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Postnatal development of responses to airflow obstruction
R Harding1, A E Jakubowska, G J McCrabb
1Department of Physiology, Monash University, Melbourne, Victoria, Australia.
Insights
Upper airway obstruction may trigger Sudden Infant Death Syndrome (SIDS). Newborn lambs show impaired arousal responses to airway obstruction, suggesting increased vulnerability with age.
Area of Science:
- Neonatal physiology
- Respiratory control
- Sleep science
Background:
- Upper airway obstruction is a potential trigger for Sudden Infant Death Syndrome (SIDS).
- Effective physiological responses to airway obstruction are crucial for survival.
- Vulnerability in mounting these responses may increase SIDS risk.
Purpose of the Study:
- To investigate respiratory and arousal responses to upper airway obstruction in newborn lambs.
- To determine the influence of sleep state and postnatal age on these responses.
Main Methods:
- Newborn lambs were subjected to controlled upper airway obstruction (nasal obstruction, airflow obstruction via tubes or face masks).
- Physiological parameters including respiratory efforts, oxygen saturation, heart rate, and arousal were monitored.
- Responses were compared across different sleep states (REM vs. non-REM) and postnatal ages.
Main Results:
- Nasal obstruction in conscious lambs led to increased inspiratory efforts and oral airway formation, improving with age.
- In sleeping lambs, airflow obstruction caused hypoxemia, increased inspiratory efforts, bradycardia, and arousal, with earlier arousal in non-REM sleep.
- Arousal was more readily triggered by nasal tubes than face masks, suggesting mechanoreception's role.
- Lambs became less arousable in REM sleep with increasing postnatal age.
Conclusions:
- Newborn lambs exhibit age-dependent changes in arousal responses to airway obstruction.
- Increased vulnerability to airway obstruction may occur during the immediate newborn period, particularly in REM sleep.
- Mechanoreception plays a significant role in initiating arousal responses to airway obstruction.
Abstract:
1. Obstruction of the upper airway could be an initiating factor in the Sudden Infant Death Syndrome (SIDS). Responses to upper airway obstruction include augmentation of respiratory efforts, active dilation of the upper airway and electrocortical arousal. Vulnerable individuals may fail to mount these responses effectively. 2. Respiratory and arousal responses to obstruction of the upper airway have been investigated in newborn lambs. In conscious lambs, nasal obstruction causes a profound augmentation of inspiratory efforts, mild asphyxiation and eventual formation of an oral airway. The ability to establish an oral airway involves both chemoreception and mechanoreception and improves with age. 3. In sleeping lambs, obstruction of tidal airflow leads to progressive hypoxaemia, augmentation of inspiratory efforts, bradycardia and arousal. Arousal occurs earlier and with less hypoxaemia and bradycardia in non-REM sleep than in REM sleep. Arousal occurs after inspiratory efforts have increased to the same extent during both sleep states, suggesting that mechanoreception, or a sense of inspiratory effort, is important in initiating arousal. 4. Obstruction of nasal tubes tends to cause arousal from sleep earlier, and with less hypoxaemia and less augmentation of inspiratory effort, than when a more compliant face mask is obstructed. This supports the suggestion that mechanoreception, which may be involved in the perception of inspiratory effort, is a determinant of arousal. 5. With increasing postnatal age, lambs become less arousable in response to airflow obstruction when in REM sleep. This suggests that lambs may become progressively more vulnerable to the effects of airway obstruction during the immediate newborn period.(ABSTRACT TRUNCATED AT 250 WORDS)