populations, pathophysiological models, risk factors and the adverse health consequences this brings [1]. Individuals suffering breathlessness not explained by objective measures of disease, prove challenging to clinicians. The neurocognitive basis of breathlessness is therefore important, and chapter 2 on the neuroscience of breathlessness offers a useful consideration of current theories of perception applied to the understanding of breathlessness [2]. To cement the foundations, chapter 3 examines the physiology of breathlessness and summarises how specific physiological factors may contribute to symptoms, offering guidance on how these should be measured [3]. Next, assessment guidance is provided in chapter 4, initially exploring the tools required and available, followed by a discussion on the appropriateness of tool selection, depending on which aspect of breathlessness is under review [4]. This then leads into a useful chapter detailing a systematic clinical approach to assessing complex breathlessness, which includes points for a comprehensive evaluation with a focus on the nature and impact of the patient’s breathlessness symptom(s) [5]. Airway-focused chapters follow to educate the reader on specific disorders associated with complex breathlessness, including: laryngeal considerations in chapter 6, with detail on inducible laryngeal dysfunction excessive airways collapse in chapter 7 BPD in chapter 8 and allergic factors in chapter 9 [6–9]. Each chapter provides a summary overview, associated assessment specifics and management approaches. Cardiopulmonary vascular considerations are next addressed to provide detailed insight into uncommon but often overlooked causes of breathlessness. These include pulmonary vascular causes in chapter 10, cardiovascular drivers in chapter 11 and autonomic dysfunction presentations, including PoTS, in chapter 12 [10–12]. The final chapters of the Monograph are dedicated to overall holistic management [13–15]. Suboptimal treatment adherence, whether intentional or not, has the potential to play a role in amplifying the complexity of breathlessness and its management, so this is explored first [13]. The subsequent chapters then provide an invaluable lens on the latest evidence on treating unexplained breathlessness holistically [14, 15]. We are particularly grateful to our authors and reviewers, who have dedicated their time and expertise to enable this Monograph to come to fruition. We would also like to acknowledge the support given to us by the ERS Monograph team who have expertly guided us throughout. We hope readers will find this resource a useful guide to support the assessment and management of individuals who present with seemingly “unexplained” or complex breathlessness. References 1 Ekström M, Johnson MJ, Currow DC, et al. The epidemiology of breathlessness. In: Hull JH, Haines J, eds. Complex Breathlessness (ERS Monograph). Sheffield, European Respiratory Society, 2022 pp. 1–14. 2 Pick A, Gnanarajah S, Fraser E, et al. The neuroscience of breathlessness. In: Hull JH, Haines J, eds. Complex Breathlessness (ERS Monograph). Sheffield, European Respiratory Society, 2022 pp. 15–23. 3 Sylvester KP, Rolland-Debord C, Ong-Salvador R, et al. The physiology of breathlessness. In: Hull JH, Haines J, eds. Complex Breathlessness (ERS Monograph). Sheffield, European Respiratory Society, 2022 pp. 24–38. 4 Lewthwaite H, Jensen D. Tools for assessing complex breathlessness. In: Hull JH, Haines J, eds. Complex Breathlessness (ERS Monograph). Sheffield, European Respiratory Society, 2022 pp. 39–60. 5 Fowler SJ, Pantin CT. A systematic approach to assessing complex breathlessness. In: Hull JH, Haines J, eds. Complex Breathlessness (ERS Monograph). Sheffield, European Respiratory Society, 2022 pp. 61–74. https://doi.org/10.1183/2312508X.10015522 xi