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Background: Dry powder inhaler (DPI) use requires sufficient peak inspiratory flow over the DPI internal resistance (PIFR)., Objectives: We examined whether spirometric peak inspiratory flow (PIFspiro) could serve to predict PIFR in patients with obstructive lung disease., Method: Thirty healthy nonsmokers and 140 stable outpatients (70 COPD, 70 asthma) performed spirometry according to the 2019 ERS/ATS spirometry update, yielding PIFspiro. Using a PIFR measurement device with varying orifices, all subjects' PIFR values were recorded for 5 predefined resistance levels, characterized by 5 orifice cross sections (SR). A test group including all healthy subjects, 30 of the asthma, and 30 of the COPD patients was used to establish the relationship between PIFR and both PIFspiro and SR by multiple regression. A validation group including the remaining 40 asthma and 40 COPD patients, served to verify whether their predicted PIFR value corresponded to the measured PIFR for each resistance level., Results: The asthma (FEV1 = 78 ± 17 [SD] %pred) and COPD (FEV1 = 46 ± 17 [SD] %pred) patients under study had varying airway obstruction. In the test group, PIFR could be predicted by ln[PIFspiro] (p < 0.0001), SR (p < 0.0001), and SR2 (p = 0.006), with an adjusted R2 = 0.71. In the validation group, estimated PIFR did not significantly differ from measured PIFR (p > 0.05 for the 5 resistance levels)., Conclusions: We propose a simple method to predict PIFR for a range of common DPI resistances, based on the device characteristics and on the patient's characteristics reflected in PIFspiro. As such, routine spirometry can serve to estimate a patient's specific PIFR without the need for additional testing., (© 2022 S. Karger AG, Basel.)

Background: While peak in- and expiratory flow rates offer valuable information for diagnosis and monitoring in respiratory disease, these indices are usually considered too variable to be routinely used for quantification in clinical practice., Objectives: The aim of the study was to obtain reproducible measurements of maximal inspiratory flow rates and to construct reference equations for peak in- and expiratory flows (PIF and PEF)., Method: With coaching for maximal effort, 187 healthy Caucasian subjects (20-80 years) performed at least 3 combined forced inspiratory and expiratory manoeuvres, until at least 2 peak inspiratory flow measurements were within 10% of each other. The effect on PIF preceded by a slow expiration instead of a forced expiration and PIF repeatability over 3 different days was also investigated in subgroups. Reference values and limits of normal for PIF, mid-inspiratory flow, and PEF were obtained according to the Lambda-Mu-Sigma statistical method., Results: A valid PIF could be obtained within 3.3 ± 0.6(SD) attempts, resulting in an overall within-test PIF variability of 4.6 ± 3.2(SD)%. A slow instead of a forced expiration prior to forced inspiration resulted in a significant (p < 0.001) but small PIF increase (2.5% on average). Intraclass correlation coefficient for between-day PIF was 0.981 (95% CI: 0.960-0.992). Over the entire age range, inter-subject PIF variability was smaller than in previous reports, and PIF could be predicted based on its determinants gender, age, and height (r2 = 0.53)., Conclusions: When adhering to similar criteria for the measurement of effort-dependent portions of inspiratory and expiratory flow-volume curves, performed according to current ATS/ERS standards, it is possible to obtain reproducible PIF and PEF values for use in routine clinical practice., (© 2021 S. Karger AG, Basel.)

A 51-year-old active smoker with primary acquired pulmonary alveolar proteinosis (PAP) diagnosed by biopsy and anti-GM-CSF antibodies was treated safely with whole-lung lavage (WLL). This resulted in a rapid improvement of symptoms and arterial blood oxygenation, but not of standard lung function parameters. However, we also performed the multiple-breath nitrogen washout (MBW) test to determine the lung clearance index (LCI) as well as indices of acinar ventilation heterogeneity (S(acin)) and conductive ventilation heterogeneity (S(cond)). At baseline, a distinct abnormality was seen for S(acin) and LCI, while S(cond) was at the upper limit of normal for this subject. S(acin), in particular, was in excess of the S(acin) abnormality corresponding to a 20-pack-year smoking history. Immediately after WLL, S(acin) and S(cond) both fell to within a normal range while LCI also decreased but remained abnormal. The S(acin) decrease was much greater than the S(cond) decrease, which was to be expected after 1 week of smoking cessation at the hospital (smoking was resumed after release from hospital). A follow-up visit 7 weeks after WLL revealed a spectacular improvement on CT scan and improvements in standard lung function. Another follow-up visit 14 weeks after WLL showed further improvements in standard lung function, and both S(acin) and S(cond) remained well within the normal range, and LCI was above the upper limit of normal. We conclude that in this patient, removal of excess surfactant by WLL resulted in a restored ventilation distribution in most of the distal air spaces., (Copyright © 2012 S. Karger AG, Basel.)

A 67-year-old never-smoker was diagnosed with diffuse panbronchiolitis (DPB) and was started on 250 mg azithromycin twice weekly. Over a 16-month observation period, lung function was assessed monthly, including a dedicated small airways test, the multiple breath nitrogen washout (MBW) with indices S(cond) and S(acin) of ventilation heterogeneity at the level of the conductive and acinar air spaces, respectively. Baseline measurements indicated moderate airway obstruction, air trapping and considerable dysfunction of the small airways around the acinar entrance. Treatment resulted in excellent symptomatic improvement paralleled by marked improvements in FEV(1), FVC, RV/TLC, S(cond) and S(acin); by contrast, there were no consistent changes in FEF(75) or TL(CO). While improvements were such that S(cond) fell within normal limits after 5 months, S(acin) remained abnormal even after 16 months of treatment. This suggests a distinct acinar structural abnormality in DPB that cannot be reversed by azithromycin., (Copyright © 2012 S. Karger AG, Basel.)