Seventy-one patients in intensive care were randomized for initial treatment with open suction systems or closed suction systems in a cross-over design. Pulmonary and cardiovascular physiology was assessed immediately before and after three 10-second aspirations per suction. Were analyzed the effect of each suction system on physiologic parameters while adjusting for their respective values prior to suction.

Study Participants. The sample consisted of 71 subjects, both genders, hospitalized in intensive care units. This study protocol was approved by the Research Ethics Committee of Heliopolis Hospital - Sao Paulo - Brazil.

Patients were randomized in the following way: patients hospitalized in the odd beds of ICU were aspirated initially by open suction system (OSS) and later by the closed suction system (CSS); patients hospitalized in the even beds were aspirated by CSS, initially, and subsequently by the OSS.

Cardiopulmonary measures: Eligible patients were evaluated for the presence or absence of neural stimulation to spontaneous ventilation (drive breathing). If the patients showed spontaneous respiratory movements, they were sedated to the level four of Ramsay scale. After this initial evaluation, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), heart rate (HR), respiratory rate (RR), oxygen saturation (SAT), tidal volume (Vt), peak pressure (Ppeak), plateau pressure (Pplat), positive end expiratory pressure (PEEP), and inspiratory flow (V) were measured. The HR and SAT data were collected by visualization of DX 2010 multiparameter monitor from Dixtal. SBP, DBP and MBP were obtained by a single measurement provided by the same monitor. Data of peak pressure, plateau pressure, positive end expiratory pressure, inspiratory flow and tidal volume were used to calculate compliance (C) and airway resistance (R). Data were collected before and after tracheal aspiration.

Pulmonary Suction: After the initial data were obtained, patients who were under volume-controlled ventilation mode (VCV) were submitted to the first aspiration procedure according to randomization described above. Patients who were under pressure-controlled ventilation mode (PCV) were changed to VCV mode, respecting the individual mean tidal volume, which means that the tidal volume of the patient under PCV would be used to ventilate in VCV. All patients were ventilated with a Savina (Drager) mechanical ventilator. Aspiration procedures and data collection were done by a health care professional unaware of the study regimes or objectives. After the measurement of the initial parameters, patients underwent the procedure of aspiration in an open or closed system according to the randomization described above. All patients were aspirated by a system that had not been used previously. The procedure was timed and required 10 seconds to insert and remove the aspiration catheter, with each aspiration performed three times. The outside diameter of the aspiration catheter had half the inner diameter of the endotracheal tube, and the negative pressure was adjusted between 70 and 100 mmHg. At the end of the aspiration procedure, physiological assessments were repeated. Patients were returned to nursing care and underwent the second procedure after six hours from initial aspiration.

Inclusion Criteria:

• patients over 18 years old;
• intubated with a 7.5mm endotracheal tube;
• mechanically ventilated.

Exclusion Criteria:

• upper gastrointestinal bleeding;
• hemodynamic instability;
• airway bleeding;
• previous lung diseases.