Medical Archive

Introduction

Ventilation

• Scenario 1 – morbid obesity
  • ?Compliance by ?chest wall compliance & by microatelectasis
  • To compensate, ?RR & ?TV
  • ??ERV, nl RV, ?TLC, ?FEV1 

??? ??
??, COPD, Bronchiectasis

??? ??
IPF, sarcoidosis, NM disease, chest wall ??.

• Extraparenchymal lung disease
  • Chest wall disorder: FRC, RV ?? ????? ??
  • Obesity: TLC & RV? ?? ??, FRC? ?? ??
  • Neuromuscular weakness: TLC ??, FRC ??, RV ??

Gas exchange

Diffusion

Ventilation/Perfusion Heterogeneity

Pathophysiology

• Ventilatory Restriction due to Increased Elastic Recoil—Example: Idiopathic Pulmonary Fibrosis
• Ventilatory Restriction due to Chest Wall Abnormality—Example: Moderate Obesity
• Ventilatory Restriction due to Reduced Muscle Strength—Example: Myasthenia Gravis
• Airflow Obstruction due to Decreased Airway Diameter—Example: Acute Asthma
• Airflow Obstruction due to Decreased Elastic Recoil—Example: Severe Emphysema

Functional measurements

Measurement of ventilatory function

Lung volumes

Air flow
Fixed upper-airway obstruction
Eg, laryngeal edema secondary to a food allergy

Airway resistance

Respiratory muscle strength

Measurement of gas exchange

Diffusing capacity (DLco)

Diffusion from… Air sacs ? Blood /min, ??? 80~120mmHg

	Obstructive pattern	Restrictive pattern	Normal spirometry
Low DLCO	Emphysema	ILD, sarcoidosis, asbestosis, HF	Anemia Pulmonary embolism Pulmonary hypertension
Normal DLCO	Chronic bronchitis Asthma	Musculoskeletal deformity Neuromuscular disease
Increased DLCO	Asthma	Morbid obesity	Pulmonary hemorrhage Polycythemia

??
??? ?????? ??
ILD, Emphysema, Pul. HTN, anemia

??
??? ???? ??. Hemoglobin in alveoli increases DLCO
Asthma, Acute CHF, pulmonary hemorrhage, polycythemia, ARDS

Arterial blood gases

(A-a)DO2
??, ??? ???? ??. ??? 15mmHg ??. (A-a)DO2 = 150 – 1.25xPaCO2 – PaO2

# Pulse oxymetry
Oxygenated Hb? ??? ?? (SaO2). ??: PaO2? ?? (curve? ?????), Carboxy-Hb, Meth-Hb? ?? ??!