Respiratory Disorders Flashcards
What is Respiratory Failure?
“respiratory dysfunction resulting in abnormalities of oxygenation or ventilation (CO 2 elimination) severe enough to threaten the function of vital organs.” (Current 2024)
Type I vs Type II respiratory failure
● Type I Respiratory Failure is the inability to provide sufficient oxygen
à hypoxia
● Type II Respiratory Failure is the inability to remove carbon dioxide
à hypercapnia
Causes of Pulmonary edema
● Increased hydrostatic pressure
● LV dysfunction (eg, myocardial
ischemia, HF)
● Mitral regurgitation
● Left atrial outflow obstruction (eg,
mitral stenosis)
● Volume overload states
● Increased pulmonary capillary
permeability
● Acute respiratory distress syndrome
Parenchymal lung disorders
● Pneumonia
● Interstitial lung diseases
● Diffuse alveolar hemorrhage
syndromes
● Aspiration
● Lung contusion
Pulmonary vascular disorders
● Thromboembolism
● Air embolism
● Amniotic fluid embolism
Chest wall, diaphragm, and pleural
disorders
● Rib fracture
● Flail chest
● Pneumothorax
● Pleural effusion
● Massive ascites
● Abdominal distention and abdominal
compartment syndrome
Acute Resp Distress Syndrome
It is an acute hypoxemic respiratory failure following a systemic or pulmonary insult that results in fluid accumulation in the lungs without evidence of heart failure (cardiogenic pulmonary edema)
“Berlin” definition of ARDS:
1) acute onset,
2) bilateral pulmonary infiltrates on CXR/CT, and
3) poor oxygenation (PaO2/FiO2 <300 mmHGg)
Several disorders/conditions associated with ARDS, 75% are
found in one of three settings:
○ Sepsis (most common)
○ Severe multiple trauma
○ Aspiration of gastric contents
Pathophysiology of ARDS
○ Inflammatory response to the insult (whether primary or secondary)
○ large amounts of pro-inflammatory cytokines are released throughout the lungs
○ Widespread cytokine release triggers immense immune response, damaging the
pulmonary capillary epithelium
○ Damage to the capillary wall –>
○ marked increased capillary permeability, and
○ decreased surfactant production/activity
In ARDS, Damage to the capillary wall à
○ marked increased capillary permeability, and
○ decreased surfactant production/activity
- Interstitial edema
- Alveolar edema
- Alveolar collapse/noncompliance
- Profound hypoxemia
ARDS: Clinical Presentation
● Rapid onset of profound dyspnea.
■ Occurs 6-72 hours after precipitating event
■ Within 12-24 hrs à may see rapid deteriorationà intubate
○ Other signs and symptoms:
■ Tachypnea
■ Frothy pink/red sputum
■ Diffuse crackles
■ Retractions
■ Cyanosis with increasingly severe
hypoxemia (<90%) that is refractory to
oxygen administration
ARDS - Diagnosis
● Once symptoms set in, CXR becomes remarkable:
■ Diffuse or patchy bilateral infiltrates
● Infiltrates rapidly become confluent
● Characteristically spare the costophrenic angle
■ Pleural effusions are small or non-existent
■ Air bronchograms are seen in 80% of cases
CXR findings in ARDS
bilat pulmonary infiltrates
○ Generally normal cardiac silhouette
ABG findings in ARDS
○ PaO2 ↓ (<60 mmHg - always until ARDS resolves)
○ PaCO2 ↑ or normal
BNP findings in ARDS
BNP (helps differentiate ARDS from cardiopulmonary edema)
○ Obtain if enlarged pulmonary cardiac silhouette
■ High - points to cardiopulmonary edema
■ Low/normal - points to ARDS
ABGs importance in ARDS = PaO2 & FiO2
- PaO2 = Measures partial pressure of oxygen in the blood
a. Represents how well we are getting oxygen across the
alveolus into the capillary - FiO2 = fraction of oxygen that the patient is breathing
- PaCo2 = not an important measurement in ARDS
- With PEEP you adjust FiO2 in order to maintain the patient at >90%
saturation
Ratios between PaO2 and FiO2 give you a better idea of the severity of ARDS and contribute to the diagnosis of
ARDS- however this is not the scope of this lecture and more advanced ICU respiratory medicine
ARDS - Treatment Management
- Identification and aggressive treatment of the precipitating condition
- Focus on meticulous and aggressive supportive care.
○ Tracheal intubation
○ Positive pressure mechanical ventilation (PEEP)
■ Target of SaO2 > 88%
Indications for intubation and ventilation include:
○ Hypoxemia despite delivery of supplemental oxygen
○ Upper airway obstruction (epiglottitis, for example)
○ Impaired airway protection (coma)
○ Inability to clear secretions
○ Severe respiratory acidosis
○ Progressive respiratory distress (ARDS, etc)
○ Apnea
Complications of Mechanical Ventilation include:
○ NUMEROUS!
○ Atelectasis (partial or complete collapse of one lung)
○ Hyperinflation (usually of one side)
○ Pneumothorax
○ Ventilator-Acquired Lung Injury
ARDS Prognosis:
○ Mortality rate associated with ARDS is 30-50%.
■ If the ARDS was secondary to sepsis (which is true of about one third of ARDS cases), mortality rate can reach 90%
■ Median survival is about 2 weeks
from onset of ARDS
Infant Resp Distress Syndrome
● IRDS was previously known as Hyaline Membrane Disease.
○ It is the most common cause of respiratory distress in the preterm infant.
● It is caused by prematurity of
the lungs and deficiency in
pulmonary surfactant
IRDS Pathophysiology
○ Without surfactant, alveoli collapse
and gas exchange is hindered.
○ Pulmonary edema and atelectasis can
occur, with hyaline membrane
formation worsening gas exchange
IRDS Clinical Presentation
○ Typical signs of respiratory distress
in the newborn…
■ Dyspnea, retractions, hypoxia, etc
IRDS - Diagnosis
● Chest X-ray:
■ Diffuse sign of interstitial and alveolar congestion in the newborn baby.
■ Air bronchograms.
■ Interstitial reticular pattern (linear-ground glass appearance)
● ABG will usually reveal:
■ Hypoxemia
■ Hypercapnia
■ Respiratory acidosis without compensation
Lecithin-Sphingomyelin Ratio (aka L-S or L/S Ratio)
- Measures two substances:
a. Lecithin (↑↑↑ as pregnancy progresses)
b. Sphingomyelin (stays constant throughout all pregnancy) - These substances are found in the amniotic fluid during pregnancy
- They are surfactants made by the lungs.
- Without surfactants the alveoli collapse (no O2 in the blood)
What are some complications from IRDS
● Alveolar collapse (as already mentioned)
● Patent ductus arteriosus
● If you give too much oxygen supplementation
○ Retinopathy of prematurity
■ Abnormal vessel growth in the retina - can cause detachment
○ Bronchopulmonary dysplasia
■ Chronic lung disease from ventilation
IRDS - Treatment and Management
● Intubation with mechanical ventilation or CPAP with nasal bubble is required.
● Aerosolized exogenous surfactant
IRDS - Prevention
● If an expecting mother is showing signs of premature labor, glucocorticoids can be administered to help stimulate maturation of the baby’s lungs.
■ Prescribed if labor prior to 34 weeks gestation
● With current knowledge and treatment, mortality rate for babies born at 27 weeks gestation or later is at 10%
