Air Consumption

I enjoy reading online about how various departments and crews spend their winter months, or any month really, training. A favorite winter drill I see each year is an air consumption exercise.

There are many variations of the training which usually involves a game of sport such as volleyball, basketball or even dodge-ball. With adult education it is a priority to convey to the adult learner why they are asked to perform a skill or why we are spending time studying a certain subject.

This motivates the learner and creates ownership or a buy in to the training. In the case of the air consumption drill, the object seems to be to don an SCBA and perform a physical activity over time to see how long the participant is able to conserve a limited supply of air.

While this drill is good to build tolerance and show that active consumption rates do not always equal factory rates, these drills do little to identify breathing abnormalities and correct them.

To make this training more effective we need to teach physical conditioning exercises, air conservation skills and recovery techniques to
the participants. We then need to recreate the physiological stress over several weeks for the same period of time each training session and see if the participant improves their ability to conserve air.

Pulmonary Science:

Minute ventilation is the volume of air inhaled or exhaled over one minute. The normal respiratory cycle of a healthy adult is steady and can be predicted. Rate and depth of breathing stays constant and rate of breathing is repetitive with uniformed inhalation and exhalation times. If we measured the volume of air taken in with one breath and divided it by the number of breaths in a minute, we would be able to calculate the minute volume or VE.

Peak inspiratory flow is the fastest flow of air inhaled during the respiratory cycle.

As we do work and exert our muscles we create an increased oxygen demand. The body must compensate for this increased demand and draw in oxygen at faster flows. To do this the body increases the minute ventilation by increasing the number of breaths per minute and increasing the volume of air inspired during each breath. During strenuous exercise this could require peak inspiratory flows, also known as inspiratory demand, of over 100L/min. At the same time the body increases the heart rate and blood pressure to increase the circulation of oxygen to the muscles.

As we exert ourselves on the fire ground we begin to breathe faster and deeper and our heart rate and blood pressure increases. The physiological numbers are affected by the physical conditioning of the individual the ability of the lung to stretch and the ability of the airways to stay dilated.

There is a direct relationship between breathing and heart rate. Our bodies have a weakened version of the mammalian diving reflex. This means that if we were to dive in cold water our bodies would decrease our heart rate to allow oxygen to be used more efficiently.

We can induce this same effect by increasing Co2 levels in our body. Co2 is a bi-product of respiration. Meaning that it is the air left in our lungs at the end of inspiration cycle and after oxygen uptake. This air is waist and is waiting to be exhaled. Co2 levels can be increased If we slow down our breathing and increase the pause between inspiration and expiration. This increase in Co2 will decrease our heart rate and decrease our oxygen demand.

When faced with low levels of self-contained air in our packs, we must decrease our heart rate, respiratory rate and volume of air consumed. The only factor our of those three that we have control over is the respiratory rate. We can consciously slow our breathing and decrease our heart rate allowing oxygen to be used more efficiently which in turn will decrease the volume of air consumed with each breath.

Consider the scenario of unextractable entanglement while low on air. In order to conserve air, the first step must be to try and relax and decrease energy expenditure. Once the body is relaxed even a little, the respiratory rate will begin to decrease. Try and put the body into a position that decreases weight on the diaphragm and opens up the chest for expansion. The second step to decrease the work of breathing is to modify breathing patterns. The normal ratio of Inspiration to expiration is 1:2. That means twice as much time breathing out than breathing in. In step 2 we are going to force ourselves through relaxed concentration to breathe in for 4 seconds and out for 8 seconds. Once we can comfortably maintain this pattern we are going to add a breath hold before breathing out and then again before breathing back in.

This is called box breathing and can be done any time you want to conserve your self-contained air. This looks like; breathe in for 4 hold for 2, breathe out for 8 hold for 2. Breathing like this adds 4 seconds of uninspired air to each breathing cycle. This brings the total seconds of uninspired air to 12/ cycle which will significantly lower the breaths per minute and increase Co2 retention in the lungs. As Co2 levels build the heart rate will decrease and the volume of air inspired with each breath will also decrease. As the inspiratory demand decreases we will conserve more air volume in our cylinders.

When training firefighters to conserve air, time must be taken to teach body mechanics and respiratory pattern modification. The air consumption drill should be done in two parts.

At the first training session, the firefighter should be given progressively intense tasks or exercises while wearing full PPE to induce high heart rates and high breathing rates.

Cross Fit style workouts work good for this including high Intensity Interval Training. A good exercise example would be a sledge hammer and tire evolution.

Have a firefighter strike a tire with a sledge hammer at a moderate pace for 45 seconds. For the last fifteen seconds have the firefighter double his rate of strikes.

Use a metronome app to help keep the rhythm. A stair machine is another good interval exercise a third to consider would be push presses or a dead lift into a push press.

Once the low air alarm sounds have the firefighter kneel and crawl. Simulate an entanglement and collapse that is unextractable, and call a mayday. The firefighter will initiate your department’s Mayday procedure.

Record how long the cylinder lasts before there is only one or two breaths left. Once the firefighter is recovered teach them the positional technique to optimize breathing and also show how to perform box breathing.

Have the firefighter practice both techniques and coach as needed. The firefighter will be assigned to practice these techniques during the off time over the next week by performing the exercises and then the recovery techniques.

One week later repeat the drill with the exact same exercises as before. Once the low air alarm sounds have the firefighter kneel and crawl. Simulate an entanglement and collapse that is unextractable. and call a mayday. The firefighter will initiate your Mayday procedure and then try and position themselves in the fetal position to conserve air through relaxation and box breathing.

Record how long the cylinder lasts before the final few breaths. Compare week one’s times with week two’s times and see if there is an improvement.

Always stress air management and being self-aware of your air capacity at all times. Stress also always having two ways to escape your current position. While conducting this training you want to reinforce good behaviors and mindsets for working in IDLH environments.

Exercising in SCBA is a fine way to build tolerance and conditioning, but if we are calling it an air consumption drill we must provide tools and techniques to conserve air or we are just playing games in masks. Giving firefighters solid survival skills builds confidence and allows them to work more aggressively.