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We have examined the behavior of several variables which are related to respiratory control in 114 infants (up to 6 months of age) in order to assess the risk for the sudden infant death syndrome (SIDS), 23 of the infants had already had demonstratable serious or life threatening apneas or respiratory problems during surgical anesthesia. These infants were assigned as a risk group, and the rest of the investigated babies was taken as a control group. We found that practically all infants of the risk group had apneas during sleep, which lasted longer than 8 s each. Only 22% of the infants of the control group had apneas of such a duration. As a statistical parameter, calculated from at least 1 hour recording of respiration, we defined the mean apnea duration (MA-value) as average value of apnea duration time in seconds per minute of recording. The MA-value proved to be significantly elevated in the infants of the risk group. The trend to hypoxia in the infants of the risk group was also indicated by the observation of lower transcutaneous PO2-values (tc-PO2) during sleep, when compared with control infants. In agreement with this observation is the increase of the 2,3-DPG concentration and the decrease of the density of erythrocytes of the infants of the risk group. Breathing hypoxic gas mixtures tended to depress respiration in all infants tested, and, especially in the risk group, to elicit irregular respiratory patterns. On the other hand, we observed that inhalation of pure oxygen markedly stimulated respiration in all infants investigated. We conclude from these observations that a risk for SIDS may be related to a particular response pattern of the respiratory center during the early postnatal life. We are able to distinguish infants with a higher risk for SIDS from other children by determination of the MA-value during sleep.

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Based on the results from semistructured interviews with parents of fifty SIDS victims and of fifty matched controls we developed a SIDS risk questionnaire, the so-called SRFB Graz. In a retrospective study this questionnaire was applied to 65 SIDS victims and 195 comparable controls. By statistical analysis a cut point was computed, which discriminates SIDS cases from controls with a sensitivity of 86% and a specificity of 95%.

Primary central alveolar hypoventilation (CAHV) is a rare disorder described in newborns, children, and adults. We report a 2 9/12 year old child with CAHV of unknown etiology. The evaluation of her ventilatory control system showed abnormalities awake and in the different sleep states. Hypoventilation was found to be more severe during non-REM sleep than during REM sleep and awake state. She had central apnea, an irregular respiratory rhythm in the non-REM sleep too, and diminished ventilatory response to inhaled 5%-6% CO2 in both REM and non-REM sleep. Her ventilation decreased when she was breathing 50% and 100% oxygen. During breathing 15% oxygen she did not arouse in spite a transcutaneous pO2 of 10 mmHg. She was first treated with mechanical ventilation during sleep and has now received bilateral simultaneous phrenic pacemaker support during quiet sleep for about one year. With the phrenic pacemaker she has normal minute volume and transcutaneous blood gases during sleep. During a respiratory infection she needed again mechanical ventilation via her tracheostoma 24 hours a day for one week. This case of a CAHV demonstrates a dysfunction of the central and partially also of the peripheral chemoreceptors. The abnormalities of the ventilation were demonstrable not only in the non-REM sleep but also in the REM sleep and awake state.