Validating the Use of Disposable Bronchoscopes for Research Bronchoalveolar Lavage

Research bronchoscopies are traditionally performed using conventional flexible fibreoptic bronchoscopes. The technique for obtaining bronchoalveolar lavage fluid (BAL) from healthy volunteers for research purposes has been developed by our group since 1999 and has been performed in > 1,000 subjects in the UK and Malawi including healthy volunteers.

Fibreoptic bronchoscopy with BAL using manual hand held suction enables the removal of non-adherent cells and lung lining fluid from the mucosal surface. In research environments, BAL allows sampling of innate (lung macrophage), cellular (B- and T- cells), and humoral (immunoglobulin) responses within the lung. Further applications include determining protein and drug levels, with the latter being a key parameter in early phase 'lung tissue active' drug development.

The BAL technique uses gentle hand-held suction of instilled fluid; this is designed to maximize BAL volume returned, and to apply minimum shear force on ciliated epithelia in order to preserve the structure and function of cells within the BAL fluid. This technique is also intended to preserve viability to facilitate the growth of cells in ex vivo culture. The research technique therefore uses a larger volume of warmed normal saline instillate (typically in the order of 200 ml) and employs manual suction to reduce cell damage.

At the Royal Liverpool Hospital (RLBUHT) ≥120 healthy volunteer BALs have been performed. Available data suggest that from 200 ml of instillate the following volume yields are retrieved: mean 100-120 ml, median 120 - 125 ml with ~ 19% of BALs returning <100 ml yield. The preferable BAL volume yield is >100 ml, a yield of >150 ml is considered excellent; yields >170 ml have not been recorded. There is no linear relationship between the cell yield and volume yield. Yields of <100 ml are in our experience, more likely to lead to side effects such as cough, chest pain and fever. Subjects with yields of <100 ml are advised to be recovered in the left lateral position to aid postural drainage of remaining instillate. There have been no serious adverse events (SAEs) reported; and notably there have been no post procedure hospitalisations or antibiotics required for suspected pneumonia.

Single-use flexible intubation bronchoscopes are used throughout United Kingdom (UK) National Health Service (NHS) trusts. They are predominantly used within the intensive care and anaesthetic (theatre) setting for both emergency and elective airway intubation. The flexible fibreoptic bronchoscope with sterile single-use disposable-sheath endoscope system has the potential to be more cost-effective and reduce the risk, however negligible, of cross-infection during the sterilisation procedure. Eliminating the need for high-level disinfection processing between procedures reduces maintenance costs (equipment and staff), and scope downtime and provides the flexibility more suited for research in healthy volunteers.

The content of this study proposal has been peer reviewed by two senior research associates based in Malawi and the UK who have deemed the scientific review criteria to be sound.

Currently many new drug and therapeutics discovery and development projects are blighted by the absence of robust predictive pre-clinical models. For example, promising anti-tuberculosis (TB) drugs and drug combinations have been clinically trialled based on current in vitro and in vivo models, only to find that they lack clinical efficacy; and conversely effective anti-TB drugs such as linezolid had poor or modest efficacy in testing usingin vitro and in vivo models. To mitigate these issues we have therefore developed dynamic pharmacodynamic in vitro models based on high content imaging that are able to measure macrophage intracellular tubercular growth and killing rates. Pharmacodynamic (PD) and Pharmacokinetics (PK) modelling of these models more closely resemble clinical measurements for known first line anti-TB; therefore we now wish to further develop this platform into a more physiological model by using alveolar macrophages (AMs) obtained from human subjects.

The purpose of using human AMs will be to compare the drug effects of known and new anti-TB compounds in human AMs to other in vitro models. This work will enable us to obtain better, more clinically relevant parameters to predict the outcome of drug dynamics. By using the AMswe can assess how reliable our current model systems are, and assess considerations of drug action in clinically relevant tissue samples. These cells can then be manipulated ex vivo to desired clinical scenarios e.g. dual TB and HIV-infections monitoring TB responses over time to a range of novel drugs and novel drug combinations. The outputs of these studies will be used directly to inform new clinical trials on drug regimens.