3 RESULTS
3.1 Clinical characteristics
During the study period, 115 patients were screened, and 109 patients
were enrolled, excluding 4 patients who had been using noninvasive
ventilators and 2 patients treated with nusinersen. The age of the 109
patients were 4.2 (2.1, 7.6) years, ranged (0.2-15.8) years. Fifty-two
patients were males. Twenty-three cases were type 1, 74 cases were type
2, and 12 cases were type 3. Thirty-four cases (31.2%) had RRTIs, 20
cases (18.3%) had ARF within one year, and 31 cases (28.4%) used MI-E
regularly. The general characteristics, survival motor neuron 2 (SMN2)
copies, MI-E usage, main parameters of PSG and lung function of
different types of SMA are shown in Table 1.
3.2 Differences in sex, age, type, BMI and MI-E between the two groups
According to the group criteria, 109 patients were divided into the
disease group with 39 cases and the control group with 70 cases. The
proportion of type 1 was higher and the BMIz was lower in the disease
group than in the control group (P < 0.05). There was no
significant difference in sex, age or MI-E usage between the two groups.
(Table 2)
3.3 Differences in lung function between the two groups
Spirometry was performed in 21 of the 39 patients in the disease group
and 57 of the 70 patients in the control group. The percent predicted
scores representing restrictive ventilation dysfunction, including
forced vital capacity (FVC), inspiratory vital capacity (VC IN),
expiratory vital capacity (VC EX), forced expiratory volume in one
second (FEV1), peak expiratory flow (PEF), maximum expiratory flow at
75% vital capacity (MEF75), maximum expiratory flow at
50% vital capacity (MEF50) and maximum midexpiratory
flow at 25% to 75% vital capacity (MMEF75/25) in the
disease group were all lower than those in the control group (P
< 0.05). There was no significant difference in the FEV1 to
FVC ratio % predicted to represent obstructive ventilation dysfunction
between the two groups (Table 2).
3.4 Differences in PSG between the two groups
End-tidal carbon dioxide (EtCO2) was measured in 9
patients in the disease group and 18 patients in the control group while
PSG was performed. Nonrapid eye movement stage 2 (N2) was higher and N3
was lower in the disease group. In addition, the respiratory arousal
index, AHI, ≥ 3% oxygen desaturation events and index were higher, and
the average oxygen desaturation, MSpO2 and
LSpO2 were lower (P < 0.05). Hypopnea was the
main respiratory event in children with SMA. The events, index, mean
time and longest time of hypopnea in the disease group were all higher
than those in the control group (P < 0.05). There was no
significant difference in apnea events between the two groups (Table 3).
3.5 Logistic regression analysis of risk factors for RRTIs and/or ARF in
children with SMA
Type 1, BMI, AHI and MSpO2 with statistically
significant differences between the two groups were entered as
covariates into binary logistic regression, and all had statistical
significance (P < 0.05), as shown in Table 4. The risk for the
occurrence of RRTIs and/or ARF in SMA type 1 was approximately four
times higher than that in types 2 and 3. Meanwhile, the risks were
approximately 1.5, 1.1 and 1.5 times higher for every 1 decrease in
BMIz, 1 events/h increase in AHI and 1% decrease in
MSpO2, respectively.
3.6 ROC curve analysis of BMIz, AHI and MSpO2
ROC curves were drawn to analyze the prediction efficiency of BMI, AHI
and MSpO2 for RRTIs and/or ARF. The best cutoff points
of these three continuous variables were obtained by taking the maximum
Jordan index, and the sensitivity and specificity are shown in Figure 1
and Table 5. The diagnostic value of MSpO2 was the best,
with the highest area under the receiver operating characteristic curve
(AUC). The sensitivity, specificity and accuracy of
MSpO2 < 95.5% with the occurrence of RRTIs
and/or ARF were 0.539, 0.886, and 0.761, respectively. To improve the
specificity and accuracy, the indicators were used in combination. With
the standard of MSpO2 < 96% and AHI
> 10 events/h or BMI < -1, the specificity and
accuracy were increased to 0.957 and 0.798, respectively, and the
sensitivity was 0.513.