Closing Capacity and Gas Exchange in Chronic Heart Failure: Experimental Protocol

Within 1 month prior to entering our study, Weber class was determined by cardiopulmonary exercise testing: Weber class B, 7 patients; Weber class C, 10 patients; and Weber class D, 3 patients. Heart failure was defined as symptomatic left ventricular dysfunction, with a left ejection fraction of < 0.45 documented by bidimensional echocardiography. Patients were excluded if they had primary pulmonary, neurologic, or myopathic disease. The echocardiographic ejection fraction and systolic pulmonary artery pressure (sPAP) were measured within the 2 weeks preceding entry into our study. The mean ejection fraction was 23% (range, 9 to 34%) [Table 1]. Twenty healthy subjects (control subjects) who were matched for sex and age were also studied with the same protocol as for the CHF patients. All control subjects were nonsmokers, but nine patients were ex-smokers (Table 1). The study was approved by the local ethics committee, and informed consent was obtained from each subject. add comment
Chronic dyspnea was scored using the modified Medical Research Council (MRC) scale based on six increasing grades (0 to 5). Dyspnea at rest was measured by a modified Borg scale, ranking magnitude from 0 (none) to 10 (maximal).
Each patient underwent a spirometric, plethysmographic, and pulmonary diffusion (ie, diffusing capacity of the lung for carbon monoxide [Dlco]) study in the sitting position. Using a plethys-mograph (Autobox 2800; SensorMedics; Yorba Linda, CA), airway resistance (Raw) was measured at a panting frequency of < 1 Hz. Spirometric and plethysmographic volumes were assessed according to European Respiratory Society (ERS). Dlco was measured with a water-sealed spirometer (Biomedin; Padua, Italy) using helium for the measurement of alveolar volume (VA). Predicted values of Raw were from Peslin, and those for Dlco were from the ERS. With the patient in the sitting position, arterial Po2 and Pco2 were measured (ABL 735; Radiometer; Copenhagen, Denmark).

Table 1—Anthropometric Characteristics and Baseline Respiratory Data in a Seated Position in CHF Patients and Control Group

Variables CHF Patients (n = 20) Control Subjects (n = 20) p Value
Sex, No.
Male 18 18
Female 2 2
Age, yr 59 ± 11 59 ± 11 NS
BMI, kg/m2 26 ± 3 23 ± 8 NS
Smoking status
Nonsmokers 11 11
Ex-smokers 9 9
Ejection fraction, % 23 ± 8
sPAP, mm Hg 46 ± 18
FVC, % predicted 82 ± 18 103 ± 11 < 0.001
VC, % predicted 80 ± 17 103 ± 12 < 0.001
FEVj, % predicted 82 ± 19 105 ± 11 < 0.001
FEVj/FVC ratio, % predicted 102 ± 7 105 ± 7 NS
FEF75, % predicted 51 ± 24 78 ± 23 < 0.001
TLC, % predicted 81 ± 15 97 ± 7 < 0.001
FRC, % predicted 78 ± 12 93 ± 13 < 0.001
IC, % predicted 84 ± 20 103 ± 13 < 0.001
ERV, % predicted 56 ± 23 103 ± 13 < 0.001
RV, % predicted 88 ± 17 93 ± 11 NS
RV/TLC ratio, % predicted 109 ± 17 96 ± 12 NS
Dlco, % predicted 69 ± 21 94 ± 11 < 0.001
Dlco/VA ratio, % predicted 90 ± 23 103 ± 18 NS
Raw, % predicted 116 ± 46 105 ± 36 NS
sGaw, % predicted 100 ± 37 96 ± 23 NS
MRC score 2.2 ± 1 0
Borg score 0.5 ± 0.7 0
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