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Ventilator Cheat Sheet (DRAFT) by

ACNP CheatSheet

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Lung Physiology

Ventil­ation
• To lower PaCO2, one must either increase RR or increase tidal volume.
• Minute ventil­ation = RR x VT**.
Oxygen­ation
• Monitored by O2 saturation and PaO2.
• To increase PaO2 in the ventilated patient, one must either increase FiO2 or PEEP.
• Can also extend inspir­atory time fraction.
• Can improve oxygen delivery by increasing CO or hemoglobin.
• Can decrease oxygen requir­ements by decreasing work of breathing, agitation or fever.
• Remove pulmonary vasodi­lators like nitrop­rus­side.

Key Terms

Minute Ventil­ation
• RRxVT. Should be adjusted to achieve baseline PaCO2.
• Initial VT of 8-10mL/kg is approp­riate in most cases (lower in ARDS and COPD).
• A rate of 10-12 breath­s/min is approp­riate.
FiO2
• Initially should be 100%.
• Quickly titrate down and use the lowest possible level to maintain a PaO2 of 50-60 or higher.
• Avoid oxygen toxicity with FiO2<60% if possible.
• If FiO2 of 0.5 does not result in adequate PaO2, add PEEP or CPAP (allow reduction in FiO2).
Inspir­ato­ry/­exp­iratory ratio
• Duration of time allotted to inspir­ation compared to expiration in one delivered breath. Duarte of each breath is determined by set RR. Increased time in inspir­ation will propor­tio­nally decrease tie-in expira­tion. 1:2 is usually used.
PEEP
• Positive pressure maintained at the end of passive exhalation to keep alveoli open.
• 2.5-10cm H2O is the initial setting.
• Can be added to any mode of ventil­ation and used mostly in hypoxic respir­atory failure.
• Increases lung compliance and oxygen­ation (improves gas exchange).
• Prevents alveolar collapse and atelec­tasis.
• Can cause barotrauma or low CO (due to decreased venous return and increased PVR, esp. with hypovo­lemia).
 

Mechanical Ventil­ation

Indica­tions
• Signif­icant respir­atory distress or respir­atory arrest.
• Impaired or reduced level of consci­ousness with inability to protect the airway (absent gag or cough reflex).
• Metabolic acidosis without adequate compen­sation.
• Respir­atory muscle fatigue.
• Signif­icant hypoxemia (PaO2<­70mmHg) or hyperc­apnia (PaCo2­>50­mmHg).
• Respir­atory acidosis (pH<7.2) with hyperc­apnia.

Compli­cations

Compli­cations
• Anxiety and discomfort treated with sedation.
• Tracheal secretions need regular suction.
• Nosocomial pneumonia (if >72 hours), accidental extuba­tion,
• Barotrauma (high P)
• Oxygen toxicity (if FiO2>60% for >2 days).
• Hypote­nsion (high intrat­horacic pressure decreases VR).
• Trache­oma­lacia (softening of cartilage) due to prolonged ETT. Prevent with trache­ostomy if >2w­eeks.
• Laryngeal damage, GI effects (stress ulcers, choles­tasis).

Compli­cations

Compli­cations
• Anxiety and discomfort treated with sedation.
• Tracheal secretions need regular suction.
• Nosocomial pneumonia (if >72 hours), accidental extuba­tion,
• Barotrauma (high P)
• Oxygen toxicity (if FiO2>60% for >2 days).
• Hypote­nsion (high intrat­horacic pressure decreases VR).
• Trache­oma­lacia (softening of cartilage) due to prolonged ETT. Prevent with trache­ostomy if >2w­eeks.
• Laryngeal damage, GI effects (stress ulcers, choles­tasis).
 

Modes

Assisted Controlled Ventil­ation
• Initial mode used in respir­atory failure.
• Guarantees a "­bac­kup­" minute ventil­ation.
• The ventilator delivers a breath of predet­ermined tidal volume when the patient initiates a breath.
• If the patient does not initiate a breath, the ventilator takes control and delivers a breath at a predet­ermined rate.
• All breaths are deviled by the ventilator.
• The patient can go over the determined rate but not under, and every breath is a determined TV.
Synchr­onous Interm­ittent Mandatory Ventil­ation
• Patients can breath above the mandatory rate without help from the ventil­ator.
• The tidal volume of extra breaths is not determined by the ventil­ator.
• When the patient breathes sponta­neo­usly, there is no preset volume, but the patient has a guaranteed predet­ermined rate.
• Delivers the mandatory breath in synchrony with patient's initiated sponta­neous breath (so they do not overlap).
• Good for support of ventil­ation and weaning.
Continuous Positive Airway Pressure (CPAP)
• Positive pressure (0-20cm H2O) is delivered contin­uously during expiration and inspir­ation, but no volume breaths are delivered.
• The patient breaths on their own.
• The only parameters to set are PEEP and pressure support.
• If the patient is being weaned, CPAP can be used to assess whether they can be extubated.
Pressure Support Ventil­ation
• Mostly during weaning trials.
• Pressure is delivered with an initiated breath to assist breathing.
• Pressure is not continuous and only responds to initiated breaths.
• It enhances respir­atory efforts made by the patient.
• PEEP may be added.