Respiratory Flashcards
What nerve can be damaged during a tracheostomy?
Recurrent laryngeal nerve
What muscle must be separated at midline during tracheostomy?
Sternohyoid muscle
Risk factors associated with aspiration pneumonia
GI: refractory vomiting, pancreatitis, intussusception, FB, ileus Anesthesia Esophageal disease: megaesophagus, motility dz, hiatal hernia, stricture, esophagitis Neuro: polyneuropathy, myasthenia gravis, seizures, prolonged recumbency Cricopharyngeal dyssynchrony Muscular dystrophy Oropharyngeal dysphagia Laryngeal disease
Causes of lobar alveolar consolidation
aspiration pneumonia lung lobe torsion atelectasis secondary to mucus plugging
Causes of focal alveolar consolidation
Airway foreign body Primary pulmonary neoplasia Metastatic neoplasia NCPE
Causes of diffuse alveolar pattern
ARDS CHF Fluid overload Eosinophilic bronchopneumopathy Coagulopathy Metastatic neoplasia
Causes of diffuse or focal interstitial pattern
early bacteria pneumonia Imminent CHF Pneumocystitis carinii infection Inhalant Toxicity Viral pneumonia
Bacteria commonly isolated from airway samples of canine pneumonia patients
B bronchiseptica (22-49%) E coli (11-17%) Klebsiella pneumoniae (2-6%) Pasteurella (3-21%) Mycoplasma (30-70%) Streptococcus (6-13%) Staphylococcus (14%) Anaerobes (5-17%)
Reasons to AVOID bronchodilators
May worsen V/Q mismatch May allow exudates to spread Inotropic/vasodilator effects may increase perfusion to poorly ventilated units May prevent hypoxic vasoconstriction may suppress cough reflex
Reasons to GIVE bronchodilators
Antiinflammatory -inhibit mast cell degranulation -decrease microvascular permeability and leak -increase mucociliary transport speed Respiratory stimulant Increase diaphragm contractility Increase resistance of diaphragm fatigue
5 classification of pulmonary hypertension
- pulmonary arterial hypertension 2. left-sided heart disease 3. lung disease and/or hypoxemia 4. chronic thrombotic/embolic disease 5. Miscellaneous
For canine pyothorax, what are the most common OBLIGATE ANAEROBES?
peptostreptococcus, bacteroides, fuesobacterium, prevotella, porphyromonas
For canine pyothorax, what are the most common AEROBES?
Pasteurella, e. coli, actinomyces, streptococcus (S. canis), and staphylococcus
MOA of doxapram
General CNS stimulant - direct stimulation of medullary respiratory center possibly through reflex activation of carotid and aortic chemoreceptors
Paradoxical laryngeal motion is defined as?
INward movement of the arytenoids secondary to negative pressure generated upon inspiration
How much resistance to airflow during inspiration is from the nose in normal dogs?
80%
What is the most important aspect of surgery for brachycephalic airway syndrome?
widening of the nares
What is a possible alternative to permanent tracheostomy in dogs with tracheal COLLAPSE
cricoarytenoid lateralization with thyroarytenoid caudolateralization
What % of cats with nasopharyngeal disease have nasopharyngeal polyps?
28%
Traction-avulsion is the most simple way to remove nasopharyngeal polyps, but is associated with what recurrence rate?
40 to 50%
What is the recommended treatment for nasopharyngeal polyps?
ventral bulla osteotomy
Radiographs misdiagnosed the location of tracheal collapse in what % of dogs?
44%
what bacteria may be cultured from the airway of normal dogs?
pasteurella, staphylococcus, streptococcus, klebsiella
What are the most common bacteria associated with tracheal collapse?
pseudomonas, pasteurella, e coli, staphyloccoci
Common nasal neoplasia in dogs vs cats?
Dogs: carcinomas or sarcomas Cats: lymphoma most common
Describe the airway changes seen in allergic airway disease
Bronchial or alveolar inflammatory changes, submucosal wall edema, increased bronchial secretions, smooth muscle hypertrophy, smooth muscle constriction of bronchioles and small bronchi
Name diseases that included in small animal allergic airway disease
canine allergic bronchitis (eosinophilic bronchopneumopathy), parasitic larval migration, pulmonary infiltrate with eosinophils, feline asthma
Describe the pathogenesis in human asthma
IgE ab cross link to mast cells in submucosa of bronchi and bronchioles of lungs, causing mast cell degranulation. Leads to release of inflammatory mediators that cause airway constriction
Name the inflammatory mediators involved in human asthma
Leukotrienes, histamine, eosinophilic chemotactic factor, bradykinin
Common parasites implicated in inflammatory pulmonary disease?
Ancylostoma, Toxocara (both primary intestinal that migrate through lung), Paragonimus, Crenosoma, Filaroides, Capillaria, Aelurostrongylus
Pathophysiology of parasites in lungs?
Type I hypersensitivity reaction that leads to bronchoconstriction and inflammation
Define and give causes of pulmonary infiltrates with eosinophils (PIE)
Umbrella term that describes several diseases that cause eosinophilic airway inflammation. Includes heartworms, drugs, parasites, inhaled allergens
Pathogenesis of feline bronchopulmonary disease?
Cellular inflammatory response, lower airway hyperreactivity (ease with which airways narrow in response to stimuli)
Most common cause of coughing in cats?
Feline bronchopulmonary disease
What % of cats with bronchopulmonary disease do not have coughing in history or PE findings?
16%
Breed of cat that is over-represented in cats with lower airway disease?
Siamese
Tests that should be performed in cats with suspected bronchopulmonary disease?
Fecal, heartworm antigen/antibody testing, radiographs, CBC, Chem, UA
Describe the radiographic appearance of feline bronchopulmonary disease
increase in bronchial densities (doughnuts, tram lines, train tracks), increased interstitial markings, alveolar pattern, hyperinflation of lung fields, flattening of diaphragm
What % of cats with bronchopulmonary disease have consolidation and alveolar infiltration of R middle lung lobe?
11%
Bronchoscopic findings in cats with bronchopulmonary disease?
Thick mucus secretion, hyperemic and edematous mucosa
Which type of diagnostic test (BAL, ETW, TTW) provides samples that are most representative of the lower respiratory cell population?
BAL
True or false- The cat’s lower airways are sterile
False- normal to have <2000 CFU/ml
T or F: Cats with bronchopulmonary disease are less likely to have mycoplasma colonization?
False
Treatment options for allergic airway disease in dogs and feline bronchopulmonary diseaes?
Glucocorticoids, bronchodilators, cyclosporine, cyproheptadine, tyrosine kinase inhibitors, leukotriene receptor blockers
How might cyclosporine help in allergic airway disease:?
inhibits the T helper cells of the immune system, which are a primary component of the allergic immune response
Two classes of bronchodilators
Methylxanthines (theophylline, aminophylline) & B2 receptor agonists (terbutaline or albuterol)
Common types of chest wall neoplasia?
Osteosarcoma, fibrosarcoma, lipoma, mast cell tumor, hemangiosarcoma
In what situations should rib fractures be repaired?
When they are causing injury to underlying structures or interfering with ventilation
2 main reasons why flail chest causes respiratory distress?
1) Pain 2)Underlying diseases such as contusions, pneumo, etc are common with flail chest
How does cervical spinal disease cause hypoventilation?
The medullary respiratory center sends information via the reticulospinal tracts to the phrenic nerve and the segemental intercostal nerves. The phrenic nerve leaves the spinal cord between C4-C6 and provides motor innervation to the diaphragm. The segmental intercostal nerves leave the spinal cord between C6-T2.
T/F- Cranial nerve deficits can be seen with botulism?
True- coonhound paralysis, on the other hand, does not cause CN deficits
Causes of allergic airway disease
Parasitic allergic airway disease, allergic bronchitis, feline asthma, PIE
More specific term for allergic bronchitis
Eosinophilic bronchopneumanopathy
Allergic airway diseases characterized by:
- Sub mucosal wall edema 2. Increased bronchial secretions3. Smooth muscle hypertrophy4. Smooth muscle constriction of bronchioles and small bronchi
Human asthma: IgE antibodies cross link to _______ in the ________ and ________ causing _________.
Mast cells, sub mucosa of the bronchi and bronchioles of the lung, mast cell degranulation
In human asthma degranulation of mast cells leads to the release of the following inflammatory mediators:
Histamine, leukotrienes, eosinophilic chemo tactic factor, bradykinin
Name 4 airway changes caused by inflammatory mediators in human asthma
Pulmonary mucosal edema, smooth muscle hypertrophy of bronchi and bronchioles, accumulation of pulmonary secretions, airway narrowing
Most common migratory parasite to cause allergic response in canine lungs
Toxocara canis
True/False: Ancylostoma caninum is a known cause of feline parasitic allergic airway disease
False…causes disease in dogs only
List 6 causes of canine parasitic allergic airway disease
- Capillaria aerophilia2. Filaroides hirthi3. Crenosoma vulpis4. Paragonimus kellicotti5. Intestinal parasite migration6. Dirofilaria immitis
List 4 causes of feline parasitic allergic airway disease
- Aelurostrongylus abstrusus2. Capillaria aerophila3. Paragonimus kellicotti4. Dirofilaria immitis
Distribution of Aelurostrongylus abstrusus
Southern US and worldwide
Distribution of Filaroides hirthi
North America, Japan, Europe
Distribution of Paragonimus kellicotti
Great Lakes, Midwest, Southern US
How does dirofilaria immitis cause an allergic inflammatory response?
Large numbers of antimicrofilarial antibodies entrap microfilariae within the pulmonary capillaries
Signalment of dogs with allergic bronchitis?
Younger, Siberian Huskies and Alaskan Malamutes over represented
Most common radiographic finding with canine allergic bronchitis
Diffuse, prominent bronchointerstitial pattern. Alveolar infiltrates (40%), and bronchiectasis (26%) also seen
Expected bronchoscope findings with canine allergic airway disease
Abundant yellow/green mucous, thickening with irregularities or polyploid changes to mucosa, exaggerated airway closure during expiration
Expected airway sampling findings in dogs with allergic bronchitis
More than 50% eosinophils (87% of dogs), 20-50% eosinophils (remaining 13% of dogs)
Causes of PIE
Pulmonary or migrating parasitesHeartworms (65% of cases)DrugsInhaled allergens
Difference between PIE and allergic bronchitis?
PIE is a pulmonary parenchymal disease, allergic bronchitis is lower airway
Radiographic changes expected with PIE?
Diffuse interstitial, bronchial, or alveolar pattern, many have hilar lymphadenopathy
Most common cause of coughing in cats?
Feline bronchopulmonary disease
What breed is over-represented in feline bronchopulmonary disease?
Siamese
T/F: a peripheral eosinophilia is common in feline bronchopulmonary disease
False- only 9% of cats with peripheral eosinophilia had this disease
Most common and persistent radiographic finding in feline heart worm disease
Bronchointerstitial pattern even without changes in the pulmonary vasculature
Common radiographic signs of feline bronchopulmonary disease
- Increase in bronchial densities2. Increase in interstitial markings3. Alveolar pattern4. Hyper inflated lungs with flattening of diaphragm5. Alveolar infiltrate with right middle lung lobe consolidation
Rare radiographic consequences of feline bronchopulmonary disease:
- Pneumothorax2. Lung lobe torsion3. Bronchiectasis
Common bronchoscope findings with feline bronchopulmonary disease
Thick mucous secretions in lower airways, hyperemic and edematous mucosa
Most predominant cell types in bronchial washings of cats with bronchopulmonary disease
Neutrophils (33% of cats) and eosinophils (24% of cats); mast cells found infrequently (up to 8% of cells), macrophages (22% of cats)….mixed cell population in 21% of cats
Mainstays of emergency therapy for allergic airway disease
Steroids, bronchodilators, oxygen
2 classes of bronchodilators for allergic airway disease
Methylxanthines, Beta 2 agonists
Which class of bronchodilators preferred for long term therapy? Why?
Methylxanthines - tolerance to Beta agonists may occur which then decreases efficacy in emergency situations
List 3 miscellaneous drugs to treat feline asthma
- Cyclosporine - inhibits helper T cells2. Cyproheptadine inhibits feline airway smooth muscle contraction in vitro3. Masitinib tyrosine kinase inhibitor may decrease airway eosinophilia and improve pulmonary mechanics in feline asthma
NCPE PCWP?
Categories of NCPE
Post obstructive, neoruogenic, ALI/ARDS, drowning, smoke inhalation, adverse drug effects, anaphylaxis, oxygen toxicity, pulmonary embolus
Possible source of ARDS (NCPE review, compendium 2012)
SIRS, sepsis, panc, pneumonia, neoplasia, uremia, parvovirus
Respiratory interstitial space contains
Connective tissue, fibroblasts, macrophages, small arteries, veins, lymphatic channels
As lymph drains from alveoli to hilus of the lungs, net hydrostatic pressure in the pulmonary interstitium __________ and the potential space for fluid accumulation __________.
Decreases, increases
Landis Pappenheimer formula does what?
Calculates COP: COP = 2.1TP + [0.16TP^2] + [0.009TP^3]
Diseases of the chest wall include…
Congenital anomalies, neoplasia, trauma (rib fx, flail chest, penetrating wounds), cervical spine dz, and neuromuscular dz
List the 2 main functions of the chest wall
- Protect internal thoracic structures2. Muscles and nerves necessary for normal respiration
What blood gas abnormality is most common with chest wall disease?
Hypoventilation/increased PCO2
What breathing pattern expected with chest wall disease?
Paradoxical…abdomen moves in on inspiration instead of out
Most common congenital chest wall abnormality?
Pectus excavatum…inward concavity of sternum and costal cartilages.
How does respiratory distress occur with pectus excavatum?
Restrictive ventilation or paradoxical movement of the deformity during inspiration
Pectus excavatum should always be surgically corrected T/F?
False…only corrected if significant respiratory impairment
List the 6 most common chest wall masses
Lipoma, chrondrosarcoma, fibrosarcoma, osteosarcoma, MCT, hemangiosarcoma
Define flail chest
Fracture of several adjoining ribs resulting in a segment of the thoracic wall that has lost continuity with the rest of the hemithorax…fractured segment moves paradoxically throughout respiration
What are the 2 main reasons patients with flail chest have respiratory distress?
- Hypoventilation secondary to pain2. Hypoxemia from other injuries such as pneumothorax, hemothorax, pulmonary contusions, diaphragmatic hernia
List 3 causes of non-traumatic rib fractures in cats
Chronic respiratory disease (asthma, pneumonia, upper airway obstructions), CRD, neoplasia
Where are non traumatic rib fractures typically located?
Mid rib, caudal aspect of the rib cage
In cats what is the proposed mechanism of Hypoventilation with cervical spine dz?
Afferent tracts to respiratory center may be damaged in cervical spinal Sx
How does cervical spinal dz cause Hypoventilation in dogs?
Unknown; postulated that medullary respiratory center sends info via reticulospinal tracts to phrenic nerve and segmental intercostal nerves. If these pathways are interrupted can cause ventilatory failure.
The ________leaves the spinal cord between the 4th and 6th vertebral bodies and provides ______________ to the diaphragm
Phrenic nerve; motor innervation
The ___________ innervate the intercostal muscles and leave the spinal cord between ______ and ______.
Segmental intercostal nerves; C6 , T2
Tick paralysis induced when female tick secretes______ that ______ or _______.
Neurotoxin, inhibits depolarization of motor nerves or blocks release of acetylcholine
List 2 ticks most commonly responsible for tick paralysis in US
American dog tick (Dermacenter variabilis), Rocky Mountain wood tick (Dermacenter andersoni)
When do signs develop in tick paralysis?
1 week after attachment of tick
Tick paralysis in Australia most common from what tick?
Ixodes holocyclus
How is tick paralysis different in Australia vs US?
Australia more severe, most require vent (median 23 hours), hospitalization 3-4 days. Vent due to Hypoventilation good (90% survived), not as good with hypoxemia (53% survive)
What things were found to be improved in a patient with biologically active ventilation compared to standard ventilation?
improved arterial oxygenation, lung mechanics, degree of lung edema, redistribution of pulmonary blood flow, proinflammatory cytokine production, histologic damage
What are the 3 fundamental settings for assist control ventilation?
RR, tidal volume, inspiratory flow rate
what is the only part of the breathing cycle that is variable with assist controlled ventilation (and is only variable when the patient triggers the breath)
expiratory time
Things that can be adjusted bedside during assist controlled ventilation?
inspired O2 concentration, trigger sensitivity, resp rate, tidal volume, insp flow rate, end insp pause, external PEEP
T/F- achieving normocapnea is a goal of mechanical ventilation?
false
in what disease state is achieving normocapnea VERY important?
brain disease
Heavy sedation can cause what disturbance with assist control ventilation?
ineffective triggering
Define hypoxia
Decrease in level of oxygen supplied to tissues
Define hypoxemia
Inadequate oxygenation of arterial blood and is defined as PaO2<80 mm Hg (at sea level)
DO2 =
CO x CaO2
List 5 causes of hypoxemia
HypoventilationVQ mismatchDiffusion impairmentDecreased FiO2Intrapulmonary shunt
Which of the 5 causes of hypoxemia do not respond to oxygen supplementation?
Intrapulmonary shunt
When is supplemental oxygen indicated?
SpO2< 93%
Arterial oxygen content formula
[1.34 (ml O2/g) x SaO2 (%) x Hb (g/dL)] + [0.003 (ml O2/dl/mmHg) x PaO2 (mm Hg)]
Risks of using non-humidified oxygen:
- Drying and dehydration of nasal mucosa2. Respiratory epithelial degeneration3. Impaired mucociliary clearance4. Increased risk of infection
What is hyperbaric oxygen
100% oxygen under supraatmospheric pressures (>760 mm Hg) to increase the percent dissolved oxygen in bloodstream by 10-20%
Phases of oxygen toxicity
- Initiation: 24-72h of exposure to 100% O2; ROS damage2. Inflammatory phase: pulmonary epithelial lining destroyed and inflammatory cells recruited, massive release of inflammatory mediators results in increased tissue permeability and pulmonary edema3. Destruction: severe local destruction, many die4. Proliferation: type 2 pneumocytes and monocytes recruited5. Fibrosis: collagen deposition and interstitial fibrosis
Correlation b/t PaO2 and SaO2
PaO2 500 = 100% SaO2
PaO2 125 = 99% SaO2
PaO2 100 = 98% SaO2
PaO2 80 (hypoxemia) = <90%P50
PaO2 29, SaO2 50
Primary physiologic cause of hypoxemia.
Low FiO2Global hypoventilationVenous admixture
Causes of venous admixture
Low V/Q regionAtelectasis (no V/Q)Diffusion defectsRight to left shunts (PDA, VSD, intrapulmonary AV shunt)
Thickness of an alveolar wall
0.3 um
What is the smallest airway without aveoli?
terminal bronchioles
Conducting ariways end with…
terminal bronchioles
What is anatomic dead space?
Airway w/o alveoli - ends at terminal bronchioles
Define acinus
portion of lung distal to terminal bronchiole
External intercostal muscles aid in..
Inhalation
Internal intercostal muscles aid in…
Forced exhalation
Where does the velocity of gas decrease the most in the?
terminal bronchioles (so inhaled particles end up here most)
Weibel diagram
Conducting zone = trachea –> bronchi –> bronchioles –> terminal bronchiolesTransitional and respiratory zone –> respiratory bronchioles –> alevolar ducts –> alveolar sac
Respiratory capillary diameter
7-10 um
How long does an RBC spend in the capillary network?
0.75 s
Bronchial circulation supplies.
Conducting zone (trachea to terminal bronchioles)
Surface area of the lungs
50-100 meters squared
aveoli in lung
500 million
Alveoli diameter
0.3 mm
Function of surfactant
Decrease surface tension in alveoli
When oxygen moves from the thin side of the blood-gas barrier from the alveolar gas to hemoglobin of the RBC, it traverses the following layers in order:
Surfactant, epithelial cell, interstitium, endothelial cell, plasma, red cell membrane
What is the PO2 of inspired gas at Mt. Everest (barometric pressure of 247 mm Hg)?
247-47 (water vapor) x 0.21 = 42 mm Hg
What is the predominant mode of gas flow in the alveolar ducts?
Difffusion
Define tidal volume
volume inspired normally
Devine vital capacity
Max inspiration and max expiration = inspiratory reserve volume + tidal volume + expiratory reserve volume
Residual volume
gas that remained in lung after maximal expiration
Functional residual capacity
volume of gas in lung after a normal expiration = expiratory reserve volume + residual volume
Inspiratory capacity
Tidal volume + inspiratory reserve volume
What does Boyle’s law state?
Pressure x volume is constant (at constant temperature)PV = K
What is alveolar ventilation?
Volume of fresh gas entering the respiratory zone each minute; (tidal volume - dead space) x resp freq
How can you increase alveolar ventilation?
increased tidal volume or respiratory frequencyIncreasing tidal volume more effective b/c reduces proportion of each breath occupied by anatomic dead space
What is the alveolar ventilation equation?
VA = (VCO2/PCO2) x K
What is anatomic dead space?
Volume of the conducting airways
What is the Bohr equation?
VD/VT = (PACO2-PECO2)/PACO2VD = dead spaceVT = tidal volumeA = alveolarE = mixed expiredBohr eqn: AEA (my initials:)All of the expired CO2 comes from the alveolar gas and none from the dead space. MEASURES PHYSIOLOGIC DEAD SPACE
What is the normal ratio of dead space:tidal volume during resting breathing?
0.2-0.35
What is physiologic dead space?
Volume of gas that does not eliminate CO2
T/F. Anatomic dead space increases with many lung diseases
F - physiologic dead space increases
T/F. Upper regions of the lung ventilate better than lower regions.
F - Lower regions ventilate better than upper zones
What lung volumes cannot be measured with a simple spirometer?
total lung capacity, functional residual capacity, residual volumeThey can be measured with helium dilution or body plethysomograph
T/F. The concentration of CO2 (and therefore its partial pressure) in alveolar gas and arterial blood is inversely related to the alveolar ventilation.
T
What does Fick’s law state regarding diffuson?
The rate of transfer of a gas through a sheet of tissue is proportional to the tissue area and the difference in gas partial pressure between the two sides, and inversely proportional to the tissue thicknessDiffusion rate proportional to partial pressure differenceDiffusion rate proportional to solubility of gas in tissue and inversely propotional to its molecular weight
CO2 diffuses ____ times more rapidly than O2 because it ha a higher _____
20 xsolubility
Transfer of carbon monoxide is….
diffusion limited b/t the amt of CO that gets into blood limited by diffusive properties and not amt of blood available
What gas is perfusion limited?
nitrous oxide (doesn’t bind with Hbg so partial pressure rises rapidly in blood, so blood flow depends on uptake)
T/F. Under resting conditions, the capillary PO2 virtually reaches that of alveolar gas when red cell is 1/3rd the way along the capillary.
T
Diffusion process challenged by:
exercise, alveolar hypoxia, thickening of the blood-gas barrier
Normal diffusing capacity
25 ml/min/mmHgcarbon monoxide used to determineFormula = VCO2/PACO2
T/F. Oxygen transfer is normally diffusion limited.
F - Perfusion limited
Under what circumstances does oxygen transfer become diffusion limited?
Intense exercise, thickened blood-gas barrier, alveolar hypoxia
What is transmural pressure?
Pressure difference between the inside and outside of capillaries
What is normal pulmonary vascular resistance?
1.7 mm Hg/L/min
What are the two mechanisms for why an increase in pulmonary arterial venous or arterial pressure causes the pulmonary vascular resistance to fall?
Recruitment (opening of previously closed) and distension (increase caliber of vessels)Recruitment more with increase in arterial pressureDistention more with increase in venous pressure
What is hypoxic pulmonary vasoconstriction?
Contraction of smooth muscle in the walls of the small arterioles in the hypoxic region. PAO2 of pulmonary gas determines this reaction. When PAO2 < 70 mm Hg, marked vasoconstriction occurs.
What is the primary constituent of pulmonary surfactant?
dipamlitoyl phosphatidylcholine
Ratio of total systemic vascular resistance to pulmonary vascular resistance
10:1
What two wave wavelengths do pulse oximeters use?
660 and 940 mm
What are the 4 causes of venous admixture?
low VQ regions, small airway and alveolar collapse (atelectasis), diffusion defects, anatomic right to left shunts
T/F Cats have a right shift oxygemoglobin dissociation curve compared to dogs
T
What are examples of diffusion defects for venous admixture?
Oxygen toxicity, smoke inhalation, ARDS
T/F. Oxygen concentration is lower at higher altitudes
F - Still 21%, barometric pressure is lower so PatmO2 is lower
What gas is highest in the alveoli?
nitrogen (560 mm Hg)
T/F. Hypoventilation is a cause of hypoxemia in patients breathing room air but not in patients breathing enriched oxygen mixtures
T - With 100% oxygen, nitrogen is decreases to nearly 0 and oxygen increases to 665, alveolar CO2 could theoretically rise to 550 mm Hg before the alveolar oxygen decreased to a level that would lead to hypoxemia (PaO2 <80)
What is the difference between a physiologic shunt and a true or anatomic shunt?
physiologic: blood flowing past nonfxnal alveolitrue: blood completely bypasses alveoli (be they fxnal or not)
What cell proliferation is responsible for diffusion defect?
cuboidal, type 2 pneumocytes (normal is flat type 1)
What is the normal A-a gradient?
20 mm Hg = venous admixture
What is minute ventilation?
TV x RRalveolar and dead space ventilation
What are causes of hypercapnia?
hypoventilation, increase in dead space ventilation, increased CO2 production, increased inspired CO2
Fowler’s method measures what?
Anatomic dead spaceMeasures concentration of a tracer gas (nitrogen) over time
Bohr’s method measures what?
Physiologic dead spaceVolume of lung that does not eliminate CO2
What is the conclusion from the alveolar ventilation equation (VA = (VCO2/PaCO2) x K)
The only physiologic reason for increased PaCO2 is level of alveolar ventilation that is inadequate for the amount of CO2 produced by tissues
Normal dog PaCO2
30-42 mm Hg
Normal cat PaCO2
25-36 mm Hg
Venous CO2 is usually ___ higher than arterial CO2
3-6 mm Hg
What are the 3 neurons involved in the respiratory control center in medulla and pons?
- medullary respiratory center2. apneustic center3. pneumotaxic center
The medullary respiratory center is split into ….
Dorsal and ventral respiratory group
What is special about the dorsal respiratory group?
Located in region of nucleus tractus solitarius, where visceral afferents from cranial nerves IX and X terminateresponsible primarily for INSPIRATION (intrinsic periodic firing)
What are the 4 nuclei in the ventral respiratory group of the medullary resp center?
- Nucleus retrroambiguus2. Nucleus para-ambiguus3. Nucleus retrofacialis4. pre-Botzinger complex
What is the job of the ventral resp group of medullary resp center?
Controls voluntary forced exhalation and acts to increase the force of inspiration
What does the apneustic center do?
coordinates the speed of inhalation and exhalation; can be over ridden by pneumotaxic center
Where is the apneustic center?
lower (ventral) pons
Where is the pneumotaxic center and what does it do?
upper (dorsal) ponsSends inhibitory impulses to the inspiratory center, terminating inspiration, and regulates inspiratory volume and RR
The descending automatic pathways (in anterolateral white matter of cord) are where…
paramedian reticular formation of the medullary and pontine tegmentum and laterally in the high cervical cord in close proximity with the spinothalamic tract
The descending voluntary pathways are where…
associated with the corticospinal tracts in brainstem and upper cervical cord
Phrenic motor neurons are where?
C3-C5
Intercostal motor neurons were where?
T2-12
Where are central chemoreceptors found?
medulla
Where are peripheral chemoreceptors found?
carotid and aortic bodies
Central chemoreceptors responsible for ___% of resp response to CO2
85%
What happens to CO2 that diffuses into brain?
Hydrated to carbonic acid –> dissociates to H+ and HCO3-; so the H+ is what actually stimulates respiration
Peripheral chemoreceptors respond to these 4 things to increase ventilation
Decreased pH, decreased PaO2, increased PaCO2, hypoperfusion
Peripheral chemoreceptors are exclusively responsible for the increased ventilation secondary to _____
hypoxemia
What is the Hering-Breuer inflation reflex?
pulmonary stretch receptors in SM respond to excessive stretch with large inspiration by sending action potentials thru large myelinated fibers of the vagus nerve to inspiratory area of medualla and apneustic center in pons; inhibits inspiratory dischargemain effect = slowing respiratory frequency by increasing expiratory time
Where are “irritant receptors” and what do they do?
Between airway epithelial cells, stimulated by noxious gases, cold, and inhaled dust; send AP via vagus causing BRONCHOCONSTRICTION AND INCREASED RR
What are “J” receptors and what do they do?
juxtacapillary receptors in alveolar walls close to capillariesrespond rapidly to chemicals in pulm circulation, distension of capillary walls, and accumulation of interstitial fluid to cause rapid, shallow breathing
How are arterial baroreceptors involved in ventilation?
Low blood pressure - hyperventilationLarge increase BP - hypoventilation
Strength of muscle contraction to inspire must overcome two main sources of impedance:
- elastic recoil of lungs and chest wall2. resistance to gas flow (upper airways)
Carbon dioxide narcosis
PaCO2 > 90mmHg
What accounts for the normal v-a CO2 difference?
10% dissolved CO2 and 90% bound CO2 in RBC as bicarbonate from tissues back to lungs
What 3 things affect venous CO2?
PaCO2, de novo tissue CO2 production, tissue blood flow
What does Henry’s law say?
The amount of dissolved gas if proportional to the partial pressure
What is oxygen capacity?
Maximum number of O2 that can combine with HbNormal is 20.8 ml O2/dL blood
What is oxygen saturation?
Percentage of available binding sites that have oxygen attached.O2 combined with Hb / O2 capacity x 100
What are the conformational changes to hemoglobin in respect to oxygenation of Hb?
R (relaxed) state with oxygenatedT (tense) state when deoxygenated
What shifts the oxygen dissociation curve to the right?
Increased temperature, 2,3-DPG, PCO2, hydrogen ionsRemember exercising muscle is hot, acidotic, hypercarbic and needs more oxygen in tissues
T/F. A right shift on the oxygen dissociation curve means the affinity of oxygen to hemoglobin is stronger.
F - means it is weaker so more O2 can be unloaded to tissues for the same given PO2
What is 2,3 DPG?
2,3-diphosphoglycerate = end product of red cell metabolism. This increased in chronic hypoxia and high altitudes. In stored RBC, 2,3-DPG reduced, so may not be that great at offloading oxygen.
A small addition of carbon monoxide to blood causes a left or right shift to O2 dissociation curve?
Left
Carbon monoxide affinity for Hb is ___ times greater than oxygen’s affinity for Hb
240Means same amt of CO with bind with Hb when partial pressure of CO is 240 times lower than oxygen’s PP
What is the Bohr effect?
The effect of pCO2 shifting curve to right because of it’s action on H+ ions
Where is carbonic anhydrase highest?
RBC
What is the chloride shift?
In the RBC, CO2 + H2O –> carbonic acid –> HCO3 and H. The bicarb diffuses out, but H can’t b/c cell membrane impermeable to + cations; so ensure a happy RBC, chloride shifts in to make it a neutral ground againGibbs-Donnan equilibrium
What is the Haldane effect?
Deoxygenated blood increases its ability to carry CO2…..why….because reduce Hb is less acidic and can take on a proton; so reduced Hb in periphery makes it easier to load CO2, and oxygenation in the lungs, makes it easier to unload CO2
How is CO2 removed from tissues?
10% dissolved, 60% HCO3, 30% carbaminoHb
Normally PETCO2 underestimates PaCO2 by __ mm Hg
2-6
What are the 3 mechanisms for oxygen induced hypercapnia in patients with chronic hypoventilation?
- Depression of formerly hypoxic-driven peripheral chemoreceptors causing worsening of hypovenilation2. Relief of hypoxic pulmonary vasoconstriction in poorly ventilated lung regions that further reduces the ability of these units to eliminate CO2 as local perfusion increases w/o increase in ventilation3. Better saturation of Hgb so that previously buffered protons on deoxyhemoglobin are released with subsequent generation of CO2 from stores (Haldane effect)
List respiratory stimulants
Doxopram, theophylline/aminophylline, caffeine, progesterone
What is orthopnea?
Extension of the head and neck while breathing
Where is 80% of the resistance to airflow during inspiration in the dog?
nose
Nasal turbinates protruding into the nasopharynx has been documented in __% of dogs with BAS, with the ___% being in Pugs.
20%, 80%
___ % of dogs with BAS has some degree of bronchoscopically detectable collapse or stenosis and that worsened degree of bronchial collapse was associated with ______ collapse.
87%, laryngeal
Esophagitis, gastritis, reflux, hiatal hernia, and pyloric stenosis reported in ____ % of dogs with BAS.
80% - worsened their resp signs
T/F. cTnI increased and CRP and haptoglobin normal in BAS dogs
T
What is the most important part of BAS surgery?
A good nose job!!! Imparts the most airway resistance.
T/F Tracheal hypoplasia and bronchial collapse means outcome worse with BAS surgical treatment.
F
What is the surgical procedure to fix a collapsed larynx?
Cricoarytenoid lateralization combined with thyroarytenoid caudolateralization (arytenoid laryngoplasty)
Which cell makes surfactant?
type 2 pneumocyte
What is the main substance of surfactant?
Dipalmitoyl phosphatidylcholine
___% of cats with nasopharyngeal disease have polyps.
28%
Traction avulsion of NP polyps in cats ass’d with ___% recurrence.
40-50%, esp if from auditory canal
If NP polyp from auditory tube or middle ear dz present, recommendation should be…
VBO
Horner’s syndrome VBO vs. traction avulsion
57% vs. 43%
Larynx accounts for ___% of resistance to airflow during nasal breathing
6
Causes of lar par
congenital denvervation, traumatic, iatrogenic, idiopathic, neoplastic, diffuse NM dz (MG and hypoT4)
Breeds associated with congenital lar par
Bouvier des Flandres, Rotties, Dalmations, Siberian Huskies (and mixes), Bull Terriers, Pyrenean Mountain Dogs, Leonbergers
T/F. Liquid phase esophagram better predicts post op aspiration than neuro status with lar par.
T
What are surgical techniques to fix lar par
- widen dorsal glottis (unilateral or bilateral arytenoid lateralization)2. widen ventral glottis (focal fold resection, partial laryngectomy, modified castellated laryngofissure)3. widen both (castellated laryngofissue and bilateral arytenoid lateralization)
Incidence of aspiration after lar par sx
8-33%
T/F. Cats with lar par are older or younger than dogs.
Older (8-16y)
Radiographs misdiagnosed the location of tracheal collapse in ___% of dogs, and failed to diagnose tracheal collapse in ___% of dogs when compared to fluorscopy.
44%, 8%
___% of dogs with cervical tracheal collapse also had concurrent bronchial collapse.
83%
Lar par diagnosed in ___% of dogs with tracheal collapse.
30% (vet surg, 1982)
Pathogens that can be cultured from normal dog lungs
Pasteurella, Staph, Strept, Klebsiella
Most common isolated bacteria from dogs with tracheal collapse.
Pseudomonas, Pasteurella, E.coli, Staph
T/F Bronchoscopic removal of trach foreign bodies has better success in cats vs dogs
F. Dogs 86%, cats 40%
Most common nasal tumors in dogs vs. cats.
Dogs - carcinoma/sarcoma, cats- LSA
Most common laryngeal tumor in dogs?
osteochondroma (usually young dogs < 2y)
Most common laryngeal tumor in cats?
LSA
Median age of laryngeal tumors?
9 y (exception, dogs osteochondroma < 2 y)
Sleep study in Bulldogs showed what?
5 bulldogs had SpO2<90% during 32% of time in REM, no control had this. Mean REM sleep SpO2 Bulldogs (78+/-5%) and controls (95 +/-2%)
What is a staphlectomy?
Resection of the soft palate
Laryngeal collapse in BDs has been correlated with the severity of ____.
Bronchial collapse.
__ % of BDs had GI abnormalites (endoscopic and biopsies)
97%
What is the Precision Flow?
Device that provides high flow (40 L/min) of humidified, warmed oxygen to help support airway patency
What was the conclusion of the NTT study in brachycephalics?
5 dogs w/o NTT oxygen developed resp distress, no dog with NTT oxygen developed resp distress; 4 dogs with NTT had to have it removed d/t vomiting, regurg, or coughing
T/F BDs have lower PaO2 and higher PaCO2
T
What kind of endotracheal tube has been assc’d with tearing of the dorsal tracheal membrane in cats?
low volume,high pressure cuffs
How much of the trachea can be resected in dogs?
20% yound dog, 25-50% older dog
What is the most appropriate way to re-anastomose tracheal rings from traumatic trachea tears in medium to large dogs?
Split cartilage technique - tracheal cartilage at the proximal and distal ends of the anastomosis is split circumferentially using an 11 blade, then prepalced sutures (8-12 of them) with 3/0 or 4/0 monofilament material around the opposite cartilage halves and thru the dorsal tracheal membrane on either side of the anastomosis; less risk of luminal stenosis than annular ligament and cartilage technique; doesn’t work in small patients
What is the most appropriate sx technique to re-anastomose the trachea in smaller animals?
cartilage technique; resect annular ligament on each side and suture the two cartilages together with preplaced suturessplit cartilage technique doesn’t work b/c cartilages fragment due to size
In cats with trach tears secondary to intubation, where was the most common site?
Thoracic inlet on the dorsolateral aspect of the trachea at the jxn of the tracheal rings and trachealis muscle
Surgical approach for an intrathoracic tracheal tear?
Right lateral thoracotomy (3rd-4th intercostal space)
Minimum volume of air in high volume, low pressure cuff to create an airtight seal in cats.
0-3 mm
Cuff pressures (measured with pressure manometer attached to endotrach cuff) should be kept within ___ and ____ mm Hg to provide sufficient seal without compromising tracheal mucosal perfusion.
20-30 mm Hg
Most common parasite to cause allergic response in canine lungs?
Toxocara canis
T/F. Strongyloides stercoralis migrates through cat lungs only, not dogs.
F - both
List 4 primary lung parasites
Paragonimus kellicotti (both)Aelurostrongylus abstrusus (cats only)Capillaria aerophila (both)Filaroides hirthi (dogs only)
What is canine allergic bronchitis (eosinophilic bronchopneumopathy)
a. Eosinophilic infiltration of lung and bronchial mucosab. Younger (3.3 +/- 2y)c. Siberian Huskies and Alaskan malamutes overrepresentedd. Prominent bronchointerstitial pattern on rads i. 40% alveolar pattern d/t secondary pneumonia ii. 26% bronchiectasise. Peripheral eosinophilia 60%f. BAL cytology i. >50% eos in 87% dogs ii. 20-50% eos in 13% dogs
What is PIE (pulm infiltrates with eos)
a. Type I hypersensitivityb. Possible stimuli: pulmonary or migrating parasites, HWD, drugs, inhaled allergensc. 65% d/t HWDd. Pulmonary parenchymal dz – signs rapid, shallow breathing, cyanosise. Rads: diffuse interstitial, bronchial, or alveolar pattern +/- hilar lymphadenopathyf. Cytology: predominance eos in airways
What are the two classes of bronchodilators?
Methylxanthines (aminophylline, theophylline)B2 agonists (albuterol, terbutalline)
What is the reflection coefficient (sigma)
relative permeability of the membrane to protein; 1 = 100% impermeable so the protein is 100% reflected
What is the filtration coefficient (K)
measure of the overall flow from the vasculature of specific tissues and is dependent on capillary surface area and hydraulic conductivity
What are the two types of pulmonary edema?
High-pressure edemaIncreased permeability edema
T/F. The filtration coefficient is reduced when increased permeability edema
F - reflection coefficient reduced, memebrane more permeable to protein
Pulmonary edema fluid is largely cleared by…
Bronchial circulation
____ % of cats with left sided CHF have no cardiac auscultable abnormalities
20
What are risk factors for ALI/ARDS (Dorothoy Russell Havemeyer)
inflammationinfectionsepsisSIRSsevere trauma (long bone fx, head injury, pulm contusion)multiple transfusionssmoke inhalationsubmersion injuryaspiration of stomach contentsingestion of drugs and toxins
What are some causes of increased permeability edema?
ALI/ARDSPTEVALIinhaled toxins (hydrocarbons)
What are causes of mixed high-pressure and increased permeability edema?
neurogenic pulmonary edema (seizure, shock, TBI)negative pressure pulmonary edema (airway obst)
Particle smaller than __ microns bypass the upper resp tract defenses and are deposited in the alveoli.
3 um
What antibiotics penetrate the lung tissue?
chloramphenicol, doxycycline, enrofloxacin, TMS, clindamycin
What are the risks/benefits or using bronchodilators to treat pneumonia?
Risks: suppress cough, worsen VQ mismatch, spread exudates to other areas of lungBenefits: increase airflow, improve mucokinetics, methylxanthings may increase speed of mucociliary transpor, inhibit degranulation of mast cells, and decrease microvascular permeability and lead; aminophylline is also a resp stimulant and increases strength of diaphragmatic contraction
How does NAC fxn as a mucolytic?
Breaks disulfide bonds in thick airway mucus; inhaled can cause bronchoconstriction in pets
Nebulizer particle size has to be < or = to…
3 microns
___ % of cats have no signs of pneumonia
36%
____% of dogs with pneumonia have concurrent predisposing disorder
36-57%
___% of cats with pneumonia cough; compared with ___% of dogs
8%, 47%
What should be done after a lung aspirate?
Place patient on aspirate side down for 30-60 min
Common bacteria in pneumonia?
Pasteurella (22-28%), E.coli (17-46%), Staph (10-16%), Strept (14-21%), Bordetella (49%, mostly puppies), anaerobic (10-20%), mycoplasma (sole inf 8%, mixed 62%)
What is the cause of an emerging a syndrome of acute, hemorrhagic, fatal pneumonia in dogs from shelters?
Strept equi subspp zooepidemicus (Lancefield Group C)
List the criteria for ALI/ARDS accoring to the Dorothy Russell Havameyer criteria.
- Acute onset2. Risk factors3. Evidence of increased transcapillary leak w/o increased pulm cap pressure pressure4. Evidence inefficient gas exchange5. Diffuse pulmonary inflammation (optional)
List the risk factors for Vet ALI and ARDS.
InflammationInfectionSepsisSIRSTrauma (long bone fx, pulmonary contusions, head trauma)Multiple transfusionsSmoke inhalationNear-drowningAspiration stomach contentsDrugs/toxins
Kelmer, JAVMA, 2009. What were the findings from the study on nasal catheter ETCO2 compared with PaCO2 in critically ill dogs?
Mean diff 3.95 +/- 4.9 w/o supplemental oxygenMean diff 6.87 +/- 6.4 w/ supplemental oxygenMean diff w/ resp disease (9+/-5) much higher than w/o resp disease (3+/-3)Good correlation (r=0.833)Cath size, ventilatory status, and outcome no sig assc’d with diff b/t ET and Pa CO2
Kogan, JAVMA, 2008. Which breed were more likely to have aspiration pneumonia?
Goldens, Cockers, English Springers, Pugs
Rice, Chest, 2007. SF ratio of <200 (ARDS)
85, 85
Rice, Chest, 2007. FS ratio of < 315 was ___ senstiive and __ specific for detecting PF < 300 (ALI)
91%, 56%
Aspiration pneumonitis can be caused by inhalation of the following…
gastric contents, freshwater, saltwater, hydrocarbons
Severity of injury after aspiration of gastric content depends on…
pH, volume, osmolality, presence of particulate matter
What percent of aspiration pneumonia cases reported to be complications of anesthesia?
5-26%
What is the most common risk factor for aspiration pneumonia?
GI disorders (60%), followed by neuro (18%), laryngeal dz (13%)
Reported survival rate after aspiration pneumonia?
77-82%
Effect of pH on severity of lung injury after aspiration?
2.4 minimal unless particulate matter present
What is the biphasic pathogenesis of acid-induced lung injury?
Initial (peaks at 1-2 h): caustic effects of acid damage bronchial and alveolar epithelium and pulm cap endothelium, stimulates substance P immunoreactive neurons involved in control of bronchial SM tone and vascular permeability. Stimulation of subP neurons induces tachykinin, peuropeptidase release, causing neurogenic inflammation, bronchoconstriction, vasodilation, and increased vascular permeability. Histologically, epithelial and endothelial degeneration, type I cell necrosis, intraalveolar hemorrhage.Second (4-6h): larger inc pulm cap permeability and protein extravasation, edema, VQ mismatch, reduced compliance, chemotactic mediates (IL-8, TNF-alpha, macrophage inflammatory protein 2) attracts neutrophils which increase ROS, proteinases, and complement proteins. Complement induced mast cell release can cause damage to contralateral lung.
T/F - Particular matter (w/o acid) aspiration causes severe pulmonary edema.
F - inflammation, no edema
Sensitivity of TTW to diagnose bacterial pneumonia.
45-70%
Thoracic trauma reported in ___ % dogs and ___% cats that sustain limb fractures from road accidents.
34-57%, 17%
What is the spalling effect in relation to pulmonary contusions?
A shearing or bursting phenomenon that occurs at gas-liquid interfaces and may disrupt the alveolus at the point of initial contact with shock wave.
What is the inertial effect in relation to pulmonary contusions?
Occurs when low-density alveolar tissue is stripped from heavier hilar structures as they accelerate at different rates resulting in both mechanical tearing and laceration of the lungs
What is the implosion effect relating to pulmonary contusions?
Rebound or overexpansion of gas bubbles after a pressure wave passes, which can lead to tearing of pulmonary parenchyma from excess distension
What does Henry’s Law say?
The amount of gas which dissolves in a unit volume of a liquid at a given temperature is directly proportional to the partial pressure of the gas in the equilibrium phaseCO2:O2 = 24:1Solubility coefficient
Rate of oxygen diffusion dependent on…
FiO2, alveolar ventilation, pulmonary capillary blood flow, oxygenation of hemoglobin
Factors that cause contraction and increase in RV pressure:
Noradrenaline, adrenalinedopamine, PGF2alpha, TXA2, histamine (H1), serotonin, angiotensin II
Factors that cause dilation and decrease RV pressure.
isoproterenol, aminophylline, ganglion blcokers, PGE1, PGI2, histamine (H2), acetylcholine, bradykinin
What causes the normal physiological shunt?
Coronary blood enters LV via thebesian veins; some bronchial artery blood enters the pulmonary veins
What can increase the A-a gradient?
Pulmonary collapse/consolidationNeoplasiaInfectionAlveolar destructionDrugsHormonesExtrapulmonary shuntingvenous admixturealveolar PAO2Cardiac outputOxygen consumpationAnemiaP50 dissociation curveAlveolar ventilation
What is the Bohr effect?
Increased CO2 produces a pH independent shift of curve to right with decreased affinity for oxygen
T/F Normal adult hemoglobin has iron in the ferrous state Fe++
TIf oxidized to Fe+++ forms metHb
How do you treat methemoglobinemia?
methylene blue
What is the Haldane effect?
Deoxy Hb is more basic than oxy Hb and accepts H+ more readilyso…reducing the PO2 and Hb saturation increases the CO2 carrying capacity of the blood
What causes reduced compliance of lungs with pleural space disease?
reduced FRC which forces lung to operate on a less compliant portion of the compliance curve
Sigrist, JVECC, 2011. Pleural space disease was significnantly associated with what type of breathing pattern?
Costoabdominal breathing (exaggerated abd component) and asynchronous breathing (outward mvmt chest and inward mvmt abd during inspiration)
Sigrist, JVECC, 2011. Asynchronous breathing was * assc’d with…in cats.
Pleural effusion and chest wall localization
Sigrist, JVECC, 2011. Inspiratory dyspnea (prolonged insp, short exp) was associated with upper airway dz in bth dogs and cats.
F - only dogs
In dogs, what muscles elevate the ribs during inspiration?
External intercostals and the internal intercartilagenous intercostal muscles
Sigrist, JVECC, 2011. Animals (dogs and cats) with pleural space disease showed predominantly ______ breathing. SE and SP for animals with pleural space dz showing an asynchronous or inverse breathing type in combination with decreased lung sounds on auscultation was ___ and ____, respectively.
asynchronous, 99%, 40%
What is the expected compensatory response in PaCO2 from metabolic acidosis?
Decrease in PaCO2 by 0.7 mm Hg per every 1 mEq/L decrease in plasma bicarb
Hypoxemia becomes the primary stimulation for ventilation when the PaO2 drops below…
50 mm Hg
Causes of hypoglycemia in animals (can cause diminished resp muscle fxn):
Excess insulin (iatrogenic, insulinoma)Severe liver dz (PSS, glycogen storage, failure)Insulinlike hormone secreting tumors (hepatic carcinoma, HSA, leiomyoma)Metabolic dz (Addisons, GH deficiency)Neonatal and juvenile hypoglycemiaToxicosis (xylitol, ethanol)SepsisPregnancy toxemiaPolycythemiaHunting dog hypoglycemia
How do you reverse nondepolarizing paralytic agents (atracurium, vecuronium, pancuronium)?
Wait - 30-45 minutes; or…give anticholinesterase (edrophoium, physostigmine, neostigmine) and an anticholinergic (atropine, glyco)
What are the 3 types of ventilator breaths?
Spontaneous: patient determines RR and TVAssisted: patient determines RR, machine sets TVControlled: machine sets RR and TV
How is PEEP helpful?
recruiting previously collapsed alveoli, preventing further alveolar collapse, reducing ventilator induced lung injury
List some differentials for patient-ventilator asynchrony.
hypoxemia, hypercapnia, pneumothorax, hyperthermia inappropriate ventilator settings, full urinary bladder or colon, inadequate depth of anesthesia
What are some indications of pneumothorax in the PPV patient?
Rapidly climbing PCO2, falling PaO2, decreased compliance
List ddx of decreases in oxygenation in the PPV patient.
Loss of O2 supply, machine or circuit malfxn, worsening of underlying lung dz, new lung dz (pneumothorax, VAP, VALI, ARDS)
List ddx of hypercapnia in the PPV patient.
- pneumothorax2. bronchoconstriction3. ET or TT obstruction4. Vent circuit issues (leak, exhale obstruction)5. Increased dead space (pulm)6. Inadequate vent settings
List endotracheal techniques
LaryngoscopicFiberoptic-assistedDigital palpationNasal intubationRetrograde intubationTransilluminationSurgical technique (cricothyroidotomy)Cricoid pressure
What is a needle cricothyroidotomy?
Pass large bore catheter thru cricothyroid membrane to supply oxygen until can get a tube in; jet ventilation indication
Complications of endotracheal intubation.
kinking of tubepressure induced tracheal necrosisbronchial intubationincreased ICPincreased IOPhypertensiontachycardia
Indications for temp trach.
UA obstructionoral/pharyngeal sxlong term ventilationremoval of tracheal FBs
How big should trach tube be?
As big as will fit in trachea, measure on lateral cervical radiograph
Describe the surgical technique for temp trach
GA, orotrach tube in place, dorsal recumbency, ventral cervical midline incision from cricoid cartilage to sternum, separate sternohyoid muscles along midline with blunt dissection and retract laterally, remove pertracheal connect tissue, transverse, vertical or box trach
What needs to be avoided for temp trach?
recurrent laryngeal and tracheal blood supply
Where do you make incision for transverse temp trach?
3-5 trach rings
How is vertical temp trach done?
vertical incision thru 2-4 trach rings
Trach tube care protocol
- Clean inner canula2. Humidify airway for 20 minutes before suctioning3. Always preoxygenate4. Sterile technique for suctioning, circular motion5. 100% O2 x 3 min after suction6. Suction 2-4 times (patient dependent)7. Replace cannula (q24h)8. Clean incision and ensure ties secure
How is cyproheptadine thought to be helpful in feline asthma?
serotonin receptor antagoist that inhibits feline airway smooth muscle contraction
Define spalling effect (pulm contusion).
lung injured directly by increase pressure, a shearing or bursting phenomenon that occurs at gas liguid interfaces and may disrupt alveolus at point of initial contact with shock waves
Define inertial effec (pulm contusion)
occurs whn low density alveolar tissue stripped from heavier hilar structures as the accelerate at different rates
Define implosion effect (pulm contusion)
Rebound or overexpansion of gas bubbles after a pressure wave passes, can lead to tearing of the pulm parenchyma fro excess distension
Angiostrongylus vasorum
middle aged dog, parasitic infection, causes hemoptysis and pulm hemorrhage
Define volutrauma
alveolar overdistension
Define barotrauma
mechanical disruption of pulmonary tissues as result of pressure
Define atelectrauma
Repetitive alveolar opening and collapse of alveoli
Difference b/t VILI and VALI
Induced vs associatedVILI based on histopath, research settingVALI clinical syndrome, live patients
Why start heparin 3-4 d before warfarin?
Avoid hypercoagulable state thru inactivation of protein C with warfarin therapy
Carboxyhemoglobin shifts OD curve to….
left
Binding affinity of CO to Hgb
240X greater than oxygen
3 possible outcomes from CO poisoning
- Complete recovery with transient hearing loss2. Recovery with permanent CNS effects3. Death
Hydrogen cyanide gas effects
nonirritant but interferes with utilization of oxygen by cellular cytochrome oxidase, causing histotoxic hypoxia
What gases can be inhaled during fire?
COShort-chain aldehydes (convert to acid in resp tract - oxides of sulfur and nitrogen)Water soluble (ammonia, HCl)benzene (from plastics)
What reduces lung compliance from smoke inhalation?
alveolar atelectasispulmonary edema
DDx for hyperemia in smoke inhalation
- carboxyHgb2. cyanide toxicosis3. systemic vasodilation4. local vasodilation from mucosal injury
Reduction in a-v oxygen gradient may be suggestive of… (in smoke inhalation)
HCN toxicity
Excessively high plasma lactate levels at admission are a sensitive indicator of ___ toxicity in humans (smoke inhalation)
HCN
The half life of CO is about ___ minutes in patients with normal respiraotry exchange on room air, but is reduced to ___ to ___ minutes with an FiO2 of 100%
250 minutes25-150 minutes
How do you treat HCN toxicity?
IV sodium nitrite followed by IV sodium THIOSULFATESodium nitrite may not be great for smoke inhalation b/c causes methemoglobinemia which will worsen O2 carrying capacity
3 mechanisms for atelectasis
compression, oxygen adsorption, depletion of surfactant
What is the primary collapsing force on the alveoli?
surface tension
What are the four opposing distending forces of the alveoli?
transpulmonary pressuretethering effect of surrounding structuressurfactantgaseous nitrogen skeleton
Why does adsorption atelectasis occur more rapidly in patients breathing oxygen enriched air?
Nitrogen skeleton is diminished or absent; the nitrogen skeleton usually provides support preventing collapse
What lung lobes are thought to be more at risk of atelectasis based on higher pleural surface to volume ratio?
right middle, left upper lobe
VAP definition
Pneumonia developed > 48 h after initiation of IPPV
Sumner, JVECC, 2011. Deep oral swabs for pneumonia….findings.
No good for puppy pneumonia, community acquired pneumonia, 40-50% agreement with hospital acquired pneumonia.
Compliance equals =
change in volume over change in pressure
What are the 4 types of PV dyssynchrony?
triggerflowcycle (breath termination)expiratory
List the 4 types of hypoxia
hypoxic, anemic, stagnant, histotoxic
Canine influenza strain
H3N8 - Greyhounds - FloridaDiagnosis difficult b/t viral shedding peaks during incubation 2-5 days, but when dogs become sick, not enough time for antibodies and viral isolation may be minimal b/c shedding decreased at this time
Sepsis and SIRS cats, JAVMA, 2011, DeClue, findings:
- Sepsis: high bands, eosinopenia, hyponatremia, hypochloremia, hypoalbuminemia, hypocalcemia, hyperbilirubinemia2. When sepsis/SIRS compared = only * diff were bands and albumin3. Cats with sepsis * higher TNF than healthy cats and more likely to have detectable IL-6 than SIRS or healthy cats4. CXCL-8 not detectable in most cats5. No diff in mortality b/t sepsis or SIRS6. Variables correlated with nonsurvival in sepsis: IL-1B, IL-6, chloride7. Cats with SIRS had higher ALP8. # SIRS criteria fulfilled not associated with outcome
DeClue, What mediators prominent in early vs. maintenance inflammatory phase?
TNF-a and IL-1B (early)IL-6 and CXCL-8 (maintenance)
SIRS criteria cats.
T103.5HR 225RR >40WBC 19.5, or >5% bands
Effect of oxyglobin in hypotensive cats, JAVMA, 2011, Wehausen.
SAP increased >80 mm Hg in 75% cats; increased >20 mm Hg above baseline in 29/33 cats, mean SAP during CRI 92
Adverse effects oxyglobin hypotensive cats, JAVMA, 2011
respiratory changes, vomiting, pigmented urine (30/33 cats)
Was NT-proBNP able to differentiate b/t CHF and nonCHF for moderate to severe pleural effusion in cats? Hassdenteufel, JVECC, 2013
Yes, cutoff 258 pmol/L
What is airway pressure release ventilation?
Open lung ventilation, high CPAP maintained and patient allowed to breath spontaneously
Most common causes of pneumomediastinum in cats (most common to least common)?JVECC, 2013
- Endotracheal intubation and PPV2. Spontaneous3. Trauma4. Tracheal FB50% had pneumothorax and pneumoretroperitoneum22% had pleural effusion
