Arterial Oxygenation In Patients Research Articles

The impact of intravenous dodecafluoropentane on a murine model of acute lung injury

IntroductionIntravenous oxygen therapeutics present an appealing option for improving arterial oxygenation in patients with acute hypoxemic respiratory failure, while limiting iatrogenic injury from conventional respiratory management.MethodsWe used an established two-hit murine model of acute lung injury (ARDS/VILI) to evaluate the effect of intravenous dodecafluoropentane (DDFPe) on oxygen saturation and bronchoalveolar lavage cell counts and protein levels. Twenty hours after challenge with intratracheal lipopolysaccharide, mice were intubated and ventilated with high tidal volumes (4 h) to produce acute lung injury. DDFPe (0.6 mL/kg) or saline was administered by IV bolus injection at the initiation of mechanical ventilation and again at 2 h. Oxygen saturation was measured every 15 min. Bronchoalveolar lavage was performed at the conclusion of the experiment.ResultsThe two-hit ARDS/VILI model produced substantial inflammatory acute lung injury reflected by markedly increased bronchoalveolar lavage (BAL) cell counts compared to BAL cell counts in spontaneous breathing controls (5.29 ± 1.50 × 10–6 vs 0.74 ± 0.014 × 10–6 cells/mL) Similarly, BAL protein levels were markedly elevated in ARDS/VILI-challenged mice compared with spontaneous breathing controls (1109.27 ± 223.80 vs 129.6 ± 9.75 ng/mL). We fit a linear mixed effects model that showed a significant difference in oxygen saturation over time between DDFPe-treated mice and saline-treated mice, with separation starting after the 2-h injection. DDFPe-treated ARDS/VILI-challenged mice also exhibited significant reductions in BAL cell counts but not in BAL protein.ConclusionDDFPe improves oxygen saturation in a murine model of ARDS/VILI injury with the potential for serving as an intravenous oxygen therapeutic.

The effect of thoracic epidural nerve block with dezocine and ropivacaine on arterial oxygen saturation and IDO gene expression during pulmonary ventilation in lung resection surgery.

During lung resection surgery, the blood supply to the lungs increases the intrapulmonary shunt and reduces arterial oxygenation in patients. Ventilation anesthesia of a lung may affect oxygenation. The present study aimed to compare intravenous anesthesia with and without thoracic epidural block (dezocine and ropivacaine) on oxygen saturation during lung ventilation in patients undergoing lung resection surgery. For this purpose, this study was performed as a double-blind, randomized clinical trial. Sixty patients who were candidates for lung resection were divided into two intervention groups (thoracic epidural block with dezocine and ropivacaine and intravenous anesthesia) and a control group (placebo thoracic epidural block and intravenous anesthesia). Hemodynamic variables, Aldert score, and possible complications were compared between the two groups before surgery and after recovery. Also, the expression level of the IDO gene was evaluated using the real-time PCR technique. SPSS, t-test, Mann-Whitney U, Chi-square, and Fisher performed data analysis and comparison. The results showed that the changes in hemodynamic variables and PaO2, SaO2, and ETCO2 were not statistically significant between the two groups. Aldrete's score at entry and exit of recovery was similar between the two groups. During the recovery period, the percentage of pain or chills in the group under complete intravenous anesthesia was significantly higher. There was no significant difference between the two groups regarding the frequency of nausea and hypotension. Also, the results of IDO gene expression showed that general anesthesia with the thoracic epidural block (dezocine and ropivacaine), which is involved in inducing immunological tolerance and suppressing immune responses, has no significant effect. The stress of performing surgery before surgery can play a role in suppressing the patient's immunity, and anesthesia of the thoracic epidural block (dezocine and ropivacaine) has no significant effect on IDO expression. In general, thoracic epidural block with complete intravenous anesthesia has no significant effect on oxygen saturation in ventilated lungs compared with intravenous anesthesia alone. Nevertheless, this combination significantly reduces postoperative pain and chills.

Impact of COVID-19 on the association between pulse oximetry and arterial oxygenation in patients with acute respiratory distress syndrome

Managing patients with acute respiratory distress syndrome (ARDS) requires frequent changes in mechanical ventilator respiratory settings to optimize arterial oxygenation assessed by arterial oxygen partial pressure (PaO2) and saturation (SaO2). Pulse oxymetry (SpO2) has been suggested as a non-invasive surrogate for arterial oxygenation however its accuracy in COVID-19 patients is unknown. In this study, we aimed to investigate the influence of COVID-19 status on the association between SpO2 and arterial oxygenation. We prospectively included patients with ARDS and compared COVID-19 to non-COVID-19 patients, regarding SpO2 and concomitant arterial oxygenation (SaO2 and PaO2) measurements, and their association. Bias was defined as mean difference between SpO2 and SaO2 measurements. Occult hypoxemia was defined as a SpO2 ≥ 92% while concomitant SaO2 < 88%. Multiple linear regression models were built to account for confounders. We also assessed concordance between positive end-expiratory pressure (PEEP) trial-induced changes in SpO2 and in arterial oxygenation. We included 55 patients, among them 26 (47%) with COVID-19. Overall, SpO2 and SaO2 measurements were correlated (r = 0.70; p < 0.0001), however less so in COVID-19 than in non-COVID-19 patients (r = 0.55, p < 0.0001 vs. r = 0.84, p < 0.0001, p = 0.002 for intergroup comparison). Bias was + 1.1%, greater in COVID-19 than in non-COVID-19 patients (2.0 vs. 0.3%; p = 0.02). In multivariate analysis, bias was associated with COVID-19 status (unstandardized β = 1.77, 95%CI = 0.38–3.15, p = 0.01), ethnic group and ARDS severity. Occult hypoxemia occurred in 5.5% of measurements (7.7% in COVID-19 patients vs. 3.4% in non-COVID-19 patients, p = 0.42). Concordance rate between PEEP trial-induced changes in SpO2 and SaO2 was 84%, however less so in COVID-19 than in non-COVID-19 patients (69% vs. 97%, respectively). Similar results were observed for PaO2 regarding correlations, bias, and concordance with SpO2 changes. In patients with ARDS, SpO2 was associated with arterial oxygenation, but COVID-19 status significantly altered this association.

Effects of remote ischemic postconditioning on HIF-1α and other markers in on-pump cardiac surgery.

There is a lack of data about the effects of remote ischemic postconditioning (RIPostC) on hypoxia-inducible factor-1α (HIF-1α) plasma levels after on-pump cardiac surgery (OPCS). This study aimed to measure the effects of RIPostC on postoperative HIF-1α plasma levels, cardiac markers and arterial oxygenation in patients undergoing OPCS. This single-centre randomized, double blind, controlled trial, enrolled 70 patients (35 control and 35 RIPostC). RIPostC was performed by 3 cycles (5min of ischemia followed by 5min of reperfusion) administered in upper arm immediately after the pump period. The primary outcome was to measure HIF-1α plasma levels: before surgery (T0), and 2h (T1), 8h (T2), 24h (T3), 36h (T4) and 48h (T5) after RIPostC. As secondary endpoint, Troponin T, CK-MB, CPK plasma levels and PaO2/FiO2 ratio were measured. HIF-1α plasma levels were increased at T1-T3 compared to T0 in both groups (P < 0.001). In the RIPostC group HIF-1α increased compared to the control group: differences between means (95% CI) were 0.034 (0.006-0.06) P = 0.019 at T1; 0.041 (0.013-0.069) P = 0.005 at T2; and 0.021 (0.001-0.042) P = 0.045 at T3. PaO2/FiO2 was higher in the RIPostC group than in the control group: at T3, T4 and T5. Moreover, Troponin T, CK-MB and CPK values decreased in the RIPostC group compared to the control group. HIF-1α plasma levels increased in control patients during for at least 36h after OPCS. RIPostC resulted in even higher HIF-1α levels during at least the first 24h and improved arterial oxygenation and cardiac markers.

Novel criteria to classify ARDS severity using a machine learning approach

BackgroundUsually, arterial oxygenation in patients with the acute respiratory distress syndrome (ARDS) improves substantially by increasing the level of positive end-expiratory pressure (PEEP). Herein, we are proposing a novel variable [PaO2/(FiO2xPEEP) or P/FPE] for PEEP ≥ 5 to address Berlin’s definition gap for ARDS severity by using machine learning (ML) approaches.MethodsWe examined P/FPE values delimiting the boundaries of mild, moderate, and severe ARDS. We applied ML to predict ARDS severity after onset over time by comparing current Berlin PaO2/FiO2 criteria with P/FPE under three different scenarios. We extracted clinical data from the first 3 ICU days after ARDS onset (N = 2738, 1519, and 1341 patients, respectively) from MIMIC-III database according to Berlin criteria for severity. Then, we used the multicenter database eICU (2014–2015) and extracted data from the first 3 ICU days after ARDS onset (N = 5153, 2981, and 2326 patients, respectively). Disease progression in each database was tracked along those 3 ICU days to assess ARDS severity. Three robust ML classification techniques were implemented using Python 3.7 (LightGBM, RF, and XGBoost) for predicting ARDS severity over time.ResultsP/FPE ratio outperformed PaO2/FiO2 ratio in all ML models for predicting ARDS severity after onset over time (MIMIC-III: AUC 0.711–0.788 and CORR 0.376–0.566; eICU: AUC 0.734–0.873 and CORR 0.511–0.745).ConclusionsThe novel P/FPE ratio to assess ARDS severity after onset over time is markedly better than current PaO2/FiO2 criteria. The use of P/FPE could help to manage ARDS patients with a more precise therapeutic regimen for each ARDS category of severity.

Positive end-expiratory pressure increases arterial oxygenation in elderly patients undergoing urological surgery using laryngeal mask airway in lithotomy position.

Elderly patients undergoing urological surgery in the lithotomy position may be vulnerable to perioperative hypoxemia. Positive end-expiratory pressure (PEEP) can improve arterial oxygenation. Although laryngeal mask airway (LMA) is widely utilized in urological surgery, it is not known how PEEP affects arterial oxygenation in these patients. We, therefore, evaluated the effect of PEEP on arterial oxygen partial pressure (PaO2) in elderly patients using LMA during urological surgery in the lithotomy position. Patients randomly received zero end-expiratory pressure (group Z, n = 34) or PEEP of 7 cmH2O (group P, n = 33). Ventilatory, respiratory, and haemodynamic variables were measured at 5min (T0), 30min (T1), and 60min (T2) after LMA Supreme™ (sLMA) insertion. The primary outcome was the difference of PaO2 at T2 between the two groups. Atelectasis score, the incidence of a significant leak, and complications associated with sLMA insertion were also evaluated. PaO2 at T2 was significantly higher in group P than in group Z (20.0 ± 4.9 vs. 14.7 ± 3.7kPa, P < 0.001). Atelectasis score at T2 was lower in group P than in group Z (5.3 ± 1.7 vs. 8.4 ± 2.3, P < 0.001). However, the incidence of a significant leak and complications associated with LMA insertion did not significantly differ between the two groups. PEEP can improve arterial oxygenation and reduce atelectasis in elderly patients using sLMA during urological surgery in the lithotomy position, suggesting that PEEP may be useful for elderly patients with an increased risk of perioperative hypoxemia when using sLMA.

High‐flow nasal therapy – modelling the mechanism

High‐flow nasal therapy – modelling the mechanism

Hemodynamic and gas exchange effects of inhaled iloprost in patients with COPD and pulmonary hypertension

Studies have shown that vasodilators such as iloprost can be useful for treating pulmonary hypertension (PH). However, in patients with COPD, vasodilators may inhibit hypoxic pulmonary vasoconstriction and impair gas exchange. The efficacy and safety of iloprost inhalation was assessed in 67 patients with PH associated with COPD (COPD-PH), diagnosed by right heart catheterization. Of these, 37 patients had severe PH (mean pulmonary arterial pressure [mPAP] >35 mmHg or mPAP 25–35 mmHg with low cardiac index [<2.0 L⋅min−1⋅m−2]). All patients received a single 20 µg dose of iloprost via a nebulizer (4.4 µg delivered at the mouthpiece). No serious adverse events were reported. Hemodynamic and gas exchange parameters (arterial blood gas and shunt fraction [Qs/Qt]) were measured or calculated at baseline and 10 min after iloprost inhalation. mPAP decreased by 2.1 mmHg (95% CI, −3.3 to −1.0), pulmonary vascular resistance (PVR) decreased by 62.4 dyn⋅s⋅cm−5 (95% CI, −92.9 to −31.8), and cardiac output increased by 0.4 L⋅min−1 (95% CI, 0.2–0.5). There was a more significant decline in PVR in patients with severe COPD-PH than in those with nonsevere COPD-PH. Hypoxemia and intrapulmonary shunt were more extreme in patients with severe COPD-PH. However, there were no significant differences in arterial blood gas and Qs/Qt between patients with nonsevere and severe forms of COPD-PH. In conclusion, iloprost improved pulmonary hemodynamics without detrimental effects on arterial oxygenation in patients with COPD-PH, even in those with severe PH. These findings suggest that the short-term use of iloprost in patients with COPD-PH is effective and well tolerated.

Effects of pleasant olfactory mental imagery on the arterial oxygenation in patients with open heart surgery: A randomized controlled trial

Background and purposeArterial hypoxemia is one of the most common respiratory complications following cardiac surgery. This study was intended to examine the effects of pleasant olfactory mental imagery on postoperative hypoxemia in patients undergoing open heart surgery. Materials and methodsThis is a randomized controlled clinical trial. The sample consisted of 80 patients who were randomly assigned to either practice olfactory mental imagery (experimental group) or receive routine care (control group). A card with the image of roses was given to patients and they were asked to look at the image, visualize the scent of roses in the mind, and then sniff as much as possible, hold their breath for 2 s and eventually exhale slowly through the nose. This procedure was consecutively repeated five times. After a fifteen-minute break, patients proceeded to practice olfactory mental imagery with other fruit images. The experimental group executed the olfactory mental imagery for two hours in the morning and two hours in the afternoon on postoperative days 1 and 2. ResultsNo statistically significant differences were observed between the experimental and control groups regarding sociodemographic characteristics, medical and surgical information. This study also demonstrated that the mean Spao2 was significantly higher in the experimental group (97.400 ± 1.70) than the control group (96.465 ± 1.70) (p = 0.015). ConclusionThe results of this study suggest that olfactory mental imagery can improve arterial oxygenation in patients with cardiac surgery.

Comparison of tidal volume and deep breath preoxygenation techniquesundergoing coronary artery bypass graft surgery: effects of hemodynamicresponse and arterial oxygenation

Background/aim: Different techniques exist for the preoxygenation of patients that will be operated on under general anesthesia. Preoxygenation with the deep breath (DB) method may affect cardiovascular stability, which is crucial for coronary artery bypass graft (CABG) patients. In this study, we aimed to compare the effects of the 3 min TVB preoxygenation technique and 1 min 8DBs technique on hemodynamic response and arterial oxygenation in patients with normal ejection fraction that were scheduled for elective CABG surgery. Materials and methods: Forty patients classified as ASA II?III and scheduled for elective CABG surgery were randomly assigned to TVB/3 min or 8DBs/1 min for preoxygenation. Cardiovascular variables, i.e. heart rate, mean arterial pressure, central venous pressure, cardiac index, systemic vascular resistance index, and stroke volume index, and arterial blood gas samples were analyzed before and after preoxygenation and at the end of the apneic period before intubation. Results: The preoxygenation methods affected the hemodynamic response similarly. PaO2 increased significantly with 8DBs compared to the TVB at the end of preoxygenation but was similar between the groups at the end of the apneic period (respectively, P: 0.03; P: 0.15). PaCO2 changes were similar between the groups. Conclusion: In patients with normal ejection fraction scheduled for CABG, 8DBs can be an alternative to TVB preoxygenation. Our results should be compared with those of other studies.

Optimizing the circulation in the prone patient.

Prone positioning is recommended as a rescue therapy to improve arterial oxygenation in patients with severe acute respiratory distress syndrome (ARDS). In this review, we summarize the macro and the microcirculatory effects of prone positioning and emphasize which hemodynamic variables can be monitored when this therapy is applied. Early and prolonged prone positioning sessions significantly decrease the mortality of patients with severe ARDS. Prone positioning increases cardiac preload and decreases right ventricular afterload in patients with ARDS under protective ventilation and maximal lung recruitment. This results in an increase in cardiac output only in patients with preload reserve, emphasizing the important role of preload in the hemodynamic effects of prone positioning. Prone positioning might also exert some effects on regional and/or local blood flows, which mainly result from the increase in intra-abdominal pressure. Because prone positioning does not produce a significant increase in intra-abdominal pressure, it does not exert deleterious effects on the microcirculation of intra-abdominal organs. Prone positioning generally exerts beneficial macrocirculatory effects, which can result in increased cardiac output in patients with preload reserve without negatively altering regional circulations.

Effect of recruitment maneuver on arterial oxygenation in patients undergoing robot-assisted laparoscopic prostatectomy with intraoperative 15 cmH2O positive end expiratory pressure.

BackgroundThis randomized, controlled study was designed to compare the effects of recruitment maneuvers (RMs) with a 15 cmH2O positive end-expiratory pressure (PEEP) on the systemic oxygenation and lung compliance of patients with healthy lungs following robot-assisted laparoscopic prostatectomy (RALP).MethodsSixty patients undergoing a RALP with an intraoperative 15 cmH2O PEEP were randomly allocated to an RM or a Control group. The patients in the RM group received a single RM through the application of a continuous positive airway pressure of 40 cmH2O for 40 s 15 min after being placed in the Trendelenburg position. The arterial oxygen tension (PaO2, primary endpoint) and the pulmonary dynamic and static compliances (secondary endpoints) were measured 10 min after the anesthetic induction (T1), 10 min after establishment of the pneumoperitoneum (T2), 10 min after establishment of the Trendelenburg position (T3), 10 min after the RM (T4), 60 min after the RM (T5), and 10 min after deflation of the pneumoperitoneum in the supine position (T6).ResultsThe intergroup comparisons of the PaO2 showed significantly higher values in the RM group than in the Control group at T4 and T5 (193 ± 35 mmHg vs. 219 ± 33 mmHg, P = 0.015, 188 ± 41 mmHg vs. 214 ± 42 mmHg, P = 0.005, respectively). However, the PaO2 at T6 was similar in the two groups (211 ± 39 mmHg vs. 224 ± 41 mmHg, P = 0.442). Moreover, there were no statistical differences between the groups in the dynamic and static compliances of the lungs at any time point.ConclusionsThe arterial oxygenation of the patients with a healthy lung function who had undergone a RALP with intraoperative 15 cmH2O PEEP was improved by a single RM. However, this benefit did not last long, and it did not lead to an amelioration of the lung mechanics.

Prone Positioning in Cardiac Surgery: For Many, But Not for Everyone

Prone positioning is a therapeutic maneuver to improve arterial oxygenation in patients with acute lung injury that is not implemented in most centers performing adult cardiac surgery. The aim of this study was to review our experience with prone positioning to assess the effects of this maneuver in patients with postoperative acute respiratory failure. From 2010-2014, 127 adult patients with postoperative acute respiratory failure were treated with prone positioning in addition to specific therapy. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors associated with in-hospital mortality. In-hospital mortality was 22.8% (n = 29). No significant differences were observed in preoperative risk factors between patients who survived (S) and those who died (D), except for age (62.7 ± 11.2 vs 70.2 ± 11.3; P = 0.007-at multivariate analysis P = 0.03, odds ratio [OR] = 1.1/year). Preproning values of PaO2/FiO2 were significantly different between groups (D vs S: 115 ± 46 vs 150 ± 56; P = 0.006), but only preproning FiO2 remained highly significant at multivariate analysis (D vs S: 0.82 ± 0.18 vs 0.67 ± 0.16; P = 0.001, OR = 1.07; with FiO2 > 0.75 vs < 75, OR = 19.6). D showed a higher improvement of PaO2/FiO2 immediately after prone positioning (207 ± 100 vs 219 ± 90, P = 0.56; within-group analysis between preproning and 1 hour after proning: S-P = 0.49, D-P = 0.019; at 12 hours: 286 ± 123 vs 240 ± 120, P = 0.06; within-group analysis between 1 hour and 12 hours after proning: S-P = 0.15; D-P = 0.17; between groups-P = 0.05). D had higher peak WBC count (26 ± 9.8 vs 17.7 ± 5.9×103/mL; P = 0.0001) and a higher rate of low output syndrome (15 vs 9 patients-51.7% vs 9.2%; P = 0.0001). At multivariate analysis, white blood cell count: P = 0.005, OR = 1.11/103 white blood cell; low output syndrome: P = 0.0002, OR = 20.5. In conclusion, our results show that prone positioning, if performed early, is a safe and effective adjunct measure for patients with postoperative acute hypoxemic respiratory failure of noncardiogenic origin.

Prone positioning in cardiac surgery: for many, but not for everyone

Prone positioning is a therapeutic maneuver to improve arterial oxygenation in patients with acute lung injury that is not implemented in most centers performing adult cardiac surgery. The aim of this study was to review our experience with prone positioning, which has become increasingly used at our center over the last years.

Recumbent deoxygenation in mild/moderate liver cirrhosis: the “Clinodeoxia”. The ortho-clino paradigm

While the effects of postural change on arterial oxygenation have been well documented in normal subjects, and attributed to the relationship of closing volume (CV) to the tidal volume, in liver cirrhosis such postural changes have been evaluated mainly in a rare, peculiar clinical end-stage condition which is characterized by increased dyspnea shifting from supine to upright position ("platypnea"). The latter is associated with worsening of PaO2 ("orthodeoxia"). We evaluated the effects of postural changes on arterial oxygenation in patients affected by mild/moderate liver cirrhosis. We performed pulmonary function tests and arterial blood gas evaluation in sitting and supine positions in 22 patients with mild/moderate liver cirrhosis, biopsy-proved, and 22 matched non-smokers control subjects. Recumbency elicited a decrease of PaO2 (Δ(sup-sit)PaO2) in 19 out of 22 controls and in all but one cirrhotics. The magnitude of this postural change was significantly (p=0.04) greater in cirrhotics (9.6±5.3%) compared to controls (6.7±3.7%). In the subset of cirrhotics younger than 60yrs and with PaO2 greater than 80mmHg in sitting position, the Δ(sup-sit)PaO2 in recumbency further increased to 12±5.8%, significantly (p=0.014) greater than in same subgroup of controls (7.1±3.8%). In mild/moderate liver cirrhosis the postural variations in PaO2 follow the normal trends, but are of greater magnitude probably as a consequence of hypoventilated units of lung for postural and disease-linked tidal airway closure, resulting in more pronounced recumbent hypoxemia ("clinodeoxia").

Erratum to: Improvement in oxygenation by prone position and nitric oxide in patients with acute respiratory distress syndrome

Inhaled nitric oxide (NO) and prone position improve arterial oxygenation in patients with the acute respiratory distress syndrome. This study was undertaken to assess the combined effects of NO and prone position in these patients.Prospective clinical study.General intensive care service in a community teaching hospital.14 mechanically ventilated adult patients with the acute respiratory distress syndrome (mean lung injury score 3.23+/-0.27).We measured hemodynamic and oxygenation parameters in the supine position and 2 h later in the prone position, before and during inhalation of 10 ppm NO. A positive response in oxygenation was defined as a > or =20% increment in the arterial oxygen tension/fractional inspired oxygen ratio (PaO2/FIO2). In the prone position PaO2/FIO2 increased significantly (from 110+/-55 to 161+/-89 mm Hg, p<0.01) and venous admixture decreased (from 38+/-12 to 30+/-7%, p<0.01) compared to the supine position. Ten of the 14 patients were responders in the prone position. In the supine position, inhalation of NO improved oxygenation to a lesser extent, increasing PaO2/FIO2 to 134+/-64 mm Hg (p<0.01) and decreasing venous admixture to 35+/-12%, (p<0.01). Five of the 14 patients responded to NO inhalation supine and 8 of 14 responded prone (p = 0.22). The combination of NO therapy and prone positioning was additive in increasing PaO2/FIO2 (197+/-92 mm Hg) and decreasing venous admixture (27+/-8%) (p<0.01). This combination also showed a positive oxygenation response on compared to the supine value without NO in 13 of the 14 patients (93 %). NO-induced changes in PaO2/FIO2 were correlated to changes in pulmonary vascular resistance only in the prone position.In patients with the acute respiratory distress syndrome, the combination of NO and prone position is a valuable adjunct to mechanical ventilation.

A preemptive alveolar recruitment strategy before one-lung ventilation improves arterial oxygenation in patients undergoing thoracic surgery: a prospective randomised study

Arterial hypoxaemia remains a problem during one-lung ventilation (OLV). We determined whether a preemptive alveolar recruitment strategy (ARS) before OLV improves arterial oxygenation during OLV in patients undergoing thoracic surgery. Forty-two patients were allocated randomly to receive either a tidal volume of 10 ml kg(-1) (group C) or ARS of 10 manual breaths with a peak inspiratory pressure of 40 cmH2O followed by positive end-expiratory pressure (PEEP) of 15 cmH2O until OLV commenced (group P). The dependent lung was ventilated with a tidal volume of 6 ml kg(-1) and PEEP of 5 cmH2O during OLV in both groups. Arterial blood gas data were recorded before ARS (baseline), after 15, 30, 45, 60 min of OLV, and at the end of OLV. Baseline paO2 in group P was similar to that in group C (29.9 +/- 3.9 vs. 30.0 +/- 3.5 kPa). However, paO2 was significantly higher in group P than in group C during OLV (38.9 +/- 15.0 vs. 28.8 +/- 14.4 kPa after 15 min of OLV, 39.6 +/- 13.3 vs. 31.2 +/- 13.9 kPa after 60 min of OLV and 45.5 +/- 12.1 vs. 34.3 +/- 12.0 kPa before an air leakage test, P < 0.05). The alveolar-arterial oxygen gradient was significantly lower in group P than in group C after 15 min of OLV and at the end of OLV (46.1 +/- 14.4 vs. 55.9 +/- 14.7, 39.7 +/- 12.4 vs. 50.7 +/- 12.3 kPa, P < 0.05). Preemptive ARS before OLV is effective in improving arterial oxygenation during the entire period of OLV.

Effects of Ventilatory Mode During One-Lung Ventilation on Intraoperative and Postoperative Arterial Oxygenation in Thoracic Surgery

The purpose of this study was to investigate the relationship between the ventilatory mode used during one-lung ventilation (OLV) and intraoperative and early postoperative arterial oxygenation in patients undergoing thoracic surgery. A prospective, randomized clinical trial. A tertiary care university hospital single institution. One hundred ten patients scheduled for thoracic surgery with at least 1 hour of OLV. Patients were prospectively randomized into 2 groups depending on the ventilatory mode used during OLV: volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV). In VCV, the authors used a tidal volume (Vt) of 8 mL/kg and in the PCV group an inspiratory pressure to provide a tidal volume of 8 mL/kg. Airway pressures and arterial blood gases were obtained at 20, 30, and 40 minutes after OLV. The authors recorded the ratio of arterial oxygen tension to inspired oxygen fraction (PaO(2)/F(I)O(2)) at 4 hours (RU1) and 24 hours (RU2) after surgery. During OLV, there were no differences in arterial oxygenation, airway plateau pressure, and mean pressure between groups, although peak pressure was higher in the VCV group (p < 0.01). The PaO(2)/F(I)O(2) ratio at RU1 was 312.6 +/- 106 in the VCV group and 322.1 +/- 104. In the PCV group at RU2, it was 402.4 +/- 105 and 389.6 +/- 114, respectively, and there were no significant differences between the groups. In patients undergoing thoracic surgery, the use of PCV compared with VCV during OLV with the same Vt of 8 mL/kg does not affect arterial oxygenation during OLV or early postoperative oxygenation.

Effects of Alveolar Recruitment on Arterial Oxygenation in Patients After Cardiac Surgery: A Prospective, Randomized, Controlled Clinical Trial

Pulmonary atelectasis and hypoxemia remain considerable problems after cardiac surgery. The objective of this study was to determine the efficacy of consecutive vital capacity maneuvers (C-VCMs) to improve oxygenation in patients after cardiac surgery. Randomized, controlled clinical trial. Tertiary referral teaching center. Ninety-five patients requiring elective cardiac surgery with cardiopulmonary bypass (CPB). Patients were randomly allocated to either C-VCM or control groups. In the C-VCM group, lung inflation at pressure of 35 cmH(2)O was sustained for 15 seconds before separation from CPB and at 30 cmH(2)O for 5 seconds after admission to the intensive care unit (ICU). The primary outcome was the ratio of arterial oxygen tension to inspired oxygen fraction measured at the following predetermined time intervals: after induction of anesthesia, 15 minutes after separation from CPB, after admission to the ICU, after 3 hours of positive-pressure ventilation, after extubation, and before ICU discharge. C-VCM resulted in better arterial oxygenation extending from the immediate postoperative period to approximately 24 hours after surgery at the time of ICU discharge. There were no significant adverse events related to C-VCM application. C-VCM is an effective method to reduce hypoxemia associated with the formation of atelectasis after cardiac surgery with CPB.

Hemodynamic features and impaired arterial oxygenation in patients with portopulmonary hypertension

Portopulmonary hypertension (P-PHT) is sporadically found in cirrhosis patients who have portal hypertension. We retrospectively investigated the clinical features of six patients with P-PHT and compared their hemodynamics and arterial oxygenation with data from 60 cirrhosis patients without pulmonary hypertension (non-PHT cirrhosis) admitted to our department. The mean pulmonary artery pressure and pulmonary vascular resistance index of P-PHT patients ranged from 25 to 57mmHg and from 399 to 1405dynesscm(-5)m(-2), respectively, and their arterial oxygenation was impaired. The systemic vascular resistance and cardiac index of P-PHT patients were similar level to those of patients with non-PHT cirrhosis. We found 10 patients with non-PHT cirrhosis in whom pulmonary vascular resistance exceeded the critical level for pre-capillary pulmonary hypertension (120dynesscm(-5)). These patients showed a distinctive hemodynamic profile, including a decrease of cardiac output due to contraction of the plasma volume and resultant elevation of systemic vascular resistance. However, the decrease of cardiac output contributed little to the elevation of pulmonary vascular resistance. Our findings suggested that certain factor(s) were acting to raise pulmonary vascular tone in these patients, which might cause chronic damage to the pulmonary vascular bed, leading to the onset of pulmonary hypertension.