The earliest signs of IPA were nidal and interstitial hyperchromogenic changes of tissues, revealed by bioplasm 9d nls analyzer-study in 75% and 67% of cases correspondingly. Roentgenography turned out to be less informative during the initial stage. Frequency of nidal and interstitial changes revealing according to roentgenography data was statistically reliably lesser – 19% and 42% correspondingly. Foci of alveolar infiltration were revealed in a significantly lesser percentage of cases according to both methods.

Nidal changes of pulmonary tissue during the second period of time (4th – 8th day) were revealed less frequently than during the first period of time. Frequency of interstitial changes areas revealing was also lesser. Foci had different shapes, more often roundish, homogeneous structure, were of subpleural location and had a connection with vessels.