Objec+ves: Respiratory Physiology Basics

Transcription

1 Noninvasive Posi+ve Pressure Ven+la+on: Applica+ons to Avoid Crisis Al Quinones, DHA, MA, RRT- NPS, RPFT, RPSGT, CCT, AE- C, FACHE Objec+ves: - Review basic respiratory physiology - Discuss essen;al aspects of NIV - Compare applica;ons for CPAP and NIV - Discuss the evidence for NIV applica;on in various disease states Why Noninvasive Ven;la;on? Un;l recently, endotracheal intuba;on has been the preferred method for the ven;latory management of acute respiratory failure. Noninvasive ven;la;on for acute respiratory failure has the poten;al of: - reducing hospital morbidity - facilita;ng the weaning process from mechanical ven;la;on - shortening length of hospitaliza;on and cost - improving pa;ent comfort. Respiratory Physiology Basics Why do we breath? Respiratory center in the pons and the upper Medulla are responsible for rhythmic respira;on. Sensi;ve to PCO 2 in the arteries and ph level of the blood When PCO 2 increases, triggers increased ven;la;on Respiratory Physiology Basics Why do we breath? If oxygen doesn t reach muscles, lac+c acid is produced which decreases ph and s;mulates ven;la;on. If the caro;d or aor;c bodies sense a lack of oxygen in the blood, ven;la;on is s;mulated Respiratory Physiology Basics Two main forces oppose inspira+on: 1. Elas;c Forces 2. Fric;onal Forces Elas;c forces are created by the elas;c proper;es of the lungs and thorax that oppose inspira;on Fric;onal forces are created by the resistance of the ;ssues and organs as they move and the resistance to gas flow through the airways. Airway Resistance (Raw) Defined as airflow obstruc;on in the airways. Calculated using the following formula: Raw= P/V Peak Pressure / Plateau Flow Normal= cmh 2 0/L/sec Intubated= 6.0 cmh 2 0/L/sec Pulmonary Compliance Dynamic compliance is a measure of lung and chest wall s;ffness during gas flow (pressure to overcome Raw included).- Tidal Volume/ Peak Pressure- PEEP Sta;c compliance is a measure of lung and chest wall s;ffness during a period of no gas flow. Tidal Volume/ Plateau Pressure- PEEP Normal sta;c compliance ml/cmh 2 0 Ven;la;on is Important! 1

2 Non- Invasive Posi;ve Pressure Ven;la;on Defini+ons Con;nuous Posi;ve Airway Pressure (CPAP): A pressure that is greater than atmospheric pressure which is applied to the airway during both inspira;on and expira;on. Noninvasive Posi;ve Pressure Ven;la;on (NPPV): The use of posi;ve pressure to provide ven;lator support without an endotracheal or tracheostomy tube. Non- Invasive Con;nuous Posi;ve Airway Pressure (CPAP) Indica+ons for CPAP 1. Intermigent lung expansion 2. Acute hypoxemic respiratory failure 3. Acute cardiogenic pulmonary edema 4. Obstruc;ve sleep apnea Contraindica+ons 1. Inadequate respiratory drive 2. Pneumothorax 3. ICP > 20 mm Hg 4. Hemodynamic instability 5. Recent facial, oral, or skull trauma/ surgery 6. Acute sinusi;s or epistaxis 7. Inability to protect the airway / clear secre;ons 8. Impaired consciousness CPAP Major Benefits of CPAP 1. Recruitment of alveoli, increased FRC, reduced shunt= improved oxygena;on 2. Maintains patent airway during sleep by preven;ng upper airway collapse CPAP SeQngs Ini+al 1. Pressure: Can be set from 3-20 cmh 2 0 on most machines. 2. Ramp: Lowers ini+al set pressure and then increases to full sekng aler 5-45 minutes. Allows increased comfort. 3. C- Flex: Improves comfort by lowering pressure at start of exhala+on and then returning to full pressure just before inhala;on. CPAP Auto CPAP Ac;vely monitors one or more variables during sleep and adjusts pressure to respond to changes in upper airway. Depending on the manufacturer, the machine can monitor one or more of the following: 1. Snoring (pharyngeal wall vibra;on) 2. Inspiratory Flow Limita;on 3. Hyponeas 4. Apneas NPPV Pressures can be controlled on inspira;on and expira;on separately Inspiratory Posi+ve Airway Pressure (IPAP)- The amount of pressure applied to the airway via noninvasive ven;la;on during inspiratory phase of a breath. Expiratory Posi+ve Airway Pressure (EPAP)- The amount of pressure applied to the airway via noninvasive ven;la;on during the expiratory phase of breath. Synonymous with PEEP. NPPV Benefits 1. Decreased number of intuba;ons 2. Decreased mortality 3. Decreased VAP NPPV Indica;ons Strong Evidence for Use: 1. COPD Exacerba;ons 2. Acute Cardiogenic Pulmonary Edema Also Useful In: 1. Post- opera;ve pa;ents 2. Morbidly obese pa;ents 3. OSA 4. Decreasing WOB with DNI pa;ents 2

3 Therapeu;c Effects of BiPAP 1. Increase in IPAP improves ;dal volume with a subsequent reduc;on in PaC Increase in EPAP improves alveolar recruitment and FRC with a subsequent improvement in oxygena;on 3. IPAP and EPAP maintain patent upper airway during sleep. Ini;al CPAP Sekngs cmh 2 0 is the typical range for most applica;ons 2. In severe hypoxemia or OSA the pressure can double to cmh Therapeu;c value evaluated pulse ox, abg, sleep study, etc Mask Fikng Mask Fikng NPPV SeQngs BiPAP is a spontaneous mode that is much like PSV and PEEP. However, most ven;lators are PEEP compensated while Bipap units do not compensate for EPAP: Ven+lator SeQngs BiPAP SeQngs PEEP= +5 cmh 2 0 EPAP = +5 cmh 2 0 PSV= + 10 cmh 2 0 IPAP = +10 cmh 2 0 Pressure on Inspira+on Pressure on Expira+on Vent= 15 cmh 2 0 Vent= 5 cmh 2 0 Bipap= 10 cmh 2 0 Bipap= 5 cmh 2 0 Important Points for NPPV Sekngs Backup Rate: Olen set in case the pa;ent becomes apneic. However, the resistance and compliance of the lung and chest wall makes effec;ve ven;la;on without pa;ent assistance nearly impossible. If the pa+ent is not spontaneously breathing you must intubate! I- Time or % IPAP: Only determines inspiratory ;me for back- up rate breaths. No effect on spontaneous breaths. Clinical Evidence Con+nuous Posi+ve Airway Pressure (CPAP) Four randomized prospec;ve trials and one large prospec;ve series have demonstrated significant improvements in: - vital signs - gas exchange - reduc;ons in intuba;on rates - CPAP values where 10 to 12.5 cm H2O and administered via a face mask. Reduc;ons in mortality not consistently demonstrated. Barach (1983). Ann Intern Med 1983;12: Nihilism and COPD Nihilism comes from the La;n nihil, or nothing. Nihilism defined as crude scien;sm or nega;on. We must move away from the nihilism associated with COPD and view it as a disease that is preventable and treatable. 3

4 COPD and NIV Mul;center European trial randomized 85 pa;ents with exacerba;ons COPD to receive face mask PSV or conven;onal therapy. Intuba;on rates were lowered from 74% among control pa;ents to 26% among NPPV pa;ents. In addi;on, complica;on rates were reduced from 48 to 16%, mortality rates from 29 to 9%, and hospital lengths of stay from 35 to 23 d. Brochard L, Noninvasive ven;la;on for acute exacerba;ons of chronic obstruc;ve pulmonary disease. N Engl J Med 1995;333: Guidelines for Use of NPPV in Severe Stable COPD Centers for Medicare and Medicaid Services Guidelines PaCO2 > 52 mm Hg and Evidence of nocturnal hypoven;la;on based on nocturnal oximetry showing sustained desatura;on to 89% for 5 min while pa;ent is on his or her usual FIO2 Sleep apnea excluded clinically (polysomnogram not required) Requisite 3- month ini;al trial of bilevel device without a back- up rate NIV and Asthma Meduri conducted a study of 17 pa;ents with status asthma;cus. The average ini;al ph 7.25 and PaCO2 65 mm Hg, treated with face mask PSV. Only two required intuba;on, average dura;on of ven;la;on was 16 h, and no complica;ons occurred. They concluded that NIV was highly effec;ve in correc;ng gas exchange abnormali;es, and avoiding intuba;on in pa;ents with acute severe asthma exacerba;ons. **Lack of randomized controlled trials** Meduri. Chest 1996;110: Cys;c Fibrosis Hodson described the use of NIV to treat pa;ents with end- stage cys;c fibrosis with FEV 1 values ranging from 350 to 800 ml and severe acute on chronic CO 2 reten;on (ini;al PaCO2 values ranging from 63 to 112 mm Hg). Six pa;ents were supported for periods ranging from 3 to 36 d Poten;al u;lity of NPPV as a rescue therapy in suppor;ng pa;ents with acutely deteriora;ng cys;c fibrosis and in providing a bridge to transplanta+on. Hodson ME, Noninvasive mechanical ven;la;on for cys;c fibrosis pa;ents a poten;al bridge to transplanta;on. Eur Respir J 1991;4: Neuromuscular Diseases and NIV Bach described a regimen for managing acute deteriora;ons in pa;ents with chronic respiratory failure caused by neuromuscular disease. Pa;ents received 24- h noninvasive ven+la+on during the exacerba;on. Pulse oximetry is monitored con;nuously and when oxygen satura+on falls below 90%, secre;on removal is aggressively assisted using manually assisted coughing and mechanical aids such as the cough insufflator- exsufflator un;l oxygen satura;on returns to the 90% range. This approach permiged management in the home, with a drama;c reduc+on in the need for hospitaliza+on. Bach JR, Ishikawa Y, Kim H. Preven;on of pulmonary morbidity for pa;ents with Duchenne muscular dystrophy. Chest 1997;112: Acute Pulmonary Edema (APE)and NIV Two Studies have evaluated face mask PSV administered to pa;ents with acute pulmonary edema. In the first, pulse oximetry, ph, and PaCO2 all improved within 30 minutes of ini;a;on of NPPV in 29 pa;ents, only one of whom required intuba;on. The second study observed similar effects on gas exchange, but five of 26 pa;ents required intuba;on Hoffmann B, Welte T. The use of noninvasive pressure support ven;la;on for severe respiratory insufficiency due to pulmonary oedema. Intensive Care Med 1999;25: CPAP or NIV for APE? Metha conducted the only controlled trial comparing CPAP with NIV. Pa;ents treated with NIV had more rapid reduc;ons in PaCO 2 than did those in the CPAP group. However, the myocardial infarc+on rate was higher (71% in the NIV group versus 31% in the CPAP group) leading to premature termina;on of the study by the inves;gators. Rates of intuba;on, morbidity, and mortality were similar between the two groups NIV may have advantages in pa;ents with CO 2 reten;on, BUT CAUTION MUST BE APPLIED. Mehta S. Randomized prospec;ve trial of bilevel versus con;nuous posi;ve airway pressure in acute pulmonary edema. Crit Care Med 1997;25: Community Acquired Pneumonia Pa;ents treated with NIV had : - reduced intuba;on rates (21 versus 50%) - shorter dura;on of ICU stay (1.8 versus 6 d) than did control subjects Hospital lengths of stay and hospital mortality rates were similar. Although these results are promising, rou;ne use of NPPV for community- acquired pneumonia in pa;ents without COPD cannot be recommended. Sassoon C. Inspiratory muscle work of breathing during flow- by, demandflow and con;nuous- flow systems in pa;ents with chronic obstruc;ve pulmonary disease. Am Rev Respir Dis 1992;145: Hypoxemic Respiratory Failure Hypoxemic respiratory failure is defined as acute respiratory distress resul;ng in a PaO 2 of less than 60 mmhg, despite addi;on of supplemental oxygen of at least 60%. Keenan, Cook, and Hill (2004) Cri;cal Care Med, 32(12).- Performed a systema;c review of the literature. Concluded that evidence does not support the rou;ne use of NIV for hypoxemic respiratory failure. 4

5 Hypoxemic Respiratory Failure A trial of 64 pa;ents with hypoxemic respiratory failure randomized to receive NPPV or intuba;on, only 31% of the NPPV- treated pa+ents required intuba+on. Improvements in oxygena;on were comparable in the two groups, and NPPV- treated pa;ents had significantly fewer sep;c complica;ons such as pneumonia or sinusi;s (3% versus 31%). Another randomized controlled trial of 61 pa;ents with various forms of acute respiratory failure found a significantly reduced intuba+on rate when pa;ents with acute hypoxemic respiratory failure were treated with NPPV as opposed to conven;onal therapy Mar;n T. A randomized prospec;ve evalua;on of noninvasive ven;la;on for acute respiratory failure. Am J Respir Crit Care Med 2000;161: Immunocompromised Pa+ents By assis;ng ven;la;on without the need to invade and trauma;ze the upper airway, it should reduce infec;ous and hemorrhagic complica;ons. Earlier uncontrolled trials have shown encouraging results. Meduri and colleagues reported a 70% NPPV success rate in 11 pa;ents with AIDS and PneuumocyiLs caranii pneumonia. Meduri G. Noninvasive posi;ve pressure ven;la;on via face mask. Chest 1996;109: Acute Lung Injury/Acute Respiratory Distress Syndrome Studies on NIV to treat acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) have reported failure rates ranging from 50% to 80%. A recent prospec;ve mul;center survey found that when NIV was used as first- line therapy for selected ALI/ARDS pa;ents (those with > 2 organ failures, hemodynamic instability, or encephalopathy were excluded), 54% avoided intuba;on and had excellent outcomes. Rana S. Failure of non- invasive ven;la;on in pa;ents with acute lung injury: Observa;onal cohort study. Crit Care 2006; 10:R79 ARDS Demoule, et al conducted an analysis to determine variables associated with benefits and risks in NIV. A successful NIV trial was associated with lower hospital mortality. However, failing an NIV trail in ARDS was associated with higher mortality than in pa;ents who never received NIV. Demoule, et al. Intensive care medicine 2006; 32(11) Facilita+ng Extuba+on in COPD In intubated pa;ents with COPD and hypercapnic respiratory failure who failed a T- piece trial were extubated to NIV or con;nued on invasive ven;la;on and weaned according to a standard pressure support protocol, randomized trials showed - an increased weaning rate at 28 days - decreased dura;ons of mechanical ven;la;on and ICU stay - reduced rates of nosocomial pneumonia Based on these findings, COPD pa;ents who fail spontaneous breathing trials could be considered for a trial of extuba;on to NIV. Not a general recommenda;on. Nava S, et al: Non- invasive mechanical ven;la;on in the weaning of pa;ents with respiratory failure due to chronic obstruc;ve pulmonary disease: A randomized study. Ann Intern Med 1998; 128: Postextuba+on Respiratory Failure Extuba+on failure is associated with high morbidity and mortality. A RCT agempted to prevent extuba+on failure by star+ng NIV as soon as pa;ents developed signs of extuba;on failure. Surprisingly, not only did NIV fail to reduce reintuba+ons, but its use also was associated with increased ICU mortality, thought to be related to delays in needed reintuba;on. Two subsequent RCTs on pa;ents deemed to be at high risk for extuba;on failure found that NIV reduced the need for reintuba+on and ICU mortality. These data tend to support the use of NIV in pa;ents at high risk of extuba;on failure, par;cularly if they have COPD. However, NIV should be monitored closely and delays in needed intuba;on avoided. Ferrer. Am J Respir Crit Care Med 2006; 173: Postopera+ve Respiratory Failure Both CPAP and NIV have shown benefit in the postopera;ve period. In the only RCT of NIV in the postopera;ve sekng, pa;ents with hypoxemic respiratory failure aler lung resec;on had reduced intuba;on and mortality rates if treated with NIV when compared with standard management. The data lend support to the use of CPAP or NIV in postopera;ve pa;ents, but no firm recomenda;on. Jallot A, Herve P, et al: Noninvasive ven;la;on reduces mortality in acute respiratory failure following lung resec;on. Am J Respir Crit Care Med 2001; 164: Respiratory Therapist Time Demands NPPV pa;ents tended to require more ;me from respiratory therapists during the first 8 h of use, an amount that fell significantly during the second 8 h. Nava and colleagues also found that respiratory therapists spent more ;me during the first 48 h caring for NPPV than for invasively ven;lated pa;ents. These findings suggest that NPPV ini+ally requires more +me to administer than conven+onal therapy. Do you agree? Nava S, Human and financial costs of noninvasive mechanical ven;la;on in pa;ents affected by COPD and acute respiratory failure. Chest 1997;111: Role of the Therapist The successful ini;a;on of noninvasive ven;la;on is highly dependent on pa;ent coopera;on. For this reason, an experienced therapist conveying confidence and assuredness to pa;ents is crucial to success. The clinician should serve the role of facilitator, mo+va+ng the pa+ent, explaining the purpose of each piece of equipment, and preparing the pa+ent for each step in the ini+a+on process. 5

6 Review Ques+ons 1. The highest level of evidence supports the use of NIV as a standard of care in the treatment of: a. CAP b. ARDS c. Acute Asthma d. Acute exacerba;ons of COPD Review Ques+ons 2. Clinical benefits of NIV in an acute care sekng include all of the following except: a. Lower incidence of VAP b. Improved comfort compared to invasive ven;la;on c. Reduced RT staff ;me to set- up and manage d. Lower intuba;on rate Case Study A 78 year old male with a history of COPD and respiratory muscle weakness is receiving NIV for ven;latory failure secondary to postop pneumonia. The pa;ent is wearing a full face mask but is having progressive difficulty swallowing and coughing. He appears very weak and has become more confused in the past hour. The RR is 26, and Sat 92%. Oxygen is being bled into the mask at 5 lpm. What ac+on should be taken? 6