Closing Capacity and Gas Exchange in Chronic Heart Failure: Results

Table 1 provides the anthropometric characteristics and baseline respiratory data for control subjects and CHF patients. In the control subjects, all baseline respiratory data were within normal limits; the MRC and Borg scores were zero, while the CHF patients exhibited slightly higher levels of MRC and Borg dyspnea scores.
In CHF patients, the FEV1/FVC ratio was within normal limits, while TLC and its subdivisions were reduced. This is also shown in Figure 1, where, for comparative purposes, volumes are expressed as the percentage of the predicted TLC. There were no significant differences in lung function between nonsmokers and ex-smokers in both CHF patients and control subjects, except for RV (percent predicted), which in control subjects was significantly (p < 0.05) lower in nonsmokers than in ex-smokers (Table 2). further

The increased Raw and decreased Dlco levels in CHF patients were probably due mainly to the reduced functional residual capacity (FRC) because the specific airway conductance (sGaw) and Dlco/VA ratio values were in the normal range. None of the CHF patients or control subjects exhibited tidal FL.
The AN2 and CV/VC ratio were increased in CHF patients relative to control subjects (Table 3). The increase in the CV/VC ratio was due entirely to decreased VC because there was no significant difference in CV between CHF patients and control subjects.

Also, no significant difference was found in CC, expressed both in liters and percent predicted. In fact, the CC was, on average, actually lower in CHF patients than in control subjects, although not significantly. This is also seen in Figure 1, which also shows that in CHF patients the CC was, on average, higher than FRC (CC was greater than FRC in 13 of the 20 CHF patients). In contrast, in all 20 control subjects CC was lower than FRC. In both CHF patients and control subjects, the CC percent predicted did not differ significantly between nonsmokers and ex-smokers (Table 2).

Figure-1

Figure 1. Lung volumes expressed as a percentage of the predicted TLC. Left, A: control subjects. Right, B: observed values in CHF patients. Values are given as mean ± SD (bars).

Table 2—Respiratory Data of All CHF Patients and Control Subjects, Stratified in Nonsmokers and Ex-smokers

Variables CHF Patients Control Subjects
IEx-Smokers (n = 9) Nonsmokers (n = 11) IEx-Smokers (n = 9) Nonsmokers (n = 11)
TLC, % predicted 83 ± 16 80 ± 15 94 ± 5 100 ± 8
FRC, % predicted 80 ± 13 75 ± 12 94 ± 10 92 ± 15
RV, % predicted 89 ± 17 86 ± 18 98 ± 8 87 ± 11t
FEV1, % predicted 84 ± 20 80 ± 20 98 ± 9 111 ± 9
FEV1/FVC, % predicted 102 ± 7 101 ± 7 107 ± 7 102 ± 8
FEF75, % predicted 47 ± 18 53 ± 30 76 ± 26 80 ± 21
CC, % predicted 95 ± 16 94 ± 23 102 ± 8 98 ± 12
P(A-a)O2, kPa 4.1 ± 1.5 4.5 ± 1.0 2.9 ± 0.6 2.6 ± 0.5

Table 3—AN2, CV, and CC in CHF Patients and Control Subjects

Variables CHF Patients(n = 20) Control Subjects (n = 20) p Value
E>N

2

%n2/l 3.8 + 2.7 1.8 + 1.3 < 0.005
%predicted 270 ± 151 121 ± 48 < 0.001
CV
L 0.71 ± 0.25 0.72 ± 0.16 NS
% predicted 83 ± 24 89 ± 22 NS
CV/VC ratio
% 24 ± 5 19 ± 5 < 0.002
% predicted 115 ± 28 89 ± 29 < 0.002
CC
L 2.70 ± 0.71 2.83 ± 0.39 NS
% predicted 94 ± 20 100 ± 10 NS
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