Saturation Dip Research Articles

Interleukin 8 in children with obstructive sleep apnea before and after adenotonsillectomy

ObjectiveTo assess serum interleukin 8 (IL-8) levels after adenotonsillectomy in children with symptoms suggestive for OSA.Study designProspective interventional study.SettingsThe study was carried out on 30 children with OSA attending ENT clinic of Suez Canal University Hospital.MethodsIncluding, children with sleep-related chronic intermittent hypoxia (CIH) and OSA symptoms performed an elective adenotonsillectomy, and aged (3–12 years). Excluding, children with acute tonsillitis, cardiorespiratory, craniofacial, or diseases affecting IL-8 level as cystic fibrosis, COVID-19 patients, and hepatitis C, taking drugs affecting IL-8 level as benzodiazepines or glutamine supplementation. Children were subjected to full history, clinical examination and laboratory investigations. Nocturnal pulse oximetry (ChoiceMMed) was performed (48–72 h preoperative and 3–4 weeks postoperative) used to determine the number of 4% dips in saturation from baseline, and the nadir saturation (nSAT). IL-8 was measured 1 month pre-operative and 1 month post-operative by flow cytometry using the Human Inflammatory Cytometric Bead Array kit.ResultsThe mean preoperative IL-8 (237.55 p/ml) and oxygen desaturation index (7.77%)cwere statistically significantly higher than mean postoperative IL-8 (207.98 p/ml) and oxygen desaturation index (2.90). The mean pre-operative SpO2 is 98.27 ranged (96.00–100.0%), while the mean postoperative SpO2 is 98.77 ranged (97.00–100.0%), with no statistically significant difference between them (p = 0.069). Preoperative IL-8 (p/ml), postoperative IL-8 (p/ml), and preoperative SpO2 (%) were found to be negatively correlated with IL-8 change.ConclusionIL-8 level significantly decreased after adenotonsillectomy in children with symptoms suggestive for OSA.

High stability in near-infrared spectroscopy: part 1, adapting clock techniques to optical feedback

Optical feedback is an efficient way to narrow and stabilise semi-conductor lasers. As a step forward for ultra-stable, yet highly tunable sources, we developed a new prototype of a three-mirror V-shaped optical cavity (VCOF). It is made of a precisely machined Zerodur spacer, that holds 3 optical contacted mirrors forming a high finesse V-shaped cavity. This arrangement allows the resonant light to be sent back to the seeding laser, triggering a drastic narrowing of the emission linewidth well below the cavity mode width without the need for high-bandwidth active electronic lock of the laser on the cavity. Low expansion material and precise temperature control of the reference cavity leads to a source with Hz level frequency drift and 70 Hz-level emission linewidth at 215 THz. We discuss the benefits of this new prototype compared to its predecessor for high-sensitivity cavity ring down spectroscopy (CRDS). To serve this purpose, the frequency stabilised laser was characterised on short, mid and long time scales, using a high finesse etalon, a self referenced optical frequency comb and a long term saturated CRDS absorption Lamb dip measurement on water.

Prevention of Morbidity in Sickle Cell Disease Phase II (Improvement of Cognition in children with Sickle Cell Disease with Auto-adjusting Continuous Positive Airways Pressure: Phase II) (POMS 2b paediatric cohort)

▪Background: Complications in sickle cell anemia (SCA, HbSS) include neurocognitive difficulties in attention and processing speed associated with low daytime and night-time oxygen saturation. These effects can be compounded by obstructive sleep apnea (OSA).However, there is concern that oxygen supplementation in SCA may lead to bone marrow suppression. Continuous Positive Airways Pressure (CPAP) is an accepted treatment for OSA in the general population and prevents dips in oxygen saturation.. The aim of this single-blind, randomised, controlled phase II trial is to compare Auto-adjusting CPAP (APAP) with standard care to standard care alone in subjects with HbSS to determine whether the intervention is safe and improves Cancellation, a measure of selective attention and processing speed.Methods: Eligibility criteria included ability to provide informed consent, age >8 and <16 years, diagnosis of HbSS and mean overnight saturation of <90% for <30% of the night. Key exclusion criteria were overnight respiratory support, respiratory or decompensated cardiac failure, chronic transfusion or contra-indications to APAP therapy or MRI.Minimisation/stratification factors were age group (8-11, 12-15 years), silent infarction on MRI, minimum overnight oxygen saturation >90% or <90%, and hydroxyurea (HU) use.APAP adherence was defined as using APAP for an average of 4 hours a night for >50% of the time and was recorded using software documenting hours of use each night. Participant support in terms of appropriate facemask and facilitating adherence were provided by an unblinded sleep physiologist.Full blood counts were obtained at baseline, 2 weeks, 3 months and 6 months.Data were analysed by intention-to-treat. The primary outcome is change in the Cancellation subtest from the Wechsler scales, and secondary outcomes include general cognitive functioning, assessed at baseline and after 6 months of treatment by assessors blind to treatment assignment. Analysis of Covariance (ANCOVA) models, adjusted for minimisation factors, were used to calculate least-square mean changes from baseline to 6 months.Results: 30 children (18 boys; median age 12.5; range 7.9-16 years) with SCA were randomised to standard care + APAP (n=15) or standard care alone (n=15) for 6 months. One child in the standard care alone arm withdrew after 6 weeks, and 8 children in the APAP arm were not adherent to treatment. Increase in cancellation score was numerically greater in the APAP arm (mean 1.46, SE 0.59 vs 1.01, SE 0.61) but this was not significant (mean difference 0.44, 95% CI: -1.42; 2.31; p=0.626). Increase in Cancellation score was greater (mean 2.63; 95%CI: 0.95, 4.30) in those whose adherence was in the highest quartile (> 2.4 hours/night) compared with the other 3 quartiles (mean 0.71, 95%CI: -0.32, 1.75; mean difference 1.91, 95%CI: -0.06, 3.88; p=0.057). In subjects assigned to APAP, cancellation scores were significantly higher with hydroxyurea use (p=0.01). There was no evidence of decline in haemoglobin in either group; hydroxyurea use was associated with an increase in haemoglobin (p=0.01). There were 7 subjects with serious adverse events in the standard care alone arm, compared to 3 in the APAP + standard care arm, all related to hospital admission for pain.Discussion: APAP for 6 months is feasible and safe in children with SCA. Alhough >50% were not adherent by the pre-defined definition, those who were compliant appeared to have more benefit in terms of improvement in attention/processing speed. There appears to be an interaction with HU use, consistent with the importance of oxygen supply and carriage for brain function. If delivery of the intervention can be improved, avoidance of oxygen desaturation with overnight respiratory support alongside HU use may play a role in improving cognition in SCD. DisclosuresNo relevant conflicts of interest to declare.

Continuous oximetry recordings on the first post-operative night after pediatric adenotonsillectomy-a case-control study

BackgroundChildren with obstructive sleep apnea (OSA) with recurrent dips in oxygen saturation (SpO2) during sleep are known to be at increased risk of post-operative airway compromise after adenotonsillectomy (AT). We aimed to determine the extent of desaturation on the first post-operative night in children known to have recurrent desaturation pre-operatively and to compare the extent of desaturation in that group with results in children known to have normal oximetry recordings pre-operatively. MethodsProspective sequential recruitment of 57 children who had overnight oximetry performed on the first night after adenotonsillectomy was undertaken, including 28 with a McGill Oximetry Score (MOS) of 2–4 pre-operatively (high risk group) and 29 with a normal/inconclusive pre-operative MOS (low risk group). Oximetry parameters (mean SpO2, SpO2 nadir, and rates of SpO2 dips below 90% and dips of ≥4%) were compared to the pre-operative oximetry result. Demographic and clinical factors, and the occurrence of post-operative complications, were derived from the medical record. ResultsIn the high risk group, the MOS improved in 23/28 children, but remained abnormal in 82%. Conversely, in the low risk group 26/29 (90%) had a normal post-operative oximetry. The remaining 3, all of whom had severe OSA on pre-operative polysomnography, had a lowered baseline SpO2 post-operatively. Mean SpO2 was slightly lower post-operatively in both groups. In the high risk group, all other SpO2 measures improved post-operatively. Respiratory adverse events were more common in the high risk group as expected (39% compared to 3% in the low risk group, p = 0.001). An adverse event requiring clinical intervention was significantly more likely if the post-operative oximetry was abnormal (result unknown to the treating team), occurring in 73% of children with an abnormal compared with 32% of children with a normal post-operative oximetry (p = 0.002). ConclusionMost children with an abnormal oximetry pre-operatively continued to have an abnormal oximetry on the first night after AT, albeit somewhat improved. While adverse events were more frequent in children with an abnormal post-operative oximetry, half (54%) did not suffer a clinical respiratory adverse event despite having repetitive desaturations on downloadable oximetry. These findings support close clinical observation of children at high risk of complications post-operatively, especially those with abnormal oximetry pre-operatively, rather than focusing on recurrent dips in SpO2 on post-operative oximetry downloads in the absence of clinically evident complications.

Saturation effect of atomic magnetic resonance

In this paper, we experimentally study the saturation effect of rubidium atomic magnetic resonance. A pump beam is applied to create atomic spin polarization, a radio frequency (RF) magnetic field is used to drive the spin precession about a static magnetic field, and an off-resonant linearly polarized probe beam is applied to detect the spin dynamics based on the Faraday-rotation effect. When the RF magnetic field intensity becomes strong, a saturation effect is observed. We measure the resonant peak under strong RF magnetic field driving and obtain a saturation dip as an indication of the saturation effect. Furthermore, we show that the line-width of the saturation dip is much smaller than that of magnetic resonance. Accordingly, the sensitivity of the precision measurement based on the saturation dip can be significantly improved. The relations between the saturation dip in the resonant peak and the driving RF magnetic field intensity, as well as pumping intensity, are also studied in our experiment.

Mid-infrared saturated absorption spectroscopy inside a hollow glass waveguide

We report the saturation spectroscopy of carbon dioxide inside a hollow glass waveguide (GW) using a tunable mid-infrared difference frequency generation (DFG) source. This DFG source was generated in a periodically poled lithium niobate crystal with a tuning range from 3.97 to 4.71μm. Saturated spectroscopy was performed on the R(60) transition of CO20001 ← 0000 band at 4.2μm inside a hollow GW of diameter 300μm and length 1 m. The saturation dip signal was found with a pump power as low as 0.18 mW inside the hollow GW. The linewidth of the dip was determined to be 4.40 MHz.

Observation of saturated absorption spectrum of 12C2H2 at 1536 nm in a 300 μm hollow glass waveguide

A system for saturated absorption spectroscopy is firstly built (to our knowledge) based on a gas-filled hollow glass waveguide with a core diameter of 300 μm. The performance of the system is demonstrated by observing the saturated absorption of the P(17) transition of the (ν1 +ν3) combination band of acetylene around 1536 nm using an erbium-doped fiber amplifier boosted external cavity diode laser. The saturated absorption spectrum is observed and the observed linewidth of the saturation dip varies from 10 to 20 MHz depending on the gas pressure and the optical launching condition into the GW. Its derivative spectrum is obtained using wavelength modulation spectroscopy and the third derivative signal is used as the error signal to lock the external cavity diode laser to the transition center. A frequency stability of ~60 kHz at 1 s integration time was achieved. Our study shows it is possible to build a mid-IR frequency reference using a large core gas-filled hollow GW.

Frequency measurements and self-broadening of sub-Doppler transitions in the + band of C2H2.

Frequency comb-referenced measurements of sub-Doppler laser saturation dip absorption lines in the + band of acetylene near 1.5 μm are reported. These measurements include transitions involving higher rotational levels than previously frequency measured in this band. The accuracy of the measured frequencies is typically better than 10 kHz. Measurements of the observed sub-Doppler line widths as a function of pressure showed that the self-pressure-broadening coefficients are about 3.5 times larger than those derived from conventional pressure broadening of unsaturated Doppler-limited spectra. This is attributed to the contribution of velocity-changing collisions to the total dephasing rate in the low pressure sub-Doppler measurements. At higher pressures, when the homogeneous broadening becomes comparable to the typical Doppler shift per elastic collision, the velocity changing collisions cease to contribute significantly to the incremental pressure broadening. A time-dependent soft collision model is developed to illustrate the transition between low and high pressure regimes of sub-Doppler pressure-broadening.

Feed-forward coherent link from a comb to a diode laser: Application to widely tunable cavity ring-down spectroscopy.

We apply a feed-forward frequency control scheme to establish a phase-coherent link from an optical frequency comb to a distributed feedback (DFB) diode laser: This allows us to exploit the full laser tuning range (up to 1 THz) with the linewidth and frequency accuracy of the comb modes. The approach relies on the combination of an RF single-sideband modulator (SSM) and of an electro-optical SSM, providing a correction bandwidth in excess of 10 MHz and a comb-referenced RF-driven agile tuning over several GHz. As a demonstration, we obtain a 0.3 THz cavity ring-down scan of the low-pressure methane absorption spectrum. The spectral resolution is 100 kHz, limited by the self-referenced comb, starting from a DFB diode linewidth of 3 MHz. To illustrate the spectral resolution, we obtain saturation dips for the 2ν3 R(6) methane multiplet at μbar pressure. Repeated measurements of the Lamb-dip positions provide a statistical uncertainty in the kHz range.

Sub-Doppler resolution near-infrared spectroscopy at 1.28 μm with the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy method.

We report on the sub-Doppler saturation spectroscopy of the nitrous oxide (N2O) overtone transition at 1.28μm. This measurement is performed by the noise-immune cavity-enhanced optical heterodyne molecular spectroscopy technique based on the quantum-dot (QD) laser. A high intra-cavity power, up to 10W, reaches the saturation limit of the overtone line using an optical cavity with a high finesse of 1.14(5)×105. At a pressure of several mTorr, the saturation dip is observed with a full width at half-maximum of about 2MHz and a signal-to-noise ratio of 71. To the best of our knowledge, this is the first saturation spectroscopy of molecular overtone transitions in the 1.3μm region. The QD laser is then locked to this dispersion signal with a stability of 15kHz at 1s integration time. We demonstrate the potential of the N2O as a marker because of its particularly rich spectrum at the vicinity of 1.28-1.30μm where there are several important forbidden transitions of atomic parity violation measurements and the 1.3μm O-band of optical communication.

Quadrupole splittings in the near-infrared spectrum of 14NH3.

Sub-Doppler, saturation dip, spectra of lines in the v1 + v3, v1 + 2v4, and v3 + 2v4 bands of 14NH3 have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening and show resolved or partially-resolved hyperfine splittings that are primarily determined by the 14N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar to the same rotational level in the ground state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.

Doppler-free spectroscopy on the Cs D1 line with a dual-frequency laser.

We report on Doppler-free laser spectroscopy in a Cs vapor cell using a dual-frequency laser system tuned on the Cs D1 line. Using counter-propagating beams with crossed linear polarizations, an original sign reversal of the usual saturated absorption dip and large increase in Doppler-free atomic absorption is observed. This phenomenon is explained by coherent population trapping (CPT) effects. The impact of laser intensity and light polarization on absorption profiles is reported in both single-frequency and dual-frequency regimes. In the latter, frequency stabilization of two diode lasers was performed, yielding a beat note fractional frequency stability at the level of 3×10-12 at 1 s averaging time. These performances are about an order of magnitude better than those obtained using a conventional single-frequency saturated absorption scheme.

Frequency-comb referenced spectroscopy of v4- and v5-excited hot bands in the 1.5 μm spectrum of C2H2

Doppler-free transition frequencies for v4- and v5-excited hot bands have been measured in the v1+v3 band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v1+v3 band itself, is between 3 and 22kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infrared absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100–7600cm−1 energy region.

G118(P) Weaning Home Oxygen Therapy in Infants with Chronic Lung Disease of Prematurity

BackgroundCurrently there are no evidence based guidelines to standardise the process of weaning home oxygen therapy in infants with chronic lung disease of prematurity (CLDP). Weaning decisions are based on...

Hyperfine structures in the v = 1–0 vibrational band of the [formula omitted] of N2

Hyperfine splittings were measured in selected rotational lines of the (1–0) vibrational band of the B∼3Πg-A∼3Σu+ transition of 14N2 in a low pressure discharge. Frequency modulated saturation dip spectroscopy produced hyperfine resolved, sub-Doppler lines with typical full-width at half-maximum line widths of 7MHz. Hyperfine transitions within 27 rotational lines in the R33, Q33, Q21, Q22, R11, and Q11 branches were recorded for J between 2 and 12, and fit with the same Hamiltonian used previously by Geisen, Neuschafer and Ottinger [Z. Phys. D 4, 263 (1987)]. The resulting parameters are (in MHz, with one standard deviation in parentheses): α=13.19(13), β=−12.36(18), e2q0Q=−1.19(25) for the (v″=0)A∼3Σu+ state; and K11=98.52(50), D11=13.09(59), D1−1=−44.11(16), G11=70.00(52), Q11=1.390(98) and Q1−1=1.65(11) for the (v′=1) B∼3Πg state.

Saturation spectroscopy of CO_2 and frequency stabilization of an optical parametric oscillator at 277 μm

We report the frequency stabilization of a CW single-frequency, singly resonant optical parametric oscillator (OPO) to the saturation absorption center of the (12)C(16)O2[10°1,02°1](II)>←00°0 P(14) line at 2.77 μm. The CO2 molecules were excited by the OPO idler wave, and the absorption signal was monitored through the fluorescence at 4.3 μm using a gold-coated longitudinal cell. The idler frequency was stabilized onto the line center by wavelength modulation method. The linewidth of the saturation dip was estimated to be 4.7 MHz, and the achieved frequency stability was 3.9 kHz (3.6×10(-11)).

At 68 years, unrecognised sleep apnoea is associated with elevated ambulatory blood pressure

After the age of 65 yrs the specific impact of unrecognised sleep-related breathing disorders (SRBD) on 24-h blood pressure (BP) levels remains under debate. We tested the cross-sectional relationship between the severity of obstructive sleep apnoea/hypopnoea (OSAH) and the increase of BP using ambulatory BP monitoring (ABPM) in the PROOF (PROgnostic indicator OF cardiovascular and cerebrovascular events study)-SYNAPSE (Autonomic Nervous System Activity, Aging and Sleep Apnea/Hypopnea study) cohort. 470 subjects (aged 68 yrs) neither treated for hypertension nor diagnosed for SRBD were included. All subjects underwent ABPM, and unattended at-home polygraphic studies. OSAH was defined by an apnoea/hypopnoea index (AHI) >15 · h(-1). The severity of the sleep apnoea was also quantified as the index of dips in oxyhaemoglobin saturation >3% (ODI). Results are expressed in per protocol analysis. Severe OSAH (AHI >30 · h(-1), 17% of subjects) was associated with a significant 5 mmHg increase in both diurnal and nocturnal systolic BP (SBP), and with a nocturnal 3 mmHg increase in diastolic BP (DBP). Systolic (mean SBP >135 mmHg) or diastolic (mean DBP >80 mmHg) hypertension were more frequently encountered in subjects suffering from moderate (AHI 15-30) or severe OSAH. After adjustment, the independent association between severe OSAH and 24-h systolic hypertension remained significant (OR 2.42, 95% CI 1.1-5.4). The relationship was further reinforced when SRBD severity was expressed using ODI >10 · h(-1). The impact of unrecognised SRBD on BP levels also exists at the age of 68 yrs. The hypoxaemic load appears to be the pathophysiological cornerstone for such a relationship.

Photocatalytic thin films containing TiO2:N nanopowders obtained by the layer-by-layer self-assembling method

In this work, TiO2–N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2–urea during 2, 4, 8, 12 and 24h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200nm at 24h milling time. UV–Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2–N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2–N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2–N nanoparticles were prepared by layer-by-layer self assembly method. UV–visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15min.

Precision Lamb-dip infrared spectra of the C–N stretching band of CH3NH2 with a CO2-laser/microwave-sideband spectrometer

We report saturation dip spectroscopy in the C-N stretching band of CH(3)NH(2) with a resolution of 0.4 MHz and an accuracy of 0.1 MHz by use of a CO(2)-laser/microwave-sideband spectrometer. The wide tunability, Lamb-dip resolution, absolute frequency accuracy, and high sensitivity of our dual-mode instrument were all key features in making precise measurements for a range of lines in the densely crowded spectrum with its complex pattern of splittings arising from the large-amplitude CH(3) torsion and NH(2) inversion. We focused on achieving resolution and assignment of transitions within the highly blended Q branch of the C-N stretch and on observations of the important K=0 sequences of Aa and Ea torsion-inversion symmetry. Term values of the latter were fitted to J(J+1) power-series expansions to obtain the K=0 C-N stretching effective B values and substate origins, from which calculated ground-state substate energies were subtracted to yield values of 1044.7061 and 1044.8011 cm(-1) for the Aa and Ea subband origins, respectively. We thereby estimate a mean value of 1044.75(5) cm(-1) for the vibrational band origin and 0.7323(5) cm(-1) for the effective upper-state B value for the C-N stretching fundamental of CH(3)NH(2).

Adenotonsillectomy for Sleep-Disordered Breathing in Children With Syndromic Craniosynostosis

Syndromic craniosynostosis (SCS) is known to be associated with sleep-disordered breathing (SDB) in childhood. Problems can occur at various levels, but midface hypoplasia is a major factor in affected infants.Adenotonsillectomy (AT) has been proven to be efficacious as a first-line treatment of SDB in healthy children. However, its role in the treatment of this issue in those with SCS has not been evaluated. Owing to the multiple possible levels of obstruction in such individuals, AT may have no benefit. This study therefore aimed to evaluate the effectiveness of AT in this group of patients.Twenty-six children with SCS with moderate to severe obstructive sleep apnea (OSA) were treated with AT. The mean age at surgery was 4.5 years (range, 1.6-13.9 y). Seven had severe OSA, 11 had moderate OSA, and 7 had mild OSA preoperatively. Of 25 children, 15 (60%) demonstrated an improvement in sleep severity scores postoperatively.Overall, there was a significant improvement in the mean number of saturation dips greater than 4%/h and in the mean nadir of dips in saturation after the operation. There was no significant difference in mean oxygen saturation, number of pulse rate rises per hour, or percentage time spent less than 90% SaO2.Clinically, there is thought to be some benefit in performing AT in these groups of patients. In children with SCS, in whom the cause of obstruction might be at multiple levels, AT should still to be considered as first-line treatment in the management of OSA/SDB.We acknowledge that some children may still go on to require further airway intervention. Further multicenter trials would be useful to examine more closely the significance of the effects of AT in children with craniofacial disorders experiencing SDB.