Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0085383 (hypocapnia)
 1,697 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To quantify any mechanical inhibitory effect of nasal intermittent positive pressure ventilation (IPPV) on inspiratory activity of the diaphragm we ventilated five conscious relaxed subjects on two occasions at respiratory rates similar to quiet breathing (QB) and at three levels of applied pressure (Pappl)--6, 9 and 12 cmH2O, each during hypocapnia (P(CO2) allowed to decrease) and eucapnia (CO2 added to inspired gas). Diaphragm activity was assessed from transdiaphragmatic pressure (esophageal and gastric balloons) and diaphragm EMG (surface electrodes) both integrated with time (integral(Pdi x dt) and integral(EMGdi x dt), respectively). Neural inspiratory time (Tin) was measured as onset to peak of the integral(EMGdi x dt) signal. Relative to QB, integral(Pdi x dt) was 50-69% less during eucapnic IPPV 6-12 cmH2O (P < 0.005) and 67-85% less during hypocapnic IPPV (P < 0.005). Tin decreased (P < 0.05) with IPPV and, on ceasing IPPV, there was apnoea (prolonged expiratory time) on 23 of 27 occasions; these changes were independent of P(CO2). Integral(EMGdi x dt) decreased (P < 0.05) at Pappl 12 cmH2O during eucapnia and at all Pappl during hypocapnia. The repeatability of integral(EMGdi x dt) was substantially less than integral(Pdi x dt) (F = 42, P << 0.01). We conclude that, during non-invasive IPPV in awake healthy subjects mechanical factors are of major importance in inhibiting inspiratory activity of the diaphragm.
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PMID:Diaphragm inhibition with positive pressure ventilation: quantification of mechanical effects. 1064 59

Millions of people currently live at altitudes in excess of 2500 metres, where oxygen supply is limited, but very little is known about the development of brain and behavioural function under such hypoxic conditions. We describe the physiological, cognitive and behavioural profile of a large cohort of infants (6-12 months), children (6-10 years) and adolescents (13-16 years) who were born and are living at three altitude locations in Bolivia ( approximately 500 m, approximately 2500 m and approximately 3700 m). Level of haemoglobin oxygen saturation and end-tidal carbon dioxide were significantly lower in all age groups living above 2500 metres, confirming the presence of hypoxia and hypocapnia, but without any detectable detriment to health. Infant measures of neurodevelopment and behaviour yielded comparable results across altitude groups. Neuropsychological assessment in children and adolescent groups indicated a minor reduction in psychomotor speed with increasing altitude, with no effect of age. This may result from slowing of underlying brain activity in parallel with reduced cerebral metabolism and blood flow, evidenced here by reduced cerebral blood flow velocity, particularly in the basilar artery, in children and adolescents. The proportion of European, Native American and African genetic admixture was comparable across altitude groups, suggesting that adaptation to high altitude in these children occurred in response to chronic hypoxic exposure irrespective of ethnic origin. Thus, psychomotor slowing is proposed to be an adaptive rather than a deficient trait, perhaps enabling accuracy of mental activity in hypoxic conditions.
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PMID:Development of aptitude at altitude. 2044 73