What is the expiratory phase?

Quality
Normal breath sounds (vesicular sounds)	Inspiratory phase longer than expiratory phase, without interposed gap. Due to transmitted air turbulence.
Bronchial breathing	Harsher noises; prolonged during expiration. Heard over areas of consolidation, where sound is not filtered by alveoli.
Amphoric breath sounds (less common)	Hollow noises, heard over a large cavity. The sound is said to be like the noise of air passing over the top of a hollow jar.
Intensity
Reduced intensity (decreased air entry)	Muffled breath sounds as a result of pleural effusion, pneumonia, chronic obstructive pulmonary disease collapse, pneumothorax or a mass.
Added sounds
Wheeze (polyphonic)	Continuous sounds with a musical quality. Note when in the respiratory cycle the wheeze occurs; usually louder in expiration. Due to airway narrowing in asthma or chronic obstructive respiratory disease.
Wheeze (monophonic)	Single note, due to fixed obstruction such as a space occupying lesion.
Stridor	Unlike wheeze, stridor is inspiratory; due to upper airway obstruction
Crackles	Interrupted, non-musical sounds, often occurring due to opening of small airways. Early inspiratory crackles suggest chronic obstructive respiratory disease; whilst later or pan-inspiratory crackles suggest that the disease is limited to the alveoli.Fine crackles sound like Velcro being pulled apart, they are characteristic of pulmonary fibrosis; medium crackles are typical of left ventricular failure whilst coarse crackles indicate pools of retained secretions in conditions such as bronchiectasis.
Pleural rub	A continuous grating sound which occurs with pleurisy as the inflamed pleura rub against each other (e.g. secondary to a pulmonary infarct or pneumonia)

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The expiratory flow rate depends on both air leaving the central airways during dynamic collapse as a result of the high intrathoracic pressure and the effect of high alveolar pressure, increased during the compressive phase and maintained at a high level by the contraction of the expiratory muscles.

From: Murray and Nadel's Textbook of Respiratory Medicine (Sixth Edition), 2016

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Clinical characteristics of the patients with chronic obstructive pulmonary disease

	Mild (stage I) (n = 13)	Moderate (stage II) (n = 13)	P
Age (years)	71.2 ± 8.3	70.4 ± 8.5	0.80
Height (m)	1.636 ± 0.091	1.680 ± 0.061	0.18
Weight (kg)	61.1 ± 9.8	63.9 ± 14.1	0.56
BMI (kg/m2)	22.80 ± 3.03	22.49 ± 3.91	0.82
VC (L)	3.539 ± 0.861	3.550 ± 0.689	0.97
VC (% pred)	113.3 ± 15.8	106.1 ± 15.9	0.25
FEV1 (L)	2.158 ± 0.521	1.699 ± 0.297	0.01*
FEV1 (% pred)	97.8 ± 15.6	69.4 ± 8.7	<0.01*
FEV1/FVC (%)	61.8 ± 4.7	49.6 ± 11.1	<0.01*