Tidal Expiratory Flow Limitation at Rest as a Functional Marker of Pulmonary Emphysema in Moderate-to-Severe COPD

Figures & data

Figure 1.  Comparison of most relevant functional parameters between COPD patients without (NFL; n = 27) and with (FL; n = 13) resting tidal expiratory flow limitation in sitting position. Only FEV₁ is significantly lower in FL patients (* = p < 0.05).

Table 1.  Anthropometric and functional parameters of all patients studied and of the two groups of patients divided according to the presence of expiratory flow limitation in sitting position

Parameters	All	NFL	FL	p
n	40	27	13	−
Age (yr)	68 ± 9	69 ± 9	67 ± 8	ns
Male/Female	33/7	24/3	9/4	−
BMI (Kg/m^2)	26 ± 4	25 ± 5	27 ± 2	ns
Smoking habit (N/E/S)	3/30/7	1/22/4	2/8/3	−
VC (% predicted)	87 ± 20	85 ± 23	90 ± 13	ns
IC (% predicted)	74 ± 14	75 ± 17	73 ± 8	ns
FEV1 (% predicted)	44 ± 11	47 ± 11	36 ± 8	< 0.05
FEV1/FVC%	44 ± 7	46 ± 7	40 ± 6	< 0.05
MEF25–75% (% predicted)	15 ± 5	16 ± 5	12 ± 4	< 0.01
TLC (% predicted)	100 ± 14	101 ± 14	98 ± 14	ns
FRC (% predicted)	116 ± 22	118 ± 20	111 ± 25	ns
RV (% predicted)	123 ± 29	126 ± 28	118 ± 31	ns
DLCO (% predicted)	51 ± 18	51 ± 20	51 ± 16	ns
KCO (% predicted)	55 ± 21	56 ± 22	53 ± 21	ns

NFL = Not Flow Limited, FL = Flow Limited, = sitting position, BMI = Body Mass Index, N = non smoker; E = ex smoker; S = smoker, VC = Vital Capacity, IC = Inspiratory Capacity, FEV₁ = Forced Expiratory Volume in the first second, FVC = Forced Vital Capacity, MEF_25–75% = Maximum Expiratory flow between 25% and 75% of Vital Capacity, TLC = Total Lung Capacity, FRC = Functional residual Capacity, RV = Residual Volume, DL_CO = Diffusing capacity of the lung for carbon monoxide, K_CO = Transfer Coefficient of the lung for carbon monoxide.

Table 2.  Functional parameters and dyspnea score of the two groups of patients divided according to the presence of expiratory flow limitation in supine position

Parameters	NFL	FL	p
n	13	27
MRC	1.3 ± 1	2.5 ± 1.2	< 0.01
VC (% predicted)	86 ± 28	87 ± 16	ns
IC (% predicted)	77 ± 17	72 ± 13	ns
FEV1 (% predicted)	51 ± 9	40 ± 10	< 0.01
FEV1/FVC%	47 ± 8	42 ± 7	ns
MEF25–75% (% predicted)	15 ± 5	13 ± 4	< 0.01
TLC (% predicted)	102 ± 14	100 ± 15	ns
FRC (% predicted)	118 ± 22	115 ± 22	ns
RV (% predicted)	121 ± 27	124 ± 30	ns
DLCO (% predicted)	61 ± 16	46 ± 18	< 0.05
KCO (% predicted)	66 ± 19	49 ± 20	< 0.05

NFL = Not Flow Limited, FL = Flow Limited, = supine position, MRC = Medical Research Council Dyspnea Score, BMI = Body Mass Index, VC = Vital Capacity, IC = Inspiratory Capacity, FEV₁ = Forced Expiratory Volume in the first second, FVC = Forced Vital Capacity, MEF_25–75% = Maximum Expiratory flow between 25% and 75% of Vital Capacity, TLC = Total Lung Capacity, FRC = Functional residual Capacity, RV = Residual Volume, DL_CO = Diffusing capacity of the lung for carbon monoxide, K_CO = Transfer Coefficient of the lung for carbon monoxide.

Figure 2.  Comparison of most relevant functional parameters in COPD patients who are NFL in sitting position (n = 27) between those without (NFL; n = 13) and with (FL; n = 14) tidal expiratory flow limitation in supine position. Both DL_CO and K_CO are significantly lower in supine FL patients (* = p < 0.05), while FEV₁ is not.

Table 3.  Functional parameters and dyspnea score of the two groups of patients divided according to the presence of expiratory flow limitation only in supine position

Parameters	NFL, NFL	NFL, FL	p
n	13	14
MRC	1.3 ± 1	2.5 ± 1.2	< 0.01
VC (% predicted)	86 ± 28	85 ± 19	ns
IC (% predicted)	77 ± 17	72 ± 16	ns
FEV1 (% predicted)	51 ± 9	43 ± 11	ns
FEV1/FVC%	47 ± 8	44 ± 7	ns
MEF25–75% (% predicted)	15 ± 5	14 ± 4	< 0.05
TLC (% predicted)	102 ± 14	101 ± 15	ns
FRC (% predicted)	118 ± 22	118 ± 19	ns
RV (% predicted)	121 ± 27	130 ± 28	ns
DLCO (% predicted)	61 ± 16	42 ± 19	< 0.05
KCO (% predicted)	66 ± 19	46 ± 20	< 0.05

NFL = Not Flow Limited, FL = Flow Limited, = supine position, MRC = Medical Research Council Dyspnea Score, BMI = Body Mass Index, VC = Vital Capacity, IC = Inspiratory Capacity, FEV₁ = Forced Expiratory Volume in the first second, FVC = Forced Vital Capacity, MEF_25–75% = Maximum Expiratory flow between 25% and 75% of Vital Capacity, TLC = Total Lung Capacity, FRC = Functional residual Capacity, RV = Residual Volume, DL_CO = Diffusing capacity of the lung for carbon monoxide, K_CO = Transfer Coefficient of the lung for carbon monoxide.