Lecture 8 "The Respiratory System Under Stress" Flashcards
how do you calculate inspired oxygen concentration?
PIO2=0.21x(Pb-47)
what are the three main challenges to the pulmonary system at atltitude?
hypoxia
low humidity
extreme cold
what happens to hypoxic drive at altitude?
hypoxic drive only lasts for 30 minutes, then respiratory rate drops and increases again over the next few days
what is the hematological effect of being at high altitude?
polycythemia, Everest showed an increase from 13.5 to 17
what happens to the oxy-Hb dissociation curve at altitude?
alkalosis shifts the curve to the left and increased 2,3 DPG shifts it to the right, overall the curve is shifted to the left to preserve O2 loading
what happens to minute ventilation, response to hypoxia, tidal volume and PCO2 in a high altitude resident?
increased minute ventilation
decreased ventilator response
increased TV
higher PCO2
is there a genetic component to high altitude adaptation?
yes
what is the primary and secondary compensation for low O2 delivery at altitude?
primary is CO
secondary is Hgb
what happens to VO2 max at altitude, and how does this affect PCO2 and PO2?
VO2 declines as a function of altitude, causing a decrease in PCO2 and an increase in PO2
what does HAPE stand for?
high altitude pulmonary edema
what is HAPE?
extreme pulmonary hypertension due to hypoxia, that is worsened by the increased CO of exercise
how do you treat HAPE?
nifedipine (CCB)
does not work as a preventative, only a treatment
what is high altitude cerebral edema?
all people at high altitudes have some degree of this
cerebral arterioles dilate in response to hypoxia, the hydrostatic P in the arteries increases and causes fluid to leave the vasculature resulting in cerebral edema
what does ataxia mean?
the inability to coordinate voluntary muscular movements
how do you treat acute mountain sickness?
symptoms resolve with time
acetazolamide (CA inhibitor)
what happens to patient’s with respiratory disease on flights?
changes from the flight may exacerbate chronic hypoxia
when is in-flight O2 needed for patients?
SaO2 < 92% on RA
PaO2 < 50 mmHg
what is the difference between drowning, near drowning and secondary drowning?
drowning is due to asphyxia by immersion
near drowning is survival of the drowning accident leading to secondary complications
secondary drowning is due to chemical and biological changes in the lungs after near drowning accidents
what happens to venous return, pulmonary blood volume and CO on immersion?
they all increase
what happens to work of breathing on immersion?
it is increased
what four things are stimulated when water gets into the mouth?
swallowing
coughing
glottis closure
laryngospasm
what is cold shock?
a sympathetic response due to total body immersion into water < 25 degrees C
it is a potent stimulus for inhalation leading to a large gasp
what is the diving reflex?
a parasympathetic response due to cold water on the face
leads to bradycardia, vasoconstriction and apnea
what is a dry drowning?
laryngospasm continues until cardiac arrest, so there is no water in the lungs
at what level PAO2 does loss of consciousness occur?
30-45 mmHg
how do the cold shock and diving reflexes increase risk of CV complications?
they are opposing sympathetic and parasympathetic stimuli, which can lead to arrhythmias
what is ore common, cold shock or diving reflex?
cold shock
what volume of aspiration leads to impaired gas exchange?
1-3 ml/kg
what happens if a hypotonic solution like fresh water is aspirated?
it dilutes surfactant and becomes absorbed leading to alveolar collapse
absorption of the water causes hyponatremia and seizures
hemodilution is rapidly corrected by redistribution
what happens if a hypertonic solution like salt water is aspirated?
it draws fluid from the circulation to the alveoli leading to hypoxia, to make it worse it is usually exudate
what is a major determinant of outcome after a near drowning incident?
CNS injury
secondary drowning has an onset of what time after water aspiration?
within 4 hours
how many chemicals are in tobacco smoke?
over 2000
what is the name of the residuous particular matter produced by the burning of tobacco?
tar
what is the average COHb in a smoker?
2-12%
what is benzene?
a carcinogen in tobacco smoke
how do you calculate pack years?
(packs/day)*years
what are three respiratory effects of smoking?
increased airway sensitivity
increased mucous production
decreased airway diameter
what happens to the alveolar/capillary barrier function in a smoker?
it becomes much more permeable as the alveolar lining becomes disrupted
what happens to serum IgE levels in smokers?
they are increased
why is CAD common in smokers?
free radicals cause vascular endothelial damage, which accelerates atheroma
why does smoking cause sleep disturbances?
smoking releases dopamine, norepi, serotonin and Ach
how likely are women who smoke to have babies with congenital heart disease?
60% more likely than those who don’t
what are three respiratory problems common in children of smokers?
decreased lung volume
increased COHb
increased risk of asthma
how long does it take to return to non-smoker levels of surgical risk?
> 8 weeks
how much is the risk of 30 day morbidity and mortality increased in smokers?
30-100% morbidity
40% mortality
