Day-to-Day Variability of Parameters Recorded by Home Noninvasive Positive Pressure Ventilation for Detection of Severe Acute Exacerbations in COPD

Figures & data

Table 1 Baseline Characteristics of Study Participants

	Total (n=102)	AECOPD (n=31)	Stable COPD (n=71)	P value
Age, years	70.80±6.86	71.74±6.55	70.39±7.00	0.682
Male	82(80.3%)	24(80.6%)	58(81.7%)	0.190
BMI, kg/m^2	21.93±4.39	22.17±3.92	21.82±4.60	0.714
Former smokers	83(81.4%)	22(71.0%)	61(85.9%)	0.098
Comorbidity
Hypertension	51(50.0%)	16(51.6%)	35(49.3%)	0.830
Diabetes	16(15.7%)	2(6.5%)	14(19.7%)	0.138
Coronary heart disease	21(20.6%)	4(12.9%)	17(23.9%)	0.289
Sleep apnea syndrome,	4(3.9%)	2(6.5%)	2(2.8%)	0.583
Number of AECOPD within the last years	1.00(1.00–2.00)	1.00 (1.00–3.00)	1.00(1.00–2.00)	0.298
FEV1, L	0.64±0.29	0.57±0.17	0.67±0.33	0.142
FEV1, % predicted	25.87±9.18	24.74±7.97	26.36±9.67	0.423
FEV1/FVC, %	46.79±9.92	46.68±10.49	46.83±9.75	0.947
PaO2, mmHg	80.03±30.74	81.03±28.78	79.59±31.75	0.830
PaCO2, mmHg	66.80±12.12	68.64±12.89	66.00±11.78	0.314
HCO3, mmolL	37.86±6.10	36.77±6.90	38.34±5.70	0.236
pH	7.37±0.06	7.35±0.07	7.38±0.05	0.112
mMRC score	3.00(2.50–4.00)	3.00(3.00–4.00)	3.00(2.00–4.00)	0.511
IPAP, cmH2O	16.00(15.00–18.00)	16.00(14.00–17.75)	16.00(15.00–17.75)	0.545
EPAP, cmH2O	5.00(4.00–5.00)	5.00(4.00–5.00)	5.00(4.00–5.00)	0.668
Back-up rate,/min	14.00(12.00–15.00)	12.00(12.00–15.00)	14.00(12.00–15.25)	0.807
The baseline of NPPV-related parameters
Respiratory rate, breath/min	18.75±2.28	18.66±2.55	18.79±2.16	0.798
Daily use, min/day	429.73±119.26	425.44±90.04	431.60±130.51	0.811
Leaks, L/min	37.54±12.19	37.38±8.76	37.61±13.47	0.932
Tidal volume, mL	592.68±136.14	581.63±140.23	597.50±135.04	0.590

Note: Data reported as mean or median with SD or interquartile range where appropriate.

Abbreviations: BMI, body mass index; mMRC, modified Medical Research Council; IPAP, inspiratory positive airway pressure; EPAP, expiratory positive airway pressure; NPPV, noninvasive positive pressure ventilation.

Figure 1 The study flow chart.

Table 2 Timing of Changes in Variability of NPPV-Related Parameter in the Days Before AECOPD (Demonstrated for 7-Day Analysis Windows)

Parameter	Days ^#	AECOPD (n=31)			Stable COPD (n=71)
		Difference (95% CI)^¶	Adjusted p-value*		Difference (95% CI)^¶	Adjusted p-value*
Respiratory rate, breath/min	−3	2.702 (0.895 to 4.508)	<0.001		−0.130 (−0.346 to 0.086)	0.234
	−2	3.386 (1.536 to 5.234)	<0.001		−0.177 (−0.393 to 0.037)	0.103
	−1	4.224 (2.362 to 6.086)	<0.001		−0.203 (−0.431 to 0.024)	0.080
Daily use, min/day	−3	25.510 (−56.216 to 107.237)	0.528		−2.304 (−18.381 to 13.772)	0.775
	−2	20.394 (−74.758 to 115.547)	0.664		3.782 (−12.217 to 19.783)	0.638
	−1	−1.005 (−96.335 to 94.324)	0.982		3.771 (−12.011 to 19.554)	0.470
Leaks, L/min	−3	1.669 (−2.529 to 5.869)	0.423		−0.848 (−2.109 to 0.412)	0.184
	−2	2.521 (−1.516 to 6.560)	0.087		−0.560 (−1.752 to 0.630)	0.350
	−1	2.695 (−1.462 to 6.854)	0.195		−0.775 (−1.900 to 0.350)	0.174
Tidal volume, mL	−3	12.520 (−31.189 to 56.229)	0.562		−11.974 (−25.943 to 1.994)	0.091
	−2	19.513 (−26.486 to 65.513)	0.393		−7.030 (−20.895 to 6.834)	0.315
	−1	21.900 (−27.695 to 71.497)	0.374		−7.675 (−22.206 to 6.855)	0.295

Notes: ^#Day prior to AECOPD admission; ^¶compare each day with the baseline in each group; *adjusted p-value from Dunnett’s post hoc test.

Table 3 Comparison of Parameter Recorded by NPPV Software in the Days Before AECOPD Between AECOPD Group and Stable Group (Demonstrated for 7-Day Analysis Windows)

Parameter	Day^#	AECOPD (n=31)	Stable COPD (n=71)	Difference (95% CI)*	P-value
Respiratory rate, breath/min	−3	21.36±3.18	18.66±2.18	2.705 (1.627 to 3.784)	<0.001
	−2	22.05±3.10	18.61±2.12	3.437 (2.386 to 4.488)	<0.001
	−1	22.89±3.01	18.58±2.09	4.301 (3.272 to 5.330)	<0.001
Daily use, min/day	−3	450.95±213.19	429.30±124.82	21.653 (−45.255 to 88.562)	0.522
	−2	445.83±240.97	435.38±124.83	10.449 (−61.436 to 82.336)	0.820
	−1	424.43±243.39	435.37±120.37	−10.938 (−82.296 to 60.419)	0.813
Leaks, L/min	−3	39.05±11.57	36.76±13.76	2.294 (−3.318 to 7.907)	0.419
	−2	39.90±11.38	37.05±13.95	2.858 (−2.793 to 8.511)	0.318
	−1	40.08±11.12	36.83±13.65	3.247 (−2.283 to 8.777)	0.246
Tidal volume, mL	−3	594.15±125.20	585.52±128.65	8.625 (−45.884 to 63.135)	0.752
	−2	601.14±132.94	590.47±128.11	10.675 (−44.670 to 66.020)	0.702
	−1	603.53±144.99	589.82±127.01	13.707 (−42.954 to 70.369)	0.632

Notes: ^#Day prior to AECOPD admission; *difference between AECOPD and Stable COPD group.

Figure 2 Timing of changes in variability of NPPV parameter before AECOPD. (A) Respiratory rate; (B) daily usage; (C) leaks; (D) tidal volume. Data reported as mean with SD.

Notes: *p-value from difference between each day with the baseline in each group <0.05. ^#p-value from difference between AECOPD and Stable COPD group <0.05.

Table 4 Univariate and Multivariate Logistic Regression Analysis of Changes in NPPV Parameters Associated with the Risk of Exacerbation

Variable	Crude OR* (95% CI)	p value	Adjusted OR^# (95% CI)	p value
7-day mean Respiratory rate	1.849(1.408 to 2.428)	<0.001	1.756(1.249 to 2.469)	0.001
Abnormal value of daily use within 7-day	1.706(1.320 to 2.206)	<0.001	1.918(1.253 to 2.934)	0.003
Abnormal value of leaks within 7-day	1.567(1.255 to 1.958)	<0.001	1.271(0.873 to 1.852)	0.210
Abnormal value of tidal volume within 7-day	2.165(1.607 to 2.915)	<0.001	2.081(1.380 to 3.140)	<0.001

Notes: *Univariate logistic regression analysis; #multivariate logistic regression analysis.

Table 5 Receiver Operating Characteristic Analysis of NPPV Parameters to Predict AECOPD

Variable	AUC (95% CI)	P-value	Cutoff value	Sensitivity	Specificity
7-day mean Respiratory rate	0.833(0.749 to 0.917)	<0.001	19.5	0.935	0.648
Abnormal value of daily use within 7-day	0.773(0.683 to 0.683)	<0.001	2.5	0.806	0.606
Abnormal value of leaks within 7-day	0.746(0.636 to 0.855)	<0.001	4.5	0.612	0.817
Abnormal value of tidal volume within 7-day	0.857(0.774 to 0.941)	<0.001	3.5	0.838	0.761

Abbreviation: AUC, area under the curve.

Figure 3 Nomogram for AECOPD risk and its predictive performance. (A) Nomogram to estimate the risk of AECOPD based on NPPV-related parameters. (B) Internal validity of the predictive performance of the nomogram in using the bootstrap validation method.

Figure 4 Receiver operating characteristic curves for predicting the risk of AECOPD.