The Triton


Sea Sick: ‘Pulse ox’ a vital part of every first-aid kit


Sea Sick: by Keith Murray

A common question people ask me is: “What medical equipment should I have on my boat and at home?”
The Top 2 inexpensive machines I always suggest are a good digital blood pressure machine and a pulse oximeter. These machines can give medical professionals a good idea if something is wrong with the patient, and possibly, how wrong and how quickly they will require medical attention.

While at sea, most of the bigger boats have on-call medical services that will want to know the patient’s vitals. The doctor on the other end of the telephone is, in essence, a detective trying to solve a mystery. The doctor needs clues to figure out what is wrong with the patient. The vital signs will be the first clue.

One of the vital signs needed is the patient’s pulse. The pulse is the beat felt against the wall of an artery each time the heart pumps. The pulse is the heart rate. In a normal adult, the pulse will be between 60 and 100 beats per minute. An adult’s heart rate can be manually checked with either the carotid pulse or radial pulse, but this requires a lot of practice and I have seen trained nurses struggle to get accurate numbers. There is an easier way — in fact, there are two ways. Both involve relatively inexpensive devices. The first is a digital or automatic blood pressure monitor, which ranges in price from $25 to $500. The second is a pulse oximeter, commonly called a pulse ox. These range in price from about $25 to $300.

Today we will be focusing on the pulse oximeter. A pulse oximeter is a medical device that can monitor the oxygen saturation of the patient’s blood and their pulse (heart rate). The pulse oximeter is a non-invasive medical device that slips on the patient’s finger. It does not hurt.

How does a pulse oximeter work? The pulse oximeter clips to the patient’s finger and holds one light on either side of the finger. The clip sends two beams of light across the nail bed. Inside the clip are two diodes. The first diode emits a red light and the second an infrared light. (You will be able to see the red light, but not the infrared.) These two beams of light enable the pulse oximeter to detect the color of the arterial blood, which helps to calculate the oxygen saturation.

Because a pulse oximeter is easy to use and provides quick results, they play a vital part in emergency medicine. Often these are very useful when working with patients with respiratory or cardiac problems such as chronic obstructive pulmonary disease (COPD), a common lung disease.

Emergency medical professionals will use the pulse ox on almost every patient. The information from the pulse ox is part of the vitals they obtain for every patient they treat. These vitals provide the general condition of the patient and let the paramedics know if the patient’s condition is improving, declining or unchanged.

OK, I have a pulse oximeter on my patient’s finger and I want to know what the numbers mean. What is a good number? A healthy person should have an oxygen saturation of 95-99 percent. These numbers may vary with age, health, current altitude and if the patient is connected to an oxygen tank. It is always best to let the trained medical professionals interpret these readings.

Should we all have one of these on board and at home? Yes, a good pulse oximeter is a vital part of every first-aid kit. For those who don’t have one, now is a good time to invest in one. All crew members should know how to use it, and should know what normal readings look like. When I teach an onboard class, we always review the pulse ox and let the crew try using it on each other.

Please note – the pulse oximeter will not provide accurate oxygen saturation information if the patient has been exposed to carbon monoxide. Carbon monoxide is a colorless, odorless gas that is produced by fires and exhaust from engines. If it’s suspected that a patient has been exposed to carbon monoxide, the medical provider should be alerted immediately.

The pulse oximeter may not perform well on patients with circulation issues, irregular or weak pulse rates, or in brightly lit areas. Bright lights may provide inaccurate readings since this device uses light to measure.

Trained as an emergency medical technician, Keith Murray now owns The CPR School, which provides onboard CPR, AED and first-aid training as well as AED sales and service ( Comments are welcome below.

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