Pulmonary Mechanics Flashcards
Diaphragm function, volume, and innervation
Inspiratory
2/3 of tidal volume
Phrenic nerves (C3-5)
Inspiratory muscles
Diaphragm, ext intercostals
Accessroy (scalenes and sternocleidomastoids)
External intercostals and accessory muscles
Ext - 1/3 of inspired…intercostal nerves (T1-T11)
Accessory - scalene and sternocleidomastoid (only labor breathing)
Exp. muscles
Abdominal muscles (Rectus abdmonius, ext and internal obliques, tvs. abdominus)…T7-T12
internal intercostals
In healthy, occurs passively so exp only used during labor breathing
Elasticity efinition
Expressed by its force-length relationship…smaller slope is harder to stretch
Intrapleural pressure vs. atmospheric and how is it created
Negative with respect
Elastic recoils of lung and rib are pulling away from each other creates negative pressure…therefore expansion of the rib cage can expand the lung…think about sliding glass with water in between over each other
Pneumothorax if air enters sthe pleural space
Parietla and visceral pleura attached ot what?
Parietal - rib cage
Visceral - outside of the lung
Contributing factors of elastic properties
Elastic tissue ST PV curve of the lung Lung compliance Surfactant
ST function as an elastic property
Reduces the liquid surface to its minimum at the gas-liquid interface
Reduces the SA and V of each alveolus
Contributes more than 50% of the elastic recoil of the lung*****
Lung compliance measurement
Change in lung volume generated by each unit change of pleural pressure
Slope of the static pressure volume curve (V/P)
Abnormal compliances caused by lung dz
Decreased - pulmonary fibrosis
Increased - emphysema/COPD…some of the patients have lost smaller alveoli so its easier to expand
Atelectasis and compliance
Often caused by airway obstruction and non-obstructive complications
Also after surgical anesthesia
Lowers the compliance
PEEP (positive end expiratory pressure) can help prevent it during mechanical ventilation
Surfactant production and when
28-32 weeks by type 2 alveolar cells
Reduces ST at epithelial surface and thereby reduces work of inspiratory muscles
Hydrophilic end is near liquid while non-polar end sticks out
Major point of elastic recoil of the chest wall graph
THe lung and chest wall equal each other at FRC
Lung and rib cage run parallel to each other
Resting chest wall past 75% of TLC
Implications of changes in FRC
FRC is lung volume that is at balanced position between elastic recoils of lung and chest wall
If reduction in compliance, then smaller FRC (pulmonary fibrosis)
If increase in lung compliance, then FRC higher than normal (COPD and emphysema)…this is what causes barrel chest from over-expansion of rib cage
Airway resistance
Raw = (Pmo-Palv)/flow
Pmo is typically 0
Patterns of airflow in the airways
Large - turbulent…generally more resistance
Medium and msall - laminar
Inverse relationship between airway resistance and airwat radius…radius by facotr of 16…only for laminar flow
Total cross section area of conducting and respiratory zone
Very little change from 0-10, once you reach terminal bronchiole, increases tremendously…more branches means less frcition
Airway resistance distribution along the respiratory tract
Most resistance occurs in the conducting airways,…almost none bast terminal bronchioles (silent zone)
Influence of lung volume on airway resistance
As long volume increases, the airway resistance decreases
Bronchomotor tone funcctions (physiologic)
Airway smooth muscles
Maintains patency - during forced exp or hyperventilation…particularly important in medium and small airways wth no cartilages present in airway walls
Protects against irritants…reflex bronchoconstriction in response to inhaled irrtants mediated through sensory receptors..,minimizes penetration of irritants into lung peripher y
Cholinergic
Adrenergic
NANC factors for bronchomotor tone
Ach - M3 - ASM contraction
Epi - B2 - ASM relaxation
Nitric oxide - relaxation
Tachykinins - contraction
Catecholamines
Locally released mediators
Bronchomotor tone
Epinepthrine from the adrenal gland
Histamine and leukotrienes
PFV relationship during single breathing cycle
BS resp neurons discharge…insp muscles contract…thoracic cavity epands…pleural pressure becomes more negative…lung inflates….alveolar pressures becomes subatmospheric…air flows into the lung until alveolar pressure equals atmospheric pressure
As you expand throacic cage and therefore alveoli, the alveolar pressure falls
