Respiratory Pathophysiology Flashcards
What do pulmonary function tests measure?
Static Lung Volumes
Dynamic lung volumes
Diffusions Capacity
What is FEV1
Forced Expiratory Volume in 1 second
Volume of air that can be exhaled after maximal inhalation in 1 second
Normal = > 80% (this does decline in age)
What is FVC?
Forced Vital capacity
Volume of air that can be exhaled after a maximal inhalation
M: 4.8L
F: 3.7L
What is FVC1 to FVC ratio?
Compares the volume of air expired in 1 second and total volume of air expired
Normal= 75 - 80%
(Useful in determining obstructive vs. restrictive), < 70 suggests obstructive, but normal with restrictive dx.
What is Forced Expiratory Flow at 25-75% Vital Capacity?
Measures airflow in the middle of FEV (FEV 25-75%)
Normal= 100% +/- 25%
Most sensitive indicator of small airway dx, usually reduced with obstructive dx, but normal with restrictive.
What is maximum voluntary ventilation?
Maximum volume of air that can be inhaled and exhaled over the course of a minute
Normal:
M = 140-180 mL
F = 80-120 mL
Best test for endurance
What does the diffusing capacity (DLCO) measure?
Volume of carbon monoxide that can traverse the alveolocapillary membrane per given partial pressure of CO
Normal= 17-25 mL/min/mmHg
(Based on Ficks Law)
What type of patients are at risk for postoperative pulmonary complications?
Age >60
ASA >2
CHF
COPD
Cigarette smoking (> 40 pack years)
In what type of procedures are patients more at risk for postoperative complications?
Aortic > thoracic > upper abdominal > neuro > peripheral vascular > emergency
General anesthesia
Surgery > 2 hours
Which lab value may indicate a risk for postoperative complications?
Albumin < 3.5 (indicates poor nutritional status)
What are some short term effects of smoking cessation?
Carbon monoxide 1/2 =4-6 hrs
P50 returns to near normal in 12 hrs
Short term cessation does not reduce pulmonary complications though
What are some long-term effects of smoking cessation?
Return of pulmonary fx takes about 6 wks. This includes:
Airway function
Mucociliary clearance
Sputum production
Pulmonary immune fx
Hepatic enzyme induction also subsides after 6 wks
What is the best way to reduce anesthesia-related atelectasis?
Alveolar recruitment maneuvers
What are the dynamic volumes (tests) in obstructive dx?
Decreased FEV1
Decreased or increased FEV
Decreased FEV1/FVC ratio
Decreased FEF 25-75%
Normal-increased residual volume
Normal-increased function residual capacity
Normal to increased Total lung capacity
What are the dynamic volumes (tests) in restrictive dx?
Decreased FEV1
Decreased FVC
Normal FEV1 to FVC ratio
Normal FEF 25-75%
Decreased residual volume
Decreased function residual capacity
Decreased total lung capacity
What happens with an extra thoracic obstruction?
For EXTRATHORACIC ~ EXhalation is normal
Patient inhales and the airway collapses (the obstruction is being pulled towards the airway)
Patient exhales and the obstruction is being pushed away
(Inspiratory limb is flat)
What happens with an intrathoracic obstruction?
Remember for an INTRATHORACIC ~ INhalation is normal
The patient inhales and the obstruction is also pulled downwards and away like the rest of the thoracic cavity.
When the patient exhales, the obstruction is push upwards and close, this collapsing the airways
What is asthma?
Acute, REVERSIBLE airway obstruction characterized by chronic airway inflammation and bronchial hyperreactivity
What is the greatest risk factor for developing asthma?
Atopy “the condition of being hyper-allergic”
What is the most common finding in asthma?
Resp alkalosis with hypocarbia (they have tachypnea)
Tachypnea and hyperventilation are result of NEURAL reflexes, not hypoxemia
What does an elevated PaCO2 in asthma show?
Air trapping, resp muscle fatigue and impending resp failure.
What is the anesthetic management of asthma? ( Think airway and vent)
Suppression of airway reflexes!
Avoidance of intubation
Deep extubation should be considered
Vent ~ limit inspiratory time, prolong expiratory time (ok with permissive hypercapnia)
Use an HME filter ~ retains humidity
What is the anesthetic management of asthma (think drugs)
Volatile agents (dilation)
Ketamine (dilation)
Propofol (suppresses reflexes)
Lidocaine (suppresses reflexes)
Avoid histamine-releasing drugs (six, morphine, Demerol)
Iv hydration (reduces viscosity)
How does bronchospasm present?
Decreased breath sounds
Wheezing
Increased peak pressures
Increased alpha angle on EtCO2 (shark fin)
How do you treat bronchospasm
100% FiO2
Deepen the anesthetic
Beta 2 agonist
Inhaled ipratropium (anticholinergic)
Epi
Aminophylline
Helium-oxygen mixture
Hydrocortisone
What is COPD
Umbrella term for chronic bronchitis and emphysema ~ reduction in maximal expiratory flow and a slower forced emptying of the lungs
What are the origins of COPD
Cigarettes
Resp infection
Exposure to dust (coal mining, gold mining)
Alpha 1 antitrypsin deficiency
What are some of the main pathological symptoms of COPD
Loss of elastic components in lung ( decreased recoil —> air trapping)
Reduced airway rigidity ( collapse during exhalation —> air trapping)
Increased gas velocity through narrow airways (decreased pressure in airways —> airway collapse —> air trapping)
Secretions (airflow obstruction and bronchospasm)
What are some common findings with COPD
Flattened diaphragm
Increased AP diameter
Pulmonary bull ar
Increased work of breathing
what is another term for chronic bronchitis?
“ Blue bloaters”
What are some symptoms of chronic bronchitis and how is it defined?
Defined as presence of cough and sputum > 3 months for 2 years
Cigarette common cause
RBCS are over produced (increases blood viscosity)
Chronic hypoxemia and hypercapnia increases PVR —> cor pulmonale
Left heart fx is normal
Weak RV causes back pressure (ascites and liver congestion)
Oxygen therapy is most efficacious therapy
What is another name for emphysema?
“Pink puffers”
Associated with enlargement and destruction of the airways distal to the terminal bronchioles —> reduces surface area for gas exchange—> increase in dead space
What are some common traits associated with emphysema?
Pt has normal (or slightly reduced) PaO2. The PaCO2 is normal or decreased (as result of hyperventilation)
Hypoxemia and hypercarbia can increase PVR later —> RV failure
Alpha-1 antitrypsin deficiency can cause emphysema
What is alpha 1 Antitrypsin Deficiency?
It is a dx where an abnormal variant of the enzyme is produced. The hepatocyte is unable to secrete this enzyme into the blood so it accumulates inside the hepatocyte. This leads to cell death and cirrhosis.
What does alpha-1 antitrypsin Deficiency do to the Lungs?
So alveolar elastase (an enzyme that breaks down pulmonary connective tissue) is kept in check by alpha-1….lack of alpha -1 leads to overactivity of alveolar elastase —> destruction of pulmonary tissue and development of panlobular emphysema.
Where should we maintain a the SaO2 in a patient with severe COPD?
88-92%
Which gas is associated with rupture of pulmonary blebs?
Nitrous oxide
How should you set up your vent for a patient with severe COPD?
Tidal volumes 6-8 mL/kg IBW
Slow inspiratory flow
PEEP
Increase expiratory time to minimize air trapping and auto-PEEP
I.e reduce 1:E ration ~ 1:3, reduce resp rate, and reduce flow resistance by using a larger ETT or frequent suctioning.
What are some etiologies to dynamic hyperinflation with COPD?
High minute ventilation (not enough time to get air out)
Reduced expiratory flow
Increased airway resistance
What are contributing factors to a high minute ventilation?
Large tidal volume
Fast resp rate
What are some factors to reduced expiratory flow?
Bronchoconstriction
Airway collapse
Inflammation
What are some examples of increased airway resistance?
Secretions
Obstructed ETT
Fighting the vent
What are some pulmonary consequences of hyperinflation seen in COPD
Alveolar overdistension
Barotrauma
Pneumothorax
Increased PIP
Increased PP
Increased WOB
What are some cardiac consequences of hyperinflation seen in COPD?
Impaired venous return
Hypotension
Overestimation of CVP and PAOP