Effect of an external resistance to airflow on the inspiratory flow curve

Koning, J P de; Mark, T W van der; J, Coenegracht P M; Tromp, T.F.J.; Frijlink, Henderik W.

doi:10.1016/s0378-5173(01)00969-3

Cited by 48 publications

(39 citation statements)

References 10 publications

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“…Most commercially available asthma inhalers have a resistance between those of the 4-and 7-mm resistors, including the Turbuhaler (AstraZeneca, Sweden), Diskhaler (Glaxo Welcome, UK), and Diskus (GlaxoSmithKline, UK) (20) (Fig. 5).…”

Section: Inhaler Resistance Effect On Inspiration Of Cf Patientsmentioning

confidence: 99%

Effect of Dry Powder Inhaler Resistance on the Inspiratory Flow Rates and Volumes of Cystic Fibrosis Patients of Six Years and Older

Tiddens

Geller

Challoner

et al. 2006

Journal of Aerosol Medicine

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Several inhaled drugs for use by cystic fibrosis (CF) patients are formulated for nebulizer use only. This therapy is time consuming and includes the risk of contamination of the nebulizers. Dry powder inhalers (DPI) can be an attractive alternative for CF drugs. Inhaled flow rate and volume, and the device resistance are important determinants for optimal dispersion of drug from a DPI. It is important to understand how these variables interact in the CF population in order to properly design a new DPI formulation targeted for these patients. The objective of this study was to assess the inspiratory variables of a representative population of CF subjects 6 years and older with varying degrees of lung disease while inhaling through resistances that simulate DPI devices. Ninety-six stable CF patients were enrolled, ages 6-54 years, FEV(1) 19-126% predicted. Subjects inhaled forcefully through four different resistances (0.019, 0.024, 0.038, and 0.048 kP(0.5)/LPM, respectively), while inspiratory time (IT(DPI)), peak inspiratory flow (PIF(DPI)), and volumes (V(DPI)) were measured. For any resistance, inspired V(DPI) increased with the older age groups; PIF(DPI) was similar between adults and adolescents but lower in the children. Subjects with lower FEV(1) had lower V(DPI) and PIF(DPI). As resistance increased, PIF(DPI) decreased, IT(DPI) increased, with no significant change in V(DPI). At the lowest resistance mean PIF(DPI) was 105 LPM (range 45-163) for all patients; 112 LPM (range 75-163) in adults; and 89 LPM (45-126) in children. Mean inspired V(DPI) was 1.75 L for all patients; 2.2 L (0.8-3.7) in adults; and 1.2 L (0.5-1.8) in children. At the lowest resistance a minimal flow rate of 30, 45, and 60 LPM was attained in 100%, 99%, and 96% of all patients. Volumes of 1.0, 1.5, and 2.0 L were attained by 85%, 57%, and 30% of the patients. At the highest resistance mean PIF(DPI) was 52 LPM (range 26-70) for all patients; 55 LPM (40-70) in adults; and 47 LPM (26-62) in children. Mean inspired V(DPI) was 1.5 L in all patients; 1.9 L (0.9-3.5) in adults and 1.1 L (0.5-2.3) in children. At the highest resistance, a minimal flow rate of 30, 45, and 60 LPM was attained in 99%, 80%, and 22% of all patients. Volumes of 1, 1.5, and 2 L were attained in 84%, 45%, and 23% of the patients. We defined ranges for inspiratory variables in a diverse CF population for a range of device resistances that bracket those of current DPIs. The recorded inspiratory patterns can be used on the bench to design and test new dry powder formulations and devices to target the largest proportion of the CF population.

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Section: Inhaler Resistance Effect On Inspiration Of Cf Patientsmentioning

confidence: 99%

Effect of Dry Powder Inhaler Resistance on the Inspiratory Flow Rates and Volumes of Cystic Fibrosis Patients of Six Years and Older

Tiddens

Geller

Challoner

et al. 2006

Journal of Aerosol Medicine

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“…(10) Added inspiratory resistance generally decreases PIF rate for both breathing maneuvers performed at rest and during exercise. (1,(22)(23)(24) Under heavy external work conditions of 181, 226, and 271 W, Silverman et al (25) reported average PIF rates of 194, 254, and 286 L · min −1 without any applied breathing resistance. However, with added resistances (4.5 cm H 2 O · L −1 · sec inspiratory and 2.9 cm H 2 O · L −1 · sec expiratory resistance) average PIF rates were 160, 192, and 240 L · min −1 , indicating that PIF decreases between 16 and 24% for resistances representative of air-purifying respirators.…”

Section: Respirator Inhalation Resistancementioning

confidence: 99%

Performance when Breathing Through Different Respirator Inhalation and Exhalation Resistances During Hard Work

Caretti

Coyne

Johnson

et al. 2006

Journal of Occupational and Environmental Hygiene

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Respirator inspiratory and expiratory breathing resistances impact ventilation and performance when studied independently. However, it is less clear as to how various combinations of inhalation and exhalation resistance affect user performance. The present study investigated the performance of 11 individuals during constant load, demanding work to exhaustion while wearing respirators with eight different combinations of inhalation and exhalation resistance. Exercise performance time, performance rating, minute volume, and peak inspiratory and expiratory airflow were recorded at the end of each test trial, and independent correlations with inhalation resistance and exhalation resistance were assessed. The combined impacts of respirator inhalation and exhalation resistances were quantified as the total external work of breathing (WOB(tot)) and correlations between the test variables and WOB(tot) were also examined. Significantly linear decreases in performance were found with increased inhalation resistances independent of exhalation resistance (R(2) = 0.99; p < 0.001) and with increased WOB(tot) (R(2) = 0.92; p < 0.001). Performance also decreased with increased exhalation resistance but no significant relationships were found. Minute volume decreased linearly with increased inhalation resistance independent of exhalation resistance (R(2) = 0.99; p < 0.001), but the linear decrease observed between minute volume and WOB(tot) was weak (R(2) = 0.36; p < 0.05). These findings suggest that WOB(tot) serves as a reliable estimate of the combined impacts of respirator inhalation and exhalation resistances on user performance during hard work, but that inhalation resistance alone serves as a better predictor of ventilation during respirator wear.

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“…Previous studies on effects of inhalation maneuver on DPI performance were focused on measuring particle size at the inhaler outlet using realistic inhalation profiles (Bisgaard et al, 1998;Clark & Bailey, 1996;De Boer et al, 1997;De Koning, Van der Mark, Coenegracht, Tromp, & Frijlink, 2002;Finlay & Gehmlich, 2000;Kamin et al, 2002). Based on these data, it is acknowledged that valid DPI testing should take into consideration realistic inhalation profiles, as opposed to standardized cascade impactor tests, where a fixed flow rate is used.…”

Section: Introductionmentioning

confidence: 99%

The effect of unsteady flow rate increase on in vitro mouth–throat deposition of inhaled boluses

Grgic

Martin

Finlay

2006

Journal of Aerosol Science

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Effect of an external resistance to airflow on the inspiratory flow curve

Cited by 48 publications

References 10 publications

Effect of Dry Powder Inhaler Resistance on the Inspiratory Flow Rates and Volumes of Cystic Fibrosis Patients of Six Years and Older

Effect of Dry Powder Inhaler Resistance on the Inspiratory Flow Rates and Volumes of Cystic Fibrosis Patients of Six Years and Older

Performance when Breathing Through Different Respirator Inhalation and Exhalation Resistances During Hard Work

The effect of unsteady flow rate increase on in vitro mouth–throat deposition of inhaled boluses

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