Oxygenation, Ventilation And Ventilator Management In The First 24 Hours
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    Oxygenation, Ventilation And Ventilator Management In The First 24 Hours Oxygenation, Ventilation And Ventilator Management In The First 24 Hours Presentation Transcript

    • Oxygenation, Ventilation, and Ventilator Management in the First 24 Hours Robert L. Huck, M.D.
      • Financial disclosures: Up to my ___ in alligators, I’m just trying to help drain the swamp (i.e., none)
      • A “nuts and bolts” talk (more “nuts” than “bolts”?, I’ll leave you to decide)
      • You getting my biases, and those of your local pulmonary support group (but no we are not a 12 step program)
      • Hopefully, knowing our thinking will smooth transitions
    • Common In Hospital Etiologies for Respiratory Failure
      • Excess narcotics or sedatives
      • In hospital aspirations
      • Cardiopulmonary arrest
      • COPD
      • CHF
      • Pneumonia
      • Drug overdose
      • Asthma
      • Pancreatitis
      • Stroke
      • Sepsis
    • Measures of Oxygenation
      • Arterial oxygen saturation (SaO2)
      • Arterial oxygen tension (paO2)
      • Alveolar to arterial oxygen difference (A-a gradient) PAO2=(FIO2x[Patm-PH2O])-(PaCO2/R)
      • PAO2/FIO2
      • A/a oxygen ratio
      • Oxygenation index ([{MAPxFIO2}/PaO2]x100)
    • Mechanisms of Hypoxemia
      • Hypoventilation
      • Ventilation/perfusion mismatch
      • Right to left shunt
      • Diffusion limitation
      • Decrease inspired oxygen tension
    • Monitoring of Oxygenation
      • Clinical: subjective dyspnea, cyanosis, mental status changes (usually restless- ness, agitation, or confusion, particularly in the elderly)
      • Pulse oxymetry
      • Arterial blood gases
    • Pulse Oxymetry
      • Arterial oxygen saturation is physiologically the more important number
      • O2 Content=(1.34 ml/gm x Hgb gm/dl x SaO2) + (0.0031x PaO2)
      • Accuracy:
        • Best in normal or near normal range
        • +/- 2% in Caucasians, +/- 4% in blacks
    • Pulse Oxymetry
      • Potential sources of error:
        • Abnormal hemoglobins: carboxyhemoglobin, methemoglobin
        • Hypoperfusion
        • Hypothermia
        • Anemia
        • Venous congestion
        • Pigmentation
        • Nail polish
        • Vital dyes (e.g. methylene blue)
    • Monitoring Oxygenation
      • Arterial blood gases
      • Effected by temperature
      • Provides information on ventilation and acid base balance as well as oxygenation
      • Relationship of PaO2 and SaO2: the oxyhemoglobin dissociation curve
    •  
    • Monitoring of Ventilation
      • Arterial blood gases
      • End tidal CO2 monitors (a complicated subject but useful for trending)
      • CO2 detectors
        • Useful for confirming ET placement
        • Requires perfusion
    • Indications for Mechanical Ventilation
      • Refractory hypoxemia
        • pO2 <55 on supplemental oxygen (usually 100% NRB mask)
        • Alveolar to arterial oxygen gradient >450 on FIO2 =1.0
        • paO2/pAO2 <0.15
      • Inadequate ventilation and respiratory acidosis (pH<7.23 and decreased level of consciousness)
      • Non sustainable work of breathing
        • Respiratory rate > 35-40 breaths per minute
        • Marked use of accessory muscle
        • Metabolic acidosis, i.e. lactic acidosis (especially if due to respiratory muscle work (e.g. asthma with normal pCO2 and decreased pH)
        • RR<10, NIFM < -30 cm H2O, Vital Capacity < 1L or < 10 ml/kg
    • Refractory Hypoxemia?
      • Remember 100% by NRB mask does not equal 100% FIO2
      • The true FIO2 depends on both flaps being in place, seal, and the patient’s inspiratory flow rate and entrainment of room air. You can try increasing the O2 flow rate (“oxymask” or mask plus nasal prongs) or O2 reservoir
    • Indications for Mechanical Ventilation
      • Refractory hypoxemia
        • pO2 <55 on supplemental oxygen (usually 100% NRB mask)
        • Alveolar to arterial oxygen gradient >450 on FIO2 =1.0
        • paO2/pAO2 <0.15
      • Inadequate ventilation and respiratory acidosis (pH<7.23 and decreased level of consciousness)
      • Non sustainable work of breathing
        • Respiratory rate > 35-40 breaths per minute
        • Marked use of accessory muscle
        • Metabolic acidosis, i.e. lactic acidosis (especially if due to respiratory muscle work (e.g. asthma with normal pCO2 and decreased pH)
        • RR<10, NIFM < -30 cm H2O, Vital Capacity < 1L or < 10 ml/kg
    • Indications for Mechanical Ventilation
      • Any of the indications above and you are thinking: “I can’t fix this any time soon.”, think intubation and invasive mechanical ventilation
      • If you are thinking: “I can fix this if I can just buy enough time.”, then think- “non invasive ventilation!” ( assuming no contraindications to NIPPV)
    • Indications for NIPPV
      • NIPPV is primarily a temporizing measure for ventilatory support.
      • Buying time for other therapies (i.e. diuretics, bronchodilators, etc.) to work
      • NIPPV generally augments, but does not replace, spontaneous ventilatory efforts
    • Indications for Non-Invasive Ventilation
      • Alert, cooperative patients not requiring emergent intubation with a need for relatively short term ventilatory support
      • Problems known to respond to NIPPV
        • COPD exacerbations with moderate hypercapnea(pCO2>45, <100 mmHg), and acidosis (pH <7.3, >7.00-7.10)
        • Acute cardiogenic pulmonary edema
        • Hypoxemic respiratory failure (other than ARDS)
        • Post-extubation respiratory failure
    • Contraindications to NIPPV
      • Cardiac or respiratory arrest
      • Inability to cooperate, protect airway, or clear secretions
      • Significantly impaired consciousness(except possibly COPD)
      • Non respiratory organ failures
      • Facial trauma, surgery or deformity
      • High aspiration risk (e.g., the pregnant asthmatic)
      • Prolonged ventilatory support anticipated
      • Recent esophageal anastomosis
    • NIPPV Interfaces
      • In acute care settings, generally start with a full face mask
      • Most patients with acute respiratory failure are mouth breathers. Nasal ventilation results in a large oral air leak
      • Normally the nasal airway contributes 50% of total airway resistance
      • Full face masks make monitoring and management of aspiration more difficult
      • Patients on chronic CPAP or BiPAP may do better with their usual kind of mask.
    • NIPPV Modes
      • Mostly at this institution NIPPV equates to bilevel positive airway pressure with a guaranteed back up respiratory rate.
      • Can be used with assist control mode of a standard ICU ventilator (for greater assurance of minute ventilation)
      • Can be used with pressure support ventilation with ICU ventilator (for better patient synchrony and comfort)
    • NIPPV Monitoring
      • Monitor: Level of consciousness, vital signs, and ABG’s.
      • Improvement should be apparent in the first 30-120 miuntes
      • If no improvement, proceed to endotracheal intubation
    • Advantages of NIPPV
      • Lower mortality in acute respiratory failure (primarily COPD and CHF)-probable selection bias for less severe patients
      • Reduced nosocomial infection
      • Decrease length of stay
      • Better patient comfort
    • Endotracheal Intubation
      • The patient is going down the tube, so you decide the tube is going down the patient.
      • How to intubate is another talk
      • Fast forward - the patient is intubated, now what?
      • A couple of caveats from the intubation process
        • Do not use succinylcholine, a depolarizing neuromuscular blocker, for hyperkalemic patients or patients with seizures
        • Etomidate causes acute adrenal suppression
    • Goals of Mechanical Ventilation: Clinical
      • Relieve respiratory distress
      • Improve hypoxemia
      • Alleviate respiratory acidosis
      • Reverse ventilatory muscle fatigue
      • Reduce systemic or myocardial oxygen consumption
      • Permit sedation or neuromuscular blockade
      • Prevent or improve atalectasis
      • Stabilize the chest wall
    • Goals on Mechanical Ventilation: Physiologic goals
      • Support gas exchange: arterial oxygenation and alveolar ventilation
      • Reduce metabolic cost of breathing by unloading respiratory muscles.
      • Avoid ventilator associated lung injuries
    • Ventilator Set Up
      • Things you need to specify:
      • Ventilator mode (more on this coming)
      • FIO2 – start with 100%, unless you are sure the patient’s lungs are normal, e.g. drug overdose, then 40% is OK
      • Respiratory rate
      • End expiratory pressure.
      • Use the ventilator “bundle” order sheet. It will prompt you.
    • Ventilator Set Up: Modes
      • Poll: Volume control versus Pressure control?
      • Available modes:
        • Volume control: A/C, SIMV, CMV
        • Pressure control: PCV
        • Flow limited: PSV (pressure support ventilation)
        • Time limited: Home ventilators
    • Ventilator Set Up: Modes
      • Each mode has things you need to specify
      • In general, use the mode you trained with, and are comfortable using
      • Our Bias: If you are starting volume controlled ventilation for acute respiratory failure, start with Assist Control Ventilation.
        • Advantage: Minimizes WOB. The patient only has to trigger the ventilator.
        • Disadvantage: Every breath is a positive pressure breath, which impairs venous return.
    • Ventilator Set Up: Modes
      • SIMV: synchronized intermittent mandatory ventilation
        • Allows spontaneous breaths between mandatory machine breaths. Mandated breaths are “synchronized” to be delivered when the patient is trying to inspire.
        • Originally this was a “weaning” mode
        • Advantage: The patient can set minute ventilation in excess of set parameters, less muscle atrophy
        • Disadvantage: Patient does all the work of spontaneous breaths plus ventilator imposed work
        • The acute concern is respiratory muscle fatigue
    • Ventilator Set Up: Modes
      • SIMV: synchronized intermittent mandatory ventilation
        • A/C vs. SIMV: If goal in the first 24 hrs is to reduce work of breathing and respiratory muscle work and fatigue, A/C is superior
        • Effect on work of breathing is really only different with SIMV if the patient breaths above the set ventilator rate.
    • Ventilator Set Up: Modes
      • Volume controlled ventilation:
        • FIO2
        • Mode: A/C, SIMV
        • Tidal volume (usually 10ml/kg ideal weight, realize normal spontaneous tidal volume is 5-6ml/kg)
        • Respiratory rate
        • Positive end expiratory pressure.
    • Ventilator Set Up: Modes
      • Pressure control ventilation vs. Volume controlled ventilation
      • Volume controlled ventilation delivers a set minute ventilation, unless pressure limits are exceeded, then some portion of the set minute volume is “dumped” (which takes time, so actual airway pressure may exceed desired airway pressures trying to deliver the preset volumes)
      • How much volume actually gets delivered depends on the patient’s airway resistance and lung compliance, theoretically minute ventilation is “guaranteed.”
    • Ventilator Set Up: Modes
      • Volume controlled ventilation vs. Pressure controlled ventilation
        • Pressure controlled ventilation increases airway pressure to the preset inspiratory pressure.
        • The actual tidal volume delivered depends on the patient’s airway resistance and lung compliance. Actual minute volume delivered can vary as these change.
        • Advantage: Limits peak airway pressures and possible barotrauma
        • Disadvantage: Minute ventilation may be inadequate for metabolic demands
    • Ventilator Set Up: Modes
      • Pressure support ventilation:
        • Also originally a “weaning” mode
        • Requires a patient with intact respiratory drive and spontaneous breathing, i.e. will not ventilate an apneic patient.
        • Augments spontaneous tidal volume, depending on the patients airway resistance and lung compliance
        • Advantage: Less asynchrony with the ventilator and improved patient comfort
    • Ventilator Set Up: Modes
      • Time limited ventilation:
        • Delivers preset flow for preset time. Tidal volume depends on airway resistance and lung compliance.
        • Often used in home ventilators: rugged , cheap, simple, dependable, but hospital RT’s (and pulmonary doc’s) are often not familiar with them
        • If home ventilated patient has respiratory problems on their ventilator, take them off theirs and put them on ours
        • You probably will not see these patients
    • Ventilator Set Up: Modes
      • Pressure control ventilation:
        • FIO2
        • Inspiratory pressure (IPAP) (as in BiPAP)
        • Expiratory pressure (EPAP) (EPAP =PEEP)
        • Delta P, the change in pressure. This must equal IPAP-EPAP
        • Slope (how fast IPAP is achieved), usually, .1-.3, determines I:E ratio
        • Respiratory rate
    • Ventilator Set Up: Modes
      • Pressure control ventilation:
        • Once ventilation is started, you need to assess if the tidal volume and minute ventilation that results are reasonable for the patient’s situation and metabolic demands
        • Check ABG’s to be sure
    • Ventilator Set Up: Modes
      • Issues you do not have to specify, but RT has to set or cope with that you need to be aware of
        • Triggering sensitivity and relation to end expiratory pressure
        • I:E ratio
        • Inspiratory flow rates and patterns (square wave vs. accelerating or decelerating flow)
        • These effect airway pressures and patient synchrony with the ventilator
        • You need to listen , if RT says there is a problem with your ventilator settings (e.g., If the patient does not have adequate time to exhale between breaths you are headed for trouble)
    • Tips on Starting Mechanical Ventilation
      • Remember , the respiratory therapists and ICU nurses are your friends ! They really do, do all this, all the time. Listen , to them! If you disagree, explain your reasoning, they will (believe it or not) listen to you! If you can’t articulate it, think again!
      • Check the chest xray! (The crisis is not “over” just because the tube is in!)
      • Positive pressure ventilation initially reduces venous return, cardiac output, and blood pressure! Be prepared! (especially, if the patient was possibly intravascularly volume depleted prior to intubation). It is not necessarily “sepsis”, just because the blood pressure goes down after intubation. Start with IV fluids.
    • Respiratory Distress on Mechanical Ventilation
      • The tools you need: a stethoscope, a chest xay, and your brain
      • Disconnect patient from ventilator and assist ventilation with bagging.
      • If the patient is easy to ventilate with bagging and this solves the distress = ventilator problem
      • If the patient hard to ventilate with bagging and still in distress = patient problem
    • Respiratory Distress on Mechanical Ventilation: Ventilator Problems
      • Inadequate ventilator settings:
        • Inadequate inspiratory flow rate or pressure- previously the most common cause. Rarer now with modern ventilators with high flow rates and ability to meet patients inspiratory flow demands. Dyspneic patient have high inspiratory flow demands, even if their own spontaneous tidal volumes and minute ventilation are inadequate.
        • Can be suspected from ventilator graphic displays, take your cues from the respiratory therapists.
    • Respiratory Distress on Mechanical Ventilation: Ventilator Problems
      • Inadequate FIO2- should be obvious from oxygen saturation or ABG’s
      • Inadequate tidal volumes - The patient may want higher than set tidal volumes. This is particularly true for neuromuscular patients and probably involves intrapulmonary stretch receptors. Given the possibilities of “volutrauma”, increasing tidal volume is not necessarily good for them, but short term (i.e. a few hours) it is ok to increase the tidal volume until they are satisfied (and call us in the morning, unless airway pressures are excessive)
    • Respiratory Distress on Mechanical Ventilation: Ventilator Problems
      • Incorrect positive end expiratory pressure, especially due to intrinsic PEEP
      • Incorrect trigger sensitivity (the patient has to work too hard to trigger the next breath)
      • Example: Intrinsic PEEP +10 cm with trigger sensitivity – 2cm (from atmospheric=0), patient effort to trigger next breath = -12cm
      • Remedy: Measure intrinsic PEEP, set ventilator PEEP at 80% of intrinsic PEEP, and set trigger sensitivity at -2 cm below set PEEP ( in this case +6 cm relative to atmospheric. Patient effort to trigger next breath -4cm
    • Respiratory distress on Mechanical Ventilation: Ventilator factors
      • Ventilator circuit leak
      • Ventilator malfunction
      • If the patient is OK off the ventilator, being assisted with bagging, these are the RT’s problems. Have them fix them or get a new ventilator.
      • Your problem: Solved!
    • Respiratory Distress on Mechanical Ventilation: Patient Problems
      • Airway problems (increased peak airway pressure – plateau pressure, meaning airway resistance has increased, parenchymal compliance is not changed) (i.e., the airways have a problem, the lung is no stiffer)
      • Pulmonary parenchymal problems-(peak airway pressure- plateau pressure unchanged or decreased, meaning air way resistance is unchanged, parenchymal compliance has decreased) (i.e., more pressure required to create the same change in volume with no increase in airway resistance = the lung is stiffer)
      • Extrapulmonary problems, i.e. the problem is around the lungs but not in them.
    • Respiratory Distress on Mechanical Ventilation: Endotracheal Tube Problems
      • Airway Problems:
      • Endotracheal tube: (It’s the tube, stupid!)
        • Patient is biting the tube (bite block, paralysis)
        • The tube is occluded with secretions, foreign body, or blood (try forcing it out the distal end with a suction catheter or a stylette or “tube changer”, or calling for bronchoscopy. Extubate and reintubate, if the problem is acute, but you risk losing a secure airway)
        • Cuff leak, deflation, or rupture (in this case airway resistance usually drops suddenly, but the air leak is usually obvious)
        • Increased resistance from heat, moisture exchanger, or in line CO2 monitor ( removing the patient from the ventilator and bagging should indicate it is a ventilator circuit problem)
    • Respiratory Distress on Mechanical Ventilation: Patient Problems
      • Airway Problems: If it is not the tube, the patient is the one with the problem.
      • Bronchospasm: (remember the stethoscope?)
      • The lower airway is occluded with secretions, blood, or a foreign body (OK, go ahead and call us for bronchoscopy [{damn it!}])
    • Respiratory Distress on Mechanical Ventilation: Patient Problems
      • Pulmonary parenchymal problems:
      • ET tube has migrated into the right mainstem. (Oh, wait, there is that stethoscope again, and when that “fails” there is always a chest xray) (Oops, it the tube again, stupid!)
      • OK, the tube is really OK, it’s the patient that really has the problem
    • Respiratory Distress on Mechanical Ventilation: Patient Problems
      • True pulmonary parenchymal problems:
      • Pneumonia
      • Atalectasis
      • Pulmonary edema (cardiogenic or non-cardiogenic)
      • Aspiration
      • Pulmonary Embolism
    • Respiratory Distress on Mechanical Ventilation: Patient Problems
      • “ Extrapulmonary Problems”:
      • Pneumothorax: (suspect with acute changes in oxygen saturation, and airway and plateau pressures) (back to the stethoscope and chest xray again)
      • Pleural effusion
      • Abdominal distension: ascites, gastic distension, ileus, pancreatitis, obesity, etc.
      • Delirium, pain, anxiety, fever, acute CNS event, acidosis (increased respiratory drive)
    • Respiratory distress on the Ventilator: Paralysis
      • Paralysis is not the same, or part of, sedation!
      • If you need paralysis to control agitation times one, until other measures, (e.g. propofol) can work, OK.
      • If you think paralysis is required to maintain ongoing ventilatory support, you need to be calling us. Paralysis to maintain ventilation is a last resort!
      • Paralysis (as opposed to sedation) is usually only required in ARDS (and maybe severe asthma), where chest wall relaxation is required to reduce inspiratory pressures. (my opinion)
    • Respiratory Distress on the Ventilator: Paralysis
      • Be sure you know the patient’s ABG, ventilator settings, and minute ventilation first!
      • Do not paralyze for agitation on an IMV of 2 bpm
      • Do not paralyze for tachypnea with a pH of 7.00, a pCO2 of 10, and a minute ventilation of 25 L/min in order to start or continue ventilator settings delivering a minute ventilation of 10 L/min
    • … you might need a pulmonologist
      • I do not think I can ventilate this patient unless I keep them paralyzed…
      • The patient is asthmatic (or has COPD) with high airway pressures and inability to ventilate (may need “permissive hypercapnea”)…
      • You always use volume controlled ventilation, its not working, and and RT is suggesting possible PCV….
    • … you might need a pulmonologist
      • The patient is on the ventilator and you can not achieve adequate oxygenation…
      • There is a problem with the endotracheal tube …
      • You think the patient is developing ARDS and airway pressures are high and oxygenation is low…
      • The patient is hemodynamically unstable, and is not responding to IV fluids …
    • … you might need a pulmonologist
      • I could go on (and on, and on, and on …), but you get the idea
      • We need (and love) our sleep, but if in doubt call us.
      • Thank you!
    •