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Pressure and Laparoscopic Surgery Part 2

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure and Laparoscopic Surgery Part 2

The intravenous (IV) tube delivers saline and other chemicals to the patient before, during and after the laparoscopic surgery. Following the standard procedure, the IV bag is hung at least 3 feet above an adult patient’s heart to ensure there is sufficient pressure to keep the IV running at a constant rate. The height of three feet ensures a minimal pressure of 67.2 mmHg.

In addition to carbon dioxide (CO₂) pressure, blood pressure measurements and other pressures are involved in laparoscopic surgery. Three examples include an intravenous (IV) tube, spirometer, and an intermittent pneumatic compression (IPC) device.

A spirometer can be used to increase the patient’s post-surgery lung capacity. The process involves a graduated scale on a closed air cylinder, a movable piston, and a pointer. With an incentive spirometer, the patient inhales for as long as possible while holding the pointer within a specific range (constant negative pressure) to demonstrate lung capacity. Periodic usage helps patients to increase their post-surgery capability. Desired capacity can vary depending on age, height, and other factors but values around 2500 ml are not uncommon.

Image of an An intermittent pneumatic compression (IPC) device on the end of a hospital bed. The screen shows an illustration of three zones of the leg to which the device is applying a cycling pressure. — Intermittent Pneumatic Compression (IPC) device

An intermittent pneumatic compression (IPC) device cuff around a man's leg, with a blue hospital sock at the bottom. The leg is resting on a hospital bed. — A leg encased in an Intermittent Pneumatic Compression (IPC) cuff

An intermittent pneumatic compression (IPC) device applies a cycling pressure (figure shows three zones) to the leg after laparoscopic surgery to prevent a Venous Thromboembolism (VTE), including Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). The device uses a cuff around each leg that are periodically and sequentially (from ankle towards the heart) filled with air and squeeze the patient’s legs. This process increases blood flow through the veins of the legs and helps prevent blood clots.

For other pressures involved in laparoscopic surgery see Pressure and Laparoscopic Surgery Part 1.

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Pressure and Laparoscopic Surgery Part 1

Pressure and Laparoscopic Surgery Part 1

Getting room to operate with pressure

Laparoscopic surgery provides an alternative to more extensive open surgical procedures. Its benefits include reduced postoperative pain, reduced scarring and shorter hospital stays. Accessed by incisions through the stomach (abdominal wall), several procedures including appendectomies are routinely performed using laparoscopic surgery. Having adequate space to repair or remove the affected area is achieved by pumping (or insufflating) a gas, usually carbon dioxide (CO₂), into the abdominal (or peritoneal) cavity to create a pneumoperitoneum (abnormal space).

Laparoscopic surgery showing a three-way valve in the gas line (arrow), gas return line (top right) scope (at navel) and operating device.
Source: SemanticsScholar.org

Pressure inside the abdominal compartment, the intra-abdominal pressure (IAP), is normally 0 to 5 mmHg but it can increase to 5 to 7 mmHg during a critical illness. For laparoscopic surgery, carbon dioxide is insufflated into the peritoneal cavity at a rate of 4–6 liter/min to a pressure usually between 12 and 15 mmHg but sometimes the range increases to between 10 to 20 mmHg. To keep this pressure steady, the pneumoperitoneum is maintained by a constant gas flow of 200–400 ml/min.

A high IAP is associated with postoperative problems, so researchers are investigating different techniques to provide alternative lower pressure recommendations for adequate work space instead of using the current, predetermined levels. One study found that the different approaches they tried resulted in an acceptable workspace at 8 mmHg IAP in 61 out of 78 patients.

For other pressures involved in laparoscopic surgery see Pressure and Laparoscopic Surgery Part 2.

Do you have a pressure sensing question? Let us know and we’ll address it in an upcoming blog.
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Smoke Bomb Pressures

Smoke Bomb Pressures

Smoke bombs have a variety of applications from detecting leaks in plumbing systems to discovering alternate entrances in collapsed caves or mines or providing cover/smoking out individuals in dangerous situations. Since they are bombs, pressure is involved in their safe and effective use.

Sewer smoke bombs are injected into a plumbing system through a smoke blower. One type of manhole air/smoke blower injects dense white smoke into sanitary or storm sewers for quick detection of unwanted inflows and leaks from roof downspouts, drain tiles, leaking manholes and more. In these smoke blowers, the amount of air flow and static pressure can vary depending on added features from 1800 cubic feet per minute (CFM) at 1.7-inch static pressure for a standard capacity unit to 4200 CFM at 3.0-inch static pressure and 4000 CFM at 4.0-inch static pressure with optional hardware.

For dangerous situations that require providing cover for first responders or smoking out the bad guys, the burning pressure for M18 colored-smoke grenades is usually less than 1 psi. If the smoke bomb was intended to simply deliver a colorful display, there needs to be sufficient pressure inside the smoke bomb to push the smoke out but not too much pressure or else it will burst.

Source: ThoughtCo. (Waldemar Blazej Nowak / EyeEm / Getty Images)

When the dye in a display smoke bomb is vaporized, the pressure from combustion forces it out to produce the smoke.

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Bite Force Pressures

Bite Force Pressures

You may have heard or read about or even seen the video of a caged male lion biting off the finger of a Jamaican zookeeper who put his hand through the cage’s fencing. While there are many responses that an event like this can trigger, a technical one is “how much bite force does a lion have?” Depending on their age, size and gender, a lion’s bite force can range between 650 and 1,000 pounds per square inch (psi), according to A-Z Animals, an online animal encyclopedia.

Do not try this – even in a zoo.
Image source: New York Post.

How does a lion’s bite force that compare to other animals? The land animal with the greatest bite force is the saltwater crocodile with a measurement of 3,700 psi for a 17-ft long subject. A sensor placed at the end of a stick safely provided the force measurement. Since some saltwater crocodiles can reach up 23 feet in length, a much larger force would not be surprising. In contrast, researchers estimate that a 21-foot great white shark can produce a bite force of nearly 4,000 psi. However, this number is based on computer modeling – not actual measurements.

In humans, bite force is important especially in dental research. Since the researchers can rely on the cooperation the subject, the bite force measurements are made with force transducers, such as strain gauge transducers, piezoresistive transducers, piezoelectric transducers, optical fiber transducers and pressure-sensitive films. The average human bite force is 162 psi.

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