Monitoring Ventilated Patients Dr.T.Sureshkumar MD, IDCCM, EDIC Consultant Intensivist Kovai Medical Center and Hospitals SCOPE OF THIS TALK • The aim is not to make anybody expert but to guide safe and efficient practice. • Narrowed down to avoid major catastrophe • Focused on graphics and hemodynamics as time limits • Language is not a barrier here & I am not the best in English. • My intention is not delivery but reach, so please come close to me. • Three Phases 1. Induction 2. Maintenance 3. Weaning • Five Monitors 1. Patient 2. Ventilator 3. Vitals 4. Images 5. Labs Why Ventilation ?? Need for Ventilation Pulmonary Extra Pulmonary Abnormal lung Normal lung Air way issues High resistance Parenchymal issues Poor Compliance Start with…Intubation 1st - Look your Patient Look & check air entry 1. Abnormal breathing Abdomen distending Irregular chest rise Hear 1. Five point auscultation 2. Abnormal sounds –wheeze, crepts And Yes your tube in right place… Patient • At induction phase Pt will be in control ventilation • During maintenance Pt will trigger and may attempt his own breath • Care should be taken whether he tolerates ventilator • Our settings adequate for him • Asynchrony • Disease worsening • During Weaning : • Important to communicate with Patient • Don’t ignore his needs nd 2 – Check Ventilator • Two important things 1. What the ventilator gives to the patient 2. How the lung accepts it. 1.Basic setup a) Oxygenation ( FiO₂) b) Ventilation (RR, Vt) c) Desired mode d) Recruitment (PEEP) if needed. 2.Scalars and loops 3.Parameters 4.Alarm settings Ventilator Graphics • Scalar and Loops are windows to Lung-Ventilation Mechanics • So all modern ventilators equipped with Graphical representations. • Gives a quick clue for problem even from a distance. • On evaluation can diagnose specific disorder and helps in preventive measures. • Scalars and Loops: • Scalars: Plot pressure, volume, or flow against time. Time is the x-axis. • Loops: Plot pressure or flow against volume. (P/V or F/V). There is no time component. Volume Modes Volume Control SIMV (Vol. Control) Pressure Modes Pressure Control PRVC SIMV (PRVC) SIMV (Press. Control) Pressure Support Volume Support Pressure Time Plateau Pressure Airway Pressure Mean airway Pressure Increased Airway Resistance PIP Decreased Compliance PIP Raw Pplat Pplat •A -Increase in airway resistance (Raw) causes the PIP to increase, but Pplat pressure remains normal. •B-A decrease in lung compliance causes the entire waveform to increase in size. (More pressure is needed to achieve the same tidal volume). The difference between PIP and Pplat remains normal. Air-Trapping (Auto-PEEP) •An acceptable amount of auto-PEEP should be < 5cm H2O Flow Time Volume Pressure Wheeze & Bronchodilator Response Improved Peak Flow • The area of no flow indicated by the red line is known as a “zero-flow state”. • This indicates that inspiratory time is too long for this patient. Is it Inadequate insp. Time?? No . In spontaneous mode it is decided by the patient Volume Time Air-Trapping or Leak Pressure / Volume loops Dynamic Compliance Over distention/DHI •As airway resistance increases, the loop will become wider. •An increase in expiratory resistance is more commonly seen. Increased Compliance Example: Emphysema Decreased Compliance Example: ARDS, CHF, Atelectasis Lung Compliance Changes and the PV Loop Preset VT Volume Targeted Ventilation COMPLIANCE Increased Normal Decreased Volume (mL) Paw (cm H2O) PIP levels Increased Normal Decreased Pressure Targeted Ventilation COMPLIANCE VT levels Lung Compliance Changes and the PV Loop Volume (mL) Paw (cm H2O) Preset PIP A Leak The expiratory portion of the doesn’t return to baseline. This indicates a leak. loop Pressure / Volume Loop The shape of the inspiratory portion of the curve will match the flow waveform. A Leak Normal If there is a leak, the loop will not meet at the starting point where inhalation starts and exhalation ends. It can also occur with air-trapping. Airway Obstruction Flow Starvation The inspiratory portion of the pressure wave shows a “dip”, due to inadequate flow. Hemodynamics • Important to understand Thoracic physiology – Heart & Lung. • Normally the Negative Plural Pressure augments the venous return to RA and thus increases CO • So Output increases during Inspiration than Expiration. • But in case of Positive Pressure it differs The systolic pressure and the pulse pressure are maximum (SPmax and PPmax) during inspiration and minimum (SPmin and PPmin) during the expiratory period. In hypovolemic conditions (1) RV preload decreases because the increase in pleural pressure induces a compression of the superior vena cava (2) an increase in intramural right atrial pressure (3) RV afterload increases because pulmonary capillaries are compressed. (4) The increase in alveolar pressure squeezes out the blood contained in the capillaries toward the left side of the heart. (5) The increase in pleural pressure induces a decrease in left ventricular afterload In hypervolemic conditions The vena cava and right atrium are poorly compliant and compressible and hence relatively insensitive to changes in pleural pressure (4) Each mechanical breath increases pulmonary venous flow and left ventricular preload (5) The increase in pleural pressure induces a decrease in left ventricular afterload . Capnography • Measures End-tidal CO2 (EtCO2) • Monitors changes in • Ventilation - asthma, COPD, airway edema, foreign body, stroke • Diffusion - pulmonary edema, alveolar damage, CO poisoning, smoke inhalation • Perfusion - shock, pulmonary embolus, cardiac arrest, severe dysrhythmias • Gold Standard for confirming Intubation • Reports quality of CPR Normal 45 0 Normal range is 35-45mm Hg (5% vol) Waveform End-tidal Ascending Phase of Exhalation A Baseline B C Alveolar Plateau D Descending phase of Inhalation E Normal 45 0 Hyperventilation 45 0 Hypoventilation 45 0 45 Normal 0 Bronchospasm 45 0 SPO₂ • Works at two different wavelengths absorbed by oxy and deoxy Hb and the gradient is used to calculate Hb saturation. • Different models of probes available. • Very useful to pick Pt deterioration. • Pros : Cons : • • • • Mobile All time wearable Real time monitor Cheap • • • • • Sats < 85 % are unreliable Impedance disturbances Picks little late Cannot measure MetHb, SulHb Altered with shock state, nail polish, dyes etc CXR • Useful for properly locating the ET • Diagnosing issues. • Follow Up of Disease. ABG • Its out of scope for this Session. • Check Ph • Metabolic side(HCO3) / Respiratory Side(PCO2) • Compensated/ Uncompensated • Any ventilator change can alter it. Charting • Even the best handing over cannot replace charting • Reviewing trends helps in Pt Dx & Mx. Language is not a barrier here & I am not the best in English.