Partial liquid ventilation for the prevention of mortality and morbidity in paediatric acute lung injury and acute respiratory distress syndrome

  • Review
  • Intervention

Authors


Abstract

Background

Acute lung injury and acute respiratory distress syndrome are syndromes of severe respiratory failure. Children with acute lung injury or acute respiratory distress syndrome have high mortality and the survivors have significant morbidity. Partial liquid ventilation is proposed as a less injurious form of respiratory support for these children. Uncontrolled studies in adults have shown improvements in gas exchange and lung compliance with partial liquid ventilation. A single uncontrolled study in six children with acute respiratory syndrome showed some improvement in gas exchange during three hours of partial liquid ventilation. This review was originally published in 2004, updated in 2009 and again in 2012.

Objectives

To assess whether partial liquid ventilation reduces mortality or morbidity, or both, in children with acute lung injury or acute respiratory distress syndrome.

Search methods

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 11); CINAHL (Cumulative Index to Nursing & Allied Health Literature) via Ovid (1982 to November 2011); Ovid MEDLINE (1950 to November 2011); and Ovid EMBASE (1982 to November 2011). The search was last performed in August 2008.

Selection criteria

We included randomized controlled trials (RCTs) which compared partial liquid ventilation with other forms of ventilation in children (aged 28 days to 18 years) with acute lung injury or acute respiratory distress syndrome. Trials had to report 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, neurodevelopmental progress, or other long-term morbidities.

Data collection and analysis

We independently evaluated the quality of the relevant studies and extracted the data from the included studies.

Main results

Only one study enrolling 182 patients (reported as an abstract in conference proceedings) was identified and found eligible for inclusion; the authors reported only limited results. The trial was stopped prematurely and was, therefore, under-powered to detect any significant differences and at high risk of bias. The only available outcome of clinical significance was 28-day mortality. There was no statistically significant difference between groups, with a relative risk for 28-day mortality in the partial liquid ventilation group of 1.54 (95% confidence interval 0.82 to 2.9).

Authors' conclusions

There is no evidence from RCTs to support or refute the use of partial liquid ventilation in children with acute lung injury or acute respiratory distress syndrome. Adequately powered, high quality RCTs are still needed to assess its efficacy. Clinically relevant outcome measures should be assessed (mortality at discharge and later, duration of both respiratory support and hospital stay, and long-term neurodevelopmental outcomes). The studies should be published in full.

Résumé scientifique

La ventilation liquide partielle pour la prévention de la mortalité et la morbidité chez les patients pédiatriques présentant des lésions pulmonaires aiguës et un syndrome de détresse respiratoire aiguë

Contexte

Les lésions pulmonaires aiguës et le syndrome de détresse respiratoire aiguë sont des syndromes d'insuffisance respiratoire sévère. Les enfants présentant des lésions pulmonaires aiguës ou un syndrome de détresse respiratoire aiguë ont une forte mortalité et les survivants présentent une morbidité significative. On a proposé la ventilation liquide partielle comme une forme d'assistance respiratoire moins nocive pour ces enfants. Des études non contrôlées chez les adultes ont montré une amélioration de l'échange gazeux et de la compliance pulmonaire avec la ventilation liquide partielle. Une seule étude non contrôlée portant sur six enfants présentant un syndrome respiratoire aigu a montré une certaine amélioration de l'échange gazeux pendant trois heures de ventilation liquide partielle. Cette revue a été publiée à l'origine en 2004, mise à jour en 2009 et à nouveau en 2012.

Objectifs

Évaluer si la ventilation liquide partielle réduit la mortalité ou la morbidité, ou les deux, chez les enfants présentant des lésions pulmonaires aiguës ou un syndrome de détresse respiratoire aiguë.

Stratégie de recherche documentaire

Dans cette revue mise à jour, nous avons effectué des recherches dans le registre Cochrane des essais contrôlés (CENTRAL) (La Bibliothèque Cochrane2011, numéro 11) ; CINAHL (Cumulative Index to Nursing & Allied Health Literature) via Ovid (de 1982 à novembre 2011) ; Ovid MEDLINE (de 1950 à novembre 2011) ; et Ovid EMBASE (de 1982 à novembre 2011). La dernière recherche a été effectuée en août 2008.

Critères de sélection

Nous avons inclus les essais contrôlés randomisés (ECR) qui comparaient la ventilation liquide partielle avec d'autres formes de ventilation chez les enfants (âgés de 28 jours à 18 ans) présentant des lésions pulmonaires aiguës ou un syndrome de détresse respiratoire aiguë. Les essais devaient rendre compte d'un ou plusieurs des critères suivants : mortalité ; durée de la ventilation mécanique, assistance respiratoire, oxygénothérapie, séjour en unité de soins intensifs, ou séjour à l'hôpital ; infection ; un trouble cognitif à long terme, développement neurologique ou d'autres morbidités à long terme.

Recueil et analyse des données

Nous avons indépendamment évalué la qualité des études pertinentes et extrait les données des études incluses.

Résultats principaux

Une seule étude portant sur 182 patients (rapporté sous forme de résumé dans les actes de congrès) a été identifié et était éligible pour inclusion ; les auteurs ont rapporté que peu de résultats. L'essai a été arrêté prématurément et, par conséquent, avait une puissance statistique insuffisante pour détecter toute différence significative et était à risque élevé de biais. Le seul résultat disponible avec une signification clinique était la mortalité à 28 jours. Il n'y avait aucune différence statistiquement significative entre les groupes, avec un risque relatif pour la mortalité à 28 jours observé dans le groupe de ventilation liquide partielle de 1,54 (intervalle de confiance à 95 % 0,82 à 2,9).

Conclusions des auteurs

Il n'existe aucune donnée issue d'ECR pour étayer ou réfuter l'utilisation de la ventilation liquide partielle chez les enfants présentant des lésions pulmonaires aiguës ou un syndrome de détresse respiratoire aiguë. Des ECR avec une puissance suffisante et de haute qualité sont encore nécessaires pour évaluer son efficacité. Des critères de jugement cliniquement pertinents devraient être évalués (la mortalité à la sortie d'hôpital et ultérieurement, la durée de l'assistance respiratoire et de l'hospitalisation, et les résultats neurodéveloppementaux à long terme). Les études devraient être publiées dans leur intégralité.

Plain language summary

Partial liquid ventilation for mechanical ventilation of severely ill children with acute lung injury and acute respiratory distress syndrome

The use of partial liquid ventilation to decrease the number of deaths and illness in children with acute onset respiratory failure is not supported by evidence from randomized controlled trials.

Severely ill children can develop lung disease, called acute lung injury or acute respiratory distress syndrome, which stops sufficient oxygenation of the blood. The children are treated with mechanical ventilation through a tube placed in the airway. This improves lung function and the supply of oxygen to the body but it can also lead to ventilator-induced lung injury. Children who survive an episode of this severe lung disease often have long-term illness including decreased lung function, impaired cognitive function, poor neurodevelopmental progress, and high rates of permanent disability.

Partial liquid ventilation could be a less injurious form of respiratory support. A special liquid (perfluorocarbon liquid) is poured into the lungs to partly replace the gas in the normally gas-filled lungs, and mechanical ventilation is continued with a gas ventilator.

We found only one multicentre randomized controlled study, reported as an abstract in conference proceedings, that was eligible for inclusion in this updated Cochrane review. The company sponsored study enrolled 182 patients in 65 centres. The trial was stopped early, before recruiting sufficient numbers of participants and before it could detect any clear differences between partial liquid ventilation and conventional mechanical ventilation (the control group). The number of deaths at 28 days was 22% of patients in the partial liquid ventilation group and 14% in the control group, the difference was not statistically significant; there was a wide variation in results and a clinically significant difference could not be excluded. There were other problems with the trial that made its results unreliable in terms of eligible patients, use of other rescue therapies, and that the measured outcomes were altered at least twice during the study; additional therapies such as high frequency ventilation or inhaled nitric oxide were allowed in the control group.

Résumé simplifié

La ventilation liquide partielle pour la ventilation mécanique des enfants gravement malades présentant des lésions pulmonaires aiguës et un syndrome de détresse respiratoire aiguë

L'utilisation de la ventilation liquide partielle pour réduire le nombre de décès et la morbidité chez les enfants atteints de manifestation aiguë d'insuffisance respiratoire n'est pas soutenue par des données issues d'essais contrôlés randomisés.

Les enfants gravement malades peuvent développer une maladie pulmonaire, appelée lésion pulmonaire aiguë ou syndrome de détresse respiratoire aiguë, qui empêche l'oxygénation suffisante du sang. Les enfants sont traités avec la ventilation mécanique via un tube placé dans les voies respiratoires. Cela améliore la fonction pulmonaire et l'apport d'oxygène à l'organisme mais cela peut également entraîner des lésions pulmonaires induites par la ventilation. Les enfants qui survivent à un épisode de cette maladie pulmonaire grave présentent souvent une maladie à long terme, notamment une diminution de la fonction pulmonaire, une altération de la fonction cognitive, un mauvais développement neurologique, et des taux élevés d'invalidité permanente.

La ventilation liquide partielle pourrait être une forme d'assistance respiratoire moins nocive.Un liquide spécial (le perfluorocarbone) est introduit dans les poumons pour remplacer en partie le gaz dans les poumons normalement remplis de gaz, et la ventilation mécanique est poursuivie avec un insufflateur de gaz.

Nous n'avons trouvé quune seule étude contrôlée randomisée multicentrique, rapporté sous forme de résumé dans des actes de conférence, qui était éligible à l'inclusion dans cette mise à jour de la revue Cochrane. L'étude, parrainée par la firme, a recruté 182 patients dans 65 centres. L'essai a été arrêté prématurément, avant d'avoir recruté un nombre suffisant de participants, et avant d'avoir pu détecter toute différence nette entre la ventilation liquide partielle et la ventilation mécanique conventionnelle (le groupe témoin). Le nombre de décès à 28 jours était de 22 % des patients dans le groupe de ventilation liquide partielle et 14 % dans le groupe témoin, la différence n'était pas statistiquement significative ; il y avait une grande variation dans les résultats et une différence cliniquement significative n'a pas pu être exclue. Il y avait d'autres problèmes liés à cet essai, qui rendent ses résultats peu valide, en termes de patients éligibles, d'utilisation d'autres traitements de secours, et le fait que les critères de jugement ont été modifiés au moins deux fois pendant l'étude ; dautres traitements tels que la ventilation à haute fréquence ou le monoxyde d'azote inhalé étaient autorisées dans le groupe témoin.

Notes de traduction

Aucun

Traduit par: French Cochrane Centre 16th January, 2014
Traduction financée par: Instituts de Recherche en Sant� du Canada, Minist�re de la Sant� et des Services Sociaux du Qu�bec, Fonds de recherche du Qu�bec Sant� et Institut National d'Excellence en Sant� et en Services Sociaux

Background

Description of the condition

Acute lung injury (ALI), known in its most severe form as acute respiratory distress syndrome (ARDS), is a syndrome of severe respiratory failure characterized by acute onset severe hypoxaemia and bilateral chest infiltrates on chest x-ray, without evidence of left heart failure. ARDS was first described by Ashbaugh in 1967 (Ashbaugh 1967) in a case series that included one 11 year old child. The causes of ALI or ARDS are many. They may result from lung disease (pneumonia, aspiration or inhalation injury, lung trauma, fat emboli, near-drowning) or extrapulmonary causes (septicaemia, trauma and shock, cardio-pulmonary bypass, drug overdose, acute pancreatitis, transfusion) (Ware 2000). Malignancy and infection (septicaemia or pneumonia) are common underlying antecedents in children (Davis 1993; DeBruin 1992; Timmons 1991).

ALI or ARDS results in poor matching of ventilation and perfusion within the lung, and subsequent severe hypoxaemia. This situation is known as ventilation-perfusion (V/Q) mismatch. The syndrome is also characterized by severe heterogeneous atelectasis and decreased lung compliance. Hence, patients with ALI or ARDS universally require respiratory support and the mainstay of treatment is endotracheal intubation and mechanical ventilation (Tobin 2001). The syndrome is also characterized by a prominent pulmonary and systemic inflammatory response. There is loss of integrity of the alveolar-capillary barrier in the lung with increased inflammatory cell and oxygen free radical mediated injury and increased pulmonary and systemic pro-inflammatory cytokines (Ware 2000). ALI or ARDS is further complicated by ventilator-induced lung injury (VILI) and associated secondary inflammatory effects. VILI arises through either overdistention of the lung (volutrauma) or the use of high pressure within the lung (barotrauma), or a combination of these factors. Decreasing baro- and volutrauma may lower mortality and morbidity (Tobin 2001; van der Werf 2001).

Generally accepted mortality figures for ALI or ARDS in adults have ranged from 40% to 60% (Ware 2000) although studies have shown decreasing mortality over time (Abel 1998; Milberg 1995). Mortality in children seems to be somewhat greater, with typical rates higher than 60% (Costil 1995; Davis 1993; DeBruin 1992; Paret 1998; Timmons 1991). Mortality is often due to the primary disease process, especially septicaemia or associated multiple organ system failure (MOSF), rather than respiratory failure per se (Monchi 1998; Pfenninger 1996; Ware 2000; Zilberberg 1998) and therefore may not be amenable to alterations in ventilatory techniques.

Recent studies show a lower mortality with 'protective' ventilatory strategies or an 'open-lung' approach in adults with ARDS. This suggests that VILI does have a role in increasing mortality and that decreasing baro- and volutrauma may lead to improved survival (Abel 1998Amato 1998ARDS Network 2000Baudouin 2001Tobin 2001van der Werf 2001). A recent Cochrane systematic review (Petrucci 2007) on ventilation with lower tidal volumes versus traditional tidal volumes in adults with ALI or ARDS concluded that whilst short-term mortality was reduced by using ventilation with lower tidal volume there was insufficient evidence to draw any conclusions about morbidity and long-term outcomes. Mortality and other outcomes have been shown to vary with the sex and age of the patient, the initial severity of the ALI or ARDS, the patient's condition, and the underlying cause of the ALI or ARDS (Davis 1993DeBruin 1992Monchi 1998Paret 1998Suntharalingam 2001Ware 2000).

There is also substantial short- and long-term morbidity associated with these syndromes. Short-term morbidity leads to prolonged ventilator dependence and longer stays in the intensive care unit (ICU) and hospital. Long-term morbidity includes decreased lung function, decreased health-related quality of life, neurodevelopmental delay, cognitive impairments, and high rates of disability (Fanconi 1985Rothenhausler 2001Schelling 2000).

Description of the intervention

The mainstay of treatment of ALI or ARDS is mechanical ventilation. Many forms of additional therapies have been considered and some of these were subjected to randomized controlled trials. Adjuncts to mechanical ventilation have included extracorporeal life support (ECLS), inhaled nitric oxide, endogenous surfactant, prone positioning, high frequency ventilation, and a variety of pharmaceutical therapies (anti-inflammatory medication, antioxidants, anticytokine agents, prostaglandins) (Conner 2000; Sarnaik 1994). The ventilatory techniques that seem to improve outcomes in ALI or ARDS are the 'lung-protective' strategies that aim to decrease VILI (Brower 2000; van der Werf 2001).

Partial liquid ventilation (PLV) has been proposed as a less injurious form of respiratory support for patients with severe respiratory failure, ALI and ARDS. In 1991, Fuhrman et al (Fuhrman 1991) introduced the technique of using functional residual capacity (FRC) volumes of perfluorocarbon liquid (PFC) with conventional gas ventilation; they called it perfluorocarbon associated gas exchange (PAGE).

How the intervention might work

This technique has become known as PLV and consists of partially filling the lungs with PFC whilst continuing mechanical ventilation with a gas ventilator. Of the available techniques of liquid assisted ventilation, it is PLV which has the most promise for practical clinical application in intensive care. Various models of acute lung injury have shown the benefits of using PLV compared with conventional mechanical ventilation alone. Many animal studies have shown that PLV improves oxygenation, carbon dioxide (CO2) removal, and lung compliance, and leads to less lung damage and VILI (Davies 1999; Wiedemann 2000). All of these benefits are achieved whilst using lower ventilatory pressures and smaller tidal volumes (Davies 1999; Wiedemann 2000). PLV also gives superior alveolar recruitment in the dependent areas of the lung and redistributes pulmonary blood flow to improve V/Q matching and decrease intrapulmonary shunting (Davies 1999; Wiedemann 2000). PFCs have also been demonstrated to have significant anti-inflammatory effects, in both in vivo animal models of ALI and in vitro cell cultures (Wiedemann 2000). PFCs can decrease inflammatory cytokine release and oxygen free radical production by alveolar macrophages and decrease neutrophil activation and chemotaxis (Wiedemann 2000).

Why it is important to do this review

Uncontrolled human studies using PLV in adults with ALI or ARDS have shown improvements in oxygenation and lung compliance in patients also on ECLS (Hirschl 1996), and improved gas exchange with haemodynamic stability and minimal adverse side effects in patients ventilated with PLV alone (Hirschl 1998). The efficacy of PLV in adults has been assessed in a separate Cochrane systematic review (Davies 2004a) and there is no evidence from randomized controlled trials to support or refute the use of PLV in adults with ALI or ARDS. A single uncontrolled study in six children with ARDS showed some improvement in gas exchange with three hours of PLV (Fedora 1999a). The optimal dose of PFC to use during PLV is unknown and its beneficial effects may be apparent at lower doses of PFC than the usual method where the initial dose of PFC is equivalent to the functional residual capacity (approximately 30 ml/kg). Variations in the technique of PLV may also include giving an initial dose of PFC with or without further top-up doses to maintain partial filling of the lungs (Davies 1999).

Objectives

The primary objective was to assess whether PLV reduces mortality or duration of mechanical ventilation, or both, in children with ALI or ARDS.

Methods

Criteria for considering studies for this review

Types of studies

We included randomized controlled trials (RCTs). We excluded cross-over studies due to their inability to determine differences for clinically relevant medium- to long-term outcomes.

Types of participants

We included children from the age of 28 days to 18 years with ALI or ARDS from any cause who were intubated and being supported by a mechanical ventilator.

Definition of ALI (Bernard 1994):

  1. acute onset respiratory failure;

  2. bilateral opacities on chest x-ray consistent with pulmonary oedema;

  3. pulmonary artery wedge pressure less than 18 mm Hg or no clinical evidence of raised left atrial pressure;

  4. partial pressure of oxygen (PaO2) to fraction of inspired oxygen (FiO2) ratio less than or equal to 300 mm Hg.

Definition of ARDS (Bernard 1994):

  1. acute onset respiratory failure;

  2. bilateral opacities on chest x-ray consistent with pulmonary oedema;

  3. pulmonary artery wedge pressure less than or equal to 18 mm Hg or no clinical evidence of raised left atrial pressure;

  4. PaO2/FiO2 ratio less than or equal to 200 mm Hg.

Types of interventions

Partial liquid ventilation (PLV), partially filling the lungs with perfluorocarbon (PFC) whilst continuing mechanical ventilation with a gas ventilator, compared with other forms of ventilatory management without the use of PFC liquids or vapour.

Types of outcome measures

One or more of the following outcomes must have been reported.

Primary outcomes
  1. Mortality (28-day, or at discharge from ICU, at discharge from hospital, at 1, 2, and 5 years)

  2. Duration of mechanical ventilation

Secondary outcomes
  1. Duration of respiratory support

  2. Duration of oxygen therapy

  3. Duration of stay in the intensive care unit (ICU)

  4. Duration of stay in hospital

  5. Infection (septicaemia, pneumonia)

  6. Long-term cognitive impairment

  7. Long-term neurodevelopment (cerebral palsy, sensorineural hearing loss, visual impairment, developmental delay)

  8. Long-term disability

  9. Long-term health-related quality of life

  10. Long-term lung function

  11. Cost

Search methods for identification of studies

The original review (Davies 2004b) searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2003, Issue 2); MEDLINE (1966 to April 2003), CINAHL (1982 to April 2003), intensive care journals and conference proceedings; reference lists and 'grey literature' for RCTs of PLV in ALI or ARDS. Without language restrictions, we updated the search using the following databases.

Electronic searches

  • CENTRAL (The Cochrane Library 2011, Issue 11) (see Appendix 1)

  • Ovid MEDLINE (1950 to November 2011) (with Daily Update) (see Appendix 2)

  • Ovid EMBASE (1982 to November 2011) (see Appendix 3)

  • SilverPlatter CINAHL (1982 to November 2011) (see Appendix 4)

Searching other resources

  • Google Scholar.

  • Clinical trial registries:

    • Clinicaltrials.gov;

    • World Health Organization (WHO) International Clinical Trials Registry Platform;

    • Current controlled trials: MetaRegisters of controlled trials; International Standard Randomised Controlled Trial Number (ISRCTN) Register;

    • CenterWatch;

    • International Federation of Pharmaceutical Manufacturers & Associations (IFPMA) Clinical Trials Portal.

Data collection and analysis

Selection of studies

The two authors worked independently to search for and assess trials for inclusion and their methodological quality. We resolved differences by discussion and consensus of the authors.

Data extraction and management

Data were extracted independently by the authors. We resolved differences by discussion and consensus. If necessary, we contacted investigators for additional information or data.

Assessment of risk of bias in included studies

We assessed studies using the Cochrane risk of bias instrument (Higgins 2011): 1) randomization, 2) allocation concealment, 3) blinding, and 4) missing participant data. Each were rated as being either adequate, unclear, or inadequate. At least two criteria must have been rated as adequate for the study to be included in the review.

Measures of treatment effect

Dichotomous data were presented as relative risks, and continuous data as weighted mean differences, along with their corresponding 95% confidence intervals.

Unit of analysis issues

To avoid unit of analysis errors, if included studies had more than two study arms we planned to either combine relevant groups to create a single pair-wise comparison or, if not possible, select one pair of interventions and exclude the others.

Assessment of heterogeneity

We planned to assess heterogeneity using the I2 statistic. In the case of high heterogeneity, subgroup analysis was planned (see below).

Assessment of reporting biases

For included studies, if the study protocol was available we assessed if the study’s pre-specified (primary and secondary) outcomes of interest had been reported in the pre-specified way. Patient reported outcomes were considered to be more subjective and more prone to bias. If a protocol was not available, we considered the potential for reporting bias to be unclear.

Data synthesis

Results were combined unless diversity (clinical or statistical heterogeneity) suggested combination was unreasonable. Dichotomous data were presented as relative risks, and continuous data as weighted mean differences, along with their corresponding 95% confidence intervals.

Subgroup analysis and investigation of heterogeneity

Subgroup analyses were planned to determine whether the results differed in the following.

Population:

  1. age;

  2. severity of: a) overall illness (e.g. APACHE or SAPS score), or b) ALI or ARDS;

  3. aetiology of ALI or ARDS (e.g. septicaemia, pneumonia, trauma, burns).

Mortality and other outcomes have been shown to vary with the age of the patient, the initial severity of the ALI or ARDS, or patient condition (for example by APACHE score), and by the underlying cause of the ALI or ARDS (Monchi 1998; Suntharalingam 2001; Ware 2000).

Intervention:

  1. initial amount or dose of PFC;

  2. whether PLV was continuous or in intermittent doses;

  3. type of PFC (e.g. perflubron, Rimar).

The correct dose of PFC to use when initiating PLV is unknown. Variations in the technique of PLV may also include giving an initial dose of PFC with or without further top-up doses to maintain partial filling of the lungs. Various types of PFC with different physical and chemical properties may be used (Davies 1999).

Co-interventions:

  1. use of inhaled nitric oxide;

  2. use of surfactant;

  3. use of the prone position;

  4. high frequency ventilation.

Whilst the mainstay of treatment of ALI or ARDS is mechanical ventilation, additional therapies have been considered and some of these have been subjected to randomized controlled trials. Adjuncts to mechanical ventilation have included inhaled nitric oxide, endogenous surfactant, prone positioning, and high frequency ventilation (Conner 2000); all can be used in conjunction with PLV.

Sensitivity analysis

If two or more trials were included, we planned to pool the results using both a random-effects and fixed-effect model.

Results

Description of studies

Eleven reports of nine studies were initially located by the original search strategy. Eight of the studies were excluded (see Characteristics of excluded studies). There were no disagreements between authors.

Only one study (Fuhrman 1998) was identified and found eligible for inclusion in this review. It has only been reported as an abstract in conference proceedings. We have contacted the first author of this study and the company that sponsored it but no further information and data were forthcoming from either source.

The study ran from January 1996 to April 1997 and enrolled 182 patients in 65 centres. At enrolment, patients were allocated to receive either PLV (N = 91) or conventional mechanical ventilation (control group, N = 91). The study was complicated by the fact that entry criteria, the use of other rescue therapies, and the primary outcome were modified at least twice during the study. These modifications included liberalization of the entry criteria and allowed use of adjunct therapies in the control group, such as high frequency ventilation or inhaled nitric oxide, or both. The study was stopped well short of the expected recruitment (less than 20%) because of an "abrupt decline" in mortality in the control group. Mortality at 28 days was 22% in the PLV group and 14% in the control group, but this difference did not reach statistical significance. It is not clear why the study did not continue thereafter. Other outcomes reported for PLV versus control were: overall mortality (not defined) 26% versus 20%; 28-day respiratory mortality 10% versus 10%; ventilator free days (not defined) 10.1 versus 12.4; and air leak 33% versus 30%. None of these outcomes showed statistically significant differences.

Results of the search

The updated search was conducted in November 2011. Out of 58 studies identified from the primary electronic databases (MEDLINE 15, EMBASE 42, CENTRAL 0, CINAHL 1) 12 were duplicates, leaving 46 abstracts or titles identified as original publications. Of these, 16 proved potentially relevant for full text review but after independent review no article met our eligibility criteria (Figure 1).  The grey literature search identified one potentially relevant title and abstract but it was found to be ineligible after full text review.

Figure 1.

Flow diagram.

Included studies

The original review had one study which fulfilled the inclusion criteria (Fuhrman 1998).

Excluded studies

The following studies were excluded from the original review:

The update search excluded 16 studies, none of which were RCTs.

Risk of bias in included studies

The study by Fuhrman et al was reported in abstract form only (Fuhrman 1998).

Allocation

  • Treatment allocation was randomized (exact method not stated)

  • Whether allocation was adequately concealed is unknown

Blinding

  • Treatment was not blinded

  • Whether the published outcomes were assessed by blinded evaluators is unknown (blinding of the assessment of death was not applicable)

Incomplete outcome data

  • Follow-up rate was not reported

Selective reporting

  • Unclear, as the included study was an abstract and we were unable to locate a protocol

Other potential sources of bias

The fact that entry criteria, use of other rescue therapies, and the primary outcome were modified at least twice during the study, and that these were not adequately described in the abstract, made it difficult to assess the impact of the modifications on the quality of the available data.

Also, each study centre enrolled an average of only 2.8 patients into the study (182 patients in 65 centres); many of these centres would have enrolled only one or two patients into the study and many would have only treated one child with PLV. This may have led to wide variation in the application of PLV, the success of which may well be determined, in part, by how the PLV was applied.

Effects of interventions

Limited results were available from only one study (Fuhrman 1998) which was stopped prematurely. The only outcome of clinical significance that was available from the only published report of this trial was 28-day mortality. Although it was not reported, we assumed 100% follow up for analysis of this short-term outcome. There was no statistically significant difference between groups for this outcome, with a relative risk for 28-day mortality in the PLV group of 1.54 (95% confidence interval 0.82 to 2.9).

Discussion

While it has been suggested that PLV is a promising alternative mode of mechanical ventilation for children with ALI or ARDS, there are no available data from adequately powered RCTs to determine whether PLV is effective, or not, in decreasing morbidity or mortality.

Summary of main results

The study by Fuhrman et al (Fuhrman 1998) was stopped prematurely and was, therefore, under-powered to detect any significant differences. The wide 95% confidence interval for 28-day mortality meant that a clinically significant difference cannot be excluded.

Overall completeness and applicability of evidence

It is unfortunate that the only RCT done so far to investigate PLV in children with ALI or ARDS (Fuhrman 1998) has not been published in full or that data on more clinically relevant outcomes (especially mortality at discharge and later, duration of both respiratory support and hospital stay, and long-term neurodevelopmental outcomes) are not forthcoming from the study investigators or the company that sponsored the trial.

Quality of the evidence

The limited information available from the published abstract of this study makes it difficult to do a complete assessment of study quality.

Potential biases in the review process

The under-reporting of RCTs due to publication bias has been well described (Dickersin 1987; Dickersin 1990; Dickersin 1993). In a systematic review of pharmaceutical industry sponsorship and research outcomes, Lexchin et al (Lexchin 2003) found that research funded by drug companies was less likely to be published. Some people consider the selection of reports for publication on the basis of 'positive results' or the failure of investigators to publish results with sufficient detail to allow judgments to be made about their validity as scientific misconduct (Chalmers 1990). It is unknown whether any of these factors are operating here.

Authors' conclusions

Implications for practice

There is extremely limited evidence to support or refute the use of PLV in children with ALI or ARDS.

Implications for research

If children with ALI or ARDS are to be treated with PLV then adequately powered, high quality RCTs are still needed to assess its efficacy. Clinically relevant outcome measures should be assessed (especially mortality at discharge and later, duration of both respiratory support and hospital stay, and long-term neurodevelopmental outcomes) and the studies should be published in full.

Acknowledgements

We would like to thank and acknowledge Dr Bradley Johnston for providing methodological support and Dr Iris Henzi for screening the titles and abstracts. The authors of the original review (Davies 2004b) wish to thank Janet Wale for helping to write the plain language summary. The following reviewed and commented on the first version of this review (Davies 2004b) prior to its initial publication and their input is acknowledged: Dr Mike Bennett, Prof Nathan Pace, Dr John Carlisle, Dr Maureen Meade, Janet Wale, and Nete Villebro.

We would like to thank Philip H Sargent for his contribution to the original published review (Davies 2004b).

Data and analyses

Download statistical data

Comparison 1. Partial liquid ventilation versus conventional mechanical ventilation
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 28 day mortality1 Risk Ratio (M-H, Random, 95% CI)Totals not selected
Analysis 1.1.

Comparison 1 Partial liquid ventilation versus conventional mechanical ventilation, Outcome 1 28 day mortality.

Appendices

Appendix 1. Search strategy for CENTRAL,The Cochrane Library

#1 MeSH descriptor Respiratory Distress Syndrome, Newborn explode all trees
#2 MeSH descriptor Respiratory Distress Syndrome, Adult explode all trees
#3 ARDS or ALI
#4 acute lung injur*
#5 (#1 OR #2 OR #3 OR #4)
#6 MeSH descriptor Liquid Ventilation explode all trees
#7 MeSH descriptor Fluorocarbons explode all trees
#8 FLUOROCARBON* or partial liquid ventilation
#9 (#6 OR #7 OR #8)
#10 (#5 AND #9)

Appendix 2. Search strategy for Ovid MEDLINE

#1 (explode "Respiratory-Distress-Syndrome-Newborn" / all SUBHEADINGS in MIME,MJME,PT) or (explode "Respiratory-Distress-Syndrome-Adult" / all SUBHEADINGS in MIME,MJME,PT)

#2 ARDS or ALI or (acute near(lung injur*))

#3 FLUOROCARBON* or partial liquid ventilation

#4 (explode "Liquid-Ventilation" / all SUBHEADINGS in MIME,MJME,PT) or (explode "Fluorocarbons-" / all SUBHEADINGS in MIME,MJME,PT)

#5 (#1 or #2) and (#3 or #4)

#6 (randomized controlled trial.pt. or controlled clinical trial.pt. or randomized.ab. or placebo.ab. or drug therapy.fs. or randomly.ab. or trial.ab. or groups.ab.) and humans.sh.

#7 #5 and #6

Appendix 3. Search strategy for Ovid EMBASE

#1 (explode "respiratory-distress-syndrome" / all SUBHEADINGS in DEM,DER,DRM,DRR) or (explode "respiratory-distress" / all SUBHEADINGS in DEM,DER,DRM,DRR)

#2 explode "acute-lung-injury" / all SUBHEADINGS in DEM,DER,DRM,DRR

#3 RESPIRATORY DISTRESS SYNDROME or ARDS or ALI or (acute near (lung injur*))

#4 #1 or #2 or #3

#5 explode "fluorocarbon-" / all subheadings

#6 explode "liquid-ventilation"/ all subheadings

#7 fluorocarbon* or (liquid near ventilation)

#8 #5 or #6 or #7

#9 #4 and #8

#10 "RANDOMIZED-CONTROLLED-TRIAL"/ all subheadings

#11 "RANDOMIZATION"/ all subheadings

#12 "CONTROLLED-STUDY"/ all subheadings

#13 "MULTICENTER-STUDY"/ all subheadings

#14 "PHASE-3-CLINICAL-TRIAL"/ all subheadings

#15 "PHASE-4-CLINICAL-TRIAL"/ all subheadings

#16 "DOUBLE-BLIND-PROCEDURE"/ all subheadings

#17 "SINGLE-BLIND-PROCEDURE"/ all subheadings

#18 #10 or #11 or #12 or #13 or #14 or #15 or #16 or #17

#19 (RANDOM* or CROSS?OVER* or FACTORIAL* or PLACEBO* or VOLUNTEER*) in TI,AB

#20 (SINGL* or DOUBL* or TREBL* or TRIPL*) near ((BLIND* or MASK*) in TI,AB)

#21 #18 or #19 or #20

#22 HUMAN in DER

#23 (ANIMAL or NONHUMAN) in DER

#24 #22 and #23

#25 #23 not #24

#26 #21 not #25

#27 #9 and #26

Appendix 4. Search strategy for CINAHL

#1 (explode "Respiratory-Distress-Syndrome" / all TOPICAL SUBHEADINGS / all AGE SUBHEADINGS in DE) or (explode "Respiratory-Distress-Syndrome-Acute" / all TOPICAL SUBHEADINGS / all AGE SUBHEADINGS in DE)

#2 RESPIRATORY DISTRESS SYNDROME

#3 ARDS or ALI or (acute near (lung injur*))

#4 FLUOROCARBON* or liquid ventilation

#5 explode "Ventilation-Liquid" / all TOPICAL SUBHEADINGS / all AGE SUBHEADINGS in DE

#6 (#1 or #2 or #3) and (#4 or #5)

#7 PLACEBO* or random* or trial* or control* or compar* or blind*

#8 #6 and #7

What's new

Last assessed as up-to-date: 28 November 2011.

DateEventDescription
5 December 2012New citation required but conclusions have not changedTwo new authors, Alka Kaushal and Conor G McDonnell, joined the team to update the review. Philip H Sargent (Davies 2004b) did not contribute to the updated review.
5 December 2012New search has been performedThis review is an update of the previous Cochrane systematic review (Davies 2004b) that included one RCT. We have rerun the search until November 2011. No new studies were found.

History

Protocol first published: Issue 4, 2002
Review first published: Issue 2, 2004

DateEventDescription
2 February 2009New search has been performedNew search; no new studies found
1 August 2008AmendedConverted to new review format.
23 July 2004New citation required and conclusions have changedSubstantive amendment

Contributions of authors

Conceiving and writing the original review: Mark Davies, Philip Sargent

Co-ordinating the review: Bradley Johnston and Alka Kaushal

Undertaking electronic searches: Alka Kaushal

Screening search result: Conor McDonnell, Alka Kaushal, Iris Henzi

Screening retrieved papers against inclusion criteria: Alka Kaushal

Obtaining and screening data on unpublished studies: Alka Kaushal

Entering data into Review Manager (RevMan 5.1): Alka Kaushal

Writing the review update: Alka Kaushal

Person responsible for reading and checking review before submission: Bradley Johnston, Conor McDonnell, Alka Kaushal

Further contributions for the original review can be found at Davies 2004b

Declarations of interest

Alka Kaushal: none known

Mark W Davies: none known

Conor G McDonnell: I am a non-paid consultant for Institute for Safe Medication Practices, Canada with regards to Pediatric Opioid Safety and national pediatric opioid recommendations.

Sources of support

Internal sources

  • Grantley Stable Neonatal Unit, Royal Women's Hospital, Brisbane, Australia.

  • Dept of Paediatrics and Child Health, University of Queensland, Brisbane, Australia.

  • Mater Children's Hospital, Brisbane, Australia.

External sources

  • No sources of support supplied

Differences between protocol and review

None

Notes

None

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Fuhrman 1998

Methods

RCT

method of randomization - unknown

allocation concealment - unknown

Participants

182 "paediatric patients" with ARDS

all had PaO2/FiO2 ratio <200mmHg with bilateral infiltrates

there were three enrolment periods which differed in the "entry criteria, use of rescue therapies and primary outcome endpoint"

Interventions

control group - conventional mechanical ventilation (and/or HFOV)

treatment group - partial liquid ventilation

during 3rd enrolment period HFOV and/or iNO were allowed, though not during PLV

it is unknown whether children in the control group would have had HFOV/NO whilst in the study when children in the PLV group would not have had these treatments

Outcomes28-day mortality
overall mortality
28-day respiratory mortality
ventilator free days
air leak
Notes 
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskRandomized, but exact method not stated
Allocation concealment (selection bias)Unclear riskUnknown
Blinding (performance bias and detection bias)
All outcomes
High risk

Treatment not blinded

Whether the published outcomes were assessed by blinded evaluators is unknown (blinding of the assessment of death is not applicable)

Incomplete outcome data (attrition bias)
All outcomes
Unclear riskFollow up not stated
Selective reporting (reporting bias)Unclear riskAs included study is an abstract
Other biasHigh risk

Trial was stopped prematurely

Entry criteria, use of other rescue therapies, and the primary outcome were modified at least twice during the study

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion
Fedora 1999No control group, not randomized
Gauger 1996No control group, not randomized
Gentili 2000No control group, not randomized
Greenspan 1997No control group, not randomized
Hirschl 1995No control group, not randomized
Meaney 1997No control group, not randomized
Nekvasil 1996No control group, not randomized
Toro-Figueroa 1996No control group, not randomized