Repetitive Saliva Swallowing Test Predicts COPD Exacerbation

Figures & data

Table 1 Patient Characteristics

	Total N = 70	E Group N = 28	Non-E Group N = 42	p value
Age (years old)	72.8 ± 7.5	73.9 ± 8.0	72.1 ± 7.2	0.34
Male/Female	59/11	22/6	37/5	0.33
BMI (kg/m^2)	21.7 ± 3.9	20.8 ± 4.4	22.3 ± 3.4	0.11
GOLD Stage
I	15 (21.4)	4 (14.3)	11 (26.2)	0.24
II	25 (35.7)	7 (25.0)	18 (42.9)
III	21 (30.0)	11 (39.3)	10 (23.8)
IV	9 (12.9)	6 (21.4)	3 (7.1)
History of exacerbations in the past year	27 (38.6)	16 (57.1)	11 (26.2)	0.01

Note: Data in parentheses are percentages.

Abbreviations: E group, exacerbation group; Non-E group, non-exacerbation group.

Table 2 The Comparison of the Dysphagia Screening Results Between the Two Groups

Test	Criteria	E Group N = 28	Non-E Group N = 42	p value
EAT-10	≥ 3	18 (64.3)	19 (45.2)	0.15
FSSG	≥ 8	10 (35.7)	11 (26.2)	0.43
RSST	A) ≤ 1 time/30 seconds	3 (10.7)	0 (0)	0.06
	B) ≤ 2 times/30 seconds	9 (32.1)	3 (7.1)	<0.01
	C) ≤ 3 times/30 seconds	15 (53.6)	8 (19.1)	<0.01
	D) ≤ 4 times/30 seconds	21 (75.0)	16 (38.1)	<0.01
	E) ≤ 5 times/30 seconds	27 (96.4)	24 (57.1)	<0.01
	F) ≤ 6 times/30 seconds	28 (100.0)	37 (88.1)	0.08
	G) ≤ 7 times/30 seconds	28 (100.0)	41 (97.6)	1.0
	H) ≤ 8 times/30 seconds	28 (100.0)	41 (97.6)	1.0
WST	A) Vocal change	13 (46.4)	13 (31.0)	0.22
	B) Pattern* 2–5	22 (78.6))	29 (69.1)	0.42
SSPT	A) Using 0.4 mL of water	4 (14.3)	7 (16.7)	1.0
	B) Using 2.0 mL of water	4 (14.3)	3 (7.1)	0.43

Notes: *Drinking patterns are defined as follows: 1, drinks 30 mL in 1 swallow without choking; 2, drinks 30 mL in multiple swallows without choking; 3, drinks 30 mL in one swallow with some choking; 4, drinks 30 mL in multiple swallows with some choking; 5, chokes and has difficulty drinking 30 mL. Data in parentheses are percentages.

Abbreviations: E group, exacerbation group; Non-E group, non-exacerbation group; FSSG, frequency scale for the symptoms of gastroesophageal reflux disease; RSST, repetitive saliva swallowing test; WST, water swallowing test; SSPT, simple swallowing provocation test.

Figure 1 Results of an ROC curve analysis using the swallow frequency in RSST. When the RSST cut-off value was set at 5.0, the sensitivity and specificity were 0.429 and 0.964, respectively, and the area under the ROC curve was 0.775.

Figure 2 Kaplan-Meier curves of the time to first exacerbation (any severity) (A) stratified by the presence of exacerbation in the past year and (B) stratified by the RSST cut-off value of 5. The time to first exacerbation was significantly longer in patients with a history of exacerbation in the past year than in those with no such history (A) and in those with an RSST value of >5 (B). The RSST was a stronger predictor of exacerbation than a history of exacerbation.

Figure 3 Kaplan-Meier curves of the time to first moderate or severe exacerbation (A) stratified by the presence of exacerbation in the past year and (B) stratified by the RSST cut-off value of 5. The time to first moderate or severe exacerbation was significantly longer in patients with a history of exacerbation in the past year than in those with no such history (A) and in those with an RSST value of >5 (B). The RSST was a stronger predictor of exacerbation than a history of exacerbation. This difference was more pronounced when the time to first moderate or severe exacerbation was set as an event.

Table 3 The Relationship Between a History of Exacerbation in the Past Year and the Results of the RSST Using a Cut-Off Value of 5

		History of Exacerbation in the Past Year
		Yes	No
RSST	> 5	2	17
	≤ 5	25	26

Abbreviations: RSST, Repetitive Saliva Swallowing Test.

Figure 4 Correlation between the %FEV1 and the number of swallows in the RSST. No significant relationship was detected between the %FEV1 and the number of swallows in the RSST.