week 7- PFTs & Pg Flashcards
• Info gained from PFT:
o air volume in and out of lungs o speed of air in and out o compliance: stiffness of lungs and chest wall o membrane/gas diffusion (special tests) o lung response to tx
• reasons for PFT:
o ssx of lung dz, progression
o Cough, dyspnea, cyanosis, wheezing, hyperventilation
o Monitor tx
o Eval preoperative pts
o Screen at risk for pulm dz
o Smokers, occupational exposure to toxic substances
• Primary lung volumes:
o VT: tidal; air inhaled during quiet breathing
o IRV: inspiratory reserve; max inhaled
o ERV: expiratory reserve; max exhaled
o RV: residual; remaining after max exhalation
• Lung capacities:
o = sum of primary lung vol
o TLC: total lung; sum of 4 primary vol
o VC: vital; vol exhaled from max insp to max exp
o FRC: functional residual; resting, end-expiratory vol
o IC: max vol inhaled from FRC
• How to do PFT/spirometry:
o Pt sits o Closed-circuit technique: o nose clip; breathe thru mouthpiece o deep breath as fast as possible o Blow out as hard as they can until you tell them to stop o Must do maximal insp and exp effort o Do 3x
• Normal size of lungs:
o Depends on age, gender, height, race
• FVC:
o Forced Vital Capacity: after max insp, max vol forcefully exhaled o N= 5L o =Total vol exhaled forcefully from TLC o majority can be exhaled in ↓3 s in N o ↑in obstructive dz
• FEV1
o Forced Expiratory Volume 1: Volume forcefully exhaled in 1s (from TLC)
o N= 3.75 L ( > 75-80% FVC)
o =rate of air flow as one exhales
o FEV1/FVC can characterize lung dz (N= 70-75%)
• Percent predicted FVC:
o Measured FVC/Normal FVC o Vary w age o > 80% (-120%) o 70-79%, Mild reduction o 50%-69%, Mod o ↓50%, Severe
• Percent predicted FEV1:
o >75%, Normal
o 60%-75%, Mild obstruction
o 50-59%, Mod
o ↓49%, Severe
• Flow-volume loop:
o max exp and insp flow-vol curves
o help characterize dz states (eg obstructive vs. restrictive)
o Obstruction: concave, scooped
o Restriction: ↓VC, normal shape
o Upper airway obstruction: cut-off insp/exp limbs
• Spirometry interpretation:
o 1: obstruction? = ↓FEV1/FVC (↓70%)
o 2: Interpret severity (FEV1)
o 3: Restriction: FEV1 and FVC ↓ in proportion (normal FEV1/FVC ratio)
o 4: Flow volume loops
• Normal, obstructive, restrictive PFT values:
o FVC: 5L, (4.9), (3.9)
o FEV1: 3.75L, 2.5, 3.5
o FEV1/FVC: 70-75%, 51%, 90%
o Prediclted FVC: 8-100%, >80%, 70%
• Obstructive lung dz:
o Can’t get air out o ↓: VC, IRV, ERV o ↑: RV, FRC, RV/TLC o ↓FEV1, ↓FEV1/FVC ratio o Obstructive ventilatory function: o Lumen of airways affected o Asthma & chronic bronchitis o FVC shows ↓flow rates and normal lung volumes, but with ↓FEV1
• Restrictive lung dz:
o ↓ lung compliance: lungs stiff, ↑P to expand lungs
o ↓: VC, RV, FRC, VT, TLC
o ↓FEV1, ↓FVC (N FEV1/FVC ratio)
o epithelial injury → interstitial fibrosis →stiff lung, dyspnea
o endothelial injury →abn ventilation-perfusion →Hypoxia, cyanosis
o Pulm HTN, cor pulmonale
• What is Diffusion capacity used for?
o to distinguish parenchymal and extraparenchymal causes of restriction
o Pulm: dzs like fibrosis
o Extraparenchymal: Obesity, neuromuscular dzs, chest wall deformities, large pleural effusions
• What is the diffusion capacity test?
o After PFTs, inhale trace amounts of CO
o →traverses alveolar capillary beds much more readily than CO2 or O2
o most CO is normally absorbed
o ↓: suggests pulmonary fibrosis
• Normal menstrual cycle:
o 28 d long, 1=1st day menses, 14= “normal” ovulation
o →ruptured ovarian follicle becomes corpus luteum
o → produces P → prepares uterus for fertilized ovum reception
o No fertilization → CL degenerates
o → menses ~14 d after ovulation
• Post-fertilization (pregnancy):
o Fertilization at fimbriae of fallopian tube
o Ciliated epithelial lining sweeps developing blastocyst to uterus, 5-7 d
o Implantation → Syncytiotrophoblast cells of fetal placenta make hCG
o → maintains function of ovarian CL during 1st 2 mos of pg
o → continued P production maintains pg
• Home Pg test kits, purpose:
o Measure Urinary hCG (human chorionic gonadotropin) o detected as low as 25IU o Max Sens: 1-4 d post MMP o Detects pg at very early stage o Earlier prenatal care
• hCG:
o glycoprotein
o a subunit identical to that of LH, FSH, TSH
o B subunits unique for each hormone
o Made within 24 hrs of blastocyst implantation, 7 d after conception
o 1-2 d after implantation, serum ↑ > 5 IU/L (+ serum Pg test)
o rise rapidly 1st few wks of pg: Serum levels higher than urine
o At 1 mo serum=urine
• How do home pg tests work?
o 1st hCG Abs bind hCG in urine, travel down stick
o 2nd hCG Abs bind complex (+)
o Further down stick: Anti-Ab bind to free Ab (-)
o Show up on paper
• Pt consultation for home pg tests:
o 1st AM voiding, has ↑HCG o Run test immediately o or store in fridge 24 hrs, at room temp o if (-), repeat in 7 d o still (-) → amenorrhea workup o If (+) → prenatal care follow-up
• Interpretation of home pg tests:
o (-): hCG not present at detectable concentrations
o (+): P
o False (-): Testing too early, Urine too dilute.
o False (+): Drugs: Antiparkinsonian, anticonvulsants, phenothiazines
o Medical Conditions: Tumors, Recent completed Pg or miscarriage
• Accuracy of home pg tests:
o 97% sens
o 95% spec
o similar to lab tests: User and technique dependent
• quant serum hCG:
o usu monoclonal Abs against B subunit of HCG
o (+) 1-2 d after implantation, or 8-9 d after conception
o double every 48 hrs in 1st tri
o higher w multiple embryos
• quant serum hCG by weeks gestation:
o serial serum hCG tests eval pg integrity o 1: 5-50 IU/L o 2: 50-500 o 3: 100-10,000 o 4: 1,080-30,000 o 6-8: 3,500-115,000 o 12: 12,000-270,000 o 13-16: Up to 200,000 o 17-40: Gradual fall to 4,000