Document Detail

Constant positive airway pressure reduces hypoventilation induced by inhalation anesthesia.
MedLine Citation:
PMID:  15721729     Owner:  NLM     Status:  MEDLINE    
STUDY OBJECTIVE: To discover if reducing respiratory system impedance would increase tidal volume and improve ventilation during inhalation anesthesia. DESIGN: Prospective, randomized cross-over study. SUBJECTS: Nine ASA physical status I and II adult female oncology patients undergoing breast operations with or without lymph node dissection and general anesthesia while breathing spontaneously. INTERVENTIONS AND MEASUREMENTS: Patients underwent alternating trials of constant positive airway pressure, with or without pressure support. Constant positive airway pressure and pressure support were titrated to maximize respiratory system compliance and equal inspiratory pressure gradient across tracheal tube, respectively. Variables reflecting cardiovascular function, pulmonary mechanics and lung gas exchange, and respired gases and isoflurane concentrations were measured. MAIN RESULTS: End-tidal concentration of isoflurane (1.3 +/- 0.2%), Fio(2) (0.43 +/- 0.09 ), and CO(2) elimination (209 +/- 42 mL min(-1)) was unchanged throughout study in patients aged 63 +/- 12 years, weighing 72 +/- 12 kg. Constant positive airway pressure (12 +/- 2 cm H(2)O) increased respiratory system compliance from 52 +/- 8 to 80 +/- 9 mL cm H(2)O(-1) (P < .001), tidal volume from 156 +/- 32 to 325 +/- 52 mL (P < .001), and minute ventilation from 4.37 +/- 0.86 to 6.18 +/- 0.92 L min(-1) (P < .001). Respiratory rate decreased from 29 +/- 7 to 19 +/- 2 min(-1) (P < .001), Paco(2) decreased from 54 +/- 8 to 44 +/- 6 mm Hg (P < .001), and Pao(2) increased from 137 +/- 37 to 160 +/- 64 mm Hg (P < .001). Pressure support (3.1 +/- 0.3 cm H(2)O) did not alter ventilation or gas exchange. CONCLUSION: We conclude that constant positive airway pressure titrated to optimal respiratory system compliance will increase efficiency of inspiratory muscles and improve ventilation. Constant positive airway pressure facilitates a pattern of breathing that minimizes some of the adverse pulmonary effects of inhalation anesthesia.
Robert A Smith; Edward C Bratzke; Rafael V Miguel
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial    
Journal Detail:
Title:  Journal of clinical anesthesia     Volume:  17     ISSN:  0952-8180     ISO Abbreviation:  J Clin Anesth     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-02-21     Completed Date:  2005-06-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8812166     Medline TA:  J Clin Anesth     Country:  United States    
Other Details:
Languages:  eng     Pagination:  44-50     Citation Subset:  IM    
Department of Anesthesiology, University of South Florida College of Medicine, Tampa, FL 33612-4799, USA.
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MeSH Terms
Airway Resistance / physiology
Anesthesia, Inhalation / adverse effects*
Breast Neoplasms / surgery
Cross-Over Studies
Electrocardiography / drug effects
Hypoventilation / chemically induced*,  therapy*
Middle Aged
Monitoring, Intraoperative
Oxygen / blood
Positive-Pressure Respiration*
Respiratory Muscles / physiology
Tidal Volume / physiology
Reg. No./Substance:

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