Letter to editor.

Dear Editor,

We read with interest the study entitled “The effect of incentive spirometer training on oromotor and pulmonary functions in children with Down's syndrome” published in Journal of Taibah University Medical Sciences Volume 14, Issue 5, October 2019, Pages 405–411. I would like to commend the authors for this successful clinical study and a significant contribution to the rehabilitation of children with Down's syndrome (DS).

The study involves thirty-four children with DS randomly allocated into two groups. A valid and reliable tool was used to assess of oromotor and pulmonary functions. The intervention consists of oromotor exercises and incentive spirometry. There are few methodological concerns that must be addressed before clinicians use evidence derived from the study.

There is a threat to internal validity due to the absence of a control group and frail research design. The study design involves two groups, A and B. Group A consists of 15 children receiving oromotor exercises (OE), whereas group B consist of 19 children receives OE plus spirometer training (ST). Such a research design is suitable to assess the effect of the addition of ST. On the contrary, the conclusion of the study states that OE is more effective than ST in improving oromotor and pulmonary function in children with DS. Further, we draw your attention to Table 1, study reported less improvement in pulmonary function in group B, even though the group received both the interventions. Such a scenario is only possible if incentive spirometry inflects detrimental effects on pulmonary function in group B. A recent study on incentive spirometry reported significant effects on pulmonary functions among patients with pulmonary dysfunction.

Table 1

Comparison between pre- and post-study mean values of ruler measure within and between groups.

Ruler measure	Pre-study	Post-study	z-value	p-value	% improvement
	Median (range)	Median (range)
Group-A	1.1 (0.5–1.5)	0.5 (0.4–0.9)	−3.07	0.002	54.5%
Group-B	−0.889	−0.527	−3.18	0.001	63.6%
z-value	0.374	0.598

Using an electric brush to cause sensory stimulation for the improvement of oromotor function can be risky among children with a history of epileptic seizures. Risk mitigation is an essential feature of any experimental research. In the current study, neither inclusion criteria nor exclusion criteria included the screening of children with seizures. Moreover, studies have found that 12% of children with DS suffer from epileptic attacks.

Lastly, the average IQ of children in group B was 59.8 ± 9.1, which is quite high as compared to other studies reporting a mean IQ of children in the same age group about 40.2. In such instances, the external validity of research may be compromised.

Grant support & financial disclosures

None.

Source of funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest

There is no conflict of interest.

Authors contributions

Every author contributed equally in all the parts of the research. All authors have critically reviewed and approved the final draft and are responsible for the content and similarity index of the manuscript.

I am pleased that you were interested in our study and read it thoroughly and I would like to thank you for your comments and I would like to declare them. First of all the title and the aim of the study were clear which is investigating the effect of incentive spirometer (IS) on oromotor function and pulmonary function in children with Down syndrome, group A received oromotor exercises only and group B received the same oromotor exercises as a base for the two groups in addition to IS which was concerned with the investigation. So the title and purpose of the study were matching the study design which is randomized clinical trial not a comparative study with no threat to the internal validity of the research. The results of the study showed that children in both groups were improved but no statistical significant difference was detected between the two groups declaring no effect of IS so this improvement was due to oromotor exercises and this what was meant by the conclusion that oromotor exercises was the cause of the improvement not the IS which had no effect not meaning that it is a comparative study. The editing of the conclusion may be the cause of giving an impression that it is a comparative study and this can be because English language is not our native language. Furthermore Table 1 was not concerned with pulmonary function but with ruler measurement for the distance of mouth opening but Table 2 was showing the results of pulmonary functions. The fourth paragraph in the discussion of the study is supporting your opinion that IS has a positive effect on pulmonary functions as reported by previous studies 1 and that is in disagreement with our study results which found no effect of IS in the targeted population of the study taking in consideration that no available previous studies investigated the effect of IS alone without other chest physical therapy modalities on Down syndrome, so this result could be due to what was mentioned in the limitation of the study about the difficulty of the children to follow the instructions as a result of their intellectual disability. So the decreased percentage of improvement of pulmonary functions in group B than group A was not because IS had detrimental effects on pulmonary functions but may be that the efforts of children in group B were dispersed between oromotor exercises and IS in the session and home program and since IS didn't have effect their percentage of improvement were less than group A whose all effort was condensed on oromotor exercises in session and home program. Regarding the history of seizures the children participated in the study were free from seizures and contraindications of the IS as well as toothbrush were not mentioned in details but we suffice with mentioning that children with serious medical conditions were excluded. Lastly the children participated in the study were not selected according to their IQ level so the IQ reported in the results was of the actual available sample not intentionally selected to affect the external validity of the research. The study that you have mentioned considering the IQ level for these children was not on Egyptian children and not recent. A more recent study performed on the Egyptian children at a sector in Egypt called El Mansoura reported their IQ level 50.1 with SD 13.6.2 Also an Egyptian study conducted on children with Down syndrome using chest physiotherapy including IS included children with IQ more than 70 intentionally.3 References: 1. Tecklin JS. Intellectual disabilities: focus on Down syndrome. In: Bertoti DB, Schreiner MB, editors. Pediatric physical therapy, London: Lippincott Williams & Wilkins, Wolters Kluwer Business; 2015. p. 379–402. 2. Yahia S, El-Hadidy M, El-Gilany A, Hady D, Wahba Y, Al-Haggar M. Disruptive behavior in Down syndrome children: a cross-sectional comparative study. Ann Saudi Med. 2014; 34: 517–521. 3. Ahmed Z. Strength training versus chest physical therapy on pulmonary functions in children with Down syndrome. The EJMHG Ain Shams University. 2017; 18: 35–39.

Table 2

Comparison between pre- and post-study values of forced vital capacity, forced expiratory flow for 1 s, and peak expiratory flow within and between groups.

Item	Pre-study Median (range)	Post-study Median (range)	z-value	p-value	% improvement
FVCGroup A	46 (38–79)	71 (65.6–91.5)	3.38	0.001	54.3%
Group B z-value p-value	67 (51.6–77)−0.9540.340	83 (74.8–91.3)−0.885	3.4	0.001	23.8%
FEV1Group A	51.7 (40.2–90)	75 (60–95)	3.34	0.001	45%
Group B z-value p-value	78.8 (59–81)−1.30.193	89 (80–103)−1.1	2.86	0.004	12.9%
PEFGroup A	40.2 (33–76)	62 (51–72)	2.7	0.006	54%
Group B z-value p-value	65 (54–72)−1.80.059	75.9 (58–92)−1.6	2.35	0.019	16.8%