Clinical application value of impulse oscillometry in geriatric patients with COPD

Figures & data

Table 1 Demographics of all the subjects

	Healthy controls	COPD	COPD 1	COPD 2	COPD 3	COPD 4
n	101	133	19	49	38	27
Age (years)	65.07±14.72	71.25±11.24	79.47±8.90	72.96±10.51	71.97±10.37	61.33±8.50
Male/female	70/31	110/23	13/6	39/10	32/6	26/1
BMI (kg/m^2)	24.59±3.26	23.59±4.00	23.11±3.69	25.56±3.67	23.07±3.47	21.09±3.93

Note: Data are expressed as numbers and mean ± standard deviation.

Abbreviation: BMI, body mass index.

Table 2 Demographics of the geriatric population

	Healthy controls		COPD
	Non-geriatric	Geriatric	Non-geriatric	Geriatric
n	58	43	38	95
Age (years)	54.33±8.83	79.56±6.00	56.50±5.34	77.15±6.57
Male/female	43/15	27/16	36/2	74/21
BMI (kg/m^2)	24.95±3.05	24.11±3.50	22.78±4.48	23.91±3.77

Note: Data are expressed as numbers and mean ± standard deviation.

Abbreviation: BMI, body mass index.

Table 3 Demographics of the advanced elderly group

	Healthy controls		COPD
	Non-advanced elderly	Advanced elderly	Advanced elderly	Non-advanced elderly
n	17	26	41	54
Age (years)	73.71±4.87	83.38±2.59	83.29±2.77	72.48±4.41
Male/female	13/4	14/12	32/9	42/12
BMI (kg/m^2)	23.89±2.97	24.25±3.85	23.66±3.80	24.10±3.77

Note: Data are expressed as numbers and mean ± standard deviation.

Abbreviation: BMI, body mass index.

Table 4 Comparison of IOS parameters between the healthy control and COPD groups

	Healthy controls	COPD	COPD 1	COPD 2	COPD 3	COPD 4
Z5 (%predicted)	89.24±29.98	159.50 (111.30 to 225)a	114.32±54.47	150.22±78.02a	195.57±80.87a,b	266.3±138.33a–c
Fres (L/s)	12.62±3.84	23.23±7.60a	16.9±6.52	21.48±5.71a	25.46±6.11a,b	27.71±9.32a–c
X5 (kPa/L/s)	−0.09±0.05	−0.25 (−0.41 to −0.14)a	−0.17±0.12	−0.23±0.18a	−0.33±0.2a,b	−0.49±0.26a–c
R5 (%predicted)	86.56±28.39	140.50 (106.55 to 185.7)a	105.25±44.79	134.52±61.75a	165.54±64.12a,b	214.64±109.68a–c
R20 (%predicted)	82±24.65	97.92±33.42a	84.48±25.25	96.55±31.44a	100.26±38.42a,b	106.61±32.9a,b
R5–R20 (%predicted)	115.96±103.54	458.23 (241.95 to 663.40)a	248.8±258.35	382.9±312.48a	606.22±295.68a,b	920.03±664.1a–c

Notes: Data are expressed as mean ± standard deviation and median (IQR).

a P<0.05 compared with the healthy controls.

b P<0.05 compared with COPD 1.

c P<0.05 compared with COPD 2.

Abbreviations: IOS, impulse oscillometry; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance; IQR, inter-quartile range.

Table 5 Correlation between the IOS and spirometry parameters in COPD

		Z5 (%predicted)	Fres (L/s)	X5 (kPa/L/s)	R5 (%predicted)	R20 (%predicted)	R5–R20 (%predicted)
FVC (%predicted)	r	−0.450**	−0.361**	0.415**	−0.416**	−0.173*	−0.491**
FEV1 (%predicted)	r	−0.564**	−0.520**	0.561**	−0.528**	−0.212*	−0.628**
FEV1/FVC (%)	r	−0.492**	−0.481**	0.517**	−0.474**	−0.139	−0.572**
MMEF (%predicted)	r	−0.530**	−0.511**	0.555**	−0.509**	−0.228**	−0.588**

Notes:

* P<0.05.

** P<0.001.

Abbreviations: IOS, impulse oscillometry; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance; FVC, forced vital capacity; r, Pearson’s or Spearman’s correlation coefficient; FEV₁, forced expiratory volume in 1 second; MMEF, maximum midexpiratory flow rate.

Figure 1 Changes in IOS parameters with increasing airflow limitation.

Notes: ^aP<0.05 compared with the healthy controls. ^bP<0.05 compared with COPD 1. ^cP<0.05 compared with COPD 2.
Abbreviations: IOS, impulse oscillometry; R5–R20, respiratory resistance; Fres, resonant frequency; X5, respiratory reactance; Z5, respiratory impedance.

Table 6 Comparison of the pulmonary function parameters between the groups of 65-year-olds

	Healthy controls		COPD
	Non-geriatric	Geriatric	Non-geriatric	Geriatric
FVC (%predicted)	97.24±15.18	97.26±20.50	66.79±18.90b	76.40±18.95a,c
FEV1 (%predicted)	95.04±15.16	98.6±20.72	37.78±20.79b	54.63±20.73a,c
FEV1/FVC (%)	79.45±5.14	77.64±6.34	42.69±15.53b	53.23±12.56a,c
MMEF (%predicted)	74.12±23.08	65.78±28.10	14.36±11.41b	19.70±11.18a,c
Z5 (%predicted)	96.37±28.77	79.62±29.19d	215.72±135.42b	167.97±85.05a,c
Fres (L/s)	12.23±3.83	13.14±3.84	24.65±8.94b	22.66±6.96a
X5 (kPa/L/s)	−0.09±0.05	−0.10±0.06	−0.34±0.28b	−0.29±0.20a
R5 (%predicted)	92.84±29.04	78.09±25.43d	176.56±105.00b	147.03±66.86a
R20 (%predicted)	90.47±25.86	70.58±17.53d	102.29±32.82	96.18±33.67a
R5–R20 (%predicted)	107.22±107.23	127.75±98.34	658.04±640.25b	488.01±350.12a

Notes: Data are expressed as mean ± standard deviation.

a P<0.001 compared with the geriatric healthy patients.

b P<0.001 compared with the non-geriatric healthy patients.

c P<0.05 compared with the non-geriatric COPD patients.

d P<0.01 compared with the non-geriatric healthy patients.

Abbreviations: FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; MMEF, maximum midexpiratory flow rate; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance.

Table 7 Correlation between the IOS and spirometry parameters in geriatric COPD patients

		Z5 (%predicted)	Fres (L/s)	X5 (kPa/L/s)	R5 (%predicted)	R20 (%predicted)	R5–R20 (%predicted)
FVC (%predicted)	r	−0.373**	−0.253*	0.345**	−0.337**	−0.197	−0.390**
FEV1(%predicted)	r	−0.527**	−0.479**	0.514**	−0.499**	−0.293**	−0.551**
FEV1/FVC (%)	r	−0.469**	−0.450**	0.452**	−0.455**	−0.239*	−0.514**
MMEF (%predicted)	r	−0.456**	−0.494**	0.445**	−0.464**	−0.345**	−0.447**

Notes:

* P<0.05.

** P<0.001.

Abbreviations: IOS, impulse oscillometry; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance; FVC, forced vital capacity; r, Pearson’s correlation coefficient; FEV₁, forced expiratory volume in 1 second; MMEF, maximum midexpiratory flow rate.

Table 8 Comparison of the pulmonary function parameters between the groups of 80-year-olds

	Healthy controls		COPD
	Non-advanced elderly	Advanced elderly	Non-advanced elderly	Advanced elderly
FVC (%predicted)	92.76±16.11	100.19±22.74	74.45±18.06b	78.97±19.99a
FEV1(%predicted)	93.25±18.77	102.10±21.53	49.81±19.89b	60.97±20.33a,c
FEV1/FVC (%)	77.53±7.01	77.72±6.01	50.41±13.13b	56.95±10.84a,c
MMEF (%predicted)	65.81±29.60	65.76±2,768	17.13±10.27b	22.90±11.55a,c
Z5 (%predicted)	80.64±30.35	78.95±2,901	189.76±96.32b	139.26±56.75a,c
Fres (L/s)	13.81±3.94	12.70±3.78	23.45±7.15b	21.62±6.64a
X5 (kPa/L/s)	−0.10±0.05	−0.10±0.07	−0.33±0.22b	−0.23±0.15a,c
R5 (%predicted)	81.04±23.25	76.16±2,704	165.98±75.20b	122.07±43.47a,c
R20 (%predicted)	74.12±16.62	68.27±1803	105.02±36.65b	84.53±25.29a,c
R5–R20 (%predicted)	125.50±83.07	129.22±108.75	567.23±396.92b	383.68±244.33a,c

Notes: Data are expressed as the mean ± standard deviation.

a P<0.001 compared with the advanced elderly healthy patients.

b P<0.001 compared with the non-advanced elderly healthy patients.

c P<0.05 compared with the non-advanced elderly COPD patients.

Abbreviations: FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; MMEF, maximum midexpiratory flow rate; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance.

Table 9 Correlation between the IOS and spirometry parameters in advanced elderly COPD patients

		Z5 (%predicted)	Fres (L/s)	X5 (kPa/L/s)	R5 (%predicted)	R20 (%predicted)	R5–R20 (%predicted)
FVC (%predicted)	r	−0.377*	−0.264	0.280	−0.334*	−0.110	−0.466**
FEV1 (%predicted)	r	−0.615**	−0.532**	0.560**	−0.558**	−0.286	−0.639**
FEV1/FVC (%)	r	−0.587**	−0.556**	0.605**	−0.519**	−0.292	−0.540**
MMEF (%predicted)	r	−0.487**	−0.368*	0.454**	−0.470**	−0.323*	−0.452**

Notes:

* P<0.05.

** P<0.001.

Abbreviations: IOS, impulse oscillometry; Z5, respiratory impedance; Fres, resonant frequency; X5, respiratory reactance; R5–R20, respiratory resistance; FVC, forced vital capacity; r, Pearson’s correlation coefficient; FEV₁, forced expiratory volume in 1 second; MMEF, maximum midexpiratory flow rate.

Table 10 The AUC of IOS parameters in different groups

IOS parameters	AUC in overall patients	AUC in the geriatric patients	AUC in the advanced elderly patients
Fres (L/s)	0.905	0.909	0.914
R5–R20 (%predicted)	0.883	0.885	0.863
X5 (kPa/L/s)	0.854	0.850	0.800
Z5 (%predicted)	0.838	0.872	0.834
R5 (%predicted)	0.829	0.867	0.825
R20 (%predicted)	0.654	0.768	0.711

Abbreviations: ROC, receiver operating characteristic; AUC, area under the curve; IOS, impulse oscillometry; Fres, resonant frequency; R5–R20, respiratory resistance; X5, respiratory reactance; Z5, respiratory impedance.

Table 11 The cutoff value of Fres and its sensitivity, specificity, and Youden’s index

	Fres cutoff values	Sensitivity	Specificity	Youden’s index
Overall subjects	17.715	0.789	0.931	0.720
Geriatric subjects	16.94	0.853	0.860	0.713
Advanced elderly	16.94	0.829	0.885	0.714

Abbreviation: Fres, resonant frequency.

Figure 2 ROC curves for COPD in the overall subjects (A), geriatric subjects (B), and advanced elderly subjects (C).

Abbreviations: ROC, receiver operating characteristic; X5, respiratory reactance; R5–R20, respiratory resistance; Fres, resonant frequency; Z5, respiratory impedance.