Therapeutics Pulmonary Ronald Flashcard

Based on Arterial Blood Gas, how do you differentiate between Hypercapnic Respiratory Failure and Hypoxic Respiratory Failure?

Hypercapnic Respiratory Failure

  • Progressive increase in PaCO2 –> respiratory acidosis
  • PaCO2 > 50 mmHg and pH < 7.35


Hypoxic Respiratory Failure

  • Progressive decrease in PaO2 due to ventilation/perfusion (V/Q) mismatch
  • PaO2 < 60 mmHg

Hypercapnic Respiratory Failure: Etiologies

Increase CO2 Production

  • Fever
  • Seizures
  • Sepsis
  • Increased carbohydrate load

Can’t Breathe! (V/Q mismatch — increased dead space)

  • COPD
  • Asthma
  • Cystic Fibrosis
  • Pulmonary Fibrosis
  • Obstructive Sleep Apnea
  • Respiratory Muscle Fatigue

Won’t Breathe! (Hypoventilation — decrease minute ventilation)

  • Drug overdose
  • CNS disorders
  • Central Sleep Apnea

Hypoxic Respiratory Failure: Etiologies


  • Acute MI
  • Left Ventricular Failure
  • CHF exacerbation
  • Mitral stenosis
  • Mitral regurgitation
  • Diastolic dysfunction


  • Pneumonia
  • Acute Respiratory Distress Syndrome (ARDs)
  • Sepsis/Septic Shock
  • Chemical Aspiration
  • Pulmonary embolism
  • Pancreatitis

Respiratory Terminology: Tidal Volume

  • The amount of air inhaled or exhaled with each normal breath
  • Avg healthy person (non-ventilated) = ~500 ml, or 5-7 ml/kg (IBW)
  • Estimated initial VT for ventilated patients = 6-10 ml/kg (IBW)
  • Excessively large tidal volumes can lead to hyperinflation of the lungs and ventilator-induced lung injury

Respiratory Terminology: Respiratory Rate

  • Breaths/min
  • Typical initial ventilator rate 12-16 bpm
  • Patients with restrictive lung disease may require higher initial respiratory rates (16-20 bpm)
  • Patients can set their own respiratory rate by breathing above the set number of breaths the ventilator provides
  • ↑ RR –> ↑ respired CO2 –> ↓ PaCO2

Respiratory Terminology: Fraction of Inspirated Oxygen

  • Percentage of O2 delivered to patient
  • Room air = FiO2 21%
  • On mechanical ventilation — FiO2 can range from 21-100%
  • GOAL — to provide lowest FiO2 to maintain adequate PaO2 (> 60 mmHg)
  • FiO2 is usually started at 100% and decreased to maintain an adequate PaO2 > 60-70 mmHg
  • High FiO2 for long periods of time increases the risk of O2 toxicity (direct lung injury, CNS effects, retinal effects)

Respiratory Terminology: Positive End-Expiratory Pressure

  • Pressure held in the lungs during exhaled
  • Helps to increase the surface area of the alveoli
  • Prevents the alveoli from collapsing during exhalation
  • PEEP can help reduce O2 requirements  — by increasing PEEP, you can decrease FiO2 due to increase surface area of alveoli recruited for oxygenation
  • Typically — PEEP < 5 cm H2O?????

Respiratory Terminology: Minute Ventilation

  • Amount of air inhaled or exhaled per one minute
  • Normal VE = 5-8 L/min
  • Increase minute ventilation = increased respiratory CO2 excretion (hyperventilation)

What are the different types of Non-Invasive Mechanical Ventilation?

  • Continuous Positive Airway Pressure (CPAP)
  • Bilevel Positive Airway Pressure (BiPAP)

Continuous Positive Airway Pressure

Non-Invasive Mechanical Ventilation

  • Constant level of positive pressure is applied throughout inspiration and expiration
  • An air splint that holds your airway open
  • Common use = obstructive sleep apnea
  • Typical setting = 2.5-15 cm H2O
  • Oxygen can be titrated into the circuit to alleviate hypoxemia

Bilevel Positive Airway Pressure

Non-Invasive Mechanical Ventilation

  • Continuous pressure that cycles between high and low pressure levels
  • Delivers CPAP but also senses when an inspiratory effort is being made and delivers a higher pressure during inspiration
  • When flow stops (end of inspiration), the pressure returns to the CPAP level
  • This positive pressure wave during inspiration unloads the diaphragm and decreases the work of breathing
  • A back up mandatory respiratory rate can be set (> 12 bpms)
  • Oxygen can be titrated into the circuit to help with hypoxemia

Indications for Bilevel Positive Airway Pressure

  • COPD with hypercapnea
  • Acute pulmonary edema (CHF exacerbation)
  • Those who refuse intubation
  • A step-down from the ventilator for COPD or CHF patients

What are the two pressures used in Bilevel Positive Airway Pressure?

  • Inspiratory Pressure — pressure support ventilation
  • Expiratory Pressure — CPAP level (air stent)

What are the types of Invasive Mechanical Ventilation?

  • Assist Control Ventilation (A/C) — Volume Control
  • Synchronized Intermittent Mandatory Ventilation
  • Pressure Support/Control Ventilation

Assist Control Ventilation

Invasive Mechanical Ventilation

  • Volume control
  • A predetermined respiratory rate and tidal volume are set on the ventilator
  • Chosen initially when starting invasive mechanical ventilation
  • Patient triggers a supported breath by beginning to inhale
  • On assisted breaths the work of breathing is shared between the patient and the ventilator
  • The machine delivers the set tidal volume on each breath — tidal volume is constant despite the breath being initiated by the patient or the machine
  • A back-up respiratory rate is set in case the patient makes a decreased effort to breathe or becomes apneic
  • The patient has the ability to control his/her own respiratory rate
  • Useful when intent is to have the ventilator assume most or all of the work of breathing

Synchronized Intermittent Mandatory Ventilation

Invasive Mechanical Ventilation

  • A predetermined respiratory rate and tidal volume are set on the ventilator
  • No assist from the ventilator is provided beyond the pre-set number of breaths initially set on the ventilator (RR)
  • If patient breaths > than the pre-set RR, those breaths will be whatever tidal volume the patient can achieve on their own
  • The patient can “breathe around” the ventilator and set his/her own respiratory rate
  • Synchronized = the machine-assisted breaths occur simultaneously with patient effort and prevents a ventilator-delivered breath in the middle of a patient-delivered breath

Pressure Support/Control Ventilation

Invasive Mechanical Ventilation

  • Ventilator responds to a patient’s inspiratory effort by increasing the pressure to a pre-specified level
  • Pressure is increased or decreased depending on patient’s ventilator status
  • Patient provides the needed work of breathing (respiratory rate and tidal volume)
  • Like breathing on a scuba tank
  • Used either as a primary ventilator support or as a tool for assessing a patient’s readiness for extubation from the ventilator

Parameters used to assess readiness for weaning

  • RR < 25-30 breaths/min
  • Tidal volume > 5 ml/kg
  • Minute ventilation < 10 L/min — takes both RR and Tidal Volume into account

For a patient on a ventilar, what would you need to change in order to alter the patients PaCO2 levels?

Tidal Volume or RR


Can change Tidal Volume or RR by increasing minute ventilation

For a patient on a ventilar, what would you need to change in order to alter the patient’s PaO2 levels?

Change PEEP and FiO2


Increasing both will increase PaO2

Effects of Positive Pressure Ventilation of Physiology


  • Decreased preload, stroke volume, and cardiac output
  • Putting positive pressure in the chest and pressure on the vena cava which can lead to a decrease in preload


  • Incidence of stress ulcers and sedation-related ileus is increased


  • May decrease venous return from the head, increasing intracranial pressure (caution in head injury) and worsening agitation, delirium, and sleep deprivation

Complications of Mechanical Ventilation

  • During Endotracheal Intubation — upperairway and nasal trauma, oral-pharyngeal lacerations, tooth avulsions, hematoma of vocal chords, etc.
  • Barotrauma
  • Volutrauma
  • Ventilator-Associated Pneumonia
  • Oxygen Toxicity
  • Auto-PEEP
  • Prolonged use of endotracheal tubes — sinusitis, tracheal necrosis or stenosis, glottic edema

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