Determination of heat gain in the inferior vena cava during thermodilution measurements.

The measurement of blood flow in the inferior vena cava (IVC) by thermodilution may be useful in the determination of hepatic venous blood flow (HVBF), but is subject to major errors. The most serious error is gain of heat from the abdominal viscera by the cool thermodiluent bolus as it moves up the IVC. The determination or elimination of this heat gain is necessary for accurate IVC blood flow measurement. By comparison of the area under the curve (AUC) for cardiac output following femoral vein injection of the thermodiluent bolus to the AUC following right ventricular injection of the thermodiluent, it is possible to quantitatively determine the unidirectional heat gain by the bolus at it moves up the IVC. The heat gain varied from 0 to 40% of the thermodiluent injected. The factors that aggravated the heat gain were a low cardiac output (below 4000 ml/mn), a large thermodiluent calorie load (over -40 calories), and possibly a slow transit time. The error due to heat gain may be effectively eliminated by keeping the size of the thermodiluent bolus below 40 negative calories.

Intra-abdominal pressure and manometric data of the distal esophageal sphincter. Their relationship to gastroesophageal reflux.

Nineteen patients with abnormal gastroesophageal reflux (13 with and six without hiatal hernia) had esophageal manometry and simultaneous 24-hour monitoring of esophageal pH and intra-abdominal pressure (IAP). Only 8% of all IAP challenges induced a reflux episode. This incidence increased to 13% in patients with a distal esophageal sphincter (DES) pressure of less than 5 mm Hg and an abdominal esophageal length of less than 1 cm, whereas it was only 6% in patients with a greater DES pressure and a longer abdominal esophagus. At the same time, there was an average of 2.7 reflux episodes per hour, of which 38.7% were caused by a challenge of IAP indicating that other mechanisms, besides changes in abdominal pressure, can cause reflux. There was no difference in DES pressure, length of abdominal esophagus, and the effect of IAP challenges in patients with and those without a hiatal hernia.

Clinical and in vitro analysis of determinants of gastroesophageal competence. A study of the principles of antireflux surgery.

The analysis of esophageal manometry and 24 hour esophageal pH monitoring in 266 consecutive patients indicates that the competency of the cardia depends upon the amplitude of the distal esophageal high pressure zone and the length of the abdominal esophagus. These two determinants of competency were examined using human esophagi in a unique in vitro model which allowed control of these parameters, as well as intraabdominal, intragastric, and intrathoracic pressures. The following principles of the function of the abdominal esophagus were graphically illustrated: (1) Competency of a segment of intraabdominal esophagus without intrinsic tone occurs only when intraabdominal pressure is equal to or greater than intragastric pressure. (2) Competency of a segment of intraabdominal esophagus without intrinsic tone is directly related to its length. (3) The length of intraabdominal esophagus necessary to maintain competency is indirectly related to variations in intraabdominal pressure. (4) Competency of a segment of intraabdominal esophagus is augmented by the presence of intrinsic tone, and the shorter the length, the greater the intrinsic tone needed. (5) Competency of a segment of intraabdominal esophagus is augmented by negative intrathoracic pressure. These findings beautifully illustrate the mechanical valvelike function of the abdominal esophagus and the objectives to be accomplished in the surgical treatment of gastroesophageal reflux.

An improvement in whole body plethysmography.

A simple method for greatly reducing thermal drift and acoustic noise in constant-volume, whole body plethysmography is described. Evaluation and adjustment for any particular clinical application can be carried out in a few moments. The device itself consists of a 20- to 25-gauge needle, a "Y" tube, and a 1-liter or more vessel, and may be assembled in 30 minutes from parts readily available in any hospital laboratory.

Branching pattern of airways and air spaces of a single human terminal bronchiole.

A polyurethane-foam enlarged reconstruction was made from serial sections of a portion of young adult human lung parenchyman. Study of the progeny of a terminal bronchiole disclosed three generations of respiratory bronchioles and an irregular branching pattern of eight generations of alveolar ducts. Sacs and alveoli arose from the lateral and distal aspects of all generations of ducts. There were an average of 3.5 alveoli per sac. Considering the terminal bronchiole as the first generation branch of the acinus, over 60 per cent of the alveoli counted and predicted were members of the 10-12th generations. The acinus contained one terminal bronchiole and approximately 14 respiratory bronchioles, 1,200-1,500 ducts, 2,500-4,500 sacs, and 14,000-20,000 alveoli.