3. Some (useful) Definitions:
1. Apnea:
i. Definition:
cessation of respiratory airflow with a duration longer than 10 seconds.
Considered abnormal ('pathologic') if duration is longer than 20 seconds (15 to 20 seconds considered 'borderline).
Apnea of any duration associated with oxygen desaturation, bradycardia, cyanosis, pallor, or hypotonia is pathologic.
ii. Classification:
- Central: episodes of cessation of respiratory airflow with absence of respiratory effort
- Obstructive: episodes of cessation of respiratory airflow in presence of a respiratory effort (which can be stronger than that seen before the occurrence of the apnea).
- Mixed: presence of both components, one follows the other if occurring in the same episode.
2. Periodic Breathing:
i. Definition:
'Cheyne-Stokes' respiration. 3 or more respiratory airflow pauses of 3 seconds or greater duration with less than 20 seconds of normal respiration between pauses.
ii. Classification:
- Normal: Brief periods of periodic breathing are normally seen during neonatal period. However, when present, only a small fraction of the day is spent on periodic breathing.
- Pathological: Age dependent norms depending on fraction of time spent on periodic breathing.
| Age (weeks) | Term Infants | Preterm Infants |
| 0 - 4 | 0 - 3.5 % | 0 - 5 % |
| 4 - 8 | 0 - 2.5 % | 0 - 3.5 % |
| 8 - 20 | 0 - 1.5 % | 0 - 2.5 % |
| > 20 | 0 - 1.0 % | 0 - 1.5 % |
Premature infants younger than 36 weeks of post-conceptual age can normally spend up to 15% of the time on periodic breathing.
iii. In older children and adults periodic breathing is seen associated with CHF or with brainstem pathology.
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Index Normal Physiology Development of Respiratory Control Definitions Specific Disorders Readings