However, expiratory flow changes very little. Why does dead space increase with age?ĭead space increases with age because the larger airways increase in diameter. The normal value is in the range of 130 to 180 mL and depends on the size and posture of the subject. The anatomic dead space is the gas volume contained within the conducting airways. What is anatomical dead space in the lungs? This happens when there is a lack of blood flow where the alveoli have enough air to oxygenate blood or there is a lack of air in an area where the blood flow is normal. Yadav, Web.Physiological dead space or physiological shunts, arise from a functional impairment of the lung or arteries. Reference- Short Text book of Anesthesia- A. It is approximately 300 ml in normal lungs.Ī.ANATOMIC DEAD SPACE: Volume of the conducting airways, approximately 150 mlī.PHYSIOLOGIC DEAD SPACE: The volume of the lung that does not participate in gas exchange.In normal lungs, is equal to the anatomic dead space (150 ml).

During anaesthesia FRC decreases by 15-20%.ĭEAD SPACE: It is the volume of the respiratory tract that does not participate in gas exchange. Total Lung volume- IRV+TV+ERV+RV = 5500 to 6000mlįunctional Residual Capacity( FRC)- It is the volume of gas in lungs after end expiration. Minute Volume- It is tidal volume X Respiratory rate. It is 120-170 litre/min ( normally it can be measured for 15 sec and expressed as litre/min) Maximum breathing capacity- Maximum volume of air that can be breathed/minute. Residual Volume- It is the volume of gas still present in lungs after maximal expiration. Its value is 4200 to 4500 ml ( 75-80 ml/kg).įunctional Expiratory Volume ( FEV)– It is vital capacity per time. Vital Capacity- Maximum volume of gas that can be exhaled after maximum inhalation ie, it is IRV+TV+ ERV. It is 2500 + 500= 3000 ml or 3 LĮxpiratory Reserve Volume- Maximum volume of gas that can be expired after normal expiration.

Inspiratory Capacity ( IC)- It is the maximum volume which can be inhaled from end expiratory position ie, IRV + TV. Inspiratory Reserve Volume ( IRV)- It is the maximum volume of gas which a person can inhale from end inspiratory position. Tidal Volume (TV)- Volume of gas inspired or expired in each breath during normal quiet respiration. Knowledge of these values are quite important to understand respiratory physiology, pathological basis of various respiratory illnesses and for anesthesia. Lung Volumes, Capacities and Dead Space- Definitions and Normal values.

Dead space in lungs