Physiological predictors Of peak inspiRatory flow using Observed lung function resultS (POROS): evaluation at discharge among patients hospitalized for a COPD exacerbation

Longitudinal Changes in Maximal Forced Inspiratory Flow and Clinical Outcomes in Patients With COPD

BACKGROUND

COPD primarily impairs expiratory flow due to progressive airflow obstruction and reduced lung elasticity. Increasing evidence underlines the importance of inspiratory flow as a biomarker for selecting inhaler devices and providing ancillary aerodynamic information.

RESEARCH QUESTION

Does the longitudinal changes in maximum forced inspiratory flow (FIFmax) influence acute exacerbations and lung function decline in patients with COPD?

STUDY DESIGN AND METHODS

This longitudinal study evaluated FIFmax in patients with COPD over a 7-year period from 2004 to 2020. Eligible patients were categorized into 2 groups based on FIFmax trajectory: the increased FIFmax group and the decreased FIFmax group. The study assessed the annual rate of acute exacerbations and the annual decline rate of FEV1. Subgroup analyses were conducted based on treatment status, with a focus on inhaled therapy and inhaler device usage.

RESULTS

Among the eligible 956 patients with COPD, 56.5% belonged to the increased FIFmax group. After propensity score matching, the increased FIFmax group experienced lower rates of severe exacerbations (0.16 per year vs 0.25 per year, P = .017) and a slower decline in FEV1 (0 [interquartile range, -51 to 71] mL/y vs -43 [interquartile range, -119 to 6] mL/y; P < .001) compared with the decreased FIFmax group. These associations were particularly prominent in patients using specific inhaler therapies such as dry powder inhalers.

INTERPRETATION

This study showed that the longitudinal changes in FIFmax are associated with clinical outcomes in patients with COPD. Patients with increased FIFmax experienced a lower rate of severe exacerbations and a slower decline in lung function. These findings suggest the potential benefits of optimizing inspiratory flow in COPD management, although further studies are needed to confirm these observations due to potential confounding factors.

Changes in Peak Inspiratory Flow After Acute Bronchodilation: An Observational Study of Patients with Stable Chronic Obstructive Pulmonary Disease

Introduction: Identifying factors influencing peak inspiratory flow (PIF) is essential for aerosol drug delivery in stable patients with chronic obstructive pulmonary disease. While a minimum PIF for dry powder inhalers (DPIs) is established, acute bronchodilator (BD) effects on PIF remain unknown. Materials and Methods: An inspiratory flow meter (In-Check™ DIAL) was used to measure PIF in stable patients during a 24-week observational cross-sectional study. Additionally, bronchodilator responsiveness (BDR) was determined using the In-Check DIAL device and spirometry. Patients received four puffs of albuterol, and pre- and post-BD PIF, forced expiratory volume in one second (FEV1), and forced vital capacity were measured. Sixty-three patients completed acute BDR data collection from July 31, 2019, to November 9, 2021. Primary endpoints were pre- and post-BD spirometry and PIF. Statistical analyses included PIF correlations with FEV1. BD change was assessed according to inhaler resistance and sex (subgroup analysis). Results: Median patient age was 64.8 years, 85.7% were non-Hispanic White, and 57.1% were female. The median increase in absolute PIF (In-Check DIAL) was 5.0 L/min, and the % PIF change was 8.9%. With albuterol, 57.1% experienced a PIF BD change >5.0%, whereas 49.2% experienced a change >10.0%. Similarly, 55.6% experienced an FEV1 BD change >5.0% and 28.6% had a >10.0% FEV1 BD change with albuterol. PIF was weakly correlated with FEV1 BD change (absolute; % PIF; r = 0.28 [p = 0.02]; r = 0.21 [p = 0.11]). Pre- and post-BD median PIF were 75.5 and 83.5 L/min for low-to-medium-resistance DPI and 45.0 and 52.0 L/min for high-resistance, respectively. The median increases in pre- and post-BD PIF were 9.0 L/min in males and 4.5 L/min in females. In contrast to when using the In-Check DIAL device, we observed no consistent bronchodilatory effects on PIF measured by spirometry. Conclusions: Using the In-Check DIAL device, ∼50% of patients experienced >10% PIF increase after acute BD, potentially enhancing medication lung deposition. Further research is required to understand PIF's impact on medication delivery. ClinicalTrials.gov Identifier: NCT04168775.

Prevalence of Critical Errors and Insufficient Peak Inspiratory Flow in Patients Hospitalized with COPD in a Department of General Internal Medicine: A Cross-Sectional Study

Background

The suboptimal use of inhalers in the treatment of patients with chronic obstructive pulmonary disease (COPD) is probably a major but poorly documented problem in hospitalized patients. We aimed to describe the prevalence of misused inhalers among patients hospitalized with COPD in a department of general internal medicine.

Methods

We conducted a monocentric cross-sectional study in consecutive patients with a diagnosis of COPD and hospitalized between August 2022 and April 2023 in the internal medicine division of Fribourg Hospital, Switzerland. Patients underwent an assessment of their inhaler technique and peak inspiratory flow (PIF) using the In-Check Dial G16®. The primary outcome was the prevalence of misused inhalers, defined as an inhaler used with a critical error and/or insufficient PIF. Secondary outcomes included the prevalence of inhalers unsuitable to patients' characteristics and of patients using at least one misused inhaler.

Results

The study included 96 patients and 160 inhalers were assessed at admission. Among these inhalers, 111 (69.4%; 95% confidence interval [CI] 61.6-76.4) were misused; 105 (65.6%; 95% CI 57.7-72.9) due to the presence of a critical error in the inhalation technique and 22 (13.8%; 95% CI 8.8-20.1) due to insufficient PIF. Concerning the secondary outcome, 27 inhalers (16.9%) were unsuitable, and 79 patients (82.3%) used at least one misused inhaler.

Conclusion

Among patients hospitalized with a diagnosis of COPD, two-thirds of inhalers were misused. Suboptimal use was mainly due to the presence of critical errors, but also to the presence of an insufficient PIF and unsuitable inhalers.

Clinical Burden of Chronic Obstructive Pulmonary Disease in Patients with Suboptimal Peak Inspiratory Flow

Introduction

Many patients with chronic obstructive pulmonary disease (COPD) may derive inadequate benefit from dry powder inhalers (DPIs) because of suboptimal peak inspiratory flow (sPIF).

Objectives

To assess the clinical burden of COPD by characterizing the clinical characteristics of participants with sPIF against medium-low resistance DPIs versus those with optimal PIF (oPIF) from two phase 3 clinical trials.

Methods

Baseline data were collected from two randomized, controlled, phase 3 trials (NCT03095456; NCT02518139) in participants with moderate-to-severe COPD. oPIF (60 L/min) against the medium-low resistance DPIs was used as the threshold for defining the PIF subgroups (<60 L/min (sPIF) vs ≥60 L/min (oPIF)).

Results

Most participants included in this analysis were White (92%) and male (63%); the mean (range) age was 65 (43-87) years. Participants with sPIF had significantly greater dyspnea than those with oPIF as measured using the modified Medical Research Council scoring (mean (95% CI): 2.1 (2.0-2.2) vs 1.6 (1.4-1.7); P  < 0.001) and baseline dyspnea index (mean (95% CI): 5.1 (4.9-5.4) vs 6.1 (5.8-6.3); P  < 0.001). Based on COPD Assessment Test scores, participants with sPIF had a higher COPD symptom burden than those with oPIF (mean (95% CI): 21.5 (19.7-23.3) vs 19.5 (18.6-20.4); P = 0.05).

Conclusion

In these trials, participants with COPD who had sPIF against the medium-low resistance DPIs had more dyspnea and worse health status than those with oPIF. These results demonstrate that sPIF is associated with a higher clinical burden as measured by patient-reported outcomes.

Consideration and Assessment of Patient Factors When Selecting an Inhaled Delivery System in COPD

Because guidelines and strategies for pharmacologic treatment of COPD focus on specific classes of inhaled medications, there is an unmet need for information to guide health care professionals for selecting an inhaled medication delivery system that matches the unique characteristics of individual patients. This article provides guidance for selecting an inhaled medication delivery system based on three "key" patient factors: cognitive function, manual dexterity/strength, and peak inspiratory flow. In addition, information is provided about specific tests to assess these patient factors. Cognitive impairment with an estimated prevalence of 25% among patients with COPD adversely affects patients' ability to correctly use a handheld device. To our knowledge, the prevalence of impaired manual dexterity/strength has not been reported in those with COPD. However, 79% of patients with COPD have reported one or more physical impediments that could influence their ability to manipulate an inhaler device. The measurement of peak inspiratory flow against the simulated resistance (PIFr) of a dry powder inhaler establishes whether the patient has the inhalation ability for creating optimal turbulent energy within the device. A suboptimal PIFr for low to medium-high resistance dry powder inhalers has been reported in 19% to 84% of stable outpatients with COPD. Health care professionals should consider cognitive function, manual dexterity/strength, and PIFr in their patients with COPD when prescribing inhaled pharmacotherapy. Impairments in these patient factors are common among those with COPD and can affect the individual's competency and effectiveness of using inhaled medications delivered by handheld devices.

Exploration of quality criteria for the detection of peak inspiratory flow under different resistance conditions

BACKGROUND

At present, robust quality criteria and methods for the assessment of Peak inspiratory flow meter performance are lacking.

OBJECTIVE

A standard flow-volume simulator for quality control analyses of an inhalation assessment device was utilized with different simulated resistance levels in order to propose a quality testing method and associated standard for this device type.

METHODS

A standard flow-volume simulator was utilized to assess the performance of an In-Check DIAL® (Device I) and an intelligent inhalation assessment device (Device P) at a fixed volume and flow rate. Indices used to evaluate these two instruments included repeatability, accuracy, linearity, and impedance.

RESULTS

Both devices exhibited good repeatability (<± 3 L/min). The difference between test results and standard simulator values for Device P was less than ± 5 L/min at resistance level R1 but higher than ± 5 L/min at resistance levels R2-5, while Device I were greater than 5 L/min at all resistance levels. The relative error for Device P was <± 10% at resistance levels R1, R2, and R4, but > 10% at resistance levels R3 and R5. The relative error values for Device I at all five resistance levels were > 10%. Device P passed the linearity test at the R2 resistance level, while Device I partially passed the linearity test at all five resistance levels.

CONCLUSION

Standard monitoring methods and standards provide a valuable approach to the more reliable clinical assessment and application of these instruments.

High inhaler resistance does not limit successful inspiratory maneuver among patients with asthma or COPD

INTRODUCTION

There has been an active discussion on the sustainability of inhaler therapy in respiratory diseases, and it has cast a shadow on pMDIs which rely on propellant with high global warming potential (GWP). DPIs offer a lower GWP and effective alternative, but there has been concern whether all patients can generate sufficient inspiratory effort to disperse the drug. This review focuses on airflow resistance of DPIs and its clinical relevance.

AREAS COVERED

For this narrative review, we searched the literature for studies comparing flow patterns with different devices. We also included a section on clinical trials comparing reliever administration with DPI, pMDI with spacer, and nebulizer during exacerbation.

EXPERT OPINION

The evidence supports the efficacy of DPIs irrespective of respiratory condition or age of the patient even during acute exacerbations. Air flow resistance does not limit the use of DPIs and the patients were able to generate sufficient inspiratory flow rate with almost any device studied. None of 16 identified clinical trials comparing reliever administration via DPIs to other types of devices during exacerbation or bronchial challenge showed statistically significant difference between the device types in FEV1 recovery. DPIs performed as well as other types of inhaler devices even during asthma or COPD exacerbation.

Maximal inspiratory and expiratory flow at moderate altitude: a study of a Latin American population

Background

Peak inspiratory and expiratory flows (PIF, PEF) are parameters used to evaluate the mechanics of the respiratory system. These parameters can vary based on whether they are measured using mechanical devices vs. spirometry and based on the barometric pressure at which the measurements are obtained. Our objectives were (1) to report the normal values and variability of PEF and PIF of a Latin American population living at a moderate altitude (2240 m above sea level), (2) to analyze the adjustment of reference values obtained at sea level with those obtained in healthy subjects living at a moderate altitude, and (3) to assess the correlation between PEF obtained by spirometry (PEFs) and PEF obtained by mechanical devices (PEFm).

Methods

In this prospective and transversal study, men and women with good respiratory health aged between 2.8 and 68 years old were invited to participate. Randomly, they underwent spirometry (to measure PEFs and PIFs) and mechanical flowmetry (to measure PEFm).

Results

A total of 314 subjects participated, with an average age of 24.3 ± 16.4 years; 59% were Women. The main determinants for the reference equations were age, weight, height and sex at birth. The agreement of the PEFm, PEFs and PIFs values was inconsistent with that reported by other authors, even at the same barometric pressure. The association between PEFm and PEFs was r = 0.91 (p < 0.001), and the correlation coefficient of concordance was 0.84.

Conclusions

The PEFm, PEFs, and PIFs measurements in individuals living at moderate altitudes are different from those found by other authors in cities with different barometric pressures and ethnicities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01943-x.

Relationship between Peak Inspiratory Flow and Patient and Disease Characteristics in Individuals with COPD—A Systematic Scoping Review

Optimal delivery of medication via dry powder inhalers, the most commonly prescribed inhaler type, is dependent on a patient achieving a minimum level of inspiratory flow during inhalation. However, measurement of peak inspiratory flow (PIF) against the simulated resistance of a dry powder inhaler is not frequently performed in clinical practice due to time or equipment limitations. Therefore, defining which patient characteristics are associated with lower PIF is critically important to help clinicians optimize their inhaler choice through a more personalized approach to prescribing. The objective of this scoping review was to systematically evaluate patient and disease characteristics determining PIF in patients with chronic obstructive pulmonary disease (COPD). Medline, Cochrane and Embase databases were systematically searched for relevant studies on PIF in patients with COPD published in English between January 2000 and May 2021. The quality of evidence was assessed using a modified Grading of Recommendations Assessment, Development and Evaluation checklist. Of 3382 citations retrieved, 35 publications were included in the review (nine scored as high quality, 13 as moderate, nine as low, and four as very low). Factors correlating with PIF in >70% of papers included both patient characteristics (lower PIF correlated with increased age, female gender, shorter height, decreased handgrip and inspiratory muscle strength, and certain comorbidities) and disease characteristics (lower PIF correlated with markers of lung hyperinflation, lower peak expiratory flow [PEF] and increased disease severity). Other factors correlating with adequate/optimal or improved PIF included education/counseling and exercise/inspiratory muscle training; impaired physical function and errors in inhalation technique/non-adherence were associated with low/suboptimal PIF. In conclusion, clinicians should measure PIF against the simulated resistance of a particular device wherever possible. However, as this often cannot be done due to lack of resources or time, the patient and disease characteristics that influence PIF, as identified in this review, can help clinicians to choose the most appropriate inhaler type for their patients.

Measuring Peak Inspiratory Flow in Patients with Chronic Obstructive Pulmonary Disease

Dry powder inhalers (DPIs) are breath actuated, and patients using DPIs need to generate an optimal inspiratory flow during the inhalation maneuver for effective drug delivery to the lungs. However, practical and standardized recommendations for measuring peak inspiratory flow (PIF)—a potential indicator for effective DPI use in chronic obstructive pulmonary disease (COPD)—are lacking. To evaluate recommended PIF assessment approaches, we reviewed the Instructions for Use of the In-Check™ DIAL and the prescribing information for eight DPIs approved for use in the treatment of COPD in the United States. To evaluate applied PIF assessment approaches, we conducted a PubMed search from inception to August 31, 2021, for reports of clinical and real-life studies where PIF was measured using the In-Check™ DIAL or through a DPI in patients with COPD. Evaluation of collective sources, including 47 applicable studies, showed that instructions related to the positioning of the patient with their DPI, instructions for exhalation before the inhalation maneuver, the inhalation maneuver itself, and post-inhalation breath-hold times varied, and in many instances, appeared vague and/or incomplete. We observed considerable variation in how PIF was measured in clinical and real-life studies, underscoring the need for a standardized method of PIF measurement. Standardization of technique will facilitate comparisons among studies. Based on these findings and our clinical and research experience, we propose specific recommendations for PIF measurement to standardize the process and better ensure accurate and reliable PIF values in clinical trials and in daily clinical practice.

Impact of PIF, Inhalation Technique and Medication Adherence on Health Status and Exacerbations in COPD: Protocol of a Real-World Observational Study (PIFotal COPD Study)

INTRODUCTION

Dry powder inhalers (DPIs), a commonly prescribed inhaler type for respiratory diseases, require patients to generate sufficient peak inspiratory flow (PIF) to ensure optimal drug delivery to the airways. Effectiveness of therapy also requires a good inhalation technique and adequate medication adherence. For patients with chronic obstructive pulmonary disease (COPD), recent studies conducted in tertiary care suggest that DPI users with suboptimal PIF have poorer COPD-related health status and increased exacerbation risk versus those with optimal PIF. The PIFotal study will investigate the impact of PIF, inhalation technique and medication adherence on patient-reported outcomes in patients with COPD in primary care using a DPI for their maintenance therapy.

METHODS AND ANALYSIS

This cross-sectional observational study will assess 1200 patients (aged ≥ 40 years, diagnosed with COPD and using a DPI for COPD maintenance therapy for ≥ 3 months) from the Netherlands, Spain, Portugal, Poland, Greece and Australia. Assessments will consist of (1) PIF measurements (usual patient inhalation manoeuvre, maximal PIF against resistance of own inhaler, and maximal PIF against low resistance); (2) Clinical COPD Questionnaire (CCQ), COPD Assessment Test and Test of Adherence to Inhalers scores; and (3) video recordings of patient inhalation technique. Dependent variables include health status (CCQ score), number of self-reported exacerbations in previous 12 months, and healthcare resource utilisation in previous 6 months. Independent variables include PIF values, inhalation technique errors, medication adherence, and demographic and clinical characteristics. In the primary analysis, the mean difference in CCQ score between patients (1) with optimal/suboptimal PIF, (2) exhibiting/not exhibiting inhalation technique errors, and (3) adhering/not adhering to medication will be examined in a multivariable linear mixed model.

ETHICS

The study protocol was approved by ethics committees/institutional review boards of all participating sites prior to enrolment; written informed consent was obtained from all study participants.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT04532853.

TRONARTO: A Randomized, Placebo-Controlled Study of Tiotropium/Olodaterol Delivered via Soft Mist Inhaler in COPD Patients Stratified by Peak Inspiratory Flow

Background

Inhaled bronchodilator therapy is currently the mainstay of treatment for patients with chronic obstructive pulmonary disease (COPD). Some inhalers require patients to achieve certain inhalation efforts either to activate the device or to deliver medication to the site of action. For dry powder inhalers, low peak inspiratory flow (PIF) can result in poor medication delivery but the clinical significance of this is not well understood.

Methods

TRONARTO was a 4-week, randomized, double-blind, placebo-controlled, multicenter, parallel-group study which stratified patients with moderate-to-severe COPD according to their PIF against medium-low resistance at screening. Patients were randomized to receive tiotropium/olodaterol (5 μg/5 μg) or matched placebo delivered via the Respimat^® Soft Mist™ inhaler (SMI). After 4 weeks of treatment, we assessed change from baseline in forced expiratory volume in 1 second (FEV₁) area under the curve 0–3 hours (FEV₁ AUC_0–3h) and trough FEV₁.

Results

Overall, 213 patients were randomized, of whom 106 received tiotropium/olodaterol (PIF <60 L/min, 55; PIF ≥60 L/min, 51) and 107 received placebo (PIF <60 L/min, 55; PIF ≥60 L/min, 52). For FEV₁ AUC_0–3h, the adjusted mean change from baseline versus placebo was 336 mL (95% confidence interval [CI] 246–425 mL; P<0.0001) in the PIF <60 L/min group and 321 mL (95% CI 233–409 mL; P<0.0001) in the PIF ≥60 L/min group. For trough FEV₁, the adjusted mean change from baseline versus placebo was 201 mL (95% CI 117–286 mL; P<0.0001) in the PIF <60 L/min group and 217 mL (95% CI 135–299 mL; P<0.0001) in the PIF ≥60 L/min group.

Conclusion

In the TRONARTO study, which included patients with moderate-to-severe COPD and varying inspiratory flow abilities, treatment with tiotropium/olodaterol resulted in significant lung function improvements versus placebo. This SMI can be used irrespective of the PIF that a patient can generate.

Modeling of Inhalation Profiles Through Dry Powder Inhaler in Healthy Adults and Asthma Patients As a Prerequisite for Further In Vitro and In Silico Studies

Background: The severity of airway obstruction may affect patient's ability to perform an effective drug inhalation from a dry powder inhaler (DPI). Also, an incorrect inhalation technique may negatively affect the efficacy of asthma treatment. The aims of the study were (1) to analyze and compare inhalation profiles recorded with the use of different inhalation techniques, and thus, (2) to establish model inhalation profiles representative for healthy subjects and subjects with mild and moderate-to-severe asthma. Methods: This study was performed in healthy volunteers, patients with mild and moderate-to-severe asthma. A modified flow-volume test to define two different expiratory levels (to residual volume and half-way to residual volume) was performed. Inspiratory flow parameters were extracted: peak inspiratory flow rate (PIF_inh), time at which peak inspiratory flow rate occurs (tPIF_inh), total inhalation time (T), and inhaled volume (V). Test of frequency for tPIF_inh100% and tPIF_inh50% by asthma severity was performed, to provide information about initial flow accelerations. The impact of two different expiratory levels preceding inhalation (with severity of asthma as a categorical factor) on inspiratory flow parameters was examined. Results: PIF_inh was dependent upon asthma severity (p = 0.046). Type of exhalation before inhalation had no effect on PIF_inh values. V value was significantly affected both by asthma severity (p = 0.024) and type of exhalation before inhalation (p < 0.0001). Mean T value was influenced by type of exhalation before inhalation (p = 0.0003), but not by asthma severity. Mean tPIF_inh value was affected by the type of exhalation before inhalation only in healthy subjects (p = 0.01). Conclusions: Both asthma severity and type of exhalation before inhalation have little impact on the dynamics of inhalation through a DPI. An alternative form of equation describing inhalation profiles demonstrating a relationship between lung mechanics and dynamics of inspiratory profile has been proposed.

Inhalation Profiles Through a Dry Powder Inhaler: Relation Between Inhalation Technique and Spirometric Measures

Background: The understanding of the real flow profiles through a dry powder inhaler (DPI), generated by asthma patients, is a prerequisite for satisfactory drug delivery to the lungs. The aims of the study were to assess the relationship between spirometric measures and inhalation profiles through a low-resistance DPI, and to compare parameters of those profiles between optimal and suboptimal inhalation technique type. Methods: Both healthy adult volunteers and patients with asthma were included in the study. Spirometry was conducted along with modified flow-volume test to detect expiratory levels (maximum "100%" exhalation to residual volume [RV] and halfway "50%" to RV). These were the reference levels of the depth of exhalation for each patient to simulate the effect of incomplete exhalation. Individual inhalation profiles were recorded using spirometry in-house software as the volumetric airflow through the inhaler versus time. Inspiratory flow parameters were extracted: time to peak inspiratory flow through inhaler (PIF_inh), time at which peak inspiratory flow occurs (tPIF_inh), total inhalation time (T), and inhaled volume during maneuver (V). Results and Conclusions: There are significant relationships between spirometric indices and parameters of inhalation through a low-resistance, cyclohaler-type DPI (assessed by single-factor analysis of Spearman's rank correlation coefficient). Multiple regression models were constructed, predicting inspiratory flow parameters (including spirometric indices, demographic parameters, and inhaler's usage history as determinants). The exhalation halfway to RV before inhalation did not affect significantly PIF_inh and tPIF_inh (and, thus, initial flow dynamics) in asthma patients. T and V parameters were then significantly decreased, but seemed sufficient for successful DPI performance. Both exhalation to RV and incomplete exhalation halfway to RV preceding inhalation allow for effective usage of low-resistance DPI.

Peak Inspiratory Flow as a Predictive Therapeutic Biomarker in COPD

Biomarkers in COPD may be clinical (prior exacerbation history), physiologic (FEV₁), or blood based (eosinophil count or fibrinogen level). Recent interest in using biomarkers to predict response to therapy in clinical practice has emerged. The benefits of inhaled therapy depend on the correct use of the inhaler, including an appropriate inspiratory flow. Of the available delivery systems, dry powder inhalers are unique because they have an internal resistance, are breath actuated, and are flow dependent. Ideally, the user inhales "forcefully" to generate turbulent energy (determined by an individual's inspiratory flow and the resistance of the device) within the device that disaggregates the powder so that the individual inhales the medication particles into the lower respiratory tract. Because of specific features of dry powder inhalers and the required optimal inspiratory flow, an unmet need exists to identify individuals who are likely or unlikely to benefit from dry powder medications. Peak inspiratory flow, defined as the maximum airflow generated during inhalation against the simulated resistance of a dry powder inhaler, is a physiologic measure that has biological plausibility, has good test characteristics (repeatability and reliability), and is generalizable. Current evidence supports peak inspiratory flow as a predictive therapeutic biomarker to optimize therapy in both outpatients with COPD as well as those hospitalized for an exacerbation before discharge. This approach is consistent with the precepts of precision medicine, which considers differences in a person's biological features, exposure, and lifestyle to prevent and treat disease.

Peak Inspiratory Flows: Defining Repeatability Limits and a Predictive Equation for Different Inhalers

BACKGROUND

Peak inspiratory flow (PIF) has been proposed as a measure to assess a patient's ability to use dry powder inhalers (DPIs). However, robust quality criteria to determine a repeatability limit for measuring PIF are lacking.

RESEARCH QUESTIONS

What are the repeatability limits for measuring PIF? What is the relationship between PIF measured using the In-Check DIAL device at Diskus (GlaxoSmithKline; PIF_D) and HandiHaler (Boehringer Ingelheim; PIF_HH) resistances?

STUDY DESIGN AND METHODS

Data from a randomized, controlled, phase 3 trial (study 0149; see Clinical Trial Registration data) were used to define repeatability limits for PIF. In addition, a model to characterize the relationship between PIF measured with the In-Check DIAL device at PIF_D and PIF_HH was defined using data from two randomized, controlled, phase 3 trials (studies 0128 and 0149).

RESULTS

In study 0128, the mean values (SD) for PIF at zero resistance and PIF_HH were 84.6 (33.4) and 57.3 (26.1) L/min, respectively. In study 0149, the mean values (SD) for PIF_D and PIF_HH were 42.4 (11.2) and 29.0 (8.3) L/min, respectively. At the mean level, the mean difference between measurement attempts for PIF_D and PIF_HH was small, < 5 and < 3 L/min, respectively. The repeatability limit was determined as 10 and 5 L/min for PIF_D and PIF_HH, respectively. Modeling the relationship between PIF_D and PIF_HH, after controlling for significant covariates, demonstrated that a PIF_D value of 60 L/min was approximately equivalent to PIF_HH of 40 L/min.

INTERPRETATIONS

This analysis demonstrated that the two highest values of PIF using the In-Check DIAL device among three inspiratory efforts, met the repeatability limit. Altogether, these data provide guidance for measuring PIF against the simulated resistance of a specific DPI in clinical practice and research studies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; Nos.: NCT02518139 (study 0128) and NCT03095456 (study 0149); URL: www.clinicaltrials.gov.