A novel approach in understanding the basic modes of ventilation in a recent generation mechanical ventilator- A review of the underlying principles.

Understanding the basic concepts and the dynamics of the equation of motion will help the anaesthesiologist and the intensive care physician in gaining an insight into the basics of modern mechanical ventilation. An equation of the type Vt = V0 × (1-e-kt) is often encountered while studying the concepts of mechanical ventilation. This leaves one wondering about the meaning of 'e'. It is explained as the base of a natural logarithm, and the base e as an irrational constant approximately equal to 2. 7182. In medical literature, various physiological mechanisms are explained by using the exponential function e. However, the explanations do not sufficiently help the learner to demystify the enigmatic term e. In this article, an effort is made to explain this function with the help of simple analogies and relevant mathematical concepts. The process of volume build-up in the lungs during mechanical ventilation is used as a model for the explanations.

Isobaric forms of ropivacaine vs. bupivacaine in lower abdominal surgeries: a hospital-based, prospective, comparative study.

We aimed to assess whether ropivacaine (0.75%; 22.5 mg) can replace bupivacaine (0.5%; 15 mg) as a better intrathecal anesthetic in lower abdominal surgery. In this hospital-based, single-blind, randomized, prospective, comparative study, 100 patients of either sex, aged between 18 and 70 years, weighing 40-80 kg, with American Society of Anesthesiologists physical status 1 and 2, and undergoing lower abdominal surgery were randomly allocated into two groups to receive intrathecal isobaric bupivacaine 0.5% 3 mL (15 mg) or ropivacaine 0.75% 3 mL (22.5 mg). In the intraoperative period, the onset, efficacy, duration, and regression of sensory and motor blockade and the quality of anesthesia and hemodynamic effects were observed at regular intervals. The ropivacaine and bupivacaine groups were comparable for demographic parameters. The duration of onset of sensory and motor blocks was significantly shorter in the bupivacaine group (P < 0.01). In the ropivacaine group, a faster recovery from sensory block (P = 0.02) and higher segmental height [thoracic (T)10 and T8] were achieved (P < 0.01). Bradycardia and hypotension were insignificant in the ropivacaine group (P > 0.05). Isobaric ropivacaine is a better spinal anesthetic in lower abdominal surgeries as it provides faster recovery from sensory block and a higher level of segmental sensory block with fewer side-effects.