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Exam 3 Mechanical Ventilation
Terms in this set (27)
Indications for Mechanical Ventilation
- Spontaneous ventilation inefficient
- pO2 < 50 mmHg
- pCO2 > 50 mmHg
Why is it important to get enough protein when on a vent?
they'll atrophy if no protein and then they'll never get extubated
What is bunking the vent?
Patient-ventilatory desynchrony aka fighting the vent
- CPAP = when machine just giving O2 and peep
- T piece = get humidified O2 from wall but not extubated yet; last step before extubated
Correct factors before weaning
- HOB 60-70º
- PEEP < 7
- FIO2 < 50%
- get blood gasses with each attempt
- pO2 >60 on FIO2 <50%
- pCO2 < 45 or to baseline
- VE < 10L/min (minute ventilation)
- NIF (MIP) more negative than -20 cm (neg inspiratory force sucked in with huge breath)
- VC > 10 ml/kg
- VT > 5 ml/kg
- RR < 32
Types of Vents
Negative Pressure Ventsterm-3
- Mimics spontaneous respiration; allow airflow into lungs
- Types: Iron lung, Pneumowrap - MD, ALS, Polio
Positive Pressure Vents
1. Volume-cycled = Inspiration terminated when preset VT is delivered
2. Pressure-cycled = when preselected pressure achieved
3. Time-cycled = Inspiration terminated and switched to expiration at a preset time
Modes of Mechanical Ventilation
Continuous mandatory ventilation (CMV), aka assist/control (A/C) ventilation:
- Delivers gas at preset tidal volume or pressure in response to patient's inspiratory efforts and initiates breath if patient fails to do so within preset time.
Intermittent mandatory (IMV), aka synchronous intermittent mandatory ventilation (SIMV):
- Delivers gas at preset tidal volume or pressure and rate, while allowing patient to breathe spontaneously
- ventilator breaths are synchronized to patient's respiratory effort.
Continuous positive airway pressure (CPAP):
- Positive pressure applied during spontaneous breaths; - patient controls rate, inspiratory flow, and tidal volume.
- used in patients to increase functional residual capacity and improve oxygenation by opening collapsed alveoli at end expiration;
- it is also used for weaning.
Pressure support ventilation (PSV):
- Preset positive pressure used to augment patient's inspiratory efforts;
- patient controls rate, inspiratory flow, and tidal volume.
- used as primary mode of ventilation in patients with stable respiratory drive to overcome any imposed mechanical resistance (e.g., artificial airway).
- Advantages include reduced work of breathing and improved patient-ventilator synchrony.
Pressure-controlled inverse ratio ventilation (PC-IRV):
- PC-CMV mode in which inspiratory-to-expiratory (I:E) time ratio is >1 : 1.
- PC-IRV is used in patients with hypoxemia refractory to PEEP; longer inspiratory time increases functional residual capacity and improves oxygenation by opening collapsed alveoli, and shorter expiratory time induces auto-PEEP that prevents alveoli from re-collapsing.
- Requires sedation and paralysis because of discomfort
- Increased intrathoracic pressure can result in excessive air trapping and decreased cardiac output (hypotension)
High-frequency ventilation (HFV):
- Delivers small volume of gas at rapid rate.
- HFV is used in situations in which conventional mechanical ventilation compromises hemodynamic stability
- Patients require sedation and paralysis.
- Contra: increased ICP
Respiratory rate (RR) or frequency (f)
- Number of breaths per minute
Amount of effort the patient must exert to initiate a breath
- Positive pressure during exhalation.
- Prevents alveoli from collapsing; used with other modes of vent.
- (3-10 cm H2O) ≈ 5cm
- Too much Peep = Alveolar Distention, High alveolar pressures, increased intrathoracic pressure (blowing out lungs); pressure on heart → CO drops
Tidal Volume (VT)
- Volume of gas delivered to patient during each breath
- 10-12 ml/kg
- normal = 8ml/kg
Oxygen concentration (FIO2)
- Concentration of room air
- adjusted to maintain PaO2 >60 mm Hg or SpO2 >92%
- duration of inspiration: expiration
- 1:2 unless inverse ratio ventilation
- Speed with which VT is delivered
- slow w/ lots of constriction like asthma
- Max pressure vent can generate to deliver VT.
- When reached inspiration ends
-stop cycle when it hits certain pressure; how much pressure we're willing to tolerate to get in that tidal volume
- Total air moved in or out of lungs in 1 minute
- (VT x f). Normal ~10L;
- if > 10 = hyperventilating = not extubatable
- periodic larger than normal VTs.
- 1-1.5 x VT, 4-5/hr.
- produce surfactant
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