John F. McConville, M.D., and John P. Kress, M.D. New England Journal of Medicine (2012) December Vol. 367 Weaning Patients from the Ventilator Journal club R4. Yoo, Jung-sun

2 types of respiratory failure 1. Hypoxic respiratory failure FiO2 > 0.6  SaO2 < 90% 2. Hypercarbic respiratory failure PaCO2 > 50mmHg & PH < 7.3 Mechanical ventilation indication

Definition of the different stages, from initiation to mechanical ventilation to weaning StagesDefinitions Treatment of ARF Period of care and resolution of the disorder that caused respiratory failure and prompted mechanical ventilation Suspicion The point at which the clinician suspects the patient may be ready to begin the weaning process Assessing readiness to wean Daily testing of physiological measures of readiness for weaning (MIP, fR/VT) to determine probability of weaning success Spontaneous breathing trial Assessment of the patient’s ability to breathe spontaneously Extubation Removal of the endotracheal tube Reintubation Replacement of the endotracheal tube for patients who are unable to sustain spontaneous ventilation ARF: acute respiratory failure, MIP: maximal inspiratory pressure, fR/VT: respiratory frequency to tidal volume ratio (rapid shallow breathing index). Martin J. Tobin Schematic representation of the different stages

Weaning failure : either the failure of SBT or the need for reintuba tion within 48 h following extubation Failure of SBT: objective indices of failure, such as tachypnea, tachycardia, hyperten sion, hypotension, hypoxaemia or acidosis, arrhythmia subjective indices, such as agitation or distress, depressed mental sta tus, diaphoresis and evidence of increasing effort Failure of SBT: often related to cardiovascular dysfunction or inabili ty of the respiratory pump to support the load of breathing. Extubation failure: may be related to the same causes, in addition to upper airway obstruction or excessive secretions. Definitions of Weaning Success and Failure Chest 2007; 132;

Clinical assessment Adequate cough Absence of excessive tracheobronchial secretion Resolution of disease acute phase for which the patient was intubated Objective measurements Clinical stability Stable cardiovascular status (i.e. fC  140 beats/min, systolic BP 90–160 mmHg, no or minimal vasopressors) Stable cardiovascular status (i.e. fC  140 beats/min, systolic BP 90–160 mmHg, no or minimal vasopressors) Stable metabolic status Stable metabolic status Adequate oxygenation SaO 2  90% on  FIO (or PaO 2 /FIO 2  150 mmHg) SaO 2  90% on  FIO (or PaO 2 /FIO 2  150 mmHg) PEEP  8 cmH 2 O PEEP  8 cmH 2 O Adequate pulmonary function fR  35 breaths/min fR  35 breaths/min MIP  -20– -25 cmH 2 O MIP  -20– -25 cmH 2 O VT  5 mL/kg VT  5 mL/kg VC  10 mL/kg VC  10 mL/kg fR/VT  105 breaths/min/L fR/VT  105 breaths/min/L No significant respiratory acidosis No significant respiratory acidosis Adequate mentation No sedation or adequate mentation on sedation (or stable neurologic patient) No sedation or adequate mentation on sedation (or stable neurologic patient) fC: cardiac frequency; BP: blood pressure; SaO 2 : arterial oxygen saturation; F I O 2 : inspiratory oxygen fraction; PaO 2 : arterial oxygen tension; PEEP: positive end-expiratory pressure; fR: respiratory frequency; MIP: maximal inspiratory pressure; VT: tidal volume; VC: vital capacity. 1 mmHg  kPa. Considerations for Assessing Readiness to Wean Chest 2007; 132;

NEJM 2012;367; Typical algorithm to discontinue mechanical vent. Typical readiness criteria : 1. Hemodynamic stability 2. Ratio of the partial pressure of arterial oxygen (measured in millimeters of mercury) to the fraction of inspired oxygen (which is unitless) of more than 200 (Pa02/FiO2 >=200) 3. The ventilator set to deliver a positive end-expiratory pressure of 5 cm of water or less 4. Some improvement in the underlying condition that caused the respiratory failure  Accomplish criteria swithced Volume control mode, Pressure control mode to Pressure support, CPAP, Ventilation with T-piece

NEJM 2012;367; C Typical algorithm to discontinue mechanical vent. Spontaneous breathing trial to be successful : patient must breathe spontaneously with little or no ventilator support for at least 30 minutes without any of the following ; 1. RR >= 35 breaths per minute for more than5 minutes 2. Oxygen saturation =140 beats per minute, 3. sustained change in the heart rate of 20%, systolic blood pressure >=180 mmHg or <= 90 mmHg, increased anxiety, or diaphoresis  If Spontaneous breathing is successful  Before removal of the endotracheal tube 1. The quantity of airway secretions 2. The strength of cough 3. Mentation.  The mechanism underlying the respiratory failure and the inability of the patient to breathe spontaneously should be determined and addressed daily (Mechanical Ventilator)

NEJM 2012;367; Typical algorithm to discontinue mechanical vent.

Chest 2007; 132;

Strategies to reduce the duration of mechenicla Vent. Minimizing the duration of mechanical ventilation : an important consideration for all clinicians who care for critically ill patients. The first textbook on mechanical ventilation, published in 1965, stated: “To know the proper timing and rate of weaning from the respirator requires considerable judgment and experience. As a rule, weaning should start as soon as possible.” Prospective observational study : involving patients with brain injuries, compared discontinuation of mechanical ventilation within 48 hours after readiness criteria had been met Vs more than a 48-hour delay in discontinuation  There was higher mortality, an increased risk of pneumonia, and a longer hospital stay (in the group with delayed discontinuation)  Clinicians should be motivated to minimize the duration of MV. Am J Respir Crit Care Med 2000; 161: NEJM 2012;367;

Strategies to reduce the duration of mechenicla Vent. Efforts to decrease the duration of mechanical ventilation can be divided into two categories: 1. Earlier appreciation of readiness for spontaneous breathing 2. Trials and a shorter process of discontinuing mechanical ventilation Many studies have tried to identify simple measurements (help clinicians predict which patients are ready for a spontaneous-breathing trial)  ratio of the respiratory rate (expressed in breaths per minute) to tidal volume (expressed in liters) (f/Vt) <=105 breaths/min/L (positive predictive value, 78%; negative predictive value, 95%) NEJM 2012;367; NEJM 1991;324;

Strategies to reduce the duration of mechenicla Vent. However, most experts agree that the best method of determining : Readiness criteria. It is the standardized approach to management rather than any specific method of ventilator support, prespecified readiness, or criteria for discontinuation of mechanical ventilation : reduces the duration of mechanical ventilation and improves outcomes.  Thus, most guidelines recommend that patients (Mechanical ventilation) be assessed daily for their readiness to breathe spontaneously CHEST 2001;120;Suppl:375S-395S

Approaches to spontaneous breathing trials This imbalance can lead to an unsuccessful spontaneous-breathing trial.

Approaches to spontaneous breathing trials Prolonged transition: at least three unsuccessful spontaneous-breathing trials or 7 days or more of mechanical ventilation after the initial unsuccessful trial. Tracheostomy is performed in patients who require prolonged weaning Although some studies have suggested that early tracheostomy might reduce short-term mortality, the length of stay in the ICU, and the incidence of pneumonia  other studies have not shown such benefits. A recent meta-analysis led to the conclusion that there is insufficient evidence of improved outcomes to warrant a recommendation for early tracheostomy. Crit care Med 2004;32:2566 Ann Intern Med 2011;154: Cochrane Database Syst Rev 2012;3:CD007271

Unsuccessful weaning from the ventilator Patients (who require reintubation) : increased risk of death, a prolonged hospital stay, and a decreased returning home (as compared with patients in whom discontinuation of mechanical ventilation is successful.)  Thus, it is essential that critical care physicians identify risk factors for failure of extubation despite successful spontaneous breathing trials. Measured peak cough flow, quantified endotracheal secretions, and assessed mental status (in 88 patients in whom discontinuation of mechanical ventilation was attempted after a spontaneousbreathing trial)  All the patients with inadequate cough, excessive secretions, and poor mental status required reintubation  3% patients with adequate require reintubation Chest 1997; 112; Intensive Care Med 2004; 30;1334-9

Treatment of Respiratory Distress after Extubation Two studies randomly assigned patients with respiratory distress that developed after discontinuation of mechanical ventilation to standard care (primarily oxygen and bronchodilators) Vs noninvasive positive- pressure ventilation (NIPPV)  No significant difference in reintubation, increased mortality in one of the studies Patients(Increased risk for extubation failure) to usual care Vs preemptive NIPPV  Both studies showed that the groups receiving NIPPV ventilation had a reduced need for reintubation JAMA 2002; 287; Crit Care Med 2005; 33; NEJM 2004; 350; Am J Respir Crit Care Med 2006; 173;164-70

Treatment of Respiratory Distress after Extubation Risk factors for unsuccessful discontinuation of mechanical ventilation are listed c

Future research Ongoing research : alter our approach to the discontinuation of mechanical ventilation in the near future. Currently, computerized systems automatically adjust ventilatory support on the basis of frequent monitoring of a patient’s respiratory rate, tidal volume, and gas exchange. Early studies of these automated weaning systems have had conflicting results.  Nevetheless reduced levels of ventilatory support without adverse effects has the potential to more quickly Additional studies are also likely to identify treatment algorithms that shorten the duration of mechanical ventilation or that reduce risk factors for unsuccessful discontinuation of ventilation after a successful spontaneous-breathing trial.