Mechanical Ventilation Lecture Review

Comprehensive vocabulary flashcards covering mechanical ventilation types, variables, clinical parameters, troubleshooting, and pharmacology based on lecture notes.

Trigger Variable

The parameter that starts the inspiratory phase of a positive pressure breath.

Pressure-triggered

Inspiration is initiated by the patient causing airway pressure to drop below the established baseline.

Flow-triggered

Inspiration is initiated by the patient causing inspiratory flow to drop below the established baseline; preferred over pressure triggered.

Time-triggered

Inspiration is initiated by the ventilator; commonly used in infant/baby ventilation.

Control or Target Variable

The primary variable the ventilator adjusts to achieve inspiration, such as Volume control ($VC$) or Pressure control ($PC$).

Limit Variable

Establishes a maximum value a variable (pressure, volume, time, flow) can reach during inspiration; it does not end inspiration but results in a plateau.

Cycling Variable

The variable that ends (terminates) the inspiratory phase of a positive pressure breath.

Volume Cycled

Pressure is applied to the airways until a preset volume is delivered; the most common cycling variable during $VC$ ventilation.

Pressure Cycled

Positive pressure is applied until a preset pressure value is reached; used during $IPPB$ and can serve as an alarm safety mechanism.

Flow Cycled

Positive pressure is applied until a predetermined flow is achieved; the normal cycling mechanism in Pressure Support Ventilation.

Spontaneous Breath

A breath where the patient controls all variables pertaining to each breath.

Mandatory Breath

A breath where the ventilator controls all variables pertaining to the breath.

Assisted Breath

A breath where the patient initiates (triggers) the breath and then the ventilator controls the remaining variables.

High Pressure Alarm

Should be set $10\text{ cm H}_2\text{O}$ above peak airway pressure.

Low Pressure Alarm

Should be set $10\text{ cm H}_2\text{O}$ below peak airway pressure; used to detect patient disconnect or leaks.

Apnea

An absolute indication for continuous mechanical ventilation where the patient is not breathing.

Vital Capacity (VC)

An assessment of bedside ventilatory parameters where a value $< 10\text{ mL/kg}$ is unacceptable.

Maximum Inspiratory Pressure (MIP)

Measures respiratory muscle strength; an unacceptable value is $< 20\text{ cm H}_2\text{O}$. Also known as Negative Inspiratory Force ($NIF$).

Minute Ventilation ($V_E$)

Calculated as $V_t \times f$; a value $> 10\text{ L/min}$ is considered unacceptable.

Static Compliance ($C_{st}$)

Calculated by $\frac{\text{Exhaled Volume}}{\text{Plateau Pressure} - \text{PEEP}}$; normal values are $60 - 100\text{ mL/cm H}_2\text{O}$.

Ideal Body Weight (IBW) Formula (Male)

$50\text{ kg} + (2 \times \text{inches over 5 ft})$.

Initial Tidal Volume Setting

Typically $5 - 10\text{ mL/kg}$ of ideal body weight; severe asthma patients should start at $4\text{ mL/kg}$.

Alveolar Minute Ventilation ($V_A$)

Calculated as $(V_t - V_d) \times f$, where anatomical deadspace ($V_d$) is estimated at $1\text{ mL per lb}$ of ideal body weight.

Airway Resistance ($Raw$)

The frictional force overcome during breathing; estimated as $\text{PIP} - \text{Plateau}$. Normal is $0.6 - 2.4\text{ cm H}_2\text{O/L/sec}$.

Mean Airway Pressure ($P_{aw}$)

The average pressure transmitted to the airway from the start of one breath to the next; primarily affects oxygenation.

Work of Breathing (WOB)

Calculated by $\text{Change in Pressure} \times \text{Change in Volume}$ ($\triangle P \times \triangle V$); normal value is $0.5 \times 0.2\text{ Joules/L}$.

Inverse Ratio Ventilation (IRV)

Uses an $I:E$ ratio of $2:1$ or greater; recommended for patients with high $PIP > 50\text{ cm H}_2\text{O}$ or high $F_iO_2 > 60\%$.

Pressure Regulated Volume Control (PRVC)

A form of ventilation that keeps pressure at the lowest level while providing automatic, breath-to-breath pressure regulation to achieve a preset volume.

High Frequency Oscillatory Ventilation (HFOV)

Oscillates gas at $3 - 15\text{ Hertz (Hz)}$; useful for severe lung injury like ARDS or air leak syndromes like Bronchopleural fistula.

ARDSnet Protocol

Initial tidal volume of $8\text{ mL/kg IBW}$, reduced to $6\text{ mL/kg IBW}$, maintaining plateau pressure $< 30\text{ cm H}_2\text{O}$.

Recruitment Maneuver (RM)

A sustained increase in pressure (e.g., $40\text{ cm H}_2\text{O}$ PEEP for $40\text{ seconds}$) with the goal of opening collapsed lung units.

Prone Positioning

Placing a patient face down to increase $PaO_2$ and decrease shunt; considered when $F_iO_2 > 60\%$ and $PEEP > 12\text{ cm H}_2\text{O}$.

Scalar Graphics

Waveforms that plot flow, airway pressure, or volume on the vertical ($Y$) axis against time on the horizontal ($X$) axis.

Auto-PEEP

Also called intrinsic PEEP or dynamic hyperinflation; occurs when expiratory flow does not return to zero before the next breath due to insufficient expiratory time.

Trigger Asynchrony

Occurs as missed triggers (insensitive setting/Auto-PEEP) or auto-trigger (leaks/oversensitive setting).

Benzodiazepines (Sedatives)

Agents like Alprazolam (Xanax), Diazepam (Valium), and Midazolam (Versed) used to decrease anxiety.

Neuromuscular blocking agents

Agents such as Pancuronium (Pavulon), Vecuronium (Norcuron), and Rocuronium (Zemuron) that cause paralysis of skeletal muscle.