Stats/Equations Flashcards
Qp:Qs
(Ao sat - SVC sat) / (PV sat - PA sat)
PVR (woods units)
(mean PA pressure - mean LAP) / Qp
Qs:QT or % shunt
measures VQ mismatch
(PV sat - PA sat) / (PV sat - SVC sat)
Hardy Weinberg equations
p + q = 1
p^2 + 2pq + q^2 = 1
- As the prevalence increases, the PPV ______ and the NPV ______.
- As the prevalence decreases, the PPV ______ and NPV ______.
- As the prevalence increases, the PPV increases and the NPV decreases.
- As the prevalence decreases, the PPV decreases and NPV increases.
Variables!
Qualitative variables (categorical)
- nominal - no order, no magnitude (gender, blood type)
- ordinal - has order but no set magnitude (ROP, NEC)
Quantitative variables (continuous)
- interval - equal intervals but no meaningful zero (apgars, temperature)
- ratio - equal intervals with meaningful zero (birthweight, residuals)
between case-control and cohort studies, when do you use RR and when OR?
Use OR with case-control and RR with cohort
How do you increase the power (decrease type II error) of a study?
think MASS:
- increase magnitude of difference
- increase alpha
- increase sample size
- decrease std deviation
What does changing the p value do to type I and type II errors?
Increasing p value increases chance of type I error (finding a difference when there isn’t one)
Increasing p value decreases the change of type II error (not finding a difference when there is one)
KBT?
every % of fetal hemoglobin = 50 mls lost
Eg: 3 fetal cells, 100 maternal cells. 3% = 150 mls lost
polycythemia exchange transfusion?
TBV (O-E/O)
If infant’s hct drops, how do you calculate EBL?
(change in hct/avg of hcts) x TBV
eg:
If hct went from 55 -> 45 in a 2 kg kid:
10/50 x 180 = 36 mls
what is the new hct after a volume of PRBC’s are transfused?
change in hct = (vol PRBC’s x hct PRBC’s)/TBV
eg, give 15 ml/kg of PRBC’s with a hct of 60 to a 2 kg kid:
30 x 60 / 180 = hct will increase by 10
If your TV decreases from 6 mls to 3 mls, how much can you expect your CO2 to increase by?
dead space always = 2mls
So TV actually decreased 4 mls to 1 ml
CO2 will go up 4x what it was prior
Which one is prevalence, which one is incidence:
- 0.05%
- 5 cases per 10,000 children per year
- 0.05% = prevalence
- 5 cases per 10,000 children per year = incidence
incidence includes cases plus the time “in” which it happens