Nocturnal hypoxemia in infants with or without upper airway obstruction and its association with nocturnal pulse rate.

Objective: Nocturnal intermittent hypoxemia may enhance sympathetic nervous system activity. We aimed to assess the potential relationship of age-adjusted nocturnal pulse rate (% distance from 95th percentile for age-pulse rate index) with nocturnal oximetry parameters and their interaction with upper airway obstruction (UAO) presence.

Methods: Nocturnal oximetry data of 1-12-month-old infants without UAO/lung disease who were hospitalized for common pediatric problems (e.g. urinary tract infection) and of infants with clinically apparent UAO were analyzed. General linear models were applied to evaluate associations of nocturnal pulse rate index with group (infants with vs. without UAO) or nocturnal hypoxemia severity (oxygen desaturation [≥3 %] index for events lasting ≥2s, ≥5s, ≥10s or ≥20s (ODI3-2s, ODI3-5s, ODI3-10s or ODI3-20s, respectively).

Results: Oximetry data of 158 infants without UAO (age 1-12.7 months) and 23 with UAO (age 1-11.1 months) were analyzed. There were no significant associations of pulse rate index with group or ODI3 (P > .05). However, significant interactions were identified between ODI3-10s or ODI3-20s and group: in infants with UAO, pulse rate increased with raising ODI3-10s or ODI3-20s compared to participants without UAO (beta .612 [95 %CI .083-1.140; P = .023 and 1.140 [.145-2.134]; P = .025, respectively). For every 10 episodes/h increase in ODI3-20s among infants with UAO, average pulse rate approached or exceeded the 95th percentile for age by 11.4 % compared to infants without UAO.

Conclusions: Despite overlap of desaturation indices values in infants without UAO and those with UAO, only in the latter, frequency of intermittent hypoxemia predicts an enhanced heart rate response.