In ICU patients, the two findings to always consider carefully are pneumothorax and improperly positioned lines.
• Being aware of the positioning of patient is crucial for identifying pneumothoraces. For upright patients, air will collect in the non-dependent apex of the lung. For supine patients, air will often collect in the most non-dependent portion of the supine lung – the costophrenic angle with the “deep sulcus sign” (asymmetric lucency in the costophrenic angle). Semi-upright positioning is tricky, because the location of the abnormal lucency is dependent on the degree of “semi-uprightness”.
• Whenever you identify a pneumothorax, ALWAYS look for evidence of tension – an ICU emergency.
• Clues that support pneumothorax over skin fold:
o ↑ lucency in the peripheral regions and ↑ density in the central regions.
o Lung markings stop at the pneumothorax margin.
o Dense visceral pleural line at the pneumothorax margin (vs. lucent skin fold margin