Hypoxic events and concomitant factors in preterm infants on non-invasive ventilation

Abstract

Automated control of inspired oxygen for newborn infants is an emerging technology, currently limited by reliance on a single input signal (oxygen saturation, SpO). This is while other signals that may herald the onset of hypoxic events or identify spurious hypoxia are not usually utilised. We wished to assess the frequency of apnoea, loss of circuit pressure and/or motion artefact in proximity to hypoxic events in preterm infants on non-invasive ventilation. Hypoxic events (SpO < 80 %) were identified using a previously acquired dataset obtained from preterm infants receiving non-invasive ventilation. Events with concomitant apnoea, loss of circuit pressure or oximetry motion artefact were annotated, and the frequency of each of these factors was determined. The effect of duration and timing of apnoea on the characteristics of the associated hypoxic events was studied. Among 1224 hypoxic events, 555 (45 %) were accompanied by apnoea, 31 (2.5 %) by loss of circuit pressure and 696 (57 %) by motion artefact, while for 224 (18 %) there were no concomitant factors identified. Respiratory pauses of longer duration (>15 s) preceding hypoxic events, were associated with a relatively slow decline in SpO and more prolonged hypoxia compared to shorter pauses. Hypoxic events are frequently accompanied by respiratory pauses and/or motion artefact. Real-time monitoring and input of respiratory waveform may thus improve the function of automated oxygen controllers, allowing pre-emptive responses to respiratory pauses. Furthermore, use of motion-resistant oximeters and plethysmographic waveform assessment procedures will help to optimise feedback control of inspired oxygen delivery.

Physiological instability after respiratory pauses in preterm infants

“…Indeed, given their numerical preponderance, short pauses (5‐9 seconds) were an important cause of physiological instability overall. The relative contribution of respiratory pauses to the overall occurrence of hypoxemia is similar to previous observations, although slightly lower (24% of episodes with SpO 2 < 80%, any duration; vs 40% of episodes with SpO 2 < 80% for ≥ 4 seconds), with discrepancies likely explained by differences in study population and hypoxemia definition. Unexplained episodes of physiological instability not associated with respiratory pause may be explained by obstructive respiratory events, CPAP pressure loss, and motion artefact, none of which could be reliably measured in this study.…”

“…Indeed, given their numerical preponderance, short pauses (5-9 seconds) were an important cause of physiological instability overall. The relative contribution of respiratory pauses to the overall occurrence of hypoxemia is similar to previous observations, 38 Several mechanisms can be invoked for hypoxemia following brief pauses in respiration, a phenomenon that has been noted previously in spontaneously breathing infants, 10,11 but not studied systematically in those on noninvasive support. Brief cessation of spontaneous respiration in preterm infants is often preceded by a period of hypoventilation, 10 and followed by a reduction in functional residual capacity 10,16 or a period of airway obstruction.…”

Apnea of prematurity (draft of clinical guidelines)

“…Недоношенным новорожденным с апноэ и при подозрении на апноэ рекомендуется проводить визуальный терапевтический осмотр для выявления клинических проявлений апноэ [2,3,24,25].…”