Normal Routine Spirometry Can Mask Chronic Obstructive Pulmonary Disease and Emphysema and Asthma in Symptomatic Patients

[...]the ATS issued an official technical statement that concluded that FEF75% and FEF25-75% have not demonstrated added value for identifying obstruction in adults and children with normal routine spirometry.8 Unfortunately, this ATS statement is in contrast to published data in asthma and COPD/emphysema, as noted previously, that identify small airway obstruction despite normal routine spirometry by abnormal FEF25-75% and especially FEF75%. [...]Hogg et al11 reported that in the presence of COPD, with or without emphysema, the distal quiet small bronchiolar zone was the major site of increased airway resistance. When all upper airway resistance is included, the contribution of small airway resistance to total airway resistance is probably ≤̇15%.10,11 This paradigm could be further obscured by normal expiratory spirometry measurements consistent with “preserved pulmonary function” as previously reported.Acknowledgments I would like to thank Noe Zamel, MD, Professor of Pulmonary Medicine, University of Toronto, Faculty of Medicine, Toronto, Ontario, Canada, for pulmonary physiologic collaboration (deceased) and my mentor Jay A. Nadel, MD, Emeritus Professor and Director Cardiovascular Research Institute and Departments of Medicine, Physiology, and Radiology, University of California San Francisco, School of Medicine, San Francisco, California.