NON-INVASIVE RESPIRATORY SUPPORT IS A PRO-INFLAMMATORY STIMULUS TO THE UPPER AND LOWER AIRWAYS Mohammed D. AlAhmari MSc RRT A thesis submitted for the degree of Doctor of Philosophy UCL, UK 2012 Centre for Respiratory Medicine Royal Free Campus University College London 1 DECLARATION “I, Mohammed Dhafer AlAhmari, confirm that the work presented in this thesis is my own except for the help listed in the acknowledgements. Where information has been derived from other sources, I confirm that this has been indicated in the thesis” Signuture: ………………… Date: ……………………… 2 ACKNOWLEDGEMENTS It is with my sincerest gratitude that I take this opportunity to thank those without whom this PhD thesis would not have been possible. Firstly, I especially want to express my deepest thanks to Professor Wisia Wedzicha who accepted me into her Centre of Respiratory Medicine and supported me throughout my PhD study. I would also like to thank my supervisor Dr. John Hurst, for his valuable guidance and insightful advice, encouragement, patience, and his suggestions and constant support during my PhD journey. Thank you for being so easy to approach at any time! I am certain that the completion of my thesis would not have been possible without his guidance. Special thanks goes to Ray Sapsford, our lab manager, for helping, teaching and assisting me with sample processing and analysing, and the setup of the in-vitro study. I would also like to express my thanks to Christine Mikelsons, Consultant Respiratory Physiotherapy, who helped and assisted me in the recruitment of OSA patients. Without her support, I believe the study of OSA would not have been possible to do. Thank you! I would also like to thank Gavin Donaldson who assisted with the power calculations of the thesis, and the suggestions he gave whenever I approached him. I would like to that the following colleagues for their help and support: Dr. James Goldring, Dr. Anant Patel, Dr. Alex Mackay, Beverly Kowlessar, and all other department colleagues for their friendship and help they readily gave during the process. This work would not have been possible without the generosity of the healthy volunteers and the patience they displayed while being on the CPAP machine for three hours. My thanks also go to OSA and COPD patients and their families. I would like to thank the Saudi Ministry of Higher Education for supporting my studies and the sponsorship of my PhD. 3 Last, but not least, I thank my wife and my three beautiful children for their understanding and support throughout my entire educational process. 4 ABSTRACT Non-invasive respiratory support (NIV) is associated with a high prevalence of local side- effects which may be associated with induction of upper airway inflammation. This thesis examines the effect of NIV on the upper and lower airway by examining bronchial epithelial cell cultures, healthy subjects, obstructive sleep apnoea (OSA), and chronic obstructive pulmonary disease (COPD) patients. The rationale for this thesis is based on reports suggesting that continuous positive airway pressure (CPAP) may induce early upper airway inflammation, and discusses the relationship between upper and lower airways in COPD. To examine the addressed rationale we used both an in vitro and in vivo approach. In vitro, we examined the release of the inflammatory cytokines from a human bronchial epithelial cell line over time-intervals using CPAP therapy. In vivo studies investigated whether induction of nasal inflammation was associated with the development of systemic inflammation, nasal symptoms, and changes in nasal mucociliary clearance after a short period of CPAP therapy. Results were investigated further in OSA by investigating whether induction of nasal inflammation was associated with the development of systemic inflammation, nasal symptoms, airway obstruction, and impaired adherence to CPAP therapy and quality of sleepiness over a six months follow-up period. Additional pilot data obtained involved a comparison of local and systemic inflammatory indices in COPD patients using and not using NIV. The key finding was that CPAP is pro-inflammatory. The in vitro data showed that CPAP resulted in the release of inflammatory mediators from cultured human bronchial epithelial cells, in a time-and-pressure-dependent manner. Meanwhile, in vivo data from healthy control subjects showed CPAP was associated with dose (pressure) response changes in nasal and systemic inflammatory markers, reduced nasal function, and the development of nasal symptoms. The development of nasal symptoms was associated with the degree of functional impairment and nasal inflammatory response. These in vitro and in vivo results were novel in reporting the effects of CPAP in this way, providing new data on the mechanisms of CPAP intolerance in the crucial, early phase of therapy. Furthermore, the long-term CPAP study with OSA resulted in nasal inflammation, reduction in nasal 5 mucociliary function, and significant other adverse effects. However, sleep quality and the perceived benefits of therapy improved over time, despite the presence of side-effects. These results have important implications for clinical practice, since it demonstrates a relationship between nasal symptoms, mucociliary clearance, inflammation and compliance in patients with OSA initiating and continuing CPAP therapy. Further investigation of strategies to combat the initial side-effects and nasal inflammation associated with this treatment modality might target the epithelial lining of the nose in an attempt to address the origin of the inflammatory response. In addition, educational and support strategies to improve patients‟ tolerance of side effects may further increase compliance with nasal CPAP treatment for OSA patients. 6 ABBREVIATIONS °C Degree Celsius AASM American Academy of Sleep Medicine AAT Alpha1-antitrypsin AECOPD Acute exacerbation of chronic obstructive pulmonary disease AHI Apnoea-Hypopnoea Index AHR Airway hyperresponsiveness ALI Acute lung injury ANOVA Analysis of Variance AR Acoustic rhinometry ARDS Acute Respiratory Distress Syndrome BEAS-2B Bronchial epithelial cell line BMI Body-mass index BODE Body mass index, obstruction, dyspnea, exercise capacity index cm Centimeter CO Carbon monoxide CO2 Carbon dioxide COPD Chronic Obstructive Pulmonary Disease CPAP Continuous positive airway pressure CRP C-reactive protein CSA Cross sectional area CT Computed Tomography CV Coefficient of variation CXCR Chemokine receptor D-MCA Distance of cross-sectional area from nasal orifice EBC Exhaled breath condensate ECM Extracellular matrix ECP Eosinophil cationic protein 7 EDS Excessive daytime sleepiness EEG Electroencephalography ELISA Enzyme-linked immunosorbent assay EPAP Expiratory positive airway pressure EPO Erythropoietin ESS Epworth Sleepiness Scale ETDA Ethylenediaminetetraacetic acid FeNO Fractional exhaled nitric oxide FEV1 Forced expiratory volume in 1 second FRC Functional residual capacity FVC Forced vital capacity GOLD Global Initiative for Chronic Obstructive Lung Disease GPRD General Practice Research Database GSH Glutathione H2O Water (hydrogen dioxide) ICAM-1 Inter-Cellular Adhesion Molecule-1 ICC Intraclass correlation coefficients IF Inflammatory factors IFN-γ Interferon-gamma IL Interleukin IPAP Inspiratory positive airway pressure IPPV Intermittent positive pressure ventilation Kg Kilogram L Liter MCA1 First minimum cross-sectional area MCA2 Second minimum cross-sectional area MMP Matrix metalloproteinases MPO Myeloperoxidase MRI Magnetic Resonance Imaging MSLT The multiple sleep latency test 8 N Number NaCl Sodium chloride nCPAP Nasal continuous positive airway pressure NHS National Health Service NIV Non-invasive ventilation MCC mucociliary clearance NO Nitric oxide O2 Oxygen OSA Obstructive sleep apnoea P Pressure PaCO2 Partial arterial pressure of carbon dioxide Paw Airway pressure PBS Phosphate buffered saline PEEP Positive end-expiratory pressure PEFR Peak expiratory flow rate PND Post-nasal drip R Pearson correlation co-efficient RDI Respiratory disturbance index Rho Spearman rank correlation co-efficient RMM Rhinomanometry rpm revolutions per minute S Second SaO2 Blood oxygen saturation SGRQ St. George‟s Respiratory Questionnaire STT Saccharin transit time SD Standard deviation STT Saccharin transit time T Temperature TIMP Tissue inhibitors of matrix metalloproteinases TCC Total cell count 9 TGF-β Transforming growth factor-beta TNF-α Tumour necrosis factor-alpha UARS Upper airway resistance syndrome UK United Kingdom μm Micrometer USA United States of America V Volume v/v volume for volume nd th V2-5 Volume of nasal cavity between the 2 and 5 cm from nasal orifice VEGF Vascular endothelial growth factor VIP Vasoactive intestinal peptide VT Tidal volume w/v Weight/volume WHO World Health Organization WOB Work of breathing VEGF Vascular endothelial growth factor 10 TABLE OF CONTENTS 2 DECLARATION ACKNOWLEDGEMENTS 3 ABSTRACT 5 ABBREVIATIONS 7 TABLE OF CONTENTS 11 LIST OF TABLES 21 LIST OF FIGURES 23 LIST OF PLATES 26 Chapter 1 INTRODUCTION 27 1.1 OVERVIEW OF THE RESPIRATORY SYSTEM 27 1.1.1 Structure of Upper Airway 29 1.1.1.1 Part of the Upper Respiratory Tract 29 1.1.2 Structure of Lower Airway 30 1.1.2.1 Part of the Lower Respiratory Tract 31 11 1.2 CONTINUOUS POSITIVE AIRWAY PRESSURE 33 (CPAP) 1.2.1 Definition and History 33 1.2.2 Indications and Contraindications of CPAP Therapy 35 1.2.2.1 Indications of CPAP Therapy 35 1.2.2.2 Contraindications of CPAP Therapy 35 1.2.2.3 CPAP-Related Side Effects 36 1.3 BiLEVEL