Выражение встречается в следующем контексте:

To compare the clinical values of bronchoscopic sputum suction and general sputum suction in respiratory failure patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) combined with sequential invasive-noninvasive mechanical ventilation at the pulmonary infection control (PIC) window (period of lower sputum production, with thinner viscosity and lighter color, and alleviated clinical signs of infection).

Заранее спасибо