Hydrochloric acid-induced lung injury: effects of early partial liquid ventilation on survival rate, gas exchange, and pulmonary neutrophil accumulation

Translational medicine for acute lung injury

Acute lung injury (ALI) is a complex disease with numerous causes. This review begins with a discussion of disease development from direct or indirect pulmonary insults, as well as varied pathogenesis. The heterogeneous nature of ALI is then elaborated upon, including its epidemiology, clinical manifestations, potential biomarkers, and genetic contributions. Although no medication is currently approved for this devastating illness, supportive care and pharmacological intervention for ALI treatment are summarized, followed by an assessment of the pathophysiological gap between human ALI and animal models. Lastly, current research progress on advanced nanomedicines for ALI therapeutics in preclinical and clinical settings is reviewed, demonstrating new opportunities towards developing an effective treatment for ALI.

Partial liquid ventilation for preventing death and morbidity in adults with acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are syndromes of severe respiratory failure that are associated with substantial mortality and morbidity. Artifical ventilatory support is commonly required and may exacerbate lung injury. Partial liquid ventilation (PLV) has been proposed as a less injurious form of ventilatory support for these patients. Although PLV has been shown to improve gas exchange and to reduce inflammation in experimental models of ALI, a previous systematic review did not find any evidence to support or refute its use in humans with ALI and ARDS.

OBJECTIVES

The primary objective of this review was to assess whether PLV reduced mortality (at 28 d, at discharge from the intensive care unit (ICU), at discharge from hospital and at one, two and five years) in adults with ALI or ARDS when compared with conventional ventilatory support.Secondary objectives were to determine how PLV compared with conventional ventilation with regard to duration of invasive mechanical ventilation, duration of respiratory support, duration of oxygen therapy, length of ICU stay, length of hospital stay, incidence of infection, long-term cognitive impairment, long-term health related quality of life, long- term lung function, long-term morbidity costs and adverse events. The following adverse events were considered: hypoxia (arterial PO2 <80 mm Hg), pneumothorax (any air leak into the pleural space requiring therapeutic intervention), hypotension (systolic blood pressure < 90 mm Hg sustained for longer than two minutes or requiring treatment with fluids or vasoactive drugs), bradycardia (heart rate < 50 beats per minute sustained for longer than one minute or requiring therapeutic intervention) and cardiac arrest (absence of effective cardiac output).

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL Issue 10, 2012, in The Cochrane Library; MEDLINE (Ovid SP, 1966 to November 2012); EMBASE (Ovid SP, 1980 to November 2012) and CINAHL (EBSCOhost,1982 to November 2012) for published studies. In our original review, we searched until May 2004.Grey literature was identified by searching conference proceedings and trial registries and by contacting experts in the field.

SELECTION CRITERIA

As in the original review, review authors selected randomized controlled trials that compared PLV with other forms of ventilation in adults (16 y of age or older) with ALI or ARDS, reporting one or more of the following: mortality; duration of mechanical ventilation, respiratory support, oxygen therapy, stay in the intensive care unit or stay in hospital; infection; long-term cognitive impairment or health-related quality of life; long-term lung function or cost.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated the quality of the relevant studies and extracted the data from included studies.

MAIN RESULTS

In this updated review, one new eligible study was identified and included, yielding a total of two eligible studies (including a combined total of 401 participants). Of those 401 participants, 170 received 'high'-dose partial liquid ventilation (i.e. a mean dose of at least 20 mL/kg), 99 received 'low-dose' partial liquid ventilation (i.e. a dose of 10 mL/kg) and 132 received conventional mechanical ventilation (CMV). Pooled estimates of effect were calculated for all those who received 'high'-dose PLV versus conventional ventilation. No evidence indicated that 'high'-dose PLV either reduced mortality at 28 d (risk ratio (RR) 1.21, 95% confidence interval (CI) 0.79 to 1.85, P = 0.37) or increased the number of days free of CMV at 28 d (mean difference (MD) -2.24, 95% CI -4.71 to 0.23, P = 0.08). The pooled estimate of effect for bradycardia in those who received PLV was significantly greater than in those who received CMV (RR 2.51, 95% CI 1.31 to 4.81, P = 0.005). Pooled estimates of effect for the following adverse events- hypoxia, pneumothorax, hypotension and cardiac arrest- all showed a nonsignificant trend towards a higher occurrence of these events in those treated with PLV. Because neither eligible study addressed morbidity or mortality beyond 28 d, it was not possible to determine the effect of PLV on these outcomes.

AUTHORS' CONCLUSIONS

No evidence supports the use of PLV in ALI or ARDS; some evidence suggests an increased risk of adverse events associated with its use.

Effect of the dose volume of perfluorocarbon when starting partial liquid ventilation

OBJECTIVE

Very preterm neonates are prone to brain injury if cerebral blood flow fluctuates. Partial liquid ventilation (PLV) may benefit any lung disease but giving 30 mL/kg of perfluorocarbon when starting PLV increases cortical cerebral blood flow velocity. We aimed to determine if varying the initial dose of perfluorocarbon alters the effect on cerebral blood flow velocity when starting PLV.

METHODS

In this randomised, controlled trial with historical comparison 24 preterm lambs received one of three loading doses of intratracheal perfluorocarbon liquid over 20 min when starting PLV: 20, 30 or 40 mL/kg. Data on respiratory mechanics, haemodynamics and cerebral blood flow velocity, measured with laser Doppler, were collected continuously for 30 min from the start of dosing.

RESULTS

Cortical cerebral blood flow velocity increased over time in all three groups (two-way ANOVA, P= 0.007). There was no difference between groups (two-way ANOVA, P= 0.26). There was no difference between groups in cortical cerebral blood flow velocity variability (P= 0.68), blood pressure (P= 0.96) or heart rate (P= 0.46). The was no statistically significant difference in PaCO(2) between groups measured at baseline and at 30 min after starting PLV (P= 0.51).

CONCLUSIONS

  Cortical cerebral blood flow velocity and its variability are not affected by varying doses of tracheal perfluorocarbon (20, 30 or 40 mL/kg) at the start of PLV in preterm lambs.

Leukocyte antibacterial functions are not impaired by perfluorocarbon exposure in vitro

Application of liquid, aerosolized, and vaporized perfluorocarbons (PFC) in acute lung injury has shown anti-inflammatory effects. Although this may be beneficial in states of pulmonary hyperinflammation, it also could increase susceptibility to nosocomial lung infection. We hypothesized that PFC impair cellular host defense and therefore investigated in an in vitro model the influence of perfluorohexane (PFH) on crucial mechanisms of bacterial elimination in human neutrophils and monocytes. Using scanning and transmission electron microscopy, we could show membrane-bound and ingested PFH particles that morphologically did not alter adherence and phagocytosis of Escherichia coli or leukocyte viability. The amount of adherent and phagocytosed bacteria as determined by flow cytometry was not influenced in cells only pretreated with PFH for 1 and 4 h. When PFH was present during E. coli challenge, bacterial adherence was decreased in polymorphonuclear neutrophils, but respective intracellular uptake was not impaired and was even significantly promoted in monocytes. Overall, E. coli-induced respiratory burst capacity was not reduced by PFH. Our findings provide evidence that key functions of innate host defense are not compromised by PFH treatment in vitro.

Effects of vaporized perfluorohexane and partial liquid ventilation on regional distribution of alveolar damage in experimental lung injury

OBJECTIVE

To determine whether the patterns of distribution of histological effects of vaporized perfluorohexane (PFH) and partial liquid ventilation (PLV) differ significantly in acute lung injury.

DESIGN AND SETTING

Experimental study in an animal research laboratory.

SUBJECTS

Eighteen pigs.

INTERVENTIONS

After induction of acute lung injury by means of infusion of oleic acid animals were randomly assigned to PFH, PLV, or gas ventilation (GV) groups. Six hours thereafter animals were killed, and lung tissue samples were taken for analysis.

MEASUREMENTS AND RESULTS

Histopathological analysis revealed less damage with PFH than with GV or PLV in the nondependent and central regions. PFH and PLV showed less injury in the dependent regions than GV. GV and PFH were associated with less histological damage in the nondependent than the dependent regions, whereas PLV presented the opposite pattern. Morphometric analysis showed increased aeration in nondependent than dependent regions with PFH and GV. PLV led to more aeration in the periphery than in central areas.

CONCLUSIONS

PFH was associated with a more homogeneous attenuation of alveolar damage across the lungs, although this therapy had more pronounced effects in nondependent zones. PLV showed the opposite pattern, with more important reduction in alveolar damage in dependent lung regions. Interestingly, reduction in alveolar damage with PFH was as effective as with PLV in dependent zones. Our findings suggest that vaporized perfluorocarbon could be advantageous as adjunctive therapy in the treatment of acute lung injury.