Even though human lung-cast and tissue studies have indicated that there exist variations in the alveolar size and topology [ 11 , 12 ], recent investigations have shown that these variations in alveolar topology might not significantly influence distal alveolar particle transport [ 30 ]; however, it may be significant in the upper alveolar airways [ 17 , 20 ].
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The sentences
Furthermore, recent studies indicate that the topological features of alveoli may not be significant in distal airways and sacs [ 17 , 20 ].