Ventilation Management in Acute Lung Injury. Strategies for patients with ARDS (original) (raw)
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New strategies in mechanical ventilation for acute lung injury
European Respiratory Journal, 1996
In the fluid-filled lungs of early adult respiratory distress syndrome (ARDS) the dependent parts are compressed and atelectatic; whereas, the nondependent areas remain aerated and functional. Ventilating these considerably restricted lungs carries the risk of overinflation and ventilatory-induced lung injury (baro-volutrauma). The consequences for adjusting mechanical ventilation are: 1) reducing tidal volumes in order to avoid alveolar hyperinflation and excessive alveolar pressures; 2) considering permissive hypercapnia if adequate CO 2 elimination cannot be maintained; 3) keeping open the unstable alveoli by positive end-expiratory pressure (PEEP) (external or intrinsic). However, the large variations in regional lung compliance make it improbable that an optimal external PEEP level beneficial for the whole lung will be found; 4) using intrinsic PEEP in the inverse ratio ventilation (IRV) mode which varies with differences in regional ventilatory kinetics. No clinical study has yet convincingly demonstrated the benefit of IRV compared to conventional ventilation, controlled clinical long-term trials are not yet available; and 5) using superimposed spontaneous breathing which may be considerably more effective in opening up collapsed alveoli, combined with intentional intrinsic PEEP this is achieved in airway pressure release ventilation (APRV). Other new principles of mechanical ventilation, such as "proportional assist ventilation" or "tracheal gas insufflation" must still be considered as experimental.
Mechanical ventilation during acute lung injury: Current recommendations and new concepts
2011
Themostsever e forms of acute respiratory failure, such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), are relatively common in the ICU setting [1]. The estimated crude incidences for ALI and ARDS in the United States are 78.9 and 58.7 cases per 100,000 persons/year respectively, higher than previous reported [1,2]. Projections suggest that as the population ages there will be a further increase in the incidence in the United States from 190,000 patients/year to 300,000/year in 2025-2030 [2]. Furthermore, the incidence will likely increase dramatically during the outbreaks of acute viral infections such as SARS and H1N1. The first description of ARDS appeared in 1967, in a paper by Ashbaugh et al. which described 12 patients with acute respiratory distress, cyanosis refractory to oxygen therapy, decrease lung compliance, and diffuse infiltrates on the chest radiography [3]. Several clinical disorders have
The Korean Journal of Critical Care Medicine, 2009
Background: ASV is a closed-loop ventilation system that guarantees a user-set minimum per-minute volume in intubated patients, whether paralyzed or with spontaneous breathing. Here, we tested the effects of ASV onrespiratory mechanics and compared them with volume-controlled ventilation (VCV). Methods: Thirteen patients meeting the criteria for acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) were enrolled. All patients were paralyzed to eliminate spontaneous breathing. We started with VCV (VCV1), then used ASV followed by VCV modes (VCV2), maintaining minute volume as much as that of VCV1. Results: During ASV, compared with VCV1, the inspiratory and expiratory tidal volumes and expiratory resistance increased. Conversely, the total respiratory rate and maximum pressure decreased. No changes in the arterial blood gases, heart rate, or mean systemic pressure were noted during the trial. Conclusions: In ALI/ARDS patients, although no differences were observed in the arterial blood gas analysis between the two modes, ASV provided better respiratory mechanics in terms of peak airway pressure and tidal volume than VCV.
Mechanical ventilation and lung injury : new advances
2011
printing supported by . Visit Chiesi at Stand D.30 MONDAY, SEPTEMBER 26TH 2011 = 110±71 mmHg). Most of our population (26/38 patients, 68%) resolved their acute episode with HFO. In this group, invasive ventilation was not required and this decision was not stated on EOL care (success group). PaO2/FiO2 at admission was found higher in the success group (126 vs. 76 mmHg, p=0.04). Failure patients (12/38, 32%) exhibited more comorbidities (Charlson’s score = 4.5 vs. 2.5, p=0.034) and appeared more severe at admission (SAPS2 = 45 vs. 31, p=0.0054). After 24 hours, the %FiO2 under HFO was significantly lower in the success group (50% vs. 70%, p=0.004). The hospitalization length was similar in both groups (p=0.28). Hospital mortality rate was significantly higher in the failure group than in the success group ((92% vs. 4%, p<0.0001) as was the 28-days mortality rate (respectively: 83% and 4%, p<0.0001). In conclusion, HFO may avoid endotracheal intubation during ALI/ARDS and its u...
Mechanical Ventilation to Minimize Progression of Lung Injury in Acute Respiratory Failure
American Journal of Respiratory and Critical Care Medicine, 2017
Mechanical ventilation is used to sustain life in patients with acute respiratory failure. A major concern in mechanically ventilated patients is the risk of ventilator-induced lung injury, which is partially prevented by lung-protective ventilation. Spontaneously breathing, nonintubated patients with acute respiratory failure may have a high respiratory drive and breathe with large tidal volumes and potentially injurious transpulmonary pressure swings. In patients with existing lung injury, regional forces generated by the respiratory muscles may lead to injurious effects on a regional level. In addition, the increase in transmural pulmonary vascular pressure swings caused by inspiratory effort may worsen vascular leakage. Recent data suggest that these patients may develop lung injury that is similar to the ventilator-induced lung injury observed in mechanically ventilated patients. As such, we argue that application of a lung-protective ventilation, today best applied with sedation and endotracheal intubation, might be considered a prophylactic therapy, rather than just a supportive therapy, to minimize the progression of lung injury from a form of patient self-inflicted lung injury. This has important implications for the management of these patients.
Effects of a Clinical Trial on Mechanical Ventilation Practices in Patients with Acute Lung Injury
American Journal of Respiratory and Critical Care Medicine, 2008
Rationale: In a clinical trial by the Acute Respiratory Distress Syndrome Network (ARDSNet), mechanical ventilation with tidal volumes of 6 ml/kg decreased mortality from acute lung injury. However, interpretations of these results generated controversy and it was unclear if this trial would change usual-care practices. Objectives: First, to determine if clinical practices at ARDSNet hospitals changed after the tidal volume trial. Second, to determine if tidal volume and plateau pressure (Pplat) within 48 hours before randomization affected hospital mortality in patients subsequently managed with 6 ml/kg predicted body weight (PBW). Methods: We used preenrollment data from 2,451 patients enrolled in six trials (1996-2005) to describe changes in tidal volume over time. We used logistic regression to determine if preenrollment tidal volume or Pplat affected mortality. Measurements and Main Results: Median preenrollment tidal volume decreased from 10.3 ml/kg PBW (range, 4.3-17.1) during the tidal volume trial (1996-1999) to 7.3 ml/kg PBW (range, 3.9-16.2) after its completion (P , 0.001). Preenrollment tidal volume was not associated with mortality (P 5 0.566). The odds of death increased multiplicatively with each cm H 2 O of preenrollment Pplat (P , 0.001) (e.g., the odds of death was 1.37 times greater when preenrollment Pplat increased by 10 cm H 2 O). Conclusions: Physicians used lower tidal volumes after publication of the tidal volume trial. Preenrollment Pplat was strongly associated with mortality, and may reflect disease severity independent of tidal volume. Pplat measured early in the course of acute lung injury, after accounting for tidal volume, is a respiratory system-specific value with strong prognostic significance.
1998
Because animal studies have demonstrated that mechanical ventilation at high volume and pressure can be deleterious to the lungs, limitation of airway pressure, allowing hypercapnia if necessary, is already used for ventilation of acute respiratory distress syndrome (ARDS). Whether a systematic and more drastic reduction is necessary is debatable. A multicenter randomized study was undertaken to compare a strategy aimed at limiting the end-inspiratory plateau pressure to 25 cm H 2 O, using tidal volume (V T ) below 10 ml/kg of body weight, versus a more conventional ventilatory approach (with regard to current practice) using V T at 10 ml/kg or above and close to normal Pa CO 2 . Both arms used a similar level of positive end-expiratory pressure. A total of 116 patients with ARDS and no organ failure other than the lung were enrolled over 32 mo in 25 centers. The two groups were similar at inclusion. Patients in the two arms were ventilated with different V T (7.1 Ϯ 1.3 versus 10.3 Ϯ 1.7 ml/kg at Day 1, p Ͻ 0.001) and plateau pressures (25.7 Ϯ 5.0 versus 31.7 Ϯ 6.6 cm H 2 O at Day 1, p Ͻ 0.001), resulting in different Pa CO 2 (59.5 Ϯ 15.0 versus 41.3 Ϯ 7.6 mm Hg, p Ͻ 0.001) and pH (7.28 Ϯ 0.09 versus 7.4 Ϯ 0.09, p Ͻ 0.001), but a similar level of oxygenation. The new approach did not reduce mortality at Day 60 (46.6% versus 37.9% in control subjects, p ϭ 0.38), the duration of mechanical ventilation (23.1 Ϯ 20.2 versus 21.4 Ϯ 16.3 d, p ϭ 0.85), the incidence of pneumothorax (14% versus 12%, p ϭ 0.78), or the secondary occurrence of multiple organ failure (41% versus 41%, p ϭ 1). We conclude that no benefit could be observed with reduced V T titrated to reach plateau pressures around 25 cm H 2 O compared with a more conventional approach in which normocapnia was achieved with plateau pressures already below 35 cm H 2 O.
Chest, 2002
Study objectives: The potential clinical benefits of pressure-controlled ventilation (PCV) over volume-controlled ventilation (VCV) in patients with acute lung injury (ALI) or ARDS still remain debated. We compared PCV with VCV in patients with ALI/ARDS with respect to the following physiologic end points: (1) gas exchange and airway pressures, and (2) CT scan intrapulmonary gas distribution at end-expiration. Design: Prospective, observational study. Setting: A multidisciplinary ICU in a nonuniversity, acute-care hospital. Patients: Ten patients with ALI or ARDS (9 men and 1 woman; age range, 17 to 80 years). Interventions: Sequential ventilation in PCV and VCV with a constant inspiratory/expiratory ratio, tidal volume, respiratory rate, and total positive end-expiratory pressure; measurement of gas exchange and airway pressures; and achievement of CT sections at lung base, hilum, and apex for the quantitative analysis of lung densities and of aerated vs nonaerated zones. Results: PaO 2 , PaCO 2 , and PaO 2 /fraction of inspired oxygen ratio levels did not differ between PCV and VCV. Peak airway pressure (Ppeak) was significantly lower in PCV compared with VCV (26 ؎ 2 cm H 2 O vs 31 ؎ 2 cm H 2 O; p < 0.001; mean ؎ SEM). The surface areas of the nonaerated zones as well as the total areas at each section level were unchanged in PCV compared with VCV, except at the apex level, where there was a significantly greater nonaerated area in VCV (11 ؎ 2 cm 2 vs 9 ؎ 2 cm 2 ; p < 0.05). The total mean CT number of each lung (20 lungs from 10 patients) was similar in the two modes, as were the density values at the basal and apical levels; the hilum mean CT number was ؊ 442 ؎ 28 Hounsfield units (HU) in VCV and ؊ 430 ؎ 26 HU in PCV (p < 0.005). Conclusions: These data show that PCV allows the generation of lower Ppeaks through the precise titration of the lung distending pressure, and might be applied to avoid regional overdistension by means of a more homogeneous gas distribution.