in p_aO₂ in part?1 (75±12 vs. 94±18?mmHg, p=0.02) but not in part?2 (92±21 vs. 103±18?mmHg, p=0.04).

Conclusions

The application of PEEP when PCV is used with the PLMA results in improved oxygenation in obese patients with a BMI ??30 and <36?kg/m² but not in normal weight patients. Alveolar recruitment produced by seal pressure measurements below 30?cm?H₂O was sufficient to produce a clinically significant improvement in oxygenation in most obese patients and there was a significant improvement of oxygenation with PEEP=5?cmH₂O. Both findings are in contrast to findings of studies using an ETT which suggests that higher pressures (40?cmH₂O) are needed for recruitment of collapsed alveoli and higher PEEP (10?cmH₂O) is needed to produce a clinically significant improvement in oxygenation in obese patients. The results of this study support data showing that the consequences of bronchopulmonary airway reactions known to occur with an ETT are less pronounced or absent when an LMA is used.     

Transcutaneous pressure at which the internal jugular vein is collapsed on ultrasonic imaging predicts easiness of the venous puncture

Even though we use ultrasound guidance for central venous puncture, we sometimes experience difficulties. We infer that in such cases the vein is collapsed and that the transcutaneous ultrasound probe pressure at which the vein is collapsed (P _tc) may predict the easiness of the venous puncture. We measured P _tc and the diameter of the internal jugular vein in 47 adult patients in our ICU. After successful puncture, we also measured venous pressure (P _v). The patients were divided into two groups based on the number of puncture attempts: ≥3 attempts constituted the “difficult group” and <3 attempts was considered the “easy group:” 33 patients were in the easy group and 14 patients were in the difficult group. The easy group showed significantly higher P _tc value (9.3 ± 3.8 vs. 3.5 ± 0.9 cmH₂O, P < 0.0001) and larger vertical diameter (9.2 ± 3.1 vs. 6.8 ± 2.2 mm, P = 0.013) than the difficult group. We observed a clear border between the minimum P _tc in the easy group (6 cmH₂O) and the maximum value in the difficult group (5 cmH₂O). In conclusion, venous collapsibility and vertical diameter determine difficulty in performing venous puncture.     

Funktionelle Trennung der Lungen

Independent lung ventilation was performed in a patient with severe hypoxemia (oxygenation ratio p_aO₂/F_IO₂ 61 mmHg) due to unilateral blunt chest trauma and consecutive consolidation of the injured lung. Recruitment and immobilization of the consolidated lung was achieved by functional separation of both lungs with application of a mean airway pressure (p_mean) of 28 mbar in combination with low frequency ventilation (4/min) of the injured lung. Adequate ventilation was maintained via the normal lung (p_mean 14 mbar). This ventilation strategy stabilized oxygenation and ventilation by preventing overinflation and ventilator-induced lung injury.     

Effects of surfactant replacement on alveolar overdistension and plasma cytokines in ventilator‐induced lung injury

Background: Overdistension of the lung causes ventilator‐induced lung injury (VILI) accompanied by surfactant abnormalities and inflammatory changes. We investigated the effects of surfactant replacement on overdistension of the terminal airspaces and plasma cytokine levels in VILI. Methods: VILI was induced by high‐pressure ventilation (HPV) in rats anesthetized with pentobarbital, followed by ventilation for 2 h in the maintenance mode (tidal volume=10 ml/kg, positive end‐expiratory pressure=7.5 cmH₂O) with or without surfactant replacement. The sizes of the terminal airspaces were determined after fixing the lungs at an airway pressure of 10 cmH₂O on deflation. Cytokine levels were assessed by enzyme‐linked immunosorbent assay. Results: The mean ratio of the largest terminal airspace size class (≥64,000 μm²) was increased from 13.4% to 32.0% by HPV (P<0.05). After maintenance‐mode ventilation, the ratio decreased to 16.1% with surfactant replacement (P<0.05), but increased to 44.6% without surfactant replacement (P<0.05). Mean macrophage inflammatory protein‐2 (MIP‐2) levels in the plasma increased from <0.02 to 6.9 ng/ml with HPV (P<0.05), and further increased to ≥11.8 ng/ml, regardless of surfactant replacement after maintenance‐mode ventilation. Similar tendencies were observed in the interleukin (IL)‐6 and IL‐10 levels. Tumor necrosis factor‐α levels were almost negligible during the experiment. Conclusion: In rats with VILI, surfactant replacement reversed overdistension of the terminal airspaces that may induce barotrauma, but not upregulation of MIP‐2, IL‐6, and IL‐10 within 2 h.     

The Effect of Patient Position on Leak-Point Pressure Measurements in Women with Genuine Stress Incontinence

The aim of this study was to determine the quantitative and qualitative effects of patient position on coughing and Valsalva leak-point pressure in women with genunie stress incontinence. Thirty-seven patients with genuine stress incontinence and 4 with mixed incontinence underwent multichannel urodynamics using a standardized protocol. Leak-point pressures were performed using 8 Fr microtip catheters placed in the bladder and vagina at a bladder volume of 250 ml in the supine, semirecumbent and standing positions. Urethral pressure profilometry was performed in the semirecumbent position at a bladder volume of 250 ml. The mean (range) age, and median (range) gravidity, parity, body mass index (BMI), and mean (range) Q-tip deflection angle were 61 years (36–80), 3 (1–8), 3 (1–6), 26 (22–30) and 55.8° (25°–80°), respectively. The mean (± standard deviation) Valsalva leak-point pressures in the supine, semirecumbent and standing positions were 82 ± 23, 73 ± 24 and 63 ± 22 cmH₂O, respectively (P<0.001). The mean (± standard deviation) cough leak-point pressures also decreased as the patients were moved from the supine (98 ± 29 cmH₂O) to the semirecumbent (88 ± 24 cmH₂O) and standing positions (77 ± 24 cmH₂O) (P<0.001). The correlation between leak-point pressure and maximum urethral closure pressure was statistically significant and was dependent upon patient position and the provocative maneuver used.     

Effect of Ono-EI-600 elastase inhibitor on high-tidal-volume-induced lung injury in rats

We tested the effect of Ono-EI-600, an elastase inhibitor that suppresses cytokine release, on ventilator-induced lung injury in a rat model. After Wistar rats (aged 8–11 weeks) were anesthetized and tracheostomized, they were randomly assigned to four groups: high tidal volume (V_T) group (H group: n = 10) receiving peak inspiratory pressure (PIP) 30 cmH₂O for 240 min; high V_T with drug group (HD group: n = 10) receiving the same ventilation settings as H group and also intravenous infusion 10 mg·kg⁻¹·h⁻¹ of Ono-EI-600 during the protocol; the lower V_T group (L group: n = 5) receiving PIP 10 cmH₂O for 240 min; and control group (C group: n = 5) receiving the same ventilation as L group for 30 min. The cytokine levels (IL-6 and CINC-1) in the bronchoalveolar lavage fluid (BALF) of the H group were significantly higher than those of the C and L groups (P < 0.05). However, for the H and HD groups, no differences were found in arterial blood gas data, cytokine levels in BALF, and histological injury scores. Our experiment provided no evidence that elastase inhibitor Ono-EI-600 protects against lung injury induced by high V_T ventilation.     

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.     

Co-administration of ephedrine prevents reductions in cardiac output and systemic oxygen delivery secondary to lung compression maneuvers during one-lung ventilation, without reducing arterial oxygenation

Purpose  

We previously showed that compression of the nondependent lung during one-lung ventilation (OLV) in patients undergoing esophagectomy improves arterial oxygenation but impairs cardiac output (CO) and systemic oxygen delivery (DO₂). The objective of this study was to test the hypothesis that the combination of nondependent lung compression and ephedrine improves arterial oxygenation without compromising DO₂.