Peak inspiratory flow

Some controversy exists concerning the most cost-effective delivery system (MDI plus holding chamber versus nebulization) to be used in treating severe acute asthma in the emergency department and hospital (see below). The DPIs are currently not indicated for the treatment of severe acute asthma exacerbations. Patients with more severe obstruction may not be able to generate sufficient peak inspiratory flows for adequate delivery. ... 

Figure 7 Peak inspiratory flow rate versus device resistance for patient-driven dry-powder inhalers illustrating comfortable and maximum effort curves for healthy volunteers. (From Ref. 34.) The United States Pharmacopiea specifies that DPIs should be tested at a device pressure drop of 4 kPa.

Stahl E, Ribeiro L, Sandahl G. Dose response to inhaled terhutahne powder and peak inspiratory flow through Turbuhaler in children with mild to moderate asthma. Pediatr Puhnonol 1996 22 106-110. 

Brown P, Ning A, Greening A, McLean A, Crompton G. Peak inspiratory flow through Turbuhaler in acute asthma. Eur Respir J 1995 8 1940-1941. 

Dal Negro R, Pomari C, Micheletto C, Cantini L. Peak inspiratory flow rate as measured through a new powder inhaler, does not correlate with asthma severity or influence effect of inhaled salbutamol. Adv Ther 1997 14 181-191. 

Meijer R, van der Mark T, Aalders B, Postma D, Koeter G. Home assessment of peak inspiratory flow through the Turbuhaler in asthmatic patients. Thorax 1996 51 433 34. 

The volume of air per unit time through an inhaler during inspiration is the inspiratory flow rate, which is expressed in L/min. Generally, the flow rate through an inhaler quite rapidly reaches a maximum value (peak inspiratory flow, PIF) followed by a slower decrease to zero flow. As a general rule, the average flow rate equals approximately 70 % of PIF. From the average flow rate and the total inhalation time the inhaled volume (V) can be computed. The flow rate influences the particle size distribution in the aerosol and the deposition pattern in the respiratory tract. 

Fig. 2 Functional endpoints of ventilatory patterns in animals. F, frequency (respiratory rate) Vt, tidal volume T, inspiratory time Te, expiratory time PIF, peak inspiratory flow PEF, peak expiratory flow...

Typically, respiratory system SP assessments of SMs are performed using either head-out or whole-body plethysmography. Parameters such as respiratory rate (RR) and tidal volume (TV) are measured, and many other parameters such as minute volume, peak inspiratory flow (PIF), peak expiratory flow (PEF), enhanced pause (Penh), inspiration time (IT), and expiration time (ET) are derived. Although there are many methods for respiratory function assessment in rodents (Murphy 2002, 2014 Hoffman et al. 2007 Hoymann 2012), such methods have not been validated extensively for large animals such as NHPs. Therefore, respiratory... 

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