Body Pressures

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.

Body Pressures

Common  body pressure measurements include blood pressure  (80/120-mm (300 mm Hg, max)), respiratory pressure (4 kPa) and intraocular pressure for glaucoma testing (15 mm Hg). However, there are several other pressure measurements made at different body locations, most are made for diagnostic purposes. These include:

  • intra-bladder pressure (IBP) 12.3 ± 4.5 mmHg depending on body position to about 22 mmHg.
  • intragastric pressure, (IGP) 15.5 ± 3.5 mmHg vs 18.0 ± 8.7 mmHg
  • intra-abdominal pressure (IAP) typically less than 12 mmHg
  • anorectal manometry (ARM) 49 ± 3 mmHg resting to 238 ± 38 mmHg maximum squeeze range
  • vacuum (negative pressure) for an electric breast pump 0-270 mmHg

Similar to blood pressure and intraocular pressure, higher than normal readings identify potentially dangerous health situations. For example, an IAP equal to or above 12 mmHg is called Intra-abdominal Hypertension (IAH). Also, an IAP above 20 mmHg with evidence of organ dysfunction/failure defines abdominal compartment syndrome (ACS). Both of these higher than normal readings are known to cause significant morbidity and mortality among critically ill patients.

For healthy subjects, anal pressure is highly reproducible on separate days. ARM measurements in resting mode vary from 49 ± 3 to 58 ± 3 mmHg in women and from 49 ± 3 to 66 ± 6 mmHg in men. In contrast, maximum pressures range from 90 ± 9 to 159 ± 45 mm Hg in women and from 218 ± 18 to 238 ± 38 in men.

Oral to anal pressures vary depending on the location of the muscle cross sectional area (MCSA).

Oral to anal pressures vary depending on the location of the muscle cross sectional area (MCSA).
Source:  Physiology of the Gastrointestinal Tract .

Depending on the location, a significantly lower pressure can be a problem, too. For most people, blood pressure in the foot is similar to the blood pressure in the arm. A pressure drop of as little as 10% can indicate peripheral artery disease (PAD).

Not all pressures are positive measurements or made for diagnostic purposes. For example, an electric breast pump uses a vacuum (negative pressure) as high as 270 mmHg to collect milk for newborns.

For all of these body pressure measurements, highly accurate microelectromechanical systems (MEMS) pressure sensors can provide an essential tool for optimum healthcare.

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Getting the Right Medical Room Pressure

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.

Getting the Right Medical Room Pressure

With airborne infectious diseases that can easily spread from one person to another, such as the COVID-19 virus, isolation is critical. In a hospital or clinic, an isolation room needs negative pressure to have airflow into the room and avoid pathogens, or germs, from escaping. In addition to viruses, other undesirable contaminants to keep away from the rest of the population and sterile equipment in a hospital include bacteria, fungi, yeasts, molds, pollens, gases, volatile organic compounds (VOCs), small particles and chemicals.

The airflow to create and maintain the negative pressure (vacuum) in the room requires a consistent pressure differential of about 0.01 inch water gauge (in. w.g.) or 2.5 Pascals (Pa).

According to the Facility Guidelines Institute’s (FGI’s) most recent 2018 FGI Guidelines ANSI/ASHRAE/ASHE Standard 170-2017, other rooms that should be negatively pressurized include:

  • Emergency Department Public Waiting Areas
  • Emergency Department Decontamination
  • Radiology Waiting Rooms
  • Triage
  • Bathrooms
  • Airborne Infection Isolation (AII) Rooms
  • Most Laboratory Work Areas
  • Autopsy Rooms
  • Soiled Workrooms or Soiled Holding Rooms
  • Soiled or Decontamination Rooms in Sterile Processing Department
  • Soiled Linen Sorting and Storage
  • Janitors’ Closets

In contrast, protecting the patient and sterile medical and surgical supplies in an operating room requires positive pressure to keep undesirable contaminants outside. The positive pressure room is achieved by pumping in filtered, clean air.

Isolation (Low) vs. operating room (High) pressure

Isolation (Low) vs. operating room (High) pressure.
Source: Minnesota Department of Health

In fact, some portable, headgear-mounted air purifying respirator systems use positive pressure to protect the wearer.

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Negative Pressure Wound Therapy

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.

Negative Pressure Wound Therapy

Unlike Hyperbaric Oxygen Therapy (HBOT) that employs a chamber with a pressure higher than 1 atmosphere absolute, negative pressure wound therapy (NPWT) uses a vacuum to enhance and promote wound healing in acute, chronic and burn wounds. In this medical procedure, a sealed wound dressing is attached to a pump that creates a negative pressure environment for the wound.

The vacuum helps to increase blood flow to the area and draw out excess fluid from the wound and depending on the type of wound type or location, it can either be applied continuously or intermittently. This type of therapy can be implemented for a few days to several months at a time.

The types of wounds that can benefit from negative pressure wound therapy, include:

  • diabetic ulcers
  • venous ulcers
  • arterial ulcers
  • pressure ulcers
  • first and second-degree burns
  • chronic wounds
  • wounds with large amounts of drainage
  • surgical and acute wounds at high risk for infection

Acelity V.A.C.Ulta Therapy System

Used in its V.A.C.ULTA™ Therapy System and other wound care products, Acelity’s SENSAT.R.A.C.™ Technology is a real-time pressure feedback system that adjusts its pump’s output, compensating for wound distance, wound position, exudate characteristics and patient movement. Source: Acelity.

The applied negative pressure in NPWT can range from -125 to -75 mmHg (-2.4 to -1.5 psi) depending on the type of wound and the patient’s tolerance. For this application, All Sensor’s DLV-005D with its digital output would be an easy way to measure the vacuum level for both the machine’s use and the health care provider’s and patient’s observation.

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

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.

Suction Solutions

Designers often look to nature for ideas that can be implemented in new products. Octopus suction cups provide an interesting pressure example.

When the octopus’ sucker is sealed to a surface, contraction of its radial muscles thins the wall of the sucker which tends to increase the enclosed volume.  However, the cohesiveness of water resists volume expansion and the pressure of the enclosed water decreases instead. With this mechanism, an octopus can create a pressure differential of 100-200 kPa (14.5-29 psi) at sea level and generate a significant amount of force.

Suction cups allow professional glazers to easily pick up and move large pieces of glass. One company offers a Vacuum Cup Octopus with Pump that can lift a maximum weight of 185 kg (407.9 lbs.) vertically with a 300-mm (11.8-in) diameter vacuum cup. One version includes a manual vacuum pump with a leak gauge to monitor the effectiveness of the suction.

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Source: Vacuum Cup Octopus with Pump

Vacuum suction cups offer a versatile method of material handling. In fact, suction cups also allow robots to pick different smooth surfaced objects. The approach has been applied to the robotics field since the 1960s. One recent research effort focuses on suction cups that can be used on robots designed to perform tasks in unstructured and contaminated environments. Of course, monitoring the amount of vacuum (negative pressure) with an accurate and rugged microelectromechanical systems (MEMS) pressure sensor can provide an even greater amount of control to more sophisticated suction applications.

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