ABGs Interpretation: Acid-Base Balance Explained

• ABGs provide essential information about a patient's acid-base balance and oxygenation status, including pH, PaCO2, HCO3, PaO2, and SaO2.
• The normal ranges for ABG values are: pH (7.35-7.45), PaO2 (80-100 mmHg), PaCO2 (35-45 mmHg), HCO3 (22-26 mEq/L), and SaO2 (above 95%).
• Respiratory acidosis occurs with excess CO2 retention, leading to decreased blood pH, often due to hypoventilation (e.g., COPD, asthma).
• Respiratory alkalosis occurs with excessive CO2 removal, leading to increased blood pH, often due to hyperventilation (e.g., asthma attack, sepsis).
• Metabolic acidosis involves an excess of acid or loss of bicarbonate, decreasing blood pH, often caused by increased acid production or bicarbonate loss (e.g., diarrhea).
• Metabolic alkalosis involves an increase in blood pH and bicarbonate levels, often due to overuse of antacids, loss of hydrogen ions (e.g., vomiting), or hypokalemia.

Compensation

• The lungs and kidneys work to compensate for acid-base imbalances; respiratory compensation occurs within minutes, while renal compensation takes hours to days.
• In metabolic acidosis, the respiratory rate increases (hyperventilation) to expel CO2 and raise pH, while in metabolic alkalosis, the respiratory rate decreases (hypoventilation) to retain CO2 and lower pH.
• In respiratory acidosis, the kidneys retain bicarbonate and excrete more H+ to raise pH, while in respiratory alkalosis, the kidneys excrete bicarbonate and retain H+ to lower pH.
• Complete compensation occurs when the pH returns to normal (7.35-7.45), despite abnormal HCO3 and PaCO2 levels.
• Partial compensation occurs when the pH is still outside the normal range, but there are changes in both HCO3 and PaCO2 in the direction needed to correct the pH.

Emergency Respiratory Care

• Rapid assessment of acute upper airway obstruction includes inspection, palpation, and auscultation without blind sweeping.
• Endotracheal (ET) tubes offer a patent airway, access for mechanical ventilation, and aids in secretion removal; they should be used for no longer than two weeks to avoid tracheal damage.
• Intubation tube size typically ranges from 6.5 to 7.5, with proper placement confirmed via CXR, auscultation, and ETCO2 monitoring.
• Ventilation-acquired pneumonia involves mobility and is treated by only suctioning when the patient is overly secreted; and/or abnormal breath sounds.
• CXRs are done daily in ICU patients to monitor for atelectasis or ARDS (acute respiratory distress syndrome).
• Mechanical ventilation involves either positive or negative pressure to maintain the patient's respirations.
• Positive pressure ventilation pushes air into the lungs, while negative pressure ventilation mimics normal breathing.
• PEEP, a setting on ventilators, maintains pressure in the lungs after expiration, to prevents alveolar collapse, facilitates gas exchange. Usually about five. When it is low, or if the patient has an illness where they don't make enough, surfactant is impacted.
• Assess respiratory and neurological status, coping, comfort, and communication ability.
• Prevent ventilator-associated pneumonia (VAP) by elevating HOB to 30-45 degrees, performing daily sedation vacations, and providing daily oral care with chlorhexidine

Common Vent Settings include the following

• Vt, or volume, ranges from 6-10ml/kg; PEEP ranges from 5-20; Rate is 10-25
• Low-pressure alarms indicate leaks, while high-pressure alarms indicate airflow obstruction.
• AC (assisted/control) mode provides preset tidal volume and rate, supporting the patient.
• SIMV (synchronized intermittent mandatory ventilation) delivers set breaths synchronized with patient efforts for comfort.
• APRV (airway pressure release ventilation) keeps lungs open longer and improves gas exchange with lungs that have extreme injuries.

Additional Facts Around Respiratory Failure

• CPAP gives positive pressure for sleep apnea, while BiPAP helps with inspiration/expiration and signals desaturation.
• Weaning involves reducing ventilator support in stages, guided by patient stability and blood gas analysis.
• Nursing interventions include gas exchange, airway clearance, trauma prevention, mobility, communication, and coping support.
• Lung sounds should be auscultated every 2-4 hours.
• Vent problems can stem from tube issues, patient-ventilator asynchrony, or changes in respiratory mechanics.
• Thoracic surgery addresses a lung collapse by relieving lung abscesses, tumors, cysts, or emphysema.
• Monitor respiratory and cardiovascular function, enhance gas exchange, promote airway clearance, manage pain with the patient during recovery from thoracic surgery procedures.
• Chest tubes are important for removing air, blood, or fluid.
• Wet chest tubes have three chambers for: fluid collection, water seal, and the third wet suction control chamber.
• Dry chest tubes have no water column; upper left knob controls pressure.
• Management of lung conditions involves early mobilization, frequent turning, frequent secretion management.
• Pneumonia causes the lungs to fill with varying forms of fluid, and impair alveoli functions from expanding, and reducing air-flow capabilities. Some forms of pneumonia may include the patient spitting up blood, while others can lead to bradycardia.
• Assess with increased WBC counts, CXR, and sputum cultures.
• Medical management involves appropriate medication (antibiotics, antivirals, antifungals).
• Complications include sepsis, respiratory and/or kidney failure, delirium, and other diseases afflicting the pleural lining of the lungs.
• Pleurisy refers to disorders affecting the visceral or parietal pleura.
• Pleural effusion involves fluid that can cause tracheal deviations away from the affected side, or cause deep painful breaths. Treat using thoracentesis.
• Empyema involves a thick build-up of pus in the pleural space, most likely leading to severe medical conditions. Treat with fluid drainage and appropriate antibiotics.
• ARDS can appear for a myriad of reasons, and severely damages the alveolor sacs, and can sometimes cause a sudden case pf "flash" lung edema. Some inflammation can also cause build up of fluids, leading to further damage. Common symptoms include rapid shallow breathing, shortness of breathe, or feeling of a general suffocation.
• Medical management requires some form of ventilation (CPAP/BIPAP) to keep airways opened.
• Flail segments involve 2+ adjacent broken ribs, and may cause the puncture of a lung(s).

O2 Delivery

• Various O2 delivery options are available for low to hi-flow depending on current status.
• 1-6L via nasal cannulas
• Face masks deliver up to 5-10L
• Nonrebreathers provide 6-15L, or ~80%-90%
• Other ventilation treatments can provide anywhere from 25-100% of O2 flow depending on the severity.

Neuromuscular Junction Blocking Agents

• NMBAs are used to eliminate voluntary and involuntary muscle movement by interrupting communication at the neuromuscular junction.

Types:

• Depolarizing agents (e.g., succinylcholine)
• Nondepolarizing agents (e.g., atracurium, cisatracurium, pancuronium, rocuronium, vecuronium).

Adverse Reactions and Considerations:

• Adverse effects may include bronchospasm in situations where there is difficulty getting the endotracheal tubes in or out of the mouth, and there may be a drug-drug interaction when used with channel blockers.

Understand ABGs with normal ranges for pH, PaO2, PaCO2, HCO3 and SaO2. Learn how respiratory and metabolic acidosis/alkalosis affect blood pH. Discover the compensatory roles of the lungs and kidneys.