Monitoring and Management of Ventilatory Support Educational Objectives • List the reasons for monitoring the patient receiving ventilatory support • List and describe the methods of evaluating patient oxygenation • List and describe the methods of evaluating patient ventilation • List and describe the ventilator parameters monitored • List the normal hemodynamic values • Describe the effects that mechanical ventilation may have upon the hemodynamic parameters Reasons for Monitoring the Patient 1. Establish baseline measurements 2. Allow trending to be observed in order to document progress or lack of progress 3. Determine efficacy of treatment in order to modify as needed 4. Determine limits of alarm parameters Evaluation of Oxygenation – is There a Problem? • Physical Findings – Heart rate – Respiratory rate – Work of breathing • Use of accessory muscles • Retractions Evaluation of Oxygenation – is There a Problem? Physical Findings – Cyanosis • Peripheral • Central or circumoral (surrounding the mouth) – Level of consciousness/mental status • Confusion • Drowsiness • Anxiety Evaluation of Oxygenation – is There a Problem? Laboratory Findings – Arterial blood gases • PaO2 • SaO2 (measured or calculated?) • Hemoglobin (Hb)/Hematocrit (Hct) • Total oxygen content (CaO2) – Level of consciousness/mental status • Confusion • Drowsiness • Anxiety – Pulse oximetry – Lactic acid levels Determine Cause of Hypoxemia CO-Oximetry Results – Oxyhemoglobin (HbO2) – Carboxyhemoglobin (HbCO) – Methemoglobin (MetHb) – Hemoglobin (Hb)/Hematocrit (Hct) Determine Cause of Hypoxemia Laboratory Findings – Oxygen consumption (O2) • Normal value – 250 mL/min • Determined by Fick Equation Where is cardiac output, CaO2 and are arterial and mixed venous O2 content • Increase in oxygen consumption necessitates increase in oxygen delivered Determine Cause of Hypoxemia – Alveolar-arterial Gradient [P(A-a)O2] • Normal value – 5 to 15 mm Hg while breathing room air; increases to 100 to 150 mm Hg while breathing 100% oxygen • Determined by subtracting arterial value from arterial blood gas result from alveolar value using alveolar air equation Determine Cause of Hypoxemia – Arterial to Alveolar Oxygen Ratio (PaO2/FIO2) • Normal Value – 400 to 500 mm Hg while breathing room air • Used to define acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) – PaO2/FIO2 < 300 mm Hg in ALI – PaO2/FIO2 < 200 mm Hg in ARDS Determine Cause of Hypoxemia Radiologic Findings – Consolidation – Fluid – Free air Management Options – FIO2 • If FIO2 < 0.6, increase oxygen concentration; if no PEEP is employed, may add 5 cmH2O of PEEP first • If FIO2 > 0.6, consider reducing as soon as patient’s condition permits to avoid complications Management Options – FIO2 Titration of Oxygen Level – If the patient’s oxygenation status is unknown or critical, always start ventilatory support with an FIO2 of 1.0 – General goal – maintain PaO2 between 60 and 80 mmHg or SpO2 greater than 90% – Determination of desired PaO2 Desired PaO2 = Desired FIO2 x Actual PaO2 FIO2 (Actual) Management Options – FIO2 – General guideline for reduction of FIO2 • Decrease in increments of 5 to 10% • Follow each reduction by drawing arterial blood gases or oximetry; allow at least fifteen minutes after the change for equilibration of blood Management Options – PEEP Positive End Expiratory Pressure (PEEP) Maintenance of baseline pressure above atmospheric level • Minimum PEEP – Least amount of PEEP necessary to achieve and maintain a PaO2 of at least 60 mmHg Management Options – PEEP • Optimal PEEP – The level of PEEP at which oxygen delivery is maximized while minimizing hemodynamic side effects – Generally only employed on patients requiring > 10 cm H2O Management Options – PEEP Method for Determination of Optimal PEEP – Determine baseline values of blood pressure, mixed venous oxygen level, arteriovenous oxygen content difference, PaO2, static compliance, and cardiac output – Increase level of PEEP in increments of 2 cmH2O, measuring values at each increment – When a decline in oxygen delivery is observed, the optimal PEEP has been exceeded – Return PEEP level to previous increment Management Options – PEEP General Guidelines for Reduction of PEEP – Decrease in increments of 2 cm H2O – Follow each reduction by drawing blood gases or oximetry; allow at least fifteen minutes after the change for equilibration of blood – Reduction of PEEP to zero prior to extubation may be neither necessary nor advantageous Management Options – Tidal Volume Increasing Tidal Volume (VT) may be used for recruitment of alveoli if hypoventilation contributes to hypoxemia Normal Value – 6 to 12 mL/kg IBW Management Options – Inspiratory Time Prolongation of inspiratory time to a point where inspiratory time exceeds expiratory time Normal I:E ratio – 1:1.5 to 1:2 Management Options – Inspiratory Time Principle of Use – Increase in inspiratory time (TI) causes increase in – Increase in aids in maintaining integrity of alveoli and recruiting atelectatic alveoli – Associated with improvement in – Associated with improvement of PaO2 in patients with ARDS Management Options – Bronchial Hygiene • Postural drainage • Percussion • Adequate humidification • Ambulation, sitting up, turning patient Management Options – Patient Positioning • Ambulation, sitting up helpful in improving oxygenation • Turning patient from side to side aids in bronchial hygiene Management Options – Patient Positioning Prone Positioning – May result in dramatic improvement in oxygenation in patients with ARDS and ALI – Care must be taken to ensure tubes and lines are not displaced during turning – May improve and reduce shunting by removing pressure of the heart on the dorsal regions Evaluation of Ventilation – Physical Findings Breathing Patterns – Apnea – Tachypnea – Bradypnea – Abnormal breathing patterns Work of Breathing – Use of accessory muscles – Retractions Evaluation of Ventilation – Physical Findings Heart Rhythms – Abnormal rhythms – Tachycardia – Bradycardia Chest excursion Altered Mental State – Anxiety – Confusion – Combativeness – Somnolence Evaluation of Ventilation – Diagnostic Findings Arterial Blood Gases – Increased PaCO2 – Decreased pH – Decreased PaCO2 Bedside Spirometry Results – Negative inspiratory force (NIF) – < -20 cmH2O – Spontaneous tidal volume – < 5 mL/kg IBW – Vital capacity – < 10 mL/kg IBW Evaluation of Ventilation – Determine Cause of Problem Hypoventilation – Inadequate alveolar ventilation – A = (VT – VDS) (f) – Increase in physiologic dead space – VD/VT = (PaCO2 – PECO2)/PaCO2 Evaluation of Ventilation – Determine Cause of Problem Increase in Carbon Dioxide Production – Stress – Shivering – Pain – Asynchrony with ventilator – High carbohydrate diet Evaluation of Ventilation – Determine Cause of Problem Change in Lung and Chest Mechanics – Compliance – C = ∆V/∆P • ∆V = VT Corrected for Tubing Compliance • ∆P = Pplat – PEEP Causes of decreased lung compliance – Atelectasis – Pulmonary edema – ALI/ARDS – Pneumothorax – Fibrosis Evaluation of Ventilation – Determine Cause of Problem Causes of decreased thoracic compliance – Obesity – Pleural effusion – Ascites – Chest wall deformity – Pregnancy Evaluation of Ventilation – Determine Cause of Problem Cause of increased lung compliance • COPD Evaluation of Ventilation – Determine Cause of Problem Causes of increased thoracic compliance – Flail chest – Loss of chest wall integrity – Change in patient position Evaluation of Ventilation – Determine Cause of Problem Change in Lung and Chest Mechanics – Airway Resistance – RAW = ∆P/∆ • ∆P = (Ppeak – Pplat) • ∆ = flow Evaluation of Ventilation – Determine Cause of Problem Causes of increased resistance – Bronchospasm – Mucosal edema – Secretions – Excessively high rate of gas flow – Small endotracheal tube – Obstruction of endotracheal tube – Obstruction of the airway Evaluation of Ventilation – Determine Cause of Problem Causes of decreased resistance – Bronchodilator administration – Decrease in flow of gas – Administration of bronchial hygiene Evaluation of Ventilation – Determine Cause of Problem • Loss of Muscle Strength/Neurological Input – Rapid Shallow Breathing Index (RSBI) • Indication of whether patients have the ability to breathe without ventilatory support Evaluation of Ventilation – Determine Cause of Problem Loss of Muscle Strength/Neurological Input – Rapid Shallow Breathing Index (RSBI) • f/VT – If < 100 breaths/min/L, patient has ability to breathe without ventilator – If > 100 breaths/min/L, patient will likely not be able to sustain spontaneous breathing – Maximal inspiratory pressure – Maximum voluntary ventilation Evaluation of Ventilation – Management Options Increase Alveolar Ventilation – Increase in Mechanical Tidal Volume • Normal Volume – 6 to 12 mL/kg IBW • Most direct way to change alveolar ventilation • Should normally not exceed 12 to 15 mL/kg IBW • Associated with increase in peak inspiratory pressure which has increased risk of trauma to lung Evaluation of Ventilation – Management Options – Increase in spontaneous ventilation • More advantageous to patient than increasing mechanical tidal volume • Augmentation by pressure support mode helps overcome resistance of ventilator circuit and artificial airway Evaluation of Ventilation – Management Options Increase Alveolar Ventilation – Increase in Mechanical Rate • Normal Value – 12 to 18 Breaths per Minute • Should Normally not Exceed 20 Breaths per Minute • Prediction of Desired Rate New rate = Evaluation of Ventilation – Management Options Decrease Carbon Dioxide Output (Production) – Medicate patient to relieve pain, stress, and prevent asynchrony, decreasing work of breathing – Maintain patient’s temperature within normal range – Provide appropriate nutrition Evaluation of Ventilation – Management Options Treat Underlying Pulmonary Pathophysiology Maintain airway in patent state – Prevent accumulation of secretions in airway – Use properly sized artificial airway – Prevent occlusion of airway by patient; use bite block Considerations in Management – Permissive Hypercapnea Allowing PaCO2 level to remain elevated above 45 mmHg • Purpose – Maintain plateau pressure at an acceptable level (< 30 cm H2O) by decreasing tidal volume to less than 6 mL/kg and increasing respiratory rate, thereby minimizing trauma and cardiovascular side effects Considerations in Management – Permissive Hypercapnea Method – Decrease tidal volume and increase respiratory rate, while maintaining minute volume – If PaCO2 increases and pH decreases, either permit normal metabolic compensation or administer medications to maintain level at 7.25 to 7.35 – Institute gradually to allow PaCO2 to increase gradually over hours or days Considerations in Management – Permissive Hypercapnea Relative Contraindications or Cautions – – – – – – – Presence of cardiac ischemia Presence of pulmonary hypertension Compromised left ventricular function Right heart failure Head trauma Intracranial disease Metabolic acidosis Considerations in Management – Permissive Hypercapnea Absolute Contraindication – Intracranial lesions Considerations in Management – Creation of Intrinsic PEEP Intrinsic PEEP – Alveolar pressure above the applied PEEP at the end of exhalation Considerations in Management – Creation of Intrinsic PEEP Contributing factors • Pressure support ventilation • Airway obstruction • Rapid respiratory rate • Insufficient flow rate • Relatively equal I:E ratio • High minute volume • History of air trapping Considerations in Management – Creation of Intrinsic PEEP Problems associated with intrinsic PEEP – Increase in work of breathing – patient must overcome PEEP in order to trigger breaths – Underestimation of mean airway pressure – Increase in hemodynamic side effects – Increase in volutrauma Considerations in Management – Creation of Intrinsic PEEP Determination of Intrinsic PEEP – Esophageal balloon – End-expiratory hold by ventilator Considerations in Management – Creation of Intrinsic PEEP Correction or Reduction of Intrinsic PEEP – Improve ventilation and reduce air trapping by use of bronchodilators – Prolong expiratory time by increasing flow or reducing tidal volume or frequency Considerations in Management – Inverse Ratio Ventilation (IRV) IRV - Mode of ventilation in which the inspiratory time is longer than the expiratory time Purpose – Treatment of patients with refractory hypoxemia not responsive to conventional modes of mechanical ventilation Considerations in Management – Inverse Ratio Ventilation (IRV) Physiology – Overcome non-compliant lung tissue – Recruitment of collapsed alveoli – Increase in time for diffusion of oxygen across the alveolar-capillary membrane – Increase in mean airway pressure Considerations in Management – Inverse Ratio Ventilation (IRV) Method – Decrease inspiratory flow – Increase in inflation hold time – In APRV mode, can be created when pressure release rate is less than 20/minute Considerations in Management – Inverse Ratio Ventilation (IRV) Because of the increase in mean airway pressure, there is an increased potential for hemodynamic side effects; these are usually limited during acute administration because the pressure is not communicated to the cardiovascular system Considerations in Management – Extracorporeal Membrane Oxygenation (ECMO) Modified form of cardiopulmonary bypass used to provide relatively long-term support for the function of oxygenation of the tissue using an extracorporeal machine capable of gas exchange Considerations in Management – Extracorporeal Membrane Oxygenation (ECMO) Purpose – Intrinsic recovery of the lungs – Support gas exchange – Provide adequate tissue perfusion – Support cardiac function Considerations in Management – Extracorporeal Membrane Oxygenation (ECMO) Indications – Failure of advanced ventilator strategies – Oxygen Index (OI) greater than 40 – OI = (Mean Airway Pressure x FIO2 x100)/PaO2 – Acute deterioration Considerations in Management – Extracorporeal Membrane Oxygenation (ECMO) Technique – A cannula is inserted into the right atrium via the right jugular vein – Blood is withdrawn through the cannula – The blood passes through a membrane oxygenator where oxygen and carbon dioxide are exchanged – The blood is then warmed and reinfused into the right common carotid artery Considerations in Management – High Frequency Ventilation (HFV) High Frequency Positive Pressure Ventilation (HFPPV) – Mode of ventilation in which a conventional ventilator delivers a rapid rate at a low tidal volume Technique: • Respiratory rate is set at minimum of 60 breaths per minute • Tidal volume is set at less than 5 mL/kg IBW Considerations in Management – High Frequency Ventilation (HFV) High Frequency Jet Ventilation (HFJV) – Mode of ventilation in which a pulse of high velocity blended gas is introduced through a side port of the endotracheal tube – Conventional ventilator provides PEEP and intermittent breaths – Rate of jet pulses set between 60 and 600 breaths per minute – Inspiratory time of jet is 20 to 40 milliseconds Considerations in Management – High Frequency Ventilation (HFV) High Frequency Oscillatory Ventilation (HFOV) – Mode of ventilation in which 180 to 3000 pulses per minute are delivered to the airway Technique • Ventilator frequency is set usually between 5 and 6 Hz; the lower the hertz (Frequency), the higher the tidal volume • Flow is continuous at 15 to 20 Lpm • Inspiratory time is set at 33% Considerations in Management – High Frequency Ventilation (HFV) High Frequency Oscillatory Ventilation • Lung volume is determined by observing chest “wiggle” (visible vibration from shoulder to midthigh area) • Mean airway pressure should start at 5 cm H2O above the mean airway pressure observed during conventional ventilation • Chest X-ray should be done within four hours of initiation of HFOV to evaluate lung volume • No breaths are delivered at conventional volumes Considerations in Management – High Frequency Ventilation (HFV) Comparison of High Frequency Techniques HFPPV HFJV HFOV Expiration Passive Passive Active Pressure Waveform Variable Triangular Sine > Dead Space < Dead Space < Dead Space Ventilation Ventilation Ventilation 180 – Frequency 60 – 150/min 60 – 600/min 3000/min Tidal Volume Considerations in Management – High Frequency Ventilation (HFV) Advantages of HFV – Lung protection – limits overdistention of alveoli by means of smaller volumes and lower peak inspiratory pressures; decrease in barotrauma – Decrease in complications including compromised cardiac output and increased intracranial pressure – Increases mean airway pressure; improves alveolar recruitment with PEEP, both set and intrinsic – Improved gas exchange; improvement in ventilation/perfusion matching from rapid flow pattern Considerations in Management – High Frequency Ventilation (HFV) Contraindications and Hazards – No absolute contraindications – Relative contraindication or caution • Chronic obstructive lung disease • Non-homogenous Hazards • • • • • Air trapping Inadequate humidification Tracheal injury from high flow velocity Inadequate monitoring lung disease Hemodynamic Monitoring – Arterial Blood Pressure Monitoring Assessment of overall cardiovascular tone and dependability of oxygen delivery Normal Value – Systolic – 100 to 140 mmHg – Diastolic – 60 to 95 mmHg; many cardiologists are now stating that the diastolic should be maintained no higher than 80 mmHg Hemodynamic Monitoring – Catheterization Arterial Catheter – Site of Insertion • • • • Radial artery (preferred) Brachial Femoral Dorsalis pedis – Site of Placement • In systemic artery in proximity of insertion site – Purpose • Measurement of systemic arterial pressure • Source of sample for arterial blood gases Hemodynamic Monitoring – Catheterization Central Venous Catheter – Site of insertion • Subclavian • Internal jugular vein – Site of placement • Superior vena cava or in or near right atrium – Purpose • Measurement of central venous pressure • Administration of fluid and/or medication Hemodynamic Monitoring – Catheterization Pulmonary Artery Catheter (Swan-Ganz or FlowDirected Catheter) – Site of insertion • Subclavian • Internal jugular vein – Site of Placement • Branch of pulmonary artery – Purpose • Measurement of CVP, PAP, and PCWP • Collection of mixed venous blood gas samples • Monitoring of mixed venous oxygen saturation • Measurement of cardiac output • Provision of cardiac pacing Hemodynamic Monitoring – Values Monitored Value Arterial Blood Pressure MAP– Mean Arterial Blood Pressure ECG – Electrocardiogram Normal Range 90-140/60-90 mmHg 80 – 100 mmHg Normal Heart Rate and Rhythm Abnormal Value > 140/90 – Hypertension < 90/60 - Hypotension > 100 mmHg – Hypertension < 80 mmHg - Hypotension PR interval > 0.2 sec., Tachycardia, Bradycardia, First-, Second- , and Third-Degree Heart Block, Premature Ventricular Contractions, Atrial Fibrillation, Atrial Flutter, Elevated S-T Segment, Inverted T Wave, Ventricular Tachycardia, Ventricular Fibrillation, Asystole Hemodynamic Monitoring – Values Monitored Value CVP – Central Venous Pressure PAP – Pulmonary Artery Pressure Normal Range Abnormal Value 2 – 6 mmHg > 6 mmHg: Fluid Overload, Right Ventricular Failure, Pulmonary Hypertension, Valvular Stenosis, Pulmonary Embolism, Cardiac Tamponade, Pneumothorax, Positive Pressure Ventilation, PEEP, Left Ventricular Failure < 2 mmHg: Hypovolemia, Blood Loss, Shock, Peripheral Vasodilation, Cardiovascular Collapse 20-35/5-15 mmHg > 35/15 mmHg: Pulmonary Hypertension, Left Ventricular Failure, Fluid Overload < 20/5 mmHg: Pulmonary Hypotension, Hypovolemia, Cardiovascular Collapse Hemodynamic Monitoring – Values Monitored Value – Mean Arterial Pressure PCWP – Pulmonary Capillary Wedge Pressure Normal Range Abnormal Value 10 – 20 mmHg > 20 mmHg: Same as ↑ PAP < 10 mmHg: Same as ↓ PAP 5 – 10 mmHg (< 18 mmHg) > 18 mmHg: Overload > 20 mmHg: > 25 mmHg: > 30 mmHg: Left Ventricular Failure, Fluid Interstitial Edema Alveolar Filling Frank Pulmonary Edema Hemodynamic Monitoring – Values Monitored Value Normal Range CO – Cardiac Output 4 – 8 L/min CI – Cardiac Index 2.5 – 4 L/min/m2 Abnormal Value > 8 L/min: Elevated < 4 L/min: Decreased > 4 L/min/m2: Elevated due to Stress, Sepsis, Shock, Fever, Hypervolemia, or Medications < 2.5 L/min/m2: Decreased due to Left Ventricular Failure, Myocardial Infarction, Pulmonary Embolus, High Levels of PPV, PEEP, Blood Loss, Pneumothorax, Hypovolemia Hemodynamic Monitoring – Values Monitored Value SVR – Systemic Vascular Resistance PVR – Pulmonary Vascular Resistance Normal Range 900 – 1400 Dynes-Sec/cm5 (11.25 – 17.5 mmHg/L/min Abnormal Value > 1400 Dynes-sec/cm5: Increased due to Vasoconstrictors, Late Septic Shock, Hypovolemia < 900 Dynes-sec/cm5: Decreased due to Vasodilators, Early Septic Shock > 250 Dynes-sec/cm5: ↓pH, ↑PCO2, 110 – 250 DynesVasopressors, Emboli, Hypoxemia, sec/cm5 Emphysema, Interstitial Fibrosis, Pneumo1.38 – 3.13 thorax mmHg/L/min < 110 Dynes-sec/cm5: Pulmonary Vasodilators, Nitric Oxide, Oxygen, Calcium Blockers The End Considerations in Management – Open Lung Ventilation • Purpose - optimize lung mechanics and minimize phasic damage by placing PEEP above Pflex • Pflex is the point on the pressure-volume curve below which the alveoli begin to collapse during exhalation Considerations in Management – Open Lung Ventilation • Rationale – Reinflation of atelectatic alveoli on a breath-bybreath basis increases lung injury – Determination of the Pflex on the pressure-volume curve signifies the pressure at which alveolar collapse occurs – PEEP is applied just above the Pflex level Considerations in Management – Open Lung Ventilation • Rationale – This is a higher than conventional level of PEEP allowing use of a lower tidal volume – Respiratory rate is increased incrementally to maintain an acceptable PaCO2, at times as high as 35 breaths per minute