An e-survey study on the practice of recruitment manoeuvres in dogs among board-certified veterinary anaesthesia and analgesia specialists.

BACKGROUND Recruitment maneuvers (RMs) are used to reduce pulmonary atelectasis in patients under general anesthesia, but they can lead to a decrease in cerebral hemodynamics. MATERIAL AND METHODS Thirty patients undergoing carotid endarterectomy were randomized to a manual sustained inflation (SI) group or a stepwise increase in PEEP (IP) group. During both RMs, the peak airway pressure (Ppeak) was maintained at 30 cmH₂O for 30 s. Electrical impedance tomography was used to evaluate pulmonary aeration changes. Mean velocity of blood flow in the middle cerebral artery (Vm) and cerebral oxygen saturation (rScO₂) was monitored intraoperatively. RESULTS IP improved lung aeration better at Ppeak=30 cmH₂O than SI (58.2±8.4% vs 46.0±8.3%, P=0.001) and this persisted until the end of surgery. Dorsal (dependent) ventilation 30 min after extubation in the SI group was lower than that before surgery (7.7±2.6% vs 9.9±3.8%, P=0.003). Vm and rScO₂ returned to baseline immediately after RM in the SI group, while it remained below baseline in the IP group (42.5±12.6 vs 50.9±18.8 cm/s, P<0.001 and 68.1±3.5% vs 70.6±3.7%, P=0.001). Heart rate declined significantly during RM only in the SI group (55.9±6.6 vs 52.2±6.9 bpm, P=0.008). CONCLUSIONS Compared with SI, IP performed better in improving lung aeration, with greater hemodynamic stability. IP resulted in slower recovery of cerebral blood flow and oxygenation.

Effects of sustained inflation (SI) and pressure- controlled ventilation (PCV) on respiratory mechanics, early central drive, and hemodynamics in patients with acute respiratory distress syndrome (ARDS) were investigated and compared. A retrospective analysis of 26 patients with ARDS, who were admitted to the Yiwu Central Hospital from March 2015 to March 2016, was performed. According to the ventilation method adopted by the patients with ARDS, 13 patients who received SI treatment were included in the SI group and 13 patients who received PCV treatment were included in the PCV group. The condition of central drive of the patients in the two groups was recorded and calculated continuously before and after recruitment maneuver (RM), the changes of each indicator of the respiratory function and hemodynamics were recorded and calculated before and after RM at 1, 10, 20 and 30 min. The differences were not statistically significant when comparing PIP, Pplate and Crs in patients in the SI group and the PCV group before RM with those after RM at 1, 10, 20 and 30 min (P>0.05), the differences were not statistically significant when comparing heart rate and mean arterial pressure in patients in the SI group and the PCV group before RM with those after RM at 1, 10, 20 and 30 min (P>0.05). Ηowever, central venous pressure in patients in the SI group after RM at 10 and 20 min was significantly higher than that in the PCV group, and the differences were statistically significant (P<0.05). VT/RMS, VE/RMS and ΔPdi/RMS in the SI group and the PCV group after RM were significantly higher than those before RM, and the differences were statistically significant (P<0.05). There was little difference in the effect between SI and PCV on respiratory mechanics, early central drive and hemodynamics in patients with ARDS, and both mechanical ventilation methods enhanced the effect of central-mechanical-ventilation coupling after RM. Therefore, the two mechanical ventilation methods, SI and PCV, were equally available for patients with ARDS.

Background and Objectives: The bronchoscopic microsample (BMS) probe allows direct epithelial lining fluid (ELF) level measurement without saline lavage. We investigated whether cytokine levels in ELF from a BMS differed from those obtained by bronchoalveolar lavage (BAL) in stable and acute lung disease. Methods: In a single-centre, prospective observational cohort study of 45 patients, a sequential BMS probe procedure and BAL were performed on patients with stable chronic obstructive lung disease, interstitial lung disease, acute lung injury (ALI), burns-related inhalational injury or controls. ELF samples were assayed for IL-1β, IL-6, IL-8, TNF-α and G-CSF. Results: Both bronchoscopic microsampling and BAL showed significantly higher cytokine levels in the ELF from patients with ALI and burns-related inhalational injury than from those with chronic stable lung disease. The BMS method detected cytokine levels approximately 20- to 80-fold higher than the corresponding BAL (uncorrected for dilution). The ratio of BMS and BAL cytokine levels was as follows: the ratio for IL-1β [mean 55, 95% confidence interval (CI) 34-88] was higher than that for IL-6 (mean 16, 95% CI 10-23, p = 0.015) and IL-8 (mean 13, 95% CI -5 to 36, p = 0.03). The ratio for G-CSF (mean 43, 95% CI 24-75) was higher than that for IL-6 (mean 16, 95% CI 10-23, p = 0.008). Conclusions: The BMS probe safely collects ELF with higher equivalent inflammatory cytokine concentrations than via BAL from patients with both acute and chronic lung disease and can be an alternative to saline BAL. Variations in cytokine concentrations between BMS and BAL and sampling-site differences warrant further study.

The role of recruitment maneuvers in mechanical ventilation for patients with the acute respiratory distress syndrome and acute lung injury remains uncertain in part due to a lack of data on the effects of specific recruitment maneuvers on lung injury severity. The primary objective of this study was to determine the effect of one type of recruitment maneuver--sustained inflation--on alveolar epithelial and lung endothelial injury in experimental acute lung injury. Randomized experimental study. Academic research laboratory. Forty-nine Sprague-Dawley rats. Lung injury was induced in anesthetized, ventilated rats by instillation of acid (pH 1.5) into the airspaces. Rats were ventilated with a tidal volume of 6 mL/kg and a positive end-expiratory pressure of 5 cm H(2)O with or without a sustained inflation recruitment maneuver repeated every 30 mins. Each recruitment maneuver consisted of two 30-sec inflations to total lung capacity (30 cm H(2)O) 1 min apart. The use of recruitment maneuvers significantly improved oxygenation, compliance, end-expiratory lung volume, functional residual capacity, and deadspace fraction. Recruitment maneuvers reduced extravascular lung water and lung endothelial injury as measured by protein permeability (217 +/- 28 vs. 314 +/- 70 extravascular plasma equivalents [microL], p < .05). However, recruitment maneuvers did not prevent alveolar epithelial injury. Epithelial permeability and bronchoalveolar lavage RTI40 levels, a marker of type I cell injury, were similar with or without recruitment maneuvers. Recruitment maneuvers decreased epithelial fluid transport, a functional marker of epithelial injury. Recruitment maneuvers did not reduce markers of airspace inflammation. Sustained inflation recruitment maneuvers improve respiratory mechanics and oxygenation and may protect the lung endothelium but do not reduce alveolar epithelial injury. Because of the differential effects of recruitment maneuvers on the lung endothelium and alveolar epithelium, the net effect in clinical acute lung injury may not be beneficial. Additional clinical studies will be needed to assess the net impact of recruitment maneuvers in patients with acute lung injury.

Objective To observe the effects of recruitment maneuver (RM) and tidal volume with different amount of gas after RM ventilation on lung diastole function in rats with acute lung injury (ALI). Method ALI rat models were induced by intravenous infusion of lipopolysaccharide (LPS) in dose of 6 mg/kg. Twenty-five rats were randomly(random number) divided into control group ( n = 5), ALI group ( n = 5), low tidal volume group (LV group,VT= 6 mL/kg, n = 5), sustained inflation (SI) with low tidal volume (SI+ LV group, VT=6 mL/kg, n = 5), and SI with moderate tidal volume group (SI+ MV group, VT= 12 mL/kg, n = 5). The RM carried out by using SI with airway pressure 30 cmH-2O for 30 seconds, and the positive end-expiratory pressure (PEEP)was set at 5 cmH2O. Lung tissue was taken after mechanical ventilation for 5 hours. The mean arterial pressure (MAP) was monitored throughout the entire course of experiment. Endothelin-1 ( ET-1 ), endothelial nitricoxide synthase (eNOS), and acetylcholine-(Ach-) induced endothelium-dependent relaxation response of isolated pulmonary artery rings were investigated after mechanical ventilation for 5 hours. Results The LPS increased the ET-1 level in lung tissue, decreased the level of eNOS in lung tissue, and impaired the Ach-induced endothelium-dependent relaxation response in pulmonary vassals, without obvious influence on systemic hemodynamics. SI + LV significantly reduced LPS-induced elevation of ET-1 level, and increased the level of eNOS, and significantly lessened endothelial dysfunction and ameliorated dysfunction od endothelium-dependent relaxation in pulmonary vas sals. Conclusions RM with high tidal volume or lowtidal volume ventilation could improve the lung vascular endothelial function of rats with acute lung injury, and RM with low tidal volume ventilation could lessen more the injury of lung vascular endothelial diastole function in rats with acute lung injury. Key words: Acute lung injury; Recruitment maneuver; Low tidal volume; Lung vascular endothelium; Pulmonary artery diastole

At birth, infants' lungs are fluid-filled. For newborns to have a successful transition, this fluid must be replaced by air to enable gas exchange. Some infants are judged to have inadequate breathing at birth and are resuscitated with positive pressure ventilation (PPV). Giving a sustained lung inflation (SLI) at the start of PPV may help clear lung fluid and establish gas volume within the lungs. This is a review update; the last version was published in 2020. To assess the benefits and harms of an initial SLI (> 1 second duration) versus standard inflations (≤ 1 second) in newborn infants receiving resuscitation with intermittent PPV. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via PubMed, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), and two trial registries on 8 April 2024. We checked the reference lists of studies and other related papers. We included randomised controlled trials (RCTs) and quasi-RCTs comparing initial SLI versus standard inflations given to infants receiving resuscitation with PPV at birth. Our critical outcomes were: death in the delivery room; death during hospitalisation. Other clinically relevant outcomes were: rate of mechanical ventilation; chronic lung disease, any grade; chronic lung disease, moderate to severe; pneumothorax during hospitalisation; intraventricular haemorrhage grade 3 or 4. We used the Cochrane risk of bias tool 1.0. We conducted meta-analyses using fixed-effect models to calculate risk ratios (RR) and 95% confidence intervals (CI). We summarised the certainty of the evidence according to GRADE methods. Fourteen trials enrolling 1766 infants met our inclusion criteria. The studies were conducted on five continents, and published between 2005 and 2024. Investigators in 12 trials (1722 infants) administered SLI with no chest compressions; 10 studies reported that peak inspiratory pressure (PIP) was sustained for 15 seconds. Levels of PIP ranged from 20 to 30 cmH₂O. Investigators in seven studies provided additional SLIs in cases of poor response. We downgraded the overall certainty of evidence for all outcomes because of limitations in study design (e.g. selection bias due to lack of allocation concealment and performance bias due to unblinded intervention), and serious imprecision of results, with wide confidence intervals and few events. One trial is ongoing. For each outcome, we downgraded the overall certainty of evidence because of limitations in study design and imprecision. Compared with intermittent ventilation, SLI with no chest compression may result in little to no difference in: • death in the delivery room (RR 1.72, 95% CI 0.82 to 3.63; I² = 0%; 6 studies, 639 participants; low-certainty evidence); • death before discharge (RR 0.99, 95% CI 0.81 to 1.21; I² = 37%; 12 studies, 1722 participants; low-certainty evidence); • chronic lung disease, any grade (RR 0.99, 95% CI 0.83 to 1.18; I² = 0%; 4 studies, 735 participants; low-certainty evidence); • moderate to severe chronic lung disease (RR 0.95, 95% CI 0.74 to 1.22; I² = 47%; 6 studies, 727 participants; low-certainty evidence); • pneumothorax during hospitalisation (RR 0.93, 95% CI 0.65 to 1.33; I² = 12%; 11 studies, 1641 participants; low-certainty evidence); • intraventricular haemorrhage grade 3-4 (RR 0.94, 95% CI 0.64 to 1.38; I² = 13%; 8 studies, 855 participants; low-certainty evidence). SLI with no chest compression may reduce the rate of mechanical ventilation (RR 0.90, 95% CI 0.80 to 1.01; I² = 0%; 7 studies, 1174 participants; low-certainty evidence). Compared with intermittent ventilation, sustained inflation without chest compression may result in little to no difference in death in the delivery room and death before discharge. Sustained inflation may reduce the rate of mechanical ventilation, and may result in little to no difference in chronic lung disease, pneumothorax, and severe intraventricular haemorrhage. There is no evidence to support the use of sustained inflation based on evidence from our review. Future studies of SLI for infants receiving respiratory support at birth should provide more detailed monitoring of the procedure, such as measurements of lung volume and presence of apnoea before or during SLI. Future RCTs should aim to enrol infants who are at higher risk of morbidity and mortality, and should stratify participants by gestational age. Researchers should also measure long-term neurodevelopmental outcomes (e.g. Bayley Scales of Infant Development, administered at two years of corrected age). This Cochrane Review had no dedicated funding. Protocol (2004): doi.org/10.1002/14651858.CD004953 Original review (2015): doi.org/10.1002/14651858.CD004953.pub2 Review update (2017): doi.org/10.1002/14651858.CD004953.pub3 Review update (2020): doi.org/10.1002/14651858.CD004953.pub4.

To compare the individual effects of three recruitment maneuvers (RM) in children with congenital heart disease complicated by postoperation acute respiratory distress syndrome (ARDS). A prospective single-blind randomized controlled trial was conducted. Thirty-two children with congenital heart disease complicated with ARDS after open-heart surgery undergoing mechanical ventilation were randomized into three groups, to whom three different RM was respectively performed, namely sustained inflation (SI), progressively increased positive end expiratory pressure (IP) and pressure control ventilation (PCV). Blood gas analysis was done every 6 hours, and the lung RM was performed if oxygenation index (OI) ≤ 300 mmHg (1 mmHg = 0.133 kPa). The OI, the dynamic lung compliance (Cdyn), as well as the parameters of hemodynamics before, during and after RM for 15, 30, and 60 minutes were recorded and analyzed before and after RM. During the treatment process, the OI was significantly increased during the process and 15, 30 or 60 minutes after RM compared with that before RM, with no statistical difference among groups (F value was 1.027, 0.403, 0.264, 0.172, 0.159, and P value was 0.367, 0.671, 0.769, 0.843, 0.853). The Cdyn at all time points in each group was also significantly increased, but there was no statistical difference among groups (F value was 0.009, 0.015, 0.206, 0.010, 0.389, and P value was 0.991, 0.985, 0.814, 0.990, 0.683). In the process of RM, the heart rate (HR) and mean arterial pressure (MAP) of the children were lowered compared with those before RM [ HR (bpm): 131.67 ± 9.56 vs. 138.93 ± 5.22 in SI group, 133.27 ± 9.54 vs. 140.33 ± 7.74 in IP group, 137.13 ± 7.39 vs. 142.40 ± 9.18 in PCV group, all P < 0.01; MAP (mmHg): 55.07 ± 4.43 vs. 65.87 ± 4.46 in SI group, 58.82 ± 6.04 vs. 64.02 ± 7.65 in IP group, 57.89 ± 4.71 vs. 65.36 ± 5.37 in PCV group, all P < 0.01], but it recovered immediately. CVP in all three groups was increased during RM [cmH₂O (1 cmH₂O = 0.098 kPa): 11.60 ± 0.99 vs. 5.53 ± 0.74 in SI group, 10.33 ± 1.35 vs. 5.40 ± 0.74 in IP group, 10.20 ± 0.94 vs. 5.80 0.68 in PCV group, all P < 0.01]. There was significant difference in CVP during RM among three groups (F = 7.327, P = 0.002), and CVP in SI group was higher than that of other two groups (both P < 0.05). CVP returned to the former level in 15 minutes after RM in IP and PCV groups, and recovered in 30 minutes in SI group. All of the RM methods can effectively improve oxygenation and pulmonary compliance of the children with complication of ARDS, and they complement the inadequacy of lung protective ventilation. PCV and IP are more effective than SI in the uniform re-expansion of alveoli after RM and recovery of hemodynamics.

Patients with chronic lung disease (CLD) have frequent episodes of spontaneous desaturations. Utilizing computerized pulse oximetry (CPO) we quantified the frequency and severity of spontaneous desaturations in very low birth weight (VLBW) infants with CLD. Thirty-four studies by CPO were performed in intubated infants for 4 hours; 17 patients (birth weight, 550-980 g; postnatal age 28-85 days) had CLD, and 17 (birth weight, 520-980 g; postnatal age, 1-7 days) had acute lung disease. Oxygen saturation (SaO2) was measured with the Nellcor N-200 oximeter, its serial output (updated once a second) captured by a computer. Pulse rate, pulse amplitude, and heart rate were also monitored continuously. We measured respiratory system mechanics in 23 patients. Tidal volume (VT), respiratory system compliance (Crs), and resistance (Rrs) were obtained by the PeDS system. Spontaneous desaturation to SaO2 less than 90% occurred for 4.5% of the time in acute patients vs. 27.1% of the time in chronic patients (P less than 0.0001); to SaO2 less than 85%, 0.7% vs. 7.6% of the time in acute vs. chronic patients (P less than 0.002); and to SaO2 less than 80%, 0.4% vs. 2.6% of the time in acute vs. CLD patients (P less than 0.05). Rrs was significantly higher in the ventilated patients with CLD (174 cmH2O/L/s) than in the ventilated patients with acute lung disease (94 cmH2O/L/s, P less than 0.0001). The mean Crs values of the two groups were comparable. Our preliminary data indicate that VLBW infants with CLD receiving assisted ventilation have a greater number of spontaneous desaturation episodes, as compared to patients with acute lung disease.

Recruitment manoeuvres dislodge mucus towards the distal airways in an experimental model of severe pneumonia

At birth, infants' lungs are fluid-filled; this fluid must be replaced by air to allow for effective breathing. Some infants are judged to have inadequate breathing at birth and are resuscitated with positive pressure ventilation (PPV). Giving prolonged (sustained) inflations at the start of PPV may help clear lung fluid and establish gas volume in the lungs. To assess the efficacy of initial sustained (> one second duration) lung inflation compared to standard inflations (≤ one second) in newly born infants receiving resuscitation with intermittent PPV. We searched on PubMed (1966 to 1 February 2015), EMBASE (1980 to 1 February 2015) and the Cochrane Central Register of Controlled Trials (the Cochrane Library 2015). No language restrictions were applied. We searched the abstracts of the Pediatric Academic Societies (PAS) from 2000 to 2014. Randomised controlled trials (RCTs) and quasi-RCTs comparing giving initial sustained lung inflations (SLI) vs. standard inflations to infants receiving resuscitation with PPV at birth. We assessed methodological quality of the included trials using Cochrane Effective Practice and Organisation of Care Group (EPOC) criteria (assessing randomisation, blinding, loss to follow-up and handling of outcome data). We evaluated the treatment effect using a fixed-effect model using risk ratio for categorical data and using mean, standard deviation (SD) and weighted mean difference (WMD) for continuous data. Two trials enrolling 352 infants met our inclusion criteria. There were no differences in the rates of mortality during hospitalisation (RR 1.59, 95% CI 0.81 to 3.10; two trials, 352 infants), intubation in the first three days of life (RR 0.85, 95% CI 0.72 to 1.02; two trials, 352 infants) or chronic lung disease (RR 1.06, 95% CI 0.79 to 1.42; two trials, 349 infants) between infants who received sustained versus standard inflations. The rate of patent ductus arteriosus (reported as need for pharmacological treatment) was higher in the sustained inflation group (RR 1.27, 95% CI 1.03 to 1.56; two trials, 352 infants). At present there is insufficient evidence from clinical trials to determine the efficacy and safety of initial sustained lung inflation for newborn infants resuscitated with PPV. RCTs comparing PPV with and without sustained inflations at neonatal resuscitation are warranted.

To assess the safety and efficacy of sustained inflations (SI) as lung recruitment maneuvers (RMs) in ventilated pediatric intensive care unit (PICU) patients. Observational, prospective data collection. Tertiary-care PICU. Thirty-two consecutive ventilated pediatric patients. An SI (30-40 cmH(2)O for 15-20 s) was performed following a ventilator disconnection, suctioning, hypoxemia, or routinely every 12 h. Physiologic variables were recorded for 6 h after each SI. All other management was at the attending physician's discretion. The change in variables from pre-SI to post-SI (at 2, 10, and 15 min, 1, 2, 3, 4, 5, and 6 h) was compared using mixed models to account for repeated measures in the same patient. 93 RMs were performed on 32 patients (ages 11 days to 14 years). RMs were done after suctioning (58/93, 62%), ventilator disconnect (5/93, 5%), desaturation (8/93, 9%), or routinely (22/93, 24%). Seven of 93 RMs (7.5%) were interrupted for patient agitation, and 2/93 (2.2%) for transient bradycardia. There was no evidence of statistically significant changes in systolic blood pressure, heart rate, or oxygen saturation as measured by pulse oximetry from pre-RM to post-RM, and there were no air leaks. In three patients with altered intracranial compliance, three of eight RM were associated with a spike of intracranial pressure. There was a sustained significant decrease in FiO(2) by 6.1% lasting up to 6 h post-RM. RMs (as SI) are safe in ventilated PICU patients and are associated with a significant reduction in oxygen requirements for the 6 h after the RM.

Objective To investigate and compare the effects of sustained inflation (SI) and pressure controlled ventilation (PCV) on lung recruitment in patients with ARDS, and on hemodynamics and respiratory mechanics of patients. Methods Ten patients with ARDS were included in this randomized clinical trial ( RCT), and SI (40 cmH20, 40s) and PCV (20 cmH20, 2 min) were successively applied to each patient under sedation, non-muscle relaxation state. There was a elution period between two types of recruitment maneuver (RM). Parameters of respiratory mechanics, gas exchange and hemodynamics were measured before RM (T0), 5 min after RM (T2) and one hour after RM (T3). Parameters of respiratory mechanics and hemodynamics were measured during the period of RM (Tl). Results (1) The PaO2 at T2 and T3 increased significantly in comparison with that at To ( P 0.05). There were no significant differences in PaCO2 between two types of RM at each interval (P > 0.05). (2) The cardiac index ( CI) at T1 decreased significantly compared with that at To in two types of RM (P 0.05). There were no differences in MAP and HR at these intervals (P > 0.05). (3) The functional residual capacity (FRC) at T2 and T3 increased significantly in comparison with that at To in two types of RM (P 0.05). There was no difference in plateau pressure (Pplat) at all intervals (P >0.05). Conclusions The oxygenation, FRC, and Cs improve significantly in both SI-RM and PCV-RM, and the effects of two types of RM are similar. The SI-RM and PCV-RM have the similar impact on circulatory system during RM. Key words: Acute lung injury; Acute respiratory distress syndrome; Recruitment maneuvers; Hemodynamics; Lung mechanics

Elevated lung volumes and increased pleural pressures associated with recruitment maneuvers (RM) may adversely affect pulmonary vascular resistance and cardiac filling or performance. We investigated the hemodynamic consequences of three RM techniques after inducing acute lung injury. Prospective, randomized, controlled experimental study. Hospital research laboratory. Thirteen anesthetized, mechanically ventilated pigs. We induced three types of acute lung injury: oleic acid injury (n = 4); ventilator-induced lung injury (n = 4); and pneumonia (n = 5). All three models were designed to initiate a similar severity of oxygenation impairment. RM methods tested were sustained inflation, incremental positive end-expiratory pressure (PEEP) with a limited peak pressure, and pressure-controlled ventilation with increased PEEP and a fixed driving pressure. From a baseline PEEP of 8 cm H2O, all interventions were tested using post-RM PEEP levels of 8, 12, and 16 cm H2O. Cardiac output by thermodilution and systemic and pulmonary artery pressures were measured frequently during the RM and for 15 mins after its completion. During the RM, cardiac output decreased to a greater extent in the pneumonia model (0.49 of baseline cardiac output) than in the oleic acid injury (0.67 of baseline) or ventilator-induced lung injury (0.79 of baseline) models. Cardiac output recovered to the baseline value by 5 mins post-RM in oleic acid injury and ventilator-induced lung injury models. However, cardiac output remained decreased 15 mins post-RM in the pneumonia model. There were no differences in hemodynamic parameters among RM methods in oleic acid injury and ventilator-induced lung injury models. In the pneumonia model, however, cardiac output decreased to a greater extent during the RM with sustained inflation (to 0.33 of baseline cardiac output) compared with pressure-controlled ventilation (to 0.68 of baseline). We conclude that RM transiently but profoundly depressed cardiac output in three models of acute lung injury. The results imply that a lung recruiting maneuver should be used with caution, especially when using sustained inflation in the setting of pneumonia.

BackgroundIn acute respiratory distress syndrome (ARDS), lung recruitment maneuvers can recruit collapsed alveoli in gravity-dependent lung regions, improving the homogeneity of ventilation distribution. This study used electrical impedance tomography to investigate the physiological effects of different recruitment maneuvers for alveolar recruitment in a pig model of ARDS.MethodsARDS was induced in ten healthy male pigs with repeated bronchoalveolar lavage until the ratio of arterial partial pressure of oxygen (PaO2) of fraction of inspired oxygen (P/F) was < 100 mmHg and remained stable for 30 min (TARDS). ARDS pigs underwent three sequential recruitment maneuvers, including sustained inflation, increments of positive end-expiratory pressure (PEEP), and pressure-controlled ventilation (PCV) applied in random order, with 30 mins at a PEEP of 5 cmH2O between maneuvers. Respiratory mechanics, hemodynamics, arterial blood gas, and electrical impedance tomography were recorded at baseline, TARDS, and before and after each recruitment maneuver.ResultsIn all ten pigs, ARDS was successfully induced with a mean 2.8 ± 1.03 L bronchoalveolar lavages. PaO2, P/F, and compliance were significantly improved after recruitment with sustained inflation, increments of PEEP or PCV (all p < 0.05), and there were no significant differences between maneuvers. Global inhomogeneity index significantly decreased after recruitment with sustained inflation, increments of PEEP, or PCV. There were no significant differences in global inhomogeneity before or after recruitment with the different maneuvers. The decrease in global inhomogeneity index (ΔGI) was significantly greater after recruitment with increments of PEEP compared to sustained inflation (p = 0.023), but there was no significant difference in ΔGI between increments of PEEP and PCV or between sustained inflation and PCV.ConclusionSustained inflation, increments of PEEP, and PCV increased oxygenation, and regional and global compliance of the respiratory system, and decreased inhomogeneous gas distribution in ARDS pigs. Increments of PEEP significantly improved inhomogeneity of the lung compared to sustained inflation, while there was no difference between increments of PEEP and PCV or between sustained inflation and PCV.

To measure the dynamics of recruitment and the hemodynamic status during a sustained inflation recruitment maneuver (RM) in order to determine the optimal duration of RM in acute respiratory distress syndrome (ARDS) patients. This prospective study was conducted in a 12-bed intensive care unit (ICU) in a general hospital. A 40cmH(2)O sustained inflation RM maintained for 30s was performed in 50 sedated ventilated patients within the first 24h of meeting ARDS criteria. Invasive arterial pressures, heart rate, and SpO(2) were measured at 10-s intervals during the RM. The volume increase during the RM was measured by integration of the flow required to maintain the pressure at 40cmH(2)O, which provides an estimation of the volume recruited during the RM. Raw data were corrected for gas consumption and fitted with an exponential curve in order to determine an individual time constant for the volume increase. The average volume increase and time constant were 210±198mL and 2.3±1.3s, respectively. Heart rate, diastolic arterial pressure, and SpO(2) did not change during or after the RM. Systolic and mean arterial pressures were maintained at 10s, decreased significantly at 20 and 30s during the RM, and recovered to the pre-RM value 30s after the end of the RM (ANOVA, p<0.01). In early-onset ARDS patients, most of the recruitment occurs during the first 10s of a sustained inflation RM. However, hemodynamic impairment is significant after the tenth second of RM.