Criteria for mucus transport in the airways by two-phase gas-liquid flow mechanism

Safety and efficacy of the epithelial sodium channel blocker idrevloride in people with primary ciliary dyskinesia (CLEAN-PCD): a multinational, phase 2, randomised, double-blind, placebo-controlled crossover trial

BACKGROUND

Mucociliary clearance is dysfunctional in people with primary ciliary dyskinesia, resulting in the accumulation of dehydrated mucus in the airways that is difficult to clear. We undertook a study to assess the benefit on lung function of treatment with a nebulised epithelial sodium channel (ENaC) blocker, idrevloride, with or without hypertonic saline, in people with primary ciliary dyskinesia.

METHODS

The CLEAN-PCD trial was a phase 2, randomised, double-blind, placebo-controlled crossover trial conducted at 32 tertiary adult and paediatric care centres and university hospitals in Canada, Denmark, Germany, Italy, the Netherlands, Poland, the UK, and the USA. People with a confirmed diagnosis of primary ciliary dyskinesia, aged 12 years or older, with a percentage of predicted FEV1 (ppFEV1) in the range of 40% to <90%, were randomly assigned in a 2:2:1:1 ratio (block size=6), stratified by ppFEV1 at screening, to one of four sequences: (1) idrevloride in hypertonic saline in treatment period 1 then hypertonic saline in treatment period 2; (2) hypertonic saline in treatment period 1 then idrevloride in hypertonic saline in treatment period 2; (3) idrevloride in treatment period 1 then placebo in treatment period 2; and (4) placebo in treatment period 1 then idrevloride in treatment period 2. The idrevloride dose was 85 μg and hypertonic saline was 4·2% NaCl. 3 mL of each study treatment was nebulised twice daily for 28 days in treatment periods 1 and 2; the two 28-day treatment periods were separated by a 28-day washout period. The primary endpoint was absolute change from baseline in ppFEV1 after 28 days. Safety assessments and reports of adverse events were made at clinic visits during each treatment period and by a follow-up telephone call 28 days after the last dose of study drug. Additionally, adverse events could be reported at a follow-up telephone call 3 days after the start of dosing and as they arose. Participants who received at least one dose of study drug were included in the safety analyses (safety set), and those who also had spirometry data were included in the efficacy analyses (full analysis set). The completed study is registered (EudraCT 2015-004917-26; ClinicalTrials.govNCT02871778).

FINDINGS

Between Sep 14, 2016, and May 31, 2018, 216 patients were screened and 123 were randomly assigned to one of four crossover sequences. Across the two treatment periods, treatment with idrevloride in hypertonic saline was initiated in 80 patients and completed in 78 patients (all 78 had data available and were included in the analysis); hypertonic saline initiated in 81 patients and completed in 76 patients (75 had data available and were included in the analysis); idrevloride initiated in 37 patients and completed in 35 patients (34 had data available and were included in the analysis); and placebo initiated in 36 patients and completed in 34 patients (all 34 had data available and were included in the analysis). Greater absolute increases in ppFEV1 from baseline to 28 days of treatment were seen with idrevloride in hypertonic saline (least-squares mean absolute change from baseline 1·0 percentage points, 95% CI -0·4 to 2·4) than with hypertonic saline alone (least-squares mean absolute change from baseline of -0·5 percentage points, -2·0 to 0·9; difference 1·5 percentage points, 95% CI <0·1 to 3·0; p=0·044). There was no significant difference in ppFEV1 for the parallel comparison of idrevloride in hypertonic saline compared with placebo or the crossover comparison of idrevloride with placebo. Adverse events were similar across treatments (57 to 65% of patients). Cough occurred in a greater proportion of participants during treatments that contained idrevloride or hypertonic saline compared with placebo, and oropharyngeal pain occurred in a greater proportion of participants during idrevloride treatments than during treatment with hypertonic saline alone or placebo, whereas chest discomfort was more common during treatments that included hypertonic saline.

INTERPRETATION

In this phase 2 crossover study, idrevloride in hypertonic saline was safe and associated with improved lung function over a 28-day period in people with primary ciliary dyskinesia compared with hypertonic saline alone. Larger, longer clinical studies are warranted to explore the potential benefits of idrevloride in combination with hypertonic saline in people with primary ciliary dyskinesia.

FUNDING

Parion Sciences, under agreement with Vertex Pharmaceuticals.

Nanoparticle Diffusion in Respiratory Mucus Influenced by Mucociliary Clearance: A Review of Mathematical Modeling

Background: Inhalation and deposition of particles in human airways have attracted considerable attention due to importance of particulate pollutants, transmission of infectious diseases, and therapeutic delivery of drugs at targeted areas. We summarize current state-of-the art research in particle deposition on airway surface liquid (ASL) influenced by mucociliary clearance (MCC) by identifying areas that need further investigation. Methodology: We aim to review focus on governing and constitutive equations describing MCC geometry followed by description of mathematical modeling of ciliary forces, mucus rheology properties, and numerical approaches to solve modified time-dependent Navier-Stokes equations. We also review mathematical modeling of particle deposition in ASL influenced by MCC, particle transport in ASL in terms of Eulerian and Lagrangian approaches, and discuss the corresponding mass transport issues in this layer. Whenever required, numerical predictions are contrasted with the pertinent experimental data. Results: Results indicate that mean mucus and periciliary liquid velocities are strongly influenced by mucus rheological characteristics as well as ciliary abnormalities. However, most of the currently available literature on mucus fiber spacing, ciliary beat frequency, and particle surface chemistry is based on particle deposition on ASL by considering a fixed value of ASL velocity. The effects of real ASL flow regimes on particle deposition in this layer are limited. In addition, no other study is available on modeling nonhomogeneous and viscoelastic characteristics of mucus layer on ASL drug delivery. Conclusion: Simplification of assumptions on governing equations of drug delivery in ASL influenced by MCC leads to imposing some limitations on numerical results.

Development of a novel experimental technique for the measurement of residual wall layer thickness in water-oil displacement flows

The effective removal and displacement of fluids is important in many industrial and environmental applications, such as for operation and cleaning of process equipment, fluid injection in porous media for oil recovery or aquifer remediation, or for achieving subsurface zonal isolation in new or abandoned wells. The accurate measurement of the residual fluid wall film left behind after displacement by a cleaning fluid is a long-standing challenge, particularly so for very thin fluid films where the thickness can be of the order of micrometer. We focus on the characterization of oil films left on the wall of a horizontal pipe after the pipe has been displaced by water, and develop a novel, non-intrusive analytical technique that allows the use of relevant pipe materials. The oil that originally occupies the pipe is stained by a hydrophobic dye Nile red, and an intermediate organic solvent is used to collect the residual oil volume that remains after displacing the pipe with a known volume of water. Finally, ultraviolet-visible spectroscopy is used to measure the Nile red concentration in the collected fluid, which is proportional to the residual volume of oil in the pipe. We demonstrate the methodology by conducting experiments where the displacing fluid is injected at two different imposed velocities, and where the injected fluid volume is varied. As expected, we find a gradual thinning of the oil film with increasing injected fluid volume. We compare the measured film thicknesses to a displacement model based on the steady velocity profile in a pipe, and find that experiments consistently produce smaller film thicknesses. This developed technique allows quantification of displacement and cleaning mechanisms involved in immiscible displacements at laminar, transitional and turbulent regimes, for different non-Newtonian fluid pairs, and for different realistic pipe materials and surface roughnesses.

The effect of posture on airflow distribution, airway geometry and air velocity in healthy subjects

BACKGROUND

Gravity, and thus body position, can affect the regional distribution of lung ventilation and blood flow. Therefore, body positioning is a potential tool to improve regional ventilation, thereby possibly enhancing the effect of respiratory physiotherapy interventions. In this proof-of-concept study, functional respiratory imaging (FRI) was used to objectively assess effects of body position on regional airflow distribution in the lungs.

METHODS

Five healthy volunteers were recruited. The participants were asked during FRI first to lie in supine position, afterwards in standardized right lateral position.

RESULTS

In right lateral position there was significantly more regional ventilation also described as Imaging Airflow Distribution in the right lung than in the left lung (P < 0.001). Air velocity was significantly higher in the left lung (P < 0.05). In right lateral position there was significantly more airflow distribution in the right lung than in the left lung (P < 0.001). Significant changes were observed in airway geometry resulting in a decrease in imaged airway volume (P = 0.024) and a higher imaged airway resistance (P = 0.029) in the dependent lung. In general, the effect of right lateral position caused a significant increase in regional ventilation (P < 0.001) in the dependent lung when compared with the supine position.

CONCLUSIONS

Changing body position leads to significant changes in regional lung ventilation, objectively assessed by FRI The volume based on the imaging parameters in the dependent lung is smaller in the lateral position than in the supine position. In right lateral decubitus position, airflow distribution is greater in dependent lung compared to the nondependent lung.

TRIAL REGISTRATION

The trial has been submitted to www.

CLINICALTRIALS

gov with identification number NCT01893697 on 07/02/2013.

Physiology and pathophysiology of human airway mucus

The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms, and mucus transport rates are heavily dependent on mucus concentration. Importantly, mucus transport rates are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers. The fluid available to hydrate mucus is generated by transepithelial fluid transport. Feedback interactions between mucus concentrations and cilia beating, via purinergic signaling, coordinate Na+ absorptive vs Cl- secretory rates to maintain mucus hydration in health. In disease, mucus becomes hyperconcentrated (dehydrated). Multiple mechanisms derange the ion transport pathways that normally hydrate mucus in muco-obstructive lung diseases, e.g., cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis (NCFB), and primary ciliary dyskinesia (PCD). A key step in muco-obstructive disease pathogenesis is the osmotic compression of the mucus layer onto the airway surface with the formation of adherent mucus plaques and plugs, particularly in distal airways. Mucus plaques create locally hypoxic conditions and produce airflow obstruction, inflammation, infection, and, ultimately, airway wall damage. Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are reviewed.

An Update on Cardiorespiratory Physiotherapy during Mechanical Ventilation

Physiotherapists are integral members of the multidisciplinary team managing critically ill adult patients. However, the scope and role of physiotherapists vary widely internationally, with physiotherapists in some countries moving away from providing early and proactive respiratory care in the intensive care unit (ICU) and focusing more on early mobilization and rehabilitation. This article provides an update of cardiorespiratory physiotherapy for patients receiving mechanical ventilation in ICU. Common and some more novel assessment tools and treatment options are described, along with the mechanisms of action of the treatment options and the evidence and physiology underpinning them. The aim is not only to summarize the current state of cardiorespiratory physiotherapy but also to provide information that will also hopefully help support clinicians to deliver personalized and optimal patient care, based on the patient's unique needs and guided by accurate interpretation of assessment findings and the current evidence. Cardiorespiratory physiotherapy plays an essential role in optimizing secretion clearance, gas exchange, lung recruitment, and aiding with weaning from mechanical ventilation in ICU. The physiotherapists' skill set and scope is likely to be further optimized and utilized in the future as the evidence base continues to grow and they get more and more integrated into the ICU multidisciplinary team, leading to improved short- and long-term patient outcomes.

Management of an infant with epidermolysis bullosa on invasive mechanical ventilation

Objective:

To describe, for the first time in the pediatric population, the use of an effective technique to mobilize secretion in a patient whose disease imposes many care limitations.

Case description:

2-year-old infant with Epidermolysis Bullosa, dependent on mechanical ventilation after cardiorespiratory arrest. Infant evolved with atelectasis in the right upper lobe with restriction to all manual secretion mobilization techniques due to the risk of worsening skin lesions. We opted for tracheal aspiration in a closed system combined with expiratory pause, a technique only described in adult patients so far.

Comments:

This case report is the first to use this technique in a pediatric patient. The use of expiratory pause combined with tracheal aspiration not only optimized the mobilization of secretion, but it was also a safe tool for reversing atelectasis. Our case report brings an important result because it increases the possibilities of managing pediatric patients admitted to intensive care units, especially in situations of absolute contraindication for chest maneuvers.

Physical Therapy and Rehabilitation in Chronic Obstructive Pulmonary Disease Patients Admitted to the Intensive Care Unit

Chronic obstructive pulmonary disease (COPD) is a progressive lung condition that affects a person's ability to exercise and undertake normal physical function due to breathlessness, poor physical fitness, and muscle fatigue. Patients with COPD often experience exacerbations due to pulmonary infections, which result in worsening of their symptoms, more loss of function, and often require hospital treatment or in severe cases admission to intensive care units. Recovery from such exacerbations is often slow, and some patients never fully return to their previous level of activity. This can lead to permanent disability and premature death.Physical therapists play a key role in the respiratory management and rehabilitation of patients admitted to intensive care following acute exacerbation of COPD. This article discusses the key considerations for respiratory management of patients requiring invasive mechanical ventilation, providing an evidence-based summary of commonly used interventions. It will also explore the evidence to support the introduction of early and structured programs of rehabilitation to support recovery in both the short and the long term, as well as active mobilization, which includes strategies to minimize or prevent physical loss through early retraining of both peripheral and respiratory muscles.

A pilot study on the non-invasive management of tracheobronchial secretions in tracheostomised patients

INTRODUCTION/OBJECTIVES

The aim of our study was to assess the safety, efficacy and feasibility of an Expiratory Flow Accelerator (EFA) device, Free Aspire, in reducing the need for daily suctions in tracheostomised (TCS) patients.

METHODS

Twenty-five patients (13 males, 12 females, aged 69.88 ± 9.06 years) were investigated. The number of superficial/deep suctions, shallows, arterial blood gas (ABG) analysis, perception of mucus encumbrance (Visual Numeric Scale, VNS) and adverse event were recorded for five days. On the first two days (T1-T2), suctioning was performed as usual, on the following three days (T3, T4, T5), patients were treated also with Free Aspire (20 min, 3 times a day).

RESULTS/CONCLUSION

The use of the non-invasive device was associated with a decrease of total number of aspirations from T2 to T5 (8.48 ± 2.62 vs 4.48 ± 3.08, P = 0.0003). Total number of daily aspirations decreased over the five days (8.68 ± 3.64 vs 4.48 ± 3.08, P = 0.0009). Deep aspirations decreased from T1 to T5 (6.16 ± 3.53 vs 1.80 ± 1.50, P = 0.0001). ABG data confirmed that no significant side effects occurred. VNS score decreased from 7.03 ± 1.42 at T1 to 4.05 ± 1.80 at T5 (P < 0.0001). These data suggest that EFA may be useful for managing secretions in TCS patients, as it can reduce the number of daily suctions, particularly the deep ones, and may improve the perception of mucus encumbrance, without side effects. More studies are needed to confirm these data and to understand in which categories of TCS patients this device can be introduced.

Airway Clearance with Expiratory Flow Accelerator Technology: Effectiveness of the "Free Aspire" Device in Patients with Severe COPD

OBJECTIVES

Chronic obstructive pulmonary disease (COPD) is associated with a higher risk of pulmonary infections. This risk not only negatively affects patients' quality of life but also increases social and health costs. Hence, there is a need for an effective rehabilitative treatment including airway clearance. The aim of this pilot study was to evaluate the efficacy of a new tool for bronchial clearance based on expiratory flow accelerator (EFA) technology compared with positive expiratory pressure (PEP) treatment.

MATERIALS AND METHODS

Twenty stable patients with COPD, Global Initiative for Chronic Obstructive Lung Disease 3-4 stage, were enrolled and allocated to treatment with EFA or Bubble-PEP (BP) for 20 days during a pulmonary rehabilitation program. At baseline and the end of treatment, the following parameters were measured: arterial blood gases (ABG); respiratory function, including peak cough expiratory flow (PCEF), maximal inspiratory pressure (MIP), and maximal expiratory pressure exercise capacity using the 6-minute walk test (6MWT), dyspnea using the Medical Research Council scale, and quality of life using the St. George's Respiratory Questionnaire.

RESULTS

Expiratory flow accelerator showed a significant pre- and post-improvement in ABG and a significantly greater improvement than BP in PCEF, MIP, and 6MWT post-treatment.

CONCLUSION

Expiratory flow accelerator is a valid device compared with BP as an adjunctive therapy for the treatment of patients with severe COPD.

Effects of ventilation mode and manual chest compression on flow bias during the positive end- and zero end-expiratory pressure manoeuvre in mechanically ventilated patients: a randomised crossover trial

OBJECTIVES

To investigate the effects of ventilation mode and manual chest compression (MCC) application on the flow bias generated during positive end-expiratory pressure-zero end-expiratory pressure (PEEP-ZEEP) in mechanically ventilated patients. PEEP-ZEEP is an airway clearance manoeuvre with the potential to exceed the flow bias required to remove secretions. However, the ventilation mode applied during the manoeuvre has not been standardised.

DESIGN

Randomised crossover trial.

PARTICIPANTS

Nineteen mechanically ventilated patients.

INTERVENTIONS

Patients were randomised to receive PEEP-ZEEP in volume-controlled and pressure-controlled modes, and with or without MCC.

MAIN OUTCOME MEASURES

The difference in flow bias - assessed by the peak expiratory flow (PEF) and peak inspiratory flow (PIF) ratio and difference - between PEEP-ZEEP applied in both ventilation modes, and with and without MCC.

RESULTS

The expiratory flow bias was significantly higher in the volume-controlled mode than the pressure-controlled mode. This result was caused by a lower PIF in the volume-controlled mode. PEEP-ZEEP applied in the pressure-controlled mode did not achieve the PEF-PIF difference threshold to clear mucus. Moreover, in the majority of cycles of PEEP-ZEEP applied in the pressure-controlled mode, an inspiratory flow bias was generated, which might embed mucus. PEF was 8l/minute higher with MCC compared with without MCC, which increased the PEF-PIF difference by the same amount. No haemodynamic or respiratory adverse effects were found.

CONCLUSIONS

If applied in the volume-controlled mode, PEEP-ZEEP can achieve the flow bias needed to expel pulmonary secretions. However, this is not the case in the pressure-controlled mode. MCC can augment the flow bias generated by PEEP-ZEEP, but its application may be dispensable.

CLINICAL TRIAL REGISTRATION

http://www.ensaiosclinicos.gov.br/rg/RBR-223xv8/.

Comparison of an expiratory flow accelerator device versus positive expiratory pressure for tracheobronchial airway clearance after lung cancer lobectomy: a preliminary study

OBJECTIVE

A new type of device has recently been introduced in chest physiotherapy as an aid to tracheo-bronchial airway clearance: expiratory flow accelerator (EFA). It promotes mucus clearance without generating any pressure gradient, allowing patients to breathe at tidal volume against no resistance.

DESIGN

Pilot randomized controlled study.

SETTING

Tertiary hospital.

PARTICIPANTS

Fifty adult patients who underwent lung cancer lobectomy were randomized to undergo chest physiotherapy with EFA (n=26) or PEP (n=24).

INTERVENTIONS

EFA; PEP bottle.

MAIN OUTCOMES

Incidence of postoperative pulmonary complications (PPC) and length of stay.

SECONDARY OUTCOMES

trends in inspiratory capacity, respiratory rate, oxygen saturation, and dyspnoea. Patients rated user-friendliness of the two devices on a 5-point Likert scale.

RESULTS

A slightly different incidence of PPCs was observed between the EFA and PEP group. Nevertheless, the length of stay was similar in the two groups. No substantial differences were seen in trends of inspiratory capacity, respiratory rate, oxygen saturation, dyspnoea between the two groups. Patient-reported user-friendliness of the two devices did not differ significantly, although the use of the EFA device appeared less strenuous.

CONCLUSIONS

Results of this pilot study point to the use of EFA as an alternative treatment option rather than as a replacement for the PEP bottle in chest physiotherapy following lung cancer lobectomy. EFA may be preferable for weaker patients and/or with airway leakages in whom PEP has limited indications. Further investigation in a larger sample is required to statistically confirm the findings. Clinical Trial Registration Number ChiCTR-ONC-17013255.

Effects of Combined Tracheal Suctioning and Expiratory Pause: A Crossover Randomized Clinical Trial

Aims

Our aim is to compare volume of suctioned secretion, respiratory mechanics, and hemodynamic parameters in intubated patients undergoing closed-system endotracheal suctioning alone (control group) versus closed-system tracheal suctioning with an expiratory pause (intervention group).

Settings and design

Randomized crossover clinical trial.

Materials and methods

Patients who had been on mechanical ventilation for more than 24 hours were randomly assigned to receive closed-system suctioning alone or closed-system suctioning with an expiratory pause on the ventilator. The following variables were evaluated: heart rate, respiratory rate, mean arterial pressure, peripheral arterial oxygen saturation, peak inspiratory pressure, mechanical ventilator circuit pressure during aspiration, exhaled tidal volume, dynamic compliance, resistance, and weight of suctioned secretion.

Statistical analysis

Compared using the paired t-test and general linear model analysis of variance for normally distributed variables (as confirmed by the Kolmogorov-Smirnov test). The Wilcoxon test was used for variables with a nonparametric distribution, while the Chi-square test and Fisher's exact test were used for categorical variables.

Results

The sample comprised 31 patients (mean age, 61.1 ± 18.2 years). The amount of secretion suctioned was significantly higher in the intervention group than in the control group (1.6 g vs 0.45 g; p = 0.0001). There were no significant changes in hemodynamic parameters or respiratory mechanics when comparing pre- and postprocedure time points.

Conclusion

The combination of closed-system endotracheal suctioning and an expiratory pause significantly increased the amount of secretion suctioned compared to conventional suctioning without expiratory pause.

Key messages

Combination of closed-system endotracheal suctioning and an expiratory pause significantly increased the amount of secretion suctioned.

How to cite this article

Martins LFG, Naue WS, Skueresky AS, Bianchi T, Dias AS, Forgiarini Junior LA. Effects of Combined Tracheal Suctioning and Expiratory Pause: A Crossover Randomized Clinical Trial. Indian J Crit Care Med 2019;23(10):454–457.

Effect of inspiratory rise time on sputum movement during ventilator hyperinflation in a test lung model

OBJECTIVES

Physiotherapists may use ventilator hyperinflation to enhance secretion clearance for intubated patients. This study investigated the effects of altering percentage inspiratory rise time (IRT) on sputum movement, ratio of peak inspiratory to expiratory flow rate (PIF:PEF ratio) and net peak expiratory flow (PEF) during ventilator hyperinflation in a test lung model.

DESIGN

Laboratory-based bench study.

INTERVENTIONS

Simulated sputum (two viscosities) was inserted into clean, clear tubing and connected between a ventilator and a resuscitation bag. Thirty-six ventilator hyperinflation breaths were applied for each 5% incremental increase in IRT between 0% and 20%.

MAIN OUTCOME MEASURES

The primary outcome was sputum displacement (cm). Secondary outcomes included PIF:PEF ratio and net PEF.

RESULTS

Significant cephalad sputum movement of 2.42cm (1.59 to 3.94) occurred with IRT between 5% and 20%, compared with caudad movement of 0.53 cm (0.31 to 1.53) at 0% IRT (median sputum movement difference 3.7cm, 95% confidence interval 2.2 to 4.8, P<0.001). Incremental increases in IRT percentage produced linear enhancements in PIF:PEF ratio and net PEF for both sputum concentrations (P<0.001). However, once the critical threshold for PIF:PEF ratio of 0.9 was achieved, the distance of sputum movement remained consistent for all IRT values exceeding 5%.

CONCLUSIONS

Significant increases in sputum movement occurred when IRT percentage was lengthened to achieve the optimal PIF:PEF ratio, irrespective of sputum viscosity. This provides a theoretical rationale for therapists to consider this technique when treating mechanically ventilated patients. As no additional sputum movement was seen beyond the critical PIF:PEF ratio threshold, a low IRT percentage may potentially be used to achieve effective sputum movement.

Airway clearance techniques for bronchiectasis

BACKGROUND

People with non-cystic fibrosis bronchiectasis commonly experience chronic cough and sputum production, features that may be associated with progressive decline in clinical and functional status. Airway clearance techniques (ACTs) are often prescribed to facilitate expectoration of sputum from the lungs, but the efficacy of these techniques in a stable clinical state or during an acute exacerbation of bronchiectasis is unclear.

OBJECTIVES

Primary: to determine effects of ACTs on rates of acute exacerbation, incidence of hospitalisation and health-related quality of life (HRQoL) in individuals with acute and stable bronchiectasis. Secondary: to determine whether:• ACTs are safe for individuals with acute and stable bronchiectasis; and• ACTs have beneficial effects on physiology and symptoms in individuals with acute and stable bronchiectasis.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of trials from inception to November 2015 and PEDro in March 2015, and we handsearched relevant journals.

SELECTION CRITERIA

Randomised controlled parallel and cross-over trials that compared an ACT versus no treatment, sham ACT or directed coughing in participants with bronchiectasis.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by The Cochrane Collaboration.

MAIN RESULTS

Seven studies involving 105 participants met the inclusion criteria of this review, six of which were cross-over in design. Six studies included adults with stable bronchiectasis; the other study examined clinically stable children with bronchiectasis. Three studies provided single treatment sessions, two lasted 15 to 21 days and two were longer-term studies. Interventions varied; some control groups received a sham intervention and others were inactive. The methodological quality of these studies was variable, with most studies failing to use concealed allocation for group assignment and with absence of blinding of participants and personnel for outcome measure assessment. Heterogeneity between studies precluded inclusion of these data in the meta-analysis; the review is therefore narrative.One study including 20 adults that compared an airway oscillatory device versus no treatment found no significant difference in the number of exacerbations at 12 weeks (low-quality evidence). Data were not available for assessment of the impact of ACTs on time to exacerbation, duration or incidence of hospitalisation or total number of hospitalised days. The same study reported clinically significant improvements in HRQoL on both disease-specific and cough-related measures. The median difference in the change in total St George's Respiratory Questionnaire (SGRQ) score over three months in this study was 7.5 units (P value = 0.005 (Wilcoxon)). Treatment consisting of high-frequency chest wall oscillation (HFCWO) or a mix of ACTs prescribed for 15 days significantly improved HRQoL when compared with no treatment (low-quality evidence). Two studies reported mean increases in sputum expectoration with airway oscillatory devices in the short term of 8.4 mL (95% confidence interval (CI) 3.4 to 13.4 mL) and in the long term of 3 mL (P value = 0.02). HFCWO improved forced expiratory volume in one second (FEV1) by 156 mL and forced vital capacity (FVC) by 229.1 mL when applied for 15 days, but other types of ACTs showed no effect on dynamic lung volumes. Two studies reported a reduction in pulmonary hyperinflation among adults with non-positive expiratory pressure (PEP) ACTs (difference in functional residual capacity (FRC) of 19%, P value < 0.05; difference in total lung capacity (TLC) of 703 mL, P value = 0.02) and with airway oscillatory devices (difference in FRC of 30%, P value < 0.05) compared with no ACTs. Low-quality evidence suggests that ACTs (HFCWO, airway oscillatory devices or a mix of ACTs) reduce symptoms of breathlessness and cough and improve ease of sputum expectoration compared with no treatment (P value < 0.05). ACTs had no effect on gas exchange, and no studies reported effects of antibiotic usage. Among studies exploring airway oscillating devices, investigators reported no adverse events.

AUTHORS' CONCLUSIONS

ACTs appear to be safe for individuals (adults and children) with stable bronchiectasis and may account for improvements in sputum expectoration, selected measures of lung function, symptoms and HRQoL. The role of these techniques in acute exacerbation of bronchiectasis is unknown. In view of the chronic nature of bronchiectasis, additional data are needed to establish the short-term and long-term clinical value of ACTs for patient-important outcomes and for long-term clinical parameters that impact disease progression in individuals with stable bronchiectasis, allowing further guidance on prescription of specific ACTs for people with bronchiectasis.

Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment

The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale.

Airway clearance techniques for bronchiectasis

BACKGROUND

People with non-cystic fibrosis bronchiectasis commonly experience chronic cough and sputum production and these features may be associated with progressive decline in clinical status. Airway clearance techniques (ACTs) are often prescribed to facilitate expectoration of sputum from the lungs, but the efficacy of these techniques in a stable clinical state or during an acute exacerbation of bronchiectasis is unclear.

OBJECTIVES

Primary: to determine the effects of ACTs on the rate of acute exacerbations, incidence of hospitalisation and health-related quality of life in individuals with acute and stable bronchiectasis.Secondary: to determine whether a) ACTs are safe for individuals with acute and stable bronchiectasis and b) ACTs have beneficial effects on physiology and symptoms in individuals with acute and stable bronchiectasis.

SEARCH METHODS

We searched the Cochrane Airways Group Specialised Register of trials from inception to October 2012, PEDro in October 2012 and handsearched relevant journals.

SELECTION CRITERIA

Randomised controlled parallel and cross-over trials that compared an ACT to no treatment, sham ACT or directed coughing in participants with bronchiectasis.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

Five studies involving 51 participants met the inclusion criteria of the review, all of which were cross-over design. Four studies were on adults with stable bronchiectasis, and the other study was on clinically stable children with bronchiectasis. Three studies were single treatment sessions, two were longer-term studies. The interventions varied and some control groups received a sham intervention while others were inactive. The methodological quality of the studies was variable and the studies were not able to blind participants and personal. Heterogeneity between studies precluded these data from meta-analysis and the review was therefore narrative.One study on 20 adults comparing an airway oscillatory device with no treatment found no significant difference in the number of exacerbations at 12 weeks (low-quality evidence). No data were available to assess the impact of ACTs on the time to exacerbation, duration of, incidence of hospitalisation or total number of hospitalised days. The same study reported clinically significant improvements in health-related quality of life in both disease-specific and cough-related measures. While based on a small number of participants and the data were skewed, the median difference in the change in total St George's Respiratory Questionnaire (SGRQ) score over three months in this study was 8.5 units (P value = 0.005 (Wilcoxon), low-quality evidence). Two studies reported mean increases in volume of sputum expectorated with airway oscillatory devices in the short term of 8.4 mL (95% CI 3.4 to 13.4 mL) and in the long term of 3 mL (P value = 0.02), with no significant effect on lung function. One study reported an immediate reduction in pulmonary hyperinflation in adults with non-positive expiratory pressure (PEP) ACTs (difference in functional residual capacity (FRC) of 19%, P value < 0.05) and with airway oscillatory devices (difference in FRC of 30%, P value < 0.05) compared to no ACTs. A similar decrease in pulmonary hyperinflation (difference in FRC of 6%) was found in children using an airway oscillatory device for 3 months compared to sham therapy. No studies reported on the effects of gas exchange, people's symptoms or antibiotic usage.

AUTHORS' CONCLUSIONS

ACTs appear to be safe for individuals (adults and children) with stable bronchiectasis, where there may be improvements in sputum expectoration, selected measures of lung function and health-related quality of life. The role of these techniques in people with an acute exacerbation of bronchiectasis is unknown. In view of the chronic nature of bronchiectasis, more data are needed to establish the clinical value of ACTs over the short and long term on patient-important outcomes, including symptoms, on physiological outcomes which may clarify the rationale for each technique and on long-term parameters that impact on disease progression in individuals with stable bronchiectasis. This is necessary in order to provide further guidance of specific ACT prescription for people with bronchiectasis. It may also be important to establish the comparative effect of different types of ACTs in people with bronchiectasis.

Mucus clearance from the pulmonary system by mechanical means: a dual-excitation approach

A dual-excitation approach to mechanical clearance of mucus from the pulmonary system is described. The approach employs independently controlled vibratory and constrictive pressure stimulations to the thorax. Patient cooperative efforts are integrated into the therapy regimen as a means of enhancing the efficacy of the treatment. An engineering model that demonstrates the capability to generate vibratory and constrictive pressure variations at specified levels is described.

Effects of manual rib cage compressions on expiratory flow and mucus clearance during mechanical ventilation

OBJECTIVES

We investigated the effects of two different types of manual rib cage compression on expiratory flow and mucus clearance during prolonged mechanical ventilation in pigs.

DESIGN

Prospective randomized animal study.

SETTING

Animal research facility, University of Barcelona, Spain.

SUBJECTS

Nine healthy pigs.

MEASUREMENT AND MAIN RESULTS

Pigs were tracheally intubated, sedated, paralyzed, and mechanically ventilated. The animals were prone on a surgical bed in the anti-Trendelenburg position. The experiments were carried out at approximately 60 and 80 hrs from the beginning of mechanical ventilation. Two types of manual rib cage compressions were tested: Hard and brief rib cage compressions synchronized with early expiratory phase (hard manual rib cage compression) and soft and gradual rib cage compressions applied during the late expiratory phase (soft manual rib cage compression). The interventions were randomly applied for 15min with a 15-min interval between treatments. Respiratory flow and mucus movement were assessed during the interventions. Respiratory mechanics and hemodynamics were assessed prior to and after the interventions. Peak expiratory flow increased to 60.1±7.1L/min in comparison to 51.2±4.6L/min without treatment (p < 0.0015) and 48.7±4.3L/min with soft manual rib cage compression (p = 0.0002). Similarly, mean expiratory flow increased to 28.4±5.2L/min during hard manual rib cage compression vs. 15.9±2.2 and 16.6±2.8L/min without treatment and soft manual rib cage compression, respectively (p = 0.0006). During hard manual rib cage compression, mucus moved toward the glottis (1.01 ± 2.37mm/min); conversely, mucus moved toward the lungs during no treatment and soft manual rib cage compression, -0.28 ± 0.61 and -0.15±0.95mm/min, respectively (p = 0.0283). Soft manual rib cage compression slightly worsened static lung elastance and cardiac output (p = 0.0391).

CONCLUSIONS

Hard manual rib cage compression improved mucus clearance in animals positioned in the anti-Trendelenburg position. The technique appeared to be safe. Conversely, soft manual rib cage compression was not effective and potentially unsafe. These findings corroborate the predominant role of peak expiratory flow on mucus clearance.

Exercise as part of a cystic fibrosis therapeutic routine

The role of exercise in cystic fibrosis (CF) is well established, and over the last three decades it has become an important component in the management of all individuals with CF. The role of exercise as a prognostic indicator or therapeutic tool is an important area of research interest in CF care internationally. This article summarizes the currently available evidence regarding exercise capacity in CF, the potential effects of exercise on health outcomes in CF and the challenges faced when trying to incorporate exercise into a CF therapeutic routine, and highlights some methods to facilitate the incorporation of exercise into CF therapeutic routines.

Conditional deletion of dnaic1 in a murine model of primary ciliary dyskinesia causes chronic rhinosinusitis

Studies of primary ciliary dyskinesia (PCD) have been hampered by the lack of a suitable animal model because disruption of essential ciliary genes in mice results in a high incidence of lethal hydrocephalus. To develop a viable mouse model for long-term studies of PCD, we have generated a transgenic mouse line in which two conserved exons of the mouse intermediate dynein chain gene, Dnaic1, are flanked by loxP sites (Dnaic1(flox/flox)). Dnaic1 is the murine homolog of human DNAI1, which is mutated in approximately 10% of human PCD cases. These mice have been crossed with mice expressing a tamoxifen-inducible Cre recombinase (CreER). Treatment of adult Dnaic1(flox/flox)/CreER(+/-) mice with tamoxifen results in an almost complete deletion of Dnaic1 with no evidence of hydrocephalus. Treated animals have reduced levels of full-length Dnaic1 mRNA, and electron micrographs of cilia demonstrate a loss of outer dynein arm structures. In treated Dnaic1(flox/flox)/CreER(+/-) animals, mucociliary clearance (MCC) was reduced over time. After approximately 3 months, no MCC was observed in the nasopharynx, whereas in the trachea, MCC was observed for up to 6 months, likely reflecting a difference in the turnover of ciliated cells in these tissues. All treated animals developed severe rhinosinusitis, demonstrating the importance of MCC to the health of the upper airways. However, no evidence of lung disease was observed up to 11 months after Dnaic1 deletion, suggesting that other mechanisms are able to compensate for the lack of MCC in the lower airways of mice. This model will be useful for the study of the pathogenesis and treatment of PCD.

Semi-quantitative tracking of intra-airway fluids by computed tomography

BACKGROUND

Airway secretions are a source of complications for patients with acute and chronic lung diseases, yet lack of techniques to quantitatively track secretions hampers research into clinical measures to reduce their pathologic consequences.

METHODS

In a preserved swine lung model, we tracked a contrasted mucus simulant (CMS) using sequential computed tomography (CT). Known drivers of secretion movement - gravity and ventilation - were tested. Ten millilitres of CMS were unilaterally introduced (1 ml min(-1)) into the airways of 12 lung sets. After instillation, six lung sets were maintained prone and six were rotated 180 degrees . Subsequently, all were mechanically ventilated for 10 min. CTs were obtained before infusion, after infusion and after ventilation +/- rotation. For CT analysis, the lungs were partitioned into eight sub-cuboids using anatomic landmarks. The volumes of two CT number ranges representing CMS and poor aeration/collapse were computed in every sub-cuboid for each CT acquisition. Volume differences between study time points were used to quantify changes.

RESULTS

CMS and poor aeration/collapse volume change distributed gravitationally after infusion. After ventilation without rotation, the CMS and poor aeration/collapse volumes remained within the originally injected sub-cuboid, although the poor aeration/collapse volume expanded (27.3 +/- 6.1-->50.5 +/- 7.4 ml, P<0.05). After ventilation + rotation, there was a reduction in the CMS and poor/aeration collapse volumes in the originally injected sub-cuboid (14.4 +/- 1.7-->4.4 +/- 0.6 ml, P<0.05 and 18.3 +/- 3.8-->11.9 +/- 2.7 ml, P<0.05, respectively) accompanied by increases in the gravitationally opposite sub-cuboid (1.7 +/- 0.2-->11.1 +/- 1.1 ml, P<0.05 and 0.8 +/- 0.5-->40.6 +/- 3.5 ml, P<0.05, respectively).

CONCLUSION

Movement of fluids within the bronchial tree can be semi-quantitatively tracked with analysis of sequential CT acquisitions. In this isolated swine lung model, gravity had an important and brisk effect on movement of a viscous fluid, whereas ventilation tended to embed it peripherally.

Role of cilia, mucus, and airway surface liquid in mucociliary dysfunction: lessons from mouse models

Mucociliary clearance is an important primary innate defense mechanism that protects the lungs from deleterious effects of inhaled pollutants, allergens, and pathogens. Mucociliary dysfunction is a common feature of chronic airway diseases in humans. The mucociliary apparatus consists of three functional compartments, that is, the cilia, a protective mucus layer, and an airway surface liquid (ASL) layer, which work in concert to remove inhaled particles from the lung. A synopsis of clinical and pathological observations in patients with cystic fibrosis, primary ciliary dyskinesia, asthma, and chronic bronchitis indicates that abnormalities in each compartment of the mucociliary system can compromise mucus clearance and cause chronic airway disease. However, the mechanisms that lead to deficient mucus clearance are still incompletely understood. Genetically engineered mice with defects in individual elements of the mucociliary apparatus are powerful tools to study the pathogenesis of mucociliary dysfunction in vivo. In this concise review, I assess the pulmonary phenotypes of mouse models with genetically defined abnormalities in ciliary structure/function, mucus production, and ASL regulation, and discuss the results of these animal studies in the context of current pathogenetic hypotheses for mucociliary dysfunction. Recent data driven from these animal studies point to a critical role of ASL dehydration in the pathogenesis of mucociliary dysfunction and chronic airway disease. In mice with airway-specific overexpression of epithelial Na(+) channels (ENaC), which constitute a rate limiting pathway for absorption of salt and water from airway surfaces, ASL depletion caused reduced mucus clearance, and a spontaneous chronic airway disease with mucus obstruction, goblet cell metaplasia, chronic inflammation, reduced bacterial clearance, and high pulmonary mortality. This mouse model of mucociliary dysfunction will allow an in vivo evaluation of novel therapeutic strategies designed to improve mucociliary clearance, and will aid the preclinical development of novel therapies for chronic airway diseases.

Do airway secretions play an underappreciated role in acute respiratory distress syndrome?

PURPOSE OF REVIEW

We review the evidence that airway secretions may have an underappreciated role in acute respiratory distress syndrome, contributing to physiologic disarrangements, ventilator dependence and perhaps to injury generation. As common manipulations of ventilator settings, position and fluid status have the potential to influence these problems, explorations into the secretion dynamics of acute lung injury may be fertile ground for developing therapeutic advances.

RECENT FINDINGS

Principles that govern the interaction of airflow and airway fluids suggest that mobile fluids and secretions are pumped by well-selected ventilatory patterns toward the airway opening. Conversely, other selections may inhibit these fluids from clearance or encourage their translocation between lung regions. Recent laboratory work demonstrates that choices for tidal volume and positive end-expiratory pressure may localize or disperse proteinaceous lung edema or bacteria. Gravitational factors may interact with ventilatory pattern for benefit or harm.

SUMMARY

Capability of ventilation and positioning to mobilize secretions implies the potential for clearance or containment of inflammatory mediators and infection. Ventilatory and positional prescriptions could be designed to meet one of either conflicting targets. Additional experimental and clinical investigations are required before adopting these proposed therapeutic principles into practice.

The Mapleson C circuit clears more secretions than the Laerdal circuit during manual hyperinflation in mechanically-ventilated patients: a randomised cross-over trial

QUESTION

What is the effect of the Mapleson C circuit compared with the Laerdal circuit in removing secretions and improving ventilation and gas exchange during manual hyperinflation?

DESIGN

Prospective, randomised, cross-over trial.

PARTICIPANTS

Twenty patients from a tertiary-level intensive care unit who were being mechanically ventilated.

INTERVENTION

Manual hyperinflation in side-lying with both the Mapleson C or Laerdal circuit on the one day, one circuit in the morning and one in the afternoon, with a washout period of at least three hours between them.

OUTCOME MEASURES

Secretion clearance was measured as sputum weight, ventilation was measured as respiratory compliance and tidal volume, while gas exchange was measured as oxygenation and CO2 removal.

RESULTS

The Mapleson C circuit cleared 0.89 g (95% CI 0.80 to 1.15) more secretions than the Laerdal circuit (p < 0.02). There was no difference between the Mapleson C and the Laerdal circuits on respiratory compliance (p = 0.81), tidal volume (p = 0.45), oxygenation (p = 0.28), or CO2 removal (p = 0.17).

CONCLUSION

Although more secretions were cleared using the Mapleson C compared with the Laerdal circuit in this study, this had no consequence in terms of oxygenation and compliance only trended to improve. As the study was underpowered the clinical significance of these findings is not clear.

Comparison of the effectiveness of manual and ventilator hyperinflation at different levels of positive end-expiratory pressure in artificially ventilated and intubated intensive care patients

BACKGROUND

Manual hyperinflation (MHI) and ventilator hyperinflation (VHI) are two methods of recruitment maneuvers used in ventilated patients to improve lung compliance and secretion mobilization. The use of VHI may minimize the adverse effects of disconnection from the ventilator, but it is uncertain whether high levels of positive end-expiratory pressure (PEEP) would decrease the peak expiratory flow rate (PEFR) and consequently affect secretion clearance.

OBJECTIVES

The aim of this study was to compare the effectiveness of MHI and VHI in terms of clearing pulmonary secretions (sputum wet weight and PEFR), improving static respiratory system compliance and oxygenation (arterial oxygen tension/fraction of inspired oxygen), and altering mean arterial pressure, heart rate, and carbon dioxide output at different levels of PEEP.

METHODS

This was a randomized crossover study involving 14 general intensive care patients who were intubated and mechanically ventilated.

RESULTS

Sputum production was similar in both techniques and levels of PEEP. There were no differences in improvement in oxygenation and static respiratory system compliance between MHI and VHI. However, VHI increased Cst significantly at 30 minutes posttreatment (P = .012), and a significant difference was observed between levels 5 and 7.5 cmH(2)O (P = .02) of PEEP for MHI. MHI generated higher PEFR than VHI (P < .05). No adverse change in heart rate or mean arterial pressure was observed during either technique; however, VCO(2) was significantly different for techniques (P = .045) and over time (P = .05).

CONCLUSION

The VHI technique seems to promote greater improvements in respiratory mechanics with less metabolic disturbance compared with MHI. Other variables such as sputum production, hemodynamics, and oxygenation were affected similarly by both techniques.

The role of airway secretions in COPD--clinical applications

It has been established that mucus hypersecretion and decreased mucus clearance contribute to the morbidity of chronic obstructive pulmonary disease (COPD). Indeed, the classic definition of chronic bronchitis relies on determining the frequency and duration of sputum expectoration. Despite the well recognized importance of this symptom, there are few therapies routinely used to decrease the sputum production or to improve clearance. There are fewer well conducted clinical trials of existing medications and this has led many regulatory agencies, notably the Food and Drug Administration (FDA), to refuse to register these medications or approve their sale. Similarly, airway clearance devices and chest physical therapy have not been well studied in COPD. Carefully conducted studies of interventions to improve airway clearance, similar to those done in cystic fibrosis (CF), may help us to identify effective therapies and possibly novel diagnostic tests for the management of COPD.

The effect of positive end-expiratory pressure level on peak expiratory flow during manual hyperinflation

Including positive end-expiratory pressure (PEEP) in the manual resuscitation bag (MRB) may render manual hyperinflation (MHI) ineffective as a secretion maneuver technique in mechanically ventilated patients. In this study we aimed to determine the effect of increased PEEP or decreased compliance on peak expiratory flow rate (PEF) during MHI. A blinded, randomized study was performed on a lung simulator by 10 physiotherapists experienced in MHI and intensive care practice. PEEP levels of 0-15 cm H(2)O, compliance levels of 0.05 and 0.02 L/cm H(2)O, and MRB type were randomized. The Mapleson-C MRB generated significantly higher PEF (P < 0.01, d = 2.72) when compared with the Laerdal MRB for all levels of PEEP. In normal compliance (0.05 L/cm H(2)O) there was a significant decrease in PEF (P < 0.01, d = 1.45) for a PEEP more than 10 cm H(2)O in the Mapleson-C circuit. The Laerdal MRB at PEEP levels of more than 10 cm H(2)O did not generate a PEF that is theoretically capable of producing two-phase gas-liquid flow and, consequently, mobilizing pulmonary secretions. If MHI is indicated as a result of mucous plugging, the Mapleson-C MRB may be the most effective method of secretion mobilization.

Increased airway epithelial Na+ absorption produces cystic fibrosis-like lung disease in mice

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene result in defective epithelial cAMP-dependent Cl(-) secretion and increased airway Na(+) absorption. The mechanistic links between these altered ion transport processes and the pathogenesis of cystic fibrosis lung disease, however, are unclear. To test the hypothesis that accelerated Na(+) transport alone can produce cystic fibrosis-like lung disease, we generated mice with airway-specific overexpression of epithelial Na(+) channels (ENaC). Here we show that increased airway Na(+) absorption in vivo caused airway surface liquid (ASL) volume depletion, increased mucus concentration, delayed mucus transport and mucus adhesion to airway surfaces. Defective mucus transport caused a severe spontaneous lung disease sharing features with cystic fibrosis, including mucus obstruction, goblet cell metaplasia, neutrophilic inflammation and poor bacterial clearance. We conclude that increasing airway Na(+) absorption initiates cystic fibrosis-like lung disease and produces a model for the study of the pathogenesis and therapy of this disease.

Secretion movement during manual lung inflation and mechanical ventilation

This project aimed to investigate the direction of artificial sputum movement during mechanical ventilation (MV) and bagging (MH) using a tube model. Three solutions of artificial sputum (ultrasonic gel, viscosity 100, 200 and 300 poise (P)) were prepared. About 1 ml of gel was placed in a glass tube connected to a test lung at one end and, via a pneumotachograph, to either a mechanical ventilator or a self-inflating bag, at the other. The position of the gel in the tube was recorded before and after 20 artificial breaths. Simultaneous breath-to-breath respiratory mechanics were measured. The procedure was repeated three times for each gel viscosity, with a fresh experimental set up for each measurement. Results showed that the distance travelled from the lung was significantly greater with MH compared with MV (P < 0.001). The lower the gel viscosity, the further the gel moved from the lung with both ventilatory modes (P < 0.001). MH was superior to MV for secretion mobilisation in a tube model.

Noninvasive motion ventilation (NIMV): a novel approach to ventilatory support

A motion platform was developed that oscillates an animal in a foot-to-head direction (z-plane). The platform varies the frequency and intensity of acceleration, imparting periodic sinusoidal inertial forces (pG(z)) to the body. The aim of the study was to characterize ventilation produced by the noninvasive motion ventilator (NIMV) in animals with healthy and diseased lungs. Incremental increases in pG(z) (acceleration) with the frequency held constant (f = 4 Hz) produced almost linear increases in minute ventilation (VE). Frequencies of 2-4 Hz produced the greatest VE and tidal volume (VT) for any given acceleration between +/-0.2 and +/-0.8 G. Increasing the force due to acceleration produced proportional increases in both transpulmonary and transdiaphragmatic pressures. Increasing transpulmonary pressure by increasing pG(z) produced linear increases in VT, similar to spontaneous breathing. NIMV reversed deliberately induced hypoventilation and normalized the changes in arterial blood gases induced by meconium aspiration. In conclusion, a novel motion platform is described that imparts periodic sinusoidal acceleration forces at moderate frequencies (4 Hz) to the whole body in the z-plane. These forces, when properly adjusted, are capable of highly effective ventilation of normal and diseased lungs. Such noninvasive ventilation is accomplished at airway pressures equivalent to atmospheric or continuous positive airway pressure, with acceleration forces less than +/-1 G(z).

An investigation of the early effects of manual lung hyperinflation in critically ill patients

This prospective within-group multicentre study was designed to assess the safety and short-term effectiveness of manual lung hyperinflation in mechanically ventilated patients. Eighteen patients from the intensive care units of two tertiary institutions were included and acted as their own control. Manual lung hyperinflation treatment involved patient positioning (side-lying), suctioning and manual lung hyperinflation. Side-lying treatment involved patient positioning and suctioning alone. Patients received both treatments on the day of data collection. Results demonstrated significant improvement for static respiratory system compliance (P = 0.001) with manual lung hyperinflation treatment compared to side-lying treatment. Manual lung hyperinflation treatment also cleared a significantly greater wet weight of sputum (P = 0.039). There were no differences between manual lung hyperinflation and side-lying treatment for gas exchange (PaO2/FIO2 and PaCO2), mean arterial pressure or heart rate. In conclusion, total static respiratory system compliance and sputum clearance were improved by the addition of manual hyperinflation to a physiotherapy treatment of positioning and suctioning in mechanically ventilated patients without compromise to cardiovascular stability or gas exchange.

Effect of high-frequency oral airway and chest wall oscillation and conventional chest physical therapy on expectoration in patients with stable cystic fibrosis

STUDY OBJECTIVE

To compare the effect of high-frequency oral airway oscillation, high-frequency chest wall oscillation, and conventional chest physical therapy (CPT) on weight of expectorated sputum, pulmonary function, and oxygen saturation in outpatients with stable cystic fibrosis (CF).

DESIGN

Prospective randomized trial.

SETTING

Pediatric pulmonary division of a tertiary care center.

PATIENTS

Fourteen outpatients with stable CF recruited from the CF center.

INTERVENTIONS

Two modes of oral airway oscillation (1: frequency 8 Hz; inspiratory to expiratory [I:E] ratio 9:1; 2: frequency 14 Hz; I:E ratio 8:1), two modes of chest wall oscillation (1: frequency 3 Hz; I:E ratio 4:1; 2: frequency 16 Hz; I:E ratio 1:1, alternating with frequency 1.5 Hz, I:E ratio 6:1), and CPT (clapping, vibration, postural drainage, and encouraged coughing) were applied during the first 20 min of 4 consecutive hours.

MEASUREMENTS AND RESULTS

Sputum was collected on an hourly basis for a total of 6 consecutive hours. During the first and the last hour, patients collected sputum without having any treatment and underwent pulmonary function tests (PFTs). Oxygen saturation was measured at 30-min intervals during hours 1 to 6. For the first 20 min of the second to the fifth hour, patients received one of the treatments. To assess the effect of the intervention, the weight of expectorated sputum during hours 2 to 6 was averaged and expressed as percentage of the weight expectorated during the first hour (baseline). For the five treatment modalities, mean sputum dry and wet weights ranged between 122% and 185% of baseline. There was no statistically significant difference among the treatment modalities. As measured by sputum wet weight, all oscillatory devices tended to be less effective than CPT (p=0.15). As measured by dry weight, oral airway oscillation at 8 Hz with an I:E ratio of 9:1 and CPT tended to be more effective than the other treatment modalities (p=0.57). None of the treatment modalities had an effect on PFTs and oxygen saturation and all were well tolerated.

CONCLUSION

In outpatients with stable CF, high-frequency oscillation applied via the airway opening or via the chest wall and CPT have comparable augmenting effects on expectorated sputum weight without changing PFTs or oxygen saturation. In contrast to CPT, high-frequency oral airway and chest wall oscillations are self-administered, thereby containing health-care expenses.

Promoting meconium clearance from the lungs of the neonatal piglet with asymmetric high frequency oscillation

To investigate the role of high frequency oscillation (HFO) in promoting meconium clearance from the airway, we used a commercially available ventilator configured with maximal expiratory flow exceeding inspiratory flow (asymmetric HFO or AHFO). We hypothesized that AHFO would move meconium in an expiratory direction (toward the ventilator). We first tested our hypothesis in vitro and, later, in vivo using the neonatal piglet. In vitro experiments using a Plexiglas airway confirmed meconium movement in an expiratory direction when bias ratio was > or = 2. For in vivo experiments, each piglet received a 3 mL/kg intratracheal bolus of a 44 g/100 mL meconium mixture followed by 45 min of mechanical ventilation. Then, in part 1, the piglet was placed in a 15 degree head down tilt position and randomized to either AHFO [ratio of inspiratory time/expiratory time (I:E) of 70:30] or HFO (I:E ratio of 30:70). After 30 min of either AHFO or HFO, the piglet was crossed over to the alternate strategy for an additional 30 min. For part 2, we maintained the piglet on either AHFO or HFO continuously for 4 h. Results demonstrate that, although there was a tendency for larger volumes of meconium to be aspirated from the airway during AHFO in part 1 experiments, there was no difference found in part 2. We also found no significant differences in blood gases or hemodynamic measurements between AHFO and HFO during the prolonged observation period in part 2 of our study. We conclude that AHFO is of no benefit in the treatment of meconium aspiration syndrome.

Relationship between bronchial reversibility and tracheobronchial clearance in patients with chronic bronchitis

BACKGROUND

Patients with chronic bronchitis show a large intersubject variation in sputum rheology, tracheobronchial clearance, and reversibility of airflow obstruction to beta 2 agonists. The bronchial mediators which are known to cause bronchoconstriction, mucosal oedema, mucus hypersecretion, and cough can also affect mucociliary transport. The aim of this study was to ascertain whether changes in tracheobronchial clearance and sputum rheological properties in patients with chronic bronchitis were associated with a specific degree of airflow reversibility assessed as the bronchial response to an inhaled beta 2 agonist (fenoterol 400 micrograms).

METHODS

Bronchial reversibility (percentage change in baseline forced expiratory volume in one second (FEV1)) was measured in 26 patients with chronic bronchitis on three separate occasions, at least one week apart. Tracheobronchial clearance was evaluated by a non-invasive radioaerosol technique, and an oscillatory viscometer was used for measuring sputum apparent viscosity and elasticity. The number of coughs (productive and nonproductive coughs), the wet weight of sputum, and its radioaerosol content were recorded during the six hour clearance period, as well as the 24 hour sputum production.

RESULTS

The change in FEV1 after fenoterol was less than 15% in 12 patients and more than 15% in 14. Patients with airways reversibility of more than 15% had faster tracheobronchial clearance, more coughs, lower sputum viscosity and elasticity, and larger 24 hour sputum production than those with airways reversibility of less than 15%.

CONCLUSIONS

In patients with chronic bronchitis a large bronchodilator response is associated with faster clearance of mucus by mucociliary transport and coughing.

Effect of forced expirations on mucus clearance in patients with chronic airflow obstruction: effect of lung recoil pressure

Spontaneous mucus clearance and the effect of forced expirations and coughing on mucus clearance were investigated in eight patients with chronic airflow obstruction and low elastic recoil pressure (emphysema group: mean FEV1 45% predicted) and in seven patients with chronic airflow obstruction and normal elastic recoil pressure (chronic bronchitis group: mean FEV1 57% predicted). Mucus clearance was measured in a central and a peripheral lung region by a radioactive aerosol tracer technique. Spontaneous mucus clearance from the peripheral lung region was higher in the patients with emphysema than in those with chronic bronchitis. There was no difference in central mucus clearance between the two groups. Mucus clearance from the peripheral lung region increased significantly during forced expirations and coughing in the patients with chronic bronchitis but not in those with emphysema. It is concluded that in patients with chronic airflow obstruction and regular sputum production spontaneous peripheral mucus clearance is greater in those with decreased elastic recoil pressure. Physiotherapy that includes forced expirations and coughing can enhance mucus clearance in such patients when elastic recoil pressure is normal but is unlikely to be effective when elastic recoil pressure is decreased.

Mobilization of mucus by airway oscillations

The effects of high frequency asymmetric airway oscillations on mucus clearance were evaluated in excised tracheas of sheep, in an animal model of excessive mucus production, and in patients with bronchiectasis. Asymmetric high frequency ventilation (15 Hz) with expiratory biased flow profiles (expiratory peak-flow greater than inspiratory peak-flow) could move mucus droplets towards the pharynx in rigid and flexible tracheas by gas-liquid interaction. In rigid tracheas the mucus was transported towards the periphery of the model lung if the oscillations were inspiratory biased. In very collapsible tracheas, however, even inspiratory biased oscillations moved the mucus cephalad. Parameters influencing direction and speed of mucus are airflow profile, peak-flow, airway compliance and lung resistance. Gamma-camera studies showed that in anesthetized dogs radiolabeled artificial mucus followed the direction of the bias during high frequency ventilation. In five human volunteers with bronchiectasis and excessive secretions the asymmetric airway oscillations were superimposed during spontaneous breathing using a mouthpiece. Airway wall vibrations following the pressure swings of the oscillator could be observed. During forced expiration inward bulging of the posterior membranes of trachea and bronchi occurred at the negative pressure phase of the oscillations. This event was associated with increased appearance of sputum in the central airways. We conclude that high frequency ventilation with asymmetric flow profiles applied via tube or mouthpiece might be an effective future treatment of mucostasis.

Removal of bronchial secretions by two-phase gas-liquid transport

Net outward wave motion of secretions from airways by two-phase gas-liquid transport is favored by higher airflow during expiration than inspiration. This can be accomplished by IRV in which the controlled mode of mechanical ventilation is adjusted such that the inspiratory cycle is prolonged and the expiratory phase is shortened. Studies were done on six anesthetized, nasally intubated sheep. Simulated mucus was instilled into the bronchi at 15-min intervals during I-E ratio of 1:2.7, 1.9:1, and 3:1. The IRV modes of 1.9:1 and 3:1 promoted transport of simulated mucus outward. Neither systemic blood pressure nor cardiac output were altered by IRV. Thus, IRV might be useful in the management of excessive bronchial secretions in mechanically ventilated patients. However, clinical trials of IRV should take into account its potential for producing adverse hemodynamic effects and barotrauma in patients with compromised cardiac function due to auto-PEEP attendant with its usage.