Lung Dysfunction of Chronic Smokers with No Signs of COPD

Figures & data

Table 1.  Subjects’ demographics.

	CS-mild	CS-heavy
Number of subjects	24	26
Gender (F/M)	11/13	3/23
Age (yrs)	48.9 (34–65)	56.3 (36 – 69)
Number of subjects at age
≥30 to ≤ 40 yrs	5	2
≥41 to ≤ 50 yrs	10	1
≥51 to ≤ 60 yrs	6	13
≥61 to ≤ 65 yrs	3	7
≥66 to ≤ 70 yrs	0	3
Pack-year history	16.3 (10–20)	32.0 (22–50)
Smokers (current/ex)	15/9	24/2
BMI (kg/m^2)	25.7 (20 – 33.2)	26.7 (20.8 – 34.9)

Results are presented as a mean and range in parenthesis.

BMI- body mass index.

Table 2.  Lung function parameters

	CS-mild	CS-heavy	P-value
FEV1 (L)	3.35 (±0.96)	3.29 (±0.83)	0.7
FEV1% predicted	101.57 (±14.90)	100.56 (±25.84)	0.3
FVC (L)	3.98 (±1.08)	4.12 (±0.96)	0.6
FVC% predicted	100.10 (±12.59)	96.94 (±13.16)	0.6
FEV1/FVC ratio	84.65 (±6.64)	79.92 (±6.07)	0.02
MEF 50 (L/s)	3.68 (±1.86)	3.48 (±1.48)	0.6
MEF 50% predicted	83.38 (±29.89)	75.41 (±25.87)	0.2
RV (L)	2.48 (±0.65)	3.03 (±0.61)	0.001
RV% predicted	126.50 (±33.60)	135 (±28.89)	0.1
FRC (L)	3.29 (±0.86)	3.89 (±1.08)	0.6
FRC% predicted	104.96 (±27.45)	113.15 (±31.48)	0.3
TLC (L)	6.65 (±1.17)	7.34 (±1.29)	0.2
TLC% predicted	107.33 (±13.90)	108.30 (±17.28)	0.8
RV/TLC ratio	37.57 (±8.05)	41.63 (±7.57)	0.03
Raw (kPa·l^−1·s)	0.23 (±0.11)	0.25 (±0.12)	0.6
sGaw (s^−1·kPa^−1)	1.39 (±0.51)	1.10 (±0.44)	0.03
IC (L)	3.35 (±0.95)	3.45 (± 0.62)	0.3
IC% predicted	115.54 (±25.84)	108.26 (±14.61)	0.2
DLCOSB% predicted	82.79 (±12.66)	78.92 (±13.09)	0.4

Results are presented as mean (±SD),

FEV₁ – forced expiratory volume in 1 second, FVC – forced vital capacity, MEF50 –maximal expiratory flow at 50% of FVC; RV-residual volume; FRC- functional residual capacity. TLC- total lung capacity, Raw- airway resistance; sGaw – airway specific conductance; DLCOSB- single-breath diffusing capacity for carbon monoxide.

Figure 1.  FEV₁% of predicted and FEV1/FVC ratio in CS-mild and CS-heavy. P< 0.05 compared to CS-mild.

Figure 2.  Airway resistance (Raw) and airway specific conductance (sGaw) values in CS-mild and CS-heavy. The median and ranges (boxes) are shown. P< 0.05 compared to CS-mild. Unit (U), the quality of y-axis is representing Raw (kPa·l⁻¹·s) and sGaw (s⁻¹·kPa⁻¹).

Figure 3.  Spearman's correlation between smoking history (pack-years) and airway specific conductance (sGaw). A significant negative correlation between smoking history (pack-years) and decline of airway conductance (p = 0.004, r = – 0.39).

Table 3.  Relationships between lung function values, smoking history and age in smokers

	Linear regression	Multiple Regression
Lung function value	Smoking (pack-years) Coefficient 95% CI	Smoking (pack-years) Coefficient 95% CI	Age (years) Coefficient 95% CI
FEV1 (L)	− 0.037 to 0.015	0.007 to 0.047^**	−0.105 to −0.062^**
FEV1 (% predicted)	−0.933 to 0.327	−0.788 to 0.641	−1.253 to 0.251
FVC (L)	−0.032 to 0.028	0.017 to 0.065^*	−0.119 to −0.069^**
FVC (% predicted)	−0.721 to 0.027	−0.655 to 0.197	−0.706 to 0.192
FEV1/FVC ratio	−0.424 to −0.042^*	−0.392 to 0.043	−0.357 to 0.101
MEF 50 (L/s)	−0.075 to 0.023	−0.017 to 0.075	−0.168 to −0.071^**
MEF50 (% of predicted)	−1.568 to 0.055	−0.969 to 0.7365	−2.29 to −0.495^**
RV (L)	0.011 to 0.047^**	0.0062 to 0.049 ^*	−0.019 to 0.025
RV (% of predicted)	−0.583 to 1.288	−0.699 to 1.461	−1.199 to 1.076
FRC (L)	−0.0033 to 0.0559	0.009 to 0.0747^*	−0.068 to 0.008
FRC (% of predicted)	−0.618 to 1.16	0.592 to 1.452	−1.423 to 0.730
TLC (L)	−0.0044 to 0.07	0.0405 to 0.109^**	−0.128 to −0.055^**
TLC (% of predicted)	−0.467 to 0.47	−0.475 to 0.608	−0.708 to 0.433
RV/TLC ratio	−0.003 to 0.460	−0.245 to 0.189	0.331 to 0.788^**
Raw (kPa·l^−1·s)	−0.0008 to 0.006	−0.003 to 0.004	0.0006 to 0.008^*
sGaw (s^−1·kPa^−1)	−0.035 to −0.007^**	−0.034 to −0.003^*	−0.021 to 0.01
DLCOSB (% of predicted)	−0.619 to 0.146	−0.776 to 0.1	−0.241 to 0.681

Linear and multiple regression analysis with independent variables of smoking history (pack-years) and chronic smokers’ age (years) were used. FEV₁ – forced expiratory volume in 1 second, FVC – forced vital capacity, MEF50 – maximal expiratory flow at 50% of FVC; RV-residual volume; FRC- functional residual capacity; TLC- total lung capacity, sGaw – airway specific conductance; Raw- airway resistance, DLCOSB- single-breath diffusing capacity for carbon monoxide; ^*P < 0.05, ^**P < 0.01, CI- confidence interval.

Table 4.  Characteristics of emphysematous lesions in chronic smokers

Group	Age(yrs)	Smoking pack-years	Smoking status Current/ex-smoker	DLCOSB % of predicted	% of emphysema on CT scans^*	Type of emphysema
CS-mild	39	15	ex-smoker	68	4.1	Mixed
CS-mild	51	11	ex-smoker	79	0.59	Centrilobular
CS-mild	44	15	ex-smoker	70	0.6	Centrilobular
CS-mild	50	15	current	69	1.05	Paraseptal
CS-mild	57	20	ex-smoker	104	0.56	Centrilobular
CS-mild	35	20	current	68	0.16	Centrilobular
CS-heavy	58	25	current	68	3.2	Mixed
CS-heavy	57	25	current	78	0.9	Paraseptal
CS-heavy	58	35	current	69	1	Centrilobular
CS-heavy	61	40	current	81	0.05	Paraseptal
CS-heavy	63	40	current	66	2.28	Mixed
CS-heavy	51	35	ex-smoker	88	2.5	Mixed
CS-heavy	55	35	current	51	6.5	Mixed
CS-heavy	54	40	current	57	6.2	Mixed
CS-heavy	57	30	current	66	5.2	Centrilobular
CS-heavy	52	37	current	67	6.6	Mixed
CS-heavy	32	23	current	71	0.9	Centrilobular

^*The threshold of -950 Hounsfield Units, DLCOSB-single-breath diffusing capacity for carbon monoxide.