Simultaneous quasi-static lung pressure-volume curves and "closing volume" measurements.

In 9 patients complaining primarily of exertional dyspnea, the diagnosis of early emphysema was made on the basis of a decrease of the elastic recoil of the lung and of the single breath diffusing capacity, in the presence of only minor airway obstruction as estimated from the routine pulmonary function tests. Closing volume, the alveolar plateau, dynamic compliance and maximal flow at 50 % of the vital capacity were markedly abnormal; the maximal flow-static recoil pressure relationships suggest, however, that none of the patients suffered from small airway disease. We conclude that one should systematically consider early emphysema in the differential diagnosis of small airway disease

Section: Discussionmentioning

confidence: 99%

Emphysema with Minor Airway Obstruction and Abnormal Tests of Small Airway Disease

Demedts¹,

Cosemans²,

Roo³

et al. 1978

“…From the data of Sutherland et al [2] and Glaister et al [3] the onset of airway clo sure occurs between PL of 5 and 0 cm H20 , thus the negative values we obtained by the direct method represent perhaps eso phageal compression artifacts. Dernets et al [4] reported PL coincident with onset of CV of -0.07 ± 3.12 cm HLO whereas Ingram et al [5] reported positive PL values (1.3 ± 0.05 cm H20).…”

Section: Discussionmentioning

confidence: 97%

“…Ingram et al [5] reported very close cor-PL scale, cm H20 -6 0 6 12 18 24 30 t _ l __ I_I___1 _I___I_I___I_I___ I__I___I Fig. 1.…”

Section: Introductionmentioning

confidence: 85%

See 1 more Smart Citation

Measurement of Airways Closing Pressure in Man

Al-Bazzaz¹

1981

In 7 healthy males, lung static and quasi-static pressure-volume (QS-PV) curves were measured simultaneously with closing volume by the single breath N₂ washout test. Comparison was made of four methods for estimation of the closing pressure (CP) at the onset of phase IV. In the first method the transpulmonary pressure (PL) that directly coincided on the tracing with onset of phase IV was measured, results varied widely with a mean of -1.3 ± 2.2 cm H₂O (x ± SD). The second method was to identify on the QS-PV curve the point of transition in the shape of the curve from concavity to convexity. This method yielded a mean CP of 2.8 ± 1.7 cm H₂O, but did not correlate statistically with closing capacity (r = 0.07, p > 0.05). The third method was to treat the whole PV curve as an exponential curve, and mathematically extrapolate the curve to a volume corresponding to the onset of phase IV, and calculate PL at this point. This method yielded CP of 2.1 ± 0.76 cm H₂O. When the same method was applied to static PV curve, CP was 2.0 ± 0.7 cm H₂O. Conformity of CP values obtained using extrapolation methods to those expected from theoretical considerations and from in vitro measurements suggests that the extrapolation methods most likely yield the true PL at the onset of airway closure

“…The possible explanation for the increased CC and CV in association with relatively normal to slightly reduced elas tic recoil and also reduced closing pres sure is as follows: sarcoid granulomata, in volving small airways and narrowing the lumen, predispose the airways to prema ture closure. The slightly reduced elastic recoil could also predispose the small air ways to premature closure at a higher lung volume and lower closing pressure [32],…”

Section: Discussionmentioning

confidence: 99%

The Pathophysiology and Response to Steroid Therapy in Sarcoidosis

Ploysongsang¹,

Roberts²

1986

Fourteen patients with early sarcoidosis were prospectively studied over a period of 12–24 months. After baseline physiologic measurements they were treated with 40 mg of prednisone daily for 8 weeks and the measurements were repeated. Thereafter, the steroid dosage was reduced to 0–10 mg every other day and the measurements were repeated between the 12th and 24th month. Relatively normal lung volumes (VC, FRC, RV, TLC) and low D_LCO increased with 8-week intensive steroid treatment and fell to below the pretreatment levels when the steroid was either tapered or stopped. The V_max50-air, V_max50-He, FEF25–75, upstream conductance (Gus) increased during intensive treatment whereas the R_L fell and the FEV₁/FVC ratio did not change. The CC/TLC, CV/VC, ΔN2, CL_dyn/CL_st, ΔVmax₅₀ were abnormal in many patients and did not change after 8 weeks of steroid treatment. We concluded that the obstructive defect is common in early sarcoidosis, predominantly in small airways and patchy in nature; the functional derangement is always improved by intensive and adequate steroid therapy and worsened when the drug is tapered or stopped.