Mandibular movements identify respiratory effort in pediatric obstructive sleep apnea

Abstract

Study objectives: Obstructive sleep apnea-hypopnea (OAH) diagnosis in children is based on the quantification of flow and respiratory effort (RE). Pulse transit time (PTT) is one validated tool to recognize RE. Pattern analysis of mandibular movements (MM) might be an alternative method to detect RE. We compared several patterns of MM to concomittant changes in PTT during OAH in children with adenotonsillar hypertrophy.

Participants: 33 consecutive children with snoring and symptoms/signs of OAH.

Measurements: MMs were measured during polysomnography with a magnetometer device (Brizzy Nomics, Liege, Belgium) placed on the chin and forehead. Patterns of MM were evaluated representing peak to peak fluctuations > 0.3 mm in mandibular excursion (MML), mandibular opening (MMO), and sharp MM (MMS), which closed the mouth on cortical arousal (CAr).

Results: The median (95% CI) hourly rate of at least 1 MM (MML, or MMO, or MMS) was 18.1 (13.2-36.3) and strongly correlated with OAHI (p = 0.003) but not with central apnea-hypopnea index (CAHI; p = 0.292). The durations when the MM amplitude was > 0.4 mm and PTT > 15 ms were strongly correlated (p < 0.001). The mean (SD) of MM peak to peak amplitude was larger during OAH than CAH (0.9 ± 0.7 mm and 0.2 ± 0.3 mm; p < 0.001, respectively). MMS at the termination of OAH had larger amplitude compared to MMS with CAH (1.5 ± 0.9 mm and 0.5 ± 0.7 mm, respectively, p < 0.001).

Conclusions: MM > 0.4 mm occurred frequently during periods of OAH and were frequently terminated by MMS corresponding to mouth closure on CAr. The MM findings strongly correlated with changes in PTT. MM analysis could be a simple and accurate promising tool for RE characterization and optimization of OAH diagnosis in children.

Keywords: mandibular movements; pediatric obstructive sleep apnea; pulse transit time; respiratory effort.

Figure 1. A midsagittal mandibular movement magnetic sensor (Brizzy Nomics, Liege, Belgium) measured the distance in mm between two parallel, coupled, resonant circuits placed on the forehead and on the chin.

Figure 2. Schematic representation of the mandibular movements.

MML, peak to peak respiratory MM ≥ 0.3 mm; MMO, mouth opening; MMS, sharp and sudden MM.

Figure 3A. Polysomnographic tracing of 4-min of stage N2 sleep, in a 12-year-old child with tonsillar hypertrophy, showing regular episodes of obstructive apnea-hypopnea.

When sampling the PTT signal at the same frequency as the MM signal and after adjustment for the lag of these signals, MM was highly correlated with PTT (Pearson r = 0.65; p < 0.001) in this patient; the more the mandible lowered during MMO, the more PTT lengthened. Cortical arousals are enclosed into the small brown symbols. On the right is a tracing during a quiescent period of normal respiration and little mandibular movement. SaO2, arterial oxyhemoglobin saturation; VTH and VAB; thoracic and abdominal inductance belts; NAF2P and NAF1, nasal pressure transducer and oronasal thermal flow sensor; MM, mandibular movements; PTT, pulse transit time; Phono, microphone sound; HR, heart rate; OAH, obstructive sleep apnea-hypopnea; MMS: sharp and sudden MM; MMC: peak to peak respiratory MM ≥ 0.3 mm; MMO: mouth opening.

Figure 3B. Magnified traces of a single OAH event.

The abbreviations are the same as described in Figure 3A.

Figure 4. Box and whisker plots of the mean envelop of mandibular movements during the last 10 seconds periods of AH and on the subsequent arousals from 214 randomly selected obstructive and 214 identified central apneic events.

The horizontal dotted lines show a threshold of 0.3 mm for the peak to peak mandibular movement's amplitude changes that defines a MML; the box height is the interquartile range (25%–75%); the solid line in each box corresponds to the median; the whiskers represent the 5 and 95% percentiles. *The p values indicate the statistical difference between OAH and CAH events during the last ten seconds of apnea-hypopnea periods and on arousal. OAH, obstructive sleep apnea-hypopnea; CAH, central sleep apnea-hypopnea; AH, apnea-hypopnea.

Figure 5. Relationship between the period of NREM sleep times (minutes) during which PTT changes from one cardiac beat to the other and mandibular movement's peak to peak amplitudes are, respectively, > 15 msec and 0.4 mm in 33 children (r = 0.86 p < 0.001).