Alterations in Oxygenation and Ventilation: Respiratory

Lung Function

• Gas exchange

• Temperature and humidity

• Protection

Gas Exchange

• The lungs perform gas exchange, which is the process of moving oxygen into the body and removing carbon dioxide. 

Temp and Humidity

• The lungs warm and humidify air to match body temperature and humidity levels. 

Protection

• The lungs protect the body from harmful substances by coughing, sneezing, swallowing, and filtering them. 

Acute Respiratory Failure (ARF)

• Occurs when oxygenation, ventilation, or both are inadequate 

ARF: Insufficient O2 transferred to blood

• Hypoxemia

  • Oxygenation failure 

  • PAo2 < or = 60 mm Hg on > or = 60% oxygen 

• Decreased PaO2 and SaO2

ARF: Inadequate CO2 removal

• Hypercapnia

• Increased PaCO2 (>50 mm Hg and pH <7.35)

ARF: ABG

• ABGs assess pH, PaO2, PaCO2, bicarbonate, SaO2

• Pulse oximetry assesses arterial O2 saturation (SpO2)

ARF: Oxygenation Failure four physiologic mechanisms

• V/Q mismatch: Mismatch between ventilation (V) and perfusion (Q)

• Shunt: Blood leaves the heart without gas exchange

• Diffusion Impairment: destroys the alveolar membrane or affects blood flow through the pulmonary capillaries 

• Alveolar hypoventilation: Decreased ventilation leading to increased PaCO2

V/Q mismatch:

• Normal alveolar ventilation (V) = 4 to 6L/min

• Pulmonary blood flow (Q) = 4 to 6 L/min

• VQ ratio = 0.8 to 1.2

• Ideally, V/Q ratio 1:1 or V/Q equals 1 

**Body can tolerate

increased CO2 levels better than decreased O2 levels

ARF Clinical Manifestations

• Rapid, shallow breathing, tachypnea 

• Tripod position/Orthopnea

• Dyspnea

• Speak in short jerky sentences

• Pursed-lip breathing

• Intercostal muscle retraction

• Tachycardia

• Restless/Agitated

• Prolonged expiration

• Fatigue

• Pallor

• Nasal flaring

ARF Clinical Manifestations: Changes in mental status

• Decreased O2: restlessness, confusion, agitation

• Increased CO2: morning headache, decreased RR, and decreased LOC

ARF Clinical Manifestations: Changes in breath sounds

• Crackles or rhonchi

• Diminished breath sounds

• Pleural friction rub

ARF Diagnostic Studies

• *Know vital sign norms

• Most common

• Chest x-ray 

• ABG analysis/pulse oximetry

• CT scan or V/Q scan

• End tidal CO2  ( with mechanical ventilation)

ARF Collaborative Care: Goal

• Goal: Optimize gas exchange

ARF Collaborative Care: mild to moderate

• High-flow O2 (if no other co-morbidities)

• Non-invasive ventilation (Bi-PAP) for patients who are awake, alert, able to maintain a patent airway, able to clear own secretions

ARF Collaborative Care: severe ARF

• ICU care

• Mechanical ventilation

• Continuous pulse oximetry

• Arterial blood pressure (ABP) monitoring: A line

• Frequent ABGs

• Central venous pressure (CVP) monitoring: measures the pressure in the superior vena cava or right atrium of the heart. Norm = 8 to 12 mmHg

• Advanced hemodynamic monitoring

ARF Collaborative Care

• Liquefy secretions: humidification, encourage fluid intake

• Mobilization of Secretions: coughing (huff, staged), positioning, chest physiotherapy (percussion, vibration, postural drainage), suctioning

ARF positioning

• HOB should be raised to at least 30 degrees; reclining chair or chair bed 

ARF Collaborative Care: PPV

• Positive Pressure Ventilation (PPV)

  • Noninvasive positive pressure ventilation (NIPPV) 

    • Provides O2 and decreases WOB with spontaneous breathing; must be awake, alert, and VS stable

    • Contraindicated for decreased LOC, high O2 requirements, facial trauma, hemodynamic instability, or excess secretions

ARF Collaborative Care: PPV two forms

• CPAP—continuous positive airway pressure. Constant pressure during inspiration and expiration

• BiPAP—bilevel positive airway pressure (more common). Uses 2 different levels of positive pressure – one with inspiration; another with expiration

ARF Collaborative Care: Noninvasive Ventilation

• BiPAP delivers two distinct air pressure levels, one for inhaling and one for exhaling, while CPAP provides a constant, single level of air pressure throughout the breathing cycle

ARF Collaborative Care: Medications

• Short-acting bronchodilators repeated every 15-30 minutes until a response is achieved using hand-held nebulizer or metered-dose inhaler with a spacer

• Corticosteroids help with inflammation 

• Treat infections: Antibiotics

ARF Collaborative Care: Medications to decrease pulmonary congestion caused by HF

• IV diuretics

• Morphine

• Nitroglycerine

ARF Collaborative Care: Medications for anxiety

• Reduce anxiety, pain, and restlessness from hypoxemia, hypercapnia, equipment discomfort: Benzodiazepines and Opioids – use lowest dose possible

Concerns with Oxygen Therapy

• High FiO2 for prolonged periods can lead to adverse effects

Oxygen toxicity

(greater than 60% O2 for longer than 48 hours); inflammation and cell death by disrupting the alveolar-capillary membrane

Patients with chronic hypercapnia (COPD):

Provide O2 at low flow (nasal cannula at 1 to 2 L/min or Venturi mask at 24% to 28%)

Goals

• Independently maintain a patent airway

• Have optimal gas exchange 

• Absence of dyspnea or recovery to baseline breathing patterns

• Effectively cough and able to clear secretions

• Normal ABG values or values within patient's baseline

• Breath sounds within patient's baseline

Acute Respiratory Distress Syndrome (ARDS)

• Sudden progressive form of acute respiratory failure. Begins 24 to 72 hours after initial lung injury (direct or indirect). Lasts 7 – 10 days 

• Lungs become stiff and reduces the ability to expand, leading to low oxygen levels in the blood

• Alveolar collapse where the blood passes thru capillary bed of the lungs without picking up O2

Acute Respiratory Distress Syndrome (ARDS) common causes

• Sepsis

• Multiple organ dysfunction syndrome (MODS). 

ARDS Clinical Manifestations

• *Classic sign of ARDS…Hypoxemia from VQ mismatch and is unresponsive to increased amounts of O2 therapy

• Profound respiratory distress

• Fine, scattered Crackles

• Restlessness, Anxiety, Change in Mental Status

• Dyspnea

• Tachycardia

• Cyanosis, Pallor

• Intercostal retractions

• Hypotension

• Diaphoresis

• Hypoventilation causing severe gas exchange alterations and imminent respiratory failure

ARDS Diagnostics

• Chest x-ray (after 72 hours) showing diffuse and extensive bilateral interstitial and alveolar infiltrates with pulmonary edema (white areas = fluid) 

• ABGs: Hypoxemia (decreased Pao2), Hypercapnia from respiratory muscle fatigue (Increased PaCO2), metabolic acidosis

ARDS Complications main cause of death

• Main cause of death: MODS, accompanied by sepsis; vital organs affected: lungs, kidneys, liver, and heart

ARDS Complications

• Infection: catheter-related 

• Respiratory: O2 toxicity, barotrauma (Rupture of overdistended alveoli during mechanical ventilation; high peak pressures), PE, pulmonary fibrosis, ventilator-associated pneumonia

• Renal: acute kidney injury

• Venous Thromboembolism (VTE)

ARDS Collaborative Care

• Secretions: Effective coughing & positioning, Hydration, Humidification, Airway Suctioning, RotoProne bed

• Chest Physical Therapy: Percussion, Vibration, Postural Drainage

• Prone positioning

• Extracorporeal membrane oxygenation (ECMO)

ARDS Collaborative Care…Medications

• Bronchodilators (albuterol)

• Corticosteroids (methylprednisolone)

• Inotropic-creates forceful contractions (dopamine, dobutamine, digoxin)

• Vasopressors (epinephrine, vasopressin)

• Loop Diuretics (furosemide)

• Narcotics (fentanyl, hydromorphone) & sedation (propofol)

ARDS Collaborative Care…Medications neuromuscular blocking agents

• (paralyzing-High Alert Medications). Used to decrease WOB and create more effective synchrony with vent to improve O2 and ventilation (succinylcholine, vecuronium). Given by Certified Registered Nurse Anesthetists, Anesthesiologists, NPs, MDs.

When does a patient need an endotracheal tube and mechanical ventilation?

• Difficulty/Inability to breathe

• Supportive breathing: patients with conditions like pneumonia, emphysema, heart failure, or a collapsed lung who cannot take in enough oxygen

• Surgery

• Reduced level of consciousness

• Trauma

• Airway protection

• Pulse oximetry in 80s and dropping

• After intubation, priority is to auscultate bilateral lungs for breath sounds

ARDS Collaborative Care Best Practice (ARDSNet protocol)

• O2 administration

• Mechanical ventilation and endotracheal tube

• Low tidal volume and pressure ventilation

• Permissive hypercapnia

• Positive end expiratory pressure (PEEP)

ARDS Mechanical Ventilation

Mechanical Ventilation

• Pressure-control type of ventilation

• Low tidal volume 4 to 6 mL/kg (norm = 6-8 mL/kg)

  • Is the volume of air in and out of lungs

• Permissive hypercapnia

• Positive end expiratory pressure (PEEP)

  • Helps to open up collapsed alveoli to improve O2 exchange

Pressure-control type of ventilation

• Ventilator provides patient with pressure controlled breaths

• Reducing pressure going into stiff, noncompliant lungs helps to prevent further lung injury

Permissive hypercapnia

• Low tidal volumes leads to slow increase in PaCO2

• PaCO2 up to 60 mmHg is acceptable in early phase ARDS

• Requires frequent ABGs; keep pH 7.30 to 7.45

• Patient usually has continuous IV analgesia and sedation

Mechanical Ventilation…Settings

• Mechanical ventilation settings include the rate of breaths, the amount of air exchanged with each breath, the oxygen concentration, and the pressure in the lungs.            

• Respiratory rate: The normal rate is 10–16 breaths per minute        

Mechanical Ventilation…Settings: Tidal Volume (VT)

• The amount of air exchanged with each breath, measured in milliliters per breath. Norm usually 4-8 mL/kg. The tidal volume depends on the patient's lung condition 

Mechanical Ventilation…Settings: Oxygen concentration (FIO2)

• The fraction of inspired oxygen (FIO2) is usually set at 100%. The FIO2 is then decreased to the lowest level that still provides adequate oxygenation

Mechanical Ventilator…Alarms

• Low pressure:

  • Check connections-something loose

• High pressure:

  • Check for kinks in tubing

  • Listen to lungs-may need suction to remove secretions that are creating the high pressure

• When in doubt:

  • Remove patient from ventilator and use ambu bag until problem is found and corrected

Mechanical Ventilator…Weaning

• Begins with intubation and continues until patient is breathing independently

  • Alert, oriented, well-rested, pain-free, non-anxious patient

  • Patient who is informed about the process and able to cooperate

  • Lungs should be reasonably clear on auscultation and CXR

  • Patient needs to be able to breathe spontaneously. Respiration rate higher than ventilator setting (ie. Vent set at 12, Pt RR 16)

  • Acceptable ABGs (within normal limits) and SpO2 (at least 92%) while remaining hemodynamically stable

  • Hemoglobin >/= 7 g/dL

Mechanical Ventilator…Extubation

• Assess muscle strength and endurance 

• Minimal secretions; patient ability to cough, gag

• Set up alternative O2 delivery device

• Hyperoxygenate and suction patient

• Loosen ET commercial holder

• Have patient take a deep breath and in one smooth motion at the peak of inspiration, deflate the ET cuff and slowly remove the tube

Mechanical Ventilator… After Extubation

• Encourage patient to deep breathe and cough

• Suction oropharynx as needed

• Assess patient’s ability to speak

• Provide supplemental O2 and oral care

• Monitor VS, respiratory status, oxygenation for 2-3 hours

Mechanical Ventilator…Extubation Complications

• Signs the patient is not tolerating extubation

  • Decreased SpO2 levels

  • Tachypnea or bradypnea

  • Tachycardia

  • Decreased level of consciousness

  • Decrease in PaO2 (lower than 60 mmHg ) 

  • Increase in PaCO2

• Prepare to reintubate or for a trial of noninvasive ventilation

A patient’s ABG results include pH 7.31, PaCo2 50 mm Hg, PaO2 51 mm Hg, and HCO3 24 mEq/L. Oxygen is applied at 2 L/min, and the patient is placed in high-Fowler’s position. An hour later, the ABGs are repeated with results of pH 7.36, PaCo2 40 mm Hg, PaO2 60 mm Hg, and HCO3 24 mEq/L. What is most important for the nurse to do?

A. Increase the oxygen flow rate to 4 L/min.

B. Document the findings in the patient’s record.

C. Reposition the patient in a semi-Fowler’s position. 

D. Prepare the patient for endotracheal intubation and mechanical ventilation.

When assessing a patient with sepsis, which finding would alert the nurse to the onset of acute respiratory distress syndrome (ARDS)?

A. SpO2 of 80% 

B. Use of accessory muscles of respiration

C. Fine, scattered crackles on auscultation of the chest

D. ABGs of pH 7.33, PaCo2 48 mm Hg, and PaO2 80 mm Hg 

A patient with severe chronic lung disease is hospitalized with respiratory distress. Which finding would suggest to the nurse that the patient has developed rapid decompensation?

A. An SpO2 of 86%

B. A blood pH of 7.33

C. New onset of agitation or confusion

D. PaCO2 increases from 48 to 50 mm Hg