PFTs and Asthma Flashcards
What are the indications for PFTs?
Diagnose and classify severity of pulmonary dysfunction
Distinguish between obstructive, restrictive and mixed disease
Monitor response to therapeutic interventions and progression of disease
Determine pulmonary risk prior to surgery
What are the basic PFTs?
Airflow spirometry
Lung volumes
Diffusion capacity for lungs for CO (DLCO)
Why is sitting preferred in spirometry?
Less likelihood of syncope
What is forced vital capacity?
Deep breath in and blow the air out as fast as possible with a forced expiration–total volume of air with maximal effort
What is FEF (forced expiratory flow) 25-75%?
Airflow measurement during middle half of forced expiration (nonspecific for small airway obstruction but may be an early indicator of disease)
Why is bronchodilator testing used?
Used to test reversibility
Take 2-4 puffs with chamber and hold for 5-10 sec and then spirometry completd 15 min after
When does bronchodilator testing show reversibility?
If FEV1 increased by 12% and 200 ml
What is the methacholine challenge test?
For bronchoprovocation
Dilute solution of methacholine in nebulizer
Spirometry conducted at 30 and 90 sec
Concentration increases
Positive test: FEV1 decreased by 20% (may be false +)
What do you have to confirm was achieved with PFTs?
Volume-time curve plateaus
Expiration lasts > 6 sec
2 best efforts are within .2 L
Flow vol loops are free of artifact
What is the diffusion capacity?
Measures the ability of the lungs to transfer gas and saturate Hb (alveolar-capillary membrane)
*can be misleading if person is anemia (false reduction) and must adjust for Hb level
CO used for surrogate for O2 transfer
Technique for DLCO
Pt inhales single breath of gas with helium/CO, then expires and measurement of exhalation taken
How to infer results for DLCO
Lungs are healthy- little CO collected during exhalation
Lungs diseased- less CO diffuses into lungs so higher levels are measured in exhaled gas
Results indicating obstructive disease
TLC: increased FVC: normal RV: increased FEV1: decreased FEV1/FVC: decreased Airway narrowing, limit airflow with expiration, reduced airflow with high lung vols, inspiration probs normal
Results indicating restrictive disease
TLC: decreased FVC: decreased RV: decreased FEV1: decreased FEV1/FVC: normal or increased Reduction in lung vol, reduced lung expansion, inspiration and expiration look normal with reduced flow and vol
Types of obstructive diseases
Asthma, asthmatic bronchitis, bronchitis, COPD, cystic fibrosis, emphysema, upper airway obstruction
Types of restrictive diseases
Pulmonary fibrosis, infectious lung disease, thoracic deformities, pleural effusion, tumors, neuromuscular diseases, obesity
How to examine a flow-volume curve (step 1)
If looks normal
Is the curve scooped out (obstructive)
Is the slope increased/peaked (restrictive)
How to examine FEV-1 value and lung vols (step 2)
Normal- r/o obstruction and restriction
Decreased by more than 15-20% of predicted– obstruction
How to examine FEV1/FVC ratio (step 3)
If decreased to less than 70%–obstructive
If 70% to LLN then mild obstruction cannot be excluded so look at FEV-1 and FEF 25-75% for asthma consideration
If normal to increased–maybe restrictive
How to examine response to bronchodilator (step 4)
If FEV-1 increases by 12%/200 ml–hyperreactive, reversible airways
How often do you need to get PFTs?
After 3-6 mos of controller tx (FEV1)
Periodic assessments every 1-2 yrs
Characteristics of asthma
Chronic airway inflammation, intermittent and reversible airway obstruction, bronchial hyper-responsiveness
Sxs that might indicate asthma
Coughing (nocturnal, seasonal, specific exposures, longer than 3 wks)
Wheezing (hallmark- may be inspiration or expiration)
Maybe CP, chest pressure, dyspnea, SOB
Risk factors for asthma
Atopy, medication intolerance, food allergies, GERD, RSV, positive FH, maternal smoking, obesity
Physical exam findings
Increased AP diameter
Wheezing with prolonged expiration
Associated signs of rhinitis, sinusitis, conjunctivitis, URI, atopic dermatitis
What are signs of severe obstruction?
Tachypnea, tachycardia, tripod, accessory muscle use, pulse paradoxus
What is the aspirin-exacerabted respiratory disease triad?
Samters (sinus disease with nasal polyps, ASA sensitivity, severe asthma)
What is the atopic triad?
Atopic dermatitis, allergic rhinitis, asthma
What is the atopic march?
Atopic dermatitis, food allergy, allergic rhiniits, asthma
Spirometry results to confirm asthma
FEV1< 80%
FEV1/FVC normal or decreased relative to predicted values (70-85%)
Reversibility >12% in FEV1 with bronchodilator
What is intermittent asthma (step 1)?
Sxs <2 days/wks Nighttime awakenings: none 0-4, <2 nights/month over 5 yo Normal PFTs in between exacerbations FEV1>80% FEV1/FVC normal (>85% when 5-19) Normal activity <2 days/week SABA use to control sxs
What is mild persistent asthma (step 2)?
Sxs >2 days/wks (not daily)
Nighttime awakenings: 1-2 nights/mo when 0-4, 3-4 nights/month over 5 yo
FEV1>80%
FEV1/FVC normal (>80% when 5-19)
Minor limitation in activity
>2 days/week SABA use to control sxs (not daily)
What is moderate persistent asthma (step 3)?
Daily sxs Nighttime awakenings: 3-4x/mo when 0-4, >1/wk but not nightly over 5 yo FEV1 60-80% FEV1/FVC reduced by 5% Some activity limitations Daily SABA use to control sxs
What is severe persistent asthma (step 4)?
Sxs throughout day
Nighttime awakenings: >1x/wk when 0-4, nightly over 5 yo
FEV1 <60%
FEV1/FVC reduced by >5%
Extremely activity limited
SABA use to control sxs several times a day
Preferred tx for intermittent asthma
SABA PRN (but used in all stages PRN)
Preferred tx for mild persistent asthma
Low dose inhaled corticosteroid daily
Preferred tx for moderate persistent asthma
Medium dose inhaled corticosteroid all ages OR lose dose ICS + LABA (over 5)
Preferred tx for severe persistent asthma
Medium dose ICS and LABA (or leukotriene receptor antagonist in 0-4) OR medium dose ICS + LTRA
Preferred tx for step 5 and 6 asthma
5: High dose ICS and LABA (or LTRA ages 0-11)
6: high dose ICS and LABA (or LRTA ages 0-4) and oral steroids
* consider adding omalizumab (Xolair) for ages >12 with allergies
What are the rules of 2 for asthma?
Do you have asthma sxs more than 2x/wk?
Do you awaken with asthma sxs more than 2x/month?
Do you refill your quick relief inhaler canister more than 2x/yr?
Does your peak flow meter measure less than 2x 10 (20%) from baseline?
If YES then asthma is not under control
What is well controlled asthma?
Sx < 2days/week
Nighttime awakenings: 0-11 <1/mo, >12 <2x/mo
FEV1 >80%
FEV1/FVC: >80% (ages 5-11)
What is not well controlled asthma?
Sx > 2days/week
Nighttime awakenings: 0-4 >1x/mo, 5-11 >2x/mo, >12 <1-3x/week
FEV1 60-80%
FEV1/FVC: 75-80% (ages 5-11)
What is very poorly controlled asthma?
Sxs daily
Nighttime awakenings: 0-4 >1x/wk, 5-11 >2x/wk, >12 >4x/wk
FEV1 <60%
FEV1/FVC: <75% (ages 5-11)
What are the zones one the peak expiratory flow meter?
Green good control (>80%)
Yellow caution-SABA and Med (50-80%)
Red medical alert (<50%)
What results are seen on the ABG?
Respiratory alkalosis initially (hyperventilatory)
What is the tx for an acute asthma exacerbation?
O2
SABA/SVN (albuterol or xopenex with maybe ipratropium)
Systemic corticosteroids (prednisolone-1 mg/kg/day with max dosing based on weight)
Maybe abx, respiratory monitoring and maybe CPAP or intubation
*follow up within 1 wk
What is the goal of asthma?
Prevent persistent sxs and asthma progression with appropriate medication management (daily ICS)
