Nasal Peak Inspiratory Flow in Healthy and Obstructed Patients: Systematic Review and Meta-Analysis Shirley Mo, MD ; Sai S. Gupta, MD; Anna Stroud, BHlth; Erika Strazdins, MD; Aneeza W. Hamizan, MD ; Janet Rimmer, MD; Raquel Alvarado, PhD; Larry Kalish, MD, MS, MMed (Clin Epi); Richard J. Harvey, MD PhD Objectives: Nasal peak inspiratory flow (NPIF) is a practical and affordable tool that measures maximum inspiratory flow rate through both nostrils. Although NPIF values for healthy controls and patients appear to differ considerably, a generally expected value for populations with and without nasal obstruction has yet to be established. The aim of this systematic review and meta-analysis was to determine the mean NPIF value in populations with and without nasal obstruction. Methods: Medline (1946–) and Embase (1947–) were searched until July 1, 2017. A search strategy was used to identify studies that reported NPIF values for defined healthy or disease states. All studies providing original data were included. The study population was defined as having either normal nasal breathing or nasal obstruction. A meta-analysis of the mean data was presented in forest plots, and data were presented as mean (95% confidence interval [CI]). Results: The search yielded 1,526 studies, of which 29 were included. The included studies involved 1,634 subjects with normal nasal breathing and 817 subjects with nasal obstruction. The mean NPIF value for populations with normal nasal breathing was 138.4 (95% CI: 127.9-148.8) L/min. The mean value for populations with nasal obstruction was 97.5 (95% CI: 86.1-108.8) L/min. Conclusions: Current evidence confirms a difference between mean NPIF values of populations with and without nasal obstruction. The mean value of subjects with no nasal obstruction is 138.4 L/min, and the mean value of nasally obstructed populations is 97.5 L/min. Prospective studies adopting a standardized procedure are required to further assess normative NPIF values. Key Words: Nasal peak inspiratory flow, peak nasal inspiratory flow, nasal obstruction, normal breathing. Laryngoscope, 00:1–8, 2020 INTRODUCTION Nasal obstruction is a common complaint in ear, nose, and throat (ENT) practices. The most widely used assess- ment tools for measuring nasal obstruction are nasal peak inspiratory flow (NPIF), rhinomanometry (RM), and acoustic rhinometry (AR). 1 RM measures nasal airway resistance, 2 whereas AR detects the minimum cross-sectional area and volume inside the nose at predetermined points. 1 NPIF mea- sures the maximum flow rate through both nostrils during inspiration. 3 Although RM and AR both rely on complex and expensive equipment that limits use to highly trained operators, 4 NPIF is a simple, practical, and affordable test that does not require significant technical expertise to perform or a computer for data analysis. 5 The proce- dure requires an inverted flow meter to be attached to an anesthetic face mask, which is then positioned over the patient’s nose and mouth to form an airtight seal. 1 The patient then inspires forcefully through their nostrils with their lips closed (Fig. 1). 6 NPIF can be used in clinical practice, home settings, and for serial measurements in both adult and pediatric populations. 7,8 It can be used to distinguish decongestable from structural nasal obstruction 9 to assess the benefit of pharmacological or surgical therapy, 10,11 and to select patients who will benefit most from rhinologic procedures. 12 NPIF is reproducible with an intraclass correlation coeffi- cient (ICC) ranging from 0.89 to 0.92. 4,13 Values between 90 L/min to 120 L/min are also sensitive and specific for detecting nasal obstruction, 4,14,15 with a minimal clinically important difference being established at 20 L/min. 16 Given the wide utility of NPIF and availability of diagnostic From the Rhinology and Skull Base Research Group, St. Vincent’s Centre for Applied Medical Research (S.M., S.S.G., A.S., E.S., A.W.H., J.R., R.A., L.K., R.J.H.), University of New South Wales, Sydney, New South Wales, Australia; Department of Otolaryngology–Head and Neck Surgery (A.W.H.), Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia; St. Vincent’s Clinic, St. Vincent’s Hospital (J.R.), Sydney, New South Wales, Australia; The Woolcock Institute, Sydney University (J.R.), Sydney, New South Wales, Australia; Sydney Medical School, University of Sydney (L.K.), Sydney, New South Wales, Australia; Department of Otolaryngology– Head and Neck Surgery (L.K.), Concord General Hospital, University of Sydney, Sydney, New South Wales, Australia; and the Faculty of Medicine and Health Sciences (R.J.H.), Macquarie University, Sydney, New South Wales, Australia. Additional supporting information may be found in the online version of this article. Editor’s Note: This Manuscript was accepted for publication on March 13, 2020. R.J.H. is a consultant with Medtronic, Olympus, and NeilMed phar- maceuticals. He has also been on the speakers’ bureau for Glaxo-Smith- Kline, Seqirus, and Astra-Zeneca. J.R. has honoraria with Sanofi Aventis, Novartis, Mundipharma, BioCSL, and Stallergenes. L.K. is on the speakers’ bureau for Care Pharmaceuticals and Mylan Pharmaceuticals. The authors have no other funding, financial relationships, or con- flicts of interest to disclose. Send correspondence to Shirley Mo, 67 Burton Street, Darlinghurst, NSW 2010, Australia. E-mail: shirley.mo@outlook.com.au DOI: 10.1002/lary.28682 Laryngoscope 00: 2020 Mo et al.: NPIF in Normal Controls and Nasal Obstruction 1 The Laryngoscope © 2020 The American Laryngological, Rhinological and Otological Society, Inc.