Year in review 2008: Critical Care--respirology

Non-invasive ventilation in acute respiratory failure: a meta-analysis

Non-invasive positive-pressure ventilation (NPPV) has assumed an important role in the management of respiratory failure because it provides ventilatory support without the need for an invasive airway. However, its effectiveness remains unclear. We performed this meta-analysis to investigate the utility of NPPV intervention in patients with acute respiratory failure (ARF). A comprehensive literature search identified 12 studies enrolling a total of 963 patients from Medline, PubMed, Cochrane and EMBASE databases that assessed the effectiveness of NPPV versus conventional mechanical ventilation and/or non-ventilation therapy in patients with ARF, irrespective of the underlying aetiology, as well as mortality rate and the length of intensive care unit (ICU) or hospital stay. The usage of NPPV was associated with significantly decreased intubation (pooled OR=0.23, 95% CI 0.12-0.42, p<0.001) and ICU mortality rate (pooled OR=0.34, 95% CI 0.20-0.60, p<0.001), but did not influence the hospital mortality rate (pooled OR=0.77, 95% CI 0.32-1.81, p=0.543) and the length of ICU or hospital stay (ICU stay: difference in means=0.38, 95% CI -3.01 to 3.77, p=0.825; hospital stay: difference in means=2.76, 95% CI -1.74 to 7.27, p=0.229). In conclusion, usage of NPPV in patients with ARF is associated with lower intubation and in-ICU mortality rate.

A study of noninvasive positive-pressure mechanical ventilation in the treatment of acute lung injury with a complex critical care ventilator

OBJECTIVE

To test the hypothesis that there would be better clinical outcomes following the treatment of patients with acute lung injury (ALI) using noninvasive positive-pressure mechanical ventilation (NIPPV) delivered via a complex critical care ventilator compared with a conventional mini-ventilator.

METHODS

Patients with ALI who required NIPPV were prospectively enrolled and randomly divided between three intervention groups: group A was ventilated using a mini-ventilator; groups B and C were ventilated using a complex critical care ventilator using different settings. Clinical parameters were recorded before and after 8 h of mechanical ventilation.

RESULTS

A total of 51 patients with ALI were enrolled in the study. Clinical parameters in groups B and C underwent greater improvements than those in group A. Group C demonstrated the lowest treatment failure rate (23.5%). Failure rates were highest in group A (58.8%).

CONCLUSION

The findings of this present study suggest that there were more satisfactory clinical outcomes following the treatment of patients with ALI when NIPPV was delivered using a complex critical care ventilator compared with a conventional mini-ventilator.

Kinetic and distinct distribution of conventional dendritic cells in the early phase of lipopolysaccharide-induced acute lung injury

Respiratory dendritic cells (DCs), especially conventional DCs (cDCs), are critically involved in the induction phase of the immune response in the respiratory system. However, little information concerning cDC kinetics in acute lung injury (ALI) is available. In this study, we have used a murine model of LPS-induced ALI to examine the kinetics and phenotype of respiratory, circulating and splenic cDCs. cDCs in the lung, blood, and spleen and the IL-6 level in the lung were detected at 6, 12 and 24 h after PBS or LPS challenge. In the ALI group, a rapid cDCs accumulation in the lung was observed, and there were highly significant correlations between the frequency of respiratory cDCs or the percentage of cDC expressing CD80 and the IL-6 concentration. However, the frequency of peripheral blood cDCs decreased rapidly in ALI mice, followed by a marked expansion. In addition, splenic cDCs only showed a transient expansion in ALI. cDCs within the blood, lungs and spleens had undergone a modest maturation in the ALI group. Our findings demonstrate that LPS-induced ALI provokes a dynamic and distinct distribution as well as phenotype changes in pulmonary, circulatory and splenic cDC populations. Lung cDCs may participate in the early inflammatory response to ALI.

Plasma Krebs von den Lungen glycoprotein, lung injury, and noninvasive ventilation in Duchenne muscular dystrophy

OBJECTIVE

There have been few reports of ventilator-induced lung injury associated with noninvasive ventilation (NIV), but many with invasive mechanical ventilation. The purpose of this study was to detect subclinical NIV-associated lung injury by monitoring Krebs von den Lungen glycoprotein plasma levels.

DESIGN

Forty-one Duchenne muscular dystrophy patients were divided into three categories: group 1, asymptomatic and not using ventilators; group 2, NIV use less than 24 hrs/day at full ventilatory support settings; and group 3, continuous NIV dependence. Plasma Krebs von den Lungen glycoprotein level was measured by electrochemical luminescent immunoassay using Krebs von den Lungen glycoprotein antibodies. One-way analysis of variance, followed by the Tukey-Kramer test, was used as appropriate to compare intergroup differences.

RESULTS

Extent of ventilator dependence correlated with age (P < 0.05). Intergroup plasma Krebs von den Lungen glycoprotein levels were not significantly different.

CONCLUSIONS

NIV used at volumes and pressures of full (invasive) ventilatory support may not induce the alveolar septal barrier injury commonly seen with invasive mechanical ventilation.

Map kinase phosphatase 5 protects against sepsis-induced acute lung injury

Mitogen-activated protein kinases (MAPKs) play a critical role in inflammation. Although activation of MAPK in inflammatory cells has been studied extensively, much less is known about the inactivation of these kinases. MAPK phosphatase 5 (MKP5) is a member of the dual-specificity phosphatase family that dephosphorylates activated MAPKs. Here we report that MKP5 protects sepsis-induced acute lung injury. Mice lacking MKP5 displayed severe lung tissue damage following LPS challenge, characterized with increased neutrophil infiltration and edema compared with wild-type (WT) controls. In response to LPS, MKP5-deficient macrophages produced significantly more inflammatory factors including inflammatory cytokines, nitric oxide, and superoxide. Phosphorylation of p38 MAPK, JNK, and ERK were enhanced in MKP5-deficient macrophages upon LPS stimulation. Adoptive transfer of MKP5-deficient macrophages led to more severe lung inflammation than transfer of WT macrophages, suggesting that MKP5-deficient macrophages directly contribute to acute lung injury. Taken together, these results suggest that MKP5 is crucial to homeostatic regulation of MAPK activation in inflammatory responses.