Respiratory system, respiratory emergencies & ventilation Flashcards
The tidal volume for a 65^lb (29kg) dog is approximately:
a. 100–200^mL
b. 300–600^mL
c. 700–1000^mL
d. 1.5–2^L
B
Which is the most common cause of hypoxemia in cats and dogs?
a. Hypoventilation
b. Diffusion impairment
c. Ventilation/perfusion mismatch
d. Decreased fractional inspired oxygen concentrations
C
When listening to lung sounds, wheezing is indicative of what disorder?
a. Narrowed respiratory passages
b. Upper airway obstruction
c. Pulmonary edema
d. Diaphragmatic hernia
A
An increase in which of the following will stimulate ventilation?
a. pH
b. H+
c. K+
d. SpO2
B
Which of the following conditions can cause a patient to have a normal PaO2 value but have impaired delivery of oxygen to tissues?
a. IMHA
b. Pneumonia
c. Laryngeal paralysis
d. Diaphragmatic hernia
A
Which of the following is considered a lung-protective strategy in mechanical ventilation?
a. Low PEEP
b. Low tidal volume
c. Low respiratory rate
d. Low ETCO2
B
Which value represents a normal PF ratio?
a. 144
b. 217
c. 301
d. 517
D
Which of the following would be responsible for a right shift in the oxyhemoglobin dissociation curve?
a. Hypocarbia
b. Acidosis
c. Hypothermia
d. Alkalosis
B
The inequality of regional ventilation and blood flow within the lung is referred to as:
a. V/Q mismatch
b. diffusion defect
c. right-to-left shunting
d. hypoxemia
A
An effusion that has a total solids value of 2.9^g/dL would be classified as what type of effusion?
a. Transudate
b. Modified transudate
c. Exudate
d. Modified exudate
B
Which of the following can help reduce the chances of ventilator-associated pneumonia for a patient receiving mechanical ventilation?
a. Appropriate oral care
b. Decreasing PEEP
c. Lung protective tidal volumes
d. All of the above
A
Lung compliance in mechanically ventilated patients can be evaluated using which method?
a. CPAP
b. Pressure volume loop
c. PEEP
d. Flow waveform
B
Respiratory rate, tidal volume, and dead space will all determine which parameter?
a. FiO2
b. PaO2
c. PaCO2
d. A-a gradient
C
Mechanical ventilation is indicated by all of the following, except:
a. severe hypoxemia in the face of oxygen supplementation
b. severe hypercapnia despite therapy
c. excessive respiratory effort and risk of fatigue or arrest
d. severe hyperventilation
D
Barring occlusion, the endotracheal tube for a patient receiving mechanical ventilation should be changed:
a. every hour
b. every 8 hours
c. every 24 hours
d. only when signs of occlusion are present
C
Which is not a benefit of airway humidification?
a. Maintaining airway patency
b. Reduction of tracheal inflammation
c. Ability to decrease PEEP
d. Promote ciliary function
C
n which ventilator mode is the patient unable to take spontaneous breaths?
a. CMV
b. IMV
c. Manual PPV
d. SIMV
A
According to human literature, during mechanical ventilation, suction of endotracheal tubes should be performed:
a. every 4 hours
b. every 12 hours
c. every 24 hours
d. when secretions are present
D
Heat and moisture exchange filters should be replaced after:
a. 4 hours
b. 12 hours
c. 24 hours
d. 72 hours
C
During mechanical ventilation, corneal ulceration is most commonly see within the first:
a. 12 hours
b. 24 hours
c. 48 hours
d. 72 hours
D
What is the main function of the respiratory system?
Supply the body with a continuous source of gas exchange between the inspired environment and the circulatory system.
Where does gas exchange occur? How does normal gas exchange occur?
Occurs in the ‘respiratory zones’ or the alveolar-capillary membrane and occurs via passive diffusion of gasses (O2 and CO2) from an area of high concentration to low concentration.
What is the space between the lungs and the thoracic cavity called?
Pleural space
What is the purpose of the pleural space and what pressure is it normally kept at?
Lubrication as the lungs expand, it is kept usually at a negative pressure of 5cmH20.
How is a breath generated?
On inspiration air is sucked into the lungs and alveoli causing the thoracic cavity to become more negative (approx. 10cmH20) as the diaphragm flattens. On expiration the lungs and chest wall passively return to their original place and air is pushed out of the lungs.
What is tidal volume (Vt)? What is considered normal?
The volume of gas normally inspired within a given breath
Vt = Va + Vd
Normal 10-20ml/kg
What is the fuctional residual capacity (FRC)?
The volume of air that remains in the lung always or the lung will collapse.
What is minute ventilation (Ve)?
The volume of gas that is ventilated per minute
Ve = Vt X RR
Normal 150-250mL/kg
Breathing….
Is an intrinsic, automated and unconscious process that originates from the brainstem and the central pattern generator in the medulla of the brainstem controls inspiration & expiration.
The pneumotaxic centre….
Located in the upper pons and is responsible for regulating the volume and rate of ventilation. Sends inhibitory impulses to the inspiratory centre to terminate inspiration and regulates inspiratory volume and respiratory rate.
The limbic system….
Regulates breathing pattern.
Central chemoreceptors….
Respond to changes in ECF hydrogen (H+) concentrations and are located in the brain, carotid & aortic arteries. They are responsible for 85% of the respiratory response to CO2.
Increased H ions = increased ventilation (increased CO2)
Decreased H ions = decreased ventilation (decreased CO2)
Pulmonary stretch receptors….
Located in airway smooth muscles and respond when the lung is distended - brief drop in respiration/apnoea. Send action potentials through myelinated fibres of the vagus nerve to inspiratory area and apneustic centre to inhibit inspiratory discharge.
Hering-breuer reflex….
What keeps the lungs from over-inflating with inspired air.
Pulmonary stretch receptors respond to excessive stretching of the lung during large inspirations. Once activated they send action potentials through large myelinated fibres of the vagus nerve to the inspiratory area in the medulla and apneustic center of the pons. In response, the inspiratory area is inhibited directly and the apneustic center is inhibited from activating the inspiratory area. This inhibits inspiration, allowing expiration to occur.
Irritant receptors….
Located between airway epithelial cells and when stimulated cause rapid bronchoconstriction and hyperpnoea.
Normal respiration….
Air enters the lungs reaching the alveoli and O2 passively diffuses through alveolar-capillary membranes where it binds with haemoglobin (Hb) forming oxyhaemoglobin (HbO2). This displaces CO2 and aids in its secretion. Oxygenated blood is delivered to the body and CO2 is exhaled.
1 Hb can carry ____ oxygen molecules?
4
__% of O2 diffused into the cell is utilised by mitochondria during the production of ATP
80-90
____ is the major by-product of internal respiration within the cell
CO2
CO2 combines with H2O forming _________ which dissolves into _____ + _____ ions. _____ is directly affected by the ratio of these ions.
a) carbonic acid
b) H+
c) HCO3-
d) pH
CO2 + H20 < – > H2CO3 < – > HCO3- + H+
What are the 5 types of hypoxia?
- Hypoxaemic-hypoxia i.e. inadequate CaO2 due to hypoxaemia
- Hypaemic-hypoxia i.e. aneamia resulting in decreased Hb
- Stagnant/circulatory hypoxia i.e. reduced CO or poor perfusion
- Histotoxic-hypoxia i.e. O2 extraction disorder
- Metabolic hypoxia i.e. increased VO2
Carbon monoxide….
220X affinity for Hb and will bind to Hb rendering it non-functional
“carboxyhaemoglobin”
Methaemoglobin….
May result from acetominophen toxicity in cats, nitrate toxicity, phenol toxicity, sulfites and napthalene.
CO2 is ___% more soluble than O2?
20
What are the 5 general causes of hypoxaemia?
- VQ mismatch
- Low FiO2
- Diffusion impairment
- R - L shunting
- Hypoventilation
VQ mismatch….
There is inequailty between regional ventilation and blood flow within the lung (ventilation v. perfusion). The lung can be adequately perfused but inappropriately ventilated or vice versa.
Treatment to improve lung ventilation and maximise perfusion
Oxygen
- improve MV
- PEEP
- alveolar recruitment maneuvers
Cyanosis present when
Hb <5g/dL and deoxyhaemoglobin >5g/dL which is the equivalent of HbO2 dropping between 50-70%.
What can auscultating crackles indicate?
Pulmonary oedema, pneumonia, fluid in the alveoli
What may audible wheezing indicate?
Narrowed respiratory passages, obstructive diseases
Absent or muffled heart sounds indicate?
Pleural space disease, pericardial disease, pneumothorax, diaphragmatic hernia.
What may inspiratory stridor indicate?
Obstructive airway disease i.e. laryngeal paralysis, BOAS, collapsing trachea.
Inspiratory effort visualised….
likely upper airway
Expiratory effort visualised….
likely lower airway
Rapid, shallow breathing….
pleural space disease, pneumothorax
Cheyne-stokes respiratory pattern….
Brief periods of apnoea followed by brief hyperventilation.
Commonly seen in severe intracranial disease, cardiac abnormalities and hypoxaemia
Kussmal respiratory pattern….
Sustained increase in depth of respiration commonly seen in patients with significant metabolic acidosis i.e. DKA, CKD
Apneustic breathing pattern….
Deep respirations with pause at full inspiration followed by brief expiration.
Commonly seen secondary to ketamine administration in Cats, central neurological disease and TBI.
PaO2 is a good indicator of?
Oxygen status
Patient can however have normal PaO2 and have decreased DO2 i.e. anaemia, reduced CO, toxicities.
The PaO2 of a healthy patient should be?
5 X FiO2
Alveolar partial pressure of O2/Alveolar gas equation
PAO2 = FiO2 (Patm - Ph) - PaCO2/RQ
On room air @ sea level PAO2=150-PaCO2/0.8
The difference between PAO2 and PaO2 should be?
A-a gradient
PAO2 - PaO2
Normal 5-15mmHg
ARDS >30mmHg
Negative = shunting
What does a high A-a gradient indicate?
The O2 in the alveoli struggles to diffuse into the blood i.e. VQ mismatch, diffusion impairment, R-L shunting, increasing age.
- Indicates pulmonary issue for hypoxaemia
P:F ratio….
P:F = PaO2/FiO2
Indicator of inappropriate oxygenation and is reliable for any FiO2 but can be unreliable in shunting.
Normal: 500
<200 indicative of ARDS
Laryngeal paralysis….
Complete or partial failure of the aryntenoid cartilages to abduct during inspiration and adduct in expiration. It is generally idiopathic but may be due to a neuromuscular disease i.e. polyneuropathy.
Signs of laryngeal paralysis
Stridorous breathing, inspiratory effort
Narrowed laryngeal lumen, increased airway resistance
Increased WOB
Airway obstruction
Dysphonia
Gagging/retching especially after eating and drinking
Heat intolerance, hyperthermia
NCPO
What are 2 common complications of laryngeal paralysis?
Pneumonitis and aspiration pneumonia
How is laryngeal paralysis treated?
Can medically manage with anxiolytics, oxygen, active cooling and weight reduction however surgery almost always indicated and has excellent prognosis (laryngeal tie back).
Collapsing trachea….
Degeneration of the tracheal cartilage that results in increased collapsibility of the trachea, trahceal flattening and tracheal narrowing. The upper portion of the trachea collapses on inspiration and the lower portion collapses on expiration.
What breeds are at higher risk of tracheal collapse?
Miniature & toy breeds
Clinical signs of collapsing trachea
Moderate to severe respiratory distress
Inspiratory stridor
Exercise intolerance
“goose-honk”, wheezing, hacking, coughing
Orthopnoea
Syncope
What are 4 anatomical features of brachycephalic airway syndrome?
- Stenotic nares
- Everted laryngeal saccules
- Hypoplastic trachea
- elongated soft palate
Pulmonary contusions….
Damage to the pulmonary capillaries - usually after blunt force trauma - which causes haemorrhage to the alveoli and broncheoli. This impairs gas exchange due to a physical barrier a the alveolar-capillary membrane, and there is VQ mismatch and hypoxaemia.
Clinical signs and diagnosis of pulmonary contusions
Thoracic pain, coughing, haemoptysis, mild to severe dyspnoea, cyanosis, increased/crackly bronchovesicular sounds.
Diagnosis with radiographs and history of blunt force trauma (radiographic evidence may not be present until 36h after event).
How are pulmonary contusions treated?
Supportive - oxygen, fluids, analgesia, decreased WOB (encourage rest).
- Diuretics, AB’s and corticosteroids unlikely to be beneficial
Feline asthma….
Hypersensitivity reaction characterised by bronchoconstriction, eosinophilic airway inflammation and airway oedema. It can range from mild to severe and is diagnosed via airway imaging. Reoccurrence is common.
How is feline asthma treated?
Environmental modification, corticosteroids (terbutaline, aminophylline, dexamethasone/prednisone).
Pneumonia….
Inflammation of the pulmonary parenchyma that results in exudate infiltration of the alveoli secondary to infection. Bacterial pathogens are the #1 cause but other pathogens such as viruses, fungi, parasites and protozoa may also induce.
Pneumonitis….
Inflammation of the pulmonary parenchyma that has no infectious cause and usually occurs secondary to aspiration of gastric contents, chemical irritants and smoke inhalation.
Clinical signs of pneumonia & pneumonitis
Lethargy
Moist cough
Tracheal irritation
Anorexia/Inappetant
Dehydration
Hypoxaemia
Increased, decreased or absent bronchovesicular sounds
+- pyrexia
Dyspnoea (often rapid, shallow)
Treatment for pneumonia & pneumonitis
Oxygen therapy
Antimicrobials
IVFT
Nebulisation +- coupage
Regular walks (facilitate in loosening secretions)
ARDS….
Acute, diffuse inflammation lung injury that leads to increased pulmonary vascular permeability, increased lung weight and loss of aerated lung tissue with hypoxaemia and bilateral radiographic opacities. It can be induced directly by the lungs or occur secondary to systemic diseases (pancreatitis, TRALI, severe burns, TBI).
Criteria for ARDS
- Must be acute onset
- Bilateral opacities consistent with pulmonary oedema
- P:F <300
- Signs cannot be attributed to cardiac failure or fluid overload.
ARDS most often occurs whilst a patient is hospitalised
Mild, moderate, severe ARDS
Mild 200-300
Moderate 100-200
Severe <100
Clinical signs of ARDS
Bilateral increased bronchovesicular sounds
Increased respiratory rate & effort
Severe dyspnoea
Cough
Cyanosis
Profound hypoxaemia
Treatment of ARDS
Oxygen - HFNO, ventilation (lung protective), CPAP
IVFT
Neuromuscular blockers (ventilated patients)
- corticosteroids, diuretics & bronchodilators not recommended
Pneumothorax….
Accumulation of air in the pleural space in a sufficient quantity that increases pressure within the pleural space impeding the ability of the lungs to expand, and participate in gas exchange.
Clinical signs of pneumothorax
Dyspnoea
Decreased/absent lung sounds
Rapid, shallow ‘restrictive’ breathing
Hypoxaemia
Treatment of pneumothorax
Oxygen
Thoracocentesis
Analgesia, anxiolysis
Chest tube placement
Immediate sterile dressing is open-pneumothorax
Surgery
Pleural effusion….
Accumulation of fluid in the pleural space and it occurs when the rate of fluid accumulation exceeds the rate of fluid absorption. This leads to an increase in pleural space pressure, inability of the lung to expand which impairs oxygenation and ventilation.
- Haemothorax
- Chylothorax
- Pyothorax
Causes of pleural effusion
Neoplasia
Hypoalbuminaemia
RHS and/or LHS heart failure
Infection
Coagulopathy
Diaphragmatic hernia
Lung lobe torsion
Clinical signs of pleural effusion
Restrictive breathing pattern
Respiratory distress
Anorexia
Muffled heart/lung sounds
Lethargy
Exercise intolerance
Treatment of pleural effusion
Thoracocentesis
Chest drain placement
Surgery
Anxiolysis
Pain relief
Oxygen
Treat underlying cause
Antibiotics where indicated
Diet alteration
Pure transudate….
Low protein <2.5g/dL
Low cell count <1000cells/uL
Due to low oncotic pressure i.e. low albumin