Alveolar ventilation (Av) allows gas to move from the lungs to blood. An adequacy of ❌ flow to the lungs is required for adequate ❌ exchange. When the capillary flow is compromised, a mismatch will occur between ❌. (I.e. even when alveolar ventilation is fine, if blood flow to the alveolar capillaries is poor the perfusion of gasses will be ❌.)
Factors that affect pulmonary capillary flow include:
- pulmonary ❌
- right ❌ dysfunction

Spirometry tests assess alveolar ventilation. A FEV/FVC (Forced Expiratory Volume (1s) & Forced Vital Capacity) ratio is usually ❌.
Peak expiratory flow rate (L/min) values of PEFR depend on size, sex and age, but typically a healthy range for adults is ❌ L/min. PEFR tends to be less ❌ to small airways disease.

Obstructive diseases (❌) reduce the expiration ability (reduce ❌ and ❌ ratio.) There is evidence of ❌.
Restrictive diseases (❌, end stages of ❌) reduce the usable capacity (reduce ❌, and ❌ FEV.)

Partial pressure of oxygen & carbon dioxide:
1. PaO2, partial pressure of oxygen in the arterial circulation
- PaO2 is dependent on ❌ O2 and ❌ pressure.
- Values ❌ typically cause symptoms.
2. PaCO2, partial pressure of CO2 in the arterial circulation
- Normal value is ❌
- It is produced by ❌ during internal respiration
- Values ❌ typically cause symptoms