Video Abstract

Video Abstract

OBJECTIVES:

We evaluated the efficacy of adenotonsillectomy (T/A) in children with sleep-disordered breathing (SDB) in a controlled study using oximetry. We hypothesized that children with SDB and abnormal nocturnal oximetry in a community setting will have improved hypoxemia indices after T/A.

METHODS:

Children with snoring and tonsillar hypertrophy (4–10 years old) who were candidates for T/A were randomly assigned to 2 oximetry sequences (baseline and 3-month follow-up): (1) oximetry immediately before T/A and at the 3-month follow-up, which occurred postoperatively (T/A group); or (2) oximetry at the initial visit and at the end of the usual 3-month waiting period for surgery (control group). Outcomes were (1) proportion of subjects with McGill oximetry score (MOS) >1 at baseline acquiring MOS of 1 at follow-up and (2) proportion of subjects achieving oxygen desaturation (≥3%) of hemoglobin index (ODI3) <2 episodes per hour at follow-up if they had ODI3 ≥3.5 episodes per hour at baseline.

RESULTS:

One hundred and forty children had quality oximetry tracings. Twelve of 17 (70.6%) children with MOS >1 in the T/A group and 10 of 21 (47.6%) children with MOS >1 in the control group had MOS of 1 at follow-up (P = .14). More subjects in the T/A than in the control group achieved ODI3 <2 episodes per hour at follow-up (14 of 32 [43.8%] vs 2 of 38 [5.3%]; P < .001). Three children with elevated ODI3 were treated to prevent persistently abnormal ODI3 in 1 child at follow-up.

CONCLUSIONS:

An ODI3 ≥3.5 episodes per hour in nocturnal oximetry is related to increased resolution rate of nocturnal hypoxemia after T/A for SDB compared with no intervention.

What’s Known on This Subject:

Normalization of polysomnographic findings occurs in a larger proportion of children undergoing early adenotonsillectomy for sleep apnea than in a watchful waiting group.

What This Study Adds:

Three children with elevated oxygen desaturation (≥3%) of hemoglobin index (≥3.5 episodes per hour) were treated to prevent persistently abnormal desaturation index in 1 child at follow-up.

Increased upper airway resistance due to adenotonsillar hypertrophy represents the main pathogenetic mechanism of obstructive sleep-disordered breathing (SDB) in childhood, which is characterized by snoring, apneas, and difficulty breathing during sleep.1,2 Overnight polysomnography (sleep study) is the gold standard method for evaluating SDB severity and identifying children who will benefit from treatment.3 However, polysomnography is a labor-intensive diagnostic method, which is not available in many community settings. Thus, there is an urgent need for easy-to-use, low-cost diagnostic tools that can be applied to recognize children with snoring and adenotonsillar hypertrophy who will improve postadenotonsillectomy.

Obstructive sleep apneas and hypopneas (airflow cessation or reduction, respectively, associated with airway obstruction) are frequently accompanied by abrupt reductions in oxygen saturation of hemoglobin measured by pulse oximetry (Spo2), which occur in clusters corresponding to rapid eye movement and stage 2 sleep.4 The McGill oximetry score (MOS) has been devised to facilitate graphical interpretation of nocturnal oximetry recordings. An abnormal tracing incorporates at least 3 clusters of desaturation events and at least 3 Spo2 drops <90%, and it is assigned a hypoxemia severity score of 2, 3, or 4 depending on the depth of desaturations (mild, moderate, or severe hypoxemia).5,6 A tracing not fulfilling these criteria is given a score of 1 (normal or inconclusive). In the presence of SDB symptoms, an MOS >1 has >90% positive predictive value for obstructive apnea-hypopnea index (AHI) >5 episodes per hour in polysomnography.7 AHI describes the frequency of obstructive events per hour of sleep time and is the main measure used in clinical practice to express SDB severity.

Frequency of Spo2 drops per hour of sleep time (oxygen desaturation index) is another oximetry parameter that has been used to estimate SDB severity.8 In an uncontrolled study in which children with clinical features of SDB were evaluated by nocturnal oximetry before and after adenotonsillectomy (T/A), Saito et al9 have proposed that an oxygen desaturation (≥3%) of hemoglobin index (ODI3) ≥3.5 episodes per hour is likely to normalize (<2 episodes per hour) postoperatively. Nevertheless, the efficacy of T/A in otherwise healthy children with SDB related to pharyngeal lymphoid tissue hypertrophy has not been assessed in randomized, controlled trials by using oximetry. We have hypothesized that children with snoring, tonsillar hypertrophy, and certain abnormalities in nocturnal oximetry performed in a community setting will have improved hypoxemia indices after T/A.

Children eligible for participation in this prospective randomized controlled parallel-group study (Chania Community Oximetry-Based Study) (1) were 4 to 10 years old; (2) presented with at least a 6-month history of snoring >3 nights per week to the outpatient ear, nose, and throat (ENT) clinic of a regional hospital in Greece (Chania General Hospital, Chania, Crete); (3) had a tonsillar size >2+; and (4) were considered T/A candidates by an attending ENT surgeon (for exclusion criteria see Supplemental Information).10 

Waiting time for T/A at the Chania General Hospital is ∼3 months. Eligible children were recruited and randomly assigned to the following 2 different pairs of oximetry recordings (baseline and 3-month follow-up): (1) an oximetry immediately before T/A and at the 3-month follow-up, which occurred postoperatively (T/A group); or (2) an oximetry at the initial clinic visit and at the end of the usual 3-month waiting period for surgery (control group) (Fig 1). Thus, participants in both groups had baseline (0 month) and follow-up (3 months) oximetry and clinical evaluation.

FIGURE 1

Recruited children were randomly assigned to 1 of the following 2 oximetry sequences (baseline and 3-month follow-up): (1) an oximetry immediately before T/A and at the 3-month follow-up, which occurred postoperatively (T/A group); or (2) an oximetry at the initial clinic visit and at the end of the usual 3-month waiting period for surgery, before T/A (control group).

FIGURE 1

Recruited children were randomly assigned to 1 of the following 2 oximetry sequences (baseline and 3-month follow-up): (1) an oximetry immediately before T/A and at the 3-month follow-up, which occurred postoperatively (T/A group); or (2) an oximetry at the initial clinic visit and at the end of the usual 3-month waiting period for surgery, before T/A (control group).

After recruitment, simple randomization with a 1:1 allocation ratio was performed at the Chania General Hospital by opening sealed envelopes with computer-generated group assignment, which were provided by the coordinating center (University of Athens). The study protocol was approved by the Chania General Hospital Scientific Council (Proceeding 8,May 22, 2013). Written informed consent was obtained from caregivers, and assent was obtained from children 7 years of age or older.

Body weight and height were recorded at baseline and follow-up. Obesity was defined as BMI ≥95th percentile (z score ≥1.65).11,12 SDB-specific health-related quality of life was assessed by using the Obstructive Sleep Apnea-18 (OSA-18), an 18-item questionnaire, which was filled out by parents during both visits.13 Details about clinical evaluation are provided in the Supplemental Information.

Participants underwent continuous oximetry from 8 to 10 pm to 8 am in the ENT ward. To facilitate recognition of major motion artifacts, awakenings were recorded by the nurse and/or parent accompanying the child. A Nonin 7500 pulse oximeter was used with 8000AA sensor applied to 1 finger (Nonin Medical BV, Amsterdam, Netherlands). Nonin PureSAT technology uses an averaging time of <3 seconds and pulse-by-pulse filtering to remove signals caused by motion or low perfusion. Spo2 recording was downloaded by using the nVISION software (Nonin Medical BV).

Data with motion artifacts or corresponding to awakenings were excluded from tracings. Oximetry was considered technically acceptable if the recording had a duration ≥360 minutes and after removal of motion artifacts and/or awakenings was ≥300 minutes.14 Number of Spo2 drops ≥3% or ≥4% per hour of recording (ODI3 or oxygen desaturation [≥4%] of hemoglobin index [ODI4]), baseline Spo2 (average of Spo2 readings not included in any saturation drops), and Spo2 nadir were provided by the software. An MOS of 1 to 4 was assigned by visual inspection of the tracing (See Outcome Measures in Supplemental Information).6 For determining MOS, a cluster of desaturation events was defined as 5 or more Spo2 drops (≥4%) within 10 to 30 minutes.5 

The study was single-blind: (1) Oximetry was scored by 1 investigator at the coordinating center who was blinded to patient randomization status and order of the oximetry study (baseline versus follow-up); (2) investigators who administered the OSA-18 questionnaire were unaware of patient group assignment, and calculation of the total score was completed by a blinded investigator at the coordinating center; (3) data analysis was performed at the coordinating center. Families and patients were not blinded to the randomization assignment.

The primary outcome measures were (1) change in the proportion of subjects with an MOS of 1 (normal or inconclusive oximetry) between follow-up (3 months) and baseline (0 months) visits and (2) the proportion of subjects with oxygenation abnormalities at baseline who improved at follow-up (ie, proportion of subjects who achieved an MOS of 1 at 3 months if they had an MOS >1 at 0 months, and the proportion of subjects who achieved an ODI3 <2 episodes per hour at 3 months, if they had an ODI3 ≥3.5 episodes per hour at 0 months).

Changes in ODI4 and OSA-18 score between follow-up and baseline were secondary outcome measures ([value at follow-up]−[value at baseline]).13 Additional secondary outcomes unrelated to the current hypothesis have been included in the study protocol and will be presented in future publications (Supplemental Information).

Assuming a 20% rate of technically nonacceptable oximetry tracings and 20% rate of participants that would be lost at follow-up or discontinue their participation, the target sample size of 188 recruited subjects was calculated (Supplemental Information). Participants in the 2 study groups were compared regarding primary outcome measures by using the χ2 test. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were computed by logistic regression. Multivariable logistic regression analysis was applied to adjust ORs for the effects of baseline MOS or ODI3, age, sex, and presence of obesity. The number of children with elevated ODI3 that underwent T/A to prevent persistence of ODI3 ≥2 episodes per hour in 1 patient at follow-up was calculated (number needed to treat).

The 2 groups were compared in terms of ODI4 change by Mann–Whitney U test and regarding OSA-18 score change by Student’s t test. The relationship between study group and change in OSA-18 score was adjusted for other factors by using a general linear model that incorporated age, sex, and presence of obesity as covariates. The interaction between SDB severity and group assignment regarding the effect on OSA-18 change was also tested.

Between June 2013 and April 2016, families of 196 eligible children were approached for recruitment to the study. Of those, 93 subjects were randomly assigned to the T/A group and 93 to the control group (Fig 2). Follow-up evaluation of the last participant was completed in August 2016. None of the participants in the control group required T/A on an urgent basis while on the surgical waiting list, and there were no major adverse events.

FIGURE 2

Study enrollment and participants’ randomization.

FIGURE 2

Study enrollment and participants’ randomization.

The frequency of technically nonacceptable oximetry at baseline or follow-up was 22.6% in the T/A group and 15.1% in the control group. The reason of nonacceptable oximetry was no sensor contact or poor contact with the child’s finger. A total of 4.3% of children randomly assigned to the T/A group and 7.5% of those assigned to the control group did not undergo follow-up oximetry because they did not return for evaluation (Fig 2).

A total of 140 children (68 in the T/A group and 72 in the control group) had technically acceptable oximetry tracings both at baseline and at follow-up and were included in the primary outcome measures analysis. The 2 study groups were similar in demographic characteristics, tonsillar size, somatometrics, OSA-18 scores, and oximetry indices (Tables 1 and 2).

TABLE 1

Baseline Characteristics of Children in the 2 Study Groups With Technically Acceptable Baseline and Follow-up Nocturnal Oximetry Tracings

VariablesT/A Group, n = 68Control Group, n = 72
Age, y 5.9 ± 1.6 6 ± 1.6 
Sex, female (%) 33 (48.5) 34 (47.2) 
Tonsillar size   
 3+ (%) 61 (89.7) 65 (90.3) 
 4+ (%) 7 (10.3) 7 (9.7) 
 BMI z score 0.3 ± 1.4 0.2 ± 1.6 
Wt status (%)   
 Obese 12 (17.6) 14 (19.4) 
 Overweight or obese 25 (36.8) 28 (38.9) 
 Failure to thrive 6 (8.8) 12 (16.7) 
OSA-18 total score 59.4 ± 16.3 58.3 ± 15.7 
VariablesT/A Group, n = 68Control Group, n = 72
Age, y 5.9 ± 1.6 6 ± 1.6 
Sex, female (%) 33 (48.5) 34 (47.2) 
Tonsillar size   
 3+ (%) 61 (89.7) 65 (90.3) 
 4+ (%) 7 (10.3) 7 (9.7) 
 BMI z score 0.3 ± 1.4 0.2 ± 1.6 
Wt status (%)   
 Obese 12 (17.6) 14 (19.4) 
 Overweight or obese 25 (36.8) 28 (38.9) 
 Failure to thrive 6 (8.8) 12 (16.7) 
OSA-18 total score 59.4 ± 16.3 58.3 ± 15.7 

Continuous variables are expressed as mean ± SD. Obesity has been defined as BMI (wt in kilograms divided by the square of the height in meters) in the 95th percentile or higher (z score ≥1.65), overweight status or obesity as BMI in the 85th percentile or higher (z score ≥1.04), and failure to thrive as a BMI in less than the fifth percentile (z score <−1.65).

TABLE 2

Baseline Oximetry Findings of Children in the 2 Study Groups With Technically Acceptable Baseline and Follow-up Nocturnal Oximetry Tracings

VariablesT/A Group, n = 68Control Group, n = 72
Recording time, min 494 (449, 551) 501 (455, 545) 
Analyzed time, min 380 (350, 444) 431 (365, 472) 
Baseline Spo2, % 98 (97.2, 98.4) 97.5 (96.5, 98.2) 
ODI3, episodes per h 3.4 (1, 5.7) 4.1 (1.5, 9.3) 
ODI4, episodes per h 1.4 (0.3, 2.7) 1.8 (0.6, 4.7) 
Subjects with an MOS >1 (%) 17 (25) 21 (29.2) 
 MOS = 2 (%) 12 (17.6) 11 (15.3) 
 MOS = 3 (%) 4 (5.9) 8 (11.1) 
 MOS = 4 (%) 1 (1.5) 2 (2.8) 
Subjects with ODI3 ≥3.5 episodes per h (%) 32 (47.1) 38 (52.8) 
Subjects with MOS >1 and ODI3 ≥3.5 episodes per h (%) 17 (25) 21 (29.2) 
% analyzed recording time with   
 Spo2 <95% 2 (0.2, 5.4) 2.3 (0.6, 8.3) 
 Spo2 <90% 0.1 (0, 1) 0.1 (0, 0.8) 
 Spo2 <85% 0 (0, 0) 0 (0, 0.1) 
Spo2 nadir, % 88 (84.3, 91.8) 89 (83.3, 91) 
VariablesT/A Group, n = 68Control Group, n = 72
Recording time, min 494 (449, 551) 501 (455, 545) 
Analyzed time, min 380 (350, 444) 431 (365, 472) 
Baseline Spo2, % 98 (97.2, 98.4) 97.5 (96.5, 98.2) 
ODI3, episodes per h 3.4 (1, 5.7) 4.1 (1.5, 9.3) 
ODI4, episodes per h 1.4 (0.3, 2.7) 1.8 (0.6, 4.7) 
Subjects with an MOS >1 (%) 17 (25) 21 (29.2) 
 MOS = 2 (%) 12 (17.6) 11 (15.3) 
 MOS = 3 (%) 4 (5.9) 8 (11.1) 
 MOS = 4 (%) 1 (1.5) 2 (2.8) 
Subjects with ODI3 ≥3.5 episodes per h (%) 32 (47.1) 38 (52.8) 
Subjects with MOS >1 and ODI3 ≥3.5 episodes per h (%) 17 (25) 21 (29.2) 
% analyzed recording time with   
 Spo2 <95% 2 (0.2, 5.4) 2.3 (0.6, 8.3) 
 Spo2 <90% 0.1 (0, 1) 0.1 (0, 0.8) 
 Spo2 <85% 0 (0, 0) 0 (0, 0.1) 
Spo2 nadir, % 88 (84.3, 91.8) 89 (83.3, 91) 

Continuous variables are expressed as mean ± SD or as median (quartile 25, quartile 75).

Children randomly assigned to the T/A group with technically acceptable baseline oximetry who completed (n = 68) or who did not complete (n = 14) the study did not differ significantly in the frequency of an MOS of 1 or proportion of subjects with ODI3 ≥3.5 episodes per hour. Similarly, there were no significant differences regarding oxygenation indices between children in the control group with acceptable baseline oximetry who completed (n = 72) or did not complete (n = 14) the study.

The T/A and control groups were not different regarding change in the proportion of subjects with an MOS of 1 between the follow-up and baseline visits (P = .54; Table 3). OR (95% CI) for achieving an MOS of 1 at follow-up in the T/A relative to the control group was 1.3 (0.5–3.3). The absence of an association persisted after adjustment for baseline MOS, age, sex, and presence of obesity (Supplemental Table 5).

TABLE 3

Change in the Proportion of Subjects With an MOS of 1 in the T/A and Control Groups Between Follow-up and Baseline Along With Statistical Comparison

OutcomeT/A Group, n = 68Control Group, n = 72P
0 mo3 moChange Between 3 and 0 mo0 mo3 moChange Between 3 and 0 mo
MOS of 1, n (%) 51 of 68 (75) 63 of 68 (92.6) +12 of 68 (+17.6) 51 of 72 (70.8) 61 of 72 (84.7) +10 of 72 (+13.9) .54 
OutcomeT/A Group, n = 68Control Group, n = 72P
0 mo3 moChange Between 3 and 0 mo0 mo3 moChange Between 3 and 0 mo
MOS of 1, n (%) 51 of 68 (75) 63 of 68 (92.6) +12 of 68 (+17.6) 51 of 72 (70.8) 61 of 72 (84.7) +10 of 72 (+13.9) .54 

Changes in the MOS between follow-up and baseline visits according to study group are presented in Supplemental Tables 6 and 7. Over the 3-month study period, 12 of 17 (70.6%) children with an MOS >1 in the T/A group and 10 of 21 (47.6%) children with an MOS >1 in the control group achieved an MOS of 1 at follow-up (P = .14; OR 2.6 [0.7–10.2]; adjusted OR 2.5 [0.6–10.7]) (Supplemental Table 8).

Individual changes in ODI3 for all subjects in the 2 groups are shown in Fig 3 (details in Supplemental Fig 5). The median (quartile 25, quartile 75) ODI3 change between follow-up and baseline was −3.2 (−6.5, −1.7) episodes per hour in the T/A group and −1.7 (−5.7, 0.9) episodes per hour in the control group.

FIGURE 3

ODI3 changes between baseline (visit 1) and follow-up (visit 2) for individual subjects in the 2 study groups along with summary boxplots. The cutoff value of 3.5 episodes per hour above which ODI3 at baseline is responsive to T/A is marked by the red line. The upper and lower boundary of each boxplot indicate the 25th and 75th percentile values, and the heavy black line within each boxplot corresponds to the median value; the upper and lower whiskers are the largest and smallest observed values that are not outliers, whereas the round, open symbols and asterisks indicate outliers and extreme values, respectively. ODI3 changes in larger scale for children with baseline ODI3 <10 episodes per hour are presented in Supplemental Fig 5.

FIGURE 3

ODI3 changes between baseline (visit 1) and follow-up (visit 2) for individual subjects in the 2 study groups along with summary boxplots. The cutoff value of 3.5 episodes per hour above which ODI3 at baseline is responsive to T/A is marked by the red line. The upper and lower boundary of each boxplot indicate the 25th and 75th percentile values, and the heavy black line within each boxplot corresponds to the median value; the upper and lower whiskers are the largest and smallest observed values that are not outliers, whereas the round, open symbols and asterisks indicate outliers and extreme values, respectively. ODI3 changes in larger scale for children with baseline ODI3 <10 episodes per hour are presented in Supplemental Fig 5.

Thirty-two of 68 participants in the T/A group and 38 of 72 subjects in the control group had ODI3 ≥3.5 episodes per hour at baseline. Children with elevated ODI3 in the 2 groups did not differ in baseline characteristics (Supplemental Table 9). Significantly more children in the T/A group than in the control group with an elevated ODI3 at baseline had an ODI3 <2 episodes per hour at follow-up (OR 14.0 [95% CI 2.9 to 68.4]; P < .001; Table 4). Subjects in the T/A group were significantly more likely to normalize their ODI3 at follow-up after considering ODI3 at baseline, age, sex, and presence of obesity (P < .01; Supplemental Table 10). Three children with elevated ODI3 underwent T/A to prevent an ODI3 ≥2 episodes per hour in 1 child at the 3-month follow-up. Comparisons of the 2 study groups regarding changes in ODI4 between follow-up and baseline are presented in the Supplemental Information.

TABLE 4

Proportion of Subjects Who Achieved an ODI3 of <2 Episodes per Hour at 3 Months (Follow-up), if They Had a Desaturation Index of ≥3.5 Episodes per Hour at 0 Month (Baseline) and Statistical Comparison Between the 2 Study Groups

T/A GroupControl GroupP
Patients with ODI3 ≥3.5 episodes per h at 0 mo, n 32 38 — 
Patients who achieved ODI3 <2 episodes per h at 3 mo (%) 14 (43.8) 2 (5.3) <.001 
T/A GroupControl GroupP
Patients with ODI3 ≥3.5 episodes per h at 0 mo, n 32 38 — 
Patients who achieved ODI3 <2 episodes per h at 3 mo (%) 14 (43.8) 2 (5.3) <.001 

—, not applicable.

Children in the T/A group had significantly larger improvement in OSA-18 total score between 3 and 0 months than participants in the control group (−32.4 ± 16.9 vs −0.8 ± 9.1; P < .001; Fig 4). The association between study group and change in the OSA-18 score remained significant after adjustment for age, sex, and presence of obesity (P < .01; Supplemental Table 11). There was no interaction between SDB severity (MOS >1 versus MOS of 1 or ODI3 ≥3.5 episodes per hour versus ODI3 <3.5 episodes per hour) and treatment group regarding change in OSA-18 (P = .68 and P = .20, respectively).

FIGURE 4

OSA-18 changes (SDB-specific, health-related quality of life score) between baseline (visit 1) and follow-up (visit 2) evaluations for individual subjects in the 2 study groups along with group statistics. Children in the T/A group had significantly larger improvement in an OSA-18 total score between 3 and 0 months (visit 2 and visit 1, respectively) than participants in the control group (P < .001). The round symbols indicate mean values, whereas the upper and lower bars depict the mean (+2 SDs) and mean (−2 SDs) values, respectively.

FIGURE 4

OSA-18 changes (SDB-specific, health-related quality of life score) between baseline (visit 1) and follow-up (visit 2) evaluations for individual subjects in the 2 study groups along with group statistics. Children in the T/A group had significantly larger improvement in an OSA-18 total score between 3 and 0 months (visit 2 and visit 1, respectively) than participants in the control group (P < .001). The round symbols indicate mean values, whereas the upper and lower bars depict the mean (+2 SDs) and mean (−2 SDs) values, respectively.

The present randomized controlled study is the first to reveal that ODI3 from nocturnal oximetry performed in a community setting can be used to identify otherwise healthy children with snoring and tonsillar hypertrophy who are likely to have resolution of hypoxemia related to SDB after T/A. A preoperative ODI3 ≥3.5 episodes per hour was associated with attainment of normal ODI3 in ∼40% of patients, postoperatively. In contrast, an MOS >1 was not responsive to T/A, because the frequency of a normal and/or inconclusive score (MOS = 1) increased similarly in both the T/A and control groups at the end of the follow-up period. Disease-specific, health-related quality of life improved significantly more in the T/A than in the control group.

Preoperative objective assessment of SDB severity is important.3 Moderate-to-severe SDB (ie, AHI >5 episodes per hour) diagnosed by polysomnography in the presence of adenotonsillar hypertrophy is an indication for T/A.3 This recommendation is supported by results of the Childhood Adenotonsillectomy Trial (CHAT), in which the efficacy of T/A has been assessed by polysomnography.15 For every 3 children with AHI >4.7 episodes per hour undergoing surgery, persistence of abnormal AHI was prevented in 1 child, whereas frequency of SDB resolution without treatment was only 26%.15,16 Because of the high spontaneous resolution frequency of mild SDB (AHI: 2–5 episodes per hour), 5 children with mild disease underwent T/A to prevent persistence of abnormal AHI in 1 child.

Additionally, prevalence of major respiratory complications in the post-T/A period increases with severity of SDB as measured by polysomnography.17 Because the availability of polysomnography is limited and more so in community settings, it has been suggested that children at risk for SDB should be offered at least 1 of the alternative diagnostic methods.3 Nocturnal oximetry is such an economical substitute. An MOS of 1 is associated with low risk of major respiratory complications postoperatively, whereas an MOS of 4 predicts high risk of complications requiring airway intervention, which can be reduced by limiting the total dose of administered opioids for pain.18,19 

The response of abnormal oximetry parameters to T/A has not been defined.20,21 In healthy 4- to 10-year-old children, the 90th and 97.7th percentile values for ODI3 are 1.2 and 2.04 episodes per hour, respectively.9,22 Saito et al9 have proposed that an ODI3 cutoff value of 3.5 episodes per hour, which corresponds to 2 SDs above the 97.7th percentile or 4 SDs above the mean ODI3 value in asymptomatic children, allows the detection of SDB-related hypoxemia, which is responsive to T/A. In the current study, 3 children with ODI3 ≥3.5 episodes per hour had surgery to prevent the persistence of abnormal ODI3 (≥2 episodes per hour) in 1 child postoperatively, a surgical success rate similar to that reported for patients with moderate-to-severe SDB (AHI >4.7 episodes per hour) in the CHAT.15 Hence, when oximetry is used as a diagnostic tool, an ODI3 ≥3.5 episodes per hour defines a subgroup of patients with SDB who respond to T/A as favorably as those with an AHI >5 episodes per hour.

In this study, MOS was not responsive to T/A. Although an MOS >1 predicts AHI >5 episodes per hour in >90% of cases, one-third of children with clinical suspicion of SDB and an MOS of 1 also have an AHI >5 episodes per hour.7 Similarly to an ODI3 ≥3.5 episodes per hour, an MOS of 1 can also be abnormal because it frequently incorporates oximetry tracings revealing hypoxemia (eg, those with only 2 clusters of desaturation events or fewer than 3 Spo2 drops <90%).5,6 In a study by Nixon et al,6 an MOS of 1 corresponded to a mean AHI of 4.1 episodes per hour and was characterized as a “normal/inconclusive” score for excluding SDB. Misclassification of SDB severity when using MOS probably explains why the 2 study groups did not differ in the frequency of achieving a normal or inconclusive score. In summary, an ODI3 ≥3.5 episodes per hour can be used to recognize cases of SDB with hypoxemia responsive to T/A, whereas an MOS >1 identifies those children who should be monitored in the hospital overnight post-T/A.18 

Health-related quality of life as measured by an OSA-18 score was similar in both participants of the CHAT and of the current study and was affected in a mild-to-moderate degree.23 In both studies, improvement in quality of life was not predicted by preoperative SDB severity.24 The improvement in OSA-18 contrasts with the response of polysomnography indices to T/A, which may remain abnormal in an appreciable proportion of children postoperatively.25 Therefore, impaired quality of life is an indication for treatment regardless of the severity of nocturnal hypoxemia.3 

The usual waiting time for T/A at Chania General Hospital is ∼3 months, and surgery has not been delayed for the purposes of this study. T/A has been the preferred treatment of SDB in all participants because tonsillectomy alone may not suffice because of residual adenoid tissue increasing upper airway resistance.26 Participants did not have a trial of nasal corticosteroid before proceeding to surgery because no improvement in SDB related to tonsillar hypertrophy was expected.27 

A study limitation is the appreciable frequency of technically nonacceptable oximetry tracings, which could decrease by using disposable (adhesive) sensors rather than reusable finger clips for cost reduction. Another limitation is that oximetry has been conducted in hospital, but the same evaluation could be completed at the patient’s home. Although the analysis based on ODI3 ≥3.5 episodes per hour was performed in subsets of the T/A and control groups, subjects of the former group were significantly more likely to normalize their ODI3 at follow-up even after adjustment for factors potentially affecting efficacy of T/A.

The use of a control group minimized improvement in abnormal ODI3 or MOS because of the “regression toward the mean” phenomenon. Improvement in the outcome measures in the control group provides an estimate of changes attributed to regression toward the mean and to placebo effect. Of note, this study was not designed to recognize subgroups of patients at risk for residual nocturnal hypoxemia post-T/A who would require repeat oximetry.

The present randomized controlled study reveals that nocturnal oximetry can be used in community settings to identify children with snoring and tonsillar hypertrophy who are likely to have resolution of nocturnal intermittent hypoxemia after undergoing T/A. An ODI3 that is not elevated does not necessarily exclude the need for treatment because impaired quality of life improves post-T/A regardless of the severity of nocturnal hypoxemia and obstructive apneas or hypopneas are not always accompanied by Spo2 drops.

     
  • AHI

    apnea-hypopnea index

  •  
  • CHAT

    Childhood Adenotonsillectomy Trial

  •  
  • CI

    confidence interval

  •  
  • ENT

    ear, nose, and throat

  •  
  • MOS

    McGill oximetry score

  •  
  • ODI3

    oxygen desaturation (≥3%) of hemoglobin index

  •  
  • ODI4

    oxygen desaturation (≥4%) of hemoglobin index

  •  
  • OR

    odds ratio

  •  
  • OSA-18

    Obstructive Sleep Apnea-18

  •  
  • SDB

    sleep-disordered breathing

  •  
  • SpO2

    oxygen saturation of hemoglobin measured by pulse oximetry

  •  
  • T/A

    adenotonsillectomy

Dr Papadakis participated in the preparation of the research proposal and data collection and analysis and contributed to preparation of the initial draft of the manuscript; Dr Chaidas reviewed the research proposal, contributed to oximetry scoring, and critically reviewed and revised the manuscript; Drs Chimona, Asimakopoulou, Ladias, and Proimos reviewed the research proposal, participated in clinical evaluation of participants, contributed to data analysis and interpretation, and critically reviewed and revised the manuscript; Dr Miligkos contributed to preparation of the initial research proposal, data analysis and interpretation, and critically reviewed and revised the manuscript; Dr Kaditis conceptualized and designed the study, prepared the research proposal, contributed to data analysis and interpretation, and drafted the initial and final manuscript; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

This trial has been registered at www.clinicaltrials.gov (identifier NCT01918007).

FUNDING: No external funding.

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

Supplementary data