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DrReedChp1
Mech Vent chp 1 test 2/6/18
| Question | Answer |
|---|---|
| RAW Formula | RAW = Change in pressure (Peak - Plat) / Flow |
| Static Compliance Formula | Cst = Corrected Vt / (Plat - Peep) Normal is 40-60 |
| Dynamic Compliance Formula | Cdyn = Corrected Vt / (Peak - Peep) Normal is 30-40 |
| What is ATC? | Automatic Tube Compensation = Vent compensates for size of ET tube |
| What is PRVC? | Pressure Regulated Volume Control = Vent automatically regulates pressure. No flow; only i-time. Regulates the flow to use lowest pressure possible |
| What is normal RAW? | 0.5 - 2.5 cmH20 /L / sec |
| What type of patient needs mechanical ventilation? | Pts who are unable to sustain the level of ventilation necessary to maintain the gas exchange functions. |
| If you decrease the ET tube radius by 1/2. what is the outcome? | The flow (WOB) through the tube increases sixteen-fold |
| What is ventilation? | Movement of air in and out of the lungs. |
| A patient on a vent changes according to what? | RAW and Compliance |
| How many valves on a volume control vent? | Two = 1 for inhalation and 1 for exhalation; YOU tell the vent when to switch them on and off based on the settings you use. |
| Flow determines what? | The I/E Ratio ; Normal is 1:2 |
| RAW affects what? | Flow = volume / time because flow is basically volume |
| Airways = | Flow / volume |
| Lungs = | Compliance |
| Set Vt and RR determines ??? | Ve (minute ventilation) |
| Formula for Minute ventilation | Vt (x) RR = Ve This determines PaCO2 |
| When we ventilate, we should worry about ???? | CO2 |
| Minute Ventilation (Ve) is always in | Liters |
| Tidal Volume (Vt) is always in | mL |
| How does flow affect time? | Increase flow = decrease time Decrease flow = increase time |
| What is SIMV? | A mode to set on the ventilator; stands for "synchronized intermittent mechanical vent" |
| What is AC? | A mode to set on the ventilator; stands for "assist control" NO PS on AC |
| What does SIMV mode mean? | Pt can take their own breath, but vent won't sent in set Vt. Will let pt breath and make his/her own Vt. We can see what pt is doing - spontaneous Vt - If the pt can do Vt you set, they can get off the vent. |
| What does AC mode mean? | If pt wakes up, he/she can take their own breath, but still get tidal volume you set. However, you can't wean on assist control, because you can't see what pt is doing. |
| SIMV is what type of mode? | A weaning mode; You add Vt you set plus Vt pt is doing |
| Pressure support is only available on what modes and what is normal setting? | Only on SIMV and CPAP; PS always starts at 10. |
| Pt can be on __________ and not take any breaths on his/her own. | AC = Assist Control |
| Who adds PS? (pressure support) | We add PS because vent doesn't automatically help when on SIMV |
| Why is SIMV called what it is? | SIMV = synchronized for a reason; if pt takes breath within 1/2 second on either side of the vent breath, the vent takes over and sends in Vt you set. Basically turns into AC so vent can't do "breath stacking" (pt can't breathe on top of a breath) |
| What is TC? | "True Control" Pt can't trigger a breath at all. It is generally not used anymore. Also same as CMV. |
| Pressure Versus Volume | Whichever you set, the other is variable, meaning it's the pt changing the one that isn't set. This lets you see compliance and resistance of the pt |
| If you set the Pressure.......... | RAW & Compliance will change volume |
| Parameters | What we set on vents |
| Monitor | What pt is doing -- we should be looking at this! |
| Peak Pressure | Total pressure in airways AND lungs (RAW & C) |
| Plateau Pressure | Total pressure in Lungs only |
| RAW is equal to | Peak - plateau; have to do inspiratory hold to get plateau pressure |
| PEEP | After pt exhales, what stays in lungs. It's oxygenation, not ventilation. |
| Getting rid of CO2 is | Ventilation; more PEEP the less you ventilate. |
| What is MAP? | Mean airway pressure; average pressure in the airways needed to get set Vt during one cycle. |
| Total parts x Ve = | Flow |
| What's the first thing you do when doing a vent check? | Check your alarms!! |
| All lower alarms mean | LEAKS |
| All higher alarms mean | OBSTRUCTION |
| Lower alarm is more _____________ than higher alarm | DANGEROUS!! |
| Inspiratory level above PEEP is | Pressure support |
| Pressure Control | increase pressure to set Vt |
| When you set pressure and PEEP..................... | you look at volume |
| Mean and _________ go together | PEEP; if you increase PEEP, you increase MAP |
| What does Peak mean? | Total amount of pressure to deliver Vt. (means Total pressure, RAW and C) |
| RAW is ____________ diseases | Obstructive; ie: Asthma / obstructive to flow / have to have volume ventilation |
| Compliance is ___________________ diseases | Restrictive; ie: Pneumonia / volume / restrictive / stiff |
| COPD is ....... (how it affects pt on vent) | Obstructive disease because of secretions; need longer to exhale, compliance too high, flow must be faster, i-time% turn down |
| Ideal flow for Mech Vent? | 40 - 60 L/min; flow determines I:E Ratio and TCT |
| How do you know if flow is enough? | Look at the I:E Ratio Also, know it's enough by checking pts WOB |
| Direct Relationships | RAW and change in pressure; ie: increase RAW and you increase WOB; decrease RAW and you decrease WOB |
| Inverse Relationships | RAW and Flow; ie: increase RAW and you decrease flow; decrease RAW and you increase flow |
| What is inspiratory hold? | hold button on vent used to get plateau pressure |
| What is ambient air? | Room air |
| When a pt is in ventilatory failure....... | He/she is acidotic, and can't oxygenate. |
| Increased C and Increased V mean | Easier to inflate; less pressure |
| Decreased Plateau means | Good compliance (increased) |
| Increased Plateau means | Low compliance (decreased) or stiff lungs |
| If you set Volume........ | No matter how much Pressure it takes, will go until reaches set Vt |
| If you set Pressure................ | Will go to what you set and hold until reaches Vt |
| If you set Vt............ | you set flow, they go together |
| If using PC | you set itime ; pressure and itime go together |
| Decreased Compliance means | Increased Pressure and WOB, vent failure, and oxygen failure |
| Increased Compliance means | Decreased Pressure and WOB |
| Retained secretions............. | in lungs, not airway; keeps alveoli from expanding |
| Static compliance means | No movement, no flow, so measures lungs; reflects the elastic properties of lung and chest wall. |
| Dynamic Compliance means | Movement and flow, measures RAW; reflects the airway resistance and elastic properties of lung and chest wall. |
| PIP - Plateau = | PIP (peak) - Plateau = RAW (Vent will show you PIP & Plateau) |
| When you have RAW....... | Go to pt and start there, and work your way back to machine to check for issues when you have RAW |
| Shift to pressure axis means | decreased compliance |
| Shift to volume axis means | increased compliance |
| Anatomic deadspace | Ventilation / no perfusion; The volume in the conducting airways |
| Wasted ventilation | Same as dead space ventilation; Anatomic, alveolar, and physiologic deadspace |
| When you have increased Dead Space ventilation | you decrease your tidal volume |
| Alveolar dead space ventilation | The normal lung volume that can't take part in gas exchange because of lack of perfusion ie: PE (blood clot) ; ventilated alveoli / not perfused |
| Physiological deadspace | Anatomic plus alveolar dead space; it is usually the same as anatomic dead space. |
| Increased physiological deadspace | Vd/Vt ratio; lead to increased WOB, pt unable to maintain, causes vent failure and oxygenation failure |
| Intrapulmonary Shunting | (in the lungs) increases pressure and decreases volume; causes wasted perfusion; have more blood than ventilation; perfusion in excess of ventilation. "wasted perfusion" |
| Hypoventilation causes | CNS depression, neuromuscular disorders, airway obstruction, increased PaCO2, Increased Vt and RR, leads to acute ventilatory failure, or chronic vent failure, and you are acidotic |
| V/Q Mismatch -- Increased | means decreased pulmonary perfusion ie: PE - most important - blood thinner because it decreases perfusion, if goes back to lungs, we have to ventilate pt |
| V/Q Mismatch -- Decreased | Due to decrease in ventilation (airflow obstruction), mild or uncompleted V/Q mismatch responds well to O2 Therapy |
| Refractory hypoxemia | doesn't respond to O2 therapy |
| What is shunt equation used for? | To see if we need to increase the PEEP; to see if there is shunting |
| What happens during diffusion defect? | (Stiff lungs) decrease A-a gradient (ie: high altitude), thickening of A/C membrane (edema), decreased surface A/C membrane (emphysema) Must do A-a gradient equation to see where it's at |
| What happens if PAO2 is insufficient? | O2 failure, hypoxemia, PaO2 < 40mm in spite of FiO2 50 to 100% |
| How to calculate minute alveolar ventilation(dead space)? | Va = (Vt - Vd) x RR (Tidal volume - Dead Space volume) |
| Increase in bowing of PV Loop equals | Overall increase in air flow resistance |
| In low compliance, what pressures change? | Plateau and peak pressures go up (stiff lungs) |
| In high compliance, what pressures change? | Plateau and peak pressures go down (flabby lungs) must send in flow faster and give longer to exhale |
| Normal Range of Dynamic Compliance | 30-40 mL/cmH2O |
| Normal Range of Static Compliance | 40-60 mL/cmH2O |
| Normal Total Compliance | 100 mL/cmH2O |
| What does smaller ET tube affect? | dynamic compliance |
| If you switch to PC...... | use less pressure to get same Vt, can give longer time with ARDS like an inverse ratio (2:1) |
| What is mechanical Dead space? | all your tubing and circuits, etc that affects total volume. You have to allow for it because exhaled Vt will be different. |
| Too much dead space will | decrease Vt and affect itime and etime |
| What mode for stiff lungs? | PC |
| What mode for all the other lung conditions? | AC |
| If we increase the PEEP, what is our guide to know when it's enough? | We must depend on the BP to let us know. |
| What is one of the most frequent uses of mechanical vents? | Mgmt of post-op pts recovering from anesthesia and medications |
| Other indications for mechanical vents? | Apnea, respiratory arrest, acute COPD exacerbation, acute severe asthma, neuromuscular disease, acute hypoxemic resp failure, heart failure, cardiogenic shock, acute brain injury, & flail chest. |
| Define Airway Resistance (in mech vents) | Airflow obstruction in the airways; in vents, it is affected by length, size, and patency of airway, ET tube, & circuits. |
| Name the six major pathophysiological factors for ventilatory/oxygenation failure. | 1)Increased RAW, 2)Changes in lung compliance, 3)Hypoventilation, 4)V/Q mismatch, 5)Intrapulmonary shunting, & 6)Diffusion defect |
| Increased RAW is usually caused by | 1)Changes in airway ie: secretions, 2)Changes in wall of airway, or 3)Changes outside the airway ie: compression of airway |
| Airway resistance varies DIRECTLY with ______________ and INVERSELY with ________________ of the airway or ET tube. | The length (directly); The diameter (inversely) |
| What is the major contributor to increased RAW? | The internal diameter of the ET tube; always use the largest appropriate size you can. |
| What are the major clinical conditions that increase RAW in COPD? | Emphysema, Chronic Bronchitis, Asthma, Bronchiectasis |
| What are the major clinical conditions that increase RAW in Mechanical Obstruction? (these are things we can cause!) | Postintubation obstruction, Foreign body aspiration, Endotracheal tube, and Condensation in vent circuit |
| What are the major clinical conditions that increase RAW in Infection? | Laryngotracheobronchitis (croup), Epiglottitis, and Bronchiolitis |
| Bronchiolitis Versus Bronchiectasis | Bronchiolitis = inflammation of the bronchioles Bronchiectasis = abnormal widening of the bronchi or their branches, causing a risk of infection |
| Define "hypoventilation". | Inadequacy of ventilation to remove CO2. The arterial PCO2 is elevated in conditions of hypoventilation. |
| Define "ventilatory failure" | Failure of the resp system to remove CO2 from body, resulting in abnormally high PaCO2. |
| Define "oxygenation failure" | Failure of the heart and lungs to provide adequate O2 for metabolic needs. |
| What is pressure-volume (P-V) loop? | The display on vent system that show a waveform. An increase in bowing = increased RAW. |
| Define "lung compliance" | The degree of lung expansion (volume change) per unit pressure change. Decreased compliance is "stiff lungs". Increased compliance is "flabby lungs". |
| What are the clinical conditions that decrease static compliance? | ARDS, Atelectasis, Tension pneumothorax, Obesity, Retained secreations |
| What are the clinical conditions that decrease dynamic compliance? | Bronchospasm, Kinking of ET tube, Airway obstruction |
| What is refractory hypoxemia? | Persistent low level O2 in blood that isn't responsive to high O2 therapy; Usually caused by intrapulmonary shunting. ie: acute resp distress or ARDS) |
| Since compliance is inversely related to pressure (WOB), a ____________ in compliance means an ___________ in WOB. | decrease ; increase |
| What is dead space ventilation? And what are the three types? | "wasted ventilation"; where ventilation is in excess of profusion. 1) anatomic, 2) alveolar, & 3) physiologic |
| What is considered normal dead space ventilation? | 30%. ie: Vt = 500mL, 150mL is dead space ventilation, doesn't take part in gas exchange. |
| Physiologic dead space Equation | Vd / Vt = (PaCO2 - PeCO2) / PaCO2 PeCO2 is mixed expired gas, collected at the same time as PaCO2 |
| What is normal Vd / Vt ratio? | less than 60% is acceptable |
| What does severe and prolonged dead space ventilation cause? | Ineffective ventilation, muscle fatigue, and vent & oxygenation failure |
| What is the key feature of Ventilatory Failure? | Hypercapnia = increased PaCO2 Hypoxemia can be a secondary complication |
| What are the five (5) mechanisms leading to Vent Failure? | 1) hypoventilation, 2) Persistent V/Q mismatch, 3) Persistent intrapulmonary shunting, 4) Persistent diffusion defect, and 5) Persistent reduction of inspired O2 |
| What is alveolar volume and what is the equation for it? | Alveolar volume is the portion of Vt that takes part in gas exchange; Va = Vt - Vd |
| What is minute alveolar ventilation and what is the equation for it? | Minute alveolar ventilation is a function of Vt, Vd, and RR; Va(with a dot) = VCO2 / PaCO2 |
| When minute alveolar ventilation is low (hypoventilation), the result is........... | an elevated PaCO2 in the ABG. |
| In a healthy person, what is normal physiologic shunt? | less than 5% |
| What are the interpretations of shunt percent? | <10% = Normal, 10%-20% = mild shunt, 20-30% = significant shunt, >30% = critical and severe shunt |
| Classic Physiologic Shunt Equation | Qsp / Qt = (CcO2 - CaO2) / (CcO2 - CvO2) |
| Define Hypoxic hypoxia. | Lack of O2 in organs and tissues due to reduction in inspired O2. |
| Can hypoxia occur in the absence of hypoxemia? | Yes; Hypoxemia reflects the likelihood of hypoxia, but it can occur without it. |
| What is hypoxemia? | Reduced O2 in the blood |
| What is hypoxia? | Reduced O2 in the organs and tissues; HOWEVER, it can occur even with normal PaO2!! |
| What are the clinical signs you have oxygenation failure? (and hypoxia) | Hypoxemia, dyspnea, tachypnea, tachycardia, and cyanosis |
| What is depressed respiratory drive? | These pts may have normal pulmonary function, but the respiratory muscles don't have adequate function. |
| What is excessive ventilatory workload? | Exceeds the pts ability to carry out the workload. |
| What is failure of ventilatory pump? | The structural failure of respiratory system to include the lung parenchyma, respiratory muscles, and thoracic skeletal structures. |
| A shift of the slope (of P-V loop) toward the pressure axis indicates a _______________ in compliance. | decrease |
| A shift of the slope (of P-V loop) toward the volume axis indicates a _______________ in compliance. | increase |
| When the airflow resistance is _______________, the peak insp pressure _____________________, while the plateau pressure ______________. | Increased, is increased, stays the same. |
Created by:
Beccaboop
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