Forced Expiration

Mean airway pressure as an index of mean alveolar pressure.

“…It follows therefore that any decreases of the level of expiratory Pao below the highest pressure that sustains flow limitation (Pao.crit) will decrease Pao without changing Falv (11,17). Under these conditions, Pao will be expected to underestimate Palv, in line with the predictions of Marini and Ravenscraft (1,2).…”

“…By definition, when expiratory flow is limited by dynamic airway compression, the pressures downstream from the site of flow limitation (that includes Pao) are isolated from those upstream (that includes Palv) (17). It follows therefore that any decreases of the level of expiratory Pao below the highest pressure that sustains flow limitation (Pao.crit) will decrease Pao without changing Falv (11,17).…”

Reference ranges for shape indices of the flow‐volume loop of healthy children

“…MEFVL shape variability may be related to disproportional growth between the airway and the lung (dysanapsis) quantified by the ratio of FEF 50 by vital capacity (VC) times static recoil pressure at 50% of VC (FEF 50 /VC*Pstat) to VC . The convex MEFVL shape in younger children is compatible with the lower elastic recoil observed in these children . The FEF 25–75 /FVC ratio was proposed as a surrogate of Mead‘s measure and used to define the MEFVL decay contour of healthy preschoolers, a convex decay (i.e., FEF 25–75 /FVC ≥1.00) with mean values (SD) of 1.73 (0.17) was reported for children <4 years decreasing to 1.48 (0.17) in 5 to 6‐year‐old children.…”

“…We propose the FEF 50 /PEF flow ratio and the angle β to distinguish convexity from concavity of MEFVL. Hyatt had already underlined that a ratio of two FEF could give an estimate of the MEFVL shape. He also proposed to use more than one slope to discriminate normal from abnormal curves.…”

Unfolding the mechanisms of progression of pulmonary emphysema in COPD

“…As a matter of fact, FEV1 being a distillate of the physical properties of the lung as well of the airways [18], it would not be surprising that, notwithstanding the clear relationship with upper lobe emphysema, airway remodelling also contributes to worsening the classical spirometric parameters over time. As recently reported by MCDONOUGH et al [19], gradual narrowing and disappearance of small airways over time is the most typical feature of COPD that precedes the appearance of emphysema and continues afterwards.…”