Emphysema from what I understand is the permanent dilation of the alveoli.
It is considered as part of COPD or chronic obstructive pulmonary disease in which the airway is obstructed with so much sputum due to the chronic long term effect of smoking. Remember smoking stimulates the goblet cells, the mucus (sputum) producing cells in the respiratory tract. If chronic smoking irritates and stimulates the goblet cells, it releases more sputum that can cause the chronic airway obstruction, thus CHRONIC OBSTRUCTIVE PULMONARY DISEASE.
Also, long term smoking destroys the surfactants that helps alveoli to do recoiling (returning to its small size after alveolar distention). With limited recoiling of the alveoli, it allows alveoli to overdistend.
When we inhale OXYGEN enters the alveoli, and when we exhale CARBON DIOXIDE leaves the airway. Now, in emphysema airway is obstructed, thus DECREASE OXYGEN in the lung plus INCREASE CARBON DIOXIDE from the trapping of air.
Decrease Oxygen Assessment
1. Dyspnea (due to decrease oxygen in the lung)
2. Productive Cough (coughing is our body's way to remove obstruction to clear airway)
3. Hypoxemia (when there is decrease oxygen in the lung it also means less oxygen delivery to the blood)
4. Weight Loss (loss of appetite and difficulty of breathing can cause poor nutrition)
5. Hypoxia (cyanosis occurs when tissue lacks oxygen and in some cases leading to digital clubbing)
Trapping of Carbon Dioxide Assessment
1. Barrel chest (since CO2 are trapped inside the alveoli plus the alveoli lacks the surfactants, the tendency of the alveoli is to retain carbon dioxide and causes the permanent overdistention. Then imagine when the 300 million alveoli overdistends, it's enough for the the lung to overexpand, thus increase anterior posterior diameter of the lung called barrel chest)
2. Hypercapnia (increase CO2 level in the blood, since CO2 cannot be removed from the lung it causes retention in the blood. Remember CO2 is the waste product of cellular metabolism, it means when cells uses oxygen the waste produced are Co2. Thats why by diffusion tissue cells moves Co2 to the blood, then from the blood to the lungs, then exhale cO2 out. If there is airway obstruction co2 are trapped in the lung and eventually retain Co2 in the blood)
3. Respiratory Acidosis (co2 as a waste must be exhaled because it is an acid. In copd trapping can cause retention of co2 in the blood changing the pH into acidisos. And since it is a respiratory problem, thus caleed respiratiry acidosis.
I hope this can help you. This is how I understand emphysema