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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]

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]

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]