Correlation between breath-holding time and hand-held portable Contec™ spirometer parameters in pre-operative pulmonary function assessment: A prospective observational study. - Bora, Hemalatha; Jonnavithula, Nirmala; Geetha, Singam; Kumar, Damera Seshi; Lakkam, Krupakar; Rao, Nageswar (Journal of Clinical & Scientific Research, 2025)