Journal of applied physiology
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Correlation between transcutaneous and arterial CO2 partial pressure (Ptcco2, and Paco2) under normal and hemorrhagic shock conditions was evaluated in rabbits. Under normal conditions the Paco2-to-Ptcco2 least-squares regression line had a slope of 1.03 an intercept of 4.57 Torr, and a root mean variance of +/- 3.79 Torr. Under hemorrhagic shock conditions the slope remained similar, but the intercept increased, producing a significant difference between arterial and transcutaneous values. ⋯ The transcutaneous response time (90%) under conditions produced by breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the breathing 10% CO2 lagged 2.8 +/- 1.4 min behind that of the Paco2. The difference between transcutaneous and arterial CO2 observed during hemorrhagic shock and the lag in transcutaneous response time can be altered by topical application of dimethyl sulfoxide, by altering both flow and permeability. These results indicate that good Ptcco2-to-Paco2 correlation exists under normal conditions and that hemorrhagic shock will produce tissue CO2 accumulation and therefore higher than arterial Ptcco2 values.
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Comparative Study
Diminished hypoxic ventilatory responses in near-miss sudden infant death syndrome.
The ventilatory response to hypoxia and to hypercarbia was assessed in 36 near-miss sudden infant death syndrome (N. M SIDS) and 23 control infants. Base-line measurements during non-REM sleep documented no significant difference in respiratory frequency, alveolar CO2 and O2 partial pressure (PAco2 and PAo2) or tidal volume between the N-M SIDS and control infants. ⋯ For both groups, the increase in ventilation with hypoxia appeared linear within the PAo2 range assessed (65-115 Torr) and was therefore expressed as the slope of the delta VI/PAo2 plot (ml.kg-1 min-1 per Torr PAo2). The slope of the hypoxic ventilatory response was significantly less in the N-M SIDS than in the control group, -8.3 +/- 1.0 VS. -19.9 +/- 1.5, respectively (p less than 0.001). In summary, in comparison to control infants, N-M SIDS infants as a group have a significantly smaller increase in VI in response to hypoxia as well as to hypercarbia.