The lungs start to feel as if they are burning, and the signals the body receives from the brain when CO2 levels are too high include strong, painful, and involuntary contractions or spasms of the diaphragm and the muscles in between the ribs. At some point, the spasms become so frequent, intense and unbearable that continued holding of the breath is nearly impossible.When a person is immersed in water, physiological changes due to the mammalian diving reflex enable somewhat longer tolerance of apnea even in untrained persons as breathing isnt possible underwater. Tolerance can in addition be trained. The ancient technique of free-diving requires breath-holding, and world-class free-divers can hold their breath underwater up to depths of 214 metres (702 ft) and for more than four minutes. Apneists, in this context, are people who can hold their breath for a long time. Hyperventilation
Voluntary hyperventilation before beginning voluntary apnea is commonly believed to allow the person involved to safely hold their breath for a longer period. In reality, it will give the impression that one does not need to breathe, while the body is actually experiencing a blood-oxygen level that would normally, and indirectly, invoke a strong dyspnea and eventually involuntary breathing. Some have incorrectly attributed the effect of hyperventilation to increased oxygen in the blood, not realizing that it is actually due to a decrease in CO2 in the blood and lungs.
DTaP-IPV/Hib vaccine is a 5-in-1 combination vaccine that protects against diphtheria, tetanus, whooping cough, polio, and Haemophilus influenzae type B.Its generic name is diphtheria and tetanus toxoids and acellular pertussis adsorbed, inactivated poliovirus and haemophilus B conjugate vaccine, and it is also known as DTaP-IPV-Hib. Uses
DTaP-IPV/Hib vaccine is administered to young children to immunise against diphtheria, tetanus, pertussis, poliomyelitis, and diseases caused by Haemophilus influenzae type B.

Formulations
A branded formulation marketed in the United States is Pentacel, manufactured by Sanofi Pasteur.Pentacel is known in the UK and Canada as Pediacel.An equivalent vaccine marketed in the UK and Canada by GlaxoSmithKline is Infanrix IPV + Hib. This is a two-part vaccine. The DTaP-IPV component is supplied as a sterile liquid, which is used to reconstitute lyophilized (freeze-dried) Hib vaccine. Pentaxim is a liquid formulation marketed by Sanofi Pasteur. Availability
It is only licensed for young children. In the US the FDA have approved the vaccine for children from age 6 weeks up to age 5 years. It was used in the UK until 2017, following which a 6-in-1 vaccine became available containing the additional protection against Hepatitis B. == References ==