The aim of the study was to compare the effects of hyperventilation on haemodynamics and partial pressure of carbon dioxide and acid base status with three different respiratory rates and tidal volume of 10 ml /kg .

Methods: 90 patients undergoing laparoscopic surgeries under General Anaesthesia were randomized into three groups, with tidal volume of 10 ml/kg and respiratory rate of 12,14,16 per  minute. Hemodynamic variables (heart rate and mean arterial pressure) were recorded and End tidal C02, PaC02, pH and Bicarbonate estimation done before, during and after C02 pneumoperitoneum.

Results: The three groups were similar in demographic profile.There were no significant difference in mean arterial pressure before creation of pneumoperitoneum in all three groups. (p value 0.067). Arterial blood gas analysis demonstrated higher PaCO2 and lower pH in control group than in study group. PaCO2 values measured before pneumoperitoneum showed a higher value in group 1 whereas  it was lower in normal range in groups 2 and 3 .The values were 34.92 mm of Hg and 33.13 mm of Hg respectively and  statistically significant (p value is 0.0000).  Heart rate was significantly higher in the control group than the study groups during pneumoperitoneum Peak inspiratory pressure did not suffer significantly between the groups  and the p value was 0.976. During the pneumoperitoneum the groups 2 and 3  showed a significantly higher values than the group 1 ( p  0.000.)

Conclusions: During laparoscopic surgeries and increasing the minute ventilation by increasing the respiratory rate from 12 per minute to 14 per minute  produces a significant decrease in partial pressure of carbon  dioxide ,end tidal carbon dioxide and pH .

Keywords: respiratory rate, laparoscopic surgeries, hyperventilation.

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Dr Gayathri B

Assistant Professor, Department of Anaesthesiology

Stanley Medical College & Hospital Chennai-1