respiratory failure Flashcards
1
Q
what all is measured in an ABG
A
- Oxygen tension (PaO2)
- Oxyhemoglobin saturation (SaO2)
- Carbon dioxide tension (PaCO2)
- Acidity (pH)
- Bicarbonate concentration (HCO3)
- Can also request Methemoglobin, carboxyhemoglobin and hemoglobin levels if needed
2
Q
what should be done prior to an arterial blood gas
A
assess palmar circulation with a modified allens test
3
Q
what is Arterial oxygen Saturation (SaO2)
A
the proportion of RBCs with hemoglobin bound to O2
4
Q
how is SaO2 typically measured
A
pulse oximetry
5
Q
what is normal SaO2
A
Level below 95% considered abnormal but needs to be below 89% to qualify for home O2 per Medicare guidelines
6
Q
what is the best marker of oxygenation
A
arterial oxygen tension (PaO2)
7
Q
what is arterial oxygen tension (PaO2) a measurement of?
A
unbound oxygen that is dissolved in plasma
8
Q
what is considered abnormal arterial oxygen tension (PaO2)
A
considered abnormal if les than 80mmHg but must be 55 or less to qualify for home oxygen.
9
Q
what is the best marker of adequate ventilation
A
carbon dioxide tension (PaCO2)
10
Q
what is normal PaCO2
A
Considered abnormal if above 45mmHg or below 35mmHg
11
Q
what is the strongest buffer in the body and how is it regulated
A
Bicarbonate, regulated by kidneys
12
Q
How long does it take bicarbonate to buffer blood acidity
A
3-5 days to reach full effect
13
Q
what system is used to regulate body pH
A
carbonic acid/bicarbonate buffering system
14
Q
what chemical links the respiratory and kidney pH regulating system
A
carbonic acid
15
Q
what is the A-a gradient
A
the ratio of alveolar oxygen level to arterial oxygen tension (PaO2) levels in the capillaries
16
Q
what would a normal A-a gradient suggest in a patient who is hypoxic
A
Hypoventilation
Low inspired O2
17
Q
what would a elevated A-a gradient suggest in a patient who is hypoxic
A
V/Q mismatch
Shunt
Impaired diffusion
18
Q
what are the 3 steps to interprettnig an ABG
A
- is acidemia or alkalemia present?
- is the cause respirtory (assess PaCO2)
- is the cause metabolic? (assess bicarb)
19
Q
interpret
pH = 7.32
PaCO2 = 52
HCO3 = 19
A
mixed respiratory and metabolic acidosis
20
Q
interperet
pH = 7.34
PaCO2 = 50
HCO3 = 31
A
respiratory acidosis with incomplete metabolic compinsation
21
Q
Interperet:
pH = 7.38
PaCO2 = 24
HCO3 = 19
A
metabolic acidosis with complete respiratory compensation
22
Q
Interperet:
pH = 7.46
PaCO2 = 42
HCO3 = 31
A
metabolic alkalosis with no compensation
23
Q
Interperet:
pH = 7.39
PaCO2 = 41
HCO3 = 25
A
normal blood gas
24
Q
Interperet:
pH = 7.42
PaCO2 = 51
HCO3 = 33
A
metabolic alkalosis with complete respiratory compensation
- remember the body does not over compensate so the cause is in the same direction as the blood pH
25
what are possible causes of respiratory acidosis
* Airway obstruction
* Lung disease
* Chest wall disease
* Neuromuscular disease
* Primary brain injury (ex. CVA, trauma), sleep apnea, drugs causing sedation like opioids.
26
what are possible causes of respiratory alkalosis
* Voluntary hyperventilation
* Involuntary hyperventilation (anxiety states, asthma exacerbation, CNS disease)
* Lung disease causing hyperventilation (remember back to PE lecture)
27
what are causes of metabolic acidosis
* bicarbonate loss (diarrhea, biliary drainage)
* increased acid load (lactic acidosis, Ketoacisosis, ingestion)
* impaired acid excretion (renal failure, adrenal insufficiency)
28
what is the next step ater determining that your primary disorder is metabolic acidosis
calculate the anion gap
29
what is an anion gap
measures difference between cations and anions using the formula below
I dont think we have to know the formula!
30
what does an increased anion gap suggest
the presence of anions that cannot be measured
31
what is the mnemonic used to remember the causes of anion gap in matabolic acidosis
MUD PILES
M- methanol intake
U - uremia (BUN>60)
D- diabetic ketoacidosis
P-paracetamol (tylenol)
I - Isoniazid, iron
L - Lactic acidosis
E - Ethylene glycol
S - salicylates (ASA)
32
what is the cause of non-anion gap acidosis
loss of bicarbonate or decreasd H+ excretion such as during:
- diarrhea
- renal tubular acidosis
33
what are causes of metbaolic alkalosis
* volume contration (dehydration, over diuresis)
* loss of hydrochloride (vomiting, gastric suctioning, antacid use)
* hypokalemia
34
what is acute lung injury
clinical and radiographic changes that cause respiratory failure in the critically ill patient
35
what characterizes acute lung injury
acute severe hypoxia that is not due to the heart
36
what is the most severe form of acute lung injury
ARDS
37
what is ARDS
Acute hypoxemic respiratory failure following a systemic or pulmonary insult without evidence of heart failure
38
what are some examples of causative events in ARDS
* sepsis (MC, 1/3)
* shock
* aspiration pna
* drugs/OD
* long contusion
* toxic inhalation
* multiple transfusions
* near-drowing
39
what is the pathogenesis of acute lung injury
pro-inflammatory cytokines cause damage and injury mainly at the capillary and alveolar cells
40
what is the pathological hallmark for acute lung injruy
diffuse alveolar damage
41
what is the pathology of ARDS
Lung injury causes excess fluid to accumulate in both the interstitium and alveoli which causes the following:
- Impaired gas exchange
- Decreased compliance
- Increased pulmonary arterial pressure
- decreased surfactant
42
what is the diagnostic cirteria for ARDS
* acute onset within 1 week of clinical insult
* BIL pulm infiltrates
* resp failure not explained by HF or fluid overload
* PaO2/FIO2 ratio < 300mmHg
43
How is the severity of ARDS determined
* mild - PaO2/FIO2 ratio between 200-300mmHg
* Moderate-PaO2/FIO2 ratio between 100-200mmHg
* Severe - PaO2/FIO2 ratio less than 100mmHg
44
what are clinical findings in ARDS
* rapid onset dyspnea
* SOB
* tachypnea
* intercostal retractions
* crackles on exam
* hypoxemia unresponsive to supp O2
* could see multiple organ failure
45
what does imaging show in ARDS
CXR - diffuse or patchy BIL infiltrates that rapidly progress but SPARE the costophrenic angles
- air bronchograms are seen in 80% of patients!!
46
what differential diagnosis must you exclude when a patient has ARDS
cardiogenic pulmonary edema
pneumonia
47
what is treatment for ARDS
treat underlying condition
treat secondary condition (sepsis)
supportive care
48
How do you treat hypoxemia in ARDS
* requires tracheal intubation and ventilation
* supplemental O2 required
* efforts to keep FlO2 less than 60% to avoid O2 toxicity
49
what is PEEP
positive end expiratory pressure - used to prevent alveolar collapse
50
what level of PEEP should be used
the lowest effective level
51
what can develop when administering PEEP
* Auto-PEEP can develop which can decrease venous return, reduce cardiac output and potentially cause hypotension
* barotrauma can also occur
52
how does PEEP affect outcome
Has been shown to improve hemodynamic outcomes but not shown to improve mortality
53
what other treatment is used in ARDS
* Prone positioning
* Volume controlled ventilation with Low Tidal Volume Ventilation (LTVV) – resulted in 10% reduction in mortality over standard therapy
* Strategies to decrease O2 consumption include appropriate use of sedatives, analgesics and antipyretics
54
what are the outcomes of ARDS
* Mortality ranges 30-40% and increases to 90% when associated with sepsis
* Median survival is 2 weeks
* Most survivors are left with chronic pulmonary symptoms
55
what is respiratory failure
Inability of the lungs to meet the metabolic demands of the body. This can be from failure of tissue oxygenation and/or CO2 elimination
56
what is type 1 respiratory failure
Type 1 – lungs fail to provide adequate oxygenation of the blood (PaO2 <60mmHg)
57
what causes T1 RF
Caused by diseases that interfere with O2 exchange, but ventilation is maintained
Occurs when significant intrapulmonary shunting or V/Q mismatch is present
58
what are causes of hypoxemic respiratory failure
* Decreased inspired O2 tension (↓PIO2)
* V/Q mismatch (COPD)
* Diffusion limitation (fibrosis)
* Intrapulmonary shunt
* disorder of heart, lungs, blood
59
what are possible etiologies of T1 RF if a normal CXR ois observed
COPD
Intracardiac shunt (right to left)
Pulmonary embolism
60
if there are focal infiltrates on the CXR, what is likely the etiology of hypoxemic respiratory failure (T1)
Atelectasis
Pneumonia
61
if there are diffuse infiltrates on the CXR, what is likely the etiology of hypoxemic respiratory failure (T1)
* Cardiogenic pulmonary edema
* Noncardiogenic pulmonary edema (ARDS)
* Interstitial pneumonitis or fibrosis
* Infectious (bilateral pneumonia)
62
What is the MC type of respiratory failure
type 1
63
what is type 2 respiratory failure
defect in ventilation where Hypoxemia is always present but PaCO2 is elevated >50mmHg
64
what are causes of hypercapnic respiratory failure
* respiratory center dysfunction
* drug overdose, CVA, tumor
* central hypoventilation
* neuromsucular disease (polio, spinal injury, myasthenia gravis)
* chest wall/pleural disease
* upper airway distrcution
* peripheral airway disorder
65
What is the cause of low arterial pH in type 2 LF
* sedative drug overdose
* acute muscle weakness (MG)
* severe lung disease
* acute on chronic RF
66
what is Acute on chronic respiratory failure and what causes it?
* Occurs in patients with chronic CO2 retention who acutely worsen and have rising CO2 and low pH
* Caused by respiratory muscle fatigue in some cases
67
what are s/s of hypoxemia
* dyspnea
* cyanosis
* restless/anxious
* confusion/delerium
* tachypnea, tahcycardia, HTN
* temor
68
what are s/s of hypercapnia
* dyspnea and HA
* peripheral and conjunctival hyperemia
* tachycardia, tachypnea, HTN
* impaired conciousness
* papilledema
* asterixis
69
What is the treatment for hypercapnia
* specific therapy directed toward the underlying disease (ex. abx for pna)
* respiratory supportive care to maintain adequate gas exchange
* general supportive care
70
what is the main goal in acute hypoxemic respiratory failure
ensuring adequate oxygenation!
keeping O2 sat>90% or PaO2 >60mmHg
71
what can restoring oxygenation in chronic hypercapnia patients cause (rarely)
hypoventilation.
However, oxygen therapy should never be withheld for fear of causing progressive respiratory acidosis.
72
what are the oxygen delivery methods
Nasal cannula
Nasal catheter
Simple mask
Partial rebreather mask
Non rebreather mask
Venturi mask
Oxygen tent
73
for every liter increase in O2, FiO2 increases by how much?
4%
74
what are the pros and cons of nasal cannula
pros:
- common and inexpensive
- does not interfere with eating or talking, well tolerated
cons:
- higher flow rates can dry out the nasal mucosa fast
- dependent on how much patients inhale through the nose
75
what is considered high flow vs low flow in nasal cannula
Low flow: 1-6 L/min (FiO2 of 24% to 44%)
High flow: up to 10 L/min
(note: remember room air is about 20% FiO2, so you add 4% per liter)
76
what is a nasal catheter and why is it not used very often?
* inserted through nostril with the end of catheter resting in the oropharynx
* not used because its uncomfortable
* has to be changed to the other nostril every 8 hours
77
what is a simple face mask and when is it used? when should it NOT be used?
* Has vents on both sides to allow room air to enter and exhaled CO2 to escape
* Used when increased O2 delivery is needed for short periods (less than 12 hours)
* Never use less then 5 L/min as patient may rebreathe most of their own air and become hypoxemic/hypercapnic
78
what is the delivery rate of a simple flow mask
Delivers FIO2 of 40 to 60% at flow rates of 5 L/min to 8 L/min respectively
79
what is a rebreather mask?
O2 reservoir bag that allows the patient to rebreathe the first 1/3 of exhaled air (dead space air)
80
what is the delivery rate of a partial rebreather mask?
* Delivers FiO2 of 35% to 60% at a flow rate of 6 L/min to 10 L/min respectively
* It increases FIO2 by recycling expired O2
81
what is a non rebreather mask
Mask with two one-way valves prevent the following:
- Entrance of room air during inspiration
- Retention of exhaled gases during expiration
82
what is the delivery rate for a non-rebreather mask
Delivers the highest FiO2 possible 95% at a flow rate of 10-12 L/min
83
what is a venturi mask?
A mask that mixes room air with precise amount of oxygen so you can dial in the FiO2. The size of the port and oxygen flow rate determine the FiO2
84
what is the delivery rate of a venturi mask
Delivers FiO2 varying from 24% up to 60% at flow rates of 4 L/min to 10 L/min
85
what is a face tent
Designed for patients who cannot wear a mask or nasal cannula (examples: facial surgery or trauma)
86
what are oxygen hoods?
used in infants! rigid plastic domes that enclose the infants heads
87
what is a oxygen tent?
plastic canopy that supplies humidified O2
88
what is noninvasive positive airway ventilation (NPPV)
the first line therapy in COPD patients with hypercapnic respiratory failure who can:
- Protect their own airway
- Handle their own secretions
- Tolerate the BPAP mask
Reduces intubation rates and amount of ICU stay
89
what is a Bilevel Positive Airway Pressure machine? who is it most commonly used in?
AKA a BiPAP
Delivers preset inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP)
MC used in patients with COPD, conditions causing resp muscle weakness, and obesity hypoventilation
90
what is a continuous positive airway pressure machine? who is it MC used in?
* supplies a continuous level of positive airway pressure throughout respiratory cycle
* no additional pressure above CPAP level is provided
* MC used in patients with sleep apnea or cardiogenic pulmonary edema
91
what is the caveat of a BiPAP and CPAP
patients must INITIATE each breath on most machines
92
what are indications for intubation?
* Hypoxemia despite supplemental O2
* Upper airway obstruction
* Unable to protect airway or clear secretions
* Acute hypercapnia that does not quickly respond to noninvasive ventilation (CPAP or BiPAP)
* Progressive fatigue, mental status changes, tachypnea, or use of accessory muscles
* Apneas
93
what is the preferred intubation method and why?
Orotracheal intubation is preferred since easier, faster and less traumatic than nasotracheal
94
How do you assure intubation has been properly placed?
* Auscultate the lungs to verify both lungs are being ventilated
* Position of the tip of the endotracheal tube should be positioned at the level of the aortic arch and verified by CXR
* Cuff pressure should not exceed 20mmHg to minimize tracheal injury
95
When is mechanical ventilation used and what are its beneits?
* Used for acute or chronic respiratory failure when there is insufficient oxygenation or ventilation, or both. can fully or partially replace spontaneous breathing
* benefits are:
- Improved gas exchange
- Decreased work of breathing
- More precise titration of oxygen needs
96
what are the 3 types of breaths that we learned ( we will elaborate on each of these!)
* Trigger breaths
* volume assisted breaths (VA)
* volume control breaths (VC)
97
what is a trigger breath?
* Ventilator-initiated breaths – preset respiratory rate triggered by a timer on ventilator
* Patient-initiated breaths- patient effort causes flow change which initiates the breath
98
what are volume assist breaths
* Breaths are initiated by the patient with a set inspiratory flow rate
* Inspiration is stopped when the set tidal volume was delivered
99
what are volume control breaths
* Breaths are ventilator-initiated with a set inspiratory flow rate
* Inspiration is terminated once the set tidal volume was reached
100
what are the ventilation modes? (we will go into each of these too!)
* continuous mandatory ventilation (CMV)
* Intermittent mandatory ventilation (IMV)
* Synchronized IMV (SIMV)
* pressure support ventilation mode (PSV)
101
what is continuous mandatory ventilation mode?
* Minute ventilation is determined entirely by the set respiratory rate and tidal volume
* Patient does not initiate additional breaths and does not require any patient effort
* Patient may be on heavy sedation, pharmacologic paralysis, or in a coma
102
what is intermittent mandatory ventilation mode?
* Clinician determines minimum minute ventilation by setting the respiratory rate and tidal volume
* The patient can increase the minute ventilation by spontaneously breathing addition breaths
103
what is synchronized IMV mode?
* Variation of IMV
* Ventilator breaths are synchronized with patient effort
* Support can range from full support to no support at all
* Better patient-ventilatory synchrony, preserves respiratory muscle function, greater control over level of support
104
what is pressure support ventilation mode
* Patient must trigger each breath, no set respiratory rate
* The work of breathing is inversely proportional to the pressure support level
* Useful when weaning a patient from mechanical ventilation (more comfortable mode that gives patient more control.)
105
what is positive end-expiratory pressure? (PEEP)
* added to ventialtion to prevent alveolar collapse with end expiration
106
what is the pressure used in PEEP
* Usually around a pressure 5cmH20
* With ARDS (using low tidal volume ventilation) up to 20cmH20 may be used
107
what are the potential complications of PEEP
* Decreased cardiac output
* Increased risk for barotrauma
* Possibility of impairing cerebral blood flow (d/t decreased cerebral venous outflow which causes increased intracranial pressure)
108
what are the potential complications of mechanical ventilation
* barotrauma (excessive tidal volumes, PEEP
* pneumothorax
* subcutaneous emphysema
* pneumomediastinum
* ventilator-associated pneumonia
* trauma (tracheal stenosis, vocal cord dysfunction)
109
what is the mean survival time after a lung transplant
6 years:( thats so crazy.
110
what are the MC diseases that lead to transplants
* COPD
* Idiopathic pulmonary fibrosis
* Cystic fibrosis
* Alpha-1 antitrypsin deficiency
* Idiopathic pulmonary hypertension
* Coal Worker’s Pneumoconiosis
111
what are lung transplant recipients chosen based off os
the Lung Allocation Score (LAS)
112
what are the general guidelines for lung transplant candidates
* Appropriate age (usually under age 65)
* Severe lung disease that is progressive
* Limited life expectancy because of their lung disease
* Good nutritional status and BMI less than 30
* Good support system and mentally intact
113
what are contraindications for lung transplant candidacy
* Active smoking (within the past 6 months)
* Active malignancy in last 2 years
* Drug or ETOH dependency
* Significant disease of other organs including CAD and heart failure
* Untreatable pulmonary or extrapulmonary infection
* BMI >35
* Hep B, C or HIV infection (they have become relative contraindications recently)
114
flip for fun
WHOO HOOOOO DONE WITH ONE MOREEE. plz enjoy a pic of Rhys's first UCHOCO!
