[03.21] CMD - Acute and Chronic Respiratory Failure V2.1.pdf

Oxygenation of blood and elimination of carbon dioxide

What are the two primary gas-exchanging functions of the respiratory system?

A syndrome

Is respiratory failure classified as a specific disease or a syndrome?

Gas exchange failure and chronicity

What are the two main axes of classification for respiratory failure?

Hypoxemic and hypercapnic

What are the two types of respiratory failure based on gas exchange failure?

Acute and chronic

What are the two types of respiratory failure based on chronicity?

PaO2 less than sixty mmHg

What is the partial pressure of oxygen threshold that defines hypoxemic respiratory failure?

Alveolar pathology

Hypoxemic respiratory failure typically results from what type of anatomical pathology?

PaCO2 greater than forty-five mmHg

What is the partial pressure of carbon dioxide threshold that defines hypercapnic respiratory failure?

Respiratory pump pathology

Hypercapnic respiratory failure typically results from what type of pathology?

Minutes to hours

Within what timeframe does acute respiratory failure typically develop?

Life-threatening derangements

What is the immediate consequence of the rapid development of acute respiratory failure?

Days or longer

Over what timeframe does chronic respiratory failure typically develop?

Indolent

What adjective is used to describe the typically slow, asymptomatic onset of chronic respiratory failure?

Clubbing, polycythemia, and cor pulmonale

What are three classic physical or hematological markers of chronic hypoxemic respiratory failure?

Elevated bicarbonate levels

What key chemical marker on arterial blood gas analysis indicates chronic hypercapnic respiratory failure?

Renal compensation

What physiological mechanism is responsible for the elevated bicarbonate levels in chronic hypercapnia?

Four

Into how many distinct types can acute respiratory failure be classified based on pathophysiologic derangements?

Type I

Which type of acute respiratory failure is defined as acute hypoxemic respiratory failure?

Type II

Which type of acute respiratory failure is defined as acute hypercapnic respiratory failure?

Type III

Which type of acute respiratory failure is defined as acute lung atelectasis?

Type IV

Which type of acute respiratory failure is defined as respiratory failure occurring in the setting of shock?

Low PaO2

What is the primary gas exchange characteristic of Type I respiratory failure?

Alveolar flooding

What pathological alveolar state leads to the development of intrapulmonary shunt physiology in Type I respiratory failure?

Intrapulmonary shunt physiology

What specific physiology is developed when alveolar flooding occurs in Type I respiratory failure?

Desaturation and low PaO2 on ABG

What are the two typical clinical presentations on monitoring and laboratory work-up for Type I respiratory failure?

Treat the underlying cause

What is the primary, most critical treatment step for Type I respiratory failure?

High flow nasal cannula, non-invasive positive pressure ventilation, and endotracheal intubation

What are the three positive airway pressure or oxygen devices used to support oxygenation in Type I respiratory failure?

Oxygen therapy

What standard therapeutic intervention is effective for most causes of hypoxemia except for true shunts?

Shunts

Which cause of hypoxemia is notoriously resistant to simple increases in oxygen therapy?

Altitude with reduced PiO2

What cause of hypoxemia is characterized by a rapid increase in PaO2 with oxygen therapy, as seen in high elevation?

Alveolar hypoventilation

Which cause of hypoxemia, seen in COPD or obesity hypoventilation, responds to oxygen but may depress minute ventilation?

Diffusion defect

Which cause of hypoxemia, seen in interstitial pneumonitis, shows a moderately rapid increase in PaO2 with oxygen?

Ventilation-perfusion mismatch

Which cause of hypoxemia, seen in pulmonary embolism, COPD, and ARDS, shows a moderately rapid increase in PaO2 with oxygen?

Atelectasis and ASD with right-to-left shunting

What are two clinical examples of shunts that show variable or poor response to oxygen therapy?

Inadequate tissue oxygenation or tissue hypoxia

What is the major threat of arterial hypoxemia to the human body?

DO2 equals CO multiplied by CaO2

What is the physiological equation for oxygen delivery, using common abbreviations?

Preload, afterload, and contractility

What three factors determine cardiac output in the oxygen delivery equation?

Hemoglobin level, PaO2, and oxygen saturation of hemoglobin

What three factors determine the oxygen content of arterial blood, CaO2?

Anaerobic metabolism

Into what metabolic pathway do cells enter when tissue hypoxia is prolonged?

Lactate

The build-up of what compound in the blood during anaerobic metabolism leads to metabolic acidosis?

Metabolic acidosis

What systemic acid-base abnormality results from prolonged tissue hypoxia and anaerobic metabolism?

PaCO2 greater than forty-five mmHg with pH less than seven point thirty

What specific PaCO2 and pH parameters define Type II respiratory failure?

Acidemia

What acid-base state, specifically defined by pH less than 7.30, accompanies Type II respiratory failure?

Alveolar hypoventilation

Type II respiratory failure is a direct consequence of what ventilatory state?

Inability to eliminate CO2

What metabolic elimination failure characterizes Type II respiratory failure?

NIPPV with a tight-fitting facial or nasal mask

What is the first-line non-invasive ventilatory treatment of choice for Type II respiratory failure?

Endotracheal intubation

What is the next step in ventilatory support if NIPPV fails in a Type II respiratory failure patient?

CNS pathology, neuromuscular dysfunction, and increased load

What are the three broad categories of mechanisms leading to alveolar hypoventilation?

Drug overdose and brainstem injury

What are two clinical examples of CNS pathology that decrease ventilation?

C3 to C5 vertebrae

Nerves innervating the muscles of respiration originate from which cervical vertebrae?

Sleep-disordered breathing

What category of breathing disorders, including obesity hypoventilation syndrome, causes hypoventilation?

Severe hypothyroidism

What systemic endocrine pathology is listed as a potential CNS-associated cause of alveolar hypoventilation?

Myasthenia Gravis, Guillain-Barre Syndrome, and Amyotrophic Lateral Sclerosis

What are three clinical examples of neuromuscular dysfunction causing impaired transmission?

Myositis, myopathy, electrolyte derangements, and fatigue

What are four causes of respiratory muscle weakness that lead to hypercapnic failure?

Resistive loads, reduced lung compliance, reduced chest wall compliance, and increased minute ventilation requirements

What are the four categories of increased loads on the chest wall and airways?

Bronchospasm and obstructive airway diseases

What are two clinical examples of resistive loads that increase airway resistance?

COPD and asthma

What are two specific obstructive airway diseases that act as resistive loads?

Alveolar edema and atelectasis

What are two clinical examples of reduced lung compliance?

Pneumothorax, pleural effusion, abdominal distention, and abdominal compartment syndrome

What are four clinical examples of reduced chest wall compliance?

Pulmonary embolus

What is a clinical example of an increased minute ventilation requirement that increases work load?

Lung atelectasis

Type III respiratory failure is primarily caused by what mechanical lung pathology?

Post-operative period

During what specific surgical period does Type III respiratory failure uniquely occur?

Perioperative respiratory failure

What is another clinical term used to refer to Type III respiratory failure?

General anesthesia

What standard surgical induction process causes a decrease in functional residual capacity, leading to Type III failure?

Decrease in Functional Residual Capacity

What physiological lung volume change under general anesthesia leads to the collapse of dependent lung units?

Collapse of dependent lung units

What structural change in the alveoli occurs because of decreased FRC during general anesthesia?

Recruit or re-expand the atelectatic lung segments

What is the primary therapeutic goal when treating Type III respiratory failure?

Frequent changes in position, chest physiotherapy, upright positioning, incentive spirometry, and pain control

What five mechanical and physical interventions are used to recruit atelectatic lungs?

Incisional and abdominal pain

Control of what specific pain is emphasized to help the patient perform breathing exercises?

NIPPV

What intervention is indicated for Type III respiratory failure patients who do not easily respond to position changes and spirometry?

Hypoperfusion of respiratory muscles

Type IV respiratory failure is caused by what perfusion abnormality?

Patients in shock

In what group of hemodynamically unstable patients does Type IV respiratory failure occur?

Less than five percent

Normally, the respiratory muscles consume what percentage of total cardiac output?

Up to forty percent

In a state of shock, the overworked respiratory muscles can consume what percentage of cardiac output?

Anaerobic metabolism

Into what metabolic pathway do respiratory muscles go when their high oxygen demand is unmet in shock?

They do not necessarily have a lung pathology

Why is Type IV respiratory failure unique regarding lung parenchymal pathology?

Endotracheal intubation

What is the definitive treatment for Type IV respiratory failure to allow the respiratory muscles to rest?

Allow respiratory muscles to rest and redistribute cardiac output back to vital organs

What are the two physiological goals of endotracheal intubation in Type IV respiratory failure?

Nasal cannula

What is the most basic low-flow oxygen delivery device?

Twenty-one to forty-five percent

What is the fraction of inspired oxygen range delivered by a standard nasal cannula?

Zero point five to six liters per minute

What is the oxygen flow rate range in lpm for a nasal cannula?

Variable system

Is a standard nasal cannula classified as a fixed or variable oxygen delivery system?

Oxygen is mixed with ambient air

Why is a nasal cannula classified as a variable system?

Reservoir systems

To what general category of oxygen delivery systems do simple face masks, partial rebreather masks, and nonrebreather masks belong?

Simple face mask

Which low-flow reservoir device delivers an FiO2 of thirty-five to fifty percent at a flow of five to twelve lpm?

Partial rebreather mask

Which low-flow reservoir device delivers an FiO2 of thirty-five to sixty percent at a flow of six to ten lpm?

Nonrebreathing mask

Which low-flow reservoir device delivers an FiO2 of fifty-five to seventy percent at a flow of six to ten lpm?

Venturi mask

Which high-flow oxygen delivery device delivers a highly predictable FiO2 of twenty-four to sixty percent at a flow of twelve to fifteen lpm?

Predictable FiO2

What is the major clinical advantage of a Venturi mask over standard low-flow devices?

High flow nasal oxygen

What does the abbreviation HFNO stand for in respiratory support?

Almost one hundred percent

What maximum fraction of inspired oxygen can be delivered by a high flow nasal oxygen system?

Sixty liters per minute

What is the maximum flow rate in lpm delivered by an HFNO system?

Fixed system

Is high flow nasal oxygen classified as a fixed or variable system?

Nasal cannula, face mask, Venturi face mask, and face mask reservoir bag

What are the four devices displayed in Figure one showing different nasal interfaces?

One to five liters per minute

What is the oxygen flow range depicted for a nasal cannula in Figure one?

Five to ten liters per minute

What is the oxygen flow range depicted for a face mask in Figure one?

Two to fifteen liters per minute

What is the oxygen flow range depicted for a Venturi face mask in Figure one?

Ten to fifteen liters per minute

What is the oxygen flow range depicted for a face mask reservoir bag in Figure one?

Liters per minute multiplied by four, plus twenty

What is the mathematical equation used to estimate the FiO2 delivered by a nasal cannula?

Thirty-two percent

Using the nasal cannula equation, what is the estimated FiO2 for a patient on three lpm?