Atelectasis is a major factor in postoperative morbidity for patients undergoing cardiopulmonary surgery We evaluated the effectiveness of stacked inspiratory spirometry (STIS) in 17 patients status postcoronary artery bypass graft in a nonrandomized fashion.

Atelectasis is a major factor in postoperative morbidity for patients undergoing cardiopulmonary surgery We evaluated the effectiveness of stacked inspiratory spirometry (STIS) in 17 patients status postcoronary artery bypass graft in a nonrandomized fashion. We measured pulmonary switch as an endpoint, and compared the magnitudes before and after the STIS maneuver. Our deductions showed an 8.66 percent reduction in pulmonary switch (p<0.05). The reduction in switch was modest; however, repetitive maneuvers might be the effect in greater improvement.

B1=baseline 1; B2=baseline 2; CPAP=continuous positive airway pressure; CPT=chest physiotherapy; DBIS=deep breath incentive spirometry; SIMV=synchronized intermittent mechanical ventilation; STIS=stacked inspiratory spirometry

clew words: atelectasis; incentive spirometry; postoperative; pulmonary shunt

Atelectasis contributes significantly to postoperative morbidity and mortality in cardiothoracic patients with an incidence ranging between 40 and 90 percent[1-7] Regions of collapsed lung may follow in increased work of breathing, pneumonia, and impaired oxygenation.[8-10] Efforts to abate the incidence of and analyze atelectasis have been largely directed at sustaining inspiration at high absolute lung masss and secretion clearance.

lately Baker et al[11] found that postoperative patients using a of the present day incentive spirometry technique devised by means of Marini et al[1] were able to inspire greater bulks and maintain inspiration for longer periods of time than they could with shrewd breath incentive spirometry (DBIS). With the recent technique, patients performed stacked inspiratory spirometry (STIS) by the agency of inspiring through a one-way valve that permitted inhalation and summation of successive turns while prohibiting exhalation. Since STIS was more effective in stretching the lung (higher inspiratory volumes) and maintaining the extend (longer periods of time), Baker et al[11] reasoned that STIS might be more effective than DBIS in preventing atelectasis and hence improving gas exchange in the postoperative patient.

Our investigation assessed the effectiveness of STIS in reducing the pulmonary switch fraction in postoperative thoracic surgery patients and touchstoneed the hypothesis of Baker et al[11] that inspiratory efforts of greater duration and turn result in greater improvements in gas exchange. We chose to examine the pulmonary switch fraction as an index of atelectasis as chest radiographs will not lay open microatelectasis,[9] nor would small changes in gros atelectasis be appreciated. The correlation between pulmonary switch and atelectasis has been established according to a computer-assisted tomography study by means of Hachenberg et al.[12]

METHODS

The studious mood was performed on 17 patients status situation coronary artery bypass surgery after preoperatively obtaining written consensus for an Institutional Review Board approved protocol. After the protocol was explained preoperatively, patients had ample opportunity to practice the respiratory maneuver that was to be performed postoperatively.

The consideration was initiated in the postoperative period when the patient was capable of lifting his/her head 75 cm above the bed and inspiring a intelligent breath on command. Patients remained intubated and supported with synchronized intermittent mechanical ventilation (SIMV) at a rate of 918 [+ or -] 154 breaths for minute. To assess ability to cooperate, all patients correctly answered the following questions: (1) Is your name (correct name provided)? (2) Are you at abiding-place or in the hospital? (3) Is the canopy of heaven green? (4) Is snow hot?

nearest the [FI.sub.02] was raised to 10 and after 15 min progeny samples were withdrawn from the systemic and pulmonary arterial catheters (baseline 1 Bl) Pulmonary switch was then calculated: QS/QT=(Cc[O.sub.2]-Ca[O.sub.2])/(Cc[O.sub.2]-Cv[O.sub.2]), where Cc[Osub2] is an estimate of pulmonary capillary oxygen appease (hemoglobin [Hgb].sup.*]Sa[O.sub.2.sup.*]1.36+PA[O.sub.2.sup.*].0031), Ca[Osub.2] is arterial oxygen satisfy (Hgb.sup.*]Sa[O.sup.2.sup.*]1.36+PA[O.sub.2.sup.*].0031) and CV[O.sub.2] is mixed venous oxygen contentment ([Hgb.sup.*]SV[O.sub.2.sup.*]1.36+PVO2*-0031). Oxygen tension and saturations were determined in succession a pH/blood analyzer (Corning 178) and a co-oximeter (Instrumentation Laboratories CO-Oximeter), respectively. Ten minutes later, while still inspiring 100 percent oxygen repeated specimens were obtained and pulmonary switch was recalculated (baseline 2, B2)

Patients were then asked to inspire within a one-way valve that prohibited exhalation. Patients were encouraged to make successive inspirations and stay against the one-way valve between efforts. The one-way valve was applied until the patient petition fored to exhale, appeared agitated, or until a change in cardiac or respiratory status was noted. Specimens were then withdrawn from the systemic and pulmonary arterial catheters, within 2 to 4 min of the completion of the maneuver (STIS), and pulmonary switch was calculated. The maneuver's duration and resultant inhaled body were recorded by a hand-held put up with stopwatch and spirometer (model VM-90 Bear Ventilator Monitor), respectively.

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