Respiration in human beings is dependent on multiple factors, mainly adjusted to changing oxygen demands. Other sources of variation, such as the emotional state can also interfere with the control of the blood gas composition. In addition, pathological variations also exist. Between them, the sleep respiratory disturbances constitute an important concern in sleep medicine, particularly the adult’s sleep apnoeas as well as those shown by premature infants. A common link between adult and infant apnoeas could exist. In infants, apnoeas seem to be due to immaturity of respiratory control while in adults a neurological problem, for instance brain stroke, could impair the respiratory control in a way similar to that of the immature newborn. Instances of such regressions are not uncommon after degenerative processes. This report deals with the analysis of the respiratory responses of lizards (Gallotia galloti) in response to various states and with comparing these responses to those of the immature newborn and those shown in adult central apnoeas.

Twenty animals were implanted with electrodes for recording EEG, ECG and breathing under I.P. barbiturate anaesthesia. After surgery recovery, continuous recordings were performed for at least 48 h. The results were stored in a computer. Linear (amplitude, coherence and FFT) analysis techniques have been used to recognize interacctions between ECG and respiration. In addition, behavioral observation and EEG analysis has been used to determine behavioral states. The analysis has been performed at a body temperature of 20, 25, 30 and 35 °C. The experiments were performed under approval of the local ethics committee for animal experimentation.

Normal lizards showed an important degree of variability depending on (1) emotional state, (2) body temperature and (3) sleep-waking state. Excited animals showed important respiratory changes, in respiratory frequency (four times higher), in pattern (polyphasic movements in front of monophasic ones), in amplitude (about 250 % higher) but also showed dramatic apnoeic pauses of up to 200 s. With respect to temperature, the respiratory frecuency was approximately doubled from 20 to 35 °C, irrespective of the behavioural state. Finally, the breathing was regular during waking but the sleep reduced both its amplitude and frequency to 50 % of the waking value. In addition, important apnoeic pauses were recorded, lasting for up to 250 s. As an example, at the preferred temperature (30°C) sleeping animals made 14 ± 5 breaths every 40 s, waking animals 20 ± 4 and excited animals 78 ± 22 (means ± S.E.M.).

Interpreting these results using Haeckel’s biogenetic law (ontogeny repeats phylogeny), it can be concluded that the central sleep apnoeas observed both in the immature and in the adult human beings can be considered as phylogenetic regressions.

This study was supported by FIS grant 00/0022-01.