Jsrcc airflow and cpap

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  • 1. Requirement for this lecture:one balloon that is easy to inflate andone that is difficult to inflate

2. Respiratory Waveforms Nasal Flow via nasal cannula Oral/nasal flow via thermistor Effort via esophageal pressure (not often used) Rib cage and abdominal movement via RIP (respiratory inductive plethysmograph) 3. Rib cage and abdominal belts (RIP) During quiet, unobstructed breathing the belts move in and out together. This reflects the RC(rib cage) and Ab(abdomen) expanding and relaxing together. With partial obstruction the belts can begin to move out of phase with each other. 4. Rib cage and abdominal belts (RIP) With significant or full obstruction the belts will movein paradox; that is one moves out when the othermoves in. This is because the airway is now a closedsystem-the volume doesnt change. So, if you expandyour chest (increasing chest volume) you have todecrease your abdominal volume and vice versa. Now fill your balloon with air (or water if you like) andtie it off. What happens to the top of the balloon if yousqueeze the bottom? What happens to the bottom ifyou squeeze the top? That is PARADOX! 5. Thermistor This measures temperature change as air moves in anout. It can tell you the presence of air flow but cannot giveyou information about the quality of that flow such asflow limitation. 6. Nasal cannula Actually measures the pressure changes as air movespast the cannula. In a closed system like a nasal mask (with no leak)pressure equals flow. In a small area (like the inside of the nose) pressure isvery similar to flow. This would not work for oral flow because it is not aclosed area. The signal you see is showing the rate of change of theinspiratory and expiratory pressure 7. Unobstructed Airflow measured bymask or nasal canula Inspiratory flowExpiratory flow Zero flow Notice that the unobstructed inspiratory flow (pressure) signal is rounded. As the signal moves up it is showing the flow rate increasing and as the signal moves back to zero the rate of flow is decreasing. The expiratory signal is pointed and gradually returns to zero. Inspiratory flow should always be up. 8. Partially obstructed inspiratory flow (UAR)Notice the concave shape of the inspiratoryflow signalThis occurs because during inspiration theairway narrows and the rate of inspiratoryflow decreases despite increasing effort. 9. Compare the obstructed andunobstructed breaths 10. Esophageal Pressure (Pes) A balloon on a catheter is placed through the nose intothe esophagus. This pressure reflects the pressure being generated inthe larynx. When you breathe in the negative pressure changesthe pressure in the balloon and it returns to normalduring relaxed exhalation. The harder it is to breathe (increased resistance,snoring, upper airway obstruction) the more negativepressure you have to develop to draw in air. 11. Esophageal pressure (Pes)Notice that Pes is negative during inspiratory flow. This indicates the negative(suction) pressure generated by the expansion of the lungs that causes inspiratoryflow. Pressure returns to zero during relaxed expiration.The next slide shows you how pressure and flow change from wake to sleep toincreased resistance/snoring. 12. RoundedNotice the rounded inspiratoryWakeinspiratoryflowflow, little effort (Pes-esophageal Little pressure indicates how hard you effort work to pull in air), and RC and ABare in phase RC and AB in phaseSleep- The airway is still open althoughopenbreathing frequency is higherthan awake rounded flow, littleairwayeffort, and RC and AB are still inphase Notice now the inspiratory flow Insp. Flow is collapsedSleep- Indicating flow limitationsignal is not rounded but isFlow collapsed a little, Pes is biggerGreater pressure indicating much more pressurelimitationDevelopment means morework has to be developed to breath andRC and AB out of RC and AB are paradoxingphase 13. Respiratory belts, airflow and respiratory effort (Pes) when partial obstruction resolvesThis picture shows anindividual moving frompartial obstruction to afully open airway.Notice that when airflow(measured by nasal pressure in thefirst few breaths of channel e)shows flow limitation the RC (a) and AB (b) arein paradox. The pressuredeveloped (f) is large.In the last breath, with noflow limitation, the beltsare in phase and littlepressure is developed 14. Why does this happen?Remember: The upper airway is composed partially of muscle. Upper airway muscles relax in sleep This allows the airway to narrow in everyone and insome to partially or fully collapse. The next slide shows the airway changing from wake to sleep to snoring to hypopnea to apnea. Below that are the effects on flow and pressure. 15. Sleep on the upper airway and its consequences 16. CPAP on the Upper airway CPAPs positive airway pressure essentially takes theplace of the relaxed muscles to hold open the airway.Get your easy to inflate balloon and blow just enoughair in to stretch it a little. Now try it again with thestiffer balloon. Can you tell that it takes more pressurefor you to inflate the second balloon? Peoples airways are like balloons with different degreesof stiffness. This is why they need different levels ofPAP. 17. Bilevel Pressure on the Upper Airway Bilevel pressure is a combination of CPAP (which isthe expiratory pressure) and mechanical ventilationwhich helps to inflate the lungs. Now blow enough air in one balloon just to hold itopen (point A.) That is the CPAP. Now, holding that pressure inflate your balloon a little(point B) then let the pressure back to point A. This simulates what bilevel pressure does. It hold theairway pressure at a certain level to keep it open thenadds more air pressure during inspiration to increasethe size of the breath.