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Biomedical subjects

D J Read

Publications and source records attributed to D J Read.

At least 73 records · Page 4Linked to original sources
PubMed1978

Ventilatory and waking responses to hypoxia in sleeping dogs.

We examined waking and ventilatory responses to acute hypoxia in four dogs during natural sleep. Progressive hypoxia was induced by a rebreathing technique in which alveolar CO2 pressure (PACO2) was held at the eucapnic level. Arterial O2 saturation (SaO2) was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Arousal from eucapnic hypoxia occurred at a SaO2 of 87.5 +/- 2.6% (mean +/- SE) during slow-wave sleep (SWS), and at a SaO2 of 70.5 +/- 3.4% during rapid-eye-movement (REM) sleep (P less than 0.005). The irregular pattern of breathing typical of REM sleep persisted during hypoxia. However linear regression analysis of breath-by-breath instantaneous minute volume of ventilation (VI) against SaO2 revealed regression coefficients in REM sleep that were similar to those found in SWS and wakefulness. This finding contrasts with earlier observations of a decreased response of VI to CO2 during REM sleep. The results indicate that although waking responses to hypoxia are delayed in REM sleep, ventilatory responses remain intact and therefore may be of importance in maintaining adequate ventilation during this stage of sleep.

Animals↗
PubMed1976

Intemittent obstruction of the upper airway during sleep causing profound hypoxaemia. A neglected mechanism exacerbating chronic respiratory failure.

An obese patient with a ten year history of respiratory failure presented with insomnia and marked daytime somnolence. Respriatory failure had been attributed to obesity, respiratory centre insensitivity to carbon dioxide, and to diffuse airways obstruction. To investigate the possible role of episodic apnoea with frequent nocturnal arousals, continous recordings were obtained during sleep of arterial oxygen saturation, oesophageal pressure and the motions of the rib-cage and abdomen/diaphragm. Repeated episodes of hypoventilation and profound hypoxaemia were found which were due to intermittent obstruction of the upper airway rather than to cessation of breathing efforts. During the episodes of hypoxaemia, values of arterial O2 tension fell to as low as 24 mmHg. Episodic hypoxaemia was relieved but not abolished, by the use of a collar, designed to hold the mandible forward. Previous reports indicated that recognition of intermittent obstruction of the upper airway during sleep and treatment by a permanent tracheostomy, resulted in a significant long-term imporvement of pulmonary and cardiac function and relief of insomnia and day-time somnolence. When tracheostomy is inadvisable, as in the present patient, it is hoped that similar long-term benefits will result from a supportive collar.

Airway Obstruction↗
PubMed1974

The role of arterial chemoreceptors in the breath-by-breath augmentation of inspiratory effort in rabbits during airway occlusion or elastic loading.

1. The breath-by-breath augmentation of inspiratory effort in the five breaths following airway occlusion or elastic loading was assessed in anaesthetized rabbits from changes of airway pressure, diaphragm e.m.g. and lung volume.2. When the airway was occluded in animals breathing air, arterial O(2) tension fell by 20 mmHg and CO(2) tension rose by 7 mmHg within the time of the first five loaded breaths.3. Inhalation of 100% O(2) or carotid denervation markedly reduced the breath-by-breath progression but had little or no effect on the responses at the first loaded breath.4. These results indicate that the breath-by-breath augmentation of inspiratory effort following addition of a load is mainly due to asphyxial stimulation of the carotid bodies, rather than to the gradual emergence of a powerful load-compensating reflex originating in the chest-wall, as postulated by some workers.5. The small residual progression seen in animals breathing 100% O(2) or following carotid denervation was not eliminated (a) by combining these procedures or (b) by addition of gas to the lungs to prevent the progressive lung deflation which occurred during airway occlusion.6. Bilateral vagotomy, when combined with carotid denervation, abolished the residual breath-by-breath progression of inspiratory effort.

Airway Obstruction↗
PubMed1971

Insensitivity of respiratory centre to carbon dioxide in the Enga people of New Guinea.

The ventilatory response to a rising carbon-dioxide (CO2) tension has been determined in healthy New Guinea natives using a new apparatus which was developed for field-work. The response in New Guineans did not vary greatly between individuals, in contrast to the finding in healthy Caucasians. In all twelve New Guinean subjects the indices of response fell in the lowest range of Caucasian response. These findings suggest that genetic and racial factors account for the marked variability of the ventilatory response to CO2 in normal man. It is suggested that inherited insensitivity of the respiratory centre in New Guineans (and in some Caucasians) leads to unusually severe disturbances of blood gases in chronic lung disease. This hypothesis is supported by published data relating arterial PCO2 and the severity of airways obstruction in New Guineans.

Carbon Dioxide↗