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報告人 : 邱翊洲

The Endotracheal Tube Cuff-Leak Test As a Predictor for Postextubation Stridor Eric J Kriner RRT, Shirin Shafazand MD MSc, and Gene L Colice MD Respir Care 2005;50(12):1632 – 1638. 報告人 : 邱翊洲. Translaryngeal intubation: life-saving for respiratory distress. 1. mechanical ventilation

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報告人 : 邱翊洲

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  1. The Endotracheal Tube Cuff-Leak TestAs a Predictor for Postextubation StridorEric J Kriner RRT, Shirin Shafazand MD MSc, and Gene L Colice MDRespir Care 2005;50(12):1632–1638 報告人: 邱翊洲

  2. Translaryngeal intubation: life-saving for respiratory distress. 1. mechanical ventilation 2. protection of the airway Complications: Laryngeal damage:ulceration, edema, and mechanical dysfunction  Usually well tolerated(most common: hoarseness)

  3. Postextubation stridor (PES) 1. much less common, but feared 2. 2–37% of patients immediately following extubation Treatment options 1.nebulized racemic epinephrine 2.heliumoxygen mixture (heliox) 3.corticosteroids. Reintubation: up to 10% of patients who require treatment for PES.

  4. The cuff-leak test (CLT) • 1. Simple, noninvasive method for identifying risk for PES. • 2. Previous studies on CLT: • small sample sizes(N<110) • narrow patient spectrum (pediatric, burn, or post- cardiac surgery). •  Objectives of this study: • 1. ? value of the CLT to predict PES in a large population of adult medical/surgical patients. • 2. Impact of variables(eg: pre-extubation corticosteroids, duration of intubation, ETT size relative to diameter of the larynx) on the incidence of PES.

  5. Methods 1. Prospective study 2. Medical and surgical ICU of Washington Hospital Center (907- bed acute-care hospital in Washington DC.) 3. All patients who require intubation at Washington Hospital Center, either pre-OP or in emergency situations evaluated by an anesthesiologist. 4. The ETTs: low-pressure, high-volume cuffs cuff pressure: < 24 cm H2O. 5. Ventilator management and discontinuance: Washington HospitalCenter’s standard-of-care practices/ discretion of the attending physician. 6. Intubated >=24 h evaluated daily for extubation readiness. 7. Prior to endotracheal extubation: CLT is performed by RT

  6. CLT: • 1.Patient placed in the semi-Fowler’s position • 2.Suctioned intraorally and intratracheally • 3.Put on the A/C ventilation mode. • 4.Cuff inflated to the minimum occlusion volume •  Record mechanical exhaled volume. • 5.Deflate the ETT cuff, the mehanical exhaled tidal volume observedover the next 6 respiratory cycles. •  Record the average of the 3 lowest exhaled volumes • 6.Cuff leak: difference between the mechanical exhaled volume with the cuff inflated and the average of the 3 lowest exhaled volumes with the cuff deflated.

  7. Post Extubation Stridor 1. Respiratory distress with inspiratory grunting, whistling, or wheezing 2. Developed in the 24 h following extubation and required physician-directed medical intervention beyond humidified O2 (e.g.: nebulized racemic epinephrine, heliox therapy, noninvasive positive-pressure ventilation,or reintubation.)

  8. From the medical record: 1. date of intubation/extubation 2. ETT size/ intubation route 3. intubated previously? if so, thereason for reintubation 4. volume of the cuff leak 5. exhaled volume with the cuff inflated 6. Hx of laryngeal disease/smoke inhalation; 7. initial indication for intubation. 8. corticosteroid administration prior to extubation 9.any treatment for PES. 10. absolute volume of the cuff leak/percentage of the volume leaked relative to the exhaled volume with the cuff inflated. 11.The ratio of the ETT size to laryngeal size

  9. Equation by Higenbottam and Payne for estimating laryngeal anterior-posterior (A-P) diameter: A-P diameter (mm) =(33.9 x height [m]) – 33.7 The ratio was established by comparing the outer diameter of the ETT to the determined A-P diameter of thelarynx.

  10. Miller and Cole: < 110ml mL of absolute volume • De Bast et al: <15.5% of the exhaled volume •  predicted PES. • In this study: • CLT failure: an absolute volume <110 mL or 15.5% of exhaled volume • Sensitivity, specificity, positive predictive value, and negative predictive value of the CLT • Likelihood ratios of a positive/negative test result • The diagnostic accuracy of the absolute cuff-leak volume and the percent of exhaled cuff-leak volume approaches for the CLT  inspected individually for ideal threshold values

  11. Results • 6-month period from Aug 1, 2002 ~ Jan 31, 2003 • 922 patients were intubated for >24 h. • 3.CLTs were not performed on 460 • death (108), • self-extubation (59) • tracheostomy (144) • omission of the CLT prior to extubation (149). • 4. 7 / 149 (1.5%) treated for PES. • 5. A pre-extubation CLT on the remaining 462 patients.

  12. Visual inspection of the 2 receiver-operating-characteristic curves 1. very similar 2. failed to identify specific threshold values as accurate predictors of PES 3. Prevalence/pre-test probability of PES in the study population: 4.3% (20/462).

  13. Outcomes of the 20 patients who were treated for stridor: • immediate reintubation: 5 patients (25%) • nebulized racemic epinephrine: • total 15 patients • 4 needs additional treatment: • heliox therapy noninvasively: 2 • Reintubation: 2 • Reintubation due to PES occurred: 1.5% (7/462) of patients.

  14. Table 4 Demographic data and baseline characteristics of patients with and without stridor.

  15. PES: more often among • 1. Female patient • (F 6.5% or 14/216 vs M 2.4% or 6/246) (p=0.04). • 2. Longer duration of intubation (6.5 4 vs 4.5  4 d, p=0.02) • Larger ETT/laryngeal size ratio (49.5  6 vs 45.5  6%, p = • 0.01) • 4. Smaller cuff leak • absolute volume (148 143 mL vs 277149 mL, p <0.001) • percentage of tidal volume (30  27% vs 55  26%, p < 0.001).

  16. PES: more often among 4. ETT/laryngeal size ratio: 45% was used as a threshold. 5. Intubation period: 6 day as a threshold for identifying a risk of PES 1% (9/127, > 6 days) vs 3.3% (11/335, <= 6 days.) (p = 0.02).

  17. Pre-extubation steroid Corticosteroids prior to extubation: PES 5.7% (6/106) vs No pre-extubation steroid PES: 3.9% (14/356) (p = 0.06).

  18. Discussion • CLT: insufficient for the test results to be used in routine treatment decisions.: • Failing the CLT: • not a useful predictor of PES • should not delay extubation or lead to the initiation of specific prophylactic treatment. • 3. The receiver-operating-characteristic analysis: neither of the • tested indices for cuff-leak failure, expressed as absolute volume or percent of exhaled volume was predictive of PES.

  19. Certain variables and the probability of PES. • 1.Female sex • 2.prolonged intubation • 3.large ETT size in relation to laryngeal size •  a higher risk of PES. • 4. Corticosteroids prior to extubation: •  not associated with a lower risk of PES.

  20. PES in the adult population: 2–37% of cases. • Variability  lack of uniform diagnostic criteria for PES. • The diagnosis of PES: • Subjective clinical end points: • prolonged inspiratory phase • use of accessory muscles, • requirement of treatment.

  21. Miller and Cole: PES definition: respiratory distress associated with a high-pitched whistling required treatment 6% of cases. Darmon et al: PES in 4.2% of cases, clinical end points. This study: clinical criteria prevalence (or pre-CLT test probability) of PES: 4.3%

  22. CLT test: 1. Likelihood ratio: about 3 for a positive test 2. Probability of developing PES with a failed CLT: only 12%  too low to be relied upon for clinical decision making

  23. 1. Receiver-operating-characteristic analysis  identify thresholds for predicting PES. 2. Absolute volume of 110 mL and a percent-of-exhaled-volume of 15.5% as threshold: • CLT had poor positive predictive value. • absolute volume and the percent-of-exhaled volume provided similar information • no apparent threshold for better performance characteristics.

  24. The pathogenesis of laryngeal injury and edema from translaryngeal intubation: 1. abrasion of the larynx due to pressure and friction, 2. laryngoscopically identified in 94% patients following extubation  most patients suffer only mild hoarseness  ? why PES occurs in only a small fraction?

  25. Laryngeal edema 1. more prevalent in female: • thinner mucosa on cartilage of the vocal process • less resistance to trauma • smaller laryngeal diameter 2. prolonged translaryngeal intubation 3. larger ratio of ETT size to laryngeal size  Contrubuted from friction and trauma

  26. Corticosteroids Several double-blind randomized controlled studies: dexamethasone and hydrocortisone:ineffective in preventing PES. In this study: Corticosteroids do not reduce the risk of PES.

  27. Inherent limitations of CLT: • 1. laryngeal edema assumed if expiratory flow into the upper airway nonexistent • 2. Factors on turbulent flow in the upper airway: • compliance of the lung • Airway resistance • respiratory mechanics • degree of muscular passivity during the expiratory cycle. •  no study analyzed the effects of lung mechanics/properties with respect to abnormal expiratory flow in the upper airway, and their impact on the CLT.

  28. Expiratory flow through the upper airway 1. influenced by ETT/larynx size ratio  expiratory flow into the upper airway may be hindered with a large ETT, even in the absence of laryngeal edema. CLT may accurately identify decreased expiratory flow through the upper airway  mechanical factors or laryngeal edema. ?  high false-positive rate for the CLT in this study ! A majority of patients in this study who had a false positive CLT (44/72 or 61%) : ETT/laryngeal size ratio > 45%.

  29. Conclusions 1. Failure of the CLT(absolute volume/ percentage of the exhaled volume)  an unreliable predictor of PES  NOT an indication for delaying extubation/ initiating other specific therapy. 2. Higher relative risk of PES • consistent abrasion-promoting variables • prolonged translaryngeal intubation, • a ratio of ETT size to laryngeal size > 45% • female 3. Pre-extubation corticosteroids did not decrease the incidence of PES.

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