Impulse Oscillometry System for the Diagnosis of Wheezing Episode in Children in Office Practice

Figures & data

Figure 1 Study flowchart.

Table 1 Association Between Final Diagnosis and Demographic and Clinical Parameters

Parameters	Final Diagnosis		p-value
	Wheezing Episode (n=37)	Others (n=46)
Age (years)	4.17±0.95	4.14±0.82	0.989
Gender
Male	19 (51.4%)	28 (60.9%)	0.384
Female	18 (48.6%)	18 (39.1%)
Height (cm)	102.16±5.65	101.15±7.44	0.484
Weight (Kg)	15.35±2.12	14.56±2.90	0.040
Complaints: Cough	2.89±0.77	3.02±0.75	0.436
Complaints: Cold	1.27±0.61	1.35±0.60	0.390
Complaints: Fever	1.62±0.83	1.85±1.01	0.366
Complaints: Breathlessness	1.70±0.88	1.52±0.69	0.418
Heart Rate (per minute)	117.86±16.56	109.93±17.66	0.022^a
Respiratory Rate (cycles per minute)	40.38±7.44	35.76±5.26	0.001^a
Respiratory System Examination
Clear	10 (27.0%)	27 (58.7%)	<0.001^a
Rhonchi	25 (67.6%)	7 (15.2%)
Crepts	2 (5.4%)	10 (21.7%)
Crepts+ Rhonchi	0 (0.0%)	2 (4.3%)
SpO2 (%)	95.97±2.03	96.59±1.26	0.195
Hemoglobin (g/dL)	11.13±0.98	11.22±1.36	0.817
Packed cell volume (%)	35.05±2.52	33.85±3.07	0.126
Platelet Count (/cu.mm)	373,400.00±106,682.71	339,846.15±97,480.13	0.279
Total leukocyte count (/cu.mm)	9,445.00±2,023.41	8,719.23±2841.41	0.318
ESR, (mm/Hr)	20.95±3.93	20.54±5.25	0.807

Notes: Values presented as mean±SD (where otherwise not specified); ^ap-value<0.05 is taken as significant.

Abbreviation: ESR, erythrocyte sedimentation rate.

Table 2 Significance of Impulse Oscillometry Parameters in Wheezing Episode and Others

IOS Parameter	Wheezing Episode		Others	p-value
AX Actual value (Pre-Nebulization) (kPa/L)	7.33±8.21		4.00±1.99	0.001*
AX Actual value (Post-Nebulization) (kPa/L)	4.79±6.82		3.61±1.71	0.402
Change in AX (Post-Nebulization) (kPa/L)	−2.55±4.43		−0.39±1.16	<0.001*
Percent Change as compared to predicted value AX (Post-Nebulization) (%)	172.90±1,208.34		2.78±63.53	<0.001*
R5: Predicted (kPa/lt/s)	0.99±0.21		1.07±0.18	0.146
R5: Actual value (Pre-Nebulization) (kPa/lt/s)	1.32±0.51		1.02±0.30	0.002*
R5: Actual value (Post-Nebulization) (kPa/lt/s)	1.07±0.43		1.00±0.27	0.425
Percent Change in R5: Observed (Post-Nebulization)(ΔR5)	−12.80±35.24		0.81±24.18	<0.001*
Change in R5: Actual value (Post-Nebulization) (kPa/lt/s)	−0.25±0.35		−0.02±0.18	<0.001*
Change in R5: Percent of Predicted (Post-Nebulization) (%)	−28.60±41.44		−2.03±15.62	<0.001*
X20: Predicted (kPa/lt/s)	0.03±0.02		0.03±0.02	0.810
X20: Actual value (Pre-Nebulization) (kPa/lt/s)	−0.20±0.20		−0.08±0.07	<0.001*
X20: Actual value (Post-Nebulization) (kPa/lt/s)	−0.11±0.18		−0.07±0.07	0.460
Change in X20: Actual value (Post-Nebulization) (kPa/lt/s)	0.10±0.10		0.01±0.07	<0.001*
Percent Change in X20: Observed (Post-Nebulization) (kPa/lt/s)	−128.32±355.53		−4.90±107.01	0.001*
Change in X20: Percent of Predicted (Post-Nebulization)	236.62±294.20		21.67±222.88	<0.001*
Resonant Frequency Actual value (Pre-Nebulization) (Hz)	26.49±6.33		23.48±2.81	0.005*
Resonant Frequency Actual value (Post-Nebulization) (Hz)	24.53±7.12		22.98±2.72	0.394
Change in Resonant Frequency (Post-Nebulization)	−1.95±3.86		−0.50±2.39	0.022
Percent Change in Resonant Frequency (Post-Nebulization)(%)	−6.78±13.97		−1.63±9.89	0.026
Provisional Diagnosis				0.202
Wheezing Episode	18 (48.6%)		16 (34.8%)
Others	19 (51.4%)		30 (65.2%)

Abbreviations: IOS, impulse oscillometry system; AX, area of reactance; R5, resistance at 5 Hz frequency; ΔRx, (Rx post-bronchodilation - Rx pre-bronchodilation/Rx pre-bronchodilation), X20, reactance at frequency 20 Hz.

Table 3 Sensitivity, Specificity, Positive Predictive Value, and Negative Predictive Value of Significant IOS Parameters

Variable	Sensitivity	Specificity	PPV	NPV	Diagnostic Accuracy
Change in AX (Post-Nebulization) (Cut-off: −1.38 by ROC) (AUROC=0.781)	70.3% (53–84)	80.4% (66–91)	74.3% (57–88)	77.1% (63–88)	75.9% (65–85)
Percent Change in AX (Post-Nebulization) (Cut-off: −34.59 by ROC) (AUROC=0.764)	62.2% (45–78)	89.1% (76–96)	82.1% (63–94)	74.5% (61–85)	77.1% (67–86)
Change in R5: Actual value (Post-Nebulization) (Cut-off: −0.24 by ROC) (AUROC=0.785)	62.2% (45–78)	93.5% (82–99)	88.5% (70–98)	75.4% (62–86)	79.5% (69–88)
Change in R5: Percent of Predicted (Post-Nebulization) (Cut-off: −19.101 by ROC)	73.0% (56–86)	93.5% (82–99)	90.0% (73–98)	81.1% (68–91)	84.3% (75–91)
Percent Change in R5 (Post-Nebulization) (Cut-off: −16.667 by ROC) (AUROC=0.784)	67.6% (50–82)	91.3% (79–98)	86.2% (68–96)	77.8% (64–88)	80.7% (71–89)
Change in X20: Actual value (Post-Nebulization) (Cut-off: 0.03 by ROC) (AUROC=0.813)	83.8% (68–94)	56.5% (41–71)	60.8% (46–74)	81.2% (64–93)	68.7% (58–78)
Percent Change in X20 (Post-Nebulization) (Cut-off: −40 by ROC) (AUROC=0.707)	81.1% (63–92)	65.9% (50–80)	66.7% (51–80)	80.6% (64–92)	72.8% (60–81)
Change in Resonant Frequency (Post-Nebulization) (Cut-off: −0.83 by ROC) (AUROC=0.647)	67.6% (50–82)	58.7% (43–73)	56.8% (41–72)	69.2% (52–83)	62.7% (51–73)
Percent Change in Resonant Frequency (Post-Nebulization) (Cut-off: −4.13 by ROC) (AUROC=0.642)	67.6% (50–82)	60.9% (45–75)	58.1% (42–73)	70.0% (53–83)	63.9% (53–74)

Abbreviations: PPV, Positive predictive value of having a wheezing episode if ΔR5Hz is lower than or equal to that specified in the first column; NPV, negative predictive value of not having a wheezing episode if ΔR5Hz is higher than or equal to that specified in the first column; ROC, receiver operating curve; AUROC, area under receiver operating curve.

Table 4 The Odds Ratio for Significant Parameters of Impulse Oscillometry

Variable	LR+	LR-	Yuden Index	Odds Ratio	Kappa	p-value
Change in AX (Post-Nebulization) (Cut-off: −1.38 by ROC)	3.59 (1.93–6.69)	0.37 (0.22–0.62)	50.7	9.72 (3.53–26.78)	0.51	<0.001
Percent Change in AX percent predicted (Post-Nebulization) (Cut-off: −34.59 by ROC)	5.72 (2.41–13.58)	0.42 (0.28–0.65)	51.3	13.47 (4.30–42.19)	0.53	<0.001
Change in R5: Actual value (Post-Nebulization) (Cut-off: −0.24 by ROC)	9.53 (3.10–29.29)	0.40 (0.27–0.62)	55.6	23.55 (6.13–90.45)	0.57	<0.001
Change in R5: Percent of Predicted (Post-Nebulization) (Cut-off: −19.101 by ROC)	11.19 (3.68–34.00)	0.29 (0.17–0.49)	66.5	38.70 (9.76–153.37)	0.68	<0.001
Percent Change in R5: (Post-Nebulization) (Cut-off: −16.667 by ROC)	7.77 (2.97–20.35)	0.36 (0.22–0.57)	58.9	21.88 (6.36–75.23)	0.6	<0.001
Change in X20: Actual value (Post-Nebulization) (Cut-off: 0.03 by ROC)	1.93 (1.35–2.76)	0.29 (0.13–0.62)	40.3	6.72 (2.35–19.21)	0.39	<0.001
Percent Change in X20: Percent of Predicted (Post-Nebulization) (Cut-off: −40 by ROC)	2.35 (1.51–3.65)	0.30 (0.15–0.61)	45.9	7.73 (2.74–21.80)	0.45	<0.001
Change in Resonant Frequency (Post-Nebulization) (Cutoff: −0.83 by ROC)	1.64 (1.09–2.47)	0.55 (0.33–0.93)	26.3	2.96 (1.20–7.32)	0.26	0.017
Percent Change in Resonant Frequency (Post-Nebulization) (Cutoff: −4.13 by ROC)	1.73 (1.13–2.64)	0.53 (0.32–0.90)	28.4	3.24 (1.31–8.03)	0.28	0.010

Abbreviation: LR, likelihood ratio.