Tidal Volume (Vt)
How much air the patient breathes in a normal breath.
(Excessive Vt can cause ventilator-induced lung injury)
Inspiratory Reserve Volume (IRV)
The amount of air that can be forcefully inhaled in addition to a normal tidal volume breath
Expiratory Reserve Volume (ERV)
The amount of air that can be forcefully exhaled after a normal tidal volume breath.
Vital Capacity (VC)
Vt + IRV + ERV
Residual Volume (RV)
The amount of air left in the respiratory tract following forceful exhalation.
Total Lung Capacity (TLC)
IRV + Vt + ERV + RV
The surfaces of the airway that are not involved in gas exchange
Dead Space = 2mL/kg
Located in the medulla/pons
Driven by CO2 and H+ levels
Located in the aortic arch/carotid bodies
Response is driven by O2, CO2 and H+
Used to tell how much O2 a person is using. Cardiac ouput measurement based on the principle that oxygen uptake by the lungs equals oxygen delivery.
Nuclear medicine study used to evaluate circulation of air and blood within the lungs to determine the V/Q ratio.
Hypercarbic Respiratory Failure
Inability to remove CO2
Indicated By - Respiratory Acidosis
Treatment - Increased Vt then rate
Hypoxic Respiratory Failure
Inability to Diffuse CO2
Indication - Low PaO2
Treatment - Increased Vt, O2 concentration, then rate
Abnormal breathing pattern characterized by a deep, gasping inspiration with a pause at full inspiration, followed by a brief, insufficient release.
(Associated with decerebrate posturing)
Abnormal pattern of breathing characterized by compolete irregularity of breating, with irregular pauses and increasing periods of apnea.
(Caused by damage to the medulla)
Abnormal pattern of breathing characterized by groups of quick, shallow inspirations followed by regular or irregular periods of apnea.
Progressively deeper and sometimes faster breathing, followed by a gradual decrease that results in temporary apnea.
(Brainstem herniation, decorticate posturing)
Respirations gradually become deep, labored and gasping. Associated with DKA.
The patient's breathing rate (F) and tidal volume (Vt) is controlled completely.
The patient can take intermittent breaths (between the controlled breaths).
The ventilator synchronizes delivery of breath with the patient's inspiratory drive.
The ventilator assists the patient with their breathing (must have intact respiratory drive).
Ventilator Acquired Pneumonia (VAP)
#1 cause of iatrogenic death in the US
Tick marks seen on capnography, patient is choking. Check ETT. Patient needs to be resedated and reparalyzed.
Tidal Volume (Vt) Setting
Minute Volume (Ve)
F x Vt (4-8 L/min)
Inspiratory: Expiratory Ratio (I:E)
Fraction of Inspired Oxygen (FiO2)
Plateau Pressure (Pplat)
< 30 - respresents the static ensd inspiratory recoil pressure of the respiratory system, lung and chest wall respectively.
Positive End Expiratory Pressure (PEEP)
Keeps alveoli so that oxygen can diffuse, prevents atalectasis.
Peak Expiratory Flow Rate (PEFR)
500 to 700 L/min for males, 380 to 500 L/min for females.
A person's maximum speed of expiration, as measured with a peak flow meter.
Controlled Mandatory Ventilation (CMV)
- Used in sedated, apneic or paralyzed patients
- All breaths are triggered, limited, and cycled by the ventilator
- Patient has no ability to initiate own breaths
Synchronized Intermittent Mandatory Ventilation (SIMV)
- Assisted mechanical ventilation synchornized with the patient's breathing
- Ventilator senses the patient taking a breath, then delivers a breath.
- Spontaneous breathing by the patient occurs between the assisted breaths which occur at preset intervals
- Preferred in patients with an intact respiratory drive
Assist-Control Ventilation (AC)
- The trigger for delivery of a breath can be either the patient or elapsed time
- Ventilator supports every breath, whether it's initiated by the patient or the ventilator
- Used in ARDS, paralyzed or sedated patients
- Anxious Patient - can breath-stack/auto-PEEP - Can cause VILI
Pressure Support Ventilation (PSV)
- Makes it easier for the patient to overcome the resistance of the ETT and is used during weaning
- Reduces work of breathing
- Patient determines tidal volumes, rate (minute volume)
- Requires consistent ventilatory effort by the patient
Similar to SIMV because they are all spontaneously triggered by the patient
The use of continuous positive pressure to maintain a continuous level of PEEP. Mild air pressure to keep an airway open.
Uses alternating levels of PEEP to maintain oxygenation, commonly used in pneumonia, COPD, asthma, etc.
Low Pressure Alarm Causes
- Patient disconnection from machine
- Chest tube leaks
- Circuit Leak
- Airway Leak
High Pressure Alarm Causes
- Kinked Line
- Patient biting the tube
- Reduced lung compliance
- Increased Airway Resistance
COPD patients with chornic bronchitis
COPD patients with emphysema. Color is pink due to polycythemia vera.
COPD CXR Findings
Flattened diaphragm, chest cavity is over expanded due to air trapping.
- Often viral, sometimes bacterial
- CXR shows pleural effusions, lobar consolidation
- Right middle lobe pneumonia is most common site
Acute Respiratory Distress Syndrome
- CXR - ground glass appearance, patchy infiltrates, bilateral diffuse infiltrates
- Swann-Ganz - increased PAWP (high pressure because right heart is pumping against increased pressure in the lung vasculature)
- Tx: High PEEP, High Vt