In one breath
When breathing stops, someone or something has to move air in and out of the lungs until the patient’s own rhythmic breathing comes back, and it has to start at once because the brain cannot last long without O₂. Machines do this for long periods, either by blowing air into the lungs (positive pressure) or by working on the chest from outside (negative pressure: the iron lung, the Bragg–Paul method). By hand, a rescuer uses mouth-to-mouth or mouth-to-nose breathing, or the Holger Nielsen back pressure–arm lift method. It only helps while the heart and circulation still work; if the heart has stopped too, it becomes part of Cardiopulmonary resuscitation (CPR).
Builds on: Asphyxia, hypercapnia and hypocapnia · Pulmonary edema and drowning · Leads to: Cardiopulmonary resuscitation (CPR)
When and why
- It is given in respiratory arrest, and kept up until the patient breathes rhythmically on their own again.
- Start immediately: the brain survives only a short time without an O₂ supply.
- It helps only while the heart and circulation are working normally. When the heart has stopped as well, ventilation is combined with chest compressions as Cardiopulmonary resuscitation (CPR).
Two families of methods
- Instrumental (mechanical): chosen when ventilation has to go on for a long time.
- Positive pressure
- Negative pressure: Drinker’s iron lung, the Bragg–Paul method, Boyle’s apparatus
- Manual: there are many, but three are used in practice.
- Mouth-to-mouth and mouth-to-nose breathing
- The Holger Nielsen method (back pressure–arm lift)
Instrumental methods
Positive pressure
- The usual method in the operating theatre during surgery.
- A machine pumps air, or air mixed with O₂, into the lungs under positive pressure, so the lungs are inflated from within.
- Drawback: it impairs venous return.
- Worth knowing, though not in your pages: inflating the lungs raises the pressure inside the chest instead of lowering it. That squeezes the great veins and weakens the gradient that brings blood back to the right atrium, so cardiac output can fall.
Negative pressure
These methods work on the chest from outside, alternately compressing it and letting it expand. Your book gives three.
- Drinker’s method (the iron lung): the patient lies in an airtight chamber with only the head and neck outside, and a pump raises and lowers the pressure in the chamber in turn.
- Bragg–Paul method (your book writes “Braggpaul”): a hollow, elastic rubber bag is wrapped around the chest and a pump inflates and releases it.
- Boyle’s apparatus: the automatic machine used for ventilation in hospitals. The rate, the depth and the mix of gas breathed in can all be set.
| Method | Inspiration | Expiration |
|---|---|---|
| Iron lung | chamber pressure below atmospheric → chest expands | chamber pressure raised → chest compressed |
| Bragg–Paul | bag released → chest springs out passively | bag inflated → chest squeezed |
- Worth knowing, though not in your pages: the iron lung kept patients with paralysed breathing muscles alive for long periods during the polio epidemics of the mid-20th century.
- Worth knowing, though not in your pages: Boyle’s apparatus is the standard anaesthesia machine, and when it ventilates a patient it pushes gas into the lungs, which most texts would call positive pressure. Your book lists it under negative pressure; be ready for an examiner who knows it the other way.
Draw it: the iron lung
- Draw a long, closed cylinder lying on its side, with the patient lying on their back inside it.
- Bring the head and neck out through an airtight collar at one end, so the nose and mouth open to room air.
- Attach a pump (bellows) to the other end of the chamber.
- Inspiration arrow: “pump lowers chamber pressure below atmospheric → chest expands → air enters through nose and mouth”.
- Expiration arrow: “pump raises chamber pressure → chest compressed → air leaves”.
- Title it “Drinker’s method: negative pressure”.
Manual methods
There are many hand methods; these three are the ones used.
| Method | Rate | Preferred for |
|---|---|---|
| Mouth-to-mouth | 10–15 breaths/min | adults |
| Mouth-to-nose | as mouth-to-mouth | infants and children |
| Holger Nielsen | 10–12 cycles/min | a respiratory cause, such as drowning |
Mouth-to-mouth breathing
- Clear the airway and extend the patient’s neck.
- Pinch the patient’s nostrils shut with the thumb and index finger of your right hand.
- Take a deep breath, seal your mouth over the patient’s mouth and blow out hard.
- Watch the chest expand, and check the abdomen for distension.
- Keep it going at 10–15 breaths a minute.
Worth knowing, though not in your pages: the chest rising is the sign that it is working; a swelling abdomen means air is going into the stomach instead of the lungs.
Mouth-to-nose breathing
The same routine, but the patient’s mouth is kept shut and you blow into the nostrils instead. It is the usual choice for children.
Holger Nielsen method (back pressure–arm lift)
Setting up:
- Lay the patient prone (face down), arms abducted at the shoulders and elbows bent, head turned to one side and resting on the hands.
- Kneel at the head end, with one knee close to the patient’s arm.
One cycle:
- Arm lift → inspiration. Straighten your back, lifting the patient’s arms until you feel resistance. The thorax expands, the pressure inside it falls and air flows in.
- Back pressure → expiration. Lower the arms gently. Lay your hands on the patient’s back over the mid-axillary region, fingers spread, and press lightly: the chest is squeezed and air flows out.
- Repeat 10–12 times a minute.
Worth knowing, though not in your pages: your book spells the name “Holger-Neilson” and “Holger Nielson”; the Dane who described the method was Holger Nielsen.
Draw it: the Holger Nielsen method
Draw two panels, each a side view of a prone patient whose head is turned and resting on the folded hands, with the rescuer kneeling at the head end.
- Panel A, arm lift: the rescuer straightens up and raises the patient’s arms toward the head until resistance is felt. Arrow into the mouth: “thorax expands, pressure falls → inspiration”.
- Panel B, back pressure: the arms are down, and the rescuer leans forward with both hands flat on the patient’s back, fingers spread. Arrow out of the mouth: “chest compressed → expiration”.
- Under both panels write “10–12 cycles per minute”.
The principle behind every method
Air flows into the lungs when the pressure in the alveoli is lower than at the mouth, and out when it is higher. Each method makes that difference in one of two ways.
| Approach | Methods | How air gets in |
|---|---|---|
| Push air into the lungs | positive pressure, mouth-to-mouth, mouth-to-nose | blown in under pressure |
| Work on the chest wall | iron lung, Bragg–Paul, Holger Nielsen | chest enlarges, pressure inside falls |
Worth knowing, though not in your pages: a rescuer’s expired air still holds about 16% O₂ (room air has about 21%), which is enough to oxygenate the patient in mouth-to-mouth breathing.
Exam-answer skeleton: "Write briefly on artificial respiration" (short note)
- Define it: ventilating the lungs of a patient in respiratory arrest until rhythmic breathing returns; start at once, because the brain soon dies without O₂.
- State the condition: it works only while the heart and circulation are working.
- Classify: instrumental (positive and negative pressure) and manual.
- Positive pressure: used in theatres; its drawback is impaired venous return.
- Negative pressure: the iron lung (how it gives inspiration and expiration), the Bragg–Paul method, Boyle’s apparatus.
- Manual: mouth-to-mouth (10–15/min), mouth-to-nose (children), and Holger Nielsen (10–12/min) with a sketch of the arm lift and back pressure.
- Close with the principle: the method makes alveolar pressure fall below, or rise above, the pressure at the mouth.
Asked in exams
- Artificial respiration: Jul 2013, 2 marks