Acute Hypoxic/Hypercapnic Respiratory Failure Flashcards
Normal Inhalation
-Generated by negative intrathoracic pressure
-Increasing volume of the chest creates negative pressure, air moves down the pressure gradient
Normal Exhalation
-Passive process
-Recoil of chest wall, respiratory muscles and lungs themselves
Compliance
-“stiffness” of the lung and the chest wall
-Normally lungs expand easily, some conditions hinder this (e.g. Fibrotic lungs, morbid obesity)
Lung Compliance Equation
-Change in lung volume for a given change in intrathoracic pressure
-Compliance = ΔV/ΔP (normal ~100 mL/ 1 cm H2O)
Resistance
-Diameter of the airways
-Ex: COPD, Asthma, plugged airways (including artificial)
-Relatively small change in radius of airway = large change in resistance
Surface tension of alveoli
-Water lines the alveoli and creates surface tension
-Overcoming this surface tension requires a lot of pressure
Surfactant
-Acts as a detergent and breaks the surface tension
-Prevents nearly complete collapse of alveoli during exhalation
-Makes it easier to breath
Respiratory Centers in the Brain
-Chemo receptors in CNS
-CO2 Chemoreceptors in the aortic and carotid bodies
-Oxygen receptors in the aortic and carotid bodies
Chemoreceptors in the CNS
-Respiratory center in the brain
-Monitor pH of CSF – aggressively control the pH
-Metabolic acidosis compensation (e.g. lactic, ketoacidosis)
P/F Ratio
-An indirect estimate of shunt fraction
-PaO2/FiO2 = x Normal is above 400
Example: 100/0.21 = 476
Example: 90/0.5 = 180
Definition of Ventilation
How effectively CO2 is eliminated from the blood
Respiratory Failure: Hypoxic (Type I) VS. Hypercapnic/Hypercarbic (Type II)
-Respiratory failure may be acute, chronic or acute on chronic
-Multitude of reasons for resp failure
Signs and Symptoms of Hypoxia (Type I)
-Dyspnea
-Cyanosis
-Anxiety
-Restlessness
-Delirium
-Tachypnea
-Bradycardia
-Tachycardia
-Hypertension
-Cardiac Dysrhythmias
-Tremor
Signs and Symptoms of Hypercapnia
-Dyspnea
-Headache
-Htn
-Tachycardia
-Tachypnea
-Bradypnea
-Impaired LOC
-Papilledema
-AMS
Diagnostic Workup for Respiratory Failure
-H&P with physical exam
-ABG
-Labs (CBC, CMP, +/- BNP, D-dimer)
-EKG
-CXR (+/- chest CT, CT PE, V/Q scan)
-exam (pleural effusions, a-lines, b-lines, lung sliding) DVT exam, ascites, more…)