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MechVent 1
mechanical ventilation basics
Question | Answer |
---|---|
Describe dynamic compliance? | the amount of force needed to overcome airway resistance and inflate the lung w/ a volume. (= Vt/PIP-PEEP) |
Describe static compliance? | inspiratory hold of air w/ a Pplat giving the C of the lungs. (= Vt/Pplat-PEEP) |
How will Cstat and Cdyn change under ↑ Raw and stiffness? | They will become less compliant |
What changes in pt’s status can affect Cstat and Cdyn? | Cstat will decrease w/ resistance or ↑ w/ air-trapping; Cdyn will decrease or become less C w/ an obstruction |
Define the term “cycle” | end of inhalation (i.e. machine stops at end of inhalation) |
List the various factors used to trigger ventilator breaths. | Pressure and Flow (pt.), Timed (vent.), Manuel (operator) |
Describe mean airway pressure, | the pressure maintained in the airways in an entire respiratory cycle. ↑in Paw then an ↑ in PaO2 |
What ventilator parameters (i.e. PEEP, Ti) that affects Paw. | Can be increased w/ PIP, PEEP***, I-Time. |
What is the advantage of SIMV vs. IMV? | SIMV prevents breath stacking, IMV will give a pt a breath no matter where they are in a spontaneous breath. |
What blood gas value is the primary indicator of adequate ventilation? | PaCO2 |
Describe the possible negative impacts of PEEP therapy. | barotraumas, ↓ venous return, Qt and renal blood flow, ↑ WOB, PVR, ICP, deadspace, mean airway pressure. |
Describe the negative physiological effects of positive pressure vent. | barotraumas*, ↓ venous return, Qt*, renal blood flow, urine output, and gastrointestinal function (due to ↓ blood flow), also an ↑ in ICP, PVR, deadspace and mean airway pressure. |
What will be the result of an ↑ Raw or a ↓ in compliance on a volume cycled ventilator? | Volume stays and pressure changes. |
What will be the result of an ↑ Raw or a ↓ in compliance on a pressure, time cycled ventilator? | Pressure, time stays the same as volume ↓’s. Less VE then pt could become hypercapnic |
HME % humidity? | 70% |
Heated Wick % humidity? | 100% |
High Pressure Alarm Setting? | 10 above pt's set PIP |
High rate alarm setting? | 35 |
Low Volume alarm setting? (on assist control and SIMV) | 10-15 below set Vt |
Low minute ventilation alarm setting? | 4 |
Apnea alarm setting? | < 20 sec |
I:E alarm setting? | I is > E (check peak flow) |
What are the various ways you can adjust I:E on a vol-cycled vent? | flow* or I-Time* or Vt or even RR (changes TCT) |
Highest PIP on a volume ventilator that can occur before possible damage? | 30 |
Maximum setting that should be selected for the high respiratory rate alarm? | 30 |
What FIO2 limit is considered dangerous in regards to possible O2 toxicity? | 0.50 % |
What settings on a ventilator are used to ↑ or ↓ the PaO2? | FIO2, PEEP, I-Time |
Describe how PEEP ↑ blood oxygenation. | alveoli recruitment by allowing positive pressure at the end of expiration before inhalation restoring a person’s FRC. |
Describe how ↑ the TI can improve blood oxygenation. | this allows for a longer inhalation time for longer contact time for diffusion to take place. |
Calculate the corrected Vt for the following pt: PIP = 50, Cmech = 2.5 ml/cmH20, delivered Vt = 900 ml. | 1. Ct=Vol/P 2. V-lost= Ct x pt’s Pip 3. Corrected Vt= Vt - V-lost (775) |
What is the appropriate action for any ventilator problem that is not immediately identified and corrected? | remove from ventilator and begin bagging the pt. |
What ventilator changes could be made to correct a respiratory acidosis? | Increase Vt or RR (Adjust Vt first, but if Vt is ideal then go w/ RR) |
What ventilator changes could be made to correct a respiratory alkalosis? | decrease Vt or RR |
What 3 changes could be made to correct a low PaO2? | Increase concentration (FIO2), Increase lung diffusion area (inspiratory time or PEEP) |
What 2 changes could be made to correct a high PaO2? | ↓ FIO2 and/or I-Time |
What is the goal for the PaCO2 and pH when mechanically ventilating a COPDer w/ chronic hypercapnea? | get them to their baseline (Pa CO2 are usually acidic and ph as well) |
Identify the normal Vt ranges. | 6-10 ml/kg |
What factors are to be optimized before considering a pt. for weaning off a vent? | Is the problem that caused the respiratory failure resolved (Primary)? Blood gases stable? (PaCO2 baseline,PaO2 adequate on .40 or less), Cardiac condition stable? Is the patient afibrile? Respiratory mechanics stable? Proper nutrition and sleep? |
Describe the criteria (tests) that are done daily w/ pt.’s undergoing weaning from a vent. (+ values) | RSBI 105(predicts spontaneous breathing), SBT, MEP + 40,MIP = >-20 to -30 cmH2O, VE = < 10 L, VC = >10 – 15 ml/Kg, Spontaneous tidal volume = > 300 ml, Respiratory rate = < 25/min |
Describe how a pt is weaned using SBT trials. | Spontaneous breathing trial, off vent w/ T-Piece/CPAP (both spontaneous), SIMV (decrease to 2), PSV (basically CPAP) |
Describe how a pt is weaned using SIMV. | Gradual ↑ on pt’s ventilatory load by decresing the rate, Machine breaths are decreased by 2 breaths at a time (incremental changes), Patient takes over with spontaneous efforts to maintain the VE needed to stabilize PaCO2 |
Why would PSV be added to this mode? | PSV can be added to help “fine tune” incremental changes and maintain adequate spontaneous Vt (>300 ml) |
What is the most common setting for initiation of apnea ventilation? | 20 seconds |
What techniques are used to monitor the possible cardiac effects from positive pressure ventilation? | A-line, Continuous BP monitor, Swan-Ganz |
Describe possible advantages of pressure control ventilation over volume control ventilation. | prevent barotrauma |
What is the rationale for permissive hypercapnea? | think barotrauma; only let go of maintaining CO2 for the sake of the lungs. |
Describe the 2 diff types of res. failure. What disease processes are associated w/ each? | Type I: Hypoxic Type II: Hypercapnic |
A/C mode, 600 Vt w/ a rate of 12, w/o spont.efforts: 7.25/CO2 55/HCO3 23/PaO2 80/ at an FIO2 .35 | Respiratory Acidosis w/ normal oxygenation; Increase Vt or RR. |
A/C mode, 600 Vt w/ a rate of 12, w/o spont.efforts: 7.37/CO2 55/HCO3 32/PaO2 50/ at an FIO2 .35 | Compensated Respiratory Acidosis w/ moderate hypoxia; Increase FIO2 |
A/C mode, 600 Vt w/ a rate of 12, w/o spont.efforts: 7.51/CO2 25/HCO3 23/PaO2 90/ at an FIO2 .45 | Respiratory Alkalosis w/ normal oxygenation; Decrease VE (Vt or RR) or sedate w/ propaphal |
A/C mode, 600 Vt w/ a rate of 12, w/o spont.efforts: 7.38/CO2 43/HCO3 22/PaO2 120/ at an FIO2 .65 | Normal ABG; except the PaO2, so lower the FIO2. It's over the toxic level anyway. |
A/C mode, 600 Vt w/ a rate of 12, w/o spont.efforts: 7.36/CO2 65/HCO3 38/PaO2 100/ at an FIO2 .45 (COPD pt being considered for weaning) | Compensated Respiratory Acidosis w/ normal oxygenation; don't touch the PaCO2. However, the O2 is at toxic level for a COPDer. Drop FIO2 until he starts to breath on his own. |