Applied Pulmonary Physiology Fisiología pulmonar aplicada Daniel Weiner, MD Division of Pulmonary Medicine Medical Director, Pulmonary Function Laboratory Children’s Hospital of Pittsburgh of UPMC

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Fisiología pulmonar aplicada

Why Applied Physiology? Physiology is the study of organ function (and dysfunction). Understanding the normal processes of the lung (airways, lung tissue, chest wall), and how these processes are perturbed, allow for: –Inferring diagnosis from symptoms –Directing treatment at the causes altering normal physiology

Outline Chest wall Cough Wheezing

Physiology of The Chest Wall The diaphragm abuts the chest wall in the “area of apposition” In infants: –Chest wall is highly compliant (primarily cartilage) –Less diaphragmatic mass –Smaller area of apposition

Physiology of the Chest Wall Elastic recoil of the lung and elastic recoil of the chest wall balance at Functional Residual Capacity (FRC, resting lung volume) –Passively determined FRC in infants would be very low (and could cause hypoxemia) –Infants therefore actively elevate their FRC by glottic closure or post- inspiratory activity of the diaphragm cw lung

Physiology of Retractions Subcostal retractions are due to contraction of a diaphragm that is already flattened by pulmonary hyperinflation

Physiology of Retractions Intercostal retractions are due to more negative than usual intrathoracic pressure being generated to inflate the lung in the presence of –decreased lung compliance, or –increased airway resistance

Chest Wall Motion Chest and abdomen usually move synchronously together during respiration Asynchronous chest wall motion can suggest either obstructive disease or diaphragm weakness Thoracoabdominal asynchrony (“belly breathing”) can be quantified

Respiratory Inductive Plethysmography Non-Invasive measurements of Tidal Breathing parameters Elastic bands around rib cage (RC) and abdomen (AB) detect changes in cross-sectional area Changes in RC and AB can be added: –RC + AB = Vt Can be calibrated absolutely (ml) with pneumotach/facemask or qualitatively

Respiratory Inductive Plethysmography

Measurements Made with RIP Tidal Volume (Vt) Respiratory Rate (f) Inspiratory and expiratory flow rates Minute Ventilation (fVt) Thoracoabdominal Phase Angle (Ф) Rapid Shallow Breathing Index (f/Vt)

Phase Angle Lissajous or Konno-Mead loops.  =sin -1 m/s Allen JL, et. al. ARRD. 1990; 141:

Respiratory Inductive Plethysmography Common Uses –Studying infant lung function (CF, BPD) –Weaning from Mechanical Ventilation –Ventilator/Patient interactions –Polysomnography –Neuromuscular Disease Drawbacks –State dependent (sleep vs awake) –Calibration issues –Normative data incomplete –Equipment/software

Application: Neuromuscular Disease

Application: Obstructive Disease

Physiology of Normal Cough Normal cough requires –inspiratory phase, increasing lung volume (60- 90% TLC) and getting air behind secretions –glottic phase, increasing intrathoracic pressure (0.2sec) –expiratory phase with high flow rate ( lpm), expelling air and secretions

cmH 2 O L/sec Subglottic pressure Flow rate 0.1 sec inspiratory phase compressive phase expulsive phase Physiology of Normal Cough

Physiology of Disordered Cough Each phase can be disrupted: –inspiratory phase: diaphragm/intercostal muscle weakness (eg muscular dystrophy), chest wall deformity (scoliosis) –glottic phase: endotracheal intubation, vocal cord paralysis/paresis –expiratory phase: abdominal muscle weakness (Prune Belly syndrome), post-operative pain

cmH 2 O L/sec Subglottic pressure Flow rate 0.1 sec Mechanical Insufflation / Exsufflation Manually Assisted Cough Breath Stacking Manual / Mechanical Insufflation Assisted Cough

Physiology of Wheezing Wheezing is a continuous musical sound of air flowing through an area of high resistance or partial obstruction Wheezing from medium sized / peripheral airways should be polyphonic (heterophonous) Wheezing from large/central airways is usually monophonic (homophonous)

Physiology of Wheezing Monophonic wheezing can be caused by: –Central airway irritation (eg aspiration) –Fixed central airway obstruction (eg tumor, foreign body) –Dynamic central airway obstruction (eg tracheomalacia)

Physiology of Wheezing Polyphonic wheezing is primarily caused by obstruction of medium sized airways due to mucus (bronchiolitis, asthma, CF, etc)

Conclusions Understanding changes in physiology of the respiratory system may allow us to determine therapy –Differentiating central vs peripheral obstruction –Understanding how to augment airway clearance –Understanding signs of hyperinflation or decreased lung compliance