Human chest wall function while awake and during halothane anesthesia

I. Quiet breathing

David Oman Warner, M. A. Warner, E. L. Ritman

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

Background: Data concerning chest wall configuration and the activities of the major respiratory muscles that determine this configuration during anesthesia in humans are limited. The aim of this study was to determine the effects of halothane anesthesia on respiratory muscle activity and chest wall shape and motion during spontaneous breathing. Methods: Six human subjects were studied while awake and during 1 MAC halothane anesthesia. Respiratory muscle activity was measured using fine-wire electromyography electrodes. Chest wall configuration was determined using images of the thorax obtained by three-dimensional fast computed tomography. Tidal changes in gas volume were measured by integrating respiratory gas flow, and the functional residual capacity was measured by a nitrogen dilution technique. Results: While awake, ribcage expansion was responsible for 25 ± 4% (mean ± SE) of the total change in thoracic volume (ΔV(th)) during inspiration. Phasic inspiratory activity was regularly present in the diaphragm and parasternal intercostal muscles. Halothane anesthesia (1 MAC) abolished activity in the parasternal intercostal muscles and increased phasic expiratory activity in the abdominal muscles and lateral ribcage muscles. However, halothane did not significantly change the ribcage contribution to ΔV(th) (18 ± 4%). Intrathoracic blood volume, measured by comparing changes in total thoracic volume and gas volume, increased significantly during inspiration both while awake and while anesthetized (by approximately 20% of ΔV(th), P < 0.05). Halothane anesthesia significantly reduced the functional residual capacity (by 258 ± 78 ml), primarily via an inward motion of the end-expiratory position of the ribcage. Although the diaphragm consistently changed shape, with a cephalad displacement of posterior regions and a caudad displacement of anterior regions, the diaphragm did not consistently contribute to the reduction in the functional residual capacity. Halothane anesthesia consistently increased the curvature of the thoracic spine measured in the sagittal plane. Conclusions: The authors conclude that (1) ribcage expansion is relatively well preserved during halothane anesthesia despite the loss of parasternal intercostal muscle activity; (2) an inward displacement of the ribcage accounts for most of the decrease in functional residual capacity caused by halothane anesthesia, accompanied by changes in diaphragm shape that may be related to motion of its insertions on the thoracoabdominal wall; and (3) changes in intrathoracic blood volume constitute a significant fraction of ΔV(th) during tidal breathing.

Original languageEnglish (US)
Pages (from-to)6-19
Number of pages14
JournalAnesthesiology
Volume82
Issue number1
DOIs
StatePublished - 1995

Fingerprint

Thoracic Wall
Halothane
Respiration
Anesthesia
Functional Residual Capacity
Intercostal Muscles
Diaphragm
Respiratory Muscles
Thorax
Gases
Blood Volume
Abdominal Muscles
Indicator Dilution Techniques
Electromyography
Rib Cage
Electrodes
Spine
Nitrogen
Tomography
Muscles

Keywords

  • Anesthetics, volatile: halothane
  • Lung: breathing pattern; diaphragm; functional residual capacity;Intrathoracic blood volume; ribcage
  • Measurement technique: dynamic spatial reconstructor; electromyography; fast computed tomography; respiratory impedance plethysmography
  • Muscle: diaphragm; external oblique; parasternal intercostal; respiratory; transversus abdominis

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Human chest wall function while awake and during halothane anesthesia : I. Quiet breathing. / Warner, David Oman; Warner, M. A.; Ritman, E. L.

In: Anesthesiology, Vol. 82, No. 1, 1995, p. 6-19.

Research output: Contribution to journalArticle

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