Document Detail

Estimation of tracheal pressure and imposed expiratory work of breathing by endotracheal tube, heat moisture exchanger, and ventilator during mechanical ventilation.
MedLine Citation:
PMID:  23232731     Owner:  NLM     Status:  Publisher    
BACKGROUND. Resistance ofthe endotracheal tube (ETT),the heat moisture exchanger (HME),and the ventilator may affect patients' respiratory status. Although previous studies examined the inspiratory work of breathing (WOB), investigation of WOB in the expiratory phase is rare. We measured estimated tracheal pressure at the tip of an ETT (P(trach)) and calculated expiratory WOB imposed by the ETT, the HME, and the expiratory valve.We examined imposed expiratory WOB in patients under assist/control (A/C) mode or undergoing a spontaneous breathing trial (SBT).We hypothesized that imposed expiratory WOB would increase with heightened ventilatory demand. METHODS. We measured airway pressure (P(aw)) and respiratory flow (V). We estimated P(trach) using the equation P(trach) = P(aw)-k(1) × V(k(2)) -2.7045 × V (L/S)(1.4169). K(1) and K(2) were determined by the internal diameter (ID) of ETT. Imposed expiratory WOB was calculated from the area of P(trach) above positive end expiratory pressure vs. lung volume. We examined imposed expiratory WOB and imposed expiratory resistance(R(E)) in relation to mean expiratory V. RESULTS. We examined 28 patients under A/C mode and 29 under SBT. In both A/C and SBT, as mean expiratory V increased, imposed expiratory WOB increased. The regression curves between mean expiratory V (x) (L/s) and imposed expiratory WOB (y) (J/L) were (y = 1.3462x(0.83), R(2) = 0.7949) for 7mm ID ETT under A/C, (y = 1.115x(0.8211), R(2) = 0.7319) for 8 mm ID ETT under A/C, (y = 1.0712x(1.0416), R(2) = 0.8499) for 7 mm ID ETT under SBT, and (y = 0.835x(0.9347), R(2) = 0.7519) for 8 mm ID ETT under SBT. Levels of imposed expiratory WOB were affected by ETT diameter and ventilator mode. The reason for increasing imposed expiratory WOB wasan increase in R(E) imposed by ETT and HME. CONCLUSIONS. Under mechanical ventilation, imposed expiratory WOB should be considered in patients with higher minute ventilation.
Akinori Uchiyama; Takeshi Yoshida; Hidenori Yamanaka; Yuji Fujino
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-4
Journal Detail:
Title:  Respiratory care     Volume:  -     ISSN:  0020-1324     ISO Abbreviation:  Respir Care     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7510357     Medline TA:  Respir Care     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Department of Anesthesiology and Intensive Care Medicine, Osaka University Graduate School of Medicine.
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