Pulmonary Flashcards
Can esmolol be given to patients with asthma?
Yes, it has little effect on bronchial smooth muscle in low doses (non-specific beta blockers like metoprolol and labetolol should be avoided)
What is a normal V/Q ratio?
alveolar ventilation: 4L/min
pulmonary blood flor: 5L/min
V/Q ratio: 0.8
What are the ABG findings during an asthma attack?
always hypoxemia
early hypocarbia and respiratory alkalosis
late hypercarbia and respiratory acidosis (intubate)
Which pulmonary function test is independent of patient effort?
FEF25%-75%
What is normal tidal volume? Vital capacity? FRC? TLC?
tidal volume: 6-8 mL/kg
vital capacity: 10x tidal volume
FRC: 30-40 mL/kg
TLC: 5-6L in men, 4-5L in women
Which part of the flow-volume loop is affected by a variable extrathoracic obstruction? Intrathoracic?
Variable extrathoracic obstructions flatten the ispiratory limb
Variable intrathoracic obstruction flatten the expiratory limb
**fixed obstructions flatten both limbs**
What factors increase closing capacity?
increased age
small airway disease
smoking
How long should elective surgery be delayed for a URI?
controversial, 2 weeks after symptom resolution is reasonable
Who should get stress-dose steroids intra-operatively?
Patients with 2 weeks of systemic steroids over the past 6 months.
BUT
Reasonable to treat unexplained perioperative hypotension empirically
Should patients with severe asthma get pre-operative steroids?
a 5-day course of methyprednisolone is effective in reducing post-intubation bronchospasm
Should patients with asthma get IV lidocaine prior to intbuation?
No, it may cause paradoxical bronchospasm
Why shouldn’t nitrous oxide be given to patients with pulmonary HTN?
It can increase PVR
Which inhalational agents should be used for patients with reactive airway disease?
at > 1 MAC, sevoflurane is slightly superior to isoflurane as a bronchodilator
desflurane increases airway resistance and should not be used
Can succinylcholine be used in asthmatic patients?
Yes, the degree of histamine release is minimal and not associated with increased airway resistance
How do you calculate auto-PEEP on the ventilator?
airway pressure during expiratory hold - set PEEP
Describe the management of an acute increase in peak airway pressure intra-operatively.
increase depth of anesthesia
suction and check position of ETT
given beta agonists, ketamine, epinephrine
switch to an ICU vent (higher inspriatory pressures)
Heliox
V-V ECMO
What are the considerations for reversal of muscle relaxation in an asthmatic patient?
Neostigmine can cause bronchoconstriction
Try to avoid reversal or use higher doses of glycopyrrolate/atropine
What analgesic presents problems for asthmatic patients?
morphine - histamine release
NSAIDs - increased leukotrienes
Why does oxygen supplementation in patients with COPD lead to hypercarbia?
1) smaller tidal volumes
2) disruption of hypoxic pulmonary vasoconstriction
Where should the pulse oximeter be placed during mediastinoscopy?
On the right hand, to detect compression of the innominate artery
Where should the IV be placed during mediastinoscopy?
Upper extremity IVs are fine, but there should be a plan for lower extremity IV access in case of SVC hemorrhage
What are the advantages and disadvantages of a bronchial blocker?
Advantages:
can be used in patients too small for a DLT
can be used through a single-lumen tube (difficult airway, no need for exchange at end of case)
DIsadvantages:
unable to suction through
unable to apply CPAP through
difficult to position and maintain position
tracheal occlusion if dislodged
What are the wavelengths used for pulse oximetry?
660 nm: max absorption by deoxyhemoglobin
940 nm: max absorption by oxyhemoglobin
**Plethysmography allows sampling only arterial blood**
What is the timing of hypoxic pulmonary vasoconstriction during one-lung ventilation?
begins in 15 minutes
completes in 2 hours
reverts to normal several hours after OLV
What is the normal distribution of blood flow between R and L? Dependent and non-dependent? With one-lung ventilation?
baseline: 55% to R, 45% to L
in lateral decubitus position: 60% to dependent lung, 40% to non-dependent lung
with OLV: 80% to dependent lung, 20% to non-dependent lung
How should ipsilateral shoulder pain be treated after lung resection?
NSAIDs effective
opioids ineffective
brachial plexus blocks possible, but may paralyze diaphragm
What are the sequelae of aspiration?
obstruction
pneumonitis
pneumonia
What amount/quality of fluid qualifies as aspiration?
25 mL
pH < 2.5
What should NOT be done after aspiration?
NIPPV
lavage
steroids
antibiotics (not until evidence of infection)
What conditions have the best evidence for use of NIPPV?
cardiogenic pulmonary edema
OSA
COPD
What are the Berlin criteria for ARDS?
1) worsening respiratory symptoms
2) bilateral lung infiltrates not explained by cardiac causes
3) PaO2/FiO2 ratio:
mild 200-300
moderate 100-200
severe < 100
What kinds of trauma are being avoided with ARDSnet ventilation strategies?
volutrauma
barotrauma
atelectrauma
What are the principles of ARDSnet ventilation strategies?
low tidal volume: 6 mL/kg
Pplat < 30 mmHg
permissive hypercapnea
SaO2 > 88%
What are the last resorts for severe ARDS?
prone positioning
inhaled nitric oxide
HFOV or APRV
V-V ECMO
What are the principles of induction for patients undergoing lung transplant?
avoid abrupt withdrawal of sympathetic tone
prolonged pre-oxygenation time
volatile agents to promote bronchodilatation
What are the considerations for ventilation in patients undergoing lung transplant?
left-sided DLT
avoid air-trapping with increased expiratory time
balance ventilation and venous return
toleration of hypercapnea
What problems are associated with lateral positioning during lung transplant?
diminished venous return
compression of the dependent lung
elevated PA pressure
What are the critical points of a lung transplant procedure?
induction
lateral positioning
commencement of one-lung ventilation
PA clamping
graft reperfusion
How do you evaluate and treat cardiac function during PA clampling?
evaluate RV response on TEE
attempt pulmonary vasodilators
may require CPB
What can cause hypotension after pulmonary graft reperfusion?
wash-out of vasodilating preservatives
coronary air embolus from incomplete de-airing
What happens to PA pressure after pulmonary graft reperfusion?
it should fall
if it does not, you must reassess the anastomosis and consider eary graft dysfunction
What is the alveolar gas equation?
PAO2 = FiO2 (Patm - pH2O) - PaCO2/0.8
Patm ~ 760 mmHg
pH2O ~ 47 mmHg
What is the oxygen content equation?
CaO2 = (SaO2 x Hgb x 1.34) + (0.003 x PaO2)
** mL of O2 per 100 mL blood **
What happens to PaCO2 during apneic oxygenation?
increases by 6 mmHg in the first minute and 3 mmHg in each subsequent minute
What is the Winter’s formula?
Estimates the respiratory compensation for a metabolic acidosis:
expected PaCO2 = (1.5 x HCO3-) + 8
How much does pH change based on PaCO2?
pH changes by 0.08 for every 10 mmHg change in PaCO2
