LUNG FUNCTION Flashcards
2 ≠ types of disorders + characteristics of each
Restrictive Disorders:
- Characterized by reduction in lung volume (TLC, RV, FVC)
- Difficulty in taking air inside due to stiffness inside lung tissue or chest wall
- Increase elastic recoiling
- Decrease lung compliance
* ILD, pulmonary fibrosis
* Scoliosis & obesity
* Neuromuscular diseases
Obstructive Disorders:
- Characterized by a reduction in airflow (FEV1, FEV1/FVC)
- “Shortness” of breath. Difficulty in exhaling air, air remains inside lung after expiration
- Decrease elastic recoiling
- Increase lung compliance
* COPD
* Asthma
* Bronchiectasis
COPD: symptoms, diagnosis, 2 ≠ types and outcomes of each
SYMPTOMS
- Dyspnea
- Chronic cough or sputum production
- History of exposure to risk factors for disease
DIAGNOSIS
- Lung function test - X-Ray
Other common features of COPD (not diagnostic): • Hyperinflated chest
• Resting tachypnea
1) Chronic inflammation (bronchitis)
- Structural changes: airways/alveoli or both
Outcomes
- FVC (Forced Vital Capacity)
- FEV1 (Forced Expiratory Volume in 1st second) - FEV1/FVC
- SVC (Slow Vital Capacity)
- RAW (Airway Resistance)
2) Emphysema
- Destruction of gas-exchanging surfaces of lung (alveoli)
Outcomes
- Same as before
- TLC (Total Lung Capacity)
- TGV (Total Gas Volume)
- RV (Residual Volume)
- DLCO (Carbon Monoxide Lung Diffusion)
2≠ types of lung hyperinflation: characteristics + outcomes of each
Static lung hyperinflation
- During rest breathing
- Increase in end expiratory lung volume (EELV) above predicted normal value
Reset respiratory system’s relaxation volume to higher level
= result of permanent parenchymal destruction, which increases lung compliance (air trapping)
Outcomes
- TLC - TGV - RV
Dynamic hyperinflation
- Determined by variation of TIME constant for emptying
respiratory system, inspired volume & expiratory time available
Refers to increase in EELV above “static” value
- In flow-limited patients, EELV = continuous dynamic variable, which fluctuate widely depending on pre- vailing level of expiratory flow limitation & breathing pattern
Outcome
- IC
Restrictive disease description
- Decreased elastic recoilment
- Retraction force elevated
- Total lung capacity reduced (<80%)
- Reduction of maximal mobilized ventilation volume
- Reduced inspiratory reserve volume
- Thorax wall deformities with mechanical restriction: scoliosis, rib fractures, pneumothorax
- Pulmonary disorders with reduction of alveolar surface: interstitial pneumonia, lung fibrosis, sarcoidosis
- Disorders of diaphragm: paresis of nerve phrenicus
- Disorders of pleura: pleural effusion
% & characteristics of obstructive & restrictive lung diseases
- Obstructive lung diseases: FEV1 /FVC<70%
- Restrictive lung disease: TLC< 80%
FVC<80%
SPIROMETRY: purpose, duration, requirements, procedure & main variables
Purpose
- Diagnosis of disease (early) - Evolution of disease
Duration
- 10 minutes
Requirements
- Nose clip
- Chair (standardized - dizziness)
- Spirometer
- Bronchodilator (COPD vs asthma): ask this first - Motivated assessor
Procedure
- Breath quietly
- After quit expiration → full inspiration
- Expire as fast & forceful that you can (until you can’t expire) - Blow in deeply
- Affordable/ portable
Main variables
- FEV1: Forced expiratory volume in 1st second
- FVC: Forced vital capacity
- PEF: Peak expiratory flow (daily change => evolution)
At least 3 reproducible values:
For FEV1 & FVC, best 2 values should be within 5% or 150 mL
V/T-curve vs F/V curve vs absolute values vs reference values → patterns
Quality control of spirometry
Can measure 3 reproducible out of 8 measurements: • Inspiratory reserve volume
• Tidal volume
• Expiratory reserve volume
- At least 6 seconds expiratory maneuvers - End 1s end expiratory plateau (0,025L) - No coughing
- FVC difference < than
≠ between best FVC & best FEV1 <0,15L - Select best values:
- Best loop: best FVC+FEV1
Reversibility:
- Inhalation of 400mcg of salbutamol
- Repeat procedure
- Variations of : 200mL or 12% indicates positive broncodilation
BODY PLETHYSMOGRAPHY: description
- Subject in sealed small “telephone booth”
- Boyle’s law: “if temperature remains same, you can use measurements of volume of gas to find out its pressure & vice versa”
- At end of normal expiration: mouthpiece closed → Patient needs to make inspiratory effort
→ Lungs expand
→ Pressures in lungs ↓
→ Pressure in cabine ↑ (closed system)
Initial volume*pressure in box known → calculate new volume – original volume = change volume in box → change volume in chest
Lung volumes: ≠ values & variation of each during obstructive & restrictive lung disease
- RV, Residual volume
- TLC, total lung capacity
- VC, vital capacity
- VT, tidal volume
Obstructive lung disease:
- Air trapping: RV >120%
- Lung hyperinflation: FRC > 120%
- Thoracic hyperinflation: TLC >120% (visual inspection)
=> Typically COPD
Restrictive lung disease:
- TLC>70% mild restriction
- 60< TLC >69% moderate restriction
- 50 < TLC > 50% severe restriction
- 30< TLC > 40% very severe restriction
=> Combine interpretation spirometry & lung volume for diagnosis
Usually, lung volumes decreased equally When TLC is <80%
FEV1/FVC is relatively normal
FVC and (FEV1) ↓
Conditions in which measurement of lung volumes indicated
- Most of TLC in normal subjects related to FVC (VC) values
- Usefulness of lung volumes largely dependent on whether or not we need to know how large RV is
Size of lungs varies with ethnic group
Remarkable lack of data on static lung volumes in non- Caucasians
=> Lung volumes in Polynesians, Northern Indians & Pakistanis are 10% smaller than in Caucasians
DLCO acronym, description & %
A: Diffusing capacity of lungs for carbon monoxide
D: indicated in evaluation of parenchymal & non-parenchymal lung diseases in conjunction with spirometry
- Severity of obstructive & restrictive lung diseases, pulmonary vascular disease & preoperative risk assessed using DLCO
%: Diffusing capacity of lungs for carbon monoxide (DLCO) DLCO <80%= reduced
- Several causes
* DLCO <50% => reduced + desaturation during exercise
* In mmol.min−1.kPa−1.l−1
* TLCO: synonym (≠ unit: ml/min/mmHg)
Diffusing capacity of lungs for carbon monoxide (DLCO)
- DLCO <80%= reduced
- 60%< DLCO>80% mild reduction
- 40%< DLCO>60% mild reduction
- DLCO<40% severe
Mixed diseases: description & example
Obstructive & restrictive components:
- Pneumectomy in patient with COPD
- Lung cancer: Loss of lung parenchyma (restrictive), obstruction of airways (obstructive)
ASTHMA: def, description & outcomes
D = chronic disease of airways that makes breathing difficult & trigger coughing & wheezing
D : Contraction muscle surrounding airways (narrowing airways) - Accumulation of inflammatory cells (swelling + build-up mucus in airways)
Airways obstruction : During asthma attack muscles surrounding bronchial wall contract & lining of airways becomes swollen & inflamed
Outcomes
- FVC
- FEV1
- FEV1/FVC
- FEV 25%-75%
- SVC
- RAW
- Bronchial challenge test
- Broncho reversibility test
RESPIRATORY MUSCLE EFFORT: description
- Maximum inspiratory & expiratory pressures measure maximal efforts of respiratory muscles
- With inhalation effort against closed pressure manometer, maximum negative pressure generated at mouth ≈ 100 cm H2O at low lung volume
- No negative pressure can be generated at TLC so that no more air can be drawn into chest
- Maximum expiratory pressures are somewhat greater, measuring 150 to 200 cm H2O at high lung volume & falling to 0 at RV
MAXIMAL INSPIRATORY PRESSURE: description & references values
- 5 MIP maneuvers (digital equipments requires just 3) - Highest 3 within 10 cm H20
- 1 minute of rest allowed in between
- Correct sitting position (nose clip) - Demonstration of maneuver
- Quiet breathing
- Complete (quiet) exhalation
- Lips around mouthpiece
- Fast and forceful inspiration
- Highest (negative) pressure will be measured
- Computer analysis afterwards
- Check for leak!
- Inform patient: almost no airflow during maneuver
Reference values
Neuromuscular diseases
Severe COPD
Weaning for mechanical ventilation
