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Indian Pediatr 2013;50: 957-960 |
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Assessment of Bronchodilator Response in
Preschool Children by Pulmonary Function Tests
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Babak Ghalibafsabbaghi, Dinesh Raj, Rakesh Lodha, and
S K Kabra
From Division of Pulmonology, Department of
Pediatrics, All India Institute of Medical Sciences, Ansari Nagar,
New Delhi, 110029, India.
Correspondence to: Dr S K Kabra, Professor, Division
of Pulmonology, Department of Pediatrics, All India Institute of Medical
Sciences, Ansari Nagar, New Delhi, 110029, India.
Email: [email protected]
Received: February 05, 2013;
Initial review: February 19, 2013;
Accepted: March 30, 2013.
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We performed pulmonary function
test to document bronchodilator response by using tidal breathing
flow volume loop (TBFVL), rapid thoracic compression (RTC), and
raised volume rapid thoracic compression (RVRTC) techniques.
Thirty-nine children (mean age 45.2 months) were evaluated. The
parameters that showed significant improvement after bronchodilator
administration included TEF10/ PTEF ratio in TBFVL, and FEF25-75%,
FEV1and PEF in RVRTC. None of the parameters measured in RTC showed
significant improvement. We conclude FEV1, PEF and FEF25-75% in
RVRTC have greater sensitivity for detection of airways changes.
Keywords: Bronchodilator, Infant,
Pulmonary function test.
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Objective documentation of bronchodilator response
in adults and older children may be carried out using forced expiratory
maneuvers in spirometry, this may not be possible in infants and
preschool children. In this age group, modified methods to assess airway
status in form of tidal breathing flow volume loop (TBFVL), rapid
thoracic compression (RTC), and raised volume rapid thoracic compression
(RVRTC) techniques have been developed. It has been demonstrated that in
RVRTC, flow limitation can be achieved during forced expiratory
maneuvers in infants when initiated from near total lung capacity [1,2].
RTC and TBFVL were used for assessment of severity of airway obstruction
[3]. These tests have been used to document air trapping in normal
children and those with cystic fibrosis [4], and to document diminished
pulmonary function test in infants with cystic fibrosis (CF) [5].
Documentation of bronchodilatory response is limited to a study in acute
bronchiolitis [6] and in infants/children with recurrent episodes of
wheezing [7,8]. No study has compared sensitivity of various indices to
detect bronchodilatory response by these techniques. Therefore, we
planned a study on infants and pre-school children with probable asthma
to assess response to inhaled bronchodilator using clinical scores and
to check sensitivity of various parameters obtained by TBFVL, RTC and
RVRTC technique to identify bronchodilator response.
Methods
This prospective cross-sectional study was carried
out at a tertiary care center in India. Infants and pre-school children
with probable asthma, weighing between 8-20 kg, who had presented to the
pediatric out-patient department, were enrolled. Children presenting
with acute onset cough without fever with past history of atleast more
than two episodes of wheeze and family history of asthma (parents or
sib) with or without wheeze were labeled as probable asthma. The study
was approved by Institutional Ethics Committee. Detailed history and
examination findings were recorded.
A previously validated clinical score, i.e.
Respiratory Distress Assessment Instrument (RDAI) [4] including
respiratory rate, heart rate, oxygen saturation, presence of wheeze and
chest indrawing, was recorded before and after administration of
bronchodilators. Pulmonary function tests (PFT) were performed on
EXHALYZER/D (Eco Medics AG, Switzerland using standard guidelines
[9]. The techniques used included: TBFVL, RTC, RVRTC. Procedure was
explained to all participants and if child was not cooperative, sedation
with triclofos (50 mg/kg) was used. After performing baseline PFTs,
salbutamol was administered (100 µg/puff, 2 puffs) using a metered dose
inhaler (MDI) and small volume spacer (350 cc) with a mask; PFTs and
clinical scores were performed again after 15-20 minutes.
We considered the test values acceptable when at
least 4 cycles in TBFVL and at least 3 curves of technically acceptable
breath cycles in RTC and 2 acceptable breath cycles in RVRTC were
obtained. For calculation of sensitivity for various parameters, an
increase of more than 15% from baseline after salbutamol inhalation was
considered significant [10].
As there was no similar study in literature, we
planned to do this pilot study to include 30 preschool children. Data
were analyzed using Stata 11 (StataCorp, College Station, TX). Data are
presented in frequency percentage, mean ± SD, and confidence interval
(95%). Paired t-test or Wilkoxon signed rank test were employed,
for data following normal distribution or non-normal distribution,
respectively.
Results
A total of 39 (30 boys) preschool children were
enrolled in the study over a period of 12 months. The mean age of
enrolled subjects was 45.2 ± 14.6 months (range 9 to 58 months); their
mean height was 96 ± 9.5 cm (range 68 to 111 cm) and mean weight was
13.6 ± 2.6 kg (range 8.2 to 19.2 kg). Family history of asthma was
present in either parents in 22 (57%) and only in sibs in 17 (43%).
Wheezing was audible in 63% of patients.
Baseline RDAI scores (mean + SD) was 2.48 (2.15) and
improved to 1.17 (1.95) (P<0.05). Of the 39 patients, TBVFL could
be performed in all patients, RTC in 38/34 (pretest/post test) and RVRTC
in 34/31(pretest/post test). Table I shows changes in
various indices before and after administration of the bronchodilator.
Web Table I shows association between changes in clinical
scores and changes in various indices of PFTs. A significant association
was found between
≥2
change in RDAI score and
≥15%
change in test result in RTC (V70%: P=0.04) and RVRTC (VPEF/VE%:
P= 0.015).
TABLE I Changes in Various Parameter Measured by Various Test Instrument Before and After Bronchodilator
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Pre test |
Post test |
Percentage change |
CI (95%) |
P value |
TBFVL |
PTEF |
0.23 ± 0.145 |
0.24 ± 0.011 |
16.06 |
(-3.10, 35.24) |
0.2641 |
t_E/t_tot |
55.71 ± 5.18 |
54.86 ± 5.15 |
-1.14 |
(-4.00, 1.70) |
0.2784 |
t_PTEF/t_E |
34.73 ± 12.31 |
33.3 ± 11.54 |
2.64 |
((-9.08, 14.37) |
0.4735 |
MTEF |
0.142 ± 0.053 |
0.154 ± 0.071 |
13.56 |
( -3.48, 30.61) |
0.2358 |
TEF75 |
0.193 ± 0.071 |
0.215 ± 0.10 |
17.72 |
(-1.56, 37.02 ) |
0.1391 |
TEF50 |
0.189 ± 0.072 |
0.212 ± 0.093 |
19.76 |
(1.55, 37.97 ) |
0.08 |
TEF25 |
0.160 ± 0.0640 |
0.172 ± 0.078 |
14.76 |
(-1.03, 30.56) |
0.2397 |
TEF10 |
0.129 ± 0.051 |
0.132 ± 0.066 |
8.49 |
(-7.27, 24.26 ) |
0.741 |
TEF50/TIF50 |
84 ± 19.68 |
89.26 ± 30.67 |
8.75 |
(-2.31, 19.83) |
0.2782 |
TEF75/PTEF |
90.45 ± 7.41 |
88.64 ± 10.48 |
1.85 |
(-5.49, 2.002) |
0.2517 |
TEF50/PTEF |
88.49 ± 6.69 |
88.63 ± 5.0 |
0.582 |
(-2.01, 3.18) |
0.897 |
TEF25/PTEF |
75.13 ± 10.44 |
72.73 ± 8.20 |
-1.91 |
(-6.50 , 2.678 ) |
0.1057 |
TEF10/PTEF |
61.55 ± 13.11 |
55.5 ± 12.66 |
-7.96 |
(-14.99, -.93 ) |
0.0047 |
PTEF/V_TE |
1.450 ± 0.530 |
1.556 ± 0.466 |
12.22 |
(3.60, 20.84) |
0.1133 |
RTC |
Vmax FRC |
375.7 ± 152.2 |
411 ± 204.4 |
56.6 |
(13.53, 99.70) |
0.5154 |
V50% |
387.2 ± 26.7 |
411 ± 35.06 |
12.3 |
(-3.00, 27.75) |
0.5289 |
V70% |
330 ± 179.7 |
339.5 ± 209 |
22.2 |
(-13.53,58.04) |
0.5784 |
PEF |
440.6 ± 140.4 |
477.7 ± 165.5 |
13.7 |
(-.20, 27.66 ) |
0.2855 |
RVRTC |
Vmax FRC2 |
210 ± 141.6 |
315 ± 242.35 |
139.0 |
(-59.8, 337.9) |
0.5846 |
V50% 2 |
281.2 ± 216.1 |
349.8 ± 246.68 |
151.8 |
(-106.5, 410.2) |
0.0703 |
V70% 2 |
219.8 ± 196.7 |
291.5 ± 257.55 |
139.2 |
(-91.4, 369.8) |
0.2286 |
FEV |
1.92 ± 104 |
196 ± 101 |
30.18 |
( -3.22, 63.59) |
0.2989 |
MEF25% |
289.8 ± 190.3 |
335.6 ± 187.58 |
85.47 |
(7.30,163.6 ) |
0.118 |
MEF10% |
279.7 ± 200.6 |
296 ± 213.25 |
78.1 |
(-7.03,163.2) |
0.3764 |
MEF25%/FEV |
1.52 ± 0.731 |
3.07 ± 6.81 |
43.4 |
(-.78 ,87.77) |
0.1203 |
FEF25-75% |
293 ± 192.94 |
364 ± 198.70 |
86.61 |
(23.5, 149.7) |
0.0598 |
FEV0.5 |
134.6 ± 76.3 |
159.9 ± 86.9 |
118.2 |
( 11.59, 224.8) |
0.1579 |
FEV.75 |
181 ± 100.4 |
181.7 ± 83.2 |
99.82 |
(22.97, 176.6) |
0.2787 |
FEV 1 |
221± 129 |
201 ± 82 |
71.6 |
(20.87,1 22.3) |
0.018 |
PEF |
393.3 ± 189.1 |
482.9 ± 210.7 |
76.2 |
(-1.93, 154.45) |
0.0205 |
VPEF/VE% |
35.7 ± 27.9 |
29.42 ± 31 |
9.59 |
( -47.65, 66.84) |
0.3876 |
Paired t-test / Wilcoxon signed rank; AVF: Area of
flow volume loop , EEL: End expiratory level , ERV:
expiratory reserve volume, MTEF: Mean tidal expiratory
flow, MTIF: Mean tidal inspiratory flow, PTEF: Peak tidal
expiratory flow, PTIF: Peak tidal inspiratory flow, t_E:
Expiratory time, t_I: Inspiratory time, t_PTEF :time to PTEF,
t_PTIF: time to PTIF; t_tot: total breath time ,TEF: tidal
expiratory flow, TPEF/TE: time ratio of peak-TEF in time of
expiration , V_T: Tidal volume
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We reanalyzed data (not shown here) after excluding
infants and children without wheeze. The results did not change. However
sensitivity of some indices [(TBVFL): t_E/t_tot, TEF75, TEF25, (RVRTC):
TEF10/PTEF, VmaxFRC2, V70%2, PEF] showed improving trends without
statistically significant deference.
Discussion
In the present study, we observed that FEV1
and PEF in RVRTC have more sensitivity to detect changes in airways
diameter but various indices in RTC were not a sensitive test for same
purpose. RTC maneuver works at a fraction of vital capacity and
therefore it has less sensitivity than RVRTC. Other reason for low
sensitivity of indices obtained from RTC include high intra individual
variability due to lack of achieving flow limitation [11,12]. RTC has
been reported to be less useful than RVRTC in infants with cystic
fibrosis [4,5]. Modl, et al. [6] studied 17 infants with acute
bronchiolitis and compared RTC and RVRTC and found significant
difference in VMaxFRC and
FEV0.5 after
bronchodilators. However, we found FEV1
as a sensitive test in our study but it was feasible in 36% of our
patients. Mekus at al also observed that a calculation of FEV1 was
rarely feasible in young infants [13].
We observed increased coefficient of variability in
RTC as well RVRTC because we used less pressure (10-20 mm Hg) as
recommended by manufacturer and used sedation in only 4 infants as
compared to other reports [6,7] that used more pressure and sedation in
all patients [6,7]. Lower ratio of TPTEF/TE has been studied as a
potential tool for detecting airway obstruction [3,4,15]. We found
TEF10/ PTEF ratio more useful (P= 0.0047). We could find
association of ≥2
change in score and
≥15%
change in test result in V 70%
(RTC) and VPEF/VE% (RVRTC) but these parameters weren’t recognized as
sensitive tests for detection of airways changes.
Strengths of our study include demonstration of
bronchodilator response objectively by using various parameters and
documented sensitivity of indices for detection of bronchodilator
response. Limitations include: inclusion of children without wheeze at
time of performing test, not using sedation in all the patients and not
measuring FRC. These limitations are likely to affect the measurements.
We conclude that pulmonary function test in infants
and preschool children are feasible and are evolving. More studies are
required to assess the utility of various indices.
Contributors: BG, SKK, RL: Involved in designing
study, performing test, data analysis and manuscript writing. DR:
involved in data analysis and manuscript writing. SKK will act as
guarantor for the paper.
Funding: None; Conflict of interest: None
stated
What This Study Adds?
• Pulmonary function tests can be used to
document bronchodilator response in preschool children with
wheeze.
• FEV1, PEF and FEF25-75% in RVRTC have
greater sensitivity for detection of airways changes.
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