PMV - Have we really come that far since the days of...

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Unformatted text preview: Have we really come that far since the days of Negative Pressure Ventilation? Prolonged Mechanical Prolonged Ventilation Ventilation Weaning Strategies in the ICU When is MV Prolonged? When Numerous Definitions NAMDRC Consensus Statement >21 consecutive days for >6 h/d (recommendation #1) Estimated 5% of MV patients will require PMV (Pierson et al.) But, nearly 34% of patients intubated for >48 hours will require extended intubations Patient Type Patient Older Comorbid Conditions Underlying Obstructive Lung Disease Ventilator Dependence Ventilator Systemic Chronic comorbid conditions Chronic Hypercapnia Organ Failure (Renal failure especially can dramatically increase the mortality rate) Mechanics Increased Work of Breathing Decreased Respiratory Muscle Capacity Intrinsic PEEP Airway Patency (eg. tracheal stenosis) Iatrogenic Unrecognized withdrawal potential Inappropriate vent settings MEDS (Suppress drive and muscle weakness) Long­term hospital stay Infection (VAP, Sepsis/SIRS—decrease O2 uptake) Recurrent Aspiration DVT Psych Sedation Depression Anxiety Dependence/Failure to Wean Dependence/Failure Additional Features • Cardiovascular Function • Ischemia • Heart Failure • Metabolic Derangements • • • • Hypophosphatemia Hypocalcemia Hypomagnesemia Hypothyroidism (severe) • • Poor—protein catabolism Overfeeding—excess CO2 • Nutrition • Deconditioning Complications of PMV Complications Infection • • • Bacterial Pneumonia Line sepsis C. Diff Volume Overload Laryngeal Edema Pneumothorax Tracheal Bleeding Renal Failure Ileus GI Bleeding DVT Additional Complications if Tracheostomy is necessary Weaning Weaning Start as soon as possible Success depends generally on 1) Strength of Respiratory muscles 2) Load Applied 3) Drive to Breath Has the problem which led to intubation been resolved? Is there a new problem? Identify those factors contributing to dependence that are potentially reversible (NAMDRC Rec #4) Sedative­based depression of respiratory drive can lead to inappropriately prolonged dependence on MV Initiate Weaning When there is: 1. Adequate Oxygenation 2. 3. 4. 5. A) PaO2/FiO2 >150­200 B) Vent Settings: PEEP <8 and FiO2 <0.5 pH >7.25 Hemodynamic stablility Ability to Initiate an Inspiratory Effort Sedation (esp. with resp­depressing drugs) has itself been weaned Predicting Success Predicting A number of criteria have been proposed Vital Capacity Tidal Volume (using a cutoff of 4 mL/Kg) • PPV 0.67, NPV 0.85 PaO2/FiO2 Max Insp. Pressure RR/VT (Rapid Shallow Breathing Index) RSBI RSBI First described by Yang and Tobin in 1991 Simply the f/VT Observation that those who fail weaning trials decrease their tidal volumes and increase their rate Threshold <105 • PPV: 0.78 and NPV: 0.95 In PMV In Even with these indices predicting weaning success in this population is difficult. Some attempts have been made Success has been correlated with number of comorbid diagnoses as well as length of MV Scheinhorn et al used A­a gradient, gender, and BUN (recognizing the increased mortality when renal failure was involved) to attempt to score the likelihood of successful weaning. Unfortunately this has shown limited success in repeat studies. Additionally, the up and coming use of post­ICU weaning facilities has improved weaning outcome. Methods of Weaning Methods Synchronized Intermittent Mandatory Ventilation (SIMV) Pressure Support Ventilation (PSV) SBT No Support CPAP PS NB: These methods are the same used with acute patients. The important difference is PMV patients generally require a more gradual weaning course SIMV SIMV Breaths are either spontaneous (+/­ pressure support) or mandatory vent­ controlled. Mandatory breaths are synchronized with patient’s own efforts Allows for a gradual decrease in ventilator­provided support and a gradual increase in the patient’s respiratory workload Rate is Reduced Progressively (2 breaths every 1­2 hours) Blood gasses are checked Patient is monitored for ability to accept increased work of breathing (HR, RR, Sats, clinical signs) But, studies have shown that respiratory muscles are unable to rest during the mandatory ventilator breaths (the respiratory center fails to adapt to the intermittent support). Can delay weaning by contributing to the development of respiratory muscle fatigue and therefore can delay extubation Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. Spanish lung failure collaborative group. N Engl J Med 1995; 332:345­350 Pressure Support Ventilation Pressure All breaths are spontaneous. But when PS is high relative to patient effort, support is almost fully from MV Enough PS is given with each breath to ensure an adequate VT. Method Gradually decrease the amount of PS (transferring the work to the patient) Once PS approaches 5­6 cmH2O extubation can be considered Reduces the work of breathing Can be used in conjunction with SIMV during weaning Reduces the likelihood of reintubation but was shown to be only slightly better than SIMV in duration of weaning SBT—Sink or Swim SBT—Sink Applications Extubation readiness—a 90 minute test (though at least one study—Esteban et al—suggested that only 30 min may be necessary) Weaning • Length of SBT is increased daily • Periods of ventilation are alternated with these trials • T­piece Trials Requires removing patient from vent and providing supplemental humidified O2 to their airway (through a tube that looks like a T.) These trials can also now be done with the patient still directly connected to the vent which allows closer observation (and all the bells and whistles that the vent provides) Types of SBTs Types 1. 2. 3. No Vent Support Low level of CPAP—closing pressure Low Level of PS—airway resistance No controlled studies have demonstrated superiority of any of these modes. However, in certain patient populations such as those with marginal left ventricular function, a low level of CPAP and the subsequent increase in intrathoracic pressure can help prevent heart failure. But, its removal, may lead to acute heart failure following extubation secondary to increased LV preload and LVEDP Trial Trial 30­90 minutes Once daily Following each SBT evaluate for possible extubation A number of studies have demonstrated equivalent results between multiple daily tests and once daily tests BP, RR, HR, ABG should all be considered Level of sedation SBTs are superior to both IMV and PS in duration of weaning and likelihood of success after weaning In patients on PMV, daily trials may be required for a longer period of time. Seminal Study (Esteban et al) Seminal 546 Patients All underwent a 2­hr SBT to evaluate for extubation • 130 had respiratory distress during the SBT and were not extubated • These pts were randomized to 1 of 4 groups • SIMV—initial rate of 10.0 breaths per minute, then decreased at least twice a day, by 2 to 4 bpm (29) • PSV—initially set at 18.0 cm H2O then reduced by 2 to 4 cm H2O at least twice a day (37) • Once a day SBT (31) • Multiple daily SBTs (33) Conclusion Conclusion A once­daily SBT led to extubation about three times more quickly than IMV and about twice as quickly as PSV. Multiple daily SBTs were equally successful. Weaning Protocol Weaning Improve overall outcome Example: 1. Is patient is a candidate for weaning? 2. Screen for readiness—RSB Trial 3. Ensure intact airway reflexes 4. Patient can now be subject to SBTs 5. SBT can be terminated if patient: i) PaO2 > 60mmHg ii) FiO2 <0.5 iii) PEEP < 8 cm H2O i) SBT for one minute to calculate RSBI i) Coughing during suctioning i) ii) PS, CPAP, or T­piece Up to 120 minutes i) ii) Successfully tolerates the SBT from 30­120 minutes Shows s/sx of failure Weaning Failure Weaning HR >140 bpm or a sustained increase of >20% RR >35 breaths/min for >5 min O2 Sats <90% for >30s HR with a sustained decrease of >20% SBP>180 for > 5 min SBP<90 for > 5 min Clinical features: Anxiety, agitation, diaphoresis NB: May not be due to weaning failure and should be treated appropriately Problems with Failure Problems Failing can put significant stress on the respiratory system Inspiratory effort can increase 4­6 times following a failed SBT (Jubran et al.) Who should run the Trial? Protocols are driven by RT and/or nurses Studies have shown that protocol­driven weaning by these individuals is superior to independent physician­directed weaning (Horst et al.) Sending PMV patients to institutions dedicated specifically to weaning improves outcomes (ie, Long­Term Assisted Care facilities) The Future The Automatic Tube Compensation Proportional­Assist Ventilation Compensates for pressure drop across ET tube Delivers the exact amount of pressure to overcome the resistive load of the tube given the flow across the tube measured at that instant (variable pressure support) Studies by Cohen and others have demonstrated that ATC improves weaning outcome compared to PSV and CPAP No studies as of yet have compared ATC vs. T­piece Ventilator adjusts airway pressure in proportion to patients instantaneous effort. This occurs from breath­to­breath and continuously through each inspiration No set tidal volume, pressure, or flow rate. The patient’s work of breathing remains constant despite changing effort or demand Computer­Driven Protocols Using knowledge­based algorithms Decreased MV duration from 12 to 7.5 days in a recent trial (Lellouche et al.) Used automatic gradual reduction in pressure support Automatic Performance of SBTs Outcomes in PMV Patients Outcomes Population is very diverse • Results are therefore difficult to generalize • For example, patients who require PMV post­operatively generally do significantly better than patients with COPD LTAC facilities • Scheinhorn et al.(2007) Large, multicenter trial evaluating outcomes in post­ICU PMV patients at 23 LTAC facilities. Scheinhorn et al (2007) Scheinhorn 1,419 patients 23 sites from 3/2002­2/2003 Excluded: End­of­life care; terminal weaning, or considered incapable of weaning at the time of admission One­Year Mortality: 52% 25% died in the weaning hospital 27% died after discharge Survival to Discharge: 67% Cost: $3968/day References References Cohen JD, Shapiro M, et al. Automatic tube compensation­assissted respiratory rate to tidal volume ratio improves the prediction of weaning outcome. Chest 2002. 122:980­4 Ely EW, Baker AM, Dunagan DP, et al. Effect of the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996; 335:1864–1869 Eskanadar N, Apostolakos M.Weaning from mechanical ventilation.Crit Care Clin(2007) 23:263­274 Esteban A, Alia I, Gordo F. Weaning: what the recent studies have shown us. Clin Pulm Med 1996, 3:91­100 Esteban E, Alia I, Tobin MJ, et al. Effect of spontaneous breathing trial duration on outcome of attempts to discontinue mechanical ventilation. Am J Respir Crit Care Med 1999; 159:512–518 Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med 1995; 6:345–350 Horst HM, Muoro D, et al. Decrease in ventilation time with a standardized weaning process. Arch Surg 1998. 133:483­489 Jubran A, Tobin MJ. Pathophysiologic basis of acute respiratory distress in patients who fail a trial of weaning from mechanical ventilation. Am J Resp Crit Care Med 1997; 155: 906 Lellouche F, Mancebo J, Jolliet P, et al. Am J Respir Crit Care Med 2006. 174:894­900 Lemaire F, Teboul J, Cinotti L, et al. Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation. Anesthesiology 1988; 69:171–179 Pierson DJ. Long­term mechanical ventilation and weaning. Respir Care 1995; 40: 289­95. Scalise PJ, Vottol JJ. Weaning from long­term mechanical ventilation. Chron Respir Dis 2005. 2: 99­103 Scheinhom DJ, Artinian BM, Catlin JL et al. Weaning from prolonged mechanical ventilation. The experience at a regional weaning center. Chest 1994; 105: 534­39. Scheinhorn DJ, et al. Post­ICU mechanical ventilation at 23 long­term care hospitals: a multicenter outcomes study. Chest 2007; 131:85 ...
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