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The adequacy of humidification of heat and moisture exchangers (HMEs) during long-term mechanical ventilation is still controversial. Recently, an active HME (AHME) (Humid-Heat, Gibeck) has been developed. This AHME combines a HME with a unit which adds water and heat between the patient and the HME. The AHME automatically regulates the water and heat supply. The only user-set input for AHME is the minute ventilation (V'e) of the patient. We evaluated the AHME efficiency for humidification during long-term mechanical ventilation.

Although they represent a valuable alternative to heated humidifiers, artificial noses have unfavourable mechanical effects. Most important of these is the increase in dead space, with consequent increase in the ventilation requirement. Also, artificial noses increase the inspiratory and expiratory resistance of the apparatus, and may mildly increase intrinsic positive end-expiratory pressure. The significance of these effects depends on the design and function of the artificial nose. The pure humidifying function results in just a moderate increase in dead space and resistance of the apparatus, whereas the combination of a filtering function with the humidifying function may critically increase the volume and the resistance of the artificial nose, especially when a mechanical filter is used. The increase in the inspiratory load of ventilation that is imposed by artificial noses, which is particularly significant for the combined heat-moisture exchanger filters, should be compensated for by an increase either in ventilator output or in patient's work of breathing. Although both approaches can be tolerated by most patients, some exceptions should be considered. The increased pressure and volume that are required to compensate for the artificial nose application increase the risk of barotrauma and volutrauma in those patients who have the most severe alterations in respiratory mechanics. Moreover, those patients who have very limited respiratory reserve may not be able to compensate for the inspiratory work imposed by an artificial nose. When we choose an artificial nose, we should take into account the volume and resistance of the available devices. We should also consider the mechanical effects of the artificial noses when setting mechanical ventilation and when assessing a patient's ability to breathe spontaneously.

In a multicentre study, influenza A/H1N1/09v 222G/N variants were more frequently detected in patients admitted to the intensive-care unit for invasive mechanical ventilation or extracorporeal membrane oxygenation (10/23; 43.5%) than in patients hospitalized in other units (2/27; 7.4%) and community patients (0/81; 0.0%) (p

Respiratory failure may be caused by either lung failure or pump failure or a combination of both. Even when the initial cause is lung failure the respiratory muscles, which are faced with a high work of breathing because of the altered mechanical characteristics of the lungs, are exposed to fatigue, i.e. inability to generate the required force. Most patients need mechanical ventilation because of an imbalance between the required work of breathing and ventilatory pump performance. Pump failure, however, is very seldom complete and in most instances, the patient's ventilatory potential can be used in a variety of partial ventilatory support modes. In the 1980's the preservation of spontaneous breathing is relatively easily provided by modern ventilators, either by minute volume integration - IMV, SIMV, MMV, APRV - or by breath-by-breath integration - AMV, ACV, PSV - (see below for abbreviations). With some of these modes, such as PSV and APRV, ventilatory support is achieved by pressure control, whilst the other modes work by volume control.

Continuous positive airway pressure is widely used in the treatment of ARF and an evaluation of the systems is important. The authors used an artificial model to test a continuous flow system with a high compliance reservoir bag. The results confirm that the system is effective in maintaining positive pressure stability within a wide range of inspiratory peak flow rates, even when a low fresh gas flow rate is employed. Nevertheless, rebreathing of expired gases is possible and may be noticeable at high expiratory flow rates, caused by the high compliance of the reservoir bag.

Unstable inspiratory pressure may reduce the benefits of intermittent mandatory ventilation and impose a greater work of breathing than some patients can tolerate. The authors evaluated a continuous flow intermittent mandatory ventilation with continuous positive airway pressure apparatus provided with a 10-L high compliance reservoir bag, separated from the ventilator circuit by a one-way valve. A pulmonary simulator was tested to generate a wide range of inspiratory peak flow rates. Pressures and flow rates were examined in different sections of the system, using PEEP levels up to 15 mm Hg and different fresh gas flow rates. The circuit offers many advantages, particularly considering the low inspiratory pressure drop and the low fresh gas flow rates needed for optimal function.

In 34 patients, we assessed the reproducibility and accuracy of a new, computerized, thermodilution method that determines right ventricular ejection fraction (RVEF). We compared the results from this new algorithm with simultaneous results from the conventional plateau thermodilution method and from both first-pass and gated nuclear techniques. Using this new method improved the reproducibility of thermal determinations of RVEF. Although the thermal values were lower, the correlations between thermal and nuclear measurements were close [r = .92 (first-pass technique), r = .81 (gated technique)]. This new method seems particularly appropriate for serial monitoring of RV performance.

Serial measurements of blood haemoglobin, serum iron, serum transferrin, total iron-binding capacity, transferrin per cent saturation and serum ferritin were determined in 51 post-operative critically ill patients to investigate body iron status in severely stressed patients. The results showed decreased blood haemoglobin, serum iron, serum transferrin and transferrin saturation compared to an increase in serum ferritin levels. These results indicate that there is inadequate availability of iron to tissues (secondary to rearrangement of body iron to the advantage of the iron storage compartment), which is often present in severely critically ill patients. A positive correlation was found between the initial (ferritin) levels and SAPS (r = 0.41, p less than 0.01). In addition, the increase of ferritin concentration parallels a worsening of the clinical status in severely ill patients. This is due to enhanced release by the macrophage system. From this, we consider serum ferritin as an acute-phase protein and a useful marker of the severity of the clinical status. It appears to be useful in predicting the patient's outcome, but is not reliable in evaluating iron stores in stressed patients.

Objective Evaluation of the respiratory pattern selected by the Adaptive Support Ventilation (ASV) in ventilated patients with acute, chronic respiratory failure and normal lungs and in a physical lung model. Design We tested ASV both on patients and in a physical lung model, with a normal level of minute ventilation and with minute ventilation increased by 30%. In each patient, respiratory pattern, mechanics and blood gases were recorded. Setting General ICU of a University Hospital. Results In patients with normal lungs, mean values±SD were: tidal volume (Vt) 558.1±142.4mL, respiratory rate (RR) 12.6±1.3b/min and inspiratory time/total time ratio (Ti/Ttot) 42.4±4.1%; in COPD, mean values±SD were: Vt 724±171mL, RR 9.2±2.7b/min and Ti/Ttot 26.6±10.5%; in restrictive ones, mean values±SD were: Vt 550.2±77.0mL, RR 15.8±2.6b/min, Ti/Ttot 47.5±2.5%. In the lung model, at a normal setting, mean values±SD were: Vt 523±18.5mL, RR 14±0.0b/min, Ti/Ttot 44.0%, in COPD, mean values±SD were: Vt 678±0.0mL, RR 9±0.0b/min, Ti/Ttot 20±0.7%, in restrictive one, mean values±SD were: Vt 513±12.8mL, RR 15±0.0b/min, Ti/Ttot 48±1.5%. In model hyperventilation conditions in a normal setting a Vt of 582±16.6mL, RR 16±0.0b/min, Ti/Ttot 48±0.0% were selected, in the obstructive setting Vt 883±0.0mL, RR 9±0.0b/min, Ti/Ttot 20±0.0% and in a restrictive one Vt 545±8.4mL, RR 18±0.0b/min, Ti/Ttot 50±0.0%. Conclusions In normal patients ASV selected a ventilatory pattern close to the physiological one, in COPD almost a high expiratory time pattern and in restrictive ones a reduced tidal volume pattern. In the model the selection was similar. In the hyperventilation test, ASV chose a balanced increase in both Vt and RR.

Background Esophageal pressure (Pes) can provide information to guide mechanical ventilation in acute respiratory failure. However, both relative changes and absolute values of Pes can be affected by inappropriate filling of the esophageal balloon and by the elastance of the esophagus wall. We evaluated the feasibility and effectiveness of a calibration procedure consisting in optimization of balloon filling and subtraction of the pressure generated by the esophagus wall (Pew). Methods An esophageal balloon was progressively filled in 36 patients under controlled mechanical ventilation. VBEST was the filling volume associated with the largest tidal increase of Pes. Esophageal wall elastance was quantified and Pew was computed at each filling volume. Different filling strategies were compared by performing a validation occlusion test. Results Fifty series of measurements were performed. VBEST was 3.5 ± 1.9 ml (range 0.5–6.0). Esophagus elastance was 1.1 ± 0.5 cmH2O/ml (0.3–3.1). Both Pew and the result of the occlusion test differed among filling strategies. At filling volumes of 0.5, VBEST and 4.0 ml respectively, Pew was 0.0 ± 0.1, 2.0 ± 1.9, and 3.0 ± 1.7 cmH2O (p

In patients with idiopathic alveolar proteinosis, the alveoli are filled with materials rich in surfactant components, especially surfactant protein A (SP-A). The anomaly could be caused by either increased secretion, decreased clearance, or both. To clarify this point, we studied five patients who underwent therapeutic lavage and then were ventilated mechanically for 24 h. During the first 8 h of mechanical ventilation, a surfactant-depleted lung was lavaged at selected intervals, and the bronchoalveolar lavage fluid was analyzed. We observed that, after lavage, various surfactant components accumulated in the airways with different time courses. We also observed that SP-A increased until the second hour and then dropped rapidly, suggesting the existence of an efficient mechanism of removal. These findings suggest that idiopathic alveolar proteinosis might be caused by a primary defect in a slow mechanism of removal or by the presence of factor(s) that interfere with the clearance of surfactant and that can be removed by lavage. It seems clear, however, that an increased secretion rate is unlikely to be the major cause of idiopathic alveolar proteinosis.