Oxygenation & Gas Exchange

What is pulmonary edema?

• Fluid builds up in the alveoli and interstitial spaces of the lungs.

• This interferes with normal oxygen and carbon dioxide exchange.

• The most common cause is left-sided heart failure.

• The extra fluid makes it harder for oxygen to move into the blood.

What would you hear with pulmonary edema?

• Rales/crackles on auscultation.

• Crackles occur because fluid is present in the lungs.

• Other findings:

  • Shortness of breath

  • Tachypnea

  • Hypoxemia

  • Frothy secretions

What is a pleural effusion?

• Fluid collects in the pleural space around the lungs.

• The fluid takes up space and limits normal lung expansion.

• The patient may develop:

  • Dyspnea

  • Cough

  • Inspiratory chest pain

What would you hear with a pleural effusion?

• Diminished or absent breath sounds over the affected area.

• Fluid around the lung prevents normal transmission of breath sounds.

• Patient may also have:

  • Dyspnea

  • Cough

  • Inspiratory chest pain

What is atelectasis?

• Partial or complete collapse of the lung.

• The alveoli become deflated.

• The most common cause is airway obstruction from retained secretions/exudates.

• Common after surgery or with hypoventilation.

What are the signs and symptoms of atelectasis?

• Rapidly developing atelectasis:

  • Sudden dyspnea

  • Pain

  • Cyanosis

• Slowly developing atelectasis:

  • May be asymptomatic

  • Mild shortness of breath

  • Cough

• Breath sounds may be diminished or absent.

What is the V/Q ratio?

• V = ventilation, or air reaching the alveoli.

• Q = perfusion, or blood reaching the alveoli.

• It compares the amount of air reaching the alveoli with blood flow.

• Normal V/Q is about 0.80.

• Approximately 4 L of air : 5 L of blood.

What causes a high V/Q ratio?

• More ventilation or less perfusion.

• There is air reaching the alveoli, but not enough blood to pick up oxygen.

• Called dead space.

• Example: pulmonary embolism, where blood flow is decreased.

What causes a low V/Q ratio?

• Less ventilation or more perfusion.

• Blood reaches the alveoli, but there is not enough air for gas exchange.

• Called a shunt.

• Example: asthma, where ventilation is decreased.

What are the 2 types of acute respiratory failure?

• Hypoxemic respiratory failure

  • Problem getting oxygen into the blood.

  • PaO₂ is low.

• Hypercapnic respiratory failure

  • Problem removing CO₂ from the blood.

  • PaCO₂ is elevated.

• A patient can have both hypoxemia and hypercapnia.

What is hypoxemic respiratory failure?

• Also called lung failure.

• The lungs cannot adequately transfer oxygen into the blood.

• PaO₂ <60 mmHg.

• PaCO₂ is usually normal or low.

• Caused by problems such as:

  • V/Q mismatch

  • Pulmonary edema

  • Atelectasis

  • Right-to-left shunt

What is hypercapnic respiratory failure?

• Also called ventilation failure.

• The patient cannot adequately remove CO₂.

• PaCO₂ becomes elevated.

• CO₂ buildup causes respiratory acidosis.

• Often occurs from inadequate ventilation or respiratory pump failure.

What causes hypercapnic respiratory failure?

• Decreased respiratory drive

• Respiratory muscle weakness

• Increased dead space

• Sedative medications

• Spinal cord injury

• Quadriplegia

• End-stage COPD

• Increased CO₂ production from conditions such as:

  • Fever

  • Sepsis

  • Burns

What ABG findings indicate hypercapnic respiratory failure?

• PaCO₂ >45 mmHg

• pH <7.35

• This indicates respiratory acidosis.

• Remember:

  • CO₂ ↑

  • Acid ↑

  • pH ↓

What ABG findings indicate hypoxemic respiratory failure?

• PaO₂ <60 mmHg

• PaCO₂ is usually normal or decreased.

• The primary problem is inadequate oxygen transfer.

• Severe untreated hypoxemia can lead to tissue hypoxia and cell injury.

What are signs and symptoms of hypoxemia?

• SpO₂ <90% on room air

• Irritability

• Confusion

• Tachypnea

• Tachycardia

• Dysrhythmias

• Cyanosis is a late sign

• Severity depends on how low the oxygen level is and how long it has been low.

What are signs and symptoms of hypercapnia?

• Headache

• Behavior changes

• Flushed skin

• Nausea/vomiting

• Asterixis

• Myoclonus

• Seizures

• Decreased LOC

• Severe cases can progress to coma/obtundation.

What manifestations can occur with both types of respiratory failure?

• Shortness of breath

• Tachypnea

• Increased work of breathing

• Changes in mental status

• Confusion

• Tachycardia

• The exact symptoms depend on the cause and severity of respiratory failure.

What is the priority when treating acute respiratory failure?

• Restore respiratory and hemodynamic stability.

• Perform frequent respiratory assessments.

• Improve oxygenation.

• Support ventilation when needed.

• Identify and treat the underlying cause.

What is the progression of oxygen support in ARF?

• Start with the least invasive method appropriate for the patient:

  1. Nasal cannula

  2. Face mask

  3. Non-rebreather

  4. CPAP/BiPAP

  5. Intubation + mechanical ventilation

• Goal is generally SpO₂ >90%.

What medications may be used to treat ARF?

• Albuterol: bronchodilator

• Ipratropium: bronchodilator

• Methylprednisolone/dexamethasone: decrease inflammation

• Furosemide: removes excess fluid

• Morphine: may help pain/air hunger

• Treatment also depends on the underlying cause.

What is the purpose of furosemide in respiratory failure?

• Furosemide is a diuretic.

• Promotes removal of excess fluid.

• Useful when hypervolemia/pulmonary edema contributes to impaired gas exchange.

• Removing excess fluid can improve oxygenation.

How do you know gas exchange is improving?

• PaO₂ increases

• PaCO₂ decreases when CO₂ retention is present

• SpO₂ improves

• Work of breathing decreases

• Respiratory status improves

• Mental status may improve as oxygenation improves.

What is ARDS?

• Severe inflammatory injury of the lungs.

• Capillaries become damaged and leak fluid into the alveoli.

• The lungs become stiff with decreased compliance.

• Oxygen cannot move easily into the blood.

• Severe cases can cause life-threatening hypoxemia.

What is the most common cause of ARDS?

• Sepsis is the most common cause listed in the PowerPoint.

• Other triggers can include:

  • Infection

  • Trauma

  • Severe inflammatory injury

• The inflammatory response damages the alveolar-capillary membrane.

When does ARDS usually develop?

• Usually develops within 3 days of the infection, trauma, or other insult.

• Nearly always develops within 7 days.

• Respiratory symptoms progressively worsen.

What are the signs and symptoms of ARDS?

• Progressive dyspnea

• Tachypnea

• Hypoxemia

• Cough

• Chest discomfort

• Anxiety/restlessness

• Tachycardia

• Hypotension

• Accessory muscle use

• Decreased lung compliance

• Pulmonary edema

• Cyanosis is a late finding.

What is refractory hypoxemia in ARDS?

• Severe hypoxemia that does not improve adequately despite high levels of oxygen.

• The patient may remain hypoxemic even when receiving 100% oxygen.

• This indicates severe impairment of gas exchange

What ABG findings are concerning in ARDS?

• SaO₂ <90%

• PaO₂ <60 mmHg

• pH <7.3

• These findings indicate significant oxygenation problems and possible acid-base disturbance.

What diagnostics are used for ARDS?

• ABG

• Chest X-ray

• CT scan

• CBC

• Electrolytes

• BUN/creatinine

• Blood and sputum cultures

• ECG to help exclude cardiac causes

• BUN/creatinine are important because AKI can progress to MODS.

What nursing interventions are important for ARDS?

• Monitor VS frequently

• Assess oxygenation

• Assess lung and heart sounds

• Monitor LOC

• Maintain oxygen therapy

• Suction as needed

• Monitor ETT placement if intubated

• Assess skin and perfusion

• Position appropriately

• Prone severe ARDS >12 hours/day when indicated.

Why is prone positioning used for severe ARDS?

• Decreases compression of the lungs.

• Improves ventilation.

• Improves gas exchange.

• Helps distribute ventilation to better-perfused areas of the lungs.

• Severe ARDS patients may be prone >12 hours/day.

What interventions decrease oxygen consumption in ARDS

• Provide adequate pain control.

• Give sedation/anxiolytics when indicated.

• Reduce anxiety and agitation.

• Mechanical ventilation decreases the patient's work of breathing.

• Prevent shivering and excessive activity when appropriate.

• Goal: reduce the body's oxygen demand.

What is CPAP?

• Provides one continuous pressure during inspiration and expiration.

• Helps prevent alveolar collapse.

• Improves oxygenation.

• Decreases work of breathing.

• Requires an intact respiratory drive and adequate tidal volume.

• Commonly used for sleep apnea.

What is BiPAP?

• Provides two pressure levels:

  • Higher inspiratory pressure

  • Lower expiratory pressure

• Helps provide ventilatory assistance.

• Especially useful for patients with hypercapnia.

• Example setting: 10/5 means IPAP 10 and EPAP 5.

What is the main difference between CPAP and BiPAP?

• CPAP: one continuous pressure, mainly supports oxygenation.

• BiPAP: two pressures, supports ventilation and oxygenation.

• BiPAP is useful when the patient needs help removing CO₂.

• CPAP is not appropriate for significant hypercapnia.

When is noninvasive ventilation contraindicated?

• Unable to protect the airway

• Altered mental status with aspiration risk

• Severe hemodynamic instability

• Facial trauma

• Unable to tolerate the mask

• Severe respiratory failure requiring invasive ventilation

• Very low pH may indicate need for intubation.

When should a patient be intubated?

• RR >30–35 or <8

• Severe accessory muscle use

• Paradoxical breathing

• Respiratory muscle exhaustion

• GCS <8 with respiratory failure

• Hemodynamic instability from hypoxia/hypercapnia

• Failure of noninvasive ventilation

• Unable to protect the airway

• Persistent abnormal ABGs

What ABGs may indicate need for intubation?

• Hypoxemic: PaO₂ <60 despite FiO₂ >0.60

• Hypercapnic: PaCO₂ >50 with pH <7.25

• Persistent abnormalities despite noninvasive support are concerning.

💉 Rapid Sequence Intubation - What is the correct medication order for RSI?

• 1. Fentanyl

  • Pain medication

• 2. Etomidate

  • Sedation/induction

• 3. Succinylcholine or rocuronium

  • Paralytic

• The patient should receive analgesia and sedation before paralysis.

Why must sedation be given before the paralytic?

• Paralytics cause muscle paralysis only.

• They do not provide pain relief or sedation.

• Giving a paralytic before adequate sedation could leave the patient unable to move or breathe while still aware.

• Therefore:
  Pain → Sedation → Paralysis.

What should the nurse monitor during RSI?

• SpO₂

• Blood pressure

• Heart rate and rhythm

• Oxygenation

• Airway status

• Medication sequence

• Have a BVM at the bedside.

• Monitor for hypoxemia, dysrhythmias, aspiration, and other complications.

Where is an endotracheal tube placed?

• Inserted through the mouth into the trachea.

• Provides a secure airway.

• Allows connection to mechanical ventilation.

• Used when the patient cannot maintain adequate ventilation or oxygenation independently.

How is ETT placement confirmed?

• End-tidal CO₂

• Bilateral breath sounds

• Physical assessment

• Chest X-ray confirms final tube position.

• The nurse should continuously monitor for displacement.

What is the purpose of the ETT cuff?

• Creates a seal inside the trachea.

• Prevents air from leaking around the tube.

• Helps ensure the ventilator's tidal volume reaches the lungs.

• Helps reduce aspiration of secretions around the tube.

Can a patient with an inflated ETT cuff eat, drink, or talk?

• No.

• The patient cannot normally talk with the ETT in place.

• Oral eating and drinking are not allowed.

• Nutrition is provided through tube feeding when appropriate.

What are the benefits of mechanical ventilation?

• Improves oxygenation.

• Improves CO₂ removal.

• Corrects respiratory acidosis.

• Decreases work of breathing.

• Allows respiratory muscles to rest.

• Provides a secure airway and helps prevent aspiration.

What is FiO₂?

• Fraction of inspired oxygen.

• Indicates the percentage of oxygen delivered by the ventilator.

• Room air = 21% oxygen.

• Ventilator settings can range from 21% to 100%.

What is PEEP?

• Positive end-expiratory pressure.

• Pressure remains in the lungs at the end of expiration.

• Helps keep alveoli open.

• Improves oxygenation and prevents alveolar collapse.

What is tidal volume?

• The amount of air delivered to the patient with each ventilator breath.

• Helps determine how much air enters the lungs with each breath.

What does the ventilator rate control?

• The minimum number of breaths delivered by the ventilator each minute.

• The patient may breathe above the set rate.

• Respiratory rate contributes to total minute ventilation.

Ventilator Modes - What is Assist-Control (A/C)?

• The ventilator provides a set minimum number of breaths.

• It assists each patient-initiated breath.

• If the patient does not breathe enough, the ventilator provides the set breaths.

• Provides substantial ventilatory support.

What is SIMV?

• Synchronized intermittent mandatory ventilation.

• Provides a set number of mandatory breaths.

• The patient can breathe spontaneously between mandatory breaths.

• Allows more patient participation in breathing.

What is pressure support ventilation?

• Supports spontaneous breaths initiated by the patient.

• A preset inspiratory pressure helps make each breath easier.

• Commonly used during weaning/extubation readiness trials.

• Patient must be able to initiate breaths.

Ventilator Alarms - What causes a low-pressure ventilator alarm?

• Usually indicates a leak or disconnection.

• Possible causes:

  • ETT displacement

  • Disconnected tubing

  • Leak in the ventilator circuit

• Assess the patient first and provide manual ventilation if needed.

What causes a high-pressure ventilator alarm?

• Indicates increased resistance to airflow.

• Possible causes:

  • Kinked tubing

  • Secretions

  • Mucus plug

  • Coughing

  • Pulmonary edema

  • Pneumothorax

• Always assess the patient first.

What complications can occur with mechanical ventilation?

• Barotrauma

• Pneumothorax

• Subcutaneous emphysema

• Fluid retention

• Hemodynamic compromise

• Oxygen toxicity

• Aspiration

• GI ulceration

• Ventilator-associated pneumonia

How can mechanical ventilation cause fluid retention?

• Positive pressure can decrease cardiac output.

• This can activate the RAAS, causing sodium and water retention.

• Monitor:

  • I&O

  • Daily weight

  • Breath sounds

  • Secretions

• Watch for worsening fluid overload.

What is oxygen toxicity?

• Lung injury caused by prolonged exposure to high oxygen concentrations.

• Risk increases with FiO₂ >50% for 24–48 hours.

• Monitor for:

  • Restlessness

  • Dyspnea

  • Tachypnea

  • Tachycardia

  • Crackles

  • Cyanosis

How does mechanical ventilation cause hemodynamic compromise?

• Increased intrathoracic pressure decreases venous return.

• Less venous return can decrease cardiac output.

• Monitor for:

  • Hypotension

  • Tachycardia

  • UO ≤30 mL/hr

  • Cool/clammy skin

  • Decreased pulses

  • Decreased LOC

How can the nurse reduce aspiration risk?

• Keep the HOB at least 30°.

• Monitor enteral feeding according to facility policy.

• Assess feeding tolerance.

• Monitor for signs of aspiration.

• Proper positioning helps reduce aspiration risk.

How is GI ulceration monitored/prevented?

• Monitor GI drainage.

• Check stool for occult blood.

• Medications may include:

  • Sucralfate

  • H2 blockers

  • PPIs for appropriate high-risk patients

What is ventilator-associated pneumonia (VAP)?

• Pneumonia associated with mechanical ventilation.

• The ETT bypasses the normal upper-airway defenses.

• Bacteria can enter directly into the lower respiratory tract.

• Airway colonization can occur within about 48 hours.

How can VAP be prevented?

• Strict hand hygiene

• Use gloves appropriately

• Maintain proper airway care

• Keep HOB elevated

• Follow infection-control practices.

• Prevent aspiration when possible.

• Acid-suppression therapy may be used for appropriate high-risk patients.

Weaning From the Ventilator - What indicates a patient may be ready for weaning?

What indicates a patient may be ready for weaning?

What is a spontaneous breathing trial (SBT)?

• A trial to determine whether the patient can breathe with less ventilator support.

• May use:

  • Pressure support

  • T-piece

• Helps determine readiness for extubation.

What findings indicate a patient is NOT ready for extubation?

• Tachycardia

• Tachypnea

• Respiratory distress

• Increased work of breathing

• Restlessness/anxiety

• Decreased LOC

• Worsening ABGs

• Inability to maintain adequate oxygenation

What findings support readiness for extubation?

• RR <35/min

• HR <140/min

• SpO₂ >90%

• SBP 90–180 mmHg

• No increased work of breathing

• Awake and alert

• Follows commands

• Adequate oxygenation and stable ABGs

What are the immediate nursing interventions after extubation?

• Place patient in semi-Fowler's/high-Fowler's.

• Apply humidified oxygen as ordered.

• Closely monitor respiratory status.

• Assess for fatigue and respiratory distress.

• Monitor oxygen saturation and vital signs.

• Obtain ABG as ordered, often within 1–2 hours.

What complications should be monitored after extubation?

• Respiratory fatigue

• Laryngospasm

• Stridor

• Airway obstruction

• Laryngeal edema

• Excessive secretions

• Respiratory failure

• Need for emergency reintubation

Why is the patient kept NPO after extubation?

• Extubation can cause swallowing problems.

• Patient needs a swallow assessment before eating/drinking.

• Helps prevent aspiration.

• Speech therapy may evaluate swallowing if needed.

What is the basic pathophysiology of cystic fibrosis?

• CF is caused by an abnormal protein involved in mucus and salt/water movement.

• Produces thick, sticky mucus.

• Thick mucus blocks airways.

• Leads to infection, scarring, and impaired gas exchange.

What are common respiratory manifestations of CF?

• Chronic cough

• Recurrent respiratory infections

• Wheezing

• Shortness of breath

• Declining FEV₁

• Thick secretions that are difficult to clear

• Progressive lung damage

What are advanced respiratory complications of CF?

• Pneumothorax

• Hemoptysis

• Severe lung damage

• Hypoxemic respiratory failure

  • PaO₂ <60

• Hypercapnic respiratory failure

  • PaCO₂ >50

• Possible need for lung transplant

What gastrointestinal/nutritional problems occur with CF?

• Thick mucus can block pancreatic ducts.

• Causes maldigestion and malabsorption.

• Can cause:

  • Low BMI

  • Poor growth

  • Steatorrhea

  • Fat-soluble vitamin deficiencies

• Vitamins A, D, E, K are especially affected.

How is cystic fibrosis diagnosed?

• Genetic testing

• Sweat chloride testing

• Nutritional assessment

• Chest X-ray

• Clinical findings

• Diagnosis is based on a combination of findings, not one test alone.

What sweat chloride result supports CF?

• Sweat chloride ≥60 mmol/L supports the diagnosis.

• CF causes increased sodium and chloride in sweat.

• The sweat test is interpreted along with other clinical/genetic findings.

What is the goal of CF treatment?

• There is currently no cure.

• Treatment focuses on:

  • Maintaining lung function

  • Clearing mucus

  • Preventing/treating infection

  • Maintaining nutrition

  • Preventing complications

What medications are used to treat CF?

• Bronchodilators → open airways

• Mucolytics → thin mucus

• Inhaled corticosteroids → decrease inflammation

• Antibiotics → treat/prevent infection

• CFTR modulators → target the abnormal CFTR protein

• Pancreatic enzymes → improve digestion

What is the correct order of CF airway treatments?

• 1. Bronchodilator

  • Opens the airways.

• 2. Mucolytic

  • Thins mucus.

• 3. Airway clearance

  • Removes mucus.

• 4. Inhaled corticosteroid

  • Decreases inflammation.

Why is the bronchodilator given first in CF?

• Example: albuterol

• Opens the airways.

• This allows the medications given afterward to reach deeper into the lungs.

• It also makes airway clearance easier.

What are mucolytics and why are they given?

• Mucolytics thin and loosen thick mucus.

• Examples:

  • Dornase alfa

  • Hypertonic saline

• Given after the bronchodilator.

• Makes secretions easier to remove.

What is airway clearance therapy in CF?

• Helps physically remove loosened mucus from the lungs.

• Examples:

  • Chest physiotherapy

  • HFCWO vest

  • Flutter/Acapella

  • PEP

  • Postural drainage

  • Coughing

How often should airway clearance therapy be performed?

• Usually 2–4 times per day.

• It should be performed consistently to prevent mucus buildup.

• Avoid performing airway clearance right before or after meals to reduce nausea/vomiting.

Why are inhaled corticosteroids used in CF?

• Example: budesonide

• Decreases airway inflammation.

• Given after airway clearance in the treatment sequence listed in the PowerPoint.

What nutrition is recommended for a patient with CF?

• High-calorie diet

• High-protein diet

• Supports increased energy needs.

• Helps maintain growth and body weight.

• Pancreatic enzymes are used when pancreatic insufficiency is present.

When should pancreatic enzymes be taken?

• Take pancrelipase with meals and snacks.

• The PowerPoint specifies within 30 minutes of meals/snacks.

• Helps digest and absorb nutrients.

• Especially important when pancreatic ducts are blocked by thick mucus.

Which vitamins should CF patients receive?

• Fat-soluble vitamins:

  • Vitamin A

  • Vitamin D

  • Vitamin E

  • Vitamin K

• These may be poorly absorbed because of pancreatic insufficiency.

What CF patient education is important?

• Teach airway-clearance techniques.

• Teach proper medication/breathing-treatment use.

• Encourage immunizations.

• Encourage high-protein/high-calorie nutrition.

• Take pancreatic enzymes with meals/snacks.

• Take vitamins A, D, E, K.

• Maintain hydration and adequate salt during hot weather.

• Genetic counseling/testing may be discussed when planning pregnancy.

What are the key ARF numbers to remember?

• Hypoxemic: PaO₂ <60

• Hypercapnic: PaCO₂ >45

• Hypercapnic respiratory acidosis: pH <7.35

• SpO₂ concerning for hypoxemia: <90%

What is the easiest way to remember hypoxemic vs hypercapnic?

• Hypoxemic = LOW O₂

  • Problem getting oxygen into blood.

• Hypercapnic = HIGH CO₂

  • Problem removing CO₂.

• Hypoxemic = oxygenation problem

• Hypercapnic = ventilation problem

What is the easiest way to remember CPAP vs BiPAP?

• CPAP = 1 pressure

  • Mainly oxygenation.

• BiPAP = 2 pressures

  • Helps ventilation and oxygenation.

• Think: BiPAP helps blow off CO₂.

What is the RSI sequence to memorize?

• Fentanyl → Etomidate → Paralytic

• Pain → Sedation → Paralysis

• Paralytic does NOT provide sedation or pain relief.

• Never paralyze before adequate sedation.

What is the CF treatment sequence to memorize?

• 1. Albuterol → open

• 2. Mucolytic → thin

• 3. Airway clearance → remove

• 4. Steroid → decrease inflammation

What are the major ventilator alarm differences?

• Low pressure = leak/disconnection

  • Displaced ETT

  • Disconnected tubing

• High pressure = obstruction/resistance

  • Kink

  • Secretions

  • Mucus plug

  • Coughing

  • Pulmonary edema

  • Pneumothorax

What are the major signs of respiratory failure?

• Early:

  • Restlessness

  • Anxiety

  • Tachypnea

  • Tachycardia

  • Changes in mental status

• Late/severe:

  • Cyanosis

  • Severe hypoxemia

  • Decreased LOC

  • Respiratory exhaustion

  • Possible respiratory arrest

What are the most concerning signs of worsening respiratory failure?

• Worsening hypoxemia despite oxygen

• Increasing work of breathing

• Severe tachypnea or respiratory fatigue

• Decreasing LOC

• Cyanosis

• Worsening ABGs

• Failure of CPAP/BiPAP

• Hemodynamic instability

What is the overall escalation from respiratory support to ventilation?

• Oxygen → CPAP/BiPAP → Intubation → Mechanical ventilation

• Escalate when the patient cannot maintain adequate oxygenation/ventilation.

• Persistent abnormal ABGs, respiratory distress, altered LOC, or NIV failure can indicate need for intubation.