The global spread of the SARS-CoV-2 virus has compelled governments and healthcare systems worldwide to implement novel regulations designed to mitigate the impact of the pandemic. These regulations also impacted healthcare systems, which underwent substantial modifications to minimize contact and prevent the further spread of the pandemic. The program utilized to assess alterations in departmental performance was the Lean Six Sigma (LSS) methodology. The study examined patients who were hospitalized in the pulmonary department of the Cardarelli hospital in Naples in 2019 (pre-pandemic) and 2020 (during the pandemic). The Mann–Whitney statistical test was employed to compare the length of stay (LOS) of patients over the two years under analysis. The analysis demonstrated a decline in the number of hospitalized patients, which nevertheless was not accompanied by a statistically significant alteration in LOS across all variables examined. This study revealed that, for the department in question, which is typically responsible for treating respiratory illnesses, the Cardarelli hospital’s pandemic response actions were conducted in accordance with a rigorous methodology, namely LSS. The outcomes allow for the illustration of the impact of these containment measures, with the objective of deriving insights that extend beyond the pandemic.