2- Respiratory Distress/Mechanical Ventilation

Week 6 and 7 Key Concepts-Respiratory Distress/Mechanical Ventilation
1. Interpret arterial blood gases (ABG). Differentiate alkalosis/ acidosis and respiratory / metabolic
2. Identify a ventilation – perfusion mismatch and how to treat it
3. Be able to calculate an Aa gradient. Be able to interpret an Aa gradient
A-a gradient: alveolar-to arterial oxygen gradient; AaDO2; alveolar-to-arterial oxygen difference.
a. A calculation to aid in diagnosing the degree of a patient’s hypoxemia
b. Formula: difference between PAO2 and PaO2
1. PAO2: calculated
2. PaO2: from arterial blood gases
3. Note: A-a gradient OR AaDO2= PAO2-PaO2
4. Formula to calculate PAO2 on page 362
c. Normal values: difference between alveolar and arterial oxygen
1. Young adult breathing room air (FiO2)=21%) less than 10 mmHg difference
2. Adult older than age 60 on room air; less than 20 mmHg difference
3. Breathing FiO2 100%=less than 50 mmHg difference
4. Identify clinical symptoms or conditions indicating a need to intubate and ventilate a patient
Inadequate intrinsic respiratory capacity to prevent or compensate for severe hypoxia and or hybercarbia due to the following:
1. Drug
Opiods, Sedatives, NM blockers

2. Trauma
Spinal cord injury, phrenic nerve injury

3. Disease
GBS, Amyotrophic lateral sclerosis, Myasthenia gravis, shock

4. Exhaustion
Status asthmaticus, sustained severe work of breathing,

5. Sustained apnea of any cause
Persistent hypoxia in arterial blood less than 60 mmhg and or hypercarbia, PaCO2 greater than 50 mmHg, or airway maintenance
1. Diffusion defects: Aspiration, pulmonary edema, ARDS, COPD, PNA,
2. Ventilation defects: COPD, Pickwickian syndrome, flail chest, pneumothorax, atelectasis,
3. Perfusion defects: shock, pulmonary embolus, malignant arrhythmias

5. Identify clinical signs and symptoms indicating a patient is ready for weaning and extubation
WEANINGS FROM MECHANICAL VENTILATION:
a. The basic requirement is that initial indication for ventilation has been improved or eliminated.
b. Other factors will affect readiness to wean:
1. time on ventilator
2. psychological readiness
3. Nutritional status
4. ability to clear airway (cough)
5. Hemodynamic stability
c. Assessing readiness to wean
1. Conduct a spontaneous breathing trail daily when the following conditions are met:
a. FiO2 of 0.40 or less and PEEP of 8 or less
b. PEEP and FiO2 < or equal the values of previous day c. Patient has acceptable spontaneous breathing efforts, (may decrease vent rate by 50% for 5 minutes to detect effort) d. systolic blood pressure of 90 mmhg or more without vasopressor support c. No NM blocking agents or blockade or agents (ARDS protocol) 2. Additional factors to consider before attempting weaning: a. physical ability . respiratory rate <30 breaths per minute . minute ventilation < 12 L/minute b. Mechanical efficiency *vital capacity 10-15 ml/kg * Negative inspiratory force >20 cm H2O
c. Oxygenation and ventilation
* PaO2 >60 on FiO2 <.50 *PaCO2 less than 50 with pH 7.35 – 7.45 * PEEP +5 or less than SaO2 greater than 92% d. hemodynamics I: Cardiac index greater than 2.3 L/min/m2 II. Mean arterial pressure greater than 60 mmhg III. Heart rate less than 120 beats per and more than 60 IV: Pulmonary capillary wedge pressure less than 18 mmHg (18-25 normal) V: not copious, easily coughed to tip of ETT for suction D: Technique: 1. Spontaneous breathing trial for 30 to 120 minutes a. if the rial is successful, patient will usually tolerate extubation b. if the trial is not tolerated, weaning should be delayed c. trials should take place daily until patient is ready to be extubated d. Trials should take place daily until patient is ready to be extubated 2. Alternate periods on ventilator and CPAP to condition respiratory muscles 3. Use pressure support to minimize ventilator-induced work of breathing E. Extubating F. Criteria for termination of wean 1. opposite of readiness to wean 2. perform early in the day 3. pt should be rested, aware and cooperative 4. have suction, o2 device and reintubation equipment close 5. elevate the head of the bed 6. suction well 7. extubate 8. monitor closely 7. Know principles of mechanical ventilation: what is respiratory rate, tidal volume, positive end-expiratory pressure (PEEP), fraction of inspired O2 (FiO2) 1. Tidal volume refers to the volume of air entering (inhaled) or leaving (exhaled) the lungs with each breath. a. When a ventilator mode uses a target tidal volume in adults, the settings should be in the range of 6-8 ml/kg ideal body weight in adults (The goal is to not exceed the plateau pressure of 30 cm of H2O in order to prevent barotrauma). b. The most common practice is to approximate tidal volume within 50 ml and then to adjust the effect. 2. To avoid barotrauma, minimal effective tidal volume should be used. 3. When the target is airway pressure, tidal volume may vary with compliance. Rate is the number of mechanical breaths delivered each minute. a. A mechanical breath cycle may be defined by a tidal volume target or by a pressure target. b. Set ventilator rates will be adjusted to achieve pH and PaCO2 goals. FiO2 that exceeds 0.5 for longer than 24 hr may result in oxygen toxicity 2. Inspiratory cycles vary as follows A. Volume cycled: pressure limited (volume-targeted) A present tidal volume is delivered unless a set pressure limit is reached, terminating the cycle. Ensures that tidal volume is not determined by compliance but has higher risk of barotrauma. B. Pressure cycled: volume limited (pressure targeted) A preset pressure is delivered unless a volume limit is reached, terminating the cycle. Allows more natural tidal volume with less risk of barotrauma Rate may have to adjusted to compensate for variable tidal volumes 3. PEEP prevents the return of intrapulmonary pressure to equal extrapulmonary pressure at the end of expiration: A. Effect is that of an incomplete expiration: increased functional residual volume (FRV) remains The result of increased FVR is twofold. 1. A greater number of alveoli are opened for a gas exchange throughout ventilatory cycle. 2. Additional alveoli are opened at peak inspiration because of tidal volume “stakced” on increased FRV B. Effect of increased alveolar ventilation is twofold: increased PaO2 without increase in FIO2, reduced atelectasis C. RISKS: Barotrauma due to hyperdistention and high intrapulmonary pressures, impedance of central venous return, resulting in lower cardiac output, most significant with low central pressure or right ventricular diastolic dysfunction, increased intracranial pressure D. Typical PEEP settings rage from 5 to 10 cm H2O. Higher peep(up tp 10-20 cm H2O) may be used with low compliance conditions such as ARDS 4. CPAP is functionally equivalent to PEEP CPAP is effectively PEEP without MV Pt must have independent inspiratory capability It has same risk and benefits of PEEP 5. Pressure Support reflects an augmentation of flow rate during spontaneous inspiration The result is to overcome resistance to flow through ventilator circuit (valves, corrugated tubing and narrow lumina), thus reducing spontaneous inspiratory effort or work of breathing. At Higher levels of pressure, it can provide full ventilatory support. MODES of Mechanical VENTILATION 1. Controlled mandatory ventilation: a patient received only set tidal volume at a set rate Patient cannot add spontaneous breaths. Sedation and of NM blockade will be required to reduce anxiety and prevent interference with ventilator function. Minute volume will be equal to the set rate x set tidal volume 2. Assist control (AC) ventilation: Patient will receive a set tidal volume at a set rate. Patient can add spontaneous breaths but will receive set tidal volume with the initiation of each spontaneous breath. The delivery of each spontaneous breath will not be synchronized with spontaneous breaths. Sedation may be required to prevent hyperventilation (hypocarbia) and ventilator desynchrony. Minute volume will be equal to (set rate + spontaneous rate) x set tidal volume 3. Intermittent mandatory ventilation (IMV or SIMV) : Patient will receive a set tidal volume at a set rate. Patient can add spontaneous breaths at own tidal volume The delivery of ventilator breaths may not be synchronized with spontaneous breaths (synchronized IMV). The delivery of ventilator breaths can be synchronized with spontaneous breaths (synchronized IMV). Minute volume will be equal to (set rate x set tidal volume) + (spontaneous rate x own tidal volume). Typically used with pressure support ventilation, which augments spontaneous breaths and minute volume 4. Pressure control ventilation: Patient will receive a set rate delivered up to a set pressure. Tidal volume will vary with each breath according to compliance, and minute volume may be adversely affected with poor compliance if the tidal volumes are very low. It may be used with inverse ratio ventilation: 1. inspiratory time is lengthened, and expiratory time is shortened 2. Barotrauma risk is reduced 3. Oxygenation may be improved. Pressure support Ventilation (PSV): pt triggers their own breath: ALL breaths are patient initiated. Ventilation determined solely by patient (no back up rate). Ideal weaning mode (used in SBTs and for prolonged periods). Most comfortable because it allows patient to control ventilation. Must monitor: Volumes (TV and MV) Ventilator cycles through PEEP and pressure support a. What are the risks of high peep, FiO2, tidal volume 6. Prescribe ventilator settings for newly intubated patients. Pg 510 Ventilator settings: Mode/rate/tidal volume/PEEP/FiO2 AC 14/450/+5/.1 (100% Assessment: auscultate for the following: Bilateral and equal distribution of normal breath sounds, adventitious sounds is the evidence of ETT cuff leak ETT position should not extend the distal tip beyond the level of the carina. a. ETT 22-cm mark even with lips is a good approximation for most adults b. chest xray, a tip of ETT should be 1-2 cm aove the carina. c. breath sounds should be audible bilaterally 7. Know what causes high and low pressure alarms High pressure alarms when proximal airway pressures exceed set limits: 1. secretion accumulation 2. pt counghing 3. spontaneous dyssynchrony 4. decreasing compliance 5. PNATHORAX 6. airway occlusion Low pressure alarms when promixal airway pressure does not reflect current ventilator function 1. disconnected tubing 2. ETT cuff leak Low volume alarms when volume returned to the ventilator is less than the set limit 1. may result from disconnecting tubing, or from ETT cuff leak 2. may result from decreased patient tidal volumes (shallow breaths) Low FIO2 alarms if below set FIO2 1. interruption in oxygen supply Apnea alarms if no spontaneous or mechanical breath detetected within a set time frame 1. pt apnea 2. mechanical failure 8. Describe static and plateau pressures on a ventilator Peak Pressure: is the pressure achieved during inspiration when the air is being pushed into the lungs and is a measure of airway resistance. Plateau pressure: is the statis pressure achieved at the end of a full inspiration. 25 to 30 cm H2O and less than 6ml/kg 9. Be able to adjust ventilator settings based on the patient's condition and AGB results. 10. Diagnostic criteria and treatment for pulmonary embolism, hypovolemic shock, pneumonia Pneumonia: Typical signs: fever, chills, leukocytosis, cough with or without sputum, sputum production, increased fremitus, DX: Chest Xray, CBC including differential WBC count Blood cultures x 3 Gram stain and culture of sputum Arterial blood gases or pulse ox Procalcitonin levels Tx: empiric antimicrobials PE: leadings cause of inhospital death, as a result of right ventricular failure Labs: VQ scan should be performed in all clinically stable patients ABG; Hypoxemia Hypcapnia Spiral CT/D dimer Pulmonary angiography when clinical data and ventilation-perfusion scan are contraindicated: Management: Supplement O2 IF fluids for those with hypotension and reduced CO2 Worsening hypercapnia with progressive obtundation is indication for intubation Heparin 80 u.kg/bolus followed by continuous infucion of 18 u/kg/hr to maintain a partial thromboplastin time (PTT) of 1.5-2 x normal; begin coumadin simultaneously to an INR of 2-3 Fibrinolytics/thrombolytics, PTT and PT must be <2 x normal Hypovolemic Shock: results from a loss of greater than 20% of circulating blood volume Causes: internal/external bleeding, burns, DKA, HHNK, Severe dehydration, LABS: decreased CO/Cl, CVP, PCWP, SVO2, increased SVR Management: Fluids, vassopressors, PRBCs if low hbg 11. Treatment protocols for patients with ARDS A. Clinical findings: Severe respiratory distress occurring during the course of one of the inciting events a. Severe respiratory distress b. respiratory distress often requires early institution of mechanical ventilatory assistance, refactoroy HYPOXEMIA is the classic finding. Symptoms: breathlessness, agitation, confusion, obtundation as oxygen delivery and uptake by tissue falls. LABS: ABG; PaO2/FiO2 ratio. If less than 300, then ALI; if less than 200, then ARDS Chest Xray: often shows evolving bilateral infiltrates (whited out) CT chest: heterogenous nature of the opacities TX: 1. first priority is identification and prompt treatment of the underlying cause. For example, sepsis, 2. Airway 3. intubate 4. circulation: fluids if hypotensive It is important to monitor peak and plateu pressures in mechanically ventilated patients tp prevent barotrauma, persistent breath to breath peak pressures greater than 45 cmH2O are a risk factor for barotrauma. To prevent barotrauma: reduce tidal volume to 6ml/kg, pressure cycles ventilation, 5. sedation 6. nutritional support: most pts need twice their usual daily caloric requirements to counteract the tremendous energy expenditure used in combating ARDS 7. risk of pulmonary barotrauma, including pneumothorax or pneumomediastinum is high with ARDS 8. sudden increases in ventilating pressure with desaturation in arterial oxygen tension indicated the need for immediate repeat chest xray for possible chest tube insertion 9. repeated physical and radiographic assessments of the lungs may be needed to rule out barotrauma in the mechanically ventilated patients with ARDS The mechanical ventilation protocol summary developed by the National institutes of heath:recommend maintaining PaO2 between 55 and 80 mmhg or SpO2 between 88% and 95% by adjusting FiO2 and PEEP. And pH between 7.30 and 7.45 in patients with ARDS by adjusting RR. Set initial TV 6ml/kg. Plateaus pressure <30 THREE main methods of weaning: Spontaneous breathing trial (SBT), (synchronized) Intermittent mandatory (SIMV) and pressure support ventilation (PSV) 12. How to initiate BIPAP and write appropriate orders for it 13. Asthma management and treatment including PEF 14. Management of COPD Cardinal symptoms: Dyspnea with exertion, chronic cough and sputum production LABS: Spirtimetry is the cornerstone a. expiratory flow rates are reduced. 1. early disease: reduction in small airway flow rates 2. Late disease: reduction in forced expiratory volume in 1 sc (FEV1). A measure of the potential for severe complications of COPD. 3. The most important measurement is the ratio of FEV1 and forced vital capacity: (FVC). * FEV1/FVC <70: indicates obstruction * FEV1/FVC 80-100 mild * FEV1/FVC 50-80 moderate * FEV1/FVC 30-50: severe * FEV1/FVC <30: very severe 4. Lung volume changes: a.Air trapping indicated by increases residual volume b. Increases total lung capacity, functional residual capacity, and residual volume are indicative of hyperinflammation. c. FVC may be reduced by air trapping d. The reduction in FVC is, on a percentage of a normal basis, less than the percentage reduction in predicted expiratory airflow. 5. Arterial blood gases and pulse OX 6. During acute exacerbation of COPD, hypoxemia, and acute hypercarbia 7. Chest Xray: air trapping, blebs and bullae, hyperinflation, dark lung fields,, increased AP diameter. MANAGEMENT: PAGE 405 1. smoking cessation 2. Nictoine replacement: eight week course is sufficient with little added benefit to longer use, 3. Bupropion (eg, Zyban, Wellbutrin) may also help avert weight gain associated with tobacco cessation 4. Varenicline (Chantix) 5. SECOND-LINE AGENTS: Clonidine Notriptyline: contraindicated in smokers with asthma, CVD, GI, glaucoma, prostate, seizure or thyroid disorders. Pharmacologic management: 1. Long-acting beta, agonists (LABA) and short acting Beta agonists (SABA) or short acting muscranic antagonists (SAMA) to improve FEV1 and symptoms 2. LABAS/long acting muscarinic antagonists (LAMA) significantly improved lung function, dyspnea, health status, and reduce exacerbations. 3. Inhaled corticosteroids (ICS)/LAMA are used for patients with moderate to severe COPD and frequent exacerbations. FEV1<60 needs ICS 4. ICS/LABA/LAMA improve lung function, symptoms in health status, and reduce exarbation 15. Know the definition of hypoxia/hypercapnia and causes of each 16. Causes of atelectasis 17. Ventilator adjustments for auto PEEP 18. Know about chest x-rays, which view would you order for an ICU patient who cannot go to X-ray suite (ie: portable xray views) a. Know where the carina is located on the chest xray: The trachea should be midline, displaced trachea can indicate thyroid enlargement or shift due to buildup of pressure. The carina should be between T4 and T6 and should be examined when the patient is intubated to ensure inflation of both lungs The right main bronchus is straighter than the left main bronchus: Aspiration PNA is suspected when the consolidation occurs in the right middle or lower lobe. The costophrenic angle should be sharp. 19. Describe the step by step process for Rapid Sequence Intubation (RSI) PAGE 112 in emergency book 1. Preparation, 2. Preoxygenation, 3. pretreatment, 4. paralysis and induction, 5. Positioning 6. placement of the tube, 7.postintubation management. 20. Identify medications used RSI Typical premedications include the following: midazolam, fentanyl, atropine, and lidocaine. Fentanyl: A dose of 1 to 3 µg/kg 3 minutes prior to induction is recommended. It is hepatically metabolized by oxidation and does not have an active metabolite. The most common adverse side effect associated with fentanyl is respiratory depression. ATROPINE: The dose for atropine is 0.01 mg/kg in adults. Lidocaine: It is recommended to administer lidocaine 3 minutes prior to RSI to blunt the increase in ICP. The typical dose of lidocaine is 1.5 mg/kg (common 100 mg), and it has a relatively quick onset of action . Propofol is a highly lipid-soluble, phenolic derivative, which is a GABA agonist and is used as an induction agent for RSI. The dosage of propofol used for induction in healthy patients is 1.5 mg/kg IV (common, 100-200 mg). 21. Know common doses of etomidate and succinylcholine. Be able to calculate those doses. Etomidate is an imidazole-derived sedative hypnotic that is a commonly used induction agent for RSI. Etomidate stimulates GABA receptors to block neuroexcitation and induce unconsciousness. The dosage range is 0.2 to 0.6 mg/kg (common, 20-50 mg), with the most common dose used being 0.3 mg/kg. The main advantages of etomidate are that it has minimal cardiovascular effects, decreases ICP, and does not cause histamine release.25 Etomidate also has a quick onset of action, short duration of action, and undergoes hepatic elimination Succinylcholine is the only depolarizing NMB currently available in the United States. Succinylcholine’s rapid onset and short duration of action make it an ideal agent for use in RSI. The dosage of succinylcholine is 1 to 2 mg/kg total body weight (common, 100 mg). In rare situations where intravenous access is not able to be obtained, succinylcholine may be administered intramuscularly at a dose of 3 to 4 mg/kg (common, 300 mg); however, the onset of action will be delayed to 3 to 4 minutes. Repeated doses (6 mg/kg) of succinylcholine should be avoided because of the potential development of a phase 2 block. Rocuronium is a nondepolarizing NMB that inhibits depolarization by antagonism of Ach receptors. The dosage of rocuronium is 0.6 to 1.2 mg/kg. Pharmacokinetics and adverse effect profiles must be considered when determining which agent to use for paralysis during RSI. Help understanding Aa gradient Pulmonary Diffusion Explained Clearly by MedCram.com’ https://www.youtube.com/watch?v=47u3-GamoII Hypoxemia: Diffusion A- alveolus a-aterial Aa gradient = [ (FIO2).(Patm-PH2o)- (PCO2?0.8)] -Po2 Normal: .21 (760 47) 40/0.8-86 .21 x 713 150-50-86= 14 normal Another way: Age/4+4= 40/4+4+ 14 If diffusion problem, FIO2 will go up, Diffusion: responds to 100% oxygen Increased Aa gradient Fibrosis/exercising, red blood cells are going through at larger rate. Week 8-Sedation and Pain Management Key Concepts Pain and Sedation 1. Be familiar with the recommendation for ICU sedation in the Society of Critical Care Medicine guideline. Apply that guideline to patients with trauma, on ventilation, with hypotension. 2. Discuss the diagnosis and treatment of delirium. Contrast that with dementia 3. Describe the CDC guide for managing acute pain and opioid sensitive prescribing. 4. Differentiate the different types of pain and the best medications to treat them. 5. Be familiar with ketamine for procedure sedation, the appropriate dose, and required monitoring. 6. What medication could you use for a laceration repair if the patient is allergic to lidocaine? 7. Describe why a patient receiving IV opioids might develop chest wall rigidity and how to treat it. 8. What are antagonist drugs for benzodiazepines and opioids Week 9 Key Concepts-Infections, Antimicrobials, and Antifungals 1. A good understanding of the gram positive and gram negative bacteria is very helpful in understanding how to select antibiotics to treat the different infections. 2. A general idea about what class of antibiotics treat gram positive and gram negative (Penicillins better for gram positive) 3. Know the different types of penicillins and what they treat and Mechanism of action 4. Know the different generations cephalosporins and what they treat. 5. Be familiar with the different antibiotic classes (fluoroquinolones, macrolides, tetracyclines, vancomycin) and the types of bacteria they are effective against. 6. Be familiar with the common side effects of each class of antibiotics. 7. Distinguish between treatment for hospital acquired pneumonia (HAP) and community acquired pneumonia (CAP). 8. Common antibiotic choices to treat urinary tract infections, community acquired pneumonia, pyelonephritis, (epocrates is a good resource for this information)-Also, How long to treat 9. Describe the relationship between penicillins and cephalosporins. If a patient is allergic to penicillins, can you prescribe them cephalosporin safely. 10. Review the sepsis guidelines and what broad spectrum antibiotic coverage would include. 11. Appropriate antibiotic treatment for MRSA infections 12. Work up and appropriate treatment for bacterial meningitis. 13. Be able to choose an appropriate antibiotic treatment based on a bacterial sensitivity report 14. Appropriate antibiotic treatment for pelvic inflammatory disease. 15. What is empiric antibiotic selection? What factors do you consider when making empiric antibiotic selections? Week 10 Key Points-Acute Renal Failure, Fluid, and Electrolyte Imbalance 1. Differentiate between the three types of kidney injury – prerenal, intra-renal, post-renal. Understand causes of each and prescribe appropriate management plans for each type. 2. Clinical symptoms of and treatment plans for hyper and hypokalemia 3. Clinical symptoms of and treatment plans for hyper and hypomagnesemia 4. Clinical symptoms of and treatment plans for hyper and hyponatremia 5. Clinical symptoms of and treatment plans for hyper and hypocalcemia-trousseaus/chvosteks sign 6. Complications related to the administration of 3% normal saline 7. Common electrolyte imbalances experienced by patients with end stage renal disease 8. Treatment of a patient with heparin induced thrombocytopenia and renal failure. 9. Medication management of a patient with bilateral renal artery stenosis 10. Signs and symptoms of acid-base disorders 11. Best agent for fluid resuscitation. 12. Know the about each type of fluid and when to use as well as what to monitor for while in use (D5W, D5 0.45% NS, 0.45% NS, D5 0.9% NS, 0.9% NS, Lactated Ringer, 3% saline, etc)-How much fluid actually stays in the vascular space Week 11 Key Points- Diabetes and Diabetic Emergencies 1. 1. Know the onset and duration of action of regular and basal insulins. Be able to provide instructions to patients regarding their insulin dosing based on this information 2. 2. Adjust insulin doses based on patient blood sugar readings over time. 3. Diabetes management in the hospitalized patients 4. 3. Provide instructions for blood sugar monitoring and insulin administration when patients have nausea / vomiting / limited oral intake / sick days 5. 4. Diagnostic criteria for diabetes and common initial medications prescribed. Medications specifically for high risk patients such as patients with cardiovascular disease 6. Most common complications of diabetes 7. 5. Differentiate between diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic syndrome (HHS). (labs, diagnostics, and treatment) 8. 6. Common side effects of metformin. Potential interaction of metformin with other medications and dyes. Management of a patient taking metformin with a planned procedure requiring IV dye. 9. 7. Complete patient treatment diabetic ketoacidosis (DKA) including IV therapy, insulin, electrolytes, diagnostics, labs. Be able to interpret labs associated with DKA (serum osmolality, anion gap)