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Mechanical ventilation is an important life-saving therapy for general anesthesia and critically ill patients, but ventilation itself may be accompanied with lung injury. Ventilator-induced lung injury (VILI) exacerbates pre-existing lung disease, leading to poor clinical outcomes. Especially for patients undergoing cardiothoracic surgery and receiving one-lung ventilation (OLV), optimizing the parameters of OLV is closely related to their prognosis. It is not clear what is the best strategy to minimize VILI through adjusting ventilation parameters, including tidal volume, positive end expiratory pressure and driving pressure, etc. Different parameters, in combination, are responsible for VILI. Protective ventilation strategies, aiming to reduce postoperative pulmonary complications, have been discussed in many clinical studies and different opinions have been raised. This review addresses the pathogenesis of VILI and focus on the OLV management and better protective OLV strategies during thoracic surgery. [ABSTRACT FROM AUTHOR]

Background: Lung- and diaphragm-protective (LDP) ventilation may prevent diaphragm atrophy and patient self-inflicted lung injury in acute respiratory failure, but feasibility is uncertain. The objectives of this study were to estimate the proportion of patients achieving LDP targets in different modes of ventilation, and to identify predictors of need for extracorporeal carbon dioxide removal (ECCO2R) to achieve LDP targets. Methods: An in silico clinical trial was conducted using a previously published mathematical model of patient–ventilator interaction in a simulated patient population (n = 5000) with clinically relevant physiological characteristics. Ventilation and sedation were titrated according to a pre-defined algorithm in pressure support ventilation (PSV) and proportional assist ventilation (PAV+) modes, with or without adjunctive ECCO2R, and using ECCO2R alone (without ventilation or sedation). Random forest modelling was employed to identify patient-level factors associated with achieving targets. Results: After titration, the proportion of patients achieving targets was lower in PAV+ vs. PSV (37% vs. 43%, odds ratio 0.78, 95% CI 0.73–0.85). Adjunctive ECCO2R substantially increased the probability of achieving targets in both PSV and PAV+ (85% vs. 84%). ECCO2R alone without ventilation or sedation achieved LDP targets in 9%. The main determinants of success without ECCO2R were lung compliance, ventilatory ratio, and strong ion difference. In silico trial results corresponded closely with the results obtained in a clinical trial of the LDP titration algorithm (n = 30). Conclusions: In this in silico trial, many patients required ECCO2R in combination with mechanical ventilation and sedation to achieve LDP targets. ECCO2R increased the probability of achieving LDP targets in patients with intermediate degrees of derangement in elastance and ventilatory ratio. [ABSTRACT FROM AUTHOR]

To determine whether end-expiratory lung volume measured with volumetric capnography (EELVCO2) can individualize positive end-expiratory pressure (PEEP) setting during laparoscopic surgery. We studied patients undergoing laparoscopic surgery subjected to Fowler (F-group; n = 20) or Trendelenburg (T-group; n = 20) positions. EELVCO2 was measured at 0° supine (baseline), during capnoperitoneum (CP) at 0° supine, during CP with Fowler (head up + 20°) or Trendelenburg (head down - 30°) positions and after CP back to 0° supine. PEEP was adjusted to preserve baseline EELVCO2 during and after CP. Baseline EELVCO2 was statistically similar to predicted FRC in both groups. At supine and CP, EELVCO2 decreased from baseline values in F-group [median and IQR 2079 (768) to 1545 (725) mL; p = 0.0001] and in T-group [2164 (789) to 1870 (940) mL; p = 0.0001]. Change in body position maintained EELVCO2 unchanged in both groups. PEEP adjustments from 5.6 (1.1) to 10.0 (2.5) cmH2O in the F-group (p = 0.0001) and from 5.6 (0.9) to 10.0 (2.6) cmH2O in T-group (p = 0.0001) were necessary to reach baseline EELVCO2 values. EELVCO2 increased close to baseline with PEEP in the F-group [1984 (600) mL; p = 0.073] and in the T-group [2175 (703) mL; p = 0.167]. After capnoperitoneum and back to 0° supine, PEEP needed to maintain EELVCO2 was similar to baseline PEEP in F-group [5.9 (1.8) cmH2O; p = 0.179] but slightly higher in the T-group [6.5 (2.2) cmH2O; p = 0.006]. Those new PEEP values gave EELVCO2 similar to baseline in the F-group [2039 (980) mL; p = 0.370] and in the T-group [2150 (715) mL; p = 0.881]. Breath-by-breath noninvasive EELVCO2 detected changes in lung volume induced by capnoperitoneum and body position and was useful to individualize the level of PEEP during laparoscopy.Trial registry: Clinicaltrials.gov NCT03693352. Protocol started 1st October 2018. [ABSTRACT FROM AUTHOR]

Background: Limiting tidal volume (VT), plateau pressure, and driving pressure is essential during the acute respiratory distress syndrome (ARDS), but may be challenging when brain injury coexists due to the risk of hypercapnia. Because lowering dead space enhances CO2 clearance, we conducted a study to determine whether and to what extent replacing heat and moisture exchangers (HME) with heated humidifiers (HH) facilitate safe VT lowering in brain-injured patients with ARDS. Methods: Brain-injured patients (head trauma or spontaneous cerebral hemorrhage with Glasgow Coma Scale at admission < 9) with mild and moderate ARDS received three ventilatory strategies in a sequential order during continuous paralysis: (1) HME with VT to obtain a PaCO2 within 30–35 mmHg (HME1); (2) HH with VT titrated to obtain the same PaCO2 (HH); and (3) HME1 settings resumed (HME2). Arterial blood gases, static and quasi-static respiratory mechanics, alveolar recruitment by multiple pressure–volume curves, intracranial pressure, cerebral perfusion pressure, mean arterial pressure, and mean flow velocity in the middle cerebral artery by transcranial Doppler were recorded. Dead space was measured and partitioned by volumetric capnography. Results: Eighteen brain-injured patients were studied: 7 (39%) had mild and 11 (61%) had moderate ARDS. At inclusion, median [interquartile range] PaO2/FiO2 was 173 [146–213] and median PEEP was 8 cmH2O [5–9]. HH allowed to reduce VT by 120 ml [95% CI: 98–144], VT/kg predicted body weight by 1.8 ml/kg [95% CI: 1.5–2.1], plateau pressure and driving pressure by 3.7 cmH2O [2.9–4.3], without affecting PaCO2, alveolar recruitment, and oxygenation. This was permitted by lower airway (− 84 ml [95% CI: − 79 to − 89]) and total dead space (− 86 ml [95% CI: − 73 to − 98]). Sixteen patients (89%) showed driving pressure equal or lower than 14 cmH2O while on HH, as compared to 7 (39%) and 8 (44%) during HME1 and HME2 (p < 0.001). No changes in mean arterial pressure, cerebral perfusion pressure, intracranial pressure, and middle cerebral artery mean flow velocity were documented during HH. Conclusion: The dead space reduction provided by HH allows to safely reduce VT without modifying PaCO2 nor cerebral perfusion. This permits to provide a wider proportion of brain-injured ARDS patients with less injurious ventilation. [ABSTRACT FROM AUTHOR]

Neuromuscular blocking agents (NMBAs) inhibit patient-initiated active breath and the risk of high tidal volumes and consequent high transpulmonary pressure swings, and minimize patient/ ventilator asynchrony in acute respiratory distress syndrome (ARDS). Minimization of volutrauma and ventilator-induced lung injury (VILI) results in a lower incidence of barotrauma, improved oxygenation and a decrease in circulating proinflammatory markers. Recent randomized clinical trials did not reveal harmful muscular effects during a short course of NMBAs. The use of NMBAs should be considered during the early phase of severe ARDS for patients to facilitate lung protective ventilation or prone positioning only after optimising mechanical ventilation and sedation. The use of NMBAs should be integrated in a global strategy including the reduction of tidal volume, the rational use of PEEP, prone positioning and the use of a ventilatory mode allowing spontaneous ventilation as soon as possible. Partial neuromuscular blockade should be evaluated in future trials. [ABSTRACT FROM AUTHOR]

Background: Prone position (PP) is highly recommended in moderate-to-severe ARDS. However, the optimal duration of PP sessions remains unclear. We searched to evaluate the time required to obtain the maximum physiological effect, and to search for parameters related to patient survival in PP. Methods and results: It was a prospective, monocentric, physiological study. We included in the study all prone-positioned patients in our ICU between June 2016 and January 2018. Pulmonary mechanics, data from volumetric capnography and arterial blood gas were recorded before prone positioning, 2 h after proning, before return to a supine position (SP) and 2 h after return to SP. Dynamic parameters were recorded before proning and every 30 min during the session until 24 h. 103 patients (ARDS 95%) were included performing 231 PP sessions with a mean length of 21.5 ± 5 h per session. They presented a significant increase in pH, static compliance and PaO2/FiO2 with a significant decrease in PaCO2, Pplat, phase 3 slope of the volumetric capnography, PetCO2, VD/VT-phy and ΔP. The beneficial physiological effects continued after 16 h of PP and at least up to 24 h in some patients. The evolution of the respiratory parameters during the first session and also during the pooled sessions did not find any predictor of response to PP, whether before, during or 2 h after the return in SP. Conclusions: PP sessions should be prolonged at least 24 h and be extended in the event that the PaO2/FiO2 ratio at 24 h remains below 150, especially since no criteria can predict which patient will benefit or not from it. Trial registration The trial has been registered on 28 June 2016 in ClinicalTrials.gov (NCT 02816190) (https://clinicaltrials.gov/ct2/show/NCT02816190?term=propocap&rank=1). [ABSTRACT FROM AUTHOR]

Extracorporeal CO2 removal (ECCO2R) is intended to facilitate lung protective ventilation in patients with hypercarbia. The combination of continuous renal replacement therapy (CRRT) and minimal-flow ECCO2R offers a promising concept for patients in need of both. We hypothecated that this system is able to remove enough CO2 to facilitate lung protective ventilation in mechanically ventilated patients. In 11 ventilated patients with acute renal failure who received either pre- or postdilution CRRT, minimal-flow ECCO2R was added to the circuit. During 6 h of combined therapy, CO2 removal and its effect on facilitation of lung-protective mechanical ventilation were assessed. Ventilatory settings were kept in assisted or pressure-controlled mode allowing spontaneous breathing. With minimal-flow ECCO2R significant decreases in minute ventilation, tidal volume and paCO2 were found after one and three but not after 6 h of therapy. Nevertheless, no significant reduction in applied force was found at any time during combined therapy. CO2 removal was 20.73 ml CO2/min and comparable between pre- and postdilution CRRT. Minimal-flow ECCO2R in combination with CRRT is sufficient to reduce surrogates for lung-protective mechanical ventilation but was not sufficient to significantly reduce force applied to the lung. Causative might be the absolute amount of CO2 removal of only about 10% of resting CO2 production in an adult as we found. The benefit of applying minimal flow ECCO2R in an uncontrolled setting of mechanical ventilation might be limited. [ABSTRACT FROM AUTHOR]

Purpose: We compared respiratory mechanics between the positive end-expiratory pressure of minimal respiratory system elastance (PEEPminErs) and three levels of PEEP during low-tidal-volume (6 mL/kg) ventilation in rats.Methods: Twenty-four rats were anesthetized, paralyzed, and mechanically ventilated. Airway pressure (Paw), flow (F), and volume (V) were fitted by a linear single compartment model (LSCM) Paw(t) = Ers × V(t) + Rrs × F(t) + PEEP or a volume- and flow-dependent SCM (VFDSCM) Paw(t) = (E1 + E2 × V(t)) × V(t) + (K1 + K2 × |F(t)|) × F(t) + PEEP, where Ers and Rrs are respiratory system elastance and resistance, respectively; E1 and E2× V are volume-independent and volume-dependent Ers, respectively; and K1 and K2 × F are flow-independent and flow-dependent Rrs, respectively. Animals were ventilated for 1 h at PEEP 0 cmH2O (ZEEP); PEEPminErs; 2 cmH2O above PEEPminErs (PEEPminErs+2); or 4 cmH2O above PEEPminErs (PEEPminErs+4). Alveolar tidal recruitment/derecruitment and overdistension were assessed by the index %E2 = 100 × [(E2 × VT)/(E1 + |E2| × VT)], and alveolar stability by the slope of Ers(t).Results: %E2 varied between 0 and 30% at PEEPminErs in most respiratory cycles. Alveolar Tidal recruitment/derecruitment (%E2 < 0) and overdistension (%E2 > 30) were predominant in the absence of PEEP and in PEEP levels higher than PEEPminErs, respectively. The slope of Ers(t) was different from zero in all groups besides PEEPminErs+4.Conclusions: PEEPminErs presented the best compromise between alveolar tidal recruitment/derecruitment and overdistension, during 1 h of low-VT mechanical ventilation. [ABSTRACT FROM AUTHOR]

Ventilation with large tidal volumes (VT), greater than 10 ml/kg of predicted body weight (PBW), is associated with worse outcomes in critically ill and surgical patients. We hypothesized that the availability of quick reference cards with proposed VT ranges specific to gender and different heights would reduce the intraoperative use of large VT during prolonged abdominal surgery. We compared retrospectively the incidence of median VT used during prolonged (≥4-h-long) abdominal surgery before (“before”) and after (“after”) the quick reference VT cards were made available in all anesthesia machines in operating rooms of a single academic US medical center. We evaluated the effect of the intervention on the primary outcome while adjusting for previously identified risk factors of large VT use: female gender, obesity (body mass index, BMI > 30), and short height (< 165 cm). The frequency of VT > 10 ml/kg PBW was 15.1% in the before group and 4.3% in the after group (p < 0.001). The frequency of large VT used during abdominal surgery was significantly decreased after the intervention even after adjusting for female gender, obesity or short height [adjOR 0.11 (95% CI 0.04–0.30)]. Our quick reference VT cards significantly reduced the frequency of large VT use during abdominal surgery. [ABSTRACT FROM AUTHOR]

Background: Mechanical ventilation with positive end expiratory pressure and low tidal volume, i.e. protective ventilation, is recommended in patients with acute respiratory distress syndrome. However, the effect of protective ventilation on bacterial growth during early pneumonia in non-injured lungs is not extensively studied. The main objectives were to compare two different ventilator settings on Pseudomonas aeruginosa growth in lung tissue and the development of lung injury. Methods: A porcine model of severe pneumonia was used. The protective group ( n = 10) had an end expiratory pressure of 10 cm HO and a tidal volume of 6 ml x kg. The control group ( n = 10) had an end expiratory pressure of 5 cm HO and a tidal volume of 10 ml x kg. 10 colony forming units of Pseudomonas aeruginosa were inoculated intra-tracheally at baseline, after which the experiment continued for 6 h. Two animals from each group received only saline, and served as sham animals. Lung tissue samples from each animal were used for bacterial cultures and wet-to-dry weight ratio measurements. Results: The protective group displayed lower numbers of Pseudomonas aeruginosa ( p < 0.05) in the lung tissue, and a lower wet-to-dry ratio ( p < 0.01) than the control group. The control group deteriorated in arterial oxygen tension/inspired oxygen fraction, whereas the protective group was unchanged ( p < 0.01). Conclusions: In early phase pneumonia, protective ventilation with lower tidal volume and higher end expiratory pressure has the potential to reduce the pulmonary bacterial burden and the development of lung injury. [ABSTRACT FROM AUTHOR]

Background: Pneumoperitoneum during laparoscopic surgery leads to atelectasis and impairment of oxygenation. Positive end-expiratory pressure (PEEP) is supposed to counteract atelectasis. We hypothesized that the derecruiting effects of pneumoperitoneum would deteriorate the intratidal compliance profile in patients undergoing laparoscopic surgery.Methods: In 30 adult patients scheduled for surgery with pneumoperitoneum, respiratory variables were measured during mechanical ventilation. We calculated the dynamic compliance of the respiratory system (C RS) and the intratidal volume-dependent C RS curve using the gliding-SLICE method. The C RS curve was then classified in terms of indicating intratidal recruitment/derecruitment (increasing profile) and overdistension (decreasing profile). During the surgical interventions, the PEEP level was maintained nearly constant at 7 cm H2O. Data are expressed as mean [confidence interval].Results: Baseline C RS was 60 [54-67] mL cm H2O-1. Application of pneumoperitoneum decreased C RS to 40 [37-43] mL cm H2O-1 which partially recovered to 54 [50-59] mL cm H2O-1 (P < 0.001) after removal but remained below the value measured before pneumoperitoneum (P < 0.001). Baseline compliance profiles indicated intratidal recruitment/derecruitment in 48 % patients. After induction of pneumoperitoneum, intratidal recruitment/derecruitment was indicated in 93 % patients (P < 0.01), and after removal intratidal recruitment/derecruitment was indicated in 59 % patients. Compliance profiles showing overdistension were not observed.Conclusions: Analyses of the intratidal compliance profiles reveal that pneumoperitoneum during laparoscopic surgery causes intratidal recruitment/derecruitment which partly persists after its removal. The analysis of the intratidal volume-dependent C RS profiles could be used to guide intraoperative PEEP adjustments during elevated intraabdominal pressure. [ABSTRACT FROM AUTHOR]

Background: Postoperative pulmonary complications (PPCs), which are not uncommon in one-lung ventilation, are among the main causes of postoperative death after lung surgery. Intra-operative ventilation strategies can influence the incidence of PPCs. High tidal volume ( V ) and increased airway pressure may lead to lung injury, while pressure-controlled ventilation and lung-protective strategies with low V may have protective effects against lung injury. In this meta-analysis, we aim to investigate the effects of different ventilation strategies, including pressure-controlled ventilation (PCV), volume-controlled ventilation (VCV), protective ventilation (PV) and conventional ventilation (CV), on PPCs in patients undergoing one-lung ventilation. We hypothesize that both PV with low V and PCV have protective effects against PPCs in one-lung ventilation. Methods: A systematic search (PubMed, EMBASE, the Cochrane Library, and Ovid MEDLINE; in May 2015) was performed for randomized trials comparing PCV with VCV or comparing PV with CV in one-lung ventilation. Methodological quality was evaluated using the Cochrane tool for risk. The primary outcome was the incidence of PPCs. The secondary outcomes included the length of hospital stay, intraoperative plateau airway pressure (P), oxygen index (PaO/FiO) and mean arterial pressure (MAP). Results: In this meta-analysis, 11 studies (436 patients) comparing PCV with VCV and 11 studies (657 patients) comparing PV with CV were included. Compared to CV, PV decreased the incidence of PPCs (OR 0.29; 95 % CI 0.15-0.57; P < 0.01) and intraoperative P (MD −3.75; 95 % CI −5.74 to −1.76; P < 0.01) but had no significant influence on the length of hospital stay or MAP. Compared to VCV, PCV decreased intraoperative P (MD −1.46; 95 % CI −2.54 to −0.34; P = 0.01) but had no significant influence on PPCs, PaO/FiO or MAP. Conclusions: PV with low V was associated with the reduced incidence of PPCs compared to CV. However, PCV and VCV had similar effects on the incidence of PPCs. [ABSTRACT FROM AUTHOR]

Background: Recent studies show that intraoperative protective ventilation is able to reduce postoperative pulmonary complications (PPC).Objectives: This article provides an overview of the definition and ways to predict PPC. We present different factors that lead to ventilator-induced lung injury and explain the concepts of stress and strain as well as driving pressure. Different strategies of mechanical ventilation to avoid PPC are discussed in light of clinical evidence.Materials and Methods: The Medline database was used to selectively search for randomized controlled trials dealing with intraoperative mechanical ventilation and outcomes.Results: Low tidal volumes (VT) and high levels of positive end-expiratory pressure (PEEP), combined with recruitment maneuvers, are able to prevent PPC. Non-obese patients undergoing open abdominal surgery show better lung function with the use of higher PEEP levels and recruitment maneuvers, however such strategy can lead to hemodynamic impairment, while not reducing the incidence of PPC, hospital length of stay and mortality. An increase in the level of PEEP that results in an increase in driving pressure is associated with a greater risk of PPC.Conclusions: The use of intraoperative VT ranging from 6 to 8 ml/kg based on ideal body weight is strongly recommended. Currently, a recommendation regarding the level of PEEP during surgery is not possible. However, a PEEP increase that leads to a rise in driving pressure should be avoided. [ABSTRACT FROM AUTHOR]

The development of a postoperative respiratory insufficiency is typically caused by several factors and include patient-related risks, the extent of the procedure and postoperative complications. Morbidity and mortality rates in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are high. It is important to have consistent strategies for prevention and preoperative conditioning is essential primarily for high-risk patients. Treatment of established postoperative lung failure requires early tracheotomy, protective ventilation (tidal volume 6 ml/kg body weight), elevated positive end expiratory pressure (PEEP, 10-20 mmHO), recurrent bronchoscopy and early patient mobilization. In critical cases an extracorporeal lung assist is considered to be beneficial as a bridge to recovery and for realizing a protective ventilation protocol. Different systems with separate indications are available. The temporary application of a lung assist allows thoracic surgery to be performed safely in patients presenting with insufficient respiratory function. [ABSTRACT FROM AUTHOR]

High tidal volumes have historically been recommended for mechanically ventilated patients during general anesthesia. High tidal volumes have been shown to increase morbidity and mortality in patients suffering from acute respiratory distress syndrome (ARDS). Barriers exist in implementing a tidal volume reduction strategy related to the inherent difficulty in changing one's practice patterns, to the current need to individualize low tidal volume settings only for a specific subgroup of mechanically ventilated patients (i.e., ARDS patients), the difficulty in determining the predicated body weight (requiring the patient's height and a complex formula). Consequently, a protective ventilation strategy is often under-utilized as a therapeutic option, even in ARDS. Recent data supports the generalization of this strategy prophylactically to almost all mechanically ventilated patients beginning immediately following intubation. Using tools to rapidly and reliably determine the predicted body weight (PBW), as well as the use of automated modes of ventilation are some of the potential solutions to facilitate the practice of protective ventilation and to finally ventilate our patients' lungs in a more gentle fashion to help prevent ARDS. [ABSTRACT FROM AUTHOR]

Purpose: During volume-controlled ventilation, part of the volume delivered is compressed into the circuit. To correct for this phenomenon, modern ventilators use compensation algorithms. Humidity and temperature also influence the delivered volume. Methods: In a bench study at a research laboratory in a university hospital, we compared nine ICU ventilators equipped with compensation algorithms, one with a proximal pneumotachograph and one without compensation. Each ventilator was evaluated under normal, obstructive, and restrictive conditions of respiratory mechanics. For each condition, three tidal volumes ( V) were set (300, 500, and 800 ml), with and without an inspiratory pause. The insufflated volume and the volume delivered at the Y-piece were measured independently, without a humidification device, under ambient temperature and pressure and dry gas conditions. We computed the actually delivered V to the lung under body temperature and pressure and saturated water vapour conditions (BTPS). Results: For target V values of 300, 500, and 800 ml, actually delivered V under BTPS conditions ranged from 261 to 396 ml (−13 to +32%), from 437 to 622 ml (−13 to +24%), and from 681 to 953 ml (−15 to +19%), respectively ( p < 0.01). Respiratory system mechanics and application of an inspiratory pause significantly affected actually delivered V. Assuming a set V of 6 ml/kg of predicted body weight, a difference of 1-2 ml/kg with actually delivered V would be commonly observed. Conclusion: The difference between preset V and actually delivered V is clinically meaningful and differs across modern ICU ventilators. [ABSTRACT FROM AUTHOR]

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Copyright of Der Internist is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To evaluate the effects of protective and conventional ventilation with or without positive end-expiratory pressure (PEEP), on systemic tumor necrosis factor-alpha, interleukin-6 levels and pulmonary function during open heart surgery.Design: Prospective, randomized clinical study.Setting: Single university hospital.Patients and Participants: Forty-four patients undergoing elective coronary artery bypass grafting surgery with cardiopulmonary bypass.Interventions: Patients ventilated with (1) protective tidal volumes (6 ml/kg, respiratory rate: 15 breaths/min, PEEP 5 cmH(2)O, n=15) group PV; (2) conventional tidal volumes (10 ml/kg, respiratory rate: 9 breaths/min, PEEP 5 cmH(2)O, n=14) group CV+PEEP and (3) conventional tidal volumes (10 ml/kg, respiratory rate: 9 breaths/min, n=15) without PEEP, group CV+ZEEP. Various pulmonary parameters, systemic TNF-alpha and IL-6 levels were determined throughout the study.Measurements and Results: There were no differences among the groups regarding the systemic TNF- alpha and IL-6 levels. The plateau airway pressures of group PV were lower than those of groups CV+PEEP ( p=0.02) and CV+ZEEP ( p=0.001) after cardiopulmonary bypass. The shunt fraction of group PV was significantly lower than that of group CV+ZEEP 24 h after surgery ( p<0.05). Oxygenation and the alveolar-arterial oxygen difference were better in both PEEP groups than in group CV+ZEEP 24 h after the operation.Conclusions: We could not find any evidence that protective mechanical ventilation prevents some of the adverse effects of cardiopulmonary bypass on the lung, nor systemic cytokine levels, postoperative pulmonary function or length of hospitalization. [ABSTRACT FROM AUTHOR]

Objective. To assess the ability of a heated humidifier to improve CO2 clearance in ARDS patients submitted to protective ventilation. Design. Prospective clinical study. Setting. University hospital intensive care unit. Patients. During a 12-month period, we studied 11 ARDS patients under protective mechanical ventilation with severe hypercapnia. Intervention. When PaCO2 was above 55 mmHg, the heat and moisture exchanger (HME) was removed and patients were ventilated using a heated humidifier (HH) until their recovery or death. The heated humidifier was inserted on the inspiratory limb of the respirator and the inspirated air was saturated to achieve a temperature of 40 °C at the Y connector of ventilator tubing and of 37 °C at the outlet of the endotracheal tube. Measurements and results. Mechanical measurements and blood gas analysis were performed just before removal of the HME, and 30 min after mechanical ventilation using HH. Ventilator parameters were kept constant in the two conditions. Using HH instead of HME, PaCO2 was safely decreased by 11±5 mmHg, without any need to change respiratory rate. No significant difference was noted in intrinsic PEEP or airway plateau pressure. Decrease in PaCO2 after HME removal was strongly correlated with the initial value of PaCO2. Conclusion. Supposing there is an interest in correcting or limiting hypercapnic acidosis in ARDS patients submitted to protective ventilation, HME removal and use of HH appears to be an efficient and safe way of increasing CO2 clearance. [ABSTRACT FROM AUTHOR]

Objective: Evaluation of the impact of low-volume, pressure-limited ventilation on the recovery rate of acute respiratory distress syndrome (ARDS). Design: Prospective observational clinical study with historical control. Setting: University hospital intensive care unit (ICU). Patients: We studied two groups of, respectively, 33 and 37 ARDS patients separated by 15 years (“historical”, June 1978–April 1981, and “recent”, October 1993–June1996). Method: ARDS was defined as the presence of bilateral chest infiltrates and a PaO2/FIO2 ratio of less than 200 mmHg under controlled ventilation regardless of PEEP level. Any cardiac participation was excluded by right heart catheterization in the “historical” group and by echo-Doppler examination in the “recent” group. The origin of ARDS was principally pulmonary (ARDSp) in both groups (26/33 and 29/37, respectively), and secondarily extrapulmonary (ARDSexp) (7/33 and 8/37, respectively). In the “historical” group, normocapnia was the major goal for respiratory support and was achieved in all patients regardless of airway pressure levels. In contrast, end-inspiratory plateau pressure in the “recent” group was limited to 30 cmH2O under respiratory support, regardless of PaCO2 level. The “historical” and “recent” ARDS groups were compared with regard to therapeutic procedure and outcome. Results: Normalization of PaCO2 (36 ± 6 mmHg) in the “historical” group required high airway pressure (end-inspiratory plateau pressure at 39 ± 4 cmH2O) and high tidal volume (13 ml/kg). Respiratory support used in the “recent” group was less aggressive, with lower airway pressure (end-inspiratory plateau pressure 25 ± 4 cmH2O) and tidal volume (9 ml/kg) resulting in “permissive” hypercapnia (51 ± 10 mmHg).Mortality rates significantly decreased from 64 % in the “historical” group to 32 % in the “recent” group ( p < 0.01). This decrease concerned only ARDSp, which was markedly predominant in both groups. Conclusion: Mortality due to ARDS of pulmonary origin has declined in our unit over the last 15 years. Low-volume, pressure-limited (protective) ventilation seems the most likely reason for improved survival, despite hypercapnia. [ABSTRACT FROM AUTHOR]

The incidence of intra-abdominal hypertension (IAH) is high and still underappreciated by critical care physicians throughout the world. One in four to one in three patients will have IAH on admission, while one out of two will develop IAH within the first week of Intensive Care Unit stay. IAH is associated with high morbidity and mortality. Although considerable progress has been made over the past decades, some important questions remain regarding the optimal ventilation management in patients with IAH. An important first step is to measure intra-abdominal pressure (IAP). If IAH (IAP > 12 mmHg) is present, medical therapies should be initiated to reduce IAP as small reductions in intra-abdominal volume can significantly reduce IAP and airway pressures. Protective lung ventilation with low tidal volumes in patients with respiratory failure and IAH is important. Abdominal-thoracic pressure transmission is around 50%. In patients with IAH, higher positive end-expiratory pressure (PEEP) levels are often required to avoid alveolar collapse but the optimal PEEP in these patients is still unknown. During recruitment manoeuvres, higher opening pressures may be required while closely monitoring oxygenation and the haemodynamic response. During lung-protective ventilation, whilst keeping driving pressures within safe limits, higher plateau pressures than normally considered might be acceptable. Monitoring of the respiratory function and adapting the ventilatory settings during anaesthesia and critical care are of great importance. This review will focus on how to deal with the respiratory derangements in critically ill patients with IAH. [ABSTRACT FROM AUTHOR]

Background: During passive mechanical ventilation, the driving pressure of the respiratory system is an important mediator of ventilator-induced lung injury. Monitoring of driving pressure during assisted ventilation, similar to controlled ventilation, could be a tool to identify patients at risk of ventilator-induced lung injury. The aim of this study was to describe driving pressure over time and to identify whether and when high driving pressure occurs in critically ill patients during assisted ventilation.Methods: Sixty-two patients fulfilling criteria for assisted ventilation were prospectively studied. Patients were included when the treating physician selected proportional assist ventilation (PAV+), a mode that estimates respiratory system compliance. In these patients, continuous recordings of all ventilator parameters were obtained for up to 72 h. Driving pressure was calculated as tidal volume-to-respiratory system compliance ratio. The distribution of driving pressure and tidal volume values over time was examined, and periods of sustained high driving pressure (≥ 15 cmH2O) and of stable compliance were identified and analyzed.Results: The analysis included 3200 h of ventilation, consisting of 8.8 million samples. For most (95%) of the time, driving pressure was < 15 cmH2O and tidal volume < 11 mL/kg (of ideal body weight). In most patients, high driving pressure was observed for short periods of time (median 2.5 min). Prolonged periods of high driving pressure were observed in five patients (8%). During the 661 periods of stable compliance, high driving pressure combined with a tidal volume ≥ 8 mL/kg was observed only in 11 cases (1.6%) pertaining to four patients. High driving pressure occurred almost exclusively when respiratory system compliance was low, and compliance above 30 mL/cmH2O excluded the presence of high driving pressure with 90% sensitivity and specificity.Conclusions: In critically ill patients fulfilling criteria for assisted ventilation, and ventilated in PAV+ mode, sustained high driving pressure occurred in a small, yet not negligible number of patients. The presence of sustained high driving pressure was not associated with high tidal volume, but occurred almost exclusively when compliance was below 30 mL/cmH2O. [ABSTRACT FROM AUTHOR]