CAPNOGRAPHY DR JOHN ROOS
Abraham Lincoln If you want me to speak for an hour give me a moment s notice if you want me to speak for five minutes give me a week.
Missed oesophageal intubation Many studies report missed oesophageal intubation rates of 1 to 2 percent Three studies reported rates at: 5.8% 9% 25% (Katz & Falk)
The three studies Silvestri S, Ralls G, et al. The effectiveness of out-ofhospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognised misplaced intubation within a regional emergency medical services system. Annals Emerg Med 2005; 45 (5): 497-503. Vilke G, Steen P, et al. Out-of-hospital paediatric intubation by paramedics: the San Diego experience. J Emerg Med 2002; 22 (1): 71-74. Katz S, Falk J. Misplaced endotracheal tubes by paramedics in an urban EMS system. Ann Emerg Med 2001; 37: 32-37
Only Of the studies reporting missed oesophageal intubation rates of 1 to 2 percent Many prefix their percentage-proclamation with the disarming adverb only
The question What s an acceptable missed oesophageal intubation rate?? Before we answer that, let s consider
How BIG is only one percent???
Anaesthetist vs Paramedic USA anaesthetic mortality rate estimated at a maximum 5 deaths per million anaesthetics Or at worst 1 death per 200 000 anaesthetics Lema M, American Society of Anaesthesiologists Newsletter, March 2004, Vol 64.
Anaesthetists vs Paramedics Unrecognized oesophageal intubation rate of only one percent Equals 2000 deaths per 200 000 prehospital intubations Presuming that the patient died from this oversight (which would be the case if neuromuscular blockade was used universally).
Prehospital vs In-hospital 2000 times greater chance of dying due to a misplaced tracheal tube out of hospital
Failure rate of only 1% in the airline industry 30 airline crashes at Heathrow Airport every single day!
To further illustrate 20 000 ALS paramedics in USA If each paramedic intubates one person/week And each has a missed oesophageal intubation rate of only one percent 10 400 missed oesophageal intubations per annum
Three 9/11 catastrophes every year!
Salt into the wounds Recent studies show misplaced ETTs amongst American paramedics to be 5% Bledsoe BE. The disappearing ET tube. JEMS March 2009. Vol 34. No. 3.
Who kills more Americans on home ground?
The ONLY modality proven to prevent missed oesophageal intubation is continuous end-tidal capnography
Inspiration/expiration?
What s this? Prolonged expiration Respiratory outflow obstruction Bronchospasm!
Continuous waveform capnography: Circuit disconnect Extubation Total airway obstruction Ventilator failure Gas supply failure
Continuous waveform capnography provides continuous monitoring of ET tube placement Cf: Snapshot techniques: Visualisation Auscultation Oesophageal detector devices
Early or late warning device? Breath by breath monitor Alarms after a single breath Very definitely an EARLY WARNING device!!
What s happening here? Ventilation rate monitor
And here? Tidal volume has changed Indirect monitor of tidal volume
What s happening here? Progressive hypoventilation Circuit leak ET tube cuff deflated Ventilation failure
And here? Curare dips Patient fighting ventilator inspiration during expiratory phase Direct monitor of neuromuscular blockade Indirect monitor of sedation
Minute vent. may be changing? Progressive hyperventilation Could be any cause In pressure control ventilation: two things Resolving bronchospasm Ascending altitude
No change in minute ventilation Spirometer says MV/TV unchanged!
No change in minute ventilation Spirometer says MV/TV unchanged Decreased cardiac output! PERI-ARREST Decreased venous return to RV, means decreased CO 2 returned to lungs STATE!!! Means decreased CO 2 exhaled!
What s this? Inspired CO 2! CO 2 not returning to baseline Rebreathing expired gases Fresh gas flows too low Malfunctioning inspiratory/expiratory valve CO 2 absorber (soda lime) exhausted
And here? Both plateau and baseline increasing! Increased CO 2 production (failure to eliminate) Therefore a hypermetabolic state Malignant hyperthermia Thyroid storm Phaeochromocytoma Sepsis
Summary Continuous, early warning monitor ET tube placement Circuit disconnect Circuit integrity (leak) Ventilator malfunction Inspiratory/expiratory valve malfunction
Summary Gas supply Gas flow Quality of inspired gas (FiCO 2 - absorber malfunction, soda lime)
Summary Respiratory rate monitor Tidal or minute volume monitor (indirect) Airway obstruction and bronchospasm Neuromuscular blockade Sedation (indirect) Cardiac output (indirect) Metabolic rate monitor (blunt instrument)
Have you totalled that up? Independently monitors 15 different parameters Either directly or indirectly What does a pulse oximeter monitor? 1. Oxygen saturation 2. Heart rate
Pulse Oximetry What does a pulse oximeter tell you in: Peripherally shut down Vasoconstricted Hypothermic Hypovolemic patient? NOTHING!!
johnroos@iafrica.com Senior Specialist and Head Dept. of Anaesthesia GF Jooste Hospital Hon. Chief Medical Officer SA Red Cross Air Mercy Service Hon. Senior Lecturer Dept. of Anaesthesia and Div. Of Emergency Medicine University of Cape Town