Review for RESP 340 Final

Modes

CMV - Continuous Mandatory Ventilation

1. AKA Assist/Control
2. Patient triggered or ventilator triggered machine breaths.
   • Machine breaths are defined as an inspiration in which the ventilator settings determine the inspiratory phase (pressure or flow waveforms) and the way inspiration ends.
   • Machine breaths are volume controlled, pressure controlled, or volume-targeted pressure controlled.
   • The patient can initiate a machine breath by creating a drop in flow (flow trigger) or a drop in pressure (pressure trigger).
   • The ventilator will initiate a machine breath if the patient does not trigger a breath during the period of time set by the Breaths/Min.
3. The ventilator settings for a machine breath depend on whether the breath is volume or pressure controlled.

Volume Controlled Settings BPM Tidal Volume or Minute Volume Peak flow or Inspiratory Time % Pause time or Pause Time % Flow waveform Sighs (optional)

Pressure Controlled Settings BPM Inspiratory Time or Inspiratory Time % OR I:E Ratio (7200) Inspiratory Pressure Level Pause Time % (900C) To increase tidal volume in pressure control mode: Increase inspiratory time if flow waveform truncated and if a longer IT will not cause breath-stacking (air-trapping).. Increase level of pressure control if inspiratory pressure minus PEEP will remain less than 30 cm H20. To increase minute ventilation and lower PaCO2: Increase tidal volume (see above). Increase BPM if that does not cause breath=stacking (air-trapping).

• FIO₂

• PEEP (as needed)

• Alarms

SIMV - Synchronized Intermittent Mandatory Ventilation

1. SIMV - Machine breaths at a fixed BPM. Any additional patient inspiratory effort will result in spontaneous breaths.
2. Machine breaths may be volume controlled or pressure controlled
3. Spontaneous breaths may be with CPAP and/or Pressure Supported

CPAP

1. Spontaneous breaths defined as patient triggered and cycled occurring at a baseline pressure above zero.
2. May be Pressure Supported

Important issues of volume controlled ventilation

1. Is alveolar ventilation adequate? ( > 35 PaCO₂ < 45) Ideally 35-38 normally.
2. Is oxygenation adequate? ( > 60 PaO₂ < 100 on < .60 FIO2)
3. Is acid/base problem respiratory or metabolic?
4. Is peak flow high enough to meet patient's inspiratory needs without being excessive? (Airway pressure instantly rises with patient inspiratory effort)
5. Is the I:E Ratio small enough to allow adequate time for exhalation? (Exhaled tidal volume = inhaled tidal volume)
6. Is the plateau pressure - PEEP < 30 cm H₂0? Is the peak pressue < 50 cm H₂0? Is patient triggering a problem? (Sedate/paralize patient or change to SIMV mode)
7. Are the ventilator alarms set properly?

Calculations for Volume Controlled Ventilation

1. VE = VT x BPM
   • VT = VE/ BPM
   • BPM = VE/ VT
2. VT = peak flow x inspiratory time
   • Peak flow must be in L/sec or ml/sec
   • Inspiratory time must be in seconds.
3. Inspiratory time = tidal volume / peak flow
   • Peak flow must be in L/sec or ml/sec
   • Inspiratory time must be in seconds.
   • Tidal volume must be in units that match peak flow (liters or ml)
4. Peak flow = tidal volume/ inspiratory time
5. I:E Ratio E = ET/ IT
   • IT + ET = total cycle time
   • total cycle time = 60/ BPM
   • Inspiratory time includes pause time when calculating I:E Ratio

Considerations for pressure controlled ventilation.

1. Do you expect the patient's compliance and/or resistance to change quickly? Monitor volumes.
2. Control inspiratory time unless in inverse ratio ventilation.
3. Set Low Tidal Volume alarm closely.
4. Cannot guard against high tidal volumes with the 7200 (there's no high minute volume alarm - Only the NPB 840 has a high minute volume and a high tidal volume alarm), if the patient's compliance should drastically change.
5. If inspiratory pressure gradient would have to be greater than 30 cm H₂0 to maintain normal PaCO₂, allow PaCO₂ to gradually increase (permissive hypercapnia).