Perfluorocarbon broncho-alveolar lavage and liquid ventilation versus saline broncho-alveolar lavage in adult guinea pig experimental model of meconium inhalation

Lung lavage for meconium aspiration syndrome in newborn infants

BACKGROUND

Meconium aspiration syndrome (MAS) can occur when a newborn infant inhales a mixture of meconium and amniotic fluid into the lungs around the time of delivery. Other than supportive measures, little effective therapy is available. Lung lavage may be a potentially effective treatment for MAS by virtue of removing meconium from the airspaces and altering the natural course of the disease.

OBJECTIVES

To evaluate the effects of lung lavage on morbidity and mortality in newborn infants with MAS.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, and EMBASE up to December 2012; previous reviews including cross-references, abstracts, and conference proceedings; and expert informants. We contacted authors directly to obtain additional data. We used the following subject headings and text words: meconium aspiration, pulmonary surfactants, fluorocarbons, bronchoalveolar lavage, lung lavage, pulmonary lavage.

SELECTION CRITERIA

Randomised controlled trials that evaluated the effects of lung lavage in infants with MAS, including those intubated for the purpose of lavage. Lung lavage was defined as any intervention in which fluid is instilled into the lung that is followed by an attempt to remove it by suctioning and/or postural drainage.

DATA COLLECTION AND ANALYSIS

The review authors extracted from the reports of the clinical trial, data regarding clinical outcomes, including mortality, requirement for extracorporeal membrane oxygenation (ECMO), pneumothorax, duration of mechanical ventilation and oxygen therapy, length of hospital stay, indices of pulmonary function, and adverse effects of lavage. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Only four small randomised controlled trials fulfilled the selection criteria. For one of these trials, no data are available for the control group. Two studies compared lavage using diluted surfactant with standard care. Meta-analysis of these two studies did not show a significant effect on mortality (typical relative risk 0.42, 95% confidence interval [CI] 0.12 to 1.46; typical risk difference -0.10, 95% CI -0.24 to 0.04) or the use of ECMO (typical relative risk 0.27, 95% CI 0.04 to 1.86; typical risk difference -0.15, 95% CI -0.35 to 0.04). For the composite outcome of death or use of ECMO, a significant effect favoured the lavage group (typical relative risk 0.33, 95% CI 0.11 to 0.96; typical risk difference -0.19, 95% CI -0.34 to -0.03; number needed to benefit [NNTB] 5). No other benefits were reported. The other published study compared surfactant lavage followed by a surfactant bolus with surfactant bolus therapy alone in MAS complicated by pulmonary hypertension. No significant improvements in mortality, pneumothorax, duration of mechanical ventilation. or duration of hospitalisation were observed.

AUTHORS' CONCLUSIONS

In infants with meconium aspiration syndrome, lung lavage with diluted surfactant may be beneficial, but additional controlled clinical trials of lavage therapy should be conducted to confirm the treatment effect, to refine the method of lavage treatment, and to compare lavage treatment with other approaches, including surfactant bolus therapy. Long-term outcomes should be evaluated in further clinical trials.

Comparative effects of bronchoalveolar lavage with saline, surfactant, or perfluorocarbon in experimental meconium aspiration syndrome

OBJECTIVE

Today, in meconium aspiration syndrome, treatment focuses on bronchoalveolar lavage, because it removes meconium and proinflammatory factors from airways. This technique might be more effective if different solutions were used such as saline solution, a protein-free surfactant, or a perfluorocarbon, because these would be less inhibited by meconium proteins.

SETTING

Pulmonary physiology research unit, Cruces Hospital.

DESIGN

Prospective, randomized study.

SUBJECTS

We studied 24 lambs (<6 days) on mechanical ventilation for 180 mins. Catheters were placed and femoral and pulmonary arteries pressures registered (systemic and pulmonary arterial pressures).

INTERVENTIONS

Lambs were instilled with 20% meconium (3-5 mL/Kg) and were randomly assigned to one of the following groups (n = 6): control: only continuous mechanical ventilation; saline bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of saline solution; dilute surfactant bronchoalveolar lavage: bronchoalveolar lavage with 32 mL/kg of diluted surfactant (lucinactant, 10 mg/mL); or perfluorocarbon bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of perfluorocarbon.

MEASUREMENTS AND MAIN RESULTS

Blood gases, cardiovascular parameters, and pulmonary mechanics were assessed. Meconium instillation produced severe hypoxia, hypercapnia, acidosis, and pulmonary hypertension with impairment of pulmonary mechanics (p < .05). Lung lavage with dilute surfactant resulted in the resolution of pulmonary hypertension as well as better gas exchange and pulmonary mechanics than the control group (p < .05). Bronchoalveolar lavage with perfluorocarbon produced a transient improvement in gas exchange and ventilatory indices in comparison with control and saline bronchoalveolar lavage groups.

CONCLUSIONS

In lambs with meconium aspiration syndrome, bronchoalveolar lavage with diluted lucinactant is an effective therapy producing significant improvements in gas exchange, pulmonary hypertension, and pulmonary mechanics. In addition, bronchoalveolar lavage with perfluorocarbon appears to confer some advantages over lavage with equal volumes of saline or no lavage.

Measurement of fractional order model parameters of respiratory mechanical impedance in total liquid ventilation

This study presents a methodology for applying the forced-oscillation technique in total liquid ventilation. It mainly consists of applying sinusoidal volumetric excitation to the respiratory system, and determining the transfer function between the delivered flow rate and resulting airway pressure. The investigated frequency range was f ∈ [0.05, 4] Hz at a constant flow amplitude of 7.5 mL/s. The five parameters of a fractional order lung model, the existing "5-parameter constant-phase model," were identified based on measured impedance spectra. The identification method was validated in silico on computer-generated datasets and the overall process was validated in vitro on a simplified single-compartment mechanical lung model. In vivo data on ten newborn lambs suggested the appropriateness of a fractional-order compliance term to the mechanical impedance to describe the low-frequency behavior of the lung, but did not demonstrate the relevance of a fractional-order inertance term. Typical respiratory system frequency response is presented together with statistical data of the measured in vivo impedance model parameters. This information will be useful for both the design of a robust pressure controller for total liquid ventilators and the monitoring of the patient's respiratory parameters during total liquid ventilation treatment.

Selective medicated (saline + natural surfactant) bronchoalveolar lavage in unilateral lung contusion. A clinical randomized controlled trial

OBJECTIVE

Open lung and low tidal volume ventilation appear to be a promising ventilation for chest trauma as it can reduce ARDS and improve outcome. Local therapy (e.g. BAL) can be synergic to remove from the lung the debris, mitigate inflammatory cascade and avoid damage spreading to not compromised lung areas.

MATERIALS AND METHODS

44 pulmonary contused patients were randomized to receive broncho-suction and volume controlled low tidal volume ventilation-VCLTVV (Control Group) or the same ventilation plus medicated (saline + surfactant) BAL (Treatment Group). Tidal volume <10 ml/kg, PEEP of 10-12 cm H(2)O and PaO(2) 60-100 mm Hg and PaCO(2) 35-45 mm Hg were used in both groups. BAL was performed using a fiberscope. 4 boluses of 25 ml saline with 2.4 mg/ml of surfactant were introduced into each contused lobe in which, subsequently, 240 mg of surfactant was instilled.

RESULTS

All patients survived. In the Control Group 18 patients developed pneumonia, 5 ARDS and days of intubation were 11.50 (3.83) compared to 5.05 (1.21) of Treatment Group in which OI and PaO(2)/FiO(2) significantly improved from 36 h.

CONCLUSIONS

VCLTVV alone was not able to prevent ARDS and infection in the Control Group as the reduction of intubation. In the Treatment Group, VCLTVV and medicated BAL facilitated the removal of degradated lung material and recruited the contused lung regions, enabling the healing of the lung pathology.

Therapeutic lung lavage with diluted surfactant in neonates with severe meconium aspiration syndrome

Meconium aspiration syndrome (MAS) may result in considerable morbidity and mortality in newborn infants. The current standard treatment is still in need of improvement for the most severe patients. We report 3 cases with devastating MAS that was successfully treated with therapeutic lung lavage. These cases were all delivered in local obstetrics clinics or hospitals with meconium-stained amniotic fluid and non-vigorous appearance at birth. However, no endotracheal suction was performed when they were born. All of them suffered from severe hypoxia and unstable vital signs despite there being high ventilatory settings when they were transferred to the tertiary medical center. Therapeutic lung lavage with diluted surfactant (Survanta, 5 mg/mL, 30 mL/kg in 2 aliquots) was performed within 24 hours of age. Bloody fluid (about 40-50% of total lavage amount) was recovered in all 3 cases. Although brief desaturation and bradycardia were observed during the procedures, 2 of them tolerated the procedures well and improved soon after lavage. The other patient received lung lavage in a relatively unstable condition and needed chest tapping to relieve bilateral pleural effusion. Their respiratory condition improved after the procedures, and they were all discharged within 1 month without major respiratory complications. These successful experiences are compatible with previous animal studies and other case reports with different lavage protocols. We conclude that therapeutic lung lavage may improve the outcome in newborn infants with severe MAS, and there were no significant adverse side effects observed. Before performing lung lavage, stabilization and optimal support may prevent unexpected results during and after lavage.

Selective medicated (normal saline and exogenous surfactant) bronchoalveolar lavage in severe aspiration syndrome in children

OBJECTIVE

To study the ability of volume-controlled ventilation and medicated (normal saline plus surfactant) bronchoalveolar lavage in aspiration to reduce the duration of intubation and improve gas exchange.

DESIGN

: Randomized controlled clinical trial.

SETTING

Pediatric intensive care unit.

PATIENTS

Twenty children, 1 month to 16 yrs old, who were intubated and mechanically ventilated, were randomized within 6 hrs of aspiration to receive volume-controlled ventilation plus medicated bronchoalveolar lavage (treatment group) or the same ventilation and bronchosuction (control group).

INTERVENTIONS

Volume-controlled ventilation and positive end-expiratory pressure (10-12 cm H2O) were applied. Medicated bronchoalveolar lavage was performed using five aliquots of 5 mL of saline plus 10 mg/mL Curosurf (porcine surfactant, Chiesi Pharmaceutical SpA, Parma, Italy) in infants, five boluses of 10 mL of saline plus 5 mg/mL Curosurf in children, and four boluses of 25 mL of saline with 2.4 mg/mL Curosurf in adolescents for each affected lobe. One hour after bronchoalveolar lavage, 240 mg of Curosurf was administered locally.

MEASUREMENTS AND MAIN RESULTS

All patients survived. In the treatment group, days of intubation were 4.6 (+/-1.07), oxygenation index and Pao2/Fio2 improved significantly at 24 hrs, and statistical reduction in tidal volume mL/kg was observed from 36 hrs. In the control group, days of intubation were 11.8 (+/-3.22) (p < .0001), no improvement in oxygenation was noted, and pneumonia was observed in seven children (70%).

CONCLUSIONS

Even though this was an unblinded small clinical trial and low tidal volume strategy was not employed at an early stage after lung injury, there is some evidence that bronchoalveolar lavage with normal saline and surfactant may have clinical value in treating severe aspiration syndrome in children. More clinical studies are warranted to overcome study limitations and potential bias.

Effects of therapeutic bronchoalveolar lavage and partial liquid ventilation on meconium-aspirated newborn piglets

OBJECTIVE

To investigate the therapeutic effects of bronchoalveolar lavage (BAL) with either diluted surfactant (SBAL) or perfluorochemical liquid (PBAL), followed by either conventional mechanical ventilation (CMV) or partial liquid ventilation (PLV), on lung injury and proinflammatory cytokine production induced by meconium aspiration in newborn piglets.

DESIGN

A prospective, randomized, experimental study.

SETTING

An animal research laboratory at a medical center.

SUBJECTS

Anesthetized and mechanically ventilated newborn piglets (n = 27).

INTERVENTIONS

The animals were instilled with 3-5 mL/kg 25% human meconium via an endotracheal tube to induce meconium aspiration syndrome (MAS). After stabilization, animals were randomly assigned to either CMV group (no BAL) or one of the treatment groups (SBAL-CMV, SBAL-PLV, PBAL-CMV, and PBAL-PLV).

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary variables were monitored, and interleukin-1beta and interleukin-6 content of the serum and lung tissue was measured. The animals without any treatment (CMV group) displayed the worst outcome; the animals in the PBAL-PLV group had the best gas exchange, lung compliance, and least pulmonary damage; and the SBAL-CMV, PBAL-CMV, and SBAL-PLV groups had intermediate effects. The serum interleukin-1beta concentration of the CMV group was significantly higher than all other groups over time (p < .05), and interleukin-6 concentration was significantly higher than the PBAL-PLV group (p < .05). The tissue interleukin-1beta and interleukin-6 contents were also highest in the CMV group and lowest in the PBAL-PLV group.

CONCLUSIONS

Initial therapeutic BAL and therapeutic BAL followed by PLV with the same perfluorochemical liquid provided significant therapeutic effects in treating an animal model with severe MAS and therefore warrant consideration in cases that are intractable to other therapies.

Novas opções terapêuticas na síndrome de aspiração de mecônio

OBJETIVOS: revisar a literatura sobre a síndrome de aspiração de mecônio (SAM), enfocando aspectos clínicos, fisiopatológicos e abordagem terapêutica, com destaque ao uso do surfactante e lavado broncoalveolar. MÉTODOS: revisão baseada em artigos publicados na MEDLINE, SCIELO e resumos de congressos internacionais de 1988 a 2004, incluindo ensaios randomizados ou quasi-randomizados, estudos caso-controle e metanálises. RESULTADOS: devido à comprovação da inibição do surfactante na SAM, houve modificações em sua abordagem terapêutica. O manejo atual consiste na aspiração das vias aéreas na sala de parto, seguida de suporte ventilatório necessário para manter a oxigenação arterial adequada, e tratamento das complicações. Tendo em vista a obstrução mecânica do mecônio e seu efeito inibitório sobre o surfactante, a reposição e lavado broncoalveolar com surfactante estão sendo estudados atualmente. CONCLUSÕES: estudos em animais e em recém-nascidos apresentam resultados controversos quanto aos benefícios do uso de surfactante e lavado broncoalveolar na SAM. Torna-se importante a realização de mais estudos para avaliar novas estratégias ventilatórias e se existem vantagens no uso do surfactante e lavado broncoalveolar com surfactante na SAM.

Pulmonary applications of perfluorochemical liquids: ventilation and beyond

In this review of liquid ventilation, concepts and applications are presented that summarise the pulmonary applications of perfluorochemical liquids. Beginning with the question of whether this alternative form of respiratory support is needed and ending with lessons learned from clinical trials, the various methods of liquid assisted ventilation are compared and contrasted, evidence for mechanoprotective and cytoprotective attributes of intrapulmonary perfluorochemical liquid are presented and alternative intrapulmonary applications, including their use as vehicles for drugs, for thermal control and as imaging agents are presented.

Surfactant Therapy for Meconium Aspiration Syndrome

Meconium aspiration syndrome (MAS) is an important cause of respiratory distress in the term infant. Therapy for the disease remains problematic, and newer treatments such as high-frequency ventilation and inhaled nitric oxide are being applied with increasing frequency. There is a significant disturbance of the pulmonary surfactant system in MAS, with a wealth of experimental data indicating that inhibition of surfactant function in the alveolar space is an important element of the pathophysiology of the disease. This inhibition may be mediated by meconium, plasma proteins, haemoglobin and oedema fluid, and, at least in vitro, can be overcome by increasing surfactant phospholipid concentration. These observations have served as the rationale for administration of exogenous surfactant preparations in MAS, initially as standard bolus therapy and, more recently, in association with therapeutic lung lavage. Bolus surfactant therapy in ventilated infants with MAS has been found to improve oxygenation in most studies, although there are a significant proportion of nonresponders and in many cases the effect is transient. Pooled data from randomised controlled trials of surfactant therapy suggest a benefit in terms of a reduction in the requirement for extracorporeal membrane oxygenation (relative risk 0.48 in surfactant-treated infants) but no diminution of air leak or ventilator days. Current evidence would support the use of bolus surfactant therapy on a case by case basis in nurseries with a relatively high mortality associated with MAS, or the lack of availability of other forms of respiratory support such as high-frequency ventilation or nitric oxide. If used, bolus surfactant should be administered as early as practicable to infants who exhibit significant parenchymal disease, at a phospholipid dose of at least 100 mg/kg, rapidly instilled into the trachea. Natural surfactant or a third-generation synthetic surfactant should be used and the dosage repeated every 6 hours until oxygenation has improved. Lung lavage with dilute surfactant has recently emerged as an alternative to bolus therapy in MAS, which has the advantage of removing surfactant inhibitors from the alveolar space in addition to augmenting surfactant phospholipid concentration. Combined animal and human data suggest that lung lavage can remove significant amounts of meconium and alveolar debris, and thereby improve oxygenation and pulmonary mechanics. Arterial oxygen saturation inevitably falls during lavage but has been noted to recover relatively rapidly, even in infants with severe disease. Several randomised controlled trials of surfactant lavage in MAS are underway, and until the results are known, lavage must be considered an unproven and experimental therapy.

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

OBJECTIVE

Partial liquid ventilation can improve respiratory functions in acid-induced lung injury. We studied the effects of the interval between induction of injury and initiation of partial liquid ventilation on survival, gas exchange, and pulmonary neutrophil accumulation.

MATERIAL AND METHODS

Anesthetized rats were randomly assigned to one of five groups ( n = 6 per group). Group 1 served as the control group, in the other groups an extended lung injury was induced by intratracheal instillation of hydrochloric acid. Whereas lungs of group 2 were gas-ventilated, group 3 received an early partial liquid ventilation (5 min after acid instillation) and group 4 a delayed partial liquid ventilation (30 min after acid instillation, 5 ml/kg perfluorocarbon). Group 5 received an additional continuous perfluorocarbon application of 5 ml x kg(-1) x h(-1) (30 min after acid instillation). Blood gases were measured with an intravascular blood gas sensor.

RESULTS

Acid instillation resulted in a marked decrease in PO(2)-values within 30 min (from 481+/-37 mmHg to 128+/-71 mmHg, FiO(2) 1.0). Survival rate of the study period (12 h) was higher with early partial liquid ventilation. We observed no differences between groups in peak PO(2)-values during treatment. Histopathological examination, however, showed less pulmonary neutrophil accumulation in lungs of the early partial liquid ventilation group when compared to the delayed partial liquid ventilation group.

CONCLUSIONS

Our results suggest that early partial liquid ventilation increases survival after extended acid-induced lung injury. While effects on arterial oxygenation appear not to predict acute survival we observed less intrapulmonary neutrophil accumulation with early partial liquid ventilation.

Comparison of aerosol therapy with different perfluorocarbons in surfactant-depleted animals

OBJECTIVE

The study investigates the effectiveness of aerosol treatment on gas exchange and pulmonary inflammatory reaction using perfluorocarbons with different molecular structure and vapor pressure.

DESIGN

Experimental, prospective, randomized, controlled study.

SETTING

Experimental laboratory at a university hospital.

SUBJECTS

Twenty anesthetized neonatal piglets assigned to four groups.

INTERVENTIONS

After establishment of lung injury by bronchoalveolar lavage, piglets either received aerosolized FC77 (n = 5), perfluorooctylbromide (n = 5), or FC43 (n = 5, 10 mL x kg(-1) x hr(-1) for 2 hrs) or intermittent mandatory ventilation (control, n = 5). Thereafter, animals were supported for another 6 hrs.

MEASUREMENTS AND MAIN RESULTS

Pao2 significantly improved in the perfluorocarbon groups compared with control (p < .01). Final Pao2 (mean +/- SEM) was FC77, 406 +/- 27 mm Hg; perfluorooctylbromide, 332 +/- 32 mm Hg; FC43, 406 +/- 19 mm Hg; control, 68 +/- 8 mm Hg. Paco2 and mean pulmonary arterial pressure were lower in all perfluorocarbon groups compared with control. The ratio of terminal dynamic compliance to total compliance was significantly higher in the FC77 than in the FC43, perfluorooctylbromide, and control groups. Relative gene expression of interleukin-1beta, interleukin-8, P-selectin, E-selectin, and intercellular adhesion molecule-1 in lung tissue was determined by TaqMan real time polymerase chain reaction normalized to hypoxanthineguanine-phosphoribosyl-transferase and was shown to be reduced by all perfluorocarbons.

CONCLUSIONS

Aerosol treatment with all the perfluorocarbons investigated improved gas exchange and reduced pulmonary inflammatory reaction independently from molecular structure and vapor pressure of the perfluorocarbons. Although differences in vapor pressure and molecular structure may account for varying optimal dosing strategies, several different perfluorocarbons were shown to be principally suitable for aerosol treatment.

Therapeutic lung lavage in the piglet model of meconium aspiration syndrome

Therapeutic lung lavage is an emerging treatment for meconium aspiration syndrome. Our objective was to investigate the type of fluid and aliquot volume most appropriate for lung lavage in this condition. Meconium injury was induced in 2-week-old piglets, followed by a 30 ml/kg lavage in two aliquots 40 minutes later. Lavage with either dilute bovine surfactant (2.5 mg/ml) or a perfluorocarbon emulsion (20% wt/vol) improved oxygenation compared with a nonlavaged control group, but only with dilute surfactant was there a sustained improvement in oxygenation (alveolar-arterial oxygen difference at 5 hours: dilute surfactant 250 mm Hg; perfluorocarbon emulsion 460 mm Hg; controls 460 mm Hg; p = 0.0031). There was histologic and biochemical evidence of decreased lung injury in the dilute surfactant group. In a further study, 30 ml/kg dilute surfactant lavage was performed 40 minutes after meconium injury using either two aliquots of 15 ml/kg, or multiple 3-ml aliquots. Aliquot volume of 15 ml/kg was associated with increased meconium removal, better post-lavage lung function, and less lung injury. Dilute surfactant lavage using two 15-ml/kg aliquots is an effective therapy in the piglet model of meconium aspiration, and should be evaluated in human infants with this condition.

Innovative practices of ventilatory support with pediatric patients

OBJECTIVES

The recognition that alveolar overdistension rather than peak inspiratory airway pressure is the primary determinant of lung injury has shifted our understanding of the pathogenesis of ventilator-induced side effects. In this review, contemporary ventilatory methods, supportive treatments, and future developments relevant to pediatric critical care are reviewed.

DATA SYNTHESIS

A strategy combining recruitment maneuvers, low-tidal volume, and higher positive end-expiratory pressure (PEEP) decreases barotrauma and volutrauma. Given that appropriate tidal volumes are critical in determining adequate alveolar ventilation and avoiding lung injury, volume-control ventilation with high PEEP levels has been proposed as the preferable protective ventilatory mode. Pressure-related volume control ventilation and high-frequency oscillatory ventilation (HFOV) have taken on an important role as protective lung strategies. Further data are required in the treatment of children, confirming the preliminary results in specific lung pathologies. Spontaneous breathing supported artificially during inspiration (pressure support ventilation) is widely used to maintain or reactivate spontaneous breathing and to avoid hemodynamic variation. Volume support ventilation reduces the need for manual adaptation to maintain stable tidal and minute volume and can be useful in weaning. Prone positioning and permissive hypercapnia have taken on an important role in the treatment of patients undergoing artificial ventilation. Surfactant and nitric oxide have been proposed in specific lung pathologies to facilitate ventilation and gas exchange and to reduce inspired oxygen concentration. Investigation of lung ventilation using a liquid instead of gas has opened new vistas on several lung pathologies with high mortality rates.

RESULTS

The conviction emerges that the best ventilatory treatment may be obtained by applying a combination of types of ventilation and supportive treatments as outlined above. Early treatment is important for the overall positive final result. Lung recruitment maneuvers followed by maintaining an open lung favor rapid resolution of pathology and reduce side effects.

CONCLUSIONS

The methods proposed require confirmation through large controlled clinical trials that can assess the efficacy reported in pilot studies and case reports and define the optimal method(s) to treat individual pathologies in the various pediatric age groups.

Airway surface liquid recovered by lavage with perfluorocarbon liquid in cats

BACKGROUND

Airway surface liquid (ASL) is difficult to sample. Lavage with an immiscible perfluorocarbon (PFC) liquid to recover ASL was evaluated in cats.

MATERIALS AND METHODS

Six wild-type cats underwent bronchoscopic lavage with a PFC (perfluorohexane), with the bronchoscope wedged in the feline equivalent of the right lower lobe. Two cats (control animals) were lavaged with a saline vehicle only. Four procedures were performed on each animal at 2-3-week intervals. Ionic composition of ASL was determined by flame photometry.

RESULTS

Cats lavaged with PFC showed significantly more acute respiratory distress than those lavaged with saline (respiratory rate following procedure: PFC, 47 +/- 5 min-1 vs. saline, 27 +/- 2 min-1, P < 0.05; O2 saturation: PFC 80 +/- 1% vs. saline, 91 +/- 1%, P < 0.01). The PFC group also had clinical evidence of chronic respiratory compromise (mean respiratory rate before next anaesthetic; PFC, 37 +/- 2 min-1 vs. saline, 20 +/- 3 min-1, P < 0.01). The PFC-lavaged lungs demonstrated persistent radiographic changes and histological evidence of small airways obstruction with distal alveolar damage. Six PFC lavages yielded ASL samples (> 100 microL) which were sufficient for analysis. Mean (+/- SEM) ionic concentrations in these samples were Na+ 157.4 +/- 14.5 mmol L-1, Cl- 150.5 +/- 16.8 mmol L-1 and K+ 10.1 +/- 1.7 mmol L-1.

CONCLUSIONS

Perfluorocarbon lavage can be used to collect unmodified ASL from the distal lung. However, repeated lavage with perfluorohexane was associated with significant pathological changes in this study.

The cardiovascular effects of partial liquid ventilation in newborn lambs after experimental meconium aspiration

OBJECTIVE

To study the effects of partial liquid ventilation with perfluorocarbon on cardiovascular function, pulmonary gas exchange, and lung mechanics in term newborn lambs with pulmonary hypertension induced by tracheal instillation of human meconium.

DESIGN

Prospective, randomized study.

SETTING

Research Unit at a university-affiliated hospital.

SUBJECTS

Twelve term newborn lambs (<6 days old).

INTERVENTIONS

Lambs were studied in two groups (n = 6): meconium aspiration (3-5 ml/kg 20% meconium solution) managed on pressure-limited conventional mechanical ventilation with or without partial liquid ventilation with perfluorocarbon.

MEASUREMENTS AND MAIN RESULTS

Heart rate, systemic and pulmonary arterial pressures, arterial pH and blood gases, cardiac output, and pulmonary mechanics were measured. Partial liquid ventilation in term newborn lambs with experimental meconium aspiration did not alter cardiovascular profile: heart rate, systemic arterial pressure, and cardiac output maintained initial values throughout the experiment. There was a significant improvement in gas exchange (oxygenation increased from values of <100 torr to 338 torr, and ventilation reached normal values in 15 mins). Dynamic compliance increased in 30 mins, reaching basal values (1.1 +/- 0.3 ml/cm H(2)O per kg). Despite the good response (blood gases and cardiovascular profile) to partial liquid ventilation in meconium aspiration syndrome, pulmonary hypertension did not decrease.

CONCLUSIONS

Partial liquid ventilation with perfluorocarbon could be a good noninvasive alternative technique that improves gas exchange and pulmonary mechanics in meconium aspiration syndrome without impairing cardiovascular function.

Persistent improvement of gas exchange and lung mechanics by aerosolized perfluorocarbon

The effect of aerosolized perfluorocarbon (PFC) (FC77) on pulmonary gas exchange and lung mechanics was studied in a surfactant depleted piglet model. Sixty minutes after induction of lung injury by bronchoalveolar lavage, 20 piglets were randomized to receive aerosolized PFC (Aerosol-PFC, 10 ml/kg/h, n = 5), partial liquid ventilation (PLV) at FRC capacity volume (FRC-PLV, 30 ml/kg, n = 5) or low volume (LV-PLV, 10 ml/kg/h, n = 5), or intermittent mandatory ventilation (IMV) (Control, n = 5). After 2 h, perfluorocarbon application was stopped and IMV was continued for 6 h. Sixty minutes after the onset of therapy, PaO2 was significantly higher and PaCO2 was significantly lower in the Aerosol-PFC and the FRC-PLV groups than in the LV-PLV and the Control groups; p < 0.001. Six hours after treatment, maximum PaO2 was found in the Aerosol-PFC group: 406.4 +/- 26.9 mm Hg, FRC-PLV: 217.3 +/- 50.5 mm Hg, LV-PLV: 96.3 +/- 18.9 mm Hg, Control: 67.6 +/- 8.4 mm Hg; p < 0.001. PaCO2 was lowest in the Aerosol-PFC group: 24.2 +/- 1.7 mm Hg, FRC-PLV: 35.9 +/- 2.8 mm Hg, LV-PLV: 56.7 +/- 12.4 mm Hg, Control: 60.6 +/- 5.1 mm Hg; p < 0.01. Dynamic compliance (C20/c) was highest in the Aerosol-PFC group; p < 0.01. Aerosolized perfluorocarbon improved pulmonary gas exchange and lung mechanics as effectively as PLV did in surfactant-depleted piglets, and the improvement was sustained longer.

Partial liquid ventilation in severely surfactant-depleted, spontaneously breathing rabbits supported by proportional assist ventilation

OBJECTIVE

We hypothesized that partial liquid ventilation (PLV) would improve oxygenation in nonparalyzed, surfactant-deficient rabbits breathing spontaneously while supported by proportional assist ventilation (PAV). This ventilation mode compensates for low pulmonary compliance and high resistance and thereby facilitates spontaneous breathing.

DESIGN

Randomized trial.

SETTING

University animal research facility.

SUBJECTS

Twenty-six anesthetized New Zealand white rabbits weighing 2592 +/- 237g (mean +/- sd).

INTERVENTIONS

After pulmonary lavage (target Pao2 <100 mm Hg on mechanical ventilation with 6 cm H2O of positive end-expiratory pressure [PEEP] and an Fio2 of 1.0), rabbits were randomized to PAV (PEEP of 8 cm H2O) with or without PLV. PLV rabbits received 25 mL/kg of perfluorocarbon by intratracheal infusion (1 mL/kg/min). Pao2, Paco2, tidal volume, respiratory rate, minute ventilation, mean airway pressure, arterial blood pressure, heart rate, pulmonary compliance, and airway resistance were measured. Evaporated perfluorocarbon was refilled every 30 mins in PLV animals. After 5 hrs, animals were killed and lungs were removed. Lung injury was evaluated using a histologic score.

MAIN RESULTS

Pao2 and compliance were significantly higher in PLV rabbits compared with controls (p <.05, analysis of variance for repeated measures). All other parameters were similar in both groups.

CONCLUSIONS

PLV improved oxygenation and pulmonary compliance in spontaneously breathing, severely surfactant-depleted rabbits supported by PAV. The severity of lung injury by histology was unaffected.

Advances in management of meconium aspiration syndrome

Meconium Aspiration Syndrome (MAS) is a leading cause of respiratory distress in the newborn. Antenatal diagnosis of meconium stained amniotic fluid and fetal distress is important to reduce morbidity and mortality in the neonates. Amnioinfusion of saline and tracheal suctioning of meconium are preventive interventions. Babies with MAS who continue to have respiratory distress need to be put on conventional ventilators. Increasing hypoxia, hypercarbia and barotrauma warrants changing to high frequency oscillatory ventilation. Pulmonary hypertension is an important complication which should be promptly recognized. Nitric oxide therapy used with high frequency ventilation has improved the outcome of babies with severe MAS and pulmonary hypertension. Some of these babies who continue to worsen clinically need to be put on ECMO circuit. Surfactant infusion in babies with MAS has been shown to improve gas exchange, resolve pulmonary hypertension and decrease oxygenation index. Total and partial liquid ventilation with perflurocarbon improves oxygenation, increases lung expansion and increases pulmonary blood flow in model studies of animals with MAS. Surfactant infusion and liquid ventilation are newer promising modes of therapeutic interventions in babies with severe MAS.

A randomised control study of partial liquid ventilation after airway lavage with exogenous surfactant in a meconium aspiration syndrome animal model

AIMS

To test the hypothesis that lavage with exogenous surfactant before partial liquid ventilation in meconium aspiration syndrome (MAS) would improve debris removal, and therefore the effectiveness of partial liquid ventilation.

METHODS

12 newborn piglets were randomised into 4 groups, partial liquid ventilation or gas ventilation, with and without surfactant lavage. Physiological and blood gas data were compared between groups by analysis of variance.

RESULTS

Arterial oxygen pressure (PaO(2)) was improved in the group treated with surfactant lavage when compared with the group not receiving surfactant. PaO(2) in the group receiving surfactant lavage followed by partial liquid ventilation was further improved when compared with the group treated with surfactant lavage followed by gas ventilation and the group receiving partial liquid ventilation alone.

CONCLUSION

The effectiveness of partial liquid ventilation in MAS might be enhanced by pretreatment with exogenous surfactant bronchial lavage.

Respiratory failure: current status of experimental therapies

A number of advances in the treatment of infants and children with respiratory failure have been investigated in the laboratory with translation to clinical practice. Investigators have recognized that application of high ventilating pressures and failure to apply adequate levels of positive end-expiratory pressure (PEEP) can inflict injury to the already failing lung. Other interventions such as prone positioning and application of new ventilating strategies such as proportional assist ventilation (PAV), inverse ratio ventilation (IRV), high frequency ventilation, liquid ventilation, and intratracheal pulmonary ventilation (ITPV), continue to be developed and explored. Administration of inhaled nitric oxide (iNO) may improve pulmonary physiology and gas exchange in patients with respiratory insufficiency. Finally, the technique of extracorporeal life support (ECLS) is being simplified and refined. This report summarizes the status of these advances and describes the basic science and clinical research that brought them to clinical application.