Minute Ventilation During Spontaneous Breathing, High-Intensity Noninvasive Positive Pressure Ventilation and Intelligent Volume Assured Pressure Support in Hypercapnic COPD

Figures & data

Figure 1.  Measurement setup.

Table 1.  Demographic data and lung function parameters for all patients and the two subgroups

	Overall (n = 27)	Non-obese (n = 13)	Obese (n = 14)	p-value*
BMI (kg/m^2)	28.5 ± 7.6	21.8 ± 5.1	34.7 ± 2.4
Age (years)	65.6 ± 9.8	65.5 ± 11.3	65.7 ± 8.4	0.948
Height (m)	1.69 ± 0.08	1.64 ± 0.05	1.73 ± 0.07	0.001
Pack-years (n)	29.3 ± 20	33.1 ± 20	25.9 ± 20.1	0.358
FVC (% predicted)	55.2 ± 16.4	48.2 ± 12.3	61.7 ± 17.5	0.030
FEV1 (% predicted)	34.4 ± 15.1	27.2 ± 13.3	41.1 ± 13.8	0.003
FEV1/FVC (%)	47.5 ± 14.5	40.7 ± 15.8	53.7 ± 10.1	0.017
TLC (% predicted)	95.6 ± 30.7	114.1 ± 30.9	78.4 ± 18.4	0.001

Data are mean ± SD. BMI = body mass index, FEV₁ = forced expiratory volume in 1 second, FVC = forced vital capacity, Non-obese = BMI ≤ 30 kg/m², Obese = BMI > 30 kg/m², TLC = total lung capacity.

*Comparison between obese and non-obese patients made using the unpaired t-test.

Table 2.  Ventilator settings for HI-NPPV, duration of HI-NPPV prior to the study and blood gases during nocturnal HI-NPPV for all patients and the two subgroups

	Overall(n = 27)	Non-obese(n = 13)	Obese(n = 14)	p-value*
IPAP (mbar)	24.8 ± 4.1	24.1 ± 3.4	25.4 ± 4.8	0.434
EPAP (mbar)	4.9 ± 1.8	4.2 ± 0.8	5.6 ± 2.2	0.053
RR (/min)	17.7 ± 2.8	18.1 ± 2.9	17.3 ± 2.6	0.467
Inspiratory time (sec)	1.0 ± 0.1	1.0 ± 0.1	1.0 ± 0.1	0.126
Supplementary oxygen (L/min)	1.5 ± 1.2	1.8 ± 1.2	1.2 ± 1.1	0.160
HMV (months)	44.9 ± 49.4	32.7 ± 47	56.3 ± 50.5	0.126
PaO2 (mmHg)	71.4 ± 9.8	68 ± 7.1	74.6 ± 11	0.076
PaCO2 (mmHg)	43.8 ± 7.0	42.8 ± 5.3	44.8 ± 8.4	0.460
pH	7.42 ± 0.04	7.43 ± 0.05	7.41 ± 0.03	0.237
HCO3^− (mmmol/L)	27.9 ± 3.7	28.1 ± 3.1	27.7 ± 4.2	0.814

Data are mean ± SD. BMI = body mass index, EPAP = expiratory positive airway pressure, HCO₃⁻ = bicarbonate, HMV = home mechanical ventilation, IPAP = inspiratory positive airway pressure, Non-obese = BMI ≤ 30 kg/m², Obese = BMI > 30 kg/m², PaCO₂ = arterial partial pressure of carbon dioxide, PaO₂ = arterial partial pressure of oxygen, RR = respiratory rate.

*Comparison between obese and non-obese patients made using the unpaired t-test.

Table 3.  Blood gases and lung function parameters before and after initiation of HI-NPPV (n = 27)

	Before HI-NPPV	With HI-NPPV	Treatment effect (95% CI)	p-value
FVC (% predicted)	48.3 ± 10.7	55.2 ± 16.4	7.6 (0.9, 14.4)	0.027*
FEV1 (% predicted)	30.7 ± 12.9	34.4 ± 15.1	2.9 (−0.9, 6.8)	0.128*
FEV1 (L)	0.93 ± 0.40	1.02 ± 0.47	0.05 (−0.06, 0.16)	0.375*
FEV1/FVC (%)	46 (33−65)	50 (34−59)		0.23^#
TLC (% predicted)	85 (61−117)	95 (68−123)		0.52^#
RV (% predicted)	159 (93−241)	160 (102−258)		0.95^#
PaO2 (mmHg)	66.6 ± 14.4	71.4 ± 9.8	3.8 (−4.7, 12.2)	0.36*
PaCO1 (mmHg)	58.1 ± 8.9	43.8 ± 7.0	−14.1 (−16.9, −11.3)	<0.001*
pH	7.37 (7.35−7.38)	7.41 (7.40−7.44)		0.003^#
HCO3^− (mmmol/L)	32.1 ± 3.2	27.9 ± 3.7	−3.7 (−5.0, −2.4)	<0.001*

Data are mean ± SD or median (interquartile range). CI = confidence interval, FEV₁ = forced expiratory volume in one second, FVC = forced vital capacity, HCO₃⁻ = bicarbonate, HI-NPPV = high-intensity noninvasive positive pressure ventilation, PaCO₂ = arterial partial pressure of carbon dioxide, PaO₂ = arterial partial pressure of oxygen, RV = residual volume, TLC = total lung capacity.

*Comparison between before and after treatment values made using paired t-test.

^#Comparison between before and after treatment values made using Wilcoxon signed rank test.

Figure 2.  Pneumotachographic measurements comparing SB, HI-NPPV and iVAPS. Data are mean ± SD. HI-NPPV = high intensity non-invasive positive pressure ventilation, iVAPS = intelligent volume assured pressure support, SB = spontaneous breathing. Comparison between SB, HI-NPPV and iVAPS was made using a linear regression model for repeated measures.

Table 4.  Pneumotachographic measurements comparing SB (n = 27), HI-NPPV (n = 27) and iVAPS (n = 21) for all patients and for the two subgroups

	SB(n = 27)	HI-NPPV(n = 27)	iVAPS(n = 21)	Difference (95% CI) p-value*
				HI-NPPV vs SB	iVAPS vs SB	HI-NPPV vs iVAPS
MV (L/min)
Overall	9.5 ± 1.7	12.1 ± 2.8	11.7 ± 3.6	2.5 (1.5, 3.6) p < 0.001	1.8 (−0.7, 3.0) p = 0.003	0.7 (−0.5, 1.8) p = 0.25
Non-obese patients	9.2 ± 2.1	11.4 ± 3.0	9.5 ± 2.2	2.2 (0.7, 3.8) p = 0.005	0.3 (−1.4, 2.1) p = 0.71	1.9 (0.2, 3.7) p = 0.032
Obese patients	9.9 ± 1.3	12.7 ± 2.5	13.3 ± 3.7	2.8 (1.3, 4.3) p < 0.001	3.4 (1.8, 4.9) p < 0.001	−0.6 (−2.1, 1.0) p = 0.47
RR (/min)
Overall	17.3 ± 4.2	18.1 ± 2.5	16.3 ± 3.5	0.8 (−0.4, 2.0) p = 0.21	−0.5 (−1.8, 0.8) p = 0.46	1.3 (−0.1, 2.6) p = 0.064
Non-obese patients	18.1 ± 5.3	18.4 ± 2.5	15.9 ± 3.7	0.3 (−1.4, 2.1) p = 0.72	−1.4 (−3.4, 0.6) p = 0.17	1.7 (−0.3, 3.7) p = 0.096
Obese patients	16.5 ± 2.7	17.7 ± 2.5	16.6 ± 3.5	1.2 (−0.5, 2.9) p = 0.15	0.4 (−1.4, 2.2) p = 0.66	0.8 (−0.9, 2.6) p = 0.35
Leakage (%)
Overall	1.2 ± 1.0	21.2 ± 15.9	21.7 ± 11.9	20.1 (15.0, 25.2) p < 0.001	20.1 (14.6, 25.7) p < 0.001	−0.04 (−5.6, 5.5) p = 0.99
Non-obese patients	1.2 ± 1.1	22.5 ± 17.6	22.3 ± 13.7	21.3 (14.0, 28.6) p < 0.001	20.3 (12.0, 28.6) p < 0.001	1.0 (−7.2, 9.3) p = 0.80
Obese patients	1.2 ± 1.0	20.1 ± 14.7	21.3 ± 11.0	18.9 (11.9, 25.9) p < 0.001	20.0 (12.6, 27.4) p < 0.001	−1.1 (−8.5, 6.3) p = 0.77

Data are mean ± SD. BMI = body mass index, CI = confidence interval, HI-NPPV = high intensity non-invasive positive pressure ventilation, iVAPS = intelligent volume assured pressure support, MV = minute ventilation, Non-obese = BMI ≤ 30 kg/m², Obese = BMI > 30 kg/m², Leakage = percentage difference between inspiratory and expiratory tidal volume, RR = respiratory rate, SB = spontaneous breathing.

*Comparison between SB, HI-NPPV and iVAPS made using a linear regression model for repeated measures.