Pulmonology - Med Study Flashcards
What % of predicted lung volumes on spirometry are abnormal?
< 80% predicted
>120% predicted may also be significant
What Lung Capacities are affected in restrictive lung disease?
Decreased TLC (both VC and RV are decreased)
What spirometry values suggest obstructive lung disease
FEV1/FVC is < 0.7
What is Residual volume (RV)?
unused space
What is expiratory Reserve volume (ERV)?
from full non-forced end expiration to full forced end expiration
what is tidal volume (TV)?
normal unforced ventilation
What is Inspiratory reserve volume (IRV)?
from normal unforced end-inspiration to full forced end-inspiration
Equation for Vital Capacity (VC)
VC = IRV + TV + ERV
Equation for Total Lung Capacity (TLC)
TLC = VC + RV
Equation for Inspiratory Capacity (IC)
IC = IRV + TV
total capacity available for inspiration after passive exhalation
Equation for functional residual capacity (FRC)
FRC = ERV + RV
capacity left in lungs after passive inspiration
Causes of intrathoracic & extrathroacic restrictive lung disease
intra: parenchymal disease, interstitial disease
extra: obesity, scoliosis, neuromuscular weakness
How does VQ mismatch lead to hypoxemia & what is treatment
some alveoli have more V and some more Q.
major cause in chronic lung disease
responds to 100% O2 supplementation
How does R to L shunting cause hypoxemia
perfusion of non-ventilated alveoli
causes: alveolar collapse, intraalveolar filling (pna, pulm edema), intracardiac shunt, AVM
how does decreased alveolar ventilation lead to hypoxemia? is PCO2 deranged? How?
low TV or RR
always has high PCO2
how does decreased diffusion cause hypoxemia?
doesn’t really unless exercise induced bc it takes tremendous thickening.
occurs with interstitial lung disease
PCO2 may be wnl
how does high altitude cause hypoxemia
reduced partial pressure of O2
what shifts oxyhemoglobin dissociation curve to the right (or down)
mnemonic TAP
increased Temperature
increased H+ (acidosis or inc PCO2)
increased 2,3-DPG
What happens when Hgb dissociation curve shifts right (down)?
decreased affinity for O2 –> promotes offloading
what happens when HGb dissociation curve shifts left (up)?
increased affinity for O2
how does Carbon Monoxide poisioning affect hgb dissociation curve
binds tightly to Hgb –> O2 cant bind –> already bound O2 binds tightly –> left/up shift in dissociation curve
regular pulse ox can’t differentiate
how does methemoglobin affect hgb dissociation curve
Hgb molecule oxidized from Fe2+ to Fe3+ –> cant hold onto O2 or CO2 –> regular Hgb holds O2 more tightly –> left/up shift
Clinical Presentation of methemoglobinemia & treatment
> 25%: perioral/peripheral cyanosis
35-40%: fatigue, dyspnea
60%: coma, death
remove offending agent
100% Oxygen
methylene blue
if hereditary - 1-2g/day ascorbic acid
Laryngomalacia
most common c/o stridor in newborn
laryngeal cartilage not stiff enough –> luminal narrowing –> inspiratory stridor
heard by 2 weeks of life
stridor worse with agitation, feeding, supine position
most outgrow by 12-24mo, if severe & affecting feeding or nighttime hypoxia, trim supraglottis
Dx with awake flexible laryngoscopy
vocal cord paralysis
damage to recurrent laryngeal
can be with other neuro abnormalities, after birth trauma (neck stretching), or after CT/thyroid/TEF surgery
absent or weak cry, hoarse raspy voice
aspiration risk
Dx with awake fiberoptic nasopharyngoscopy
subglottic stenosis
cause stridor & resp distress in newborn or first few months of life
common in Down’s Syndrome
can present with recurrent croup
can be acquired after intubation at any age
Dx with direct laryngoscopy or bronch
laryngeal cyst
develop from mucous secretion epithelium of supraglottic region
stridor & hoarseness
usu not congenital and 2’2 prolonged or traumatic intubation
tx; remove cyst
laryngocele
epithelium lined diverticula from laryngeal saccule (above each vocal cord that lubes the cords)
laryngeal obstruction of neck mass
excise
laryngeal atresia
failure of larynx to recanalize in 10th week gestation
usually incompatible with life
laryngeal web
abnormal development of structures in & around laryngeal inlet
present with abnormal voice, stridor, resp distress
assoc with velocardiofacial syndrome –> test for 22q11 gene deletion
Dx: direct laryngoscopy
Tx: incision or dilation
Tracheal agenesis - 3 types
type 1: proximal trachea closed, distal communicates with esophagus
type 2: bronchi meet in midline & communicate with esophagus thru fistula
type 3: absent trachea, both main bronchi communicate with esophagus separately
RDS + absent cry. suspect if unable to intubate despite visualizing larynx
tracheal stenosis
segmental, usu involves complete cartilage rings occuring anywhere along length
severe retractions + expiratory stridor
bronch, CT, or MRI to confirm
mild can observe, if symptomatic dilate or resect
Tracheomalacia/bronchomalacia
inadequate cartilagenous tone or external compression –> collapses with breathing –> expiratory stridor
usually mild but can be assoc with other things like TEF, cardiac abnormality, cervical/mediastinal masses
lobar emphysema
RDS in neonate up to 5-6 months - tachypnea, grunting, expiratory wheezing
usually LUL
diaphragm down & mediastinum to opposite side
if severe, lobectomy
Pulmonary hypoplasia
RDS, hypoxic, hypercarbic
assoc/w oligohydramnios, PROM
Congenital Pulmonary Venolobar syndrome (Scimitar syndrome)
pulm venous blood flow from all/part of R lung –> IVC just above or below diaphragm which is L to R shunt
heart failure or pulm htn
transcatheter occlusion of aortopulmonary collaterals
AVM - Hereditary Hemorrhagic telangiectasia (aka Osler Weber Rendu)
skin, mucous membrane, organ issues
epistaxis by age 20 but can come earlier
PAVM uncommon in childhood but incidence increases with age and often asymptomatic
R–>L shunting –> dyspnea, bleeding hemoptysis, exervise intolerance
risk for CVA/TIA, brain abscess
known HHT should get screening echos - positive is air bubble in systemic
Tx for symptomatic - surgery or pulm angiography
pulmonary sequestration
mass of abnormal, nonfunctioning lung tissue isolated from normal lung, fed by systemic arteries
intralobar: lower lobe (m/c posterior basal section of LLL), usually isolated & discovered in childhood/adolescence
extralobar: males, just above/below diaphragm, left side
communicates with foregut
other anomalies common (colon duplication, vertebral anomaly, diaphragm defects)
pleuritic CP out of proportion to other findings
Dx on CXR/CT. not bronchoscopy bc not connected to airway.
Bronchogenic cyst
abnormal budding of tracheal diverticulum of foregut before 16wga
m/c cyst in infancy
single, unilocular, right sided
most filled with mucous
incidental on CXR vs RDS d/t compression of airway
can get infected - fever, CP, productive cough
rupture –> pneumothorax or hemoptysis
Tx - excision
Eventration of diaphragm
marked elevation, usually congenital but can be 2’2 phrenic nerve injury
males, left sided
accessory diaphragm
rare. most often right side. can cause lung hypoplasia
surgery if symptomatic
Croup
3mo-3yo, peak 2yo
boys > girls
fall, early winter
paraflu > RSV, flu, measles, other
low pitched barking cough, inspiratory stridor, steeple sign
humidifier, steamy shower, cool air
dexamethasone or if moderate stridor at rest/moderate rtx/severe sxs use rac epi (need to observe bc can rebound)
Epiglottits
2y-5y
abrupt onset fever, sore throat, drooling, stridor, look toxic, tripod positioning
abx with anti-staph (clinda, oxacillin, cefazlin) & ceftriaxone or cefotax
airway w anesthesia or ENT
ppx with rifampin
Bacterial Tracheitis
S. aureus > paraflu, moraxella, NtHflu, anaerobes
previously healthy child <3yo with recent URI
toxic, high fever, brassy productive cough, rapid deterioration
fall, winter
Tx: nafcillin, usually need hospitalization. vanco if MRSA common in community
