George's Respiratory Questionnaire; FVC: forced vital capacity; [FEV.sub.1]: forced expiratory volume in one second; [FEF.sub.25-75%]: forced expiratory flow during the middle half of the FVC; TLC: total lung capacity
; RV: residual volume; [SIII.sub.N2]: phase III slope of nitrogen single-breath washout; CV/VC: closing volume/vital capacity; peak V[O.sub.2]: peak oxygen uptake; RER max: maximum respiratory exchange ratio (VC[O.sub.2]/V[O.sub.2]) at peak exercise; [O.sub.2] pulse max: maximum oxygen pulse (V[O.sub.2]/heart rate) at peak exercise; HRR: heart rate reserve.
In order to detect the presence of air trapping in the lungs, lung volumes should be measured to determine the total lung capacity
and the residual volume.
Finally, increased dead space to tidal volume ratio (VD/VT), increased shunt, and high residual volume to total lung capacity
ratio (RV/TLC) or distribution of ventilation all have a negative effect on the respiratory drive.
The following indices of PFT, namely, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV[sub]1), FEV[sub]1/FVC, total lung capacity
(TLC), and the diffusion capacity for carbon monoxide of lung (DLCO), were assessed and expressed as percentages of values predicted.
Thirty-eight patients (79.2%) had preserved FEV1/FVC ratio with mean FEV1 of 63 [+ or -] 20% with mild restriction (total lung capacity
(TLC) 63 [+ or -] 17%).
Parameters included in the test were forced expiratory volume in one second ([FEV.sub.1]), forced vital capacity (FVC), [FEV.sub.1]/FVC ratio, peak expiratory flow rate, residual volume, total lung capacity
, transfer factor of the lung for carbon monoxide (DLCO) and DLCO divided by alveolar volume.
Pulmonary function tests showed a mild restrictive pattern (forced vital capacity (FVC) = 3.39 l--102% of predicted value; forced expiratory volume in 1 s (FEVi) = 2.64--109%; FEV/FVC = 78%; peak expiratory flow rate (PEFR) = 1036 l/s--147%, total lung capacity
(TLC) = 4.94 l--75%; residual volume (RV) = 1.49 l--52%; expiratory reserve volume (ERV) = 1.78 l--217%) and diffusion capacity for C[O.sub.2] corrected for total lung capacity
by single breath (diffusing capacity for C[O.sub.2] divided by the alveolar volume - D[L.sub.CO/VA]) was severely impaired (57% of predicted value), suggesting a pattern of interstitial disease.
However, there is consistent evidence that smokers who have emphysema and fibrosis can be extremely dyspneic and may present with normal flow rates on spirometry, normal total lung capacity
, and strikingly low diffusion capacity.
Despite severe gas exchange impairment, which required oxygen-therapy, pulmonary function tests revealed mild restrictive abnormalities (forced vital capacity (FVC)--72% of predicted normal value (pred.), forced expiratory volume in 1 s ([FEV.sub.1])--70% pred., forced expiratory volume in 1 s / vital capacity ([FEV.sub.1]/ VC)--0.77, total lung capacity
type, and the added requirement of total lung capacity
. As explained
Asbestosis also decreases total lung capacity
(the maximum volume lungs can be expanded).
20% decline in DLCO of the predicted value, or the value lower than 80% of the predicted one and reduces the total lung capacity
(TLC) for more than 15% are the diagnostic criteria of APT.