Correlation of Luminal Mucus Score in Large Airways with Lung Function and Quality of Life in Severe Acute Exacerbation of COPD: A Cross-Sectional Study

Figures & data

Figure 1 Flowchart of participant inclusion in the study.

Abbreviations: AECOPD, acute exacerbation of chronic obstructive pulmonary disease; LFT, lung function test.

Figure 2 Bronchoscopic findings at the bronchial entrances of the right middle and lower lobe showing the luminal mucus scoring. (A) Score 0, normal; (B) score 1, strands of clear mucus; (C) score 2, globules of mucus; (D) score 3, airway occluded.

Table 1 Comparison Between Included and Excluded Patients

Characteristics	Included Patients (n=74)	Excluded Patients (n=16)	Test Statistic	P-value
Demographic factor
Age (year)	68.2±6.3	67.8±5.6	−0.278	0.782
Sex: male (%)	73(98.7%)	15(93.8%)	0.073	0.787
BMI (kg/m^2)	19.2(17.5–21.9)	19.7(18.1–23.7)	−1.113	0.266
Smoking status
Never-smoker	1(1.3%)	2(12.5%)	2.204	0.138
Former smoker	37(50.0%)	11(68.8%)	1.858	0.173
Current smoker ^a	36(48.6%)	3(18.7%)	3.649	0.056
Amount of smoking
Pack-years	56.8±30.1	48.7±26.3	0.946	0.347
Bronchoscopic findings
Luminal mucus score	15.0(12.0–21.0)	12.0(8.5–20.0)	−1.386	0.166
Quality of life
CAT score	13.7±8.1	14.1±9.7	−0.171	0.864
mMRC grade	2.0(1.0–2.0)	2.0(1.0–3.0)	−1.124	0.261
EXACT score	15.9±8.7	17.5±8.5	−0.737	0.463
SGRQ score	49.8(38.4–63.0)	56.4(32.4–72.0)	−1.040	0.299
Complete blood count test
White blood cell (10^9/L)	7.6(6.4–9.7)	8.3(6.6–10.3)	−0.776	0.438
Neutrophil (10^9/L)	5.1(4.1–7.0)	5.9(4.5–8.3)	−0.934	0.350
Lymphocyte (10^9/L)	1.5(1.2–1.8)	1.4(1.0–1.7)	−0.787	0.431
Eosinophil (10^9/L)	0.2(0.1–0.3)	0.2(0.0–0.3)	−0.706	0.480
Red blood cell (10^12/L)	4.7(4.4–5.0)	4.5(4.4–4.7)	−1.219	0.223
Hemoglobin (g/L)	144.0(135.0–152.0)	141.5(131.3–149.8)	−0.417	0.677
Arterial blood gas test
PaCO2 (mmHg)	40.5±7.0	42.1±11.1	−0.680	0.551
Lactic acid (mmol/L)	1.3(1.1–1.7)	1.2(0.9–1.6)	−0.889	0.374
Other laboratory findings
C-reactive protein (mg/L)	2.2(1.3–10.9)	4.5(1.8–41.8)	−1.314	0.189
Albumin (g/L)	37.6±3.9	37.2±3.4	0.414	0.680
Creatinine (umol/L)	70.3(60.0–80.2)	70.7(62.3–89.1)	−0.575	0.565
Blood urea nitrogen (mmol/L)	5.7(4.4–7.3)	5.3(4.1–7.4)	−0.566	0.571
Fbrinogen (g/L)	3.6(3.1–4.6)	3.9(2.9–5.2)	−0.359	0.720
Other clinical parameters
Hospital stay (day)	5.0(5.0–7.0)	6.0(4.3–7.8)	−0.757	0.449
ICU admission	1(1.3%)	1(6.2%)	0.073	0.787
NPPV	5(6.8%)	2(12.5%)	0.069	0.792

Notes: ^aCurrent smoking was defined as having smoked 100 cigarettes in one’s lifetime and smoking for the 6 months before the screening. Results are expressed as mean ± SD or median (IQR 25–75) as appropriate.

Abbreviations: BMI, body mass index; CAT, Chronic Obstructive Pulmonary Disease Assessment Test; mMRC, modified Medical Research Council dyspnea scale; EXACT, EXAcerbations of Chronic Pulmonary Disease Tool; SGRQ, St George’s Respiratory Questionnaire; PaCO2, partial pressure of carbon dioxide in artery; ICU, intensive care unit; NPPV, noninvasive positive pressure ventilation.

Table 2 Postbronchodilator Lung Function of 74 COPD Patients

Spirometric Parameters	n=74
FVC (L)	2.24±0.56
FVC % predicted	68.9±16.4
FEV1 (L)	0.96(0.73–1.36)
FEV1% predicted	39.6(29.8–52.4)
FEV1≥80% predicted, n(%)	2(2.7%)
50%≤FEV1<80% predicted, n(%)	21(28.4%)
30%≤FEV1<50% predicted, n(%)	33(44.6%)
FEV1<30% predicted, n(%)	18(24.3%)
FEV1/FVC (%)	44.5(40.7–51.8)
PEF (L/sec)	2.52(1.80–3.38)
FEF25%-75% (L/sec)	0.42(0.30–0.62)

Note: Results are expressed as mean ± SD or median (IQR 25–75) as appropriate.

Abbreviations: PEF, peak expiratory flow; FEF_25%–75%, forced expiratory flow at 25% to 75% of the FVC.

Table 3 Relationship Between Total Luminal Mucus Score and Other Parameters

Characteristics	ρ	P-value
Age	0.069	0.559
BMI (kg/m^2)	−0.269	0.020^a
Amount of smoking (pack-years)	0.198	0.091
Chronic bronchitis (yes)	0.300	0.009^a
CAT score	0.313	0.007^a
mMRC grade	0.527	<0.001^a
EXACT score	0.426	<0.001^a
SGRQ score	0.441	<0.001^a
Neutrophil (10^9/L)	0.154	0.189
Lymphocyte (10^9/L)	−0.210	0.072
Eosinophil (10^9/L)	0.081	0.492
PaCO2(mmHg)	0.273	0.018^a
C-reactive protein (mg/L)	0.132	0.215
Fbrinogen (g/L)	0.059	0.619
FVC (L)	−0.437	<0.001^a
FVC % predicted	−0.460	<0.001^a
FEV1 (L)	−0.502	<0.001^a
FEV1% predicted	−0.498	<0.001^a
FEV1/FVC (%)	−0.446	<0.001^a
PEF (L/sec)	−0.455	<0.001^a
FEF25%-75% (L/sec)	−0.518	<0.001^a
Hospital stay (day)	0.257	0.027^a

Note: ^aStatistical significance.

Abbreviations: BMI, body mass index; CAT, Chronic Obstructive Pulmonary Disease Assessment Test; mMRC, modified Medical Research Council dyspnea scale; EXACT, EXAcerbations of Chronic Pulmonary Disease Tool; SGRQ, St George’s Respiratory Questionnaire; PaCO2, partial pressure of carbon dioxide in artery; PEF, peak expiratory flow; FEF_25%–75%, forced expiratory flow at 25% to 75% of the FVC.

Figure 3 Correlation of total luminal mucus score with mMRC grade, SGRQ score, FEF_25%–75%, and FEV₁% predicted. Note: Total luminal mucus score is significantly correlated with mMRC grade (A), SGRQ score (B), FEF_25%-75% (C), and FEV₁ % predicted (D).

Abbreviations: mMRC, modified Medical Research Council dyspnea scale; SGRQ, St George’s Respiratory Questionnaire; PaCO2, FEF_25%–75%, forced expiratory flow at 25% to 75% of the FVC.

Table 4 Relationship of Luminal Mucus Score in Various Lobes with FEV₁% Predicted and mMRC Grade

Lobes	FEV1% Predicted		mMRC Grade
	ρ	P-value	ρ	P-value
RULB	−0.225	0.054	0.369	0.001^c
RMLB	−0.308	0.008^c	0.373	0.001^c
RLLB	−0.169	0.150	0.176	0.134
LUDB	−0.459	<0.001^c	0.375	0.001^c
Lingular bronchus	−0.319	0.006^c	0.364	0.001^c
LLLB	−0.254	0.029^c	0.251	0.031^c
Bilateral ULB ^a	−0.422	<0.001^c	0.456	<0.001^c
RMLB and lingular bronchus	−0.340	0.003^c	0.433	<0.001^c
Bilateral LLB ^b	−0.245	0.036^c	0.259	0.026^c

Notes: ^aBilateral ULB, including RULB and LUDB; ^bbilateral LLB, including RLLB and LLLB; ^cstatistical significance.

Abbreviations: RULB, right upper lobe bronchus; RMLB, right middle lobe bronchus; RLLB, right lower lobe bronchus; LUDB, left upper division bronchus; LLLB, lower lobe bronchus; ULB, upper lobe bronchi; LLB, lower lobe bronchi; mMRC, modified Medical Research Council dyspnea scale.

Table 5 Stepwise Multiple Linear Regression Analysis for Luminal Mucus Score^a

Variables	Coefficient (95% CI)	Standardized β	t-value	P-value	VIF
Intercept	16.724 (11.105 to 22.344)		5.934	<0.001
mMRC	2.465 (1.065 to 3.866)	0.398	3.511	0.001^b	1.379
FEV1% predicted	−0.108 (−0.197 to −0.019)	−0.273	−2.410	0.019^b	1.379

Notes: ^aR²=0.348; F=18.960; P<0.001; ^bstatistical significance; variables: BMI, CAT score, mMRC grade, EXACT score, SGRQ score, PaCO2, FVC, FVC % predicted, FEV₁, FEV₁% predicted, FEV₁/FVC, PEF and FEF_25%–75%.

Abbreviations: β, regression coefficient; mMRC, modified Medical Research Council dyspnea scale; VIF, variance inflation factor.