Does Tendelenburg position and sheet covering of the face affect respiratory function in cardiac patient?

The Tendelenburg position (TP) and the sterile sheet covering of the face (SCF) are two manoeuvres routinely employed to cannulate a central vein and position the Swan-Ganz catheter. The two manoeuvres however can interfere with the respiratory function, decreasing the functional residual capacity, redistributing the pulmonary blood flow and favouring the rebreathing of the expired gases [1]. In this study we evaluated the impact of the two manoeuvres on the respiratory gas exchange in the cardiac patient.

Method

We studied 50 cardiosurgical premedicated patients without respiratory disease and we divided them into 5 groups: Group A₁ = 10 elective coronary patients (CP) with left ventricular ejection fraction (LVEF) >45% supplied with O₂ 40% by a ventimask; Group A₂ = 10 CP with LVEF >45% breathing room-air; Group B₁ = 10 CP with LVEF <45% supplied with O₂ 40%; Group B₂ = 10 CP with LV EF <45% breathing room-air; Group C = 10 end stage heart disease patients with LVEF <30% undergoing heart trasplantation, supplied with O₂ 40%. Before induction of anaesthesia all patients were placed in TP (30°) and had their face completely covered by sterile sheets, to cannulate the internal jugular vein and position the Swan-Ganz catheter. The arterial blood samples to measure oxygen (PaO₂) and carbon dioxide (PaCO₂) tension were drawn: before TP and SCF (Time 1), before removing TP (with SCF) (Time 2), before removing SCF (without TP) (Time 3), 5 min after SCF removal (Time 4). Statistical analysis was performed by ANOVA test, significant for P< 0.05.

Results

The main results are reported in Table 1. There are no significant differences among the five groups in the times applied for TP and SCF.

Discussion

The analysis of our data shows that: a) the association of TP and SCF (time 1 versus time 2) caused a significant increase in PaO₂ in all patients receiving O₂ and a small and not significant decrease in patients breathing room-air; b) The removal of TP (time 2 versus time 3) caused a small increase in PaO₂ in all groups but group C who showed a significant increase in PaO₂; c) the SCF (time 1 versus time 3) induced a significant increase in PaO₂ in all patients receiving supplemental O₂ and a small and not significant increase in patients breathing room-air. We did not observe any significant change in PaCO₂ values in all groups.

We conclude that the TP and the SCF, frequently employed in anaesthesia, ICU and emergency medicine, ensure a good respiratory gas exchange in cardiac patient, even when supplemental O₂ is not supplied or LVEF is markedly reduced.

Table 1 PaO₂ and PaCO₂ values recorded at the four times