Video References

Interested in learning more about the theory?

This page provides links and videos that will provide the background information and science I used to better understand the theory myself.

You have to remember that the theory began after migraines were eliminated for me at the Ontario Migraine Clinic. I sat in a room with acupuncture needles stuck in me while I practiced this breathing method. I went from 15 migraines a month to ZERO and have not had a migraine in 7+ years. Was it the acupuncture or the breathing? My money is on the breathing.

Once I realized that it was actually the breathing that got rid of my migraines I set out to find out why.

During my research, I was very surprised at how much I didn’t understand our most important function. Breathing should be taught at an early age & this should be supported throughout school. Check it out for yourself.

For more info on the Bohr effect, check this page http://banishmigraineheadachesforever.com/the-bohr-effect/

For studies regarding hypoxia & migraines click here http://banishmigraineheadachesforever.com/studies/

Pulmonary Gas Exchange Part I

Lectures in Respiratory Physiology,  John B West MD, PhD

Pulmonary Gas Exchange-Part II

Lectures in Respiratory Physiology,  John B West MD, PhD

Start at 11m 50sec.

Acid Base Balance

Lectures in Respiratory Physiology,  John B West MD, PhD

Blood Gas Transport

Lectures in Respiratory Physiology,  John B West MD, PhD

Transport of Respiratory Gases

Transport of Respiratory Gases – Partial pressure of oxygen and carbon dioxide, dissociation curves, transport of carbon dioxide, the bohr effect etc. A2 Biology Revision (AQA Spec. A)

Negative Effects of Mouth Breathing | Mark A Cruz DDS

http://www.markacruzdds.com/
Mark A. Cruz DDS talks about the effects of mouth breathing and how negative effects within the body may arise simply due to mouth breathing. Important functions of the body, such as alkalinity of the blood becomes compromised, affecting other organs.

Evolution Trainers – How To Breathe Properly

Ashley Selman talks to Lisa Engles about how to breathe properly. Lisa explains that many people are ‘paradoxical’ breathers and how to use your diaphragm to breathe correctly.

Negative Effects of Mouth Breathing | Mark A Cruz DDS

http://www.markacruzdds.com/
Mark A. Cruz DDS talks about the effects of mouth breathing and how negative effects within the body may arise simply due to mouth breathing. Important functions of the body, such as alkalinity of the blood becomes compromised, affecting other organs.

Mouth Breathing causes Sleep Apnea

Buteyko practitioner Patrick McKeown examines the research linking open mouth breathing to snoring and sleep apnea.

Mouth Breathing, Swaddling: Effects on Cell O2 Levels

 

Mouth breathing (during sleep too), lack of swaddling of babies and other lifestyle factors can destroy our health. Mouth breathing in children and adults means lack of O2, CO2 and nitric oxide in the body cells.

For over 80% of sick people and majority of modern healthy people, body oxygenation and stress-free breath holding time are lowest during early morning hours or during sleep due to negative effects of chronic overbreathing (hyperventilation) and low CO2 content in the cells and blood . Why? Many modern people breathe through the mouth during their sleep. Mouth breathing drastically decreases oxygen level in body cells. Another important factor is sleeping on one’s back at night. This lifestyle factor also reduces body oxygen content about 2 times.

For infants and toddlers, there is a special factor that causes poor health and hyperventilation: lack of swaddling. Swaddled babies breathe less, sleep longer and are more quiet. They develop better and remain healthy. These are the main pros for swaddling. There are virtually no cons.

Why Breathing Through Your Nose is Important

Diaphragmatic Breathing vs. Chest Breathing in Modern People

Diaphragmatic breathing is very rare these days even in those people who practice diaphragmatic breathing exercises. Chest breathing is very common. Over 90% of modern people are chest breathers. (I am talking about automatic or unconscious breathing at rest and during sleep.) Why do we have these problems? Note that diaphragmatic breathing provides much more oxygen for the arterial blood since blood flow at the bottom of the lungs is about 7 times stronger than at the top of the lungs, as Dr. Artour Rakhimov explains .

Modern people breathe about 2 times more air every minute than the medical norm for minute ventilation at rest. Over breathing reduces body oxygen content and leads to spasms in body muscles, the diaphragm included.

In the past, diaphragmatic breathing was common since people had much higher body oxygen levels due to light and slow breathing patterns. High CO2 relaxes muscles of the human body and helps with correct posture due to excellent oxygenation of the muscles.

Abdominal breathing usually becomes the norm (24/7), when the morning CP (control pause or body oxygen index) is over 30 s. (To find the CP measure your stress-free breath holding time after usual exhalation.)

It is logical that people in the past (about 100 years ago and before that) had diaphragmatic breathing 24/7. Since relatively healthy people have about 20-25 s CP these days, most of them are chest breathers.

Breathing retraining techniques can be used to restore abdominal breathing or belly breathing. These include the Frolov breathing device, Buteyko method, Strelnikova breathing gymnastic, and hatha yoga.

Hyperventilate, Have Less O2 in the Brain, And Be Unaware about That

We can breathe 2-3 times more than the physiological norm and are not aware that our breathing is way too heavy. This causes devastating health effects. Deep and big breathing (hyperventilation) leads to … lowered tissue oxygenation, which is the normal feature of cancer, heart disease, diabetes, arthritis, chronic fatigue and many other problems.

This video discusses the main paradox of breathing: those people, who breathe little, have a lot of oxygen in the body; sick people breathe heavy, but suffer from tissue hypoxia.

Hyperventilation: Breathing Effects on Brain Oxygen and Health

Chronic hyperventilation syndrome is common in modern people. Such breathing reduces oxygen transport to brain and other body cells.

Over 90% of modern population and people with chronic diseases breathe much more than the medical norm 24/7. It is called chronic hyperventilation syndrome. You can check these medical studies here (over 40 references):
http://www.normalbreathing.com/hyperv…

Furthermore, when people breathe 2-3 times more air than the medical norm, they are usually totally unaware that their breathing is too heavy.

What are the main physiological and biochemical effects of over-breathing on our brains? There are 3 key effects:
- reduced perfusion or blood supply for the brain cells;
- lowered oxygenation of brain tissues
- and increased excitability of the nerve cells (spontaneous and/or asynchronous firing of neurons).

These effects can cause stress, anxiety, sleeping problems, phobias, panic attacks and even mental problems. As a result, healthy breathing is crucial for good or normal mental health.

All these effects have been confirmed by hundreds of physiological research studies and are based on CO2 deficiency in the arterial blood due to hyperventilation. Dr. Buteyko devoted his life to studying chronic hyperventilation syndrome and effects of CO2 on the human organism.

Mouth Breathing vs. Nose Breathing (for Mouth Breather)

 

If you are a mouth breather, you need to know the following medical facts. Published-western-clinical evidence clearly proved thatmouth breathing is one of 2 immediate leading causes of mortality in the severely sick patients with chronic diseases. Early morning hours (from about 4 to 7 am) have the highest death rates due to coronary-artery spasms, anginas, strokes, asthma attacks, seizures and many other exacerbations. The relevant medical research is considered on the web page “Sleep Heavy Breathing Effect”.
http://www.normalbreathing.com/index-nasal.php

MOUTH BREATHING VS. NASAL BREATHING

 

Certain individuals, whether children or adults, have a tendency to breathe through the mouth instead of the nose. Whether you are exercising, sleeping or going about daily life, it is preferable to do nasal breathing rather than mouth breathing. When you breathe through your mouth, your brain is tricked into thinking that carbon dioxide is escaping the body too quickly. This stimulates the production of mucous, as the body attempts to slow the breathing.

Read more: http://www.livestrong.com/article/255298-mouth-breathing-vs-nasal-breathing/#ixzz2j8Sdsy2s

Mouth Breathing Can Cause Major Health Problems
“Children who mouth breathe typically do not sleep well, causing them to be tired during the day and possibly unable to concentrate on academics,” Dr. Jefferson said. “If the child becomes frustrated in school, he or she may exhibit behavioral problems.”

http://www.medicalnewstoday.com/releases/184696.php
http://www.sciencedaily.com/releases/2010/04/100406125714.htm

Nose Breathing

 

Breathing through the nose has many benefits. Breathing through the mouth, many negatives. There are some researchers who believe that mouth breathing and associated hyperventilation causes or exacerbates asthma, high blood pressure, heart disease, and many other medical problems. It makes some folks look dull witted or slightly unconscious.

http://www.breathing.com/articles/nose-breathing.htm

‘Mouth-breathing’ gross, harmful to your health

 

Jefferson believes breathing though the mouth is often an overlooked root cause of many health and behavioral problems, particularly in school-age kids. (“Just think of the child,” he says. “How do you think they’re doing in school? These kids are tired, they’re irritable, they can’t concentrate in school. And a lot of these kids (may be) diagnosed with ADD and hyperactivity.”)

http://www.nbcnews.com/health/mouth-breathing-gross-harmful-your-health-1C6437430

Chest Breathing | Thoracic Breathing: Effects, Tests and Solutions

 

Chest breathing (or thoracic breathing) is very common in modern people. More than 50% of adults have predominantly chest breathing at rest. It is even more common for people with chronic diseases, who breathe too deeply at rest, as this table shows.
http://www.normalbreathing.com/index-chest-breathing.php

Normal Respiratory Rate, Volume, Chart, …

 

Normal respiratory rate in adults is 12 breaths/min. Normal breathing, as we discussed, is strictly nasal (in and out), mainly diaphragmatic (i.e., abdominal), slow (in frequency) and imperceptible (or small/shallow in its volume).
http://www.normalbreathing.com/index-nb.php

Normal Respiratory Rate – Breathing Frequency (Health, Disease, Yoga, …)

Respiratory rate (respiration rate, breathing frequency, breathing rate, ventilation rate, pulmonary ventilation rate, and respiratory frequency) is the number of breaths that a person takes during one minute. The normal value for an adult is 10-12 breaths per minute at rest. Yoga masters breathe much slower.

Medical research suggests breathing frequency is the indicator of pulmonary problems that get progressively worse with progress of chronic health conditions, such as heart disease, asthma, COPD, diabetes, HIV-AIDS, cancer, and cystic fibrosis.

You can find more facts related to respiratory rates for adults with cancer patients, cystic fibrosis, heart disease, asthma, diabetes, COPD and many other conditions on pages of NormalBreathing.com.

Medical textbooks suggest that the normal respiratory rate for adults at rest is only 10-12 breaths per minute. Older physiology textbooks often provide even smaller values (e.g., 8-10 breaths per minute), while more recent textbooks can give up to 15-18 breaths per minute. Ideal breathing rate is 3-4 breaths per minute as in real yoga masters.

Most modern adults breathe much faster (about 15-20 breaths per minute) than their normal respiration rate. Respiratory rates in people with chronic diseases are usually higher: often nearly 20 breaths/min or even higher.

NormalBreathing.com has numerous medical studies that testify that respiratory rates in terminally sick people with cancer, HIV-AIDS, cystic fibrosis and other conditions is usually over 30 breaths/min.

Another webpage with this URL: http://www.e-breathing.com/respiration/normal-respiratory-rate/ also provides details related to medical norms and values for breathing frequency in people with chronic health problems.

Normal values for respiratory rate:
- during exercise: 50-60 breaths/min
- hatha yoga pranayama: 0.5-3 breaths per minute
- firebreath (hatha yoga exercise): 100-120 breaths/min.

Normal respiration rates in children
- Newborns and infants (up to 6 months old): 30-60 breaths/min
- Infants (6 to 12 months old): 24-30 breaths/min
- Toddlers and children (1 to 5 years old): 20-30 breaths/min
- Children (6 to 12 years): 12-20 breaths/min.

Charts and graphs of breathing patterns, minute ventilation and results of the body oxygen test (Buteyko CP test) can be found on this page: http://www.normalbreathing.com/index-rate.php and the link provided above. Also, the Amazon book “Yoga Benefits Are in Breathing Less” describes the causes of poor efficiency of modern yoga and effects of classic yoga on health and breathing..

References for Table 1 (Minute ventilation and
prevalence of CHV in patients with chronic diseases)

 

Sourced from http://www.normalbreathing.com/

Dimopoulou et al, 2001

Dimopoulou I, Tsintzas OK, Alivizatos PA, Tzelepis GE, Pattern of breathing during progressive exercise in chronic heart failure, Int J Cardiol. 2001 Dec; 81(2-3): p. 117-121.

Intensive Care Unit and Pulmonary Function Laboratory, Onassis Cardiac Surgery Center, Athens, Greece.


Johnson et al, 2000

Johnson BD, Beck KC, Olson LJ, O’Malley KA, Allison TG, Squires RW, Gau GT, Ventilatory constraints during exercise in patients with chronic heart failure, Chest 2000 Feb; 117(2): p. 321-332.

Divisions of Cardiovascular, Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA


Fanfulla et al, 1998

Fanfulla F, Mortara , Maestri R, Pinna GD, Bruschi C, Cobelli F, Rampulla C, The development of hyperventilation in patients with chronic heart failure and Cheyne-Stokes respiration, Chest 1998; 114; p. 1083-1090.

Respiratory Function Laboratory, IRCCS, S. Maugeri Foundation, Montescano Medical Center, Pavia, Italy.


Clark et al, 1997

Clark AL, Volterrani M, Swan JW, Coats AJS, The increased ventilatory response to exercise in chronic heart failure: relation to pulmonary pathology, Heart 1997; 77: p.138-146.

Departnent of Cardiac Medicine, National Heart and Lung Institute, London, UK


Banning et al, 1995

Banning AP, Lewis NP, Northridge DB, Elbom JS, Henderson AH, Perfusion/ventilation mismatch during exercise in chronic heart failure: an investigation of circulatory determinants, Br Heart J 1995; 74: p.27-33.

Department of Cardiology, College of Medicine, University of Wales, Cardiff, UK.


Clark et al, 1995

Clark AL, Chua TP, Coats AJ, Anatomical dead space, ventilatory pattern, and exercise capacity in chronic heart failure, Br Heart J 1995 Oct; 74(4): p. 377-380.

Department of Cardiac Medicine, National Heart and Lung Institute, London, UK.


Buller et al, 1990

Buller NP, Poole-Wilson PA, Mechanism of the increased ventilatory response to exercise in patients with chronic heart failure, Heart 1990; 63; p.281-283.

The National Heart and Lung Institute and National Heart Hospital, London, UK.


Elborn et al, 1990

Elborn JS, Riley M, Stanford CF, Nicholls DP, The effects of flosequinan on submaximal exercise in patients with chronic cardiac failure, Br J Clin Pharmacol. 1990 May; 29(5): p.519-524.

Royal Victoria Hospital, Belfast, Northern Ireland.


D’Alonzo et al, 1987

D’Alonzo GE, Gianotti LA, Pohil RL, Reagle RR, DuRee SL, Fuentes F, Dantzker DR, Comparison of progressive exercise performance of normal subjects and patients with primary pulmonary hypertension, Chest 1987 Jul; 92(1): p.57-62.

Divisions of Pulmonary Medicine and Cardiology, Department of Internal Medicine, University of Texas Medical School, and Hermann Hospital, Houston, USA.


Travers et al, 2008

Travers J, Dudgeon DJ, Amjadi K, McBride I, Dillon K, Laveneziana P, Ofir D, Webb KA, O’Donnell DE, Mechanisms of exertional dyspnea in patients with cancer, J Appl Physiol 2008 Jan; 104(1): p.57-66.

Respiratory Investigation Unit, Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen’s University, Kingston, Ontario, Canada.


Bottini et al, 2003

Bottini P, Dottorini ML, M. Cordoni MC, Casucci G, Tantucci C, Sleep-disordered breathing in nonobese diabetic subjects with autonomic neuropathy, Eur Respir J 2003; 22: p. 654–660.

Dept of Internal Medicine and Endocrine-Metabolic Sciences, University of Perugia, Perugia, Italy


Tantucci et al, 2001

Tantucci C, Bottini P, Fiorani C, Dottorini ML, Santeusanio F, Provinciali L, Sorbini CA, Casucci G, Cerebrovascular reactivity and hypercapnic respiratory drive in diabetic autonomic neuropathy, J Appl Physiol 2001, 90: p. 889–896.

Clinica di 1Semeiotica e Metodologia Medica and Neurologia e Neuroriabilitazione, University of Ancona, and Dipartimento di Medicina Interna e Scienze Endocrino-Metaboliche, University of Perugia, Italy.


Mancini et al, 1999

Mancini M, Filippelli M, Seghieri G, Iandelli I, Innocenti F, Duranti R, Scano G, Respiratory Muscle Function and Hypoxic Ventilatory Control in Patients With Type I Diabetes, Chest 1999; 115; p.1553-1562.


Tantucci et al, 1997

Tantucci C, Scionti L, Bottini P, Dottorini ML, Puxeddu E, Casucci G, Sorbini CA, Influence of autonomic neuropathy of different severities on the hypercapnic drive to breathing in diabetic patients, Chest. 1997 Jul; 112(1): p. 145-153.

Clinica di Semeiotica e Metodologia Medica, University of Ancona, Italy.


Tantucci et al, 1996

Tantucci C, Bottini P, Dottorini ML, Puxeddu E, Casucci G, Scionti L, Sorbini CA, Ventilatory response to exercise in diabetic subjects with autonomic neuropathy, J Appl Physiol 1996, 81(5): p.1978–1986.

Clinica di Semeiotica Metodologia Medica, University of Ancona, Ospedale Regionale Torrette, Ancona 60020; and Istituto di Medicina Interna e Scienze Endocrine e Metaboliche, University of Perugia, Perugia 06100, Italy.


Chalupa et al, 2004

Chalupa DC, Morrow PE, Oberdörster G, Utell MJ, Frampton MW, Ultrafine particle deposition in subjects with asthma, Environmental Health Perspectives 2004 Jun; 112(8): p.879-882.

Department of Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA.


Johnson et al, 1995

Johnson BD, Scanlon PD, Beck KC, Regulation of ventilatory capacity during exercise in asthmatics, J Appl Physiol. 1995 Sep; 79(3): p. 892-901.

Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA


Bowler et al, 1998

Bowler SD, Green A, Mitchell CA, Buteyko breathing techniques in asthma: a blinded randomized controlled trial, Med J of Australia 1998; 169: p. 575-578.

Mater Adult Hospital, South Brisbane, QLD, Australia.


Kassabian et al, 1982

Kassabian J, Miller KD, Lavietes MH, Respiratory center output and ventilatory timing in patients with acute airway (asthma) and alveolar (pneumonia) disease, Chest 1982 May; 81(5): p.536-543.

Pulmonary Division, Department of Medicine, College of Medicine and Dentistry of New Jersey, New Jersey hfedical School, College Ho ital, Newark, USA


McFadden & Lyons, 1968

McFadden ER & Lyons HA, Arterial-blood gases in asthma, The New Engl J of Med 1968 May 9, 278 (19): 1027-1032.


Palange et al, 2001

Palange P, Valli G, Onorati P, Antonucci R, Paoletti P, Rosato A, Manfredi F, Serra P, Effect of heliox on lung dynamic hyperinflation, dyspnea, and exercise endurance capacity in COPD patients, J Appl Physiol. 2004 Nov; 97(5): p.1637-1642.

Dipartimento di Medicina Clinica, Servizio di Fisiopatologia Respiratoria, Università La Sapienza, v. le Università 37, 00185 Rome, Italy.


Sinderby et al, 2001

Sinderby C, Spahija J, Beck J, Kaminski D, Yan S, Comtois N, Sliwinski P, Diaphragm activation during exercise in chronic obstructive pulmonary disease, Am J Respir Crit Care Med 2001 Jun; 163(7): 1637-1641.

Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, Department of Medicine, and Ste Justine Research Center, Ste Justine Hospital, Montreal, Quebec, Canada.


Stulbarg et al, 2001

Stulbarg MS, Winn WR, Kellett LE, Bilateral Carotid Body Resection for the Relief of Dyspnea in Severe Chronic Obstructive Pulmonary Disease, Chest 1989; 95 (5): p.1123-1128.

Pulmonary Division, Department of Medicine, University of California, San Francisco; and Kaweah Delta District Hospital, Visalia, California, USA


Radwan et al, 2001

Radwan L, Maszczyk Z, Koziorowski A, Koziej M, Cieslicki J, Sliwinski P, Zielinski J, Control of breathing in obstructive sleep apnea and in patients with the overlap syndrome, Eur Respir J. 1995 Apr; 8(4): p.542-545.

Lung Function Laboratory, Institute of Tuberculosis and Lung Diseases, Warszawa, Poland


Epstein et al, 1998

Epstein SK, Zilberberg MD; Facoby C, Ciubotaru RL, Kaplan LM, Response to symptom-limited exercise in patients with the hepatopulmonary syndrome, Chest 1998; 114; p. 736-741.

Department of Medicine, Tupper Research Institute, New England Medical Center, Tufts University School of Medicine, Boston, MA 02166, USA


Kahaly, 1998

Kahaly GJ, Nieswandt J, Wagner S, Schlegel J, Mohr-Kahaly S, Hommel G, Ineffective cardiorespiratory function in hyperthyroidism, J Clin Endocrinol Metab 1998 Nov; 83(11): p. 4075-4078.


Fauroux et al, 2006

Fauroux B, Nicot F, Boelle PY, Boulé M, Clément A, Lofaso F, Bonora M, Mechanical limitation during CO2 rebreathing in young patients with cystic fibrosis, Respir Physiol Neurobiol. 2006 Oct 27;153(3):217-25. Epub 2005 Dec 27.


Browning et al, 1990

Browning IB, D’Alonzo GE, Tobin MJ, Importance of respiratory rate as an indicator of respiratory dysfunction in patients with cystic fibrosis, Chest. 1990 Jun;97(6):1317-21.


Ward et al, 1999

Ward SA, Tomezsko JL, Holsclaw DS, Paolone AM, Energy expenditure and substrate utilization in adults with cystic fibrosis and diabetes mellitus, Am J Clin Nutr. 1999 May;69(5):913-9.


Dodd et al, 2006

Dodd JD, Barry SC, Barry RB, Gallagher CG, Skehan SJ, Masterson JB, Thin-section CT in patients with cystic fibrosis: correlation with peak exercise capacity and body mass index, Radiology. 2006 Jul;240(1):236-45.


McKone et al, 2005

McKone EF, Barry SC, Fitzgerald MX, Gallagher CG, Role of arterial hypoxemia and pulmonary mechanics in exercise limitation in adults with cystic fibrosis, J Appl Physiol. 2005 Sep;99(3):1012-8. Epub 2005 Apr 28.


Bell et al, 1996

Bell SC, Saunders MJ, Elborn JS, Shale DJ, Resting energy expenditure and oxygen cost of breathing in patients with cystic fibrosis, Thorax 1996 Feb; 51(2): 126-131.

Section of Respiratory Medicine, University of Wales College of Medicine, UK


Tepper et al, 1983

Tepper RS, Skatrud B, Dempsey JA, Ventilation and oxygenation changes during sleep in cystic fibrosis, Chest 1983; 84; p. 388-393.


Esquivel et al, 1991

Esquivel E, Chaussain M, Plouin P, Ponsot G, Arthuis M, Physical exercise and voluntary hyperventilation in childhood absence epilepsy, Electroencephalogr Clin Neurophysiol 1991 Aug; 79(2): p. 127-132.


Han et al, 1997

Han JN, Stegen K, Simkens K, Cauberghs M, Schepers R, Van den Bergh O, Clément J, Van de Woestijne KP, Unsteadiness of breathing in patients with hyperventilation syndrome and anxiety disorders, Eur Respir J 1997; 10: p. 167–176.

Service de Neuropédiatrie, Hôpital St. Vincent de Paul, Paris, France


Pain et al, 1991

Pain MC, Biddle N, Tiller JW, Panic disorder, the ventilatory response to carbon dioxide and respiratory variables, Psychosom Med 1988 Sep-Oct; 50(5): p. 541-548.

Department of Thoracic Medicine, Royal Melbourne Hospital, Parkville, Victoria, Australia.


MacKinnon et al, 1991

MacKinnon DF, Craighead B, Hoehn-Saric R, Carbon dioxide provocation of anxiety and respiratory response in bipolar disorder, J Affect Disord 2007 Apr; 99(1-3): p.45-49.

Department of Psychiatry and Behavioral Sciences, Johns Hopkins University, Baltimore, MD, USA


Clague et al, 1994

Clague JE, Carter J, Coakley J, Edwards RH, Calverley PM, Respiratory effort perception at rest and during carbon dioxide rebreathing in patients with dystrophia myotonica, Thorax 1994 Mar; 49(3): p.240-244.

Aintree Chest Centre, Fazakerley Hospital, Liverpool, UK