Respiratory Monitoring 2024 PDF

Respiratory Monitoring Foundations of Critical Care 2024 D.Freer Learning objectives Review essentials of respiratory monitoring Answer the questions What is respiratory monitoring? Different forms of monitoring available Who do we monitor? W...

Respiratory Monitoring Foundations of Critical Care 2024 D.Freer Learning objectives Review essentials of respiratory monitoring Answer the questions What is respiratory monitoring? Different forms of monitoring available Who do we monitor? Why do we monitor? Monitoring Monitor – Verb “to watch and check a situation carefully for a period of time in order to discover something about it” “to watch closely for purposes of control, surveillance, etc.; keep track of; check continually” Latin: Monit - warned Case Study Mr Peter Rabbit Age: 35 Presentation: Elective laparoscopic bariatric surgery PMHx: ▪ Obstructive Sleep Apnoea – home CPAP ▪ Previous Respiratory arrest following sedation for endoscopy ▪ BMI 40 ▪ Ischemic Heart Disease Progress In OT: ▪Bleeding from liver Laceration and splenic hilum; ▪No record of respiratory monitoring for last 1h 30 min prior to discharge to Recovery?? In Recovery: ▪SpO2 drop 2x below 90%; ▪Decision for pt’s own CPAP; ▪Pt’s own CPAP does not fit supplemental O2; ▪CPAP idea abandoned, continues with a CIG/Hudson mask; ▪Mr Rabbit is in severe pain; ▪Morphine pain protocol; ▪Over recovery stay SpO2 80-95%. In HDU ▪Mr Rabbit is admitted to HDU at 19:40h; ▪No Cardiac monitoring is connected as it is only used for cardiac patients (there was equipment available); ▪From 19:40 – 20:20 Mr Rabbit’s monitor alarmed 33 times for low SpO2. ▪Mrs Rabbit, while visiting her husband says that he sounds like he is sleeping without his CPAP machine but much worse. She goes home at 19:55; ▪2 x the RNs in HDU reposition the SpO2 finger probe, attempt to rouse the patient and observe his SpO2 climb slowly to 90% Conclusion ▪At 20:22 Mr Rabbit’s monitor beeps inoperative and there is a question mark after a flat plethysmographic waveform. ▪At 20:38 the RN comes to review him; ▪A Code Blue is called… Unfortunately, Mr. Rabbit died in 2013 as a result of ischemic encephalopathy following laparoscopic bariatric surgery with iatrogenic spleen and liver damage (? Artery lacerated?) (Coroner’s report) Are we satisfied with the respiratory monitoring that Mr. Rabbit received? What would you have done differently? What respiratory monitoring is available? Nurse initiated Other Inspection Imaging WOB X-ray RR CT Palpation VQ Auscultation Ultrasound Pulse Oximetry MRI Capnography Bronchoscopy VBG Vent feedback Peak Flow ABG Spirometry Let’s review Why do we breathe? Oxygen in – oxygenation CO2 out – ventilation We use various forms of monitoring to assess both oxygenation and ventilation How do we breathe normally ? Voluntary OR Cellular metabolism generates CO2 High levels of CO2 detected centrally Phrenic nerve innervated Diaphragm moves down Intercostals move out Mixed gases come in 21% Oxygen 1% CO2, Argon, water vapour, and other gases 78% Nitrogen Gas exchange occurs Then everything relaxes and CO2 is exhaled Inspection Look at your patient – make sure you undress them in the ED!! - Equal expansion - Signs of trauma Work of breathing – assessing oxygenation or ventilation? - Ventilation - Combination of RR and TV – think minute ventilation Respiratory Rate – Count it! Why is it the first vital sign to go off? Palpation Palpate equal expansion Tenderness Subcutaneous emphysema Auscultation How many of you own a stethoscope? How many of you use it? What can you tell with a stethoscope? Pulse Oximetry How many Red cells in the body? How many Hb in one red cell? Pulse Oximetry is a non-invasive method of measuring the percentage of Haemoglobin (Hb) saturated with Oxygen (O2) in arterial blood PaO2 vs Hb carrying capacity SpO2 SaO2 Can also measure pulse amplitude and pulse rate Continuous or intermittent Pulse Oximetry Limitations Only as good as the operator Positioning of the probe Intravascular dyes – methylene blue Nail varnish will give falsely low readings Anaemia Vasoconstriction / decreased perfusion (low flow states) Cannot distinguish between different forms of Hb Carboxyharmoglobinaemia Methheamoglobinaemia Accurate in general above 80%, below CHECK with ABG Oxygen-Haemoglobin Dissociation Curve Describes the sigmoidal relationship between the partial pressure of oxygen (PaO2) and the oxygen saturation of haemoglobin Describes the changing affinity of haemoglobin for oxygen which occurs with increasing PaO2 It can shift - Physiologically - Pathologically Effect of the shift on SpO2 The same SpO2 can have different relationships to PaO2: - With a right shift have higher PaO2 (acidosis, high CO2, high temp, more 2- 3DPG) Oxygen has a greater affinity to offload from the Hb - With a left shift have lower PaO2 (alkalosis, low CO2, hypothermia, less 2- 3DPG) Oxygen doesn’t want to leave the Hb Always interpret SpO2 in light of underlying pathology that could affect the oxygen- haemoglobin dissociation curve Capnography The measurement of carbon dioxide (CO2) in expired air Continuous, non-invasive Capnometer - device that measures and displays a numerical value of carbon dioxide Capnograph - also displays the carbon dioxide waveform Infrared spectroscopy (absorption) ▪A beam of infrared light is passed through a gas sample containing CO2 ▪CO2 molecules absorb specific wavelengths of infrared light energy ▪Light emerging from the sample is analysed ▪A ratio of the CO2 affected wavelengths to the non-affected wavelengths is reported as ETCO2 Indications Confirmation of tracheal intubation Real-time surrogate CO2 monitoring: Patients with CO2 retention Head injured patients Ongoing intubation and ventilation Ventilator weaning Assessment of ROSC Limitations Nasal probe placement – normally not enough gas flow Sensor is susceptible to blockage by secretions or condensation May erroneously read Nitrous Oxide or helium as CO2 Who do we monitor? So, we have discussed what respiratory monitoring is. Who do we monitor? What do we base our monitoring on? Why do we monitor? Looking for those warning signs If you see a warning sign, do something about it. Better to not monitor than to monitor without action. Case Study 1 Identity: Jack Black, 24 Y.O M Situation: Brought into ED on a Friday night by friends. Was out on the town with friends and “took some odd pills” before becoming unrousable. Nil evidence of trauma Background: Nil PmHx, no regular medications Case Study 1 A: What monitoring do you want to inform your Assessment? Airway Inspection – look, listen, feel. Maintaining own. Sonorous respirations. Dried vomit around mouth. C-spine – immobilise or not? Breathing What monitoring? Breathing spontaneously, RR – 8bpm. SpO2 92% RA. Nasal ETCO2 50mmHg, equal chest wall expansion, nil trauma Circulation Warm, well perfused peripheries. HR 130 sinus, BP 100/50 Disability: What assessment / monitoring? Rousable to pain, GCS 11 (E2, V4, M5). BSL 5.4 Exposure Nil external evidence of trauma, t- 35.0 Case Study 1 Still on Assessment What ongoing respiratory monitoring is essential for Jack? Why? What shift will his SpO2 curve have? Why? What does this shift mean for his PaO2 and oxygen reserve? What are your recommendations for Jack’s care? Case study 2 Identity Thelma, 60 YO Female Situation: Presented to ED with acute SOB. Commenced on CPAP & GTN infusion for APO. Unable to wean off CPAP – just transferred to CCU. Background IHD, HTN, heart failure (1 litre fluid restriction), recurrent UTIs Case study 2 Assessment: What monitoring do you want to inform your Assessment? Airway Inspection – look, listen, feel. Maintaining own. Risk of NIV? Staffing ratio? Breathing What monitoring? Breathing spontaneously, RR – 28bpm SpO2 95% FiO2 0.4. Circulation Warm, well perfused peripheries. HR 130 sinus, BP 100/50