Auto PEEP
Pressure above atmospheric remaining in the alveoli at end exhalation due to air trapping AKA intrinsic PEEP
Barotrauma
Physical injury sustained as a result of exposure to ambient pressures above normal, most commonly secondary to positive pressure ventilation (e.g. pneumothorax, pneumo mediastinum)
Dynamic Hyperinflation
Increase in functional residual capacity (FRC) above the elastic equilibrium volume of the respiratory system; causes include increased flow resistance, short inspiratory time, and increased post inspiratory muscle activity
High Frequency Ventilation
Ventilatory support provided at rates significantly higher than normal breathing frequencies
Hypercapnic Respiratory Failure (Type 2)
Inability to maintain normal removal of CO? from the tissues; may be indicated by PaCO? greater than 50 mm Hg in an otherwise healthy individual
Hypoxemic Respiratory Failure (Type 1)
Inability to maintain normal oxygenation in the arterial blood
Maximum Expiratory Pressure (MEP)
Measurement of the output of the expiratory muscles against a maximum stimulus, measured in cm H?O positive pressure
Maximum Inspiratory Pressure (MIP)
Measure of the output of the inspiratory muscles against a maximum stimulus, measured in cm H?O negative pressure
Maximum Voluntary Ventilation (MVV)
Maximum volume of air in L/min that a subject can breathe during a 12 to 15 second period. It is a very patient dependent test.
Muscle Fatigue
Condition involving loss of the capacity to develop force or velocity of a muscle resulting from muscle activity overload, which is reversible by rest.
Noninvasive Ventilation (NIV)
Mechanical ventilation without endotracheal intubation of tracheotomy, usually via a form fitting mask
Positive End Expiratory Pressure (PEEP)
Application and maintenance of pressure above atmospheric at the airway throughout the expiratory phase of positive pressure mechanical ventilation
Pressure Control Ventilation
Mode of ventilatory support in which mandatory support breaths are delivered to the patient at a set inspiratory pressure
Respiratory Alternans
Alternating between use of the diaphragm for short periods and use of the accessory muscles to breathe; indicative of end stage respiratory muscle fatigue
Tension Time Index
Product of contractile force (ratio of diaphragmatic pressure to maximum diaphragmatic pressure) and contractile duration (ratio of inspiratory time to total breathing cycle time) used to indicate a level of contraction associated with fatigue
Work of Breathing
Amount of force needed to move a given volume into the lung with a relaxed chest wall
Respiratory Failure
Inability to maintain either the normal delivery of oxygen to the tissues or the normal removal of carbon dioxide from the tissues and often results from an imbalance between respiratory workload and ventilatory strength of endurance
Respiratory Failure is defined as (#'s)
Arterial partial pressure of oxygen (PaO?) less than 60 mm Hg
OR
Alveolar partial pressure of carbon dioxide (PaCO?) greater than 50 mm Hg
Hypoxemic (Type 1) Respiratory Failure
Occurs when the primary problem is inadequate oxygen delivery
Hypercapnic (Type 2) Respiratory Failure
Describes "bellows failure" of the lungs resulting in elevated CO? levels
Hypercapnic Respiratory Failure is also known as
Ventilatory Failure
What is the term for Respiratory Failure due to inadequate ventilation
Hypercapnic (Type 2) Respiratory Failure
What are the primary causes of hypoxemia
Ventilation/Perfusion mismatch
Shunt
Alveolar hypoventilation
Diffusion impairment
Perfusion/diffusion impairment
Decreased inspired oxygen
Venous admixture
What is the most common cause of hypoxemia
Ventilation/Perfusion Mismatch
Pathologic V/Q mismatch occurs when
Disease disrupts the balance, and hypoxemia results
What are the causes of V/Q mismatch
Obstructive Lung diseases
Bronchospasm
Mucous Plugging
Inflammation
Premature airway closure that signal asthmatic or emphysematous exacerbations
Infection
Heart Failure
Inhalation injury may lead to partially collapsed or fluid filled alveoli
What is the clinical presentation of a patient with V/Q mismatch
Hypoxemia commonly manifests with dyspnea, tachycardia, and tachypnea, use of accessory muscles, nasal flaring, lower extremity edema, peripheral or central cyanosis
Severe hypoxemia can lead to
Significant central nervous system dysfunction, ranging from irritability to confusion to coma
Bilateral wheezing especially any young patients in respiratory distress often identifies
The bronchospasm of asthma
Upper airway disease or fluid filled airways may also result in
Wheezing
Breath sounds that are diminished bilaterally are common in
Emphysema
Wheezing in one lung may identify
Endobronchial lesion
Absence of breath sounds on one side of the chest may reveal
Collapse, infection, edema, or effusion as potential causes of the Q mismatch
Radiographically, V/Q mismatch can manifest as a _____________ radiograph, with large or hyper inflated lungs as in the case of obstructive disease
black
A __________ chest radiograph is evident when alveoli are partially occluded
White
True/False
A shunt does not respond to supplemental oxygen
TRUE, because the gas exchange unit (the alveolus) is not open
True/False
V/Q mismatch does not respond to supplemental oxygen
FALSE, V/Q mismatch responds to supplemental oxygen
What is a Shunt
An extreme version of V/Q mismatch in which there is no ventilation to match perfusion
About 2% to 3% of the blood supply is shunted via
The bronchial and thebesian veins that feed the lungs and heart; this is a normal anatomic shunt
Pathologic anatomic shunt occurs as a result of
Right to left blood flow through cardiac openings (artial or ventricular septal defects) or in pulmonary arteriovenous malformations
Physiologic shunt leads to hypoxemia when
Alveoli collapse or are filled with fluid or exudate
The causes of physiologic shunting
Atelectasis
Pulmonary edema
Pneumonia
Clinical Presentation of Shunt
Similar to V/Q mismatch
Bilateral of unilateral crackles
Shunt usually manifests with a _________ chest x ray
white
V/Q mismatch usually manifests with a ______ chest x ray
black
Shunting can be diagnosed by
Using 100% oxygen breathing techniques
Contrast enhanced echocardiography
Macro aggregated albumin scanning
Pulmonary angiography
Shunt is differentiated from V/Q mismatch by
The lack of increase in PO? as FiO? is increased
Diffusion
The movement of gas across the alveolar capillary membrane secondary to a pressure gradient
Does diffusion impairment become more pronounced at rest or during exercise
During exercise because it limits the time for gas exchange
Diffusion impairment is commonly found in patients with what diseases
Patients with interstitial lung disease
Pulmonary fibrosis
Asbestosis
Sarcoidosis
The thickening and scarring of the interstitium undermine normal gas exchange
Emphysema
Pulmonary vascular abnormalities like anemia, pulmonary hypertension and pulmonary em
Clinical Presentation of Diffusion Impairment
Signs and Symptoms are related to the specific disease
Interstitial lung disease may be the diagnosis of a dyspneic patient with a dry cough and fine basilar crackles
Digital clubbing
Joint abnormalities
Raynaud disease
Pulmonary Hypertension may manifest with signs of
Right sided heart failure such as edema, jugular venous distention, and a louder pulmonary component of the second heart sound
Perfusion/Diffusion Impairment
A rare cause of hypoxemia found in individuals with liver disease complicated by hepatopulmonary syndrome
Perfusion/Diffusion Impairment
Right to left intra cardiac shunt combines with dilated pulmonary capillaries resulting in impaired gas exchange
What can be used to over come Perfusion/Diffusion Impairment
Significant supplemental oxygen the gas transfer reduction
Clinical presentation of Perfusion/Diffusion Impairment
Obvious signs of liver disease
Digital clubbing
Platypnea
Orthideoxia
Decreased Inspired Oxygen
Clinically uncommon, hypoxemia may develop when the inspired oxygen is less than body requirements
What is the most common situation for decreased inspired oxygen
High altitude
What is the clinical presentation of decreased inspired oxygen
The signs are symptoms of hypoxemia may be present, with the cause clearly related to the patient environment
such as altitude
What is the treatment for decreased inspired oxygen
Supplemental oxygen
Venous Admixture
A decrease in mixed venous oxygen increase the gradient by which oxygen needs to be stepped up as it passes through the lungs
What is the most common cause of lox mixed venous oxygen, owing to increased peripheral extraction of oxygen
Congestive heart failure with low cardiac output
What are the three main causes of Hypoxemic Respiratory Failure
Hypoventilation
V/Q mismatch
Shunt
How does hypoventilation differ from other causes of Acute Hypoxemic Respiratory Failure
Manifesting with a normal alveolar to arterial PO? difference
Hypercapnic Respiratory Failure (type 2)
An elevated PaCO?, creating an uncompensated respiratory acidosis (Weather acute or acute on chronic)
Hypercapnic Respiratory Failure (type 2) is also known as
Pump failure or ventilatory failure
Are PaCO? and alveolar ventilation directly or inversely related
Inversely
What causes hypercapnic respiratory failure do to a decreased ventilatory drive
Drug overdose or sedation
Bilateral carotid endarterectomy with incidental resection of the carotid bodies
Brainstem lesions
Disease of the CNS such as multiple sclerosis or Parkinsons
Hypothyroidism
Morbid obesity (obesity hypoventilation)
Sleep apnea
Me
What diseases cause muscle weakness/fatigue
Guillain Barre Syndrome
Myasthenia gravis
COPD
Kyphoscoliosis
Obesity
Guillain Barre Syndrome
Lower extremity weakness progressing to the respiratory muscles in one third of patients (Ascending)
What disease are associated with Hypercapnic respiratory failure
COPD
Asthma
Upper airway obstruction
Obesity hypoventilation
Pneumothroax
Severe burns
Chest wall disorders (khyphoscoliosis)
Ankylosing spondylitis
Chronic and acute hypercapnic respiratory failure can be differentiated by the severity of change in
pH
Acute Hypercapnic Failure
pH decreases 0.08 for every 10 mm Hg increase in PaCO?
Chronic Hypercapnic Failure
pH decreases 0.03 of every 10 mm Hg in PaCO?
What are the most commonly used tests to assess respiratory muscle strength at the bedside
Maximum inspiratory pressure (MIP)
Maximum expiratory pressure (MEP)
Forced Vital Capacity
Maximum voluntary ventilation (MVV)
MIP of _________ cm H?O or less (more negative) usually indicates adequate respiratory muscle strength to continue spontaneous breathing
-30
Contractile Muscle fatigue
A reversible impairment in the contractile response to a neural impulse in an overloaded muscle
Central muscle fatigue
An exertion induced, reversible decrease in central respiratory drive
Transmission muscle fatigue
An exertion induced, reversible impairment in the transmission of neural impulses
Respiratory muscle weakness
The decreased capacity of a rested muscle to generate force and decreased endurance
Respiratory muscle weakness occurs most commonly in patients with
Neuromuscular disease
COPD
Kyphoscoliosis
Obesity
Fatigue
A condition in which there is loss of the capacity to develop force or velocity of a muscle resulting from muscle activity under load, which is reversible by rest
When does fatigue occur
Work of breathing
Hypoxemia
decreased inspiratory muscle efficiency
Poor nutrition
inability of a muscle to extract energy from supplied substrates