HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dawes, G. S. Articles by Walker, D. W. Search for Related Content PubMed PubMed Citation Articles by Dawes, G. S. Articles by Walker, D. W.

Nuffield Institute for Medical Research, University of Oxford, Oxford

1. The electromyographic (e.m.g.) activity of the diaphragm and intercostal muscles has been recorded during breathing movements of unanaesthetized lambs in utero (109-135 days), and compared with the changes of tracheal pressure.

2. The diaphragm e.m.g. was irregular in size, shape and timing, with a variable rate of rise during inspiration, often with a flattening of integrated activity before the end of a breath and with little or no post-inspiratory activity.

3. The diaphragm e.m.g. gave the most reliable measurements of breath interval and incidence: in eucapnia mean T_I was 0.45±0.02 (S.E. of mean) and T_E was 0.74±0.05 sec, and 58-100% of the diaphragm bursts were associated with identifiable and appropriate changes of tracheal pressure.

4. During fetal hypercapnia, produced by increasing the maternal inspired CO₂ in a single change or series of step changes, tracheal pressure amplitude and its rate of change during inspiration increased progressively over the P_{a, CO2} range of 37-87 mmHg.

5. In eucapnia the area, amplitude and inspiratory slope of the integrated diaphragm e.m.g. were not always correlated with tracheal pressure amplitude, and in hypercapnia they increased only in the lower part of the P_{a, CO2} range. Inspiratory intercostal activity increased progressively as the P_{a, CO2} was raised.

6. The frequency histograms of variables derived from the tracheal pressure, diaphragm and intercostal e.m.g.s were skewed to the left in eucapnia but became normalized during hypercapnia. The rate and depth of breathing became regular.

7. The response to mild asphyxia was a combination of the responses to hypercapnia and hypoxia.

8. The interpretation of the tracheal pressure and diaphragm e.m.g. as measures of the `depth' of breathing and respiratory `drive' in the fetal lamb is discussed.

This article has been cited by other articles:

				B. J. Koos, Y. Kawasaki, A. Hari, F. Bohorquez, C. Jan, J. Roostaeian, C. L. Wilson, and L. Kruger Electrical stimulation of the posteromedial thalamus modulates breathing in unanesthetized fetal sheep J Appl Physiol, January 1, 2004; 96(1): 115 - 123. [Abstract] [Full Text] [PDF]